Frame Pump

[Mark Cleary]

I don't like CO2 no reliable as a pump. Skip the mini pumps with one exception and tell me the best pump. I read the reviews and a Topeak Road Morph seems to be a clear winner. Not a mini pump but not a full size frame pump. Then I read a ZEfal seems to be the best but was outdone by the Topeak.

What are the options you might suggest and my criteria is easy. Money is not a problem if the pump does what I want it to do. I want the easiest and least amount of muscle work to get the tire up to say 90-100 psi. I don't expect and floor pumb but they too require a few strokes. My good floor pump and give a 25mm 700c road tire up to about 95psi in about 35 strokes with new tube.

Also if I get the pump that fits on the pump stop on my habanero frame do you just measure the distance and how much error do you get to keep it tight?
Deacon Mark

[Roger Merriman]

I did have one, which I used for traveling I disliked it though it’s quite
a few years back so can’t remember why!

Roger Merriman

[Frank Krygowski]

I used Zefal HP for years, and still have them on some bikes. When the
Zefal HPX came out, I bought those. They've been almost perfectly
reliable. The only failures have been the little plastic "wings" the
snug it in place against the frame tubes. Replacements exist, but are
hard to find.

Other pumps may be better, but not in ways that matter to me.

I remember a club ride where multiple CO2 systems failed, and the flat
was finally fixed using my Zefal HPX.

--
- Frank Krygowski

[AMuzi]

Those are both excellent choices.

Vendors may have different measuring systems. Here, we ask
'How much distance must it span?', which would be peg to
seat tube in your case. As with spoke length terminology,
others ask tube length on centers and correct from there.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[Roger Merriman]

I never got on with C02 and now with tubeless (on the Gravel bikes new
wheels) which some sealants don’t like I believe. Thus far two rides one
puncture (some goo left on my shorts and tire) encouraging thus far ie
sealed in under a second some pressure lost but since it was its test run
I’d bee advised will loose pressure slowly for a while.

I have bought a new mini pump so I don’t end up unscrewing the valve which
would be annoying!

Roger Merriman

[Mark Cleary]

Frank would like to know your experience with it on getting the tire up to desired PSI? Can you get to say 90 PSI with not too many strokes or do happen to know? I know mini pumps regardless can work but after getting to about 60 PSI you could pump 100 more times just get to 80-95. I have no interest in Co2 I carry a cartridge and chuck but unless I am in some hurry best to use a pump. CO2 to me is failure waiting to happen with any slip up.
Deacon Mark

[AMuzi]

The Zéfal HPX and Topeak are relatively long and of
relatively small diameter compared to other pumps which
makes them significantly easier to use than, say, a classic
Silca or a mini-pump.

[Lou Holtman]

My Zefal HPX from the past mounted under the top tube rattled like hell. Why does everybody think that CO2 is a failure to happen? You screw the cartridge in, you press the chuck onto the presta valve like any other chuck and you open/close/open/close the valve of the chuck. 90-100 psi? Good luck with your Zefal. Best frame pump I had and still have somewhere is the Topeak Road Morph by far and there is a reason for that. It is a mini floor pump. Good luck.

Lou

[ritzann...@gmail.com]

https://www.amazon.com/Blackburn-Frame-Pump/dp/B07C9RTC2G
Blackburn Frame Pump. Used it for about 35 years now I think. Usually on group rides I use my pump to get the fixed tire inflated. Never other people's pumps. If you forget to air up your tires at home before a ride. And drive to the start location and discover you need more air. It will easily top your tires up to 100 or 120 psi. You do have to pump it to reach pressure. But what is another 15 seconds when you've already been stopped for 5 minutes due to the flat.

[John B.]

I would also ask, "how often do you have flats?". I carried a pump for
years and finally realized that I very seldom had flats and went to
the CO2 cartridges, two in the seat bag, and still had very few flats
(:-)

--
Cheers,

John B.

[ritzann...@gmail.com]

Six flats on Paris Brest Paris in 2007. 765 total miles. One flat every 127 miles. My Blackburn frame pump got a lot of use during those three days and nights.

[Frank Krygowski]

I don't know for sure because I seldom take precise pressure measurements, but I usually count strokes as
I pump, sort of assuming it's about 1 psi per stroke. For me, ~100 strokes gets close enough to ~100 psi.
I've got a mini pump on my folding bike. IIRC it requires at least 250 strokes to inflate a flat tire. It doesn't
require much force, but that's a lot of pumping. Fortunately I've rarely needed to use it.

> I have no interest in Co2 I carry a cartridge and chuck but unless I am in some hurry best to use a pump. CO2 to me is failure waiting to happen with any slip up.

I've seen that happen to others.

- Frank Krygowski

[Frank Krygowski]

On Sunday, August 21, 2022 at 6:17:16 PM UTC-4, lou.h...@gmail.com wrote:
>
> My Zefal HPX from the past mounted under the top tube rattled like hell.

Huh. I've never had that problem. In fact, I've never heard of that problem.

> Why does everybody think that CO2 is a failure to happen? You screw the cartridge in, you press the chuck onto the presta valve like any other chuck and you open/close/open/close the valve of the chuck.

Why do I think it's a failure waiting to happen? Because I've seen it happen multiple times. I've heard
about other instances.

>90-100 psi? Good luck with your Zefal.

It's never required luck for me. And I'm not unusually strong.

- Frank Krygowski

[John B.]

(:-) Well, I can comment on French roads but I have ridden for 30
years or more in Thailand, Singapore and Indonesia and as I said...
had very few flats (:-) In fact, from memory, the most flats I ever
had on one ride was with a pair of brand, new, superduper, Gatorskin
tires. Two flats in about a half a mile. And, I'll grant that was a
disaster. Sitting on the side of the road with the rain pouring down
and I discovered I was out of tire patches (:-(
--
Cheers,

John B.

[Lou Holtman]

On Monday, August 22, 2022 at 3:59:15 AM UTC+2, frkr...@gmail.com wrote:
> On Sunday, August 21, 2022 at 6:17:16 PM UTC-4, lou.h...@gmail.com wrote:
> >
> > My Zefal HPX from the past mounted under the top tube rattled like hell.
> Huh. I've never had that problem. In fact, I've never heard of that problem.

I said my HPX. Had to stuff a piece of rubber in the space between the handle and the barrel that got lost every time I used the pump. Never heard of it? Well no you have.

> > Why does everybody think that CO2 is a failure to happen? You screw the cartridge in, you press the chuck onto the presta valve like any other chuck and you open/close/open/close the valve of the chuck.
> Why do I think it's a failure waiting to happen? Because I've seen it happen multiple times. I've heard
> about other instances.

Pff, I have seen a lot of mini and frame pumps fail. Like any pump you have to learn the technique how to use them.

> >90-100 psi? Good luck with your Zefal.
> It's never required luck for me. And I'm not unusually strong.

100 psi or almost 7 bar? Don't you have 35 mm wide tires? You never need to pump up those tires to 100 psi. In practice people stop pumping at the moment they think 'this is good enough' and most of the times this is at 5-5.5 bar. Compared to mini pumps a frame pump makes it faster not easier. Physics.

Bottom line is that you can run out of catridges in case of multiple flats during a ride. But the upside is that you can inflate a tube much faster and to a higher pressure much, much easier than with a pump. If it gives you piece of mind to carry a (frame) pump that is all good, but CO2 inflator is a failure waiting to happen is nonsense.

Lou

[AMuzi]

I'm not arguing for or against CO2 or HPX. Both are good
products.

That said, your pump was the wrong length for that frame.

[Lou Holtman]

Possible but it had a range IIRC and I am sure it was within that range but water under the bridge now. It rattled and damaged the paint but is was a reasonable good pump. I found the Topeak Road Morph better to achieve higher pressures though. Just opposing to the 'CO2 inflator is a failure waiting to happen' nonsense.

Lou

[Frank Krygowski]

On 8/22/2022 4:30 AM, Lou Holtman wrote:
> On Monday, August 22, 2022 at 3:59:15 AM UTC+2, frkr...@gmail.com wrote:
>> On Sunday, August 21, 2022 at 6:17:16 PM UTC-4, lou.h...@gmail.com wrote:
>>>
>>> My Zefal HPX from the past mounted under the top tube rattled like hell.
>> Huh. I've never had that problem. In fact, I've never heard of that problem.
>
> I said my HPX. Had to stuff a piece of rubber in the space between the handle and the barrel that got lost every time I used the pump. Never heard of it? Well no you have.

Well, I'm sorry you had that problem. You're still the only person I've
heard of, but maybe others just didn't voice their complaints.

And I'm sorry you couldn't come up with a solution that didn't get lost
every time. Perhaps you should have posted here, as Tom does with his
many problems.

>
>>> 90-100 psi? Good luck with your Zefal.
>> It's never required luck for me. And I'm not unusually strong.
>
> 100 psi or almost 7 bar? Don't you have 35 mm wide tires? You never need to pump up those tires to 100 psi.

I've had Zefal HP or Zefal HPX pumps for a long, long time, way back
into the days I used 25mm tires. Most of the time my favorite size was
28, and that's still on my touring bike. Three other bikes now have
32mm, including the tandem. Folding bikes and mountain bikes are wider,
and get lower different pressure usually from the floor pump.

> In practice people stop pumping at the moment they think 'this is good enough' and most of the times this is at 5-5.5 bar. Compared to mini pumps a frame pump makes it faster not easier. Physics.

Whoa! Physics! Impressive! ;-)

> Bottom line is that you can run out of catridges in case of multiple flats during a ride. But the upside is that you can inflate a tube much faster and to a higher pressure much, much easier than with a pump. If it gives you piece of mind to carry a (frame) pump that is all good, but CO2 inflator is a failure waiting to happen is nonsense.

OK, I'll tell the guys whose CO2 inflators failed that you said that.


--
- Frank Krygowski

[Tom Kunich]

You and I are in complete agreement. Though I will add that someone or other made a minipump that clamped into a plastic holder attached under the water bottle holder. It had a reasonably easy use and only 100 strokes to bring a tire to pressure. It didn't rattle and it had a small extension hose that screwed on both ends making it quite easy to use. But CO2 takes up far less room now that we have such good tires that rarely have flats.

[Frank Krygowski]

I'm _very_ curious about a mini-pump that required only 100 strokes, if
you mean 100 strokes from zero to ~100 psi. What specific pump was that?
250 to 300 strokes seem to be more common.

