Mechanical Efficiency

[cycl...@gmail.com]

I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

[Martin Borsje]

cycl...@gmail.com expressed precisely :

You start here comparing the efficiency of the transmission (chain or
hydraulic pmp/motor/tubing combination) with that of the drive
(e-motor).

Something with apples and pears. Please be more clear on this.

[Frank Krygowski]

As Martin says, the electric motor is the answer to "One of these things
is not like the others..."

But electric motors vary widely in efficiency. The trend, very
logically, is that big ones are made more efficient than tiny ones. My
guess (TM) would be approaching 95% for really huge ones, down to 70%
for tiny shaded pole motors driving timers, clocks, etc. I'd expect a
motor as used in a motorized bike to be around 80% efficient.

Roller chains are very efficient. Over 90% is not at all unusual, and
they can get into the high 90s under the right conditions.

Hydraulic drives typically consist of a pump, valves, hoses and a
hydraulic motor. This site gives roughly 85% for a fairly simple pump:
http://machinerylubrication.com/Read/28430/hydraulic-pump-motors-maintenance
A hydraulic motor of similar technology would be similar. And you'd
have losses in valves and piping. You'd need to compound all those
efficiencies to get the total. I'd guess overall efficiency of less than
70%.

--
- Frank Krygowski

[DougC]

Hydraulic wheel drive can work okay at low RPMs and where loss of drive
precision isn't important, but the fluid turbulence prevents them from
being much use at higher RPMs. ("higher" being, as fast as bicycle
wheels or car wheels typically turn)

Tall-wheel self-propelled crop sprayers have a hydraulic pump on the
transmission and hydraulic motors at the wheels:
https://www.youtube.com/watch?v=cvDVcFCp5fU
The ones for spraying corn (maize in Euro-land) are tall enough that you
can walk around underneath them without bending over. They are driven
across corn fields with the tires straddling between the planted rows.

[AMuzi]

On 4/19/2017 2:10 PM, cycl...@gmail.com wrote:

I do not know but it sounds dauntingly complex.

One added factor is that a new chain drive is very efficient
but wear brings a lot of friction=heat loss. There's plenty
of data on that subject.

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

[bob prohaska]

Ok, I'll bite 8-)

cycl...@gmail.com wrote:
> I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.
>
> Can anyone here compare the efficiency of:
>
> A very long chain drive as used in a recumbent

Low-to-mid 90's %, assuming good alignment and lubriction.
Aluminum chain links seem like a good idea.

> A hydraulic drive system and

Don't know, but hydrostatic drives tend to have seal friction
losses and hydrodynamic drives operate at higher speeds than
cyclists pedal.

> A electric motor
>

How heavy do you want to make it? Power transfer is maximum at
50% efficiency, to make it more efficient the components must be
given higher power capacity, i.e., bigger. That's why bottle
dynamos are around 50% efficiency.

> And perhaps there's something I missed?

On a bicycle the biggest issue seems to be weight. An aluminum
or titanium chain drive is probably the best match to requirements.

Putting on my Nomex suit...........

bob prohaska

[John B Slocomb]

I can't quantify it but I've known a number of people that had a
hydraulic drive in a sailing yacht. Every one hated it. I remember a
guy had sailed from Australia to Singapore and when I met him he was
industrially re-engining his 35 ft. boat to use a direct drive
(propeller shaft and gear box).

Due to hull design and shape installing an auxiliary motor is
difficult in some sail boats and a hydraulic pump on the engine and a
hydraulic motor driving the prop seems like a good idea. Until one
tries it. On the other hand an electrical drive seems to work great.
At least on a boat :-)

It might be considered that a chain drive probably has the lowest
losses of any drive system :-)

[cycl...@gmail.com]

Thanks for everyone's input. While going through all of the literature I got the idea that with electric or hydraulic you couldn't really expect much more than a total of 60% at best but I wanted to make sure.

High speed recumbents have the problem of not being able to get high enough gears and end up having multiple large and small wheels to get pure wheel speed. The best I saw was an internally geared wheel that gave a 1:4 ratio but you can't buy those sorts of components and would have to build them yourself.

