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Tensile Freewheels


Mike Poyzer @ Onza

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Surely for the 22t model you could have used the extra size to make a better freewheel by using bigger/more pawls and deeper ratchets rather than just ordering a larger plate on the current one which looks ridiculous.

Nice idea though having different sizes

No because if you had it bigger and had the same amount of grooves in the rachet you would end up with deeper ones but also it would take more of a crank turn to it engage. So you would have to have more grooves in the rachet to make up for it but then you would loose the advantage of the deeper rachet ring.

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No because if you had it bigger and had the same amount of grooves in the rachet you would end up with deeper ones but also it would take more of a crank turn to it engage. So you would have to have more grooves in the rachet to make up for it but then you would loose the advantage of the deeper rachet ring.

No matter how far out on the radius of the sprocket the rachet is positioned aslong as there are the same amount of rachets the crank would have to turn the same distance because the angle the crank turns though = 360 divided by no. of engagements

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Developing this freewheel took a lot of time and funds trying different ideas. Once the configuration was decided we invested a lot more money on tooling for pawls, springs and toothed rings for production. Producing a 22 tooth and a 16 tooth are speculative ventures to a large extent and to have designed and developed different internals to those of the 18 tooth would have tripled the development costs. Since we felt that the 18 tooth was our optimum, it made sense to use the same internals on other sizes. Therefore the only change required was the outer toothed sprocket. It was a case of either having other sizes with the same internals or not having other sizes at all.

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  • 5 months later...
No matter how far out on the radius of the sprocket the rachet is positioned aslong as there are the same amount of rachets the crank would have to turn the same distance because the angle the crank turns though = 360 divided by no. of engagements

i don't think thats completely correct... if you increase the size of the radius of the ratchet and still keep the same amount of teeth the distance between each tooth will increase. so that means you will have to move the crank further for it to engage. i think i'm right by saying if you double the radius if the ratchet you would have to double the amount of teeth for the crank to move the same distance on the orginal ratchet for it to engage. thats why its more accurate to use radians rather than degrees because radians is a measure of radius over angle swept.

i might be taking complete rubbish though so feel free to prove me wrong.

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i don't think thats completely correct... if you increase the size of the radius of the ratchet and still keep the same amount of teeth the distance between each tooth will increase. so that means you will have to move the crank further for it to engage. i think i'm right by saying if you double the radius if the ratchet you would have to double the amount of teeth for the crank to move the same distance on the orginal ratchet for it to engage. thats why its more accurate to use radians rather than degrees because radians is a measure of radius over angle swept.

i might be taking complete rubbish though so feel free to prove me wrong.

No it doesn't, if you increase the rachet, thus increasing the tooth size, it doesn't make any difference to how far you move the crank arm, because the crank arm rotates, so you move it through 360/36= 10 degrees for every engagement.

The freewheel itself can be any size, because it engages 36 times per rotation.

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ok i've drawn a pic to show what i mean. if you look at the blue teeth on the inside of the ratchet (8 for simplicity) and there's a black line, a indicating how far the pawl has to travel along the ratchet tooth before it engages again. each freewheel has the same number teeth inside the ratchet but if you can see the bigger one has to travel further for it to engage. do you see what i mean?

post-393-1199651185_thumb.jpg

Edited by mafu26
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ok i've drawn a pic to show what i mean. if you look at the blue teeth on the inside of the ratchet (8 for simplicity) and there's a black line, a indicating how far the pawl has to travel along the ratchet tooth before it engages again. each freewheel has the same number teeth inside the ratchet but if you can see the bigger one has to travel further for it to engage. do you see what i mean?

post-393-1199651185_thumb.jpg

mat's designing a wheelchair that's capable of taking steven hawking to the top of a mountain. he knows his shit.

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yeah, as far as your foots concerned at the end of the crank arm, it doesnt make any difference, the smaller diameter ratchet would surely need to be stronger 'cos it's got more leverage on the teeth?

providing both large and small ratchets have the same number of engagements yada yada yada

Edited by toxicturky
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urg i dunno. confused now :S good bit of banter though

edit: yeah i'm talking rubbish. think i'm confusing it with if your crank arm was longer then you'd have to move your leg more...?

Edited by mafu26
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