Question: Filling rear shock with nitrogen
Steve
nitrogen, and were to get one?
The one I'm looking for is the one with the T to engage and dis-engage the
shrader valve on the shock.
Thanks
Chris Buckley
it. All you really need to do is just use a plain, old tire chuck, set
your nitrogen pressure at about 20 psi higher than your Target Pressure,
fill the shock and remove the chuck as quickly as possible. Due to the
extremely small volume of nitrogen in the shock, you will lose 10-20
lbs. of pressure using this procedure. Bottom line: it's not that
critical.
Chris
SCW
scw
"Steve" <ste...@adelphia.net> wrote in message
news:O0dl8.34693$Ib6.3...@bin7.nnrp.aus1.giganews.com...
David Levy
"Chris Buckley" <cnbu...@earthlink.net> wrote in message
news:3C9570A2...@earthlink.net...
Brewster
GP
nitrogen pressure have on the operation of the shock? I'm guessing
that a typical range is around 180-220 psi and higher pressure will
give you firmer slow speed compression damping?
Greg P.
Chris Buckley <cnbu...@earthlink.net> wrote in message news:<3C9570A2...@earthlink.net>...
David Levy
The purpose of pressure on the oil is to prevent vaporization of the oil at
low pressure (like during shock rebound). Higher/lower pressure will not
affect viscosity or damping (within reason - I would guess 10 million
psi'ses might affect viscosity) as long as vaporization does not take place.
Hootie Pootie to you too.
"GP" <gplas...@hotmail.com> wrote in message
news:f6bc7b29.0203...@posting.google.com...
Jeff Deeney
: i think it's a schrader valve.
Most Ohlins use a little rubber diaphragm that is punctured by a special
needle to pressurize the shock. I disliked this setup, even after I
purchased the special needle. The second time I took my shock apart I
drilled out the center and threaded a shrader valve in it's place. A
little JB weld fillet on both sides to ensure a good seal. It's been
working great.
I second the approach of setting your regulator 20psi higher and using a
standard chuck. Make sure and bleed the N2 line of air first. Give the
shock a couple of fill/empty cycles to get the air out. Not terribly
important, but I'm anal about it. Air is 70% nitrogen anyway.
-Jeffrey Deeney- DoD#0498 NCTR UTMA BRC COHVCO AMA
'99 ATK 260LQ-Stink Wheels '94 XR650L-DreamSickle
We don't stop riding because we get old, we get old because we stop riding.
Chris Buckley
"Cavitation" is the key word here, the nitrogen pressure against the the
oil keeps the shock piston from cavitating and foaming up the oil. In
other words, consistent damping under all conditions. (in theory)
Chris
Steve
price on just the valve.
Steve
"Jeff Deeney" <nos...@thank.you@PROBLEM_WITH_INEWS_GATEWAY_FILE> wrote in
message news:a75f3m$6i4$2...@fcnews.fc.hp.com...
jeff dunham
"plunger chuck" but I am not sure. Race-tech sells something simpler
than the motion-pro (which I have) for $99.00. They have it listed on
their website www.race-tech.com.
jeff
'01 gasgas ec300
My Sponsors...
www.smackovermotorsports.com => The GasGas Parts Warehouse
www.lt-racing.com => GasGas Performance Accessories and Services
MX Tuner
<cnbu...@earthlink.net> wrote:
>Your opinion is pretty much spot on.
>
>"Cavitation" is the key word here, the nitrogen pressure against the the
>oil keeps the shock piston from cavitating and foaming up the oil. In
>other words, consistent damping under all conditions. (in theory)
>Chris
Yup. But higher nitrogen pressure will have a significant impact on
the compression damping. This is an easy trick to use for stock shocks
for heavier riders. FYI, stock pressure in most jap shocks is 10 bar
or 145 psi. A revalved shock normally runs in the 175psi range. XR's
use a much higher pressure (250 psi range).
MX Tuner
Jeff Howe
"MX Tuner" <mxt...@mindspring.com> wrote in message
news:3c967d9b...@news.mindspring.com...
FYI, stock pressure in most jap shocks is 10 bar
> or 145 psi.
> MX Tuner
Maybe thats what they want, but thats not what I'm seeing. I get brand new
shocks off the showroom with 125psi. This is not the exception anymore, it
is the norm. I have not had one new shock here this year yet that bested
130psi. Lowest I had so far was a 02 CR125 with 110 psi. 02 YZ 250 with
20 hrs on it, 125 psi, partial bladder collapse, bladder rubbing on
reservoir wall. The shock was cavitating straight from the factory. This
is common.
I've been checking this for the last 2 years now and am blown away they are
so sloppy about it, but then I guess I shouldn't be. Me thinks dealer prep
should include a nitrogen spritzer before they hit the floor now too. I'm
willing to bet that 90% of stock jap bike shocks are cavitating at least a
little bit when new.
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
> MX Tuner
Jeff Howe
to your question too. Race Tech does sell just the valve seperate as well.
You don't have to buy the $90 guage setup from them.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"Steve" <ste...@adelphia.net> wrote in message
news:4Dtl8.30667$%j5.15...@bin2.nnrp.aus1.giganews.com...
whereami
have them.
Nowadays I use bicycle shock pump for filling my shock. I have always used
air anyway since the shock oil is separated from the air.
Randy
Phil Scott
Air is something like 70%+ nitrogen.... and the rest other gasses, oxygen,
hydrogen, argon etc and water vapor.
The reason pure 'dry' nitrogen is used is because it precludes the oxygen (that
fuels corrosion, and water vapor which also fuels corrosion of the parts).
If I were going to use ordinary compressed air I would dry it first... that
would be a multi stage process. first Id let the air cool in the compressor
tank. then Id run it through a refrigeration service drier (1/4" flare
fittings) on the hose line you use to charge the shock.
that would work about as well as pure nitrogen. imho.
Phil Scott
David Levy
thousands of barrels in a reservoir). If it is incompressible, higher
pressure is of no significance.
"MX Tuner" <mxt...@mindspring.com> wrote in message
news:3c967d9b...@news.mindspring.com...
>
> Yup. But higher nitrogen pressure will have a significant impact on
> the compression damping.
><snip>
> MX Tuner
David Levy
The name of the valve is "the valve that you use to recharge the shock
thingy with nitrogen".
The price of the "the valve that you use to recharge the shock thingy with
nitrogen" is more than the price of what all the dumbasses that wasted
bandwidth here have spent on their entire setup - cylinder, schrader valve
chuck, fittings, and tubing to refill their shocks.
Hell, I even learned that I can tap and install a shrader valve into my
Ohlins shock (thanks Jeff!).
Your welcome.
"Steve" <ste...@adelphia.net> wrote in message
news:4Dtl8.30667$%j5.15...@bin2.nnrp.aus1.giganews.com...
john
Levey if ya need a few email me
john
A banker is someone who lends you an umbrella
when the sun is shining, and who asks for it back
when it start to rain.
"David Levy" <.com>
john
big envelope when you want to send a tinny weenie
thing
john
heck why not put ship it in a refrigerator box.
"john" <縪hn@衡め.将� wrote in message news:a77imp$snl$1...@plonk.apk.net...
MX Tuner
wrote:
>> Yup. But higher nitrogen pressure will have a significant impact on
>> the compression damping.
>Why? Oil is essentially incompressible (unless you are dealing with
>thousands of barrels in a reservoir). If it is incompressible, higher
>pressure is of no significance.
The oil isn't compressible but the higher pressure in the reservoir
slows the rate at which the oil enters the reservoir, going through
the compression adjuser. The pressure in the bladder pushes against
the oil.
MX Tuner
MX Tuner
<trakc...@netscape.net> wrote:
>
>
>"MX Tuner" <mxt...@mindspring.com> wrote in message
>news:3c967d9b...@news.mindspring.com...
>
>
>FYI, stock pressure in most jap shocks is 10 bar
>> or 145 psi.
>
>> MX Tuner
>
>Maybe thats what they want, but thats not what I'm seeing. I get brand new
>shocks off the showroom with 125psi. This is not the exception anymore, it
>is the norm. I have not had one new shock here this year yet that bested
>130psi. Lowest I had so far was a 02 CR125 with 110 psi. 02 YZ 250 with
>20 hrs on it, 125 psi, partial bladder collapse, bladder rubbing on
>reservoir wall. The shock was cavitating straight from the factory. This
>is common.
>
>I've been checking this for the last 2 years now and am blown away they are
>so sloppy about it, but then I guess I shouldn't be. Me thinks dealer prep
>should include a nitrogen spritzer before they hit the floor now too. I'm
>willing to bet that 90% of stock jap bike shocks are cavitating at least a
>little bit when new.
Interesting. Heck, I've never checked one I was pulling apart. I'll
check the next few and see what I come up with.
Have you checked shocks you've been into and know the pressure they
were set at? Do you find they bleed down at all?
MX Tuner
MX Tuner
wrote:
>The reason pure 'dry' nitrogen is used is because it precludes the oxygen (that
>fuels corrosion, and water vapor which also fuels corrosion of the parts).