Straight cut gears are the most efficient losing only around 2-3%, chain drives in perfect condition are something like 90% but rapidly lose that unless fully enclosed and often serviced.

[AMuzi]

But you already have a meat engine as cargo so any
additional energy source (electric) will increase total mass
and any degradation of efficiency in transfer (hydraulic)
will waste energy.

[Jeff Liebermann]

On Wed, 19 Apr 2017 12:10:33 -0700 (PDT), cycl...@gmail.com wrote:

>I have been looking all over the Internet to find comparisons of
>mechanical efficiency and haven't found anything that isn't
>covered in different units of measure that require multiple
>iterations of conversions.

<https://en.wikipedia.org/wiki/Bicycle_drivetrain_systems>

I also couldn't find anything that is instantly useful. There's
probably a reason why nobody has made such a general study. My
guess(tm) is it's because it wouldn't apply to most useful situations,
power levels, rotational speeds, and other design limitations. A
realistic comparison would include a range of acceptable power
transmission levels, weight limits, and possibly some operational
considerations. On a bicycle, the book
"Bicycling Science"
by David Gordon Wilson
2nd and 3rd editions (they're somewhat different)
<http://www.alibris.com/Bicycling-Science-David-Gordon-Wilson/book/17828968>
<https://books.google.com/books?id=0JJo6DlF9iMC>
is a good reference of work for such surveys. The section on power
transmission includes Berg cable drives, toothed belt drives, drive
shafts, etc.

>Can anyone here compare the efficiency of:
>
>A very long chain drive as used in a recumbent

Might be something in here:
<http://www.cyclingpowerlab.com/drivetrainefficiency.aspx>
<http://www.bikeradar.com/us/news/article/friction-facts-measuring-drivetrain-efficiency-35694/>

>A hydraulic drive system and

The weight penalty of dragging a plumbing nightmare around might make
this a losing proposition even if it were 100% efficient.

>A electric motor

I'm going to assume you're only interested in a human powered
transmition, not building a battery or wind powered bicycle or hybrid.

An electric generator and motor transmission is the mostly the product
of the generator and motor efficiencies, going from kinetic energy to
electric energy and then back to kinetic. A small (1-2HP) permanent
magnet electric generator is probably about 75% efficient while a
similar sized motor is about 70%. There are power/rpm curves for both
that can be used to determine the most efficient operating point, or
the efficiency at some particular power and RPM level. Using my
guess(tm) numbers, that's:
0.75 * 0.70 = 53% efficiency.
In other words, an all electric drive system sucks. On Pg 337 of the
"Bicycling Science" book, the author does a better job of estimating
the electrical system efficiency. He has the following in series:
70% - Pedals driving gears with short chain to generator.
98% - Generator
95% - Controller
80% - Motor driving short chain to wheel
Multiplying these together yields 52% efficiency.

There's also a short section on hydrostatic drives (as in earth
movers), which the author claims maxes out at 80% efficiency and is
therefor useless.

>And perhaps there's something I missed?

Well, I would suggest you disclose what you are trying to accomplish
so that I don't need to guess(tm) so much. You also missed other
transmission systems:
1. Perforated metal tape instead of a chain
2. Cable (Snek) drive
3. Berg cable and plastic chain:
<http://802.11junk.com/jeffl/pics/Berg/>
4. Toothed rubber belt
5. Direct gear drive using lots of spur gears.
6. Drive Shaft
7. Direct drive (Penny Farthing)
8. Ratchet drive
9. Various eccentric gear drives (elliptical crank, reciprocating
pedals, rolling exercise machines, etc).
<http://www.elliptigo.com>
<https://www.streetstrider.com>
10. Rowing motion drive
<https://rowingbike.com>
11. Front wheel pedal drive with hub transmission.
12. Whatever else I forgot.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[cycl...@gmail.com]

I had started this because in a recumbent the chain run is so long that it can't possibly be very efficient. So I then considered a drive shaft. This sounds OK by itself until you start considering the length of the drive shaft and that it would be made so lightly that it would require many bearings along it to prevent flexing.