We could work on this as a physics problem!


--
- Frank Krygowski

[funkma...@hotmail.com]

On Monday, August 22, 2022 at 4:30:05 AM UTC-4, lou.h...@gmail.com wrote:
> On Monday, August 22, 2022 at 3:59:15 AM UTC+2, frkr...@gmail.com wrote:
> > On Sunday, August 21, 2022 at 6:17:16 PM UTC-4, lou.h...@gmail.com wrote:
> > >
> > > My Zefal HPX from the past mounted under the top tube rattled like hell.
> > Huh. I've never had that problem. In fact, I've never heard of that problem.
> I said my HPX. Had to stuff a piece of rubber in the space between the handle and the barrel that got lost every time I used the pump. Never heard of it? Well no you have.

I couldn't get my Silca pump to stay in the frame ( I ride a 56) . I ended up using a velcro strap to keep it in place. I switched to the HPX and the problem went away. The downside? The HPX didn't inflate as quickly or reliably. Pick yer poison. I don't use a frame pump at all these days.

> > > Why does everybody think that CO2 is a failure to happen? You screw the cartridge in, you press the chuck onto the presta valve like any other chuck and you open/close/open/close the valve of the chuck.
> > Why do I think it's a failure waiting to happen? Because I've seen it happen multiple times. I've heard
> > about other instances.
> Pff, I have seen a lot of mini and frame pumps fail. Like any pump you have to learn the technique how to use them.
> > >90-100 psi? Good luck with your Zefal.
> > It's never required luck for me. And I'm not unusually strong.
> 100 psi or almost 7 bar? Don't you have 35 mm wide tires? You never need to pump up those tires to 100 psi. In practice people stop pumping at the moment they think 'this is good enough' and most of the times this is at 5-5.5 bar. Compared to mini pumps a frame pump makes it faster not easier. Physics.
>
> Bottom line is that you can run out of catridges in case of multiple flats during a ride. But the upside is that you can inflate a tube much faster and to a higher pressure much, much easier than with a pump. If it gives you piece of mind to carry a (frame) pump that is all good, but CO2 inflator is a failure waiting to happen is nonsense.

I rely pretty heavily on CO2 inflators, but have had plenty of failures. When going off-road I generally carry a mini pump as well, just to top off in case the seal doesn't hold rather than breaking into a new cartridge (running tubeless) and in case the inflator failure happens.

I wouldn't go so far as to say CO2 is a "failure waiting to happen", but it's happened often enough for me to carry a minipump just in case. It seems the major cause of failure is the o-ring seal where the cartridge screws in. I'm pretty convinced these are generic rubber that can't handle the ultra low temperature of the CO2 discharge. I've had much better luck with them since I now wait for the inflator to warm back up to the point that it just feels colder than the surrounding air before I unscrew the cartridge. Than said, I did have one knob type (Pro Bike Tool) that literally came apart in my hand after I opened the valve, and a lever type (Genuine Innovations) that just refused to open (and no, the locking mechanism was not set to the lock position).

I've been using the Portland Design Works "Shiny Object" for a couple of years (with many flats) now with no problems.


>
> Lou

[Lou Holtman]

I use this one,
https://www.mantel.com/lezyne-control-drive-co2-co2-pomp
never failed on me. After inflating I leave the cartridge on until I get home and replace it. Screw the new cartridge halfway in so it doesn't cut the seal of the cartridge. I carry two cartridges and two tubes on a road bike and a phone. Never had to use the latter. You have to know that adiabatic expanding CO2 gets cold (science). In humid conditions it can freeze the valve stuck. In such or any conditions it is better to inflate with a couple of short bursts with a little time in between so the tube valve can warm up a bit. It is also wise not to unscrew the cartridge immediately after inflating. The cartridge can be frozen stuck to the rubber seal and when you unscrew gets torn a bit. Leave it on. With this simple rules failure is unlikely but the clumsy/technical challenged/stubborn people should stay away from CO2 inflator and stick to their mini/frame pumps and hope that the rubber seal is not rotten/worn or full of mud, the barrel not crooked, the piston lubed and they don't mind 100+ strokes to achieve a meager 5-5.5 bar. Frame/mini pumps don't fail, yeah right....as if they don't need some care which most of the times they don't get from the clumsy/technical challenged/stubborn people. YMMV.

Lou

[Tom Kunich]

The nice thing about that Lezyne is that it has a positive on and off. A lot of them have a button the fails after only a couple of uses.

[Lou Holtman]

People who are able to operate a faucet can operate this CO2 inflater.

Lou

[Mark Cleary]

Lou the problem is you have to make sure the tube is inside the tire correct. It fills so fast that it is possible to not have the tube seated correct and pop. You probably are not as clumsy as me. Also, once I have a flat tire on a very cold ride in the winter and I was not careful and hands froze and burned. I also have had the chuck not seated correct and then checking the tire for pressure I lose the air. For myself I just want to be sure I have endless air. I don't even carry a patch kit just a spare tube. I figure if I go down with another flat I will make the call. I suppose on a century if I was going to be way out I might be better to take 2 tube. Patching a tube I can do but not on the roadside.
Deacon Mark

[Roger Merriman]

Lou Holtman <lou.h...@gmail.com> wrote:
> On Monday, August 22, 2022 at 3:59:15 AM UTC+2, frkr...@gmail.com wrote:
>> On Sunday, August 21, 2022 at 6:17:16 PM UTC-4, lou.h...@gmail.com wrote:
>>>
>>> My Zefal HPX from the past mounted under the top tube rattled like hell.
>> Huh. I've never had that problem. In fact, I've never heard of that problem.
>
> I said my HPX. Had to stuff a piece of rubber in the space between the
> handle and the barrel that got lost every time I used the pump. Never
> heard of it? Well no you have.
>
>>> Why does everybody think that CO2 is a failure to happen? You screw the
>>> cartridge in, you press the chuck onto the presta valve like any other
>>> chuck and you open/close/open/close the valve of the chuck.
>> Why do I think it's a failure waiting to happen? Because I've seen it
>> happen multiple times. I've heard
>> about other instances.
>
> Pff, I have seen a lot of mini and frame pumps fail. Like any pump you
> have to learn the technique how to use them.
>
>>> 90-100 psi? Good luck with your Zefal.
>> It's never required luck for me. And I'm not unusually strong.
>
> 100 psi or almost 7 bar? Don't you have 35 mm wide tires? You never need
> to pump up those tires to 100 psi. In practice people stop pumping at the
> moment they think 'this is good enough' and most of the times this is at
> 5-5.5 bar. Compared to mini pumps a frame pump makes it faster not easier. Physics.

That high! Even on the gravel bike I only just reach 3bar/45psi

Seems to be some suggestions that CO2 isn’t good with tubeless or rather
the sealants.

>
> Bottom line is that you can run out of catridges in case of multiple
> flats during a ride. But the upside is that you can inflate a tube much
> faster and to a higher pressure much, much easier than with a pump. If it
> gives you piece of mind to carry a (frame) pump that is all good, but CO2
> inflator is a failure waiting to happen is nonsense.
>
> Lou
>
>

Roger Merriman

[ritzann...@gmail.com]

A Tommy pronouncement:

"now that we have such good tires that rarely have flats."

Ha Ha Ho Ho.

[ritzann...@gmail.com]

Deacon Mark wrote: "Patching a tube I can do but not on the roadside."

Carry Park Instant Patches. In addition to the extra tube or two. They are not permanent like real patches you do at home. But they stick good for about a week and then fall off. Long enough to get you home.

https://www.parktool.com/en-us/product/super-patch-kit-gp-2

[ritzann...@gmail.com]

That is contrary to what little I know about tubeless tires. Its little. You need the CO2 to quickly inflate the tubeless tire so it locks the tire bead into the rim. Whereas with a manual pump, you cannot get the quick burst of air to force the bead into its groove that keeps the tire on the rim. I've heard people use compressed air and air compressor tanks at home to seat a tubeless tire. Not possible with a regular tire pump. And thus some inventor made a manual normal tire pump that allows you to inflate a chamber on the pump so you can use it in burst mode for seating tubeless tires.

[Jeff Liebermann]

OK. I'll bite. I get to pick the pump from my collection:
<http://www.learnbydestroying.com/jeffl/pics/bicycles/misc/bicycle-pumps.jpg>
Measuring the volume of one stroke is easy. I fill the pump with
water and measure the volume (or weight) of the ejected water. That
takes care of all the volume of valves, cavities, hardware and
oddities inside the pump.

You get to pick the tube and tire sizes. If you have the actual
dimensions (ID or OD) available that would be handy.

Calculating the volume of the inflated tube is a bit awkward, but not
impossible. I could probably measure the volume using water
displacement, but I don't have every size tube and tire handy.

The math is ideal gas law:
<https://en.wikipedia.org/wiki/Ideal_gas_law>
PV=nRT where:
P=pressure, V=volume, n=number of moles,
R=gas constant, T=temperature
When adding more air N (molecules) and P (pressure) will increase. V
(volume) is constrained by the tire and does not increase. T
(temperature) will increase, but it's assumed that sufficient time or
coolant are available to bring the tire back to room temperature. This
video grinds through the calculations, except it's for deflation and
not inflation. Easy enough to change some signs.



--
Jeff Liebermann je...@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

[Frank Krygowski]

I've used only one instant patch. The flat happened in Stockholm -
interestingly, from broken glass on a multi-use path!

Anyway, I was shocked to find I'd forgotten to pack my usual patch kit.
I used one of the tiny patches that came with the mini-pump for my
folding bike, stored in its handle.

I was a bit surprised to find it worked. In fact, while I'm not sure, it
may still be on that tube many years later.

--
- Frank Krygowski

[Frank Krygowski]

OK: My mini pump is a Hurricane HP Air Scepter, 0.669" bore, 7.7"
stroke. That's 2.7 in^3 per stroke.

I just had a bad experience testing it on my 3 speed's rear tire. That's
had a very slow leak, as in several days to need air, so it needed
pumping anyway.

Tire OD is 1.19", and it's a nominal 27" tire. I'm guessing about 1.1
ID. Volume is area times circumference at the centroid of that area. So
(Pi * ID^2 / 4) * (27" - 1.19") * Pi gives 77.0 in^3 for the tires volume.

To begin, the pump needs to inflate the flat tube to zero pressure.
That's just volume to volume at the same pressure. 77 in^3 / 2.7 in^3
per stroke = 28 strokes.