No, they recommend nitrogen because it is more temp stable.
>If I were going to use ordinary compressed air I would dry it first... that
>would be a multi stage process. first Id let the air cool in the compressor
>tank. then Id run it through a refrigeration service drier (1/4" flare
>fittings) on the hose line you use to charge the shock.
>
>that would work about as well as pure nitrogen. imho.
For about the first 5 minutes of riding......
MX Tuner
Jeff Howe
don't know. I have yet to see any major loss, but I have seen some lose as
much as 15psi in a season. Most I get back are maybe 5psi loss. I guess
this is something I would like to find out more about.
Today I had 2 shocks that had never been serviced since leaving the floor.
00 RM 250, and 99 KX250. 00 RM shock pressure was 110psi, bladder was
collapsed pretty good. 99 KX shock pressure 85psi, what a mess!! Bladder
was wasted, oil was WAY contaminated. The anodizing was beginning to wear
off the internal shock bore. People don't realize how bad their stuff is.
This is why annual service at the bare minimum is a must. It's also why I
developed my own synthetic fluids. Using a quality oil in them is a must on
these things since everybody ignores them until it's too late. Sure you
would like to get every job back at least seasonally to freshen it up, but
most guys just won't do it, or they sell the bike. Use a HI VI synthetic
shock oil. Skip the petroleum. I've seen the advantages over the last 3
years to know it's worth it and even though it might cost a little more you
are doing your customer a favor.
Consider in the more severe cases of cavatation your going to suck your
sealhead down in the body. You've seen the crud under the shock caps, and
you now have that wearing away on your shock bore. I had a 93 CR 250 in
here last summer with 50psi on it. Had that shock not had the 2 retaining
clip system it would have fried the body. The bladder was a total wad, and
I mean like you crumpled it in your hand. Having the shock turn into a pump
is not good.
The cool thing with checking the pressure before you open them up is you
know what your going to see in there before you get into it.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"MX Tuner" <mxt...@mindspring.com> wrote in message
news:3c97cd0...@news.mindspring.com...
Jay C
> The cool thing with checking the pressure before you open them up is you
> know what your going to see in there before you get into it.
How do you check pressure without a presurized fill backing you up? I would
think that with such a small volume of gas, any type of meter/gauge would
take up enough volume to give a false (low) reading.
90% of measured stock shocks low you say? Seems unlikely (at least I hope
it is ;). Are you sure that isn't simply false readings due to gas filling
your gauge?
Jay
The Deeneys
Phil Scott <phils...@hotmail.com> wrote in message
> The reason pure 'dry' nitrogen is used is because it precludes the oxygen
(that
> fuels corrosion, and water vapor which also fuels corrosion of the parts).
>
> If I were going to use ordinary compressed air I would dry it first...
that
> would be a multi stage process. first Id let the air cool in the
compressor
> tank. then Id run it through a refrigeration service drier (1/4" flare
> fittings) on the hose line you use to charge the shock.
>
> that would work about as well as pure nitrogen. imho.
With all due respect, there is another very good reason for using
compressed N2 instead of air. Highly compressed oxygen in
direct contact with hydrocarbon fumes (i.e. oil vapor) can be very
unstable at elevated temperatures. Touch your shock body after
riding hard for a while. Granted, I think the risk of explosion is
small, but signficant. That would ruin my day if the shock exploded
beneath me.
N2 is cheap. It only cost pennies to fill a shock. It's the service
charge that is expensive. I think next time I need a refill I'm going to
buy the tank and regulators. I think a setup can be had for <$200.
I can recoup some of the costs by charging buddies $5 for a
a charge. They'll save a lot of money as well. Refilling the tank
should only cost a couple of $$. Another advantage of having
a tank, you can carry it on trips with you and use it to run air
tools (for a little while anyway) and to fill tires.
-Jeffrey Deeney- ©2002 DoD#0498 NCTR UTMA BRC COHVCO AMA
jde...@frii.nospam.com '99 ATK 260LQ-Stink Wheels '94 XR650L-DreamSickle
The Deeneys
David Levy <dl...@pobox.com> wrote in message
news:a77hes$j2pi5$1...@ID-132159.news.dfncis.de...
> Hell, I even learned that I can tap and install a shrader valve into my
> Ohlins shock (thanks Jeff!).
Make sure and put locknuts on both inner and outer surfaces of the stem.
JB weld for a good seal.
> Your welcome.
Thank you... I think...
BTW, if anyone want the needle kit for filling Ohlins, I'll part with mine
cheap. I think it cost $25 new. I'll let it go for a $10 donation to
USA-ALL :-)
-Jeffrey Deeney- ©2002 DoD#0498 NCTR UTMA BRC COHVCO AMA
jde...@frii.nospam.com '99 ATK 260LQ-Stink Wheels '94 XR650L-DreamSickle
Jeff Howe
results of low pressure. Read what I wrote about the 02 YZ with 20hrs on
it. At the same time I did that bike I had a 02 YZ 125 in here right off
the floor that gave the exact same reading of 125psi. New, that bladder had
no indication of wear of course, but a shock with the same pressure reading
with 20 hrs on it was showing problems existed.
Sure we're eating up a little pressure, but it may not be what your hoping
for. I have no reason to lie about this stuff. My gauge doesn't have a big
long hose on it, and the volume in question is pretty small. Heck, the
gauge could be out of whack, but internal inspection seems to back it up.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"Jay C" <jwc.N...@sysmatrix.net> wrote in message
news:3c980...@news.vic.com...
Phil Scott
>On Tue, 19 Mar 2002 12:31:19 GMT, phils...@hotmail.com (Phil Scott)
>wrote:
>
>>The reason pure 'dry' nitrogen is used is because it precludes the oxygen (that
>>fuels corrosion, and water vapor which also fuels corrosion of the parts).
>
>No, they recommend nitrogen because it is more temp stable.
Could be, but air is over 70% nitrogen anyway and the rest of the components
dont change pressure much differently than nitrogen in the ranges we live in...
nitrogen and inert gasses are used in many industrial applications because they
are innert and oxygen isnt..its quite active.
>
>>If I were going to use ordinary compressed air I would dry it first... that
>>would be a multi stage process. first Id let the air cool in the compressor
>>tank. then Id run it through a refrigeration service drier (1/4" flare
>>fittings) on the hose line you use to charge the shock.
>>
>>that would work about as well as pure nitrogen. imho.
>
>For about the first 5 minutes of riding......
Could be, I'd have to look the pressure /temp/ enthalpy charts up in my ashrae
guide to know by how much. Do you have figures on that? or ever tried air? I
havent myself.
Phil Scott
>
>MX Tuner
Tim Harrell
The main reason for using N2 instead of air is that water vapor in any
quantity will result in huge pressure increases with temperature
increases. If you had a source of truly dry compressed air, the
difference between that and nitrogen would be quite minor, since all of
the other constituents of air are gaseous at all temperatures that the
shock is likely to see. Water vapor, however, is perpetually hovering
around phase change points (i.e. from solid to liquid to gas). A tiny
droplet of water, which could very well condense and get injected into
the bladder while filling with air, changes it's volume by a huge amount
when turning to vapor (steam). I don't remember the factor off the top
of my head, almost 20 years since Thermodynamics, but it's several
orders of magnitude. Since the volume is controlled by the shock body
and bladder, that means that the phase change of that droplet of water
will result in very large changes of pressure.
Tim H.
Phil Scott
PS... in my business we use various gasses, and the smaller molecule gasses,
such as hydrogen and helium (components of air) will leak or even osmos through
materials where the larger molecules wont. Nitrogen is one of the larger air
molecules so would be more stable in a container than an air mix.. as its
lighter components leaked... so there are apparently good reasons for using
nitrogen aside from it inert qualities.
Phil Scott
>
>
>>
>>MX Tuner
>
john
to fill a gauge..... if you are measuring lower pressures
in a small reservoir then yes line & gauge volumes play a bigger role
very high pressure trapped then released is quite impressive.
i have seen results of a super high pressure release of film canister size
vessel (simulate atomic blast) in a pressure lab....blew the vault door
right off, and they say government jobs are boring...(that kind of
boring i can do without thank you very much)
john
afraid of small shinny objects.news:3c98265c$0$1427$9ba6...@news.pclink.com...
john
still maintaining that bloated look from the remaining gas.
john
"Phil Scott" <@hotmail.com> wrote in message
news:3c982454...@news.tdl.com...
> On Wed, 20 Mar 2002 05:28:13 GMT, @hotmail.com (Phil Scott) wrote:
>
> >On Tue, 19 Mar 2002 23:46:05 GMT, @mindspring.com (MX Tuner) wrote:
> >
> >>On Tue, 19 Mar 2002 12:31:19 GMT, @hotmail.com (Phil Scott)
Jay C
> Sure we're eating up a little pressure, but it may not be what your hoping
> for. I have no reason to lie about this stuff. My gauge doesn't have a
big
> long hose on it, and the volume in question is pretty small. Heck, the
> gauge could be out of whack, but internal inspection seems to back it up.
