10 tooth freewheel? (a little project)

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10 tooth freewheel? (a little project)

Post by recumpence » Oct 27 2010 8:01pm

Hey Guys,

Here is a simple item (of course, I say "Simple" as a relative term. This darn thing took me an entire day to make). This is a 10 tooth freewheel. The story behind this item is;

My Catrike has a 26 inch rear wheel. I have been running a Astro 10 turn 3210. However, it is a bit anemic for someone like myself who is used to more power. So, I wanted to gain a bit, but without spending a fortune, or going to another reduction stage. I had a 6 turn 3210 on the bench. However, in order to retain the same 33 mph top speed (perfect for a 3210), I would have to gain some serious increase in reduction. I was, previously, running a 16 tooth freewheel and a 56 tooth rear chainring. Also, I was running a 20 tooth motor pulley. Well, the math showed a 18 tooth motor pulley, 62 tooth rear chainring (the largest chainring that is reasonably priced at $52. Going to a 75 tooth would cost $190!). That leaves a freewheel tooth count of 10. Hmm, how to do that? Well, a sprague would never hold the torque, besides I have always wanted to try this. So, to that end, I made this part.

It consists of a machined (narrowed) #40 sprocket. I bored it out and added a needle bearing for freewheeling. Then I machined an adaptor to mesh with the 16 tooth freewheel. I purposely used a ACS freewheel because of their very ow resistance freewheeling. A White Industries freewheel has alot of drag if spun too fast. This freewheel allows me to pedal without too much drag from the tiny sprocket spinning a large freewheel.

How does it perform? AWESOME! This thing pulls really hard, now. It used to be kind of a pooch to say the least. I mean, it was fun to ride and very efficient. But, it was not torquey. Now, this thing pulls HARD! If I get hard on the throttle in mid corner, it will spin the tire a bit. I am very surprised. Also, my efficiency is only 19wh per mile at 20mph without any pedalling. Also, that WH only goes up a small amount if I am really hard on it.

This is my favorite setup so far, per dollar. There is some chain noise with that tiny sprocket. But, it is not too bad.

Anyway, enjoy the pictures.

Matt
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Re: 10 tooth freewheel? (a little project)

Post by Hillhater » Oct 27 2010 8:28pm

Neat solution Matt,..
.... but have you considered going with the #35 or 219 chain system as used on go karts. ?
you would not only have a wider choice of inexpensive sprockets (up to 100T) and drivers down to 9T, but you could also use a kart centrifugal clutch on your intermediate drive shaft as both a "freewheel" and as a "Slipper" to eliminate the initial power surge and overcome the start up issues for sensorless motors.
http://www.gokartsupply.com/clutches.htm
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Re: 10 tooth freewheel? (a little project)

Post by vanilla ice » Oct 27 2010 8:43pm

Love the way you mated to the freewheel.. so #40 chain would work with bicycle sprockets huh?

I have a couple of those clutches. No bearings, I think bushings! Very inexpensive, comet I think is the brand. One is even a #40 IIRC. They make adjustable ones, but those do cost more.

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Re: 10 tooth freewheel? (a little project)

Post by Hillhater » Oct 27 2010 9:09pm

There are 100's of manufacturers of those kart clutches many with roller bearings (Noram) , but bushings are acceptable as they are only in use when the motor is not running.
Engagement speed can be "adjusted" on most of them by changing the internal springs and / or weight of the shoes.
Obviously you would run the chain to suit the sprockets.
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Re: 10 tooth freewheel? (a little project)

Post by mud2005 » Oct 27 2010 9:30pm

nice work as usual, I had a similar design sketched out, but never made one. now all I have to do is copy yours :D seriously though, kick ass job.

are you going to offer these for sale?

also, where to get a 62T chainring? I thought 60 was the biggest from vuelta
Last edited by mud2005 on Oct 27 2010 9:34pm, edited 1 time in total.
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Re: 10 tooth freewheel? (a little project)

Post by katou » Oct 27 2010 9:33pm

Let me see if I understand:

You found a 10 tooth sprocket that matched the pitch of normal bike chain
made it thinner
mated it to a freewheel with an adapter
now the little sprocket freewheels with the larger sprocket on the freewheel

voila 10 tooth freewheeling sprocket

Is this correct? Seems like a good solution that most here could actually take a whack at.

Why do you figure it has changed the performance so dramatically?

Katou

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Re: 10 tooth freewheel? (a little project)

Post by recumpence » Oct 27 2010 9:47pm

Yes, that is correct.