To pressurize that air, if we ignore temperature effects, all we need is
P1*V1 = P2*V2. Condition 1 refers to atmospheric air into the pump.
Condition 2 is volume at high pressure - say 100 psi? But both must be
absolute pressure, so P1 = 14.7 psi and P2 = ~ 114.7 psi. (Extra
significant figures only for clarity.)

Pump intake volume = V1 = P2 * V2 / P1 = 114.7 * 77 / 14.7 = about 590 in^3

590 in^3/ 2.7 in^3 per stroke = 218 strokes...
plus 28 strokes to expand a flat tube to full size, so ~ 250 strokes.

...

So, the bad experience: I deflated the already soft tube (slow leak,
remember?) and began counting. As I hit 250 strokes I heard a hiss. The
leak suddenly transformed from slow to fast. I felt air rushing out of
the rim at the valve. I disconnected the pump and watched the tire go
dead flat.

I'll try again later, maybe with a different bike tire.


--
- Frank Krygowski

[Luns Tee]

On Monday, August 22, 2022 at 6:35:56 PM UTC-7, jeff.li...@gmail.com wrote:
> When adding more air N (molecules) and P (pressure) will increase. V
> (volume) is constrained by the tire and does not increase. T
> (temperature) will increase, but it's assumed that sufficient time or
> coolant are available to bring the tire back to room temperature.

I was astounded when I worked out the numbers for the temperature increase. IIRC, adiabatically (no heat lost) compressing air from 1atm at 20c to 100psi, the temperature increases to something like 245c! Subsequently cooling back to room temperature without changing volume would lose roughly half of the 100psi. We don't see anything near this magnitude, which indicates the cooling happens much faster than we're able to pump to 100psi. The air has relatively little thermal mass relative to the materials it's in contact with, and the flow especially through the narrow valve, puts it in close contact, so the compression does look much closer to being isothermal (constant temperature) than adiabatic.

-Luns

[Luns Tee]

I haven't had great experience with the instant patches and haven't restocked since using my last one maybe 20 years ago.

I think the effectiveness depends a lot on the particular inner tube being used and how good a match it is for the tire. A 700x 20-25 inner tube will be stretched out much more in a 25mm tire than in a 20mm tire,, and the tension from stretching can't be any good for the patch adhesive. The patch covering roughly half the perimeter of the tube means the tension is roughly twice what it would be in an unpatched section. Moreover, the pressure-sensitive non-vulcanized adhesive will creep in use when the tube is inflated, so the unstretched patch will eventually be matched to stretched tube rubber, and if such a patched tube is taken out of service, the adhesive is stressed just sitting there unused with the patch being all wrinkly from the tube trying to shrink under it.

For the same 25mm tire, a 700x25-32 tube would be much easier on the patches. The ones I've used are generally thicker rubber than the smaller diameter tubes I've used, negating the benefit a bit, but this isn't universal; the thickest tube I've used so far is a 20-25 I recently got from a not-so-well stocked LBS.

So, YMMV with the instant patches. Using the largest, thinnest tube that will fit (which is also the most likely to get pinched under the bead in installation) would give the best chances of success, but this is true for conventional glued patches too.

-Luns

[Luns Tee]

On Tuesday, August 23, 2022 at 9:49:53 AM UTC-7, Frank Krygowski wrote:
> OK: My mini pump is a Hurricane HP Air Scepter, 0.669" bore, 7.7"
> stroke. That's 2.7 in^3 per stroke.

This sounds like the same 17mm bore of the HPX, while the HPX would have a stroke something around 2x to 3x of 7.7" . So the roughly 100 strokes to 100psi of the HPX would translate to 200-300 strokes. The 250 strokes you arrived at for the mini pump is right in the middle of that, corresponding to a 20" stroke, which sounds pretty reasonable.

-Luns

[Luns Tee]

On Sunday, August 21, 2022 at 10:19:56 AM UTC-7, deaco...@gmail.com wrote:
> I don't like CO2 no reliable as a pump. Skip the mini pumps with one exception and tell me the best pump. I read the reviews and a Topeak Road Morph seems to be a clear winner. Not a mini pump but not a full size frame pump. Then I read a ZEfal seems to be the best but was outdone by the Topeak.
>
> What are the options you might suggest and my criteria is easy. Money is not a problem if the pump does what I want it to do. I want the easiest and least amount of muscle work to get the tire up to say 90-100 psi. I don't expect and floor pumb but they too require a few strokes. My good floor pump and give a 25mm 700c road tire up to about 95psi in about 35 strokes with new tube.

I have classic Silca Imperos on all my bikes, but if I were shopping for a pump today, I would probably go with an HPX. The Impero requires a bit more arm strength than is comfortable for me, not enough to make me deliberately replace my pumps, but enough I wouldn't get the same thing going fowards. The HPX has a smaller barrel (17mm instead of 19mm, for 20% less force), and the retention spring is in series and locked out instead of being in parallel and adding to the pumping force as the old Impero does. I don't know how retention works on the current Silca Impero, but I'm pretty sure the bore is the same as before.

I've heard good things about the Road Morph but don't have first-hand experience with one. I don't think you'd go wrong either way.

-Luns

[Jeff Liebermann]

On Tue, 23 Aug 2022 12:49:47 -0400, Frank Krygowski

Very nice. I worked out a different method, which required
calculating moles of air and determining which gas constant is
appropriate. Your method is much easier. Thanks.

I see a problem with the tire volume calculation. The cross section
of the tire is NOT a circle.
<https://www.sheldonbrown.com/tire-sizing.html>
"The cross-section of a tire's fabric is an arc of a circle -- only a
full circle with tubulars. The rim takes up the part of the circle
that is not represented by the tire...."

What's the tire size printed on the side of the tire? 27 x ??
Bead width and depth of the rim? Approximate a square to make it
easier.

Volume of a torus:
1/4 * Pi^2 * (a+b) * (b-a)^2
where b=outer radius of the torus and a=inner radius of torus
<https://keisan.casio.com/exec/system/1223388402>

Is your measured pump stroke length calculated from measuring the
difference in travel of the piston shaft from fully in to fully out?
That's different from measuring the length of the pump body and is why
I like using the water displacement method.

Incidentally, the force required to pump the last stroke to 100 psi
is:
100 psi / piston_area = 100 / ( Pi * (0.669/2)^2 )
= 100 / 0.112 = 285 lbs
One needs to be fairly strong to pump the last few stroke.

Gotta run. Back later tonite.

[funkma...@hotmail.com]

On Monday, August 22, 2022 at 9:35:56 PM UTC-4, jeff.li...@gmail.com wrote:
> On Mon, 22 Aug 2022 12:44:29 -0400, Frank Krygowski
> <frkr...@sbcglobal.net> wrote:
>
> Measuring the volume of one stroke is easy. I fill the pump with
> water and measure the volume (or weight) of the ejected water. That
> takes care of all the volume of valves, cavities, hardware and
> oddities inside the pump.

You didn't really do this, did you? My god, what did that pump ever do to you?!?!?

[Luns Tee]

On Tuesday, August 23, 2022 at 11:09:46 AM UTC-7, jeff.li...@gmail.com wrote:
> On Tue, 23 Aug 2022 12:49:47 -0400, Frank Krygowski

> Very nice. I worked out a different method, which required
> calculating moles of air and determining which gas constant is
> appropriate. Your method is much easier. Thanks.

Rather than moles, I like to use cc's at STP, and convert pressure to ATM. All the pump spec sheets I've seen that offer a number for displacement, do so in cc's. The volume of air that needs to be delivered is just the volume of the tire times the pressure in ATM. The pressure can be either absolute pressure or gauge pressure depending whether you're starting from a fully empty (flat) or filled but not pressurized tube.
Frank's method is basically the same thing, just with in^3 instead of cc's, and p2/p1 kept as a ratio instead of using units where p1=1.

> I see a problem with the tire volume calculation. The cross section
> of the tire is NOT a circle.

FIrst, consider a spherical cow....

> Incidentally, the force required to pump the last stroke to 100 psi
> is:
> 100 psi / piston_area = 100 / ( Pi * (0.669/2)^2 )

Umm... lbs/in^2 / in^2 = lbs/in^4 is I don't know what, but not a force.

> = 100 / 0.112 = 285 lbs

100psi * pi*(.669in/2)^2 = 35 lbs

-Lunsb

[Frank Krygowski]

I think that makes a negligible difference for this calculation.

> What's the tire size printed on the side of the tire? 27 x ??
> Bead width and depth of the rim? Approximate a square to make it
> easier.

That tire is 27 x 1 1/4".

> Volume of a torus:
> 1/4 * Pi^2 * (a+b) * (b-a)^2
> where b=outer radius of the torus and a=inner radius of torus
> <https://keisan.casio.com/exec/system/1223388402>
>
> Is your measured pump stroke length calculated from measuring the
> difference in travel of the piston shaft from fully in to fully out?

Yes.

> That's different from measuring the length of the pump body and is why
> I like using the water displacement method.

I didn't measure the length of the pump body. That's the stroke, by
laying the pump on my workbench and marking the minimum and maximum
extension used when pumping.

> Incidentally, the force required to pump the last stroke to 100 psi
> is:
> 100 psi / piston_area = 100 / ( Pi * (0.669/2)^2 )
> = 100 / 0.112 = 285 lbs
> One needs to be fairly strong to pump the last few stroke.

Nope. Force is pressure TIMES area. Units on your computation work out
to pounds/in^4. That's not right. Also, I get the pump area = 0.35
in^2, not 0.112 in^2.

100 lb/in^2 * 0.35 in^2 = 35 pounds. Much more reasonable!

BTW, if a person happens to have something like a HP48G calculator lying
around, it's very handy to save in the root directory a simple function
named something like AC, for Area of a Circle.

<< SQ 𝜋 * 4 / >>

Put the diameter in the stack, type AC and get the area.

:-)

--
- Frank Krygowski

[Roger Merriman]

Seems to be more aimed at, trailside punctures than set up. This said it
also seems to be myth or at least though can find it repeated, what I can’t
find is any solid proof ie any manufacturers or technical bods advice.

I’ve only had tubeless for two rides this far, have a mini pump than CO2
though push on rather than screw to avoid unscrewing the valve which the
pumps with hoses can do I found!

Which can get tedious…

Thus far the one and only puncture was sealed in very short order. but we
shall see how it goes I guess!