Gee... touchy.
What I meant was simply that a gauge could easily chew up significant
pressures given the small volumes involved. A little and imperceptable slip
while sticking on the gauge could release another significant amount... who
knows? Obviously, you can see trends doing what you are doing... when you
read 110PSI, then 85PSI, then 50PSI... obviously you can see that one is
lower pressure than the other - you stated that the shocks with lower
pressure readings typically their internals all trashed - OK then - you know
what low pressure does. I wasn't debating that issue. What I was
questioning was your statement that brand-new OEM shocks were all over the
place and the great majority of them were out of spec (not that it would
suprise me). It seems to me that putting on a simple pressure gauge creates
enough variability that direct comparisons would be impossible - I was also
under the impression, and advised some time ago, that measuring the pressure
in a shock was considered impossible for those reasons. I was told that if
you put a gauge on a shock, then you would loose enough pressure to need a
re-charge - made sense to me. That's why I was curious if you had some more
high-tech measuring method. That's all.
An easy enough test would simply be to charge a shock to a known pressure
using your input system then stick your gauge on it. At least that way you
could know what the typical pressure loss would be given a type of shock and
a given gauge. Even easier would be to measure a freshly topped-off shock
(worst-case scenario is max pressure), take off the gauge, then measure it
again. The second measurement will probably be lower - how much lower is
the question. Top it off and try it again. Do it a couple of times and see
how repeatable the measurements are. It might give you some more insight on
what you are seeing (or maybe not, depending on the results).
Jay
Jay C
Possibly, but I'd tend to believe that the PV=nRT relationship is pretty
similar between nitrogen and air. I always thought that nitrogen was used
specifically because it is an inert gas and will not react with the shock
internals. I've also heard that a danger exists if some of the oil leaks
past the chamber seal, then the shock could diesel and explode like a bomb
(now that would be a SERIOUS case of monkey-butt) - a good argument. I
still think that it is the non-corrosive qualities that make nitrogen
primarily attractive though. Air would eventually lead to internal
corrosion due to trace moisture and oxygen being present.
Jay
David Levy
in performance but I must say I was scared that it might blow up. They do
get hot.... and there is oil and air in there. Mine never blew up though.
Now I have a N2 cylinder. I bought everything at mcmaster.com. I had some
1/4" ss tubing laying around and used that with some Swagelok fittings. A
newly serviced shock is like a clean pair of underwear.
"The Deeneys" <dee...@nospam.frii.com> wrote in message
news:3c981356$0$86432$7586...@news.frii.com...
> With all due respect, there is another very good reason for using
> compressed N2 instead of air. Highly compressed oxygen in
> direct contact with hydrocarbon fumes (i.e. oil vapor) can be very
> unstable at elevated temperatures. Touch your shock body after
> riding hard for a while. Granted, I think the risk of explosion is
> small, but signficant. That would ruin my day if the shock exploded
> beneath me.
>
><snip>
Dudley Cornman
> The reason pure 'dry' nitrogen is used is because it precludes the oxygen
(that
> fuels corrosion, and water vapor which also fuels corrosion of the parts).
>
Isn't it also alot more stable under heat and pressure than ordinary
compressed air...
> If I were going to use ordinary compressed air I would dry it first...
that
> would be a multi stage process. first Id let the air cool in the
compressor
> tank. then Id run it through a refrigeration service drier (1/4" flare
> fittings) on the hose line you use to charge the shock.
>
> that would work about as well as pure nitrogen. imho.
It seems that I recall reading that what you propose is dangerous...
dsc
Dave Sparkman
<dl...@pobox.com> writes:
>A
>newly serviced shock is like a clean pair of underwear.
Are you saying that you change your undies every 6 months?
-Dave-
YZ 125
WR 200
TSCEC # 432
RMEC # 3030
Dudley Cornman
> a tank, you can carry it on trips with you and use it to run air
> tools (for a little while anyway) and to fill tires.
But... but.... but... won't your tires be a lot heavier filled with nitrogen
rather than the helium we RMDers usually use? :)
dsc
David Levy
I'm not sure that it slows the fluid but I would think it shifts the
pressure by which is required by the shock to begin pushing fluid through
the compression adjuster. Anyway, thanks for explaining.
"MX Tuner" <mxt...@mindspring.com> wrote in message
news:3c97cc6...@news.mindspring.com...
MX Tuner
<trakc...@netscape.net> wrote:
>Yeah Mark, I notice they do bleed down a bit and it seems to vary. Why? I
>don't know. I have yet to see any major loss, but I have seen some lose as
>much as 15psi in a season. Most I get back are maybe 5psi loss. I guess
>this is something I would like to find out more about.
The whole set up isn't what I'd call a leak proof seal anywyas. I can
see how a small amount might seep out over time.
>Today I had 2 shocks that had never been serviced since leaving the floor.
>00 RM 250, and 99 KX250. 00 RM shock pressure was 110psi, bladder was
>collapsed pretty good. 99 KX shock pressure 85psi, what a mess!! Bladder
>was wasted, oil was WAY contaminated. The anodizing was beginning to wear
>off the internal shock bore.
I've seen more KX/KDX shocks do this than most all other shocks
combined. I didn't think about the possibility of low pressure causing
it.
>Consider in the more severe cases of cavatation your going to suck your
>sealhead down in the body. You've seen the crud under the shock caps, and
>you now have that wearing away on your shock bore. I had a 93 CR 250 in
>here last summer with 50psi on it. Had that shock not had the 2 retaining
>clip system it would have fried the body.
I always wondered why they have two circlips. Interesting.
>The bladder was a total wad, and
>I mean like you crumpled it in your hand.
I've seen more than a couple like that. Looks like one of those weird
little green tropical fruit thingies.
>The cool thing with checking the pressure before you open them up is you
>know what your going to see in there before you get into it.
I'm definitely going to do that. Thanks for the insight!
MX Tuner
Wes
> In article <a7amp5$jlpmd$1...@ID-132159.news.dfncis.de>, "David Levy"
> <dl...@pobox.com> writes:
>
> >A
> >newly serviced shock is like a clean pair of underwear.
>
> Are you saying that you change your undies every 6 months?
Or whenever the fluid is leaking around the seals, whichever comes first.
Wse
David Jones
Even then, all you usually have to do is run a business card around
them to loosen and displace the crud.
>Wse
David - '02 KTM200 EXC (virgin)
http://www.motosports-boise.com/rmd
"The Very Unofficial RMD Homepage"
Tim Harrell
>
> On 20 Mar 2002 18:29:05 -0800, wes...@arraycomm.com (Wes) wrote:
>
> >dspa...@aol.com (Dave Sparkman) wrote in message news:<20020320144909...@mb-bd.aol.com>...
> >> In article <a7amp5$jlpmd$1...@ID-132159.news.dfncis.de>, "David Levy"
> >> <dl...@pobox.com> writes:
> >>
> >> >A
> >> >newly serviced shock is like a clean pair of underwear.
> >>
> >> Are you saying that you change your undies every 6 months?
> >
> >Or whenever the fluid is leaking around the seals, whichever comes first.
>
> Even then, all you usually have to do is run a business card around
> them to loosen and displace the crud.
>
> >Wse
>
> David - '02 KTM200 EXC (virgin)
Paper cuts!!!!
Oh, the humanity.
Tim H.
Dudley Cornman
> >> Are you saying that you change your undies every 6 months?
> >
> >Or whenever the fluid is leaking around the seals, whichever comes first.
>
> Even then, all you usually have to do is run a business card around
> them to loosen and displace the crud.
Remind me to never accept a busines card from this fellow... :)
dsc
Rowdy
<snip>
> (worst-case scenario is max pressure), take off the gauge, then measure it
> again. The second measurement will probably be lower - how much lower is
Your my hero Jay. That's exactly what i was going to suggest!
Know your measurement error or skip the measuring altogether.
I suggest the following procedure:
- attach filling system
- fill up to pressure indicated as "A"
- remove filling system => unknown pressure "B" due to disengagement loss
- attach gauge
- measure pressure => known error pressure "C"
- remove gauge
- measure pressure => known error pressure "D"
- attach filling system
- fill up to "desired pressure" + (A - B)
- now you _know_, that the shock ist filled to exactly the "desired pressure"
B = C + (C - D) (assuming gauge attachment loss >> detachment loss)
B was the actual pressure after filling the shock to "A psi indicated"
and removing the filling system (e.g. customer pressure)
C - D is what you loose at each gauge measurement (actually the sum of
gauge attachment loss, gauge filling loss and gauge detachment loss)
as long as C - D << C the value of C-D ("measurement loss") will be rather
constant (e.g. independent of C) and only depending on the shock's gas reservoir
volume, the volume of the gauge and hose and one's way of attaching and detaching
the gauge.
Rowdy
Rowdy
>
<snip Tuner sez: nitrogen pressure affects compression damping>
> Got it. I stand before you enlightened!