Then looking at one of the land speed record streamliners they have machined a front wheel drive system. But then you have to design a system that allows the pedals to remain in the same plane as the legs and turn to accomodate the steering. This loses a great deal officiency as well.

Also with streamliners the speeds are so great that you have to make absolutely phenomenally large gearing.

As you could see in that youtube video of the German riding to work the actual average speed of an unsuspended bike also isn't very great. The rough ride slows the bike greatly because the rider cannot retain an efficient peddaling position.

Then I considered hydraulics. In fact this probably weighs very little more than either the long chain with the double gearing system or the front drive system with the machined hub containing a 1:4 gearing.

After all - the disk braking system weighs in only slightly more than standard rim brakes including the disk most of which are steel.

But the efficiency is the problem. For the speed you absolutely must have as little loss as possible.

Electric drives are readily available but the weakness and the loss of efficiency is through the generator and the speed multiplication systems.

So I'm still in the design state of the drive system before even worrying about the shell. I can see that the aerodynamics of the present generation of streamliner can be easily improved. Apparently they are doing their testing in very low speed wind tunnels and are relating that to the higher speeds.

And the weight of the entire streamliners are WAY out of hand. While aerodynamic drag is important over about 30 mph, you have to get up to the speed before good aerodynamics is significant. And you can burn up all of your energy getting there with the weights I'm seeing. That is the main reason they appear to accelerate so slowly and not because of faulty gearing.

[Frank Krygowski]

On 4/21/2017 11:08 AM, cycl...@gmail.com wrote:
>
>
> I had started this because in a recumbent the chain run is so long that it can't possibly be very efficient.

I don't know of any reason that a long chain should be much less
efficient than a short one.

Chain inefficiencies (small as they are) come from the friction as the
links bend around sprockets, and friction as rollers roll on and off
sprocket teeth. Some of the bending friction is between side plates
exacerbated by lateral angles, and long chain runs tend to have smaller
lateral angles. They may be more efficient than short chains.

--
- Frank Krygowski

[Jeff Liebermann]

On Fri, 21 Apr 2017 08:08:06 -0700 (PDT), cycl...@gmail.com wrote:

>I had started this because in a recumbent the chain run is so long that
>it can't possibly be very efficient.

I beg to differ. Long chains are more efficient than short chains.

The loss of efficiency in a chain drive is mostly from the friction
losses when the chain link pin is rotated inside the sleeve. Only the
upper part of the chain loop is under tension. Only the links that are
rotating from the straight line chain, to the crank and the freewheel
have pins that are rotating and therefore add friction. In other
words, for large diameter gears, only two links on the entire chain
have rotating pins. For smaller diameters and tighter bends, perhaps
2 more pins.

In addition, the tension on the chain is distributed only over the
upper part of the chain loop. For example, if you a pulling with 100
lbs of tension on the upper part of the chain loop, and there are 10
links (and 20 pins) in the upper part of the chain loop, then the
pressure per pin is:
100 lbs / 20 pins = 5 lbs/pin
However, if you use a much longer chain, as in a recumbent, with 50
links (100 pins) between the two gears, the tension per pin is:
100 lbs / 100 pins = 1 lbs/pin
Since frictional losses increase with surface pressure, the longer
chain would have LESS friction than the shorter chain because there is
less pressure on the pins and sleeves. Of course, a longer chain
would weigh more, but that's another calculation and is not directly
involved in the efficiency calculation.

[cycl...@gmail.com]

Long chains have several guide pulleys along their length and each one of those pulleys absorb about a watt each.

[DougC]

Welp,,,, I would presume that a longer chain would tend to require more
idlers to route a circuitous path than a short one would.

Using plain bicycle chain still tends to win out most of the time tho.
It's just easier and cheaper to use than anything else. Home-builders
can make sprockets any size you want with just a drill press and any 2-D
CAD program. Any of that other stuff is way more complicated to try to
fabricate.

