Recently I asked about a centrifugal clutch for motorizing my bicycle.
I already have the bike motorized. It can take me at moderate speeds. It
needs refinement but the basics work.
The problem is this: the engine sits over the rear wheel. Its shaft has a
small v-pulley which drives a 21" rim affixed to the wheel as the driven
pulley. As clutch there is a small wheel on an arm that moves to
tension or loosen the v-belt. I move the the arm with a brake lever on the
handlebar. It's just adecuate. The bad thing is that, even when totally
loose, the mere weight of the v-belt resting on the driving pulley causes
enough friction drag so that pull starting the engine gets very difficult.
This engine pull starts very easily; you have to pull very fast, but
not hard. With the added drag from the v-belt have I pull and pull very
hard and unbelievably the shaft slows down enough to hinder the starting.
For this reason also I can't start the engine by pedalling the bike. I
really cant pedal that fast.
Thus far I have tried to devise a sistem to make the v-belt float over
the driving pulley while starting but I'cant come with anything useful.
So other than removing the belt while I start the engine and then
replacing it (doable but certainly undesirable and unpractical) I can't
figure a way to make it work.
I thought about a centrifugal clutch, but the ones available have
problems:

-The Comet clutch would be ideal, its designed fot high inertia
(minibikes,karts) applications but it engages at 1800 rpm, too low for the
idle spped of the engine. Since its the non-adjustable type I'm not sure
it can be opened and altered to give it higher engagement rpm.

-The chainsaw clutch should engage at the engine +2800 rpm idle speed, but
its smaller than the Comet, plus Eric Snow noted that it would overheat
while engaging, due to the higher inertia. Besides it would thake somewhat
more machining to make it fit.

So with the current setup I'm gonna rip my arm off and keep making the
ridicule in front of the whole neighborhood. Unknown if the Comet could
be hacked to work. As for the chainsaw clutch, well I dont make the engine
propel the bike from still but rather I pedal up to speed and then I
engage the clutch and the engine takes over, so perhaps this should at
least partly alleviate the overheating problem.
What to do?


Thanks in advance,

Camilo









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Camilo Ramos wrote:
Recently I asked about a centrifugal clutch for motorizing my bicycle.
I already have the bike motorized. It can take me at moderate speeds. It
needs refinement but the basics work.
The problem is this: the engine sits over the rear wheel. Its shaft has a
small v-pulley which drives a 21" rim affixed to the wheel as the driven
pulley. As clutch there is a small wheel on an arm that moves to
tension or loosen the v-belt. I move the the arm with a brake lever on the
handlebar. It's just adecuate. The bad thing is that, even when totally
loose, the mere weight of the v-belt resting on the driving pulley causes
enough friction drag so that pull starting the engine gets very difficult.
This engine pull starts very easily; you have to pull very fast, but
not hard. With the added drag from the v-belt have I pull and pull very
hard and unbelievably the shaft slows down enough to hinder the starting.
For this reason also I can't start the engine by pedalling the bike. I
really cant pedal that fast.
Thus far I have tried to devise a sistem to make the v-belt float over
the driving pulley while starting but I'cant come with anything useful.
So other than removing the belt while I start the engine and then
replacing it (doable but certainly undesirable and unpractical) I can't
figure a way to make it work.
I thought about a centrifugal clutch, but the ones available have
problems:

-The Comet clutch would be ideal, its designed fot high inertia
(minibikes,karts) applications but it engages at 1800 rpm, too low for the
idle spped of the engine. Since its the non-adjustable type I'm not sure
it can be opened and altered to give it higher engagement rpm.

-The chainsaw clutch should engage at the engine +2800 rpm idle speed, but
its smaller than the Comet, plus Eric Snow noted that it would overheat
while engaging, due to the higher inertia. Besides it would thake somewhat
more machining to make it fit.

So with the current setup I'm gonna rip my arm off and keep making the
ridicule in front of the whole neighborhood. Unknown if the Comet could
be hacked to work. As for the chainsaw clutch, well I dont make the engine
propel the bike from still but rather I pedal up to speed and then I
engage the clutch and the engine takes over, so perhaps this should at
least partly alleviate the overheating problem.
What to do?


Thanks in advance,

Camilo

Figure out the machining to make a chainsaw clutch or a weedeater clutch
work without extensive mods to the clutch.

