Belt drive Sprockets on the Cheap!

[Miles]

I see that Comet also have 5M split pulleys up to 144t (on close out..). Might be useful for those that want a large ratio single stage drive. You could get 2 or 3 pulleys out of the 40mm width, if you devised a way to mount them (fix to plywood disk, etc...)

http://www.cometkartsales.com/store/bel ... ockets.htm

[boostjuice]

Some work with a Pfeifer 5M pulley > rear hub adaptation over at motoredbikes.com

[boostjuice]

More Pheifer pulley/belt sprocket resellers (other than cometkartsales.com)

http://www.out2win.com/catalog/pfeifer.html

http://host0114.csmhosting.com/iw_products.m4p.pvx?;products_no_tree?company=APS?CAT=BDP

[Miles]

Thanks! 1 piece pulleys from 65t to 90t. Just what we were after

[full-throttle]

An interesting way of fabricating belt drive sprockets:

ABDS.1.engl.pdf

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Each belt disk consists of three elements:

Adapter plate. It connects hub and belt. On the inner side, it has either five holes on a bolt circle 74mm or a contour for Shimano 9-spline hubs, 3-fold contour of most internal hubs and others, on the outer side the shape of the belt geometry.

Thickness of the adapter plate is 3mm.



Belt disk. Two of these disks are screwed either to the left or right side of the adapter or to both sides.
This allows to get nearly any chainline by simply switching a disk from one into another position.

If you plan to use the belt drive on a bike with higher power output (tandem, electic engine) please use one or two additional toothed disks. We send you the corresponding belt (8 or even 10mm wide).

On the inner and outer side there are two protection disks, that hold the whole package together.

http://www.schlumpf.ch/hp/zr/zr_engl.htm

[edaz40]

if surface finish is a problem,have you run one a little yet?the belt may burnish it to a smoother finish,or wire edm it and inatall thin plates to the sides to retain belt(3 pc ),or send the water jet part out for chem. de-burr.ever try to make thhe gear out of glass filled nylon-called nylon 66-which is 66% glass fiber in the nylon mix.plastic supply houses sell it in sheets,cut to order,then add alum.side plates.you can drill&tap nylon easily.ed

[recumpence]

I hate to break this to you but, I bet 5mm pitch will skip when used as a final drive with any amount of power put through it. You may have to go up to 8mm pitch. Of course, that depends on width (it looks pretty wide, maybe 25 or 30mm?) and number of teeth engaged on the small pulley.

Matt

[magudaman]

Cool thread, I'm been so busy I am behind on the times here, its nice to some cool designs going through here!

I made my own belt sprockets for my Motoped and it really has been working out pretty good. They took me way too long to do since I had to mill them using a 5/32in end mill and just under 1in thick. I've been wanting to get a the 4th axis running on the mill so I could just use a stub mill to do them extremely quickly. I had also considered similar ideas to what you guys were talking about here such as the thin section of sprockets that would be bolted together. I'm currently running the 20mm wide 8mm pitch powergrip GT2 belt. I've pushed just under 10 HP through it and has not ever skipped a tooth.

Just FYI, Polychain and powergrip are two different profiles and are not compatible. Polychain is really the ultimate. I would love to run that and could get away with only 12mm wide belt.

I also am running not recommend size sprocket. I in the photo is a 14T and 15T, gates recommends no less than 22T. So apparently I will get advanced belt wear, but I'm at 270 miles so far with out any signs yet...





I didn't see the photos of these posted here anywhere:






Both are supposed to shed mud and have crazy torque handling abilities, very innovative design I thought.

[bobc]

I just started putting myself a new bike together. I've bought a gates carbondrive belt (it was £74 - you'd buy quite a few chains for that price) and I'm making the pulley/sprockets to the schlumpf design.
The gates belt drive system does have some problems in the field, allegedly, with some users reporting skipping. I've tried to avoid this by going for large diameter pulleys (to get a good wrap) and I will make position for a "snubber" wheel to ensure full tooth engagement as the belt joins the rear pulley. I don't want too much belt tension, I feel that would ruin the geared hub (I got a shiny new alfine 11 ;^)
I am getting 3 test pulley parts lasered this week, at various amounts undersize, to determine the best outside diameter for the "11mm" pitch. WHen I figure it out I'll let you know.

edit humblest apologies for soiling the "non-hub" arena with info about a PEDAL POWER ONLY bike..............