I have pondered the same problem too however: with a conventional
bicycle drive train, even with triple chainrings you run into the
problem of not having enough width in the drive ratios... You want to be
able to crawl in a granny gear when you need to, but you still want to
be able to pedal at a comfortable cadence at 35 - 40+ MPH.
,,,,,,,
I know how most do it: they just use a normal 2x9+ setup with the widest
ranges they can get, and they sacrifice the low end for a bit higher
end. Some bikes also use compound gearing, with a second rear hub +
derailler after the first, but that gets messy fast.

And none of these is still really convenient to use, in that they do not
place the ratios in a mathematical order. Ideally you would want a
couple of button-levers marked [shift up] and [shift down], and it would
go through all the ratios in order, from one end to the other. With an
automatic car transmission for example, it shifts 1-2-3-4-5
automatically when accellerating. You don't need to TELL it what gear to
use.....

I've seen this same question asked about Di2 setups: why is there still
two levers? Since a microprocessor could easily figure out the
next-highest gear or next-lowest gear, and switch the front & rear
deraillers to reach it. You should just need ONE lever, or two
buttons.... But this only seems to be stubborn tradition; riders are
used to mentally managing the front and rear deraillers separately. So
that was the way Shimano decided to control it.

[cycl...@gmail.com]

Huh? These long chains do not have straight runs and in fact near the back have a rather shorter run to the cogs which always puts them in more of a sharper angle to the cogset. In other words - you are always in a more "cross-chained" angle.

[Doug Landau]

So you are saying that losses from routing the lower run of the chain through tensioners and idlers are negligible?

[Frank Krygowski]

On 4/21/2017 1:12 PM, Jeff Liebermann wrote:
> On Fri, 21 Apr 2017 08:08:06 -0700 (PDT), cycl...@gmail.com wrote:
>
>> I had started this because in a recumbent the chain run is so long that
>> it can't possibly be very efficient.
>
> I beg to differ. Long chains are more efficient than short chains.
>
> The loss of efficiency in a chain drive is mostly from the friction
> losses when the chain link pin is rotated inside the sleeve. Only the
> upper part of the chain loop is under tension. Only the links that are
> rotating from the straight line chain, to the crank and the freewheel
> have pins that are rotating and therefore add friction. In other
> words, for large diameter gears, only two links on the entire chain
> have rotating pins. For smaller diameters and tighter bends, perhaps
> 2 more pins.
>
> In addition, the tension on the chain is distributed only over the
> upper part of the chain loop. For example, if you a pulling with 100
> lbs of tension on the upper part of the chain loop, and there are 10
> links (and 20 pins) in the upper part of the chain loop, then the
> pressure per pin is:
> 100 lbs / 20 pins = 5 lbs/pin
> However, if you use a much longer chain, as in a recumbent, with 50
> links (100 pins) between the two gears, the tension per pin is:
> 100 lbs / 100 pins = 1 lbs/pin

Not true, Jeff. The tension in the chain is a constant The load on
each pin in the free upper span is exactly the same, and it doesn't
change if the chain is longer, i.e. has more pins. A normal chain with
a 100 pound load has 100 pounds on each pin, no matter how long.

Now if you had two chains side by side sharing the same 100 pound load,
those pins would each have 50 pounds on them.

To use an electrical analogy, you're confusing a series situation with a
parallel situation.

--
- Frank Krygowski

[Jeff Liebermann]

Argh. We went through this exercise a few years ago in this newsgroup
when I allegedly made the same mistake. Am I wrong again? (I just
hate it when that happens).

The way I look at it is that if I replace each link in the upper part
of the chain loop with a spring scale, methinks the deflection of each
spring (a measure of the force) would be the pulling load divided by
number of spring scales.

Or, if we break the chain and put one spring scale between two
adjacent links, the measured force will be equal to the applied load.
However, if we break the chain in two places, methinks the measured
force will be half the applied load. If the force were equal to the
applied load on each link, I would expect the two spring scales to
also indicate a force equal to the applied load, which I don't believe
is the case.

