Jackshaft Gates PolyFlex belts for jackshaft/friction drive reduction?