>
>>>
>>> Bottom line is that you can run out of catridges in case of multiple
>>> flats during a ride. But the upside is that you can inflate a tube much
>>> faster and to a higher pressure much, much easier than with a pump. If it
>>> gives you piece of mind to carry a (frame) pump that is all good, but CO2
>>> inflator is a failure waiting to happen is nonsense.
>>>
>>> Lou
>>>
>>>
>> Roger Merriman
>

Roger Merriman

[Jeff Liebermann]

On Tue, 23 Aug 2022 12:49:47 -0400, Frank Krygowski
<frkr...@sbcglobal.net> wrote:

>OK: My mini pump is a Hurricane HP Air Scepter, 0.669" bore, 7.7"
>stroke. That's 2.7 in^3 per stroke.

Is that really a mini-pump? 7.7" in seems like a rather long stroke
for a mini-pump. Note the stroke lengths in my collection below. Is
there a maximum length for something to be considered a mini-pump?

Crank Brothers
Power Pump Dual Piston Design
bore = ???? stroke = 2.7" force @100psi = ???

Schwinn
bore = 0.960" stroke = 4.8" force @100psi = 138 lbs

Topeak
bore = 0.89" stroke = 5.3" force @100psi = 161 lbs

Bike Gear
bore = 0.68" stroke = 4.3" force @100psi = 275 lbs

force = 100psi / ( Pi * radius^2 )

Drivel: Zoom meeting postponed so I'll be able to work on this today.

[Jeff Liebermann]

On Tue, 23 Aug 2022 11:58:23 -0700 (PDT), "funkma...@hotmail.com"
<funkma...@hotmail.com> wrote:

>On Monday, August 22, 2022 at 9:35:56 PM UTC-4, jeff.li...@gmail.com wrote:
>> On Mon, 22 Aug 2022 12:44:29 -0400, Frank Krygowski
>> <frkr...@sbcglobal.net> wrote:
>>
>> Measuring the volume of one stroke is easy. I fill the pump with
>> water and measure the volume (or weight) of the ejected water. That
>> takes care of all the volume of valves, cavities, hardware and
>> oddities inside the pump.

>You didn't really do this, did you?

Yes, but only to one old Topeak mini-pump. However, the calculated
and measured volumes were sufficiently close, that I think I can use
the measured volumes. Measuring the bore diameter was a bit of a
challenge because of the inside threads at the end of the pump body. I
had to use inside calipers and transfer the ID to my digital calipers.
Close enough methinks.

Incidentally, using fluid displacement has a real advantage with
multi-stage bicycle pumps and pumps like the Crank Brothers pump, that
has "High Pressure" and "High Volume" settings. Calculating the
volume would normally require disassembly and measurement while fluid
displacement method will work without requiring disassembly.

>My god, what did that pump ever do to you?!?!?

In order to get good results, one must first offer sacrifice before
the various gods of cycling, metrology, math, etc. There isn't much
damage done that can't be fixed by removing residual water with an air
hose and evaporating any remaining water in the sun.

[Jeff Liebermann]

On Tue, 23 Aug 2022 12:01:22 -0700 (PDT), Luns Tee <lu...@berkeley.edu>
wrote:

>On Tuesday, August 23, 2022 at 11:09:46 AM UTC-7, jeff.li...@gmail.com wrote:
>> On Tue, 23 Aug 2022 12:49:47 -0400, Frank Krygowski
>> Very nice. I worked out a different method, which required
>> calculating moles of air and determining which gas constant is
>> appropriate. Your method is much easier. Thanks.

>Rather than moles, I like to use cc's at STP, and convert pressure to ATM. All the pump spec sheets I've seen that offer a number for displacement, do so in cc's. The volume of air that needs to be delivered is just the volume of the tire times the pressure in ATM. The pressure can be either absolute pressure or gauge pressure depending whether you're starting from a fully empty (flat) or filled but not pressurized tube.
>Frank's method is basically the same thing, just with in^3 instead of cc's, and p2/p1 kept as a ratio instead of using units where p1=1.

That's a good way to do it. Thanks for the ideas.

>> I see a problem with the tire volume calculation. The cross section
>> of the tire is NOT a circle.
>
>FIrst, consider a spherical cow....

Yep.

>> Incidentally, the force required to pump the last stroke to 100 psi
>> is:
>> 100 psi / piston_area = 100 / ( Pi * (0.669/2)^2 )

>Umm... lbs/in^2 / in^2 = lbs/in^4 is I don't know what, but not a force.
>
>> = 100 / 0.112 = 285 lbs
>
>100psi * pi*(.669in/2)^2 = 35 lbs
>
>-Lunsb

Oops. I didn't check if the units worked so I divided when I should
have multiplied. I made the same mistake in a different posting,
which I'll try to correct in a few minutes. Thanks for the
correction.

[Jeff Liebermann]

On Tue, 23 Aug 2022 12:37:42 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>Crank Brothers
>Power Pump Dual Piston Design
> bore = ???? stroke = 2.7" force @100psi = ???
>
>Schwinn
> bore = 0.960" stroke = 4.8" force @100psi = 138 lbs
>
>Topeak
> bore = 0.89" stroke = 5.3" force @100psi = 161 lbs
>
>Bike Gear
> bore = 0.68" stroke = 4.3" force @100psi = 275 lbs
>
>force = 100psi / ( Pi * radius^2 )

The above is totally wrong. My mistake and my thanks to Luns Tee and
Frank for noticing the problem. The above should be:

Crank Brothers
Power Pump Dual Piston Design
bore = ???? stroke = 2.7" force @100psi = ???

Schwinn

bore = 0.960" stroke = 4.8" force @100psi = 72 lbs

Topeak
bore = 0.89" stroke = 5.3" force @100psi = 62 lbs

Bike Gear
bore = 0.68" stroke = 4.3" force @100psi = 36 lbs

force = 100psi * ( Pi * radius^2 )

[Jeff Liebermann]

On Tue, 23 Aug 2022 12:56:55 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>However, the calculated
>and measured volumes were sufficiently close, that I think I can use
>the measured volumes.

Oops (again). That should be:

However, the calculated and measured volumes were sufficiently close,

that I think I can use the calculated volumes.

[AMuzi]

It's not 285lb at 100psi, not even close.

At 18mm diameter, you get a roughly one sq inch area which
needs roughly 100lb to output 100lb/sq in, which experience
confirms.

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[Tom Kunich]

If you're using clincher tires on clincher rims you need more practice if you cannot tell if the tube is not pinched. You push the far side of the tire into the deepest part of the rim and then you push the close side over looking down to make sure that the tube isn't under the tire. If it is you can generally lift the tire a little which will cause the very partially inflated tube to pop under and into the tire inner side. By partially inflated, I generally open the filler and using only my breath inflate the tire slightly. If you have too much air in the tube it resists allowing the tire to be pushed on by HAND ONLY. This mainly why I stopped using tubeless tires. It took plastic covered steel levers to finally push the tire over the end of the tubeless rim. At your age I'm sure that you can roll the tire over the edge after making sure that the tire on both sides are shoved to the deepest part of the clincher rim.

With tubeless rims, there is a deep center well but still the tire bead is so tight that it is very difficult to mount and impossible to get a tube in there if you need to use one without pinching the tube 3 out of 4 tries. While some people here have pointed out that some tubeless tires are especially tight my experience is that they are all so tight that it makes little difference.

[Tom Kunich]

The heating due to a pressure increase is so slight because of the pumping speed that temperature increases due to pressure changes is indetectable.

[Tom Kunich]

The Park Tool insta--patches still work well. The Chinese copies do not.

[Jeff Liebermann]

Huh? If pumping speed were a factor in tire inflation heating, then
very rapidly inflating a tire using an air compressor or CO2 cartridge
should cause the tire to catch fire. That doesn't happen.

Methinks we can assume that inflating a tire will produce some heat.
Ideal gas law calcs demonstrate that. The generated heat can be
dissipated by either convection or radiation. We don't normally use a
fan to cool the pump or tire while inflating, so that leaves
radiation. What part of the pumping system will radiate most of the
heat? Aluminum pump, rubber pump hose, brass or plastic valve head,
rubber inner tube, rubber tire, aluminum rim, or stainless spokes?
After inflating a tire, which of these parts are still warm when
you're done? Extra credit if you have an IR camera or IR thermometer
data.

[Luns Tee]

On Tuesday, August 23, 2022 at 1:57:34 PM UTC-7, AMuzi wrote:
> At 18mm diameter, you get a roughly one sq inch area which
> needs roughly 100lb to output 100lb/sq in, which experience
> confirms.

18mm is about 0.4 square inches. 28mm, which is the diameter of the Silca Pista is roughly one (0.954) square inch.

So if you have a Pista with a damaged pressure gauge, you can do a poor man's calibration by just putting it on a bathroom scale, zeroing out the pump's mass, and comparing indicated weight in lbs with indiciated pressure on the gauge.

-Luns

[Frank Krygowski]

That reminds me of the old trick for measuring speed, back in the day of
"tick tick tick" mechanical cyclometers: For 700C or 27 inch wheels,
the number of ticks in five seconds is extremely close to your speed in
miles per hour.

Sometimes the numbers just work out fortuitously.


--
- Frank Krygowski

[Luns Tee]

On Tuesday, August 23, 2022 at 3:04:41 PM UTC-7, jeff.li...@gmail.com wrote:
> Huh? If pumping speed were a factor in tire inflation heating, then
> very rapidly inflating a tire using an air compressor or CO2 cartridge
> should cause the tire to catch fire. That doesn't happen.

Things do get warmer when compressing faster. However, in these examples, you're not just compressing air in the tire, you're also decompressing air in the compressor tank or CO2 in the cartridge (which largely comes from liquid CO2 boiling rather than room temperature gas expanding). Heating from compression is neglible relative to the cooling from these expansions, boiling being a more extreme expansion. I've had frost form on my valve stem when I've filled a tire from a CO2 cartridge. Conversely, the valve stem is perceptibly warmer from pumping a tire with either a floor pump or frame pump.

This is less apparent with bicycle pumps than it is with PCP airgun pumps which can get up to a few thousand PSI. Those pumps often include passive liquid trapped for more thermal mass to sink heat, and the directions also sometimes recommend breaking up continuous pumping to give the pump time to cool off. I think the higher pressure and somewhat higher volume of air delivered compared to a typical tire means there's an order of magnitude if not more heat that's generated in the pump than pumping a bike tire.