>Now if you had two chains side by side sharing the same 100 pound load,
>those pins would each have 50 pounds on them.

Yep, here we agree.

>To use an electrical analogy, you're confusing a series situation with a
>parallel situation.

The electrical analogy would be each link in the chain is a resistor.
The applied load is the voltage. If the resistors are all equal, the
voltage across each resistor would be equal to the applied voltage
divided by the number of resistors.

I'll admit that I might be wrong about all this, but at this moment,
it seems correct to me.

[Jeff Liebermann]

On Fri, 21 Apr 2017 10:40:30 -0700 (PDT), Doug Landau
<doug....@gmail.com> wrote:

>So you are saying that losses from routing the lower run of
>the chain through tensioners and idlers are negligible?

Worse. I was ignoring the losses from tensioners, idlers, grease, pin
rotation caused by a slight chain droop, inertial loading from a
longer and thus heavier chain, chain acceleration lag, etc. I assumed
that the original question was about a simple power transmission
system, not the complex mess that such systems inevitably evolve into.
Something more like this test fixture and a practical bicycle:
<http://cdn.mos.bikeradar.imdserve.com/images/news/2012/11/06/1352163122826-1476emv18vmdi-630-80.jpg>
The additional losses can be tested separately and included later.

You're correct that tensioners, idlers, etc are important. For a
chain drive that is about 95% efficient, small frictional losses might
reduce the 95% efficiency rather significantly. However, I don't
believe we were trying to nail down a single number for a chain drive
efficiency. As noted in the "Bicycling Science" books, the efficiency
will vary somewhat depending on speed, conditions, maintenance,
gearing, etc. What I believe was of interest was comparing the
efficiencies of a drive chain, hydraulic drive, and an electric
generator-motor drive. From my readings, these will show drastically
different efficiencies, where the effects of tensioners, idlers, etc
will not make much difference in the comparison.

[Jeff Liebermann]

On Fri, 21 Apr 2017 10:18:17 -0700 (PDT), cycl...@gmail.com wrote:

>Huh? These long chains do not have straight runs and in fact near the
>back have a rather shorter run to the cogs which always puts them in
>more of a sharper angle to the cogset. In other words - you are
>always in a more "cross-chained" angle.

There are chain designs which help in such arrangements. This one
seems popular:
<http://kmcchain.us/chain/x9-93/>
<http://t-cycle.com/chain-in-bulk-c-116/bulk-kmc-x993-chain-by-foot-p-35.html>

However, if you're looking for the source of chain drag and friction,
just look at what wears on an old chain. It's not the inner or outer
plates, which is what allegedly wears with "bent" chain line. It's
the pin and sleeve that show most of the wear and presumably is the
source of most of the friction. I say presumably because there are
differences in surface hardness, lubrication, cleanliness, etc which
affect wear.

[Frank Krygowski]

On 4/21/2017 11:13 PM, Jeff Liebermann wrote:

> On Fri, 21 Apr 2017 20:03:26 -0400, Frank Krygowski wrote:
>
>> Not true, Jeff. The tension in the chain is a constant The load on
>> each pin in the free upper span is exactly the same, and it doesn't
>> change if the chain is longer, i.e. has more pins. A normal chain with
>> a 100 pound load has 100 pounds on each pin, no matter how long.
>
> Argh. We went through this exercise a few years ago in this newsgroup
> when I allegedly made the same mistake. Am I wrong again? (I just
> hate it when that happens).

Well yes, you're wrong. I don't remember the previous discussion, so I
can't comment on the "again" part.

>
> The way I look at it is that if I replace each link in the upper part
> of the chain loop with a spring scale, methinks the deflection of each
> spring (a measure of the force) would be the pulling load divided by
> number of spring scales.

Nope. Each spring scale would measure the same. If you have two spring
scales at home, you can easily verify this.

> Or, if we break the chain and put one spring scale between two
> adjacent links, the measured force will be equal to the applied load.
> However, if we break the chain in two places, methinks the measured
> force will be half the applied load. If the force were equal to the
> applied load on each link, I would expect the two spring scales to
> also indicate a force equal to the applied load, which I don't believe
> is the case.