Well i don't, yet. Facts as i see them:
- oil is incompressible, at our shock's pressures at least
- the piston doesn't cavitate, because take a well services example
- there is a nitrogen filled bladder in the reservoir
- it exerts the high pressure onto the oil surrounding it
- this pressure shows up everywhere, hence prevents cavitation
as far away from the bladder as "at the piston"
- the dampening action results from the piston forcing oil through
well defined and clicker adjustable orifices within the shock body
- the compression damper clicker does not guard a flow of oil from shock
body into reservoir during compression. This amount of oil would be
"missing" in the shock's body, would only be possible in case of cavitation.
- Otherwise compression damping would transfer oil into the reservoir,
thereby compressing the nitrogen bladder and creating a high rate gas spring,
not what a damper is meant to do
- even during hefty dampening action there is virtually no oil flow to or
from the reservoir, except for the expanding of oil volume due to heat
- the reservoir is just that: a reservoir whose main purpose is to dissipate
the heat and slow down the effect of changed viscosity from heating up
the oil
- hence the nitrogen pressure is irrelevant and has zero effect
as long as it's high enough to prevent cavitation.
- the only reason for all this reservoir thingies and pressurized nitrogen
is to lessen the effect of the heating oil onto the dampening action, by introducing a bigger casing surface (some even with heat dissipation ribbing),
more oil to store the heat and a high base pressure which prevents cavitation.
Where am i wrong here?
Rowdy
David Levy
the shock body must be higher than pressure in the reservoir bladder.
Raising the pressure in the reservoir bladder will shift the required shock
body pressure up to initiate flow into the reservoir bladder.
It makes a difference as to which side of the compression damper the
compressible nitrogen filled bladder is located.
"Rowdy" <peter....@gmx.net> wrote in message
news:3C99E776...@gmx.net...
>
> Well i don't, yet. Facts as i see them:
>
><snip>
>
>
> Rowdy
whereami
reservoir and the shock body. The rebound adjuster opens a hole on the
shock shaft which allows the oil to bypass the piston which seems to defeat
the purpose of the piston and shim pack since the oil can flow both ways
through the hole.
Cavation is not a problem if it is designed into the system. It doesn't
matter what happens inside the shock as long as you get the desired
effects. My Ohlins shock requires 210 psi and the use of Husky
automatic tansmission fluid. Thats what the engineers designed the system
for in order to make the shock work properly.
Randy
Rowdy <peter....@gmx.net> wrote in news:3C99E776...@gmx.net:
Jeff Deeney
Man, I can't believe I'm jumping into this geek-fest :-)
: Well i don't, yet. Facts as i see them:
You are close.
: - oil is incompressible, at our shock's pressures at least
: - the piston doesn't cavitate, because take a well services example
: - there is a nitrogen filled bladder in the reservoir
: - it exerts the high pressure onto the oil surrounding it
: - this pressure shows up everywhere, hence prevents cavitation
: as far away from the bladder as "at the piston"
: - the dampening action results from the piston forcing oil through
: well defined and clicker adjustable orifices within the shock body
So far so good.
: - the compression damper clicker does not guard a flow of oil from shock
: body into reservoir during compression. This amount of oil would be
: "missing" in the shock's body, would only be possible in case of cavitation.
: - Otherwise compression damping would transfer oil into the reservoir,
: thereby compressing the nitrogen bladder and creating a high rate gas spring,
: not what a damper is meant to do
: - even during hefty dampening action there is virtually no oil flow to or
: from the reservoir, except for the expanding of oil volume due to heat
: - the reservoir is just that: a reservoir whose main purpose is to dissipate
: the heat and slow down the effect of changed viscosity from heating up
: the oil
: - hence the nitrogen pressure is irrelevant and has zero effect
: as long as it's high enough to prevent cavitation.
This is where you are in error. On most shocks, the compression clicker
is located between the shock body and the reservoir. This clicker
controls how easily oil flows between the shock body and the reservoir.
Oil does flow between the shock body and reservoir as the shock
compresses. The oil flow is equal to the volume of the rod entering the
shock body. If it didn't, the shock would not be able to compress,
since the compressible gas is located in the reservoir.
The presurized reservoir does act as a gas spring. The gas spring
provides no damping, and therefore oil pressure will not affect damping
characteristics.
: - the only reason for all this reservoir thingies and pressurized nitrogen
: is to lessen the effect of the heating oil onto the dampening action, by introducing a bigger casing surface (some even with heat dissipation ribbing),
: more oil to store the heat and a high base pressure which prevents cavitation.
The reservoir does help cool oil as you mentioned. It also provides a
larger source of oil. As I mentioned, oil is constantly moving back and
forth between the shock body and reservoir.
: Where am i wrong here?
If you're still in doubt, tear your shock down. During the bleeding
process, watch what happens to the oil level in the reservoir as you
stroke the shock up and down. This is much easier to observe on a
non-piggyback shock.
-Jeffrey Deeney- DoD#0498 NCTR UTMA BRC COHVCO AMA
Rowdy
> It makes a difference as to which side of the compression damper the
> compressible nitrogen filled bladder is located.
Exactly!
I am (currently) thinking of the shock damping system to be some kind of loop:
"Above the piston" is the oil that will be compressed when compression
damping is happening. The piston tries to push it through some adjustable
orifice (compression clicker) and into a feed back tube/passage that brings
the oil back to the place "below the piston", BYPASSING the rebound orifice.
(high pressure "before" the compression clicker, std. nitrogen system pressure
after it)
The "below the piston" volume contains the oil that gets compressed when
rebound damping takes place. The piston forces said oil through the
rebound clicker orifice and into the same feed back tube/passage, so that
the oil enters the space "above the piston" BYPASSING the compression orifice.
Were there no temperature, oil expansion and cavitation issues
that close system concept would do fine, w/o any reservoir or nitrogen.
Personally, i can't believe that the reservoir is entering the shock's body
at any location that sees damping action created pressure, because then
the oil would take the easy way out:
Instead of squeezing past the clicker orifice it would simply pour into
the reservoir, heavily compressing the nitrogen bladder in the process.
Clearly not what we would want for a decent damper.
still not seeing the light, how nitrogen pressure could affect compression
damping
Rowdy
Wes
You left out the volume of oil the shaft displaces as the shock
compresses. That's the flow of oil into the reservoir the compression
clicker works against.
For the orifices and shim stacks on the piston to do anything, there
has to be a pressure drop across the piston. The nitrogen pressure
making everything equal only fits when the shock is motionless. It's a
physics thing.
Higher nitrogen pressure raises the compression force of the shock, in
relation to pressure times area of the shaft. Pressure drop across the
piston probably has a delta offset related to gas pressure as well,
but I'm a little foggy on this part.
Hook a hose to both sides of a hydraulic cylinder, and it'll extend.
Wes
Wes
>
> It makes a difference as to which side of the compression damper the
> compressible nitrogen filled bladder is located.
Umm ... yeah, it does. If you had it between the piston and the
compression valve, with no compressible reservoir behind the valve,
the valve wouldn't do a damn thing. The bladder would compress, and
rebound back, like an undamped spring. Net work done, zero.
That's what you meant, right?
Wes
Jay C
> I suggest the following procedure:
> B = C + (C - D) (assuming gauge attachment loss >> detachment loss)
> B was the actual pressure after filling the shock to "A psi
indicated"
> and removing the filling system (e.g. customer pressure)
> C - D is what you loose at each gauge measurement (actually the sum of
> gauge attachment loss, gauge filling loss and gauge detachment
loss)
> as long as C - D << C the value of C-D ("measurement loss") will be
rather
> constant (e.g. independent of C) and only depending on the shock's gas
reservoir
> volume, the volume of the gauge and hose and one's way of attaching and
detaching
> the gauge.
Wow Rowdy, I had no idea you were such a nerd. Cool.
Jay
gEEk
Jeff Howe
enough to worry about. My point is simply that I would like to see the
OEM's giving more of a safety factor to the shock charge. 140 psi can be
really close to cavatation, using 175 hurts nothing performance wise and
gives a margin of safety. Granted my gauge checking is not perfect, but I
know the shocks I'm getting here straight off the floor need more pressure.
The information I give on this is to help people out, rather I seem to get
the feeling you would rather not know any of this so I'll just keep my mouth
shut concerning my profession and continue here as a rider.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"Jay C" <jwc.N...@sysmatrix.net> wrote in message
news:3c98cdb2$1...@news.vic.com...
john
just when i though i knew how shocks worked
some dern foreigner comes in and muddies the water
john
don't make me derive some integrals on you
calc-use-less
"Jay C" <jwc.N...@sysmatrix.net> wrote in message
news:3c9a2749$1...@news.vic.com...
Jay C
> I did it 10 times today on 2 different shocks, gauge eats up 6psi.
Now you know. Must've been a good idea too...you did it.
> Not enough to worry about. My point is simply that I would like to see
the
> OEM's giving more of a safety factor to the shock charge. 140 psi can be
> really close to cavatation, using 175 hurts nothing performance wise and
> gives a margin of safety.