-Luns

[Frank Krygowski]

To tremendously reduce the probability of mistakes like yours, I taught
the technique shown here:
https://brownmath.com/bsci/convert.htm
If the units don't work out (as in your initial attempt) there's
something wrong. It's a signal to go back and find your error.

I insisted my students show units and their cancellation on every
problem. It really helps.

It even works with electrical problems, if you remember that
1 Volt = 1 Amp * 1 Ohm or 1 Watt = 1 Volt * 1 Amp, etc.


--
- Frank Krygowski

[AMuzi]

Thank you.
But my point holds that 1 sq in needs 100 lb to make 100
psi. Smaller diameter pumps need more strokes but less effort.

[ritzann...@gmail.com]

1 square inch needs 100 pounds to make 100 pounds per square inch. Gosh, Andy that seems a little too simple and straightforward.

[Jeff Liebermann]

On Tue, 23 Aug 2022 17:21:10 -0700 (PDT), Luns Tee <lu...@berkeley.edu>
wrote:

>On Tuesday, August 23, 2022 at 3:04:41 PM UTC-7, jeff.li...@gmail.com wrote:
>> Huh? If pumping speed were a factor in tire inflation heating, then
>> very rapidly inflating a tire using an air compressor or CO2 cartridge
>> should cause the tire to catch fire. That doesn't happen.
>
>Things do get warmer when compressing faster.

Oops. You're correct. That's my 3rd mistake for the day. Maybe I
should do something else for a while. Thanks (again) for the
correction.

If the rate at which heat is radiated from the pump, tube, tire and
wheel, is greater than the rate at which compression heats the air,
the tire will become hot. However, if the pump, tube, tire and wheel
can radiate the heat faster than compression can replace it, the tire
will remain fairly cool.

>However, in these examples, you're not just compressing air in the tire, you're also decompressing air in the compressor tank or CO2 in the cartridge (which largely comes from liquid CO2 boiling rather than room temperature gas expanding).

The cooling happens where the CO2 cartridge pressure drops radically
from about 880 psi to tire pressure of 40 to 120 psi.

"What's the pressure in a CO2 cartridge?"
<https://www.youtube.com/watch?v=rzZRDjRBALs> (12:37)

>Heating from compression is neglible relative to the cooling from these expansions, boiling being a more extreme expansion. I've had frost form on my valve stem when I've filled a tire from a CO2 cartridge. Conversely, the valve stem is perceptibly warmer from pumping a tire with either a floor pump or frame pump.

I probably shouldn't have mentioned CO2 because it complicates the
heat flow calculations (and guesses). I don't use CO2 cartridges and
have very little experience with them for inflating tires. At home, I
use an air compressor and have not noticed any heating in the valve,
tire, tube, or rim.

>This is less apparent with bicycle pumps than it is with PCP airgun pumps which can get up to a few thousand PSI. Those pumps often include passive liquid trapped for more thermal mass to sink heat, and the directions also sometimes recommend breaking up continuous pumping to give the pump time to cool off. I think the higher pressure and somewhat higher volume of air delivered compared to a typical tire means there's an order of magnitude if not more heat that's generated in the pump than pumping a bike tire.

With my air compressor, the temperature of the cylinder is
sufficiently high that I would get a nasty burn if I touched it while
operating. I don't know how much of this heat is caused by air
compression or piston friction. The pipe between the cylinder and the
tank has fins to help radiate the heat. However, the air delivered
from the tank is only slightly warmer than ambient thanks to the large
thermal mass of the tank cooling down the air before delivery and the
pressure drop causing a temperature drop.

I'm still trying to answer your question as to where the heat
generated from bicycle tire air inflation is going. Gas law says the
compressed air should be quite hot. Yet, if I bleed a little air out
of the valve from a tire I just inflated, it's fairly cool. Nothing
else in the system is even warm. So, where did the heat go? I should
put the tire in an insulated box and see if anything gets hot.

>-Luns

[Jeff Liebermann]

On Tue, 23 Aug 2022 20:22:00 -0400, Frank Krygowski
<frkr...@sbcglobal.net> wrote:

>To tremendously reduce the probability of mistakes like yours, I taught
>the technique shown here:
>https://brownmath.com/bsci/convert.htm
>If the units don't work out (as in your initial attempt) there's
>something wrong. It's a signal to go back and find your error.

Thanks. That's the first time I've seen that method. Usually, I
check if my units of measure and do a sanity check on the result. I
did neither when I made my mistake. I created the equation in a rush,
didn't check anything, and immediately prepared myself for a Zoom
meeting that never happened. Haste maketh waste. I'll look at the
article and see if I can steal something useful from it.

Normally, I do all my equation writing and math on a paper pad before
I commit to typing it into the computer. I can usually see problems
easier on paper than on the screen. I didn't do that this time. The
calculation of the force required to operate the pump at 100 psi was a
last minute afterthought. I went directly to the screen, with
predictable results.

>I insisted my students show units and their cancellation on every
>problem. It really helps.

I usually do that. However, sometimes the units are too long for the
equation to fit on one line. So, I scatter the units around the
equations with predictable results. This time, I included the psi,
but left out everything else.

>It even works with electrical problems, if you remember that
>1 Volt = 1 Amp * 1 Ohm or 1 Watt = 1 Volt * 1 Amp, etc.

Thanks again.

[AMuzi]

On 8/23/2022 9:58 PM, russell...@yahoo.com wrote:
> On Tuesday, August 23, 2022 at 7:24:04 PM UTC-5, AMuzi wrote:
>> On 8/23/2022 5:44 PM, Luns Tee wrote:
>>> On Tuesday, August 23, 2022 at 1:57:34 PM UTC-7, AMuzi wrote:
>>>> At 18mm diameter, you get a roughly one sq inch area which
>>>> needs roughly 100lb to output 100lb/sq in, which experience
>>>> confirms.
>>>
>>> 18mm is about 0.4 square inches. 28mm, which is the diameter of the Silca Pista is roughly one (0.954) square inch.
>>>
>>> So if you have a Pista with a damaged pressure gauge, you can do a poor man's calibration by just putting it on a bathroom scale, zeroing out the pump's mass, and comparing indicated weight in lbs with indiciated pressure on the gauge.
>>>
>>> -Luns
>>>
>> Thank you.
>> But my point holds that 1 sq in needs 100 lb to make 100
>> psi. Smaller diameter pumps need more strokes but less effort.

> 1 square inch needs 100 pounds to make 100 pounds per square inch. Gosh, Andy that seems a little too simple and straightforward.
>

Yes it is. But '235lb for 100psi' was out of scale for any
bicycle pump I've seen.

[Luns Tee]

I'll grant that these fall outside the original context of frame or mini pumps, but Topeak Joe Blow variants, Fat, Mountain X and Dualie would fit that description. With a 44.4mm barrel, these would take 240lb for 100psi. Mind you, their gauges only read up to 75psi or less and probably wouldn't appreciate 100psi, but I imagine these pumps should otherwise survive the experience.

-Luns

[Tom Kunich]

I'm trying to figure out how this is even a discussion the FACT that tires do not get even warm when inflated should have given anyone a clue that there is more here than compression of air in a confined space. The compression of the air in the pump bleeds heat off into the metal of the pump, the hose and then the decompression of the air in the innertube. The volume of the tube and the heat absorption of the rim and the tire leave no measurable increase in temperature.

Has anyone considered how air is getting compressed when the tube is at 100 psi and the pump is compressing atmospheric pressure to 100 psi. What is the actual volume of air being compressed as opposed to the means of losing heat? Good lord, one would expect actual facts to impinge upon theory.

[Tom Kunich]

My inflation of 28 mm tires according to Silca is approximately 96 PSI. I am not a track racer and infinitesimal gains means nothing.

The small minipump I had was when I was still running 23 mm tires and as I said, the double acting pump would fill the tire with about 100 strokes. But CO2 is lighter smaller and now with large expensive tires I simply don't get flats anymore so the CO2 is really nothing more than a backup. I'm paying about $50 apiece for Michelin Pro4;'s and they ride well with good traction and last at least 2,000 miles. Riding a variety of bikes means that tires don't get used very often so that extends their apparent life.

[Roger Merriman]

I’ve bought some new wheels for the gravel bike, partly as I suspected they
where fairly knackered, gravel riding particularly uk stuff ie everything
from single track to tarmac and to have them set up tubless thus far had
one puncture ie bit of gloop on tire tire had lost some pressure but as
this was its test ride so some pressure lost was expected.

I’m hoping that the gloop can mean I don’t end up having multiple punctures
on winter rides which can get tedious!

I have taken a spare inner tube on the first ride, I do have a pump but
realistically that’s last ditch efforts with the tubeless kit! I have the
rubber strips etc and tools in the bar ends.

Thus far so good but only done just over 100 miles so…

Roger Merriman

[Frank Krygowski]

On 8/23/2022 12:49 PM, Frank Krygowski wrote:
> On 8/22/2022 9:35 PM, Jeff Liebermann wrote:

>> When adding more air N (molecules) and P (pressure) will increase.  V
>> (volume) is constrained by the tire and does not increase.  T
>> (temperature) will increase, but it's assumed that sufficient time or

Bad news on the 2nd trial, or on the calculation.

I fixed the flat. (Oddly, it looked like a micro-bit of glass went into
the tube from the spoke side, not the pavement side. I must not have
cleaned things out properly after the last flat long ago.)

Then I attached the mini-pump and began counting. I stopped at 200
strokes, felt the tire with my thumb and thought "That feels like about
75 psi."

Well, my thumb needs re-calibrating, and so do my calculations. Pressure
gauges said only 55 psi.

I chose not to do a second trial. I'd already worked on brakes for a
friend's bike, plus fixed that flat, and I have a wiring project
awaiting me. I pumped to about 80 psi using my floor pump. But 200
strokes didn't come close to 100 psi.

Discussion is welcome.


--
- Frank Krygowski

[Lou Holtman]

That is what I’m telling every time a CO2 versus mini/frame pump discussion is going on. Al people stop pumping way sooner than 7 bar. 5.5 bar at the most. Nobody has a calibrated thumb.

Lou

[Roger Merriman]

My issue with C02 is it’s one shot nature of it, particularly since I do
head off into remote places way out of phone reception and so on, the
highest pressures are my Gravel bike at 45psi (track pump gauge) so
reasonably low.