Then buy a pile of them.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

Camilo Ramos wrote:

Recently I asked about a centrifugal clutch for motorizing my bicycle.
I already have the bike motorized. It can take me at moderate speeds. It
needs refinement but the basics work.
The problem is this: the engine sits over the rear wheel. Its shaft has a
small v-pulley which drives a 21" rim affixed to the wheel as the driven
pulley. As clutch there is a small wheel on an arm that moves to
tension or loosen the v-belt. I move the the arm with a brake lever on the
handlebar. It's just adecuate. The bad thing is that, even when totally
loose, the mere weight of the v-belt resting on the driving pulley causes
enough friction drag so that pull starting the engine gets very difficult.
This engine pull starts very easily; you have to pull very fast, but
not hard. With the added drag from the v-belt have I pull and pull very
hard and unbelievably the shaft slows down enough to hinder the starting.
For this reason also I can't start the engine by pedalling the bike. I
really cant pedal that fast.
Thus far I have tried to devise a sistem to make the v-belt float over
the driving pulley while starting but I'cant come with anything useful.
So other than removing the belt while I start the engine and then
replacing it (doable but certainly undesirable and unpractical) I can't
figure a way to make it work.
I thought about a centrifugal clutch, but the ones available have
problems:

-The Comet clutch would be ideal, its designed fot high inertia
(minibikes,karts) applications but it engages at 1800 rpm, too low for the
idle spped of the engine. Since its the non-adjustable type I'm not sure
it can be opened and altered to give it higher engagement rpm.

-The chainsaw clutch should engage at the engine +2800 rpm idle speed, but
its smaller than the Comet, plus Eric Snow noted that it would overheat
while engaging, due to the higher inertia. Besides it would thake somewhat
more machining to make it fit.

So with the current setup I'm gonna rip my arm off and keep making the
ridicule in front of the whole neighborhood. Unknown if the Comet could
be hacked to work. As for the chainsaw clutch, well I dont make the engine
propel the bike from still but rather I pedal up to speed and then I
engage the clutch and the engine takes over, so perhaps this should at
least partly alleviate the overheating problem.
What to do?

Thanks in advance,

Camilo

The clutches sold on similar sized garden implements will work. Stop
worrying about slippage. If the clutch slips, it is because the gearing
is too high, or you are trying to get the motor to do something that it
is unable. The solution is to adjust ratios until you get a working
system.

Looking around on the web, I have seen a number of bike motors crafted
from four stroke honda weedwacker powerplants (31cc IIRC). Those are not
exactly the personification of the phrase "torquey engines". They are
all using stock clutches, and pretty large ratio gear reductions.

Low tech solution. Take a look at the old pedal start style
motorcyles. The common factor on them is the kickstand that supports the
rear wheel off the ground while starting. No wheel on the ground equals
no drag on the motor during startup.

Cheers
Trevor Jones

On Wed, 10 May 2006 22:59:21 -0500, "Camilo Ramos"
wrote:


Recently I asked about a centrifugal clutch for motorizing my bicycle.
I already have the bike motorized. It can take me at moderate speeds. It
needs refinement but the basics work.
The problem is this: the engine sits over the rear wheel. Its shaft has a
small v-pulley which drives a 21" rim affixed to the wheel as the driven
pulley. As clutch there is a small wheel on an arm that moves to
tension or loosen the v-belt. I move the the arm with a brake lever on the
handlebar. It's just adecuate. The bad thing is that, even when totally
loose, the mere weight of the v-belt resting on the driving pulley causes
enough friction drag so that pull starting the engine gets very difficult.
This engine pull starts very easily; you have to pull very fast, but
not hard. With the added drag from the v-belt have I pull and pull very
hard and unbelievably the shaft slows down enough to hinder the starting.
For this reason also I can't start the engine by pedalling the bike. I
really cant pedal that fast.
Thus far I have tried to devise a sistem to make the v-belt float over
the driving pulley while starting but I'cant come with anything useful.
So other than removing the belt while I start the engine and then
replacing it (doable but certainly undesirable and unpractical) I can't
figure a way to make it work.
I thought about a centrifugal clutch, but the ones available have
problems:

-The Comet clutch would be ideal, its designed fot high inertia
(minibikes,karts) applications but it engages at 1800 rpm, too low for the
idle spped of the engine. Since its the non-adjustable type I'm not sure
it can be opened and altered to give it higher engagement rpm.

-The chainsaw clutch should engage at the engine +2800 rpm idle speed, but
its smaller than the Comet, plus Eric Snow noted that it would overheat
while engaging, due to the higher inertia. Besides it would thake somewhat
more machining to make it fit.

So with the current setup I'm gonna rip my arm off and keep making the
ridicule in front of the whole neighborhood. Unknown if the Comet could
be hacked to work. As for the chainsaw clutch, well I dont make the engine
propel the bike from still but rather I pedal up to speed and then I
engage the clutch and the engine takes over, so perhaps this should at
least partly alleviate the overheating problem.
What to do?


Thanks in advance,

Camilo

It seems to me that the chainsaw clutch would work. You don't really
want the motor running at idle when it is is driving the bike so just
rev up the motor, the clutch engages, then use your present belt
clutch system for the final drive. So, the chain saw clutch allows
starting while your present clutch allows driveability. On the other
hand, you may be able to fit stronger springs to the Comet clutch. Go
to a mini bike or fun kart store and look at the clutch. They are
really simple. Maybe you could piggyback a pair of springs on top of
the existing springs. I have a customer who used to race go carts.
Next time he comes by I'll ask him if he has any suggestions.
Eric







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