Sounds reasonable to me. Are you saying that OEMs specify shock pressures
too low? What is a typical OEM spec anyway - aren't they around 175PSI? My
XR400 is supposed to be charged to 215#, or something around there - I know
the spec is way higher then the CRs - the higher pressure must have
something to do with the shorter stroke (compared to a CR), I would think.
> Granted my gauge checking is not perfect, but I
> know the shocks I'm getting here straight off the floor need more
pressure.
Need more pressure for what you feel is necessary, or to be within OEM spec?
I am still not clear on exactly what you mean by "need".
> The information I give on this is to help people out, rather I seem to get
> the feeling you would rather not know any of this so I'll just keep my
mouth
> shut concerning my profession and continue here as a rider.
What gives you that idea - if I didn't want to know, then why do you think
I'm asking all of these questions? You seem to be stuck on this idea that
you are being attacked, for some reason. You need to lose the persecution
complex. The fact that a dozen different people questioned your methods,
your findings, and your hypothesis based on those findings tells me exactly
the opposite. People ask questions and propose alternatives and
improvements to learn and to verify, not to attack.
No one who responded to your posts (at least that I read), including me,
disputed you claims that low pressures damage shocks (which I think was
supposed to be your original point)... but many questioned your methods for
determining that pressures were low in the first place - after all, an
accurate and non-destructive method of checking shock pressures is something
that everyone would like to know.
Besides, you didn't have a clue how much your gauge corrupted a pressure
reading - now you know. Knowledge is rarely free.
Jay
David Levy
right?
For discussions sake, the shock is on the left, the compression adjuster is
in the middle, and the reservoir is on the right.
There is resistance of flow through the compression adjuster, correct?
Let's look at the compression stroke of the shock. The shaft moves up and
oil is forced through the piston. If shaft speed increases enough, pressure
above the piston increases eventually opening up flow through the
compression adjuster to the reservoir. Shaft
speed/pressure-above-the-piston must increase enough to open the compression
adjuster and begin to collapse the reservoir bladder. If the reservoir
bladder does not collapse - no flow. Higher pressure in the bladder means
higher resistance to collapse of the bladder which would translate into
firmer compression damping.
Hey, I know how we can verify this. Put water in the bladder. Let's do it
to Mike W.'s shock?
"Rowdy" <peter....@gmx.net> wrote in message
news:3C9A164C...@gmx.net...
><snip>
> Personally, i can't believe that the reservoir is entering the shock's
body
> at any location that sees damping action created pressure, because then
> the oil would take the easy way out:
><snip>
> Rowdy
David Levy
You are all interesting and special.
Wes
> Jay C wrote:
> <snip>
> > a given gauge. Even easier would be to measure a freshly topped-off shock
> > (worst-case scenario is max pressure), take off the gauge, then measure it
> > again. The second measurement will probably be lower - how much lower is
>
> Your my hero Jay. That's exactly what i was going to suggest!
> Know your measurement error or skip the measuring altogether.
>
> I suggest the following procedure:
>
> - attach filling system
> - fill up to pressure indicated as "A"
<snip complexities>
Nah, pressurize the shop, depress valve stem until hissing stops,
release valve stem, depressurize shop.
That's how they do gas springs ... sorta.
You should be able to measure the pressure by the force exerted by the
shaft, knowing the diameter, but you'd need a foolproof way of
compensating for seal drag.
Wes
David Jones
<snip>
>You should be able to measure the pressure by the force exerted by the
>shaft, knowing the diameter, but you'd need a foolproof way of
>compensating for seal drag.
Seal Drag? Isn't that a hot sport in Nova Scotia, played with baseball
bats?
>Wes
David - '02 KTM200 EXC (virgin)
Jay C
>
> Nah, pressurize the shop, depress valve stem until hissing stops,
> release valve stem, depressurize shop.
That's how I do it. At least after eating at Taco Bell. Man, my wife HATES
that! ;)
Jay
Rowdy
<snip Rowdy's shocking world of physics>
> > Where am i wrong here?
>
> You left out the volume of oil the shaft displaces as the shock
> compresses. That's the flow of oil into the reservoir the compression
> clicker works against.
Darn, you too.
I'm just back from a shock swapping fest at buddy Drehwurms garage
(now i'm the proud owner of an Öhlins shock with 5.2 spring)
He said exactly the same thing. The only reason why oil _has_ to move
into the reservoir and back into the shock with _every_ compression
and expansion is the volume the shaft displaces when entering the
shock's previously oil filled chamber.
Totally closing the passage to the reservoir would practically lock
the shock solid (or bust the seals)
Okay, point taken as far as the to and fro pumping of oil
between shock and reservoir is concerned.
> Higher nitrogen pressure raises the compression force of the shock, in
> relation to pressure times area of the shaft. Pressure drop across the
> piston probably has a delta offset related to gas pressure as well,
> but I'm a little foggy on this part.
Hmm. So this miraculous self expansion of a shock w/o spring does
originate from the nitrogen trying to expand by shoving oil back
into the shock and this oil pushing out the shaft, gaining previously
occupied space?
Hence one should be able toss the nitrogen gauge and "measure" gas
pressure by measuring the selfexpansion force of a shock w/o spring
not?
Rowdy
Rowdy
<snip>
> The oil flow is equal to the volume of the rod entering the
> shock body. If it didn't, the shock would not be able to compress,
> since the compressible gas is located in the reservoir.
Damn, another one!
Thanks for bringing up the rod volume effect. I didn't take that into account.
> The presurized reservoir does act as a gas spring. The gas spring
> provides no damping, and therefore oil pressure will not affect damping
> characteristics.
Ahh! So you're joining me in claiming the gas pressure is rather irrelevant
for damping as long as it's high enough to prevent cavitation, right?
<snip>
> If you're still in doubt, tear your shock down. During the bleeding
> process, watch what happens to the oil level in the reservoir as you
> stroke the shock up and down. This is much easier to observe on a
> non-piggyback shock.
I think i'll do that anyhow. Yamaha doesn't sell the shock shaft as
a separate item, and the smallest "assembly" that includes said shaft
is the whole shock, Duh! At a measly 650 EUR (=580 bucks!!)
Bastards! I can get a brand new Öhlins for a little more.
Rowdy
Rowdy
<snip>
> oil is forced through the piston. If shaft speed increases enough,
> pressure above the piston increases eventually opening up flow through
> the compression adjuster to the reservoir.
Hu? That's a totally new concept to me. You seem to insinuate the existence
of a pressure actuated valve guarding the compression clicker, which, if
oil pressure on the compression side of the piston has reached a
certain level, would "open up" and enable flow through the compression
adjuster to begin.
You sure there is a pressure activated valve(!) at the clicker?
> speed/pressure-above-the-piston must increase enough to open the
> compression adjuster
I doubt that. I think the compression adjuster is just an orifice, that
can be adjusted, much like fuel mixture screw.
> and begin to collapse the reservoir bladder. If the reservoir
> bladder does not collapse - no flow.
I don't buy that. Does it take some additional event besides compression
pressure opening that strange compression adjuster's valve to make the
bladder collapse?
> Higher pressure in the bladder means higher resistance to
> collapse of the bladder which would translate
> into firmer compression damping.
You make bladder collapse sound like some event that suddenly happens,
after exceeding a threshold pressure value. Prove that.
> Hey, I know how we can verify this. Put water in the bladder.
> Let's do it to Mike W.'s shock?
Okay, great idea!
He'll totally forget to freak out over any sidehills
when riding with a bladder full with water.
Let's do it to his shock and our entertainment.
Rowdy
MX Tuner
wrote:
>David Levy wrote:
><snip Tuner sez: nitrogen pressure affects compression damping>
>> Got it. I stand before you enlightened!
>Well i don't, yet. Facts as i see them:
>- oil is incompressible, at our shock's pressures at least
Yup.
>- there is a nitrogen filled bladder in the reservoir
>- it exerts the high pressure onto the oil surrounding it
Yup.
>- this pressure shows up everywhere, hence prevents cavitation
> as far away from the bladder as "at the piston"
Yup.
>- the dampening action results from the piston forcing oil through
> well defined and clicker adjustable orifices within the shock body
Sort of. The damping comes from oil flowing through the shims at the
piston *and* the oil flowing through the compression adjuster (some
goes through the rebound circuit as well).
>- the compression damper clicker does not guard a flow of oil from shock
> body into reservoir during compression.
This may be where you're confused. It does restrict oil flow into the
reservoir. Think about this. The amount of oil that is transferred
into the reservoir is only the amount of oil that is displaced by the
volume of the shock shaft.
>- Otherwise compression damping would transfer oil into the reservoir,
> thereby compressing the nitrogen bladder and creating a high rate gas spring,
It does.
> not what a damper is meant to do
The reservoirs primary purpose (I think) is to prevent the oil from
cavitating. Just like leaving a Coke bottle capped (and yes, oil will
foam up a huge amount- more than you think). A side affect is it's
"push" against the oil traveling into the reservoir.
How's that sound, Jeff? Do you agree or am I way off base?