Roger Merriman

[Frank Krygowski]

:-) Back in the late 1980s or early 1990s, our club sponsored a rather different cycling event, held mostly
within the large local metropark. It was a family-themed event, and besides a large menu of rides from which to choose, there was a large lunch spread, games for kids and adults, etc.

Two such games involved tires. One was a flat tire changing contest, for speed: How
fast can a person start with a flat front tire in his bike, remove it, take out the tube, replace the tube,
inflate it, reinstall the wheel. One friend of mine (reputed to be the best pro bike mechanic in the area)
won very easily. As I recall, his time was something near one minute.

The other contest was tire inflation. Riders started with their dire deflated, and used their pump (no gauge)
to pump to IIRC 100 psi. Contestants were free to stop, use their thumbs, pump fast or slow, and judge
the pressure any way they liked, We used a calibrated pressure gauge. The winner was extremely close -
as I recall, within two psi.

Of course, I don't know how well he might have repeated that. But at least on that day, his thumb seemed
well calibrated.

- Frank Krygowski

[pH]

On 2022-08-23, Luns Tee <lu...@berkeley.edu> wrote:
> On Sunday, August 21, 2022 at 10:19:56 AM UTC-7, deaco...@gmail.com wrote:
>> I don't like CO2 no reliable as a pump. Skip the mini pumps with one
>> exception and tell me the best pump. I read the reviews and a Topeak
>> Road Morph seems to be a clear winner. Not a mini pump but not a full
>> size frame pump. Then I read a ZEfal seems to be the best but was
>> outdone by the Topeak.
>>
>> What are the options you might suggest and my criteria is easy. Money is not a problem if the pump does what I want it to do. I want the easiest and least amount of muscle work to get the tire up to say 90-100 psi. I don't expect and floor pumb but they too require a few strokes. My good floor pump and give a 25mm 700c road tire up to about 95psi in about 35 strokes with new tube.
>
> I have classic Silca Imperos on all my bikes, but if I were shopping for a pump today, I would probably go with an HPX. The Impero requires a bit more arm strength than is comfortable for me, not enough to make me deliberately replace my pumps, but enough I wouldn't get the same thing going fowards. The HPX has a smaller barrel (17mm instead of 19mm, for 20% less force), and the retention spring is in series and locked out instead of being in parallel and adding to the pumping force as the old Impero does. I don't know how retention works on the current Silca Impero, but I'm pretty sure the bore is the same as before.
>
> I've heard good things about the Road Morph but don't have first-hand experience with one. I don't think you'd go wrong either way.
>
> -Luns


Zefal HPX all around, here. I guess that's three of 'em.

pH in Aptos

[funkma...@hotmail.com]

On Wednesday, August 24, 2022 at 2:02:12 AM UTC-4, jeff.li...@gmail.com wrote:
> On Tue, 23 Aug 2022 17:21:10 -0700 (PDT), Luns Tee <lu...@berkeley.edu>
> wrote:
> >On Tuesday, August 23, 2022 at 3:04:41 PM UTC-7, jeff.li...@gmail.com wrote:
> >> Huh? If pumping speed were a factor in tire inflation heating, then
> >> very rapidly inflating a tire using an air compressor or CO2 cartridge
> >> should cause the tire to catch fire. That doesn't happen.
> >
> >Things do get warmer when compressing faster.
> Oops. You're correct. That's my 3rd mistake for the day. Maybe I
> should do something else for a while. Thanks (again) for the
> correction.

Face it Jeff, you're getting old.

[Luns Tee]

On Tuesday, August 23, 2022 at 11:02:12 PM UTC-7, jeff.li...@gmail.com wrote:
> On Tue, 23 Aug 2022 17:21:10 -0700 (PDT), Luns Tee <lu...@berkeley.edu>
> wrote:
> If the rate at which heat is radiated from the pump, tube, tire and
> wheel, is greater than the rate at which compression heats the air,
> the tire will become hot. However, if the pump, tube, tire and wheel
> can radiate the heat faster than compression can replace it, the tire
> will remain fairly cool.

I would say dissipate rather than radiate, but that aside you've pretty much summed it up; the heat produced by compression gets absorbed/dispersed quickly enough to not see significant temperatures. It's not just a matter of the rate of compression, but also of duration. You'll see more of an effect if you pump up several tires in quick succession.

> With my air compressor, the temperature of the cylinder is
> sufficiently high that I would get a nasty burn if I touched it while
> operating. I don't know how much of this heat is caused by air
> compression or piston friction. The pipe between the cylinder and the
> tank has fins to help radiate the heat. However, the air delivered
> from the tank is only slightly warmer than ambient thanks to the large
> thermal mass of the tank cooling down the air before delivery and the
> pressure drop causing a temperature drop.

I don't know what the typical valving arrangement is like with a compressor, but in principle if you could disable the checkvalve(s) between the cylinder and pressurized tank and run the compressor with the piston always at tank pressure (doing no net compression), that would let you see the effect of friction alone. The friction will be higher than it is normally since the pressure is no longer cycling between atmospheric and tank pressure, but I imagine it'll be nowhere near as hot as when compressing air normally.

> I'm still trying to answer your question as to where the heat
> generated from bicycle tire air inflation is going.

The heat will be delivered to the barrel of the pump, mostly at the bottom, and through wherever the air goes after that. The top of barrel doesn't see much heat since it only sees air that's been minimally compressed, while the bottom sees the highest pressures. Air flowing through the checkvalve, hose and tire valve, will be in close contact with those passages and lose much of its heat to those surfaces. Whatever is left after the tire valve diffuses quickly in the tire chamber and heats up the inside of the tire pretty uniformly across the entire tire (e.g. no great concentration of air/rubber heat transfer near the valve.

What's happening inside the tire can be thought of in two different ways, but both are (must be) equivalent. The air that's initially in the tire to begin with is at low pressure. As you add more air into the tire, you can imagine the original volume of air getting pushed back into a smaller and smaller volume away from the valve as the pressure increases (basically, just imagine each half of the tire from valve to opposing point as being a curved pump chamber). As this compression happens, the initial air increases in temperature but losing that heat to the tire casing. The other interpretation is that the air that's originally there, stays throughout the tire as it originally was, minding its own business. As new air comes in, it slips past existing air molecules, diffusing throughout the volume (think of partial pressures of a mixture of different gases, except the different gases are just of air, old and new). Heat of the higher temperature new air gets mixed into the cooler old air. Either way, heat in the tire does get to the tire casing, but it won't be concentrated at the valve.

For perspective, keep in mind that this temperature rise from compression is what Diesel engines rely on for ignition. Diesel engines typically have a compression ratio somewhere around 20:1. If that compression is done isothermally, it only gets to around 300psi - higher than we use in bicycle tires, but not astronomically so. In fact, the work done (per mole of gas), is actually less than double what it is getting to 100psi, and that work done is exactly the heat produced: the internal energy of the gas is the same

>Gas law says the
> compressed air should be quite hot. Yet, if I bleed a little air out
> of the valve from a tire I just inflated, it's fairly cool. Nothing
> else in the system is even warm. So, where did the heat go? I should
> put the tire in an insulated box and see if anything gets hot.

The air you bleed out is cool because it expands as it comes out. The temperature drops as it expands just as it increased while compressing. If you only bleed a little bit of air, that's only a little bit of cooling happening. If you take a fully inflated tire that's sat long enough to dissipate all heat from pumping and then let out all the air at the valve, the valve does feel noticably cooler.

-Luns

[Luns Tee]

On Wednesday, August 24, 2022 at 6:15:30 PM UTC-7, frkr...@gmail.com wrote:
> The other contest was tire inflation. Riders started with their dire deflated, and used their pump (no gauge)
> to pump to IIRC 100 psi. Contestants were free to stop, use their thumbs, pump fast or slow, and judge
> the pressure any way they liked, We used a calibrated pressure gauge. The winner was extremely close -
> as I recall, within two psi.

I had a related experience just last week. I was at a LBS to get a new tire/tube which I was ready to install there and then for myself, but the fellow who retrieved the tire for me just went ahead and installed it for me. He inflated with an air line that didn't have a working pressure gauge on it, judging by thumb how where he was with inflating. He told me to finish up with a floor pump. No pumping needed, my tire was at 100psi to as close as the pump gauge would read.

I complimented him for his accuracy, but he dismissed the compliment saying he was actually shooting for 90psi. In retrospect, I do wonder what pressure his compressor is set to.

-Luns

[Frank Krygowski]

On 8/25/2022 2:37 PM, Luns Tee wrote:
>
> The air you bleed out is cool because it expands as it comes out. The temperature drops as it expands just as it increased while compressing. If you only bleed a little bit of air, that's only a little bit of cooling happening. If you take a fully inflated tire that's sat long enough to dissipate all heat from pumping and then let out all the air at the valve, the valve does feel noticably cooler.

Vaguely related: I recall an article from maybe the 1970s? Chrysler
Corporation (IIRC) was trying to find a way to more quickly cool the
interior of a car in summertime, vs. waiting for a conventional air
conditioner to do its job. They investigated a system that used the
fresh air itself as the working medium. The system pumped air to a high
pressure, raising its temperature as well as its pressure. The hot, high
temperature air then passed through a heat exchanger to cool it off.
That air was then allowed to expand, causing its temperature to drop,
and it flowed directly into the passenger compartment.

The account I read said that the executives in the prototype car
actually cheered when the system almost instantaneously began emitting
very cold air. But the process was so noisy it was deemed not worth
pursuing.

--
- Frank Krygowski

[Lou Holtman]

Same as opening your refrigerator door to cool your kitchen?

Lou

[Joy Beeson]

On Mon, 22 Aug 2022 15:15:07 -0700 (PDT), Mark Cleary
<deaco...@gmail.com> wrote:

> Patching a tube I can do but not on the roadside.

I've no idea how many tubes I've patched on the roadside. I don't
*think* that I did it while sitting on gravel in broiling sun more
than once or twice.

Nowadays, all I carry for tire repair is a phone. If the phone ever
fails, I'll walk to the next town. (Mem: make sure my paper list of
numbers is up to date.)

The guy at the Trailhouse works ever so much cheaper than I do.

--
Joy Beeson
joy beeson at centurylink dot net
http://wlweather.net/PAGEJOY/

[Frank Krygowski]

Not at all. Do you not understand the thermodynamics?


--
- Frank Krygowski

[Ralph Barone]

Vortex tubes are my favourite magical air conditioner. Connect compressed
air to a specially shaped chunk of metal. Hot air comes out one end and
cold air comes out of the other.

