Belt drive Sprockets on the Cheap!

[etard]

Very cool Bob! You definately should provide these for the community, IF you have the time. The design looks great!

[bobc]

I picked this lot up today for £40

I'm attatching the design dxf files so anyone can get some lasered, but I suggest you wait 'til I've ridden the bike.... ;^)
Also note it's geared for a particular belt on a particular road bike with particular internal geared hub - you'll probably want something different so I'll also add the XL file I use to belt lengths.
My pulleys are 62:27
chainring is ally, rear sprocket is stainless
If it does work OK (& I think it will) I'll put all the design data up on here (dimensions & tooth notch shape)

[bobc]

Gates "carbondrive" pulleys complete & fitted on my new bike. The setup feels pretty good even though it's not tensioned properly yet. Cleaning the flash off the lasered aluminium parts took ages (about 3 hrs) but the laminations stack made getting the beltline right an absolute breeze! Youcan see where I made the rear triangle split in the first picture.

and the screws on this will be exchanged for less unsightly ones!

So - one or two little jobs still to do, but looking pretty good I reckon!

[rodgah]

excellent job Bob. Im surprised you went with ally for the chain ring....then again you might change your mind and redesign a lightweight stainless design if you did it again, ally just never cuts all that nicely on a laser since its around 70% reflective to IR light......always looks like a million miniature beavers chewed at it.

I have thought of doing this process for the powered side, just never had the patience to sit down and find/draw the tooth profile. Im also surprised you got such a intricate piece (rear sprocket) without plate warp, probably due to a higher quality machine than I am used to playing with. I would of thought the 'teeth' would of faced the opposite way, so it would throw the muck out when its disengaged from the belt, and if over torqued the teeth would stand up taller, not lay down.

Very good job anyway

[bobc]

Ta: - went for ally for weight obviously, at 3mm thick it should be able to stand up for itself (chainrings can get clobbered...). The rear sprocket is stainless weighs 400gms, hate to think what the "chainring"would be...
The teeth are that way round so that the bearing/loaded tooth surface is a full face contact on the sprocket - otherwise you'd surely wear little "hooks" on the belt teeth which wouldn't be nice.. Anyway - we'll see what it's like;- I can always turn 'em round ;^)

[Miles]

The teeth are that way round so that the bearing/loaded tooth surface is a full face contact on the sprocket - otherwise you'd surely wear little "hooks" on the belt teeth which wouldn't be nice..

That's certainly the way they were designed to be used. See: http://www.schlumpf.ch/hp/schlumpf/bild ... 1.engl.pdf

[GITech]

This is certainly cool stuff here and in the thread you posted Miles!

I'd like to get into belts too, but I'm restricted by clearance issues in my design, so I have to stick with chain.

I'll be watching though!

Later,
Jay

[rodgah]

The teeth are that way round so that the bearing/loaded tooth surface is a full face contact on the sprocket - otherwise you'd surely wear little "hooks" on the belt teeth which wouldn't be nice..

That's certainly the way they were designed to be used. See: http://www.schlumpf.ch/hp/schlumpf/bild ... 1.engl.pdf

doh!.....of course

[bobc]

The bike is together now

I must say, so far, it has delivered all I had hoped; flawless and convenient gears from the alfine 11 speed hub and versa "STI" style shifters and a magic carpet ride from the belt transmission. I guess we'll see over the next thousand miles or so whether my pulleys cause accelerated belt wear. Meanwhile here is the extra design information about the timing pulleys:
1) the "blank" diameter is ( N * 11 / pi ) - 1.8 mm where N is the number of teeth
2) my tooth cutout profile is shown in the sketch below

this looks pretty good on the pulleys I've made. Put a circular array of these notches on the blank above ;^)

[bobc]

stop press.... now the clocks have gone back & the weather is good - cycling to work is on again... took the new bike today (15 miles in each direction) & it was perfect - best bike I've ever had, smooth, silent & fast. But it's the silence that's great about this, no creaks, no chain noise or derailleur noise. Very happy ;^)

[Hillhater]

Backtracking a year or so....
..was there any development of the "barrel gear" internal drive for the chain ring.. ?

[Miles]

Cross ref:
http://endless-sphere.com/forums/viewto ... 28&t=26226

[bobc]

-Keeping up to date - 700 miles on the bike now - belt & pulleys all as good as new (apart from a single rusty nut on the chainring - OK I'll swap it....)

[Eclu Lardbut]

Regarding using belt drive on ebikes...
Seems to me the very cheapest option for belt drive pulleys is off the front of modern car engines. Thousands and thousands of them are in breakers' yards and it won't take much to find suitable sizes that can be used on a bike drive system.
There are idler wheels too, with bearings, that can be used as tensioners. The main engine pulleys consist of crank (which is usually a fairly wide bore in the middle, but not beyond the wit of man to adapt/fill in), often a fuel pump or water pump pulley, and then the single or twin crankshaft pulleys.
I certainly would /will look there when I'm needing some.