MX Tuner
DirtCrashr
>>shaft, knowing the diameter, but you'd need a foolproof way of
>>compensating for seal drag.
>Seal Drag? Isn't that a hot sport in Nova Scotia, played with baseball
>bats?
SUNDAY SUNDAY SUNDAY
140-NITRO BURNING HORSEPOWER BATS SMOKING THEIR TIRES OFF THE LINE WHEN THE
CHRISTMANS TREE LIGHTS UP SUNDAY SUNDAY SUNDAY
>>Wes
>
>
>David - '02 KTM200 EXC (virgin)
Madonna
'97 KTM 300 MXC, Diadora gear, Suomy Helmets
D36, BRC, CERA, COHVCO, CORVA.
Jeff Howe
Not only did I say what pressures I was seeing on my gauge, I also said I
can see what is happening inside the shock as a result. The fact that I see
this so often is why I shared it. It's not like I said this after observing
my very own personal shock one time. I was trying to give you all info here
that could be helpful based on personal experience. I've been checking
these thing for the last 2 years now, just for the hell of it. Like Tuner,
I never used to check them before opening them up, but since I was seeing
evidence of cavatation I started to check. I got the impression that with
the big blowout about my testing method being questionable that it was just
something you didn't want to hear, truth or not. Like I said, I have no
reason to lie about it, and had I felt what methods I used were totally
unreliable I wouldn't share this. Griping about a small gauge pressure loss
is nuts. If a specific shock cavitates at 135 psi and I'm reading 130 and I
have a 6psi loss, that 1psi is worthless. Your still way to close to the
border. Rowdy's assumption of the heated oil growing and creating more
pressure in the system is true...but it's minimal.
You just took my response as "touchy". The info is there for you to accept
how you want. You can either use it or discard it. Makes no difference to
me, though I would like this stuff to make you think twice about it. Thats
what it was for. 90 % of the NEW shocks *I* get in here ARE low on
pressure. Lower than what they claim they charge them too and low enough to
cavitate. That makes me think that most everybody else would see the same
thing if they bothered to check them. Now, we are NOT talking a significant
level of trashed shock here at 125psi, but it's enough that the shock is not
working at peak performance. What lots of guys don't realize is the dirty
oil they see is largely a result of this. When the bladder is rubbing the
reservoir wall it makes a mess of the oil, the more severe this is the more
crappy the oil will look and the closer you are to blowing a hole through
your bladder. You look in a reservoir of a shock that has been operating at
under 100 psi for any length of time and you will see what looks like a burn
mark on the wall. Nice black spot. Most of it is rubber and you literally
have to scrub it out with a Scotch-brite pad.
I will never claim to know everything, and I don't now. Anybody at that
point is full of crap.
Also, I did have a clue how much the gauge corrupted a pressure reading as I
stated previously it was an insignificant amount. I knew it was minimal.
This is not the first time I've checked shocks, recharged and checked again.
But, you guys wanted me to do it a bunch of times so I did and posted it.
Last year there was a thread at DRN concerning spring rate consistency, and
I went out that night and tested 3 brands of springs on my spring tester and
recorded the results in 1/2" increments. I never posted that info on the
net, but rather shared it with Jeremy Wilkey to make a point. Same kind of
deal... and again we could question the accuracy of my tester, but the fact
they were all done on the same tester lends a little credence to the
results. If you want to see that data send me a email, I think I still have
it.
Nobody is expected to take what I say as gospel, but I would like them to
know that I have no intention of supplying grossly misleading information
concerning anything with bikes and specifically my passion for suspension.
I will always speak from experience on this and not from dreamed up
assumptions. I can learn from anybody, whether it's right or wrong.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"Jay C" <jwc.N...@sysmatrix.net> wrote in message
news:3c9a365b$1...@news.vic.com...
Tim Harrell
>
>
> Hu? That's a totally new concept to me. You seem to insinuate the existence
> of a pressure actuated valve guarding the compression clicker, which, if
> oil pressure on the compression side of the piston has reached a
> certain level, would "open up" and enable flow through the compression
> adjuster to begin.
>
> You sure there is a pressure activated valve(!) at the clicker?
No, but the compression adjuster is more restrictive than the flow
through the piston at lower shock speeds. As piston speed increases, the
restriction of the compression adjuster causes the pressure "above the
piston" to increase more to sustain the same flow rate. Flow through an
orifice is dependent on the pressure differential across the orifice. A
higher bladder pressure would give a lower differential across the
compression valve for a given "above the piston" (ATP) pressure,
therefore allowing less flow through the valve for that ATP pressure.
Since there HAS to be flow into the reservoir for the shock to compress
(what do you think compensates for the volume of the shock shaft?), in
order for the flow rate through the comp adjuster to remain the same (to
allow the wheel to follow the ground over the same bump) there must be a
higher ATP pressure (i.e. more compression damping) to restore the
pressure differential across the comp valve.
Clear as mud to everybody?
>
> > speed/pressure-above-the-piston must increase enough to open the
> > compression adjuster
>
> I doubt that. I think the compression adjuster is just an orifice, that
> can be adjusted, much like fuel mixture screw.
You're right, but the pressure is a function of piston speed for a given
setting.
>
> > and begin to collapse the reservoir bladder. If the reservoir
> > bladder does not collapse - no flow.
>
> I don't buy that. Does it take some additional event besides compression
> pressure opening that strange compression adjuster's valve to make the
> bladder collapse?
Bladder collapses as a result of fluid volume entering the reservoir.
Some fluid HAS to transfer into the reservoir to compensate for the
shaft volume. Another volume, hopefully small I would think, will pant
back and forth responding to the pressure differential between the 2
cavities and the varying resistance to flow through the piston damping
orifices.
>
> > Higher pressure in the bladder means higher resistance to
> > collapse of the bladder which would translate
> > into firmer compression damping.
>
> You make bladder collapse sound like some event that suddenly happens,
> after exceeding a threshold pressure value. Prove that.
I'll diverge from David here, and stick to my differential pressure
across the compression valve theory.
>
>
> > Hey, I know how we can verify this. Put water in the bladder.
> > Let's do it to Mike W.'s shock?
>
> Okay, great idea!
> He'll totally forget to freak out over any sidehills
> when riding with a bladder full with water.
>
> Let's do it to his shock and our entertainment.
>
> Rowdy
We have to do it for Science.
Tim H.
Chris Buckley
topping of the nitrogen in the shocks on a quarterly basis. Now if I
could only find out how to take apart a Sachs shock.
Chris
Jeff Howe
.>
> The reservoirs primary purpose (I think) is to prevent the oil from
> cavitating. Just like leaving a Coke bottle capped (and yes, oil will
> foam up a huge amount- more than you think). A side affect is it's
> "push" against the oil traveling into the reservoir.
>
> How's that sound, Jeff? Do you agree or am I way off base?
>
> MX Tuner
>
The oil displaced by the shaft has to have a place to go first and foremost
or you blow the shock apart. The reservoir doesn't prevent cavitation the
pressure does. The oil is coming in no matter what the pressure. Don't
bother using pressure as a tuning variable. It can be but it's a waste of
time to make it a major player.
Everybody is flowing on this, kinda cool. The neat part now is going to be
watching the function of the adjuster. Cool topic.
Jeff Howe
Ohlins.
--
Best regards,
Jeffrey Howe
President
TrakControl Dynamics
Performance Suspension Services
www.trakcontrol.com
"Chris Buckley" <cnbu...@earthlink.net> wrote in message
news:3C9A82DB...@earthlink.net...
MX Tuner
<trakc...@netscape.net> wrote:
>> The reservoirs primary purpose (I think) is to prevent the oil from
>> cavitating. Just like leaving a Coke bottle capped (and yes, oil will
>> foam up a huge amount- more than you think). A side affect is it's
>> "push" against the oil traveling into the reservoir.
>> How's that sound, Jeff? Do you agree or am I way off base?
>> MX Tuner
>The oil displaced by the shaft has to have a place to go first and foremost
>or you blow the shock apart. The reservoir doesn't prevent cavitation the
>pressure does.
DOH!! That's what I meant. "Reservoir" meaning device that is
pressurizing the oil.
>The oil is coming in no matter what the pressure. Don't
>bother using pressure as a tuning variable. It can be but it's a waste of
>time to make it a major player.
I agree and I don't. But it does have an effect on the damping, albeit
small, and that was one of the debated points.
>Everybody is flowing on this, kinda cool. The neat part now is going to be
>watching the function of the adjuster. Cool topic.
Yup. Fun stuff.
Now, excuse me. I have to go work on a 1980 CR 250 (ugh!).
MX Tuner
Dudley Cornman
> David Levy wrote:
> >
> <snip Tuner sez: nitrogen pressure affects compression damping>
> >
> > Got it. I stand before you enlightened!
>
> Well i don't, yet. Facts as i see them:
>
> - oil is incompressible, at our shock's pressures at least
> - it exerts the high pressure onto the oil surrounding it
> as far away from the bladder as "at the piston"
> well defined and clicker adjustable orifices within the shock body
> "missing" in the shock's body, would only be possible in case of
cavitation.