[Radey Shouman]

Do you not understand the humor?

[Lou Holtman]

Yes professor thermodynamics was my specialization.

Lou

[AMuzi]

heh heh Well known to VW owners who added the 4-barrel
conversion which becomes a big block of ice in cool weather.

[Ralph Barone]

Also magical, but different physics behind it.

https://en.m.wikipedia.org/wiki/Carburetor_icing
vs
https://en.m.wikipedia.org/wiki/Vortex_tube

[Frank Krygowski]

Nope.

--
- Frank Krygowski

[Frank Krygowski]

> Yes professor thermodynamics was my specialization.

Then: Such an odd question!


--
- Frank Krygowski

[Lou Holtman]

It was a joke. It is a solution for a prblem that doesn't exist. How long does it takes for your AC before cooled air comes out of the vents? (serious question). You probably can 'program' your EV to turn on your AC before you leave. It requires an app though. Bummer.

Lou

[Roger Merriman]

Joy Beeson <jbe...@invalid.net.invalid> wrote:
> On Mon, 22 Aug 2022 15:15:07 -0700 (PDT), Mark Cleary
> <deaco...@gmail.com> wrote:
>
>> Patching a tube I can do but not on the roadside.
>
> I've no idea how many tubes I've patched on the roadside. I don't
> *think* that I did it while sitting on gravel in broiling sun more
> than once or twice.
>

For myself that’s zero I do take them home and patch though the MTB tubes
are often so old I tend to bin! Or valve gets sticky! I do take a inner
tube with me, though not with the gravel bike and it’s tubeless always I’m
not sure I’d get valve out and tube in in the field!

> Nowadays, all I carry for tire repair is a phone. If the phone ever
> fails, I'll walk to the next town. (Mem: make sure my paper list of
> numbers is up to date.)
>
> The guy at the Trailhouse works ever so much cheaper than I do.
>

With the MTB I particular I can be remote places that phone may not work,
and so on. So a spare tube in the saddle bag seems a wise choice!

Roger Merriman

[Roger Merriman]

That is indeed one of the advantages of EV’s though to be honest having
decent air conditioning in the car seems to work as well! Ie my old 19 year
Volvo cools rapidly even during the recent heat waves north of 40c

Though nice pootle on the bike nr the river with a ice cream is rather more
pleasant!

Roger Merriman

[Frank Krygowski]

OK. Don't quit your day job!

> It is a solution for a prblem that doesn't exist. How long does it takes for your AC before cooled air comes out of the vents? (serious question).

(Serious answer): On previous cars, not long enough to be objectionable.
That's doubtlessly one of the reasons the system I described was never
put into production. But apparently someone (maybe marketing people?)
though the delay was worth addressing.

I wasn't proposing it as a desirable system. I was just remarking on the
thermodynamics.

> You probably can 'program' your EV to turn on your AC before you leave. It requires an app though. Bummer.

I can do that. I can also do a remote start. To date I haven't.

This car's climate control system is IMO unnecessarily complicated. It
has an "Auto" button with LED that allows me to just set a preferred
temperature; the system will supposedly select AC or heat and blower
speed as necessary. But (no surprise) I'd prefer direct control. And
despite the "Auto" indicator being off, if I dial up "Climate" in the
touch screen, it still says "Auto." The only way I've found to dismiss
that is to turn climate controls completely off.

The system also seems to sometimes impose its will over my choices. I've
manually turned on AC and gotten no cold air for quite a while (like,
well over a minute) then later had the air suddenly blast out cold. And
at times I've seen the "Heat" button illuminated when I know I didn't
push it.

I fear they should not have hired high school kids to do their programming.

--
- Frank Krygowski

[Tom Kunich]

On my Ford Taurus it takes mere seconds. It works so well that I always have the fan on low and the temperature at 68 F.

[Lou Holtman]

Nah, the people in the Far East think differently when it comes to user interfaces. You should have bought a European car ;-)

Lou

[AMuzi]

Maybe.

I loved my early version BMW 2002, a very well engineered
machine, but I find modern ones as inscrutable.as
girlfriend's Toyota.

[Roger Merriman]

I went the other way, with the admittedly old Volvo where when I got it, I
used to attempt to micro manage it, but realised that setting the two sides
to same temps and auto just well works, just occasionally it will feel a
touch airless though a nudge of the windscreen clear button seems to
encourage it.

>
> The system also seems to sometimes impose its will over my choices. I've
> manually turned on AC and gotten no cold air for quite a while (like,
> well over a minute) then later had the air suddenly blast out cold. And
> at times I've seen the "Heat" button illuminated when I know I didn't
> push it.
>
> I fear they should not have hired high school kids to do their programming.
>

Roger Merriman.

[Lou Holtman]

On Friday, August 26, 2022 at 10:18:31 PM UTC+2, AMuzi wrote:
> On 8/26/2022 1:52 PM, Lou Holtman wrote:
> > On Friday, August 26, 2022 at 7:55:36 PM UTC+2, Frank Krygowski wrote:
> >> On 8/26/2022 11:28 AM, Lou Holtman wrote:
> >> .
> >>
> >> I fear they should not have hired high school kids to do their programming.
> >>
> >>
> >
> > Nah, the people in the Far East think differently when it comes to user interfaces. You should have bought a European car ;-)
> >
> > Lou
> >
> Maybe.
>
> I loved my early version BMW 2002, a very well engineered
> machine, but I find modern ones as inscrutable.as
> girlfriend's Toyota.
> --

Ah, BMW i-drive or how is it called. They f*cked that up allright. I did a testride in a colleague ‘s Tesla two months ago. I think you have write a script to turn on the wipers. I knew enough after 10 minutes.

Lou

[John B.]

Geeze but youse guys have a of problems.
If you want the car cool when you get in just send the wife out about
10 minutes early to get it started and the AC turned on.
--
Cheers,

John B.

[Frank Krygowski]

On 8/24/2022 3:06 PM, Frank Krygowski wrote:
> On 8/23/2022 12:49 PM, Frank Krygowski wrote:
>> On 8/22/2022 9:35 PM, Jeff Liebermann wrote:
>>> On Mon, 22 Aug 2022 12:44:29 -0400, Frank Krygowski
>>> <frkr...@sbcglobal.net> wrote:
>>>
>>>> On 8/22/2022 11:59 AM, Tom Kunich wrote:
>>>
>>>>> You and I are in complete agreement. Though I will add that someone
>>>>> or other made a minipump that clamped into a plastic holder attached
>>>>> under the water bottle holder. It had a reasonably easy use and only
>>>>> 100 strokes to bring a tire to pressure.
>>>
>>>> I'm _very_ curious about a mini-pump that required only 100 strokes, if
>>>> you mean 100 strokes from zero to ~100 psi. What specific pump was
>>>> that?
>>>> 250 to 300 strokes seem to be more common.
>>>>
>>>> We could work on this as a physics problem!
>>>
>>> OK.  I'll bite.  I get to pick the pump from my collection:
>>> <http://www.learnbydestroying.com/jeffl/pics/bicycles/misc/bicycle-pumps.jpg>
>>>
>>> Measuring the volume of one stroke is easy.  I fill the pump with
>>> water and measure the volume (or weight) of the ejected water.  That
>>> takes care of all the volume of valves, cavities, hardware and
>>> oddities inside the pump.
>>>
>>> You get to pick the tube and tire sizes.  If you have the actual
>>> dimensions (ID or OD) available that would be handy.
>>>
>>> Calculating the volume of the inflated tube is a bit awkward, but not
>>> impossible.  I could probably measure the volume using water
>>> displacement, but I don't have every size tube and tire handy.
>>>
>>> The math is ideal gas law:
>>> <https://en.wikipedia.org/wiki/Ideal_gas_law>
>>> PV=nRT where:
>>>    P=pressure, V=volume, n=number of moles,
>>>    R=gas constant, T=temperature
>>> When adding more air N (molecules) and P (pressure) will increase.  V
>>> (volume) is constrained by the tire and does not increase.  T
>>> (temperature) will increase, but it's assumed that sufficient time or
>>> coolant are available to bring the tire back to room temperature. This
>>> video grinds through the calculations, except it's for deflation and
>>> not inflation.  Easy enough to change some signs.
>>
>> OK: My mini pump is a Hurricane HP Air Scepter, 0.669" bore, 7.7"
>> stroke. That's 2.7 in^3 per stroke.
>>
>> I just had a bad experience testing it on my 3 speed's rear tire.
>> That's had a very slow leak, as in several days to need air, so it
>> needed pumping anyway.
>>
>> Tire OD is 1.19", and it's a nominal 27" tire. I'm guessing about 1.1
>> ID. Volume is area times circumference at the centroid of that area.
>> So (Pi * ID^2 / 4) * (27" - 1.19") * Pi gives 77.0 in^3 for the tires
>> volume.
>>
>> To begin, the pump needs to inflate the flat tube to zero pressure.
>> That's just volume to volume at the same pressure. 77 in^3 / 2.7 in^3
>> per stroke = 28 strokes.
>>
>> To pressurize that air, if we ignore temperature effects, all we need
>> is P1*V1 = P2*V2. Condition 1 refers to atmospheric air into the pump.
>> Condition 2 is volume at high pressure - say 100 psi? But both must be
>> absolute pressure, so P1 =  14.7 psi and P2 = ~ 114.7 psi. (Extra
>> significant figures only for clarity.)
>>
>> Pump intake volume = V1 = P2 * V2 / P1 = 114.7 * 77 / 14.7 = about 590
>> in^3
>>
>> 590 in^3/ 2.7 in^3 per stroke = 218 strokes...
>> plus 28 strokes to expand a flat tube to full size, so ~ 250 strokes.
>>
>> ...
>>
>> So, the bad experience: I deflated the already soft tube (slow leak,
>> remember?) and began counting. As I hit 250 strokes I heard a hiss.
>> The leak suddenly transformed from slow to fast. I felt air rushing
>> out of the rim at the valve. I disconnected the pump and watched the
>> tire go dead flat.
>>
>> I'll try again later, maybe with a different bike tire.
>
> Bad news on the 2nd trial, or on the calculation.
>
> I fixed the flat. (Oddly, it looked like a micro-bit of glass went into
> the tube from the spoke side, not the pavement side. I must not have
> cleaned things out properly after the last flat long ago.)
>
> Then I attached the mini-pump and began counting. I stopped at 200
> strokes, felt the tire with my thumb and thought "That feels like about
> 75 psi."
>
> Well, my thumb needs re-calibrating, and so do my calculations. Pressure
> gauges said only 55 psi.
>
> I chose not to do a second trial. I'd already worked on brakes for a
> friend's bike, plus fixed that flat, and I have a wiring project
> awaiting me. I pumped to about 80 psi using my floor pump. But 200
> strokes didn't come close to 100 psi.
>
> Discussion is welcome.