[magudaman]

Well I had some free time on a 60w laser cutter and made these test cutouts out of acrylic. I'm not sure if I can use something like Delrin but that may work as an actual sprocket, maybe not. There needs to be some tweaking of size of the teeth due to the laser cut size. The assembled block actually lines up better when it is actually bolted down.

[CNCAddict]

Man...great minds think alike BTW delrin works fantastic, better than aluminum. I have maybe 1000 miles on the one in the picture.

tn_IMG_0747.JPG

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[bobc]

CNCAddict -
what belt is that? it has the look of the gates carbodrive about it. but not completely...
I'm interested in tooth profile and exactly what "outside diameter" you used (I have this theory it should be a bit less than the theorectical value for the tooth pitch but don't know how much less). To be honest your tooth profile doesn't look perfect - could that be because the belt has worn?
cheers
Bob
PS see below - miles U R A star

[Miles]

Bob,

This is Gates' original modified curvilinear profile patent, I think.

[bobc]

Great miles - that explains what we see in CNCAddict's photo, I guess he assumed (like me) the tooth form was a single radius.
Who'd have thought that the best tooth flank shape was a tractrix (thats the curve made by a wheel on the end of a stick when you push the other end of the stick along a straight line).
Shame it's a genreal patent without the carbondrive specific measurements in.... but there's enough there to do a good enough job!
Bob

[Miles]

Do you mean the 11mm pitch carbon-drive? That's definitely a modified profile. It might be worth getting in touch with Gates - they might supply you with a CAD file....

[bobc]

"It might be worth getting in touch with Gates - they might supply you with a CAD file...."
haha - I'd give long odds they won't ;^) - their profits come from their exhorbitant pulley prices...
What's more I intend to put my pulley dxfs on this site.........!!!! (when I'm happy)

[Miles]

This one was granted last year - priority date 2008........:

[bobc]

Even better - what's clear from this is that the sprocket shape in the conjugate flank portion is somewhat immaterial (so long as it doesn't impede belt entry) - the torque is transmitted by the "linear flank portion" and the belt itself takes care of clearance during wrap/unwrap (where interference is withthe linear flank portion anyway). I could use trapezoidal tooth form on the sprocket (note genuine gates sprockets only have the linear part of the tooth - see photos above) I'll take measurements off a photo of belt profile & work from there. I suspect this tooth form may be specific to the new centre track belt, & the tractrix used on the original belt, but the belt profile photo should sort that out. Clearance is advisory anyway to prevent tooth rubbing during wrap/unwrap, which would generate noise and rob efficiency as well.

[etard]

Maguda,
Those are some beautiful pulleys man!!

Delrin: I have a decent amount that my friend gave me of various diameters between 2-4" diameter and about 6" long or more. I would be willing to trade material for a finished sprocket if anybody is interested in making drive sprockets with Delrin. I can probably get more as well.

[CNCAddict]

Yeah, I'm using the Polychain carbon 8mm pitch belts (12mm wide). I found an old gates patent that had crap for information..then tweaked the design in by eye. Absolutely no problems so far with the belt or delrin sprockets. The hardest part is getting the correct belt tension....I'm using a ghetto DIY spring tensioner since I have it on a dual suspension bike. I also advise against using a fixed tensioner since a twig or rock getting between the belt and sprocket could overstress components, with a spring tensioner the belt just moves out of the way to let the debri pass. Compared to a metal chain this is like night and day. No grime or grease and it's at least 10x quieter. I can only hear the wind and my tires. I'm never going back to chains.

PS, these guys have the best prices by far, unbelievably cheap for a carbon fiber belt http://shop.limct.com

[bobc]

photo of the gates carbondrive belt - this is the old cdx stuff, not centretrack. You can see there's no sign of a flat section near the root of the teeth

[Miles]

PS, these guys have the best prices by far, unbelievably cheap for a carbon fiber belt http://shop.limct.com

Crikey! That is cheap! Thanks David

[bobc]

did 3 test sprockets, then made the real thing ;^)

happy with the wrap on that. I'll post a pic of the finished pulley in place in the fullness of time.
That's just one of the laminations, unfinished, straight from the laser place.

[Miles]

What does it cost per lamination piece to have them cut, Bob?

[E-racer]

WOW! That's nice! Are you going to be willing to make them for other people?