> thereby compressing the nitrogen bladder and creating a high rate gas
spring,
> from the reservoir, except for the expanding of oil volume due to heat
> - the reservoir is just that: a reservoir whose main purpose is to
dissipate
> the heat and slow down the effect of changed viscosity from heating up
> the oil
> - hence the nitrogen pressure is irrelevant and has zero effect
> as long as it's high enough to prevent cavitation.
>
> - the only reason for all this reservoir thingies and pressurized nitrogen
> is to lessen the effect of the heating oil onto the dampening action, by
introducing a bigger casing surface (some even with heat dissipation
ribbing),
> more oil to store the heat and a high base pressure which prevents
cavitation.
>
I kinda see it your way...
Take a canister of oil... no air space and put a steel ball bearing in it.
Shake it up... feel how the bearing moves. Now add 200 pounds of pressure
and shake it again... can you feel any difference? I doubt it. I think the
effects are much the same on stacks and valves, etc. Unless pressurizing oil
makes it act like it is thicker, I don't see how it will change the damping.
:)
dsc
David Levy
Would concrete work?
Isn't 175 psi going to hurt?
"Wes" <wes...@arraycomm.com> wrote in message
news:af1d5a13.02032...@posting.google.com...
><snip>
David Levy
bladder would affect damping. As we say in the oilfield, "How do you want
it to work?"
I thought the shims in the piston would contribute most of the damping until
shaft speed increased to a set point that would open up flow to the
reservoir. You say it's simply an orifice. If so (and I don't doubt it)
then pressure in the bladder would make no difference. Is it correct to say
that both the shims and the "compression cartridge thingy" both contribute
to damping regardless of shaft speed?
Okay, you won me over. Pressure above the required pressure to prevent
cavitation has no effect on shock performance.
"Rowdy" <peter....@gmx.net> wrote in message
news:3C9A63DE...@gmx.net...
> David Levy wrote:
> <snip>
>
> Hu? That's a totally new concept to me. You seem to insinuate the
existence
> of a pressure actuated valve guarding the compression clicker, which, if
> oil pressure on the compression side of the piston has reached a
> certain level, would "open up" and enable flow through the compression
> adjuster to begin.
><snip>
>
>
> Rowdy
David Levy
and succumbing to his argument.
You splain things good. Thanks.
"Tim Harrell" <"don't e-mail me"@work> wrote in message
news:3C9A7ACD.4FD757EF@work...
><snip>
> No, but the compression adjuster is more restrictive than the flow
> through the piston at lower shock speeds. As piston speed increases, the
> restriction of the compression adjuster causes the pressure "above the
> piston" to increase more to sustain the same flow rate. Flow through an
> orifice is dependent on the pressure differential across the orifice. A
> higher bladder pressure would give a lower differential across the
> compression valve for a given "above the piston" (ATP) pressure,
> therefore allowing less flow through the valve for that ATP pressure.
> Since there HAS to be flow into the reservoir for the shock to compress
> (what do you think compensates for the volume of the shock shaft?), in
> order for the flow rate through the comp adjuster to remain the same (to
> allow the wheel to follow the ground over the same bump) there must be a
> higher ATP pressure (i.e. more compression damping) to restore the
> pressure differential across the comp valve.
> Clear as mud to everybody?
><snip>
> Tim H.
Rowdy
<snip>
> unreliable I wouldn't share this. Griping about a small gauge pressure loss
> is nuts. If a specific shock cavitates at 135 psi and I'm reading 130 and I
> have a 6psi loss, that 1psi is worthless. Your still way to close to the
Don't forget there are a lot of engineers on RMD with too much time on
their hands. These people are used to research into any measurement
errors, and only _after_ quantifying them, they'd agree with you on these
errors being irrelevant. Might sound picky, but is the only way to deal
with measurement errors. This way (thanks to your check measurements) we
all can rule out the possibility that the low reading you got "on 90%
of all new shocks" is a result of flawed measurement technique.
Nice to know one is getting numbers that mean a thing, not?
Now you can back up your diagnosis by proving that you even researched
the measurement error of yer gauge, isn't that a good thing?
> border. Rowdy's assumption of the heated oil growing and creating
> more pressure in the system is true...but it's minimal.
So what about the hotter oil displaying a different viscosity?
Damping increase a very small amount from the increased pressure
but decreases muuch more from the changed viscosity of hot oil, not?
> You just took my response as "touchy". The info is there for you to accept
Jay is touchy, too. Among engineers, people who do not assess quality of
their measurements and simply appear to believe any reading as if it were
a nature's constant loose credibility fast.
The two of you were a prefect example of two worlds clashing. And as usual
both of you were right, just not accustomed to the others procedures.
Shake hands now, guys.
<snip>
> was for. 90 % of the NEW shocks *I* get in here ARE low on pressure.
And thanks to your rechecking of the your measurement technique,
we now _know_ they were already low before measuring the pressure.
<snip>
> Also, I did have a clue how much the gauge corrupted a pressure reading as I
> stated previously it was an insignificant amount. I knew it was minimal.
With all due respect: you thought you knew.
Only _after_ measuring the measurement error it is valid to clam to "know it".
<snip spring rate>
> net, but rather shared it with Jeremy Wilkey to make a point. Same kind of
> deal... and again we could question the accuracy of my tester, but the fact
> they were all done on the same tester lends a little credence to the
> results.
Sorry again:
Exactly the fact that you used just one single tester _reduces_ the credence.
Checking the rates on a host of (different type) testers would have increased
the credence. (credence has nothing to do with accuracy, mind you)
> If you want to see that data send me a email, I think I still have it.
Of course! Pleas post it in ASCII format to RMD, if possible.
I've had a 5.8 Eibach Spring on my stock WR-F shock, which surely didn't
feel like 5.8, sag wise. The 5.2 on my new (2nd hand) Öhlins however feels
much more like i'd hipshootingly expect a 5.2 to behave.
> Nobody is expected to take what I say as gospel, but I would like them to
> know that I have no intention of supplying grossly misleading information
Believe it or not: Most of us don't have that intention,
but as you've seen from my earlier post i just didn't know better.
> I can learn from anybody, whether it's right or wrong.
Sounds like Tuner to me. He likes to study idiots' responses, too,
especially in the premix and jetting dept. :-)
thanks for staying
Rowdy
Jeff Howe
> David Levy wrote:
> <snip>
> > oil is forced through the piston. If shaft speed increases enough,
> > pressure above the piston increases eventually opening up flow through
> > the compression adjuster to the reservoir.
>
> Hu? That's a totally new concept to me. You seem to insinuate the
existence
> of a pressure actuated valve guarding the compression clicker, which, if
> oil pressure on the compression side of the piston has reached a
> certain level, would "open up" and enable flow through the compression
> adjuster to begin.
>
> You sure there is a pressure activated valve(!) at the clicker?
Yes, there is one in every adjuster.
>
> > speed/pressure-above-the-piston must increase enough to open the
> > compression adjuster
>
> I doubt that. I think the compression adjuster is just an orifice, that
> can be adjusted, much like fuel mixture screw.
There is a low speed orifice/needle adjuster and a high speed compression
shim stack. When the LS adjustable orifice has seen sufficient fluid
velocity to hydraulice, the force is then working against the HS shim stack.
Late model LS/HS adjusters feature a spring that puts pressure on this
internal shim stack. So to understand how to get the most from your
adjuster circuit realize that LS affects HS but not vice versa.
If it were just an orifice and you closed it off totally you would not be
able to displace fluid to the reservoir and shock would be coming apart.
I'm not sure if somebody already covered this here but.... I'll try to get
pictures up sometime of these things.
Something cool on this topic, in shop now I have a 87 KX shock...and I
beleive these were first to feature a LS/HS adjustable shock tuning
adjuster. Hopefully I can get pictures of it.
Rowdy
<snip>
> When the bladder is rubbing the reservoir wall it makes a mess of the oil,
> the more severe this is the more crappy the oil will look and the closer
> you are to blowing a hole through your bladder.
> You look in a reservoir of a shock that has been operating at under
> 100 psi for any length of time and you will see what looks like a burn
> mark on the wall.
Buddy i got my Öhlins from yesterday mentioned Öhlins would not be using
a bladder design but a kind of piston between nitrogen and reservoir oil.
After reading all your shocking reports about decaying bladders,
this piston setup seems to be a superior design, not?
(assuming they found a way to make sure the piston seal is more or less
maintenance free, that is)
Rowdy
Jay C
> Late model LS/HS adjusters feature a spring that puts pressure on this
> internal shim stack.
Is the pressure on that spring the thing that gets adjusted with a HS shock
adjusting clicker? I always wondered how the HS clickers worked.
Jay
Jay C
> The reservoir doesn't prevent cavitation the
> pressure does.