I'll try a couple other explanations.

First, you can find tables of tensile strength for various sizes of
roller chain. You'll note that the tables don't specify length. That
tensile strength depends on several factors, but not length. If what
you're visualizing were true, they'd have to specify length.

Second, if what you visualize were true, let's take a chain with an
ultimate strength of (say) 5000 pounds. Would that apply to one link
(say, 1/2")? If so, would two links (say, 1") be able to hold 10,000
pounds? Would 10 inches of chain be able to hold 100,000 pounds? Would
100" of chain hold a million pounds? You see that it quickly becomes
absurd.

Under static and otherwise ordinary and reasonable conditions, the
length doesn't matter. Tension in a chain is constant over its length.
Same is true for ropes, cables, etc.


--
- Frank Krygowski

[cycl...@gmail.com]

I read and article that tested chains and new they were all equal. But the KMC wore more rapidly and the friction went up faster. Though with the price difference you could buy three KMC chains for one Campy.

[Jeff Liebermann]

On Sat, 22 Apr 2017 00:23:48 -0400, Frank Krygowski
<frkr...@sbcglobal.net> wrote:

>Nope. Each spring scale would measure the same. If you have two spring
>scales at home, you can easily verify this.

I just took several springs and measured the deflections. You're
right which means my explanation is wrong. The last time we had a
similar discussion on bicycle chains, I made the same mistake.
Something is fundamentally wrong with my reasoning. Argh.

>First, you can find tables of tensile strength for various sizes of
>roller chain. You'll note that the tables don't specify length. That
>tensile strength depends on several factors, but not length. If what
>you're visualizing were true, they'd have to specify length.
>
>Second, if what you visualize were true, let's take a chain with an
>ultimate strength of (say) 5000 pounds. Would that apply to one link
>(say, 1/2")? If so, would two links (say, 1") be able to hold 10,000
>pounds? Would 10 inches of chain be able to hold 100,000 pounds? Would
>100" of chain hold a million pounds? You see that it quickly becomes
>absurd.

Good point and I see the problem.

>Under static and otherwise ordinary and reasonable conditions, the
>length doesn't matter. Tension in a chain is constant over its length.
>Same is true for ropes, cables, etc.

Thanks. I'll try not to screw it up again.

My usual off topic Drivel:
How to mount headlights on a front rack:
<http://www.cycleexif.com/alex-singer-randonneur>
Wide headlight pattern using incandescent lights:
<http://www.bicicletasantigas.com.br/arquivos/portal/galeria/pp118.htm>

[Sir Ridesalot]

On Saturday, April 22, 2017 at 11:14:25 PM UTC-4, Jeff Liebermann wrote:
Snipped

> My usual off topic Drivel:
> How to mount headlights on a front rack:
> <http://www.cycleexif.com/alex-singer-randonneur>

Oh man does that bring back memories. I remember front racks that had an integral clamp to hold your flashlight.

Battery powered lights and their mounts sure have come a long ways.

Cheers

[Jeff Liebermann]

On Sat, 22 Apr 2017 21:08:03 -0700 (PDT), Sir Ridesalot
<i_am_cyc...@yahoo.ca> wrote:

>On Saturday, April 22, 2017 at 11:14:25 PM UTC-4, Jeff Liebermann wrote:
>Snipped
>> My usual off topic Drivel:
>> How to mount headlights on a front rack:
>> <http://www.cycleexif.com/alex-singer-randonneur>

>Oh man does that bring back memories. I remember front racks
>that had an integral clamp to hold your flashlight.

I've never seen one of those racks. You just answered one of my
questions. I was wondering if the flashlight mounts were part of the
rack design, or added as an accessory. It sure looks like it's part
of the rack.

>Battery powered lights and their mounts sure have come a long ways.

Yep. When incandescent flashlights were in fashion, we could barely
see or be seen. Today, we have 1000 lumen lights that can glare blind
anyone who dares approach. Progress blunders onward.