The performance was increased by using a higher RPM motor with a further reduction for the same top speed. More motor RPM for a given top speed, the more power you get.

Matt
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Re: 10 tooth freewheel? (a little project)

Post by mud2005 » Oct 27 2010 10:01pm

more questions... :) would this be possible to use for a single stage drive? like a 3220 10turn w/ a 9t to a 62t chainring? at 44V that should be somewhere around 33mph i think

how long would the motor shaft have to be?
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Re: 10 tooth freewheel? (a little project)

Post by liveforphysics » Oct 28 2010 12:45am

Nice work! For a given input voltage, you've boosted continous power ability by 40% (increased motor KV), and increased continous torque ability at the rear wheel by 40% as well. :) All-around win for everyone but the poor controller, but if it can handle it, then it's just all wins. :)

Nicely done!
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Re: 10 tooth freewheel? (a little project)

Post by recumpence » Oct 28 2010 5:30am

A few things here;

#1 Yes, a single stage reduction is possible this way. However, as Gary has found, it is noisey due to the high motor RPM. Also, you lose a bit of power when you go to a lower motor RPM for a given speed, anyway. So, at that point, the added cost of the bigger motor is not used.

#2 Yes, I have been researching a centrifugal clutch for some time, now. I may move in that direction. I do not like the power loss with the slip, though.

#3 The big chainring is from the Hostel Shoppe in Wisconsin. It was, by far, the cheapest large chainring I could find. It cost $52. To go up to a 75 tooth would cost $190! :shock:

#4 Luke, you are correct. The controller is plenty happy right now, though. I have found the maximum load a HV160 will tolerate long-term is a 3220/6 turn Delta. This is roughly the same KV, but in Wye and 1/2 the rotor mass. I am not sure the reason for this, but according to Astro and Castle, a big motor (big for an RC controller) is very hard on these tiny ESCs mainly in Delta. There is something to do with, not only the KV, but also the termination that makes it so hard on the ESC. Ideally I would love to move to a 4 turn Wye 3215. That should leave plenty of headroom for the controller, while giving a 50% power boost from where it is now. This is not a power machine, though. Heck, the frame is a bit spindly to be pushing huge power though (huge for a bike). So, this may be the permanent setup. However, I would, indeed, love to try a 3215 just for kicks. After all, I know the controller will handle it. And, hey, I live in a hilly area. I can definately use some extra power! :wink:

Oh, one last thing, I am still running my torque limiter slipper clutch. However, with this setup, the belt surface speed is 40% higher (and the RPM of the clutch). That gives me 50% more power to the rear wheel before the belt skips or the clutch slips. This was a big part of the reason for this upgrade. I wanted to see how much power I could get to the rear wheel with a belt drive primary reduction.

Matt
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Re: 10 tooth freewheel? (a little project)

Post by dontsendbubbamail » Oct 28 2010 7:26am

vanilla ice wrote:Love the way you mated to the freewheel.. so #40 chain would work with bicycle sprockets huh?

I have a couple of those clutches. No bearings, I think bushings! Very inexpensive, comet I think is the brand. One is even a #40 IIRC. They make adjustable ones, but those do cost more.
#40 sprockets have the same pitch and barrel diameter as bicycle chain. You just have to cut the sprocket width in half to work with 1/8" bicycle chain.

Bubba

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Re: 10 tooth freewheel? (a little project)

Post by GGoodrum » Oct 28 2010 3:13pm

How is the noise with this small of a sprocket? As I recall, from Miles' chordal chart, anything under 12t will get pretty noisy.

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Re: 10 tooth freewheel? (a little project)

Post by Hillhater » Oct 28 2010 4:10pm

recumpence wrote:
#2 Yes, I have been researching a centrifugal clutch for some time, now. I may move in that direction. I do not like the power loss with the slip, though.

Matt
Matt, the centrifugal "Drum" clutches can be "set" to have minimal slip range. I depends on the design of the clutch shoes and pivot system.
Infact when any significant amount of slip is required , as it is on some race karts, then a different type of disc clutch is used.
The clutch would also perform the same function as your "Slipper clutch" too.
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Re: 10 tooth freewheel? (a little project)

Post by spinningmagnets » Oct 28 2010 4:49pm

I also really like the sprocket adapter you made. It reminds me of nuts that are "castellated" so they can accept cotter pins. Brilliant solution, as it is something that others can make, and most would prefer to buy...from someone like you!

Image

Here is a 9T rear BMX hub that I considered for a jackshaft to back-drive by adapting a large diameter pulley to it (the left spoke-flange?), but they are expensive, and I like your solution better.