[amberwolf]

A friend of mine rebuilding his Dodge Stratus engine had the timing belts and pulleys off, and I pondered using a set of those for belt drive. I'm sure I could find a Stratus in a junkyard I could pull them from--but then I saw what it woudl take to get that far (practically have to take the engine out), and decided I would never have enough time to spend at the junkyard to do it.

[5134ev]

I welded a 26 inch rim to an existing 26 tire and wheel for a trike and then used a 1 1/2 inch pulley on the motor.Belt went from the motor pulley to the welded wheel (as a large pulley.This gave about a 17 to 1 reduction and with my 2500 rpm motor gave about 12 mph speed.I had voltage switching from 24 volts and 12 volts so it was pretty efficient though I had a little belt slippage when starting.However it eliminated the 10% loss you get with a pwm speed controller.
Robert

[jk1]

What would be the smallest pulley teeth count you could use on the gates 8mm pitch carbon drive belts ? this is for a mid drive on the motor side.

In the data sheet i think 22teeth is the minimum, if i made a custom drive sprocket would it work for say an 16 or 18 teeth cog on the motor ? or would it slip, I am thinking of using the 10mm wide CARBON POLYCHAIN FOR a 3 to 4 kw motor would that work for such a small motor pulley ? would i have to use idler to increase the belt wrap ?

[Miles]

What would be the smallest pulley teeth count you could use on the gates 8mm pitch carbon drive belts ? this is for a mid drive on the motor side.

In the data sheet i think 22teeth is the minimum, if i made a custom drive sprocket would it work for say an 16 or 18 teeth cog on the motor ? or would it slip, I am thinking of using the 10mm wide CARBON POLYCHAIN FOR a 3 to 4 kw motor would that work for such a small motor pulley ? would i have to use idler to increase the belt wrap ?

I've used 16t for 8M PowerGrip belts. It's possible that the tooth geometry or construction of the Carbon PolyChain belts would be more restricting, though. Obviously the capacity would be lower.

You need to specify the driver pulley speed, in addition to the power, to make any kind of judgement...

[jk1]

Driver pully speed will be about 400-500 rpm and power will be under 4kw.

The reason i like the polychain is that it seems with an 8mm pitch belt and 10mm wide belt pully it should be able to handle 3-4kw easy as its rate to 30hp at 500rpm? i think my main problem will be if i make the drive pulley too small... but i need it as small as possible to get as high a ratio as possible.

One thing that just occured to me can u get the carbon poly chain in small lengths ? i.e to suit mid drive or are they only made very long to replace normal bike chain ?

135mm centres between the gears and 18 or 20t on the motor to 80 or 90T on the cranks is what i was thinking for the drive. These pulley sizes are not available off the shelf i think so i may need to custom make them?

[Miles]

CNCAddict has used an 18t pulley with PolyChain:
viewtopic.php?p=520282#p520282

[Miles]

One thing that just occured to me can u get the carbon poly chain in small lengths ? i.e to suit mid drive or are they only made very long to replace normal bike chain ?

The CarbonDrive system made for bicycles is 11mm pitch. You want the Industrial stuff (also used for tandems).

[Miles]

Have you got the design manual?
http://www.gates.com/catalogs/index.cfm ... Design#ddm

[Miles]

would i have to use idler to increase the belt wrap ?

You could try with a "snubber" pulley first (engages only if the belt starts to rise on the teeth).

[magudaman]

What would be the smallest pulley teeth count you could use on the gates 8mm pitch carbon drive belts ? this is for a mid drive on the motor side.

In the data sheet i think 22teeth is the minimum, if i made a custom drive sprocket would it work for say an 16 or 18 teeth cog on the motor ? or would it slip, I am thinking of using the 10mm wide CARBON POLYCHAIN FOR a 3 to 4 kw motor would that work for such a small motor pulley ? would i have to use idler to increase the belt wrap ?

I have been using 15T 8M PowerGrip GT2 Belt on my setup for over 400 miles with no issues. The sprocket was cut by me too. The carbon belts might not be quite as happy with that tight radius though. They are much more stiff belts in contrast to the powergrips, like plastic verses rubber.

From I understand the key number is teeth in mesh. From the documentation I have read you need at least 6 teeth in mesh to have 100% of the torque rating. Which actually is really easy to do. I talked with gates for a while the one day and they told me the problem with lower than 22t stuff is accelerated belt wear. The fibers are bending further than they were designed to do. While a belt my last a lifetime in perfect conditions with a 22T unit it may only last a season or 1000 miles on 15T or 16T. Basically go with the largest you can get on your driver.

PFEIFER INDUSTRIES makes custom belt drive stuff and are great to talk with. There product are top notch, use them if you can. The reason I say this is they have a really nice calculator that will give teeth in mesh and other handy stuff. I have attached it.

[magudaman]

I also am trying a new cutting technique that now let me cut sprockets in no time!








Its on the bike now running and seem to be holding up great. The 6061 is definitely softer and wears quicker than the 7075 I used for my original stuff.