[AMuzi]

On 4/22/2017 10:14 PM, Jeff Liebermann wrote:
> On Sat, 22 Apr 2017 00:23:48 -0400, Frank Krygowski
> <frkr...@sbcglobal.net> wrote:

-snip-

> The last time we had a
> similar discussion on bicycle chains, I made the same mistake.
> Something is fundamentally wrong with my reasoning. Argh.

-snip-

One more adult admission like that and you'll be banned from
usenet.

[Frank Krygowski]

On 4/23/2017 10:48 AM, AMuzi wrote:
> On 4/22/2017 10:14 PM, Jeff Liebermann wrote:
>> On Sat, 22 Apr 2017 00:23:48 -0400, Frank Krygowski
>> <frkr...@sbcglobal.net> wrote:
>
> -snip-
>> The last time we had a
>> similar discussion on bicycle chains, I made the same mistake.
>> Something is fundamentally wrong with my reasoning. Argh.
> -snip-
>
> One more adult admission like that and you'll be banned from usenet.

My thought as well. "Admit you're wrong? Whoa, that's against the rules!!"


--
- Frank Krygowski

[Jeff Liebermann]

On Sun, 23 Apr 2017 15:07:39 -0400, Frank Krygowski

<frkr...@sbcglobal.net> wrote:

>On 4/23/2017 10:48 AM, AMuzi wrote:
>> On 4/22/2017 10:14 PM, Jeff Liebermann wrote:
>>> On Sat, 22 Apr 2017 00:23:48 -0400, Frank Krygowski
>>> <frkr...@sbcglobal.net> wrote:
>>
>> -snip-
>>> The last time we had a
>>> similar discussion on bicycle chains, I made the same mistake.
>>> Something is fundamentally wrong with my reasoning. Argh.
>> -snip-
>>
>> One more adult admission like that and you'll be banned from usenet.

I do wish that someone would ban me from Usenet and put me out of my
misery. I spend far too much time providing wrong answers, misleading
theories, bizarre designs, worthless ideas, and topic drift.

>My thought as well. "Admit you're wrong? Whoa, that's against the rules!!"

Please forgive my breach of protocol. To err is human and I just
wanted to reassure myself. Feel free to assume that I'm perfect.

[cycl...@gmail.com]

On Saturday, April 22, 2017 at 8:14:25 PM UTC-7, Jeff Liebermann wrote:
>
> Thanks. I'll try not to screw it up again.

Fat chance. Bet I beat you to the punch though.

[Doug Landau]

On Friday, April 21, 2017 at 8:31:27 PM UTC-7, Jeff Liebermann wrote:
> On Fri, 21 Apr 2017 10:40:30 -0700 (PDT), Doug Landau
> <doug....@gmail.com> wrote:
>
> >So you are saying that losses from routing the lower run of
> >the chain through tensioners and idlers are negligible?
>
> Worse. I was ignoring the losses from tensioners, idlers, grease, pin
> rotation caused by a slight chain droop, inertial loading from a
> longer and thus heavier chain, chain acceleration lag, etc. I assumed
> that the original question was about a simple power transmission
> system, not the complex mess that such systems inevitably evolve into.
> Something more like this test fixture and a practical bicycle:
> <http://cdn.mos.bikeradar.imdserve.com/images/news/2012/11/06/1352163122826-1476emv18vmdi-630-80.jpg>
> The additional losses can be tested separately and included later.
>
> You're correct that tensioners, idlers, etc are important.

I'm not saying they are I'm just wondering. It doesn't look like the losses from the derailer on an upright is going to be significant. What I noticed with my rickshaw was that the chain was so long it was hard to keep off the ground due to it's weight. I tried using a derailer as a tensioner, and mounted it upside-down underneath the cab,so the spring would lift it up, near the middle of the run. To my surprise the spring wasn't anywhere near stiff enough. Not even enough to keep the pulleys engaged, let alone the chain held up above level, let alone taught and not flapping. It's what it was going to take to take up the slack that I thought might be non-negligible.