While the pressure thing all makes sense, the thing that confuses me is the
use of the cavitation term. Also, Tuner's statement about shock oil
foaming. I don't see how these things can happen - well, at least the
foaming part. In a typical fork (not the works bladder-type), yes. I
suppose cavitation can occur, with the spaces that have no oil in them being
a vacuum. But foaming? There is no gas in the system available to fill
foam bubbles. The only gas available is isolated by the bladder - which is
there specifically to eliminate air from the system so foam and gas-filled
cavitation can't occur, from what I understand. Assuming foaming does, in
fact, occur in a shock, where does the gas in the bubbles come from?
Jay
Brewster
piston movement, remove the spring and try to compress the shock with
recommended pressue in the bladder. If you do this on a scale and measure
the resistance verses distance traveled, you could determine the amount of
effect the pressure has.
Just a thought.
Brewster
Jeff Deeney
: Isn't 175 psi going to hurt?
No. It's the depresurizing that hurts. Ingest a sufficient quantity of
anti-foaming agents to prevent the bends.
-Jeffrey Deeney- DoD#0498 NCTR UTMA BRC COHVCO AMA
'99 ATK 260LQ-Stink Wheels '94 XR650L-DreamSickle
We don't stop riding because we get old, we get old because we stop riding.
Jeff Deeney
: Jay is touchy, too. Among engineers, people who do not assess quality of
: their measurements and simply appear to believe any reading as if it were
: a nature's constant loose credibility fast.
No, you're confusing lack of interpersonal skills with being touchy.
This is typical for engineers. I speak from personal experience.
Anyone who disagrees is a wanker.
Jeff Deeney
: I agree and I don't. But it does have an effect on the damping, albeit
: small, and that was one of the debated points.
As a licensed mechanical engineer, I'm going to have to disagree on this
point. Oil is essentially incompressible. The effect of 175psi on
viscosity is almost immeasurable, and certainly undetectible while
riding. The only effect on damping would be due to cavitation at lack
of pressure.
Jay C
> So what about the hotter oil displaying a different viscosity?
> Damping increase a very small amount from the increased pressure
> but decreases muuch more from the changed viscosity of hot oil, not?
JFTR, increased temperature will have a huge effect on system pressure. Not
from expansion of the oil (I would assume that effect to be negligable) but
from the increased temperature of the gas. The nitrogen will increase in
temperature as much as the oil and will increase internal pressures
significantly. I would expect a shock pressure to increase from 150PSI cold
to easily over 200PSI at working temperatures. dP/dT = 1, after all.
Luckily, we measure temperature change in Kelvin, or we'd all be dead by now
;).
> Jay is touchy, too.
And proud of it. I'm hopelessly anal-retentive too.
> Among engineers, people who do not assess quality of
> their measurements and simply appear to believe any reading as if it were
> a nature's constant loose credibility fast.
Word.
> Shake hands now, guys.
Come on now, Rowdy. I'm not at odds with Jeff - I'm just still pumping him
for information. This is fascinating stuff to me... he just seems to take
the questioning of his statements as a personal assault.
And Jeff - assuming you're still following this - I have absolutely no
intention of dissing you in any way. As I tried to explain yesterday
(albeit unsuccessfully, evidently), don't take my questioning of your
techniques as calling you incompetent in any way, please. You need not take
a defensive posture. I was just trying to clarify your statements and
understand your techniques, for the benefit of myself and any others who
might also be interested. I also thought you might see the benefit of
quantification and clarification of your own techniques too.
Sorry for the misunderstanding.
Jay
Jay C
> Buddy i got my Öhlins from yesterday mentioned Öhlins would not be using
> a bladder design but a kind of piston between nitrogen and reservoir oil.
>
> After reading all your shocking reports about decaying bladders,
> this piston setup seems to be a superior design, not?
Actually, the hot setup is to replace the piston with an after-market
bladder. The reciprocating mass of the piston adversely affects shock
action, evidently.
Jay
Jay C
: Jay is touchy, too. Among engineers, people who do not assess quality of
>
> This is typical for engineers. I speak from personal experience.
> Anyone who disagrees is a wanker.
Screw you. I have great interpersonal skills. Eat shit and die.
Jay
Peter Renner
>
> MX Tuner (mxt...@mindspring.com) wrote:
>
> : I agree and I don't. But it does have an effect on the damping, albeit
> : small, and that was one of the debated points.
<snip licensed to disagree>
> The only effect on damping would be due to cavitation at lack of pressure.
As a licensed mechanical hipshooter, I'm going to have to disagree on this and
have to agree with Tuner, at least from a theoretical (e.g. might be irrelevant
for my kind of riding :) point of view.
Shaft displaces oil in shock body and forces oil into reservoir.
The oil has to enter the reservoir no matter what or the shock would bust
(or the shaft would stop moving upward)
This oil enters said reservoir the easier the lower the pressure there is.
("Proof" by border analysis:
compare compression damping at the following assumed nitrogen pressures:
1 psi, 100 psi, 100k psi, 10^10 psi, infinite psi = no nitrogen at all)
Rowdy
john
ever use a pressure cooker?
cavitations is boiling of fluid where it touches
the surface (where cavitations occurs)
if you can figure out how to eliminate it
the navy would like to talk to you
john
"Jay C" <jwc.N...@sysmatrix.net> wrote in message
news:3c9b5928$1...@news.vic.com...
Rowdy
>
> Rowdy (peter....@gmx.net) wrote:
>
> : Jay is touchy, too. Among engineers, people who do not assess quality of
> : their measurements and simply appear to believe any reading as if it were
> : a nature's constant loose credibility fast.
>
> No, you're confusing lack of interpersonal skills with being touchy.
> This is typical for engineers. I speak from personal experience.
> Anyone who disagrees is a wanker.
eh? you talking to me?
you have a problem you want to talk about? let's go outside!
interpersonal what? Never had on of these.
But i'm right with assessing measurement errors being a prerequisite
for a credible measurement, not?
Rowdy
David Levy
>
> No, you're confusing lack of interpersonal skills with being touchy.
> This is typical for engineers.
Agree. Engineers are trained to not have social skills. Social skills are
highly overated. Knowledge is thrilling.
>I speak from personal experience.
> Anyone who disagrees is a wanker.
Disagree.
David Levy
IRKurt
1. Caveatation creates enormous vaccuum/pressure.
2. That the bladder is little more than a displacement tool, its job to flex
(not collapse) preventing a huge sucking sound through the seals.
3. There is a threshold pressure for collapse/not collapse. + / - 6 psi is a
non-factor in a bare-ass minimum scenario.
4. As far as adjusment goes, it's theoretically possible via the pressureized
bladder, but the adjustments can be made a lot more easily and accurately
through dampening adjustments - elsewhere in the system we call shock.
How am I doing?
Kurt
Big Picture Note to Engineers: -- to prevent crashing into planets please
verify imperial versus metric measurements.
IRKurt
writes:
>("Proof" by border analysis:
> compare compression damping at the following assumed nitrogen pressures:
> 1 psi, 100 psi, 100k psi, 10^10 psi, infinite psi = no nitrogen at all)
>
>
>
>Rowdy
Perhaps because the number (presssure) more represents a threshold, not a
linear scale?
Kurt
IRKurt
<dl...@pobox.com> writes:
>> No, you're confusing lack of interpersonal skills with being touchy.
>> This is typical for engineers.
>
>Agree. Engineers are trained to not have social skills. Social skills are
>highly overated. Knowledge is thrilling.
That's why we don't let you guys outside, much.
Can I pick something up for you from McDonald's for lunch? They are offering
Big Macs for 38.6% off regular price. By volume you could eat....
Kurt
Jay C
> jay see
> ever use a pressure cooker?
> cavitations is boiling of fluid where it touches
> the surface (where cavitations occurs)
> if you can figure out how to eliminate it
> the navy would like to talk to you
Wha?? Evidently not even close. However, as one to learn something new
every day, I can announce that I answered my own previous question while
looking up the word for your benefit (and my amusement). I thought that
cavitation occured when the liquid was driven fast enough to pull away from
itself. I was right...however, the cavitiation of oil in a shock only made
sense to me if the liquid-free spaces were vacuums. Well, raise-my-rent...
creating vacuums is, by definition, what cavitiation is all about. Pisser.
Main Entry: cav·i·ta·tion
Pronunciation: "ka-v&-'tA-sh&n
Function: noun
Etymology: cavity + -ation
Date: 1895
: the process of cavitating : as a : the formation of partial vacuums in a
liquid by a swiftly moving solid body (as a propeller) or by high-intensity
sound waves; also : the pitting and wearing away of solid surfaces (as of
metal or concrete) as a result of the collapse of these vacuums in
surrounding liquid b : the formation of cavities in an organ or tissue
especially in disease
Jay
john
anonymous Marine Scout-Sniper
"IRKurt"
john
cavitations can also happen with lasers
http://www.physik3.gwdg.de/~ohl/SONO_ASI/node1.html
if your into that stuff
i only care if my prop is about to be roasted
or my teeth need drilled & filled.
john
glad to add to the nuances of English language
amusements park rides for you
i swear my brain ain't wired for English
"Jay C" <jwc.
> "john" <ż