Further followup: I repeated the test of pumping that tire with that
mini pump. I stopped at 200 strokes, measured the pressure, and again
got about 55 psi. I added more air, a total of 300 strokes, and measured
about 75 psi. Again, based on relative volumes and pressurizing the air
in the approximate volume of the tire, I expected 250 strokes to yield
about 100 psi. Obviously that's pretty far off.

Sources of error?

I think the big one is the internal volume of the inflated tire. I
estimated that by measuring the inflated tire's width, subtracting my
guess (TM) at wall thickness of tire plus tube to get ID, assuming a
torus (IOW a circular cross section of the inflated tube) and
multiplying that circular cross section by the circumference of the
cross section's centroid. I think that would be acceptably accurate for
a tubular tire. But the "well" of the clincher rim must add much more
volume than I anticipated. More volume to fill yields less pressure
added per pump stroke.

A second source of error might be the filling of the pump barrel. This
pump has an O-ring piston. I think the intake air has to flow past that
O-ring. It may take a bit of time for that air flow to occur, to fully
fill the pump volume with atmospheric pressure, and when pumping fast
there may be incomplete filling. Also, pumping away quickly I may have
not fully retracted the pump handle some percentage of the time.

There seemed to be negligible air loss in removing the pump (just a
quick, quiet "pop") or in measuring pressure using a tire gauge, so I
don't believe those contributed.

The rim is a Wolber Super Champion Mod 58, in 27" size. The tire is a
Pasela, 27" x 1 1/4. If anyone else wants to take a stab at actual air
volume of the inflated tire, have at it.


--
- Frank Krygowski

[Luns Tee]

On Monday, August 29, 2022 at 4:33:39 PM UTC-7, Frank Krygowski wrote:

> Further followup: I repeated the test of pumping that tire with that
> mini pump. I stopped at 200 strokes, measured the pressure, and again
> got about 55 psi. I added more air, a total of 300 strokes, and measured
> about 75 psi. Again, based on relative volumes and pressurizing the air
> in the approximate volume of the tire, I expected 250 strokes to yield
> about 100 psi. Obviously that's pretty far off.

There aren't enough data points to say for sure what's going on, but the ratio of 55psi:75psi doesn't match with 200strokes:300 strokes.

If we assume every stroke delivers the same amount of air, your last hundred strokes put in 20psi, so the first 200 strokes would have delivered 40psi. So these numbers would make sense if you started with 15psi. I doubt that's the case, and imagine the actual case would really be effectively a negative gauge pressure rather than positive. Of course, this is all assuming your gauge is accurate and more importantly, linear.

If the first 200 strokes really delivered more air per stroke than the next 100, I'd guess this is from deadspace left at the end of each pump stroke, with some air compressed by the piston not getting out the checkvalve. The piston will spring back a bit when you let off at the end of the stroke, with that part of the stroke not drawing in air as assumed in your calculations.

Accounting for deadspace and getting pressure as a function of number of strokes isn't too difficult - it's just the sum of a geometric series. Going the other way and extracting parameters (displacement and deadspace normalized to tire volume) might not be too bad either, but is more than I can do in my head at the moment. Having a third data point, say at 100 strokes would help (instead of guessing an appropriate pressure at 0 strokes), but also adds to the question of how much air is lost putting on a pressure gauge.

-Luns

[AMuzi]

I don't know but the o-ring may bleed more significantly at
higher pressures, Cup shaped pistons seal tighter at higher
pressures. I have not observed nor measured this it's just a
thought, given Mr Krygowki's report.

[Luns Tee]

Playing with this a bit, I get that the air in the tire is:

N(n) = N(0)*x^n + (D+V0)*1atm * (x^n-1)*x/(x-1)
where x= V/(V+V0)

Where V is tire volume, D is the pump displacement, and V0 is the pump dead space, in units of your choice. N(n) is the absolute amount of air in the tire after n strokes, in units of volume used for V, D and V0, at 1atm.

This is not a great assumption, but if we assume the tire starts with zero absolute pressure (N=0), that the 55psi and 75psi are gauge pressure, and 1atm is close enough to 15psi, I get that:

(x^300-1)/(x^200-1) = (75+15)/(55+15) = 9/7
x^100 = (1+sqrt(15))/7

V0 = V* 1/(((1+sqrt(15))/7)^(1/100 ))-1
~= 0.00363 V

Frank's estimated tire volume of 77in^3 is V=1262cc. The estimated deadspace would then be 0.00363*1262cc~= 4.6cc. The 17mm pump bore is an area of 2.3cm^2, so the deadspace is equivalent to 4.6cc/2.3cm ~= 2 cm of inaccessible stroke.

This sounds excessive. At 100psi = 7.8atm gauge pressure, the springback after the end of the stroke would be 7.8*2cm = 15.6cm or close to 6 inches. I can't imagine this to go unnoticed, especially on a 7.7in stroke.

So I guess there's something more going on than simple deadspace. Or perhaps not; the o-ring seals on pumps that use them at the piston also function as the intake checkvalve, with the valving being determined not purely by the pressure difference, but also the direction of relative motion causing the o-ring to slide between the sealing and venting sides of its groove. Drag of the o-ring on the pump barrel when the piston starts retracting may be venting the residual pressure, making the springback less than it would otherwise be.

As an anecdote, the floor pump from my high-school days was a Zefal Rush. I believe it uses a rubber cup rather than 0 rings for its piston. I've forgotten how it happened, but I literally lost the guts of its checkvalve. The pump is still usable relying on the presta tire valve to function as the checkvalve. There is a significant amount of springback at the bottom of the stroke at higher pressures, an inch or two or maybe more, from the deadspace of the hose now being upstream of the checkvalve.

> > A second source of error might be the filling of the pump barrel. This
> > pump has an O-ring piston. I think the intake air has to flow past that
> > O-ring. It may take a bit of time for that air flow to occur, to fully
> > fill the pump volume with atmospheric pressure, and when pumping fast
> > there may be incomplete filling. Also, pumping away quickly I may have
> > not fully retracted the pump handle some percentage of the time.

The pump not filling completely to atmospheric pressure on intake is definitely plausible. A 1-2psi drop for air trying to rush in past the plunger would reduce the intake volume 7-15%. I'd try pulling the pump handle out as you would during normal pumping, but immediately releasing it when it hits the end of its travel. Does it spring back in? If so, that's lost travel. However, I'd expect this to happen more at lower pressures when you're able to pump more quickly. When the pressure is higher and you need more force to pump, it's natural to slow down and rest between push strokes; That resting time may allow more air in. Perhaps not though; I imagine one's more likely to rest before pulling the handle rather than after. This can be deliberately controlled though; this would be an interesting experiment to try.

-Luns

[Ralph Barone]

Luns Tee <lu...@berkeley.edu> wrote:
> On Monday, August 29, 2022 at 4:33:39 PM UTC-7, Frank Krygowski wrote:
>
>> Further followup: I repeated the test of pumping that tire with that
>> mini pump. I stopped at 200 strokes, measured the pressure, and again
>> got about 55 psi. I added more air, a total of 300 strokes, and measured
>> about 75 psi. Again, based on relative volumes and pressurizing the air
>> in the approximate volume of the tire, I expected 250 strokes to yield
>> about 100 psi. Obviously that's pretty far off.
>
> There aren't enough data points to say for sure what's going on, but the
> ratio of 55psi:75psi doesn't match with 200strokes:300 strokes.
>
> If we assume every stroke delivers the same amount of air, your last
> hundred strokes put in 20psi, so the first 200 strokes would have
> delivered 40psi. So these numbers would make sense if you started with
> 15psi. I doubt that's the case, and imagine the actual case would really
> be effectively a negative gauge pressure rather than positive. Of course,
> this is all assuming your gauge is accurate and more importantly, linear.
>

Doesn’t your tire start at 14.7 psi, which is atmospheric pressure?

[Frank Krygowski]

OK, some further details based on playing with the tire and pump just now:

I think the dead space is definitely a contributor. I pushed the pump
handle for a full stroke, held it there very briefly, then slowly
released the force. The handle sprung back about one inch.

Before that, I extended the pump handle and applied very, very light
force. The handle slowly slid forward while delivering no air to the
tire. That may mean some leakage past the O-ring is possible. I suppose
it's not guaranteed, though. I think I can envision an O-ring groove
whose diameter tapers in a way that leakage occurs on retraction or on
slow forward motion, but that has a better seal when pressure is higher.

The loss of air when using the gauge is minimal. It's a pencil-style
gauge, the bore is probably ~1/4", and 75 psi moves its piston maybe 2".
The transducer is a simple spring, and I expect it's quite linear.

At this point, I think the errors are due to underestimating tire
volume, plus dead space in the pump. But I haven't bothered to go
through Luns's math.

--
- Frank Krygowski

[Luns Tee]

On Tuesday, August 30, 2022 at 6:40:54 PM UTC-7, Ralph Barone wrote:

> Luns Tee <lu...@berkeley.edu> wrote:
> > There aren't enough data points to say for sure what's going on, but the
> > ratio of 55psi:75psi doesn't match with 200strokes:300 strokes.
> >
> > If we assume every stroke delivers the same amount of air, your last
> > hundred strokes put in 20psi, so the first 200 strokes would have
> > delivered 40psi. So these numbers would make sense if you started with
> > 15psi. I doubt that's the case, and imagine the actual case would really
> > be effectively a negative gauge pressure rather than positive. Of course,
> > this is all assuming your gauge is accurate and more importantly, linear.
> >
> Doesn’t your tire start at 14.7 psi, which is atmospheric pressure?

The 55psi and 75psi values that Frank gave were presumably gauge pressure, so the extrapolation back to zero strokes would also be 15psi gauge pressure. Absolute pressure is 14.7psi more than that.

Besides which, assuming we have a tube in the tire, a deflated tube doesn't generally occupy the entire volume inside the tire casing, so you're starting with less air in the tube than if the tire were filled at atmospheric pressure. Air between the tube and tire gets squeezed out of the picture as the tube inflates to fill the space.

-Luns