Image
Last edited by spinningmagnets on Oct 28 2010 4:56pm, edited 1 time in total.

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Re: 10 tooth freewheel? (a little project)

Post by recumpence » Oct 28 2010 4:53pm

GGoodrum wrote:How is the noise with this small of a sprocket? As I recall, from Miles' chordal chart, anything under 12t will get pretty noisy.

-- Gary
Chordal affect is also related to RPM. The sprocket does not spin fast enough to make much noise. The motor whine is louder than the sprocket. I do feel the buzz of the chordal affect just a touch at certain RPM, though.

Matt
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Re: 10 tooth freewheel? (a little project)

Post by Hillhater » Oct 28 2010 6:18pm

GGoodrum wrote:How is the noise with this small of a sprocket? As I recall, from Miles' chordal chart, anything under 12t will get pretty noisy.

-- Gary
Odd, i am used to Karts where a 9 or 10T (#219) sprocket is common running up to 15-18,000 rpm, and chain noise is not an issue. !
.. but then again a 100cc 2 stroke at 18k rpm tends to drown out most things :lol:
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Re: 10 tooth freewheel? (a little project)

Post by MitchJi » Oct 29 2010 7:24pm

Hi Matt,
recumpence wrote:Here is a simple item (of course, I say "Simple" as a relative term. This darn thing took me an entire day to make)...

Matt
Why not bolt the sprocket to the adaptor (make it thinner if necessary) rather than cutting all the notches?

Why not #219, something like 14t to a 72t Extron composite sprocket? More compact and both the 14t and the Extron composite would be quieter.
Last edited by MitchJi on Oct 29 2010 9:22pm, edited 2 times in total.
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Re: 10 tooth freewheel? (a little project)

Post by johnrobholmes » Oct 29 2010 7:37pm

Pretty cool there! I have been looking around for small gearing solutions too. I have been tempted to try a bike without a freewheel.

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Re: 10 tooth freewheel? (a little project)

Post by www.recumbents.com » Oct 31 2010 2:25pm

Hey Matt,

Would something like this work?

http://www.jrbicycles.com/storefront/in ... ductId=651

It's a 10T freewheel, but it's designed for a specific hub. You make your own freewheel adapters anyway, so this should not be a issue.

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Re: 10 tooth freewheel? (a little project)

Post by JEB » Oct 31 2010 4:20pm

That Odyssey most likely would not live, the freewheel that Matt is using because of it's diameter will take more torque.

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Re: 10 tooth freewheel? (a little project)

Post by mud2005 » Oct 31 2010 4:53pm

JEB wrote:That Odyssey most likely would not live, the freewheel that Matt is using because of it's diameter will take more torque.
the odyssey driver would need to be inside a ratchet mechanism and thus would have a larger diameter. also bmx drivers usually have multiple bearings inside so they could easily handle the torque
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Re: 10 tooth freewheel? (a little project)

Post by vanilla ice » Nov 01 2010 11:26am

dontsendbubbamail wrote:#40 sprockets have the same pitch and barrel diameter as bicycle chain.
Cool, so I could run a #40 chain to mate a bmx sprocket to a #40 sprocket! I wonder how noisy that would be though.

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Re: 10 tooth freewheel? (a little project)

Post by deecanio » Nov 01 2010 1:29pm

what im really waiting for is Matt to embed a freewheel into a cluster, now that would be 8) 8) 8)


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Re: 10 tooth freewheel? (a little project)

Post by dontsendbubbamail » Nov 01 2010 2:03pm

vanilla ice wrote:
dontsendbubbamail wrote:#40 sprockets have the same pitch and barrel diameter as bicycle chain.
Cool, so I could run a #40 chain to mate a bmx sprocket to a #40 sprocket! I wonder how noisy that would be though.

I guess you could, but if you have a band saw or a grinder it is easy to cut the #40 sprocket down to run with standard bicycle chain.

Bubba

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Re: 10 tooth freewheel? (a little project)

Post by SoSauty » Nov 04 2010 6:05pm

Hey Matt,

Another useful creation, way to go. Also, didn't know that #40 was same as wide bike chain, handy to know. There's a question about single stage drive I'd like to follow up on: one could use an Astro 3220 yet could similiar adaptation be made with your little slipper clutch up on the motor shaft?

Would the Case that fits over the drive shaft temper the noise a bit?

Good ole 6 or 7turn, 10 to 75tooth; seems 47-51mph realistic;
(7turn 12 to 84tooth? motor mounted about 6" off the ground just in front of the rear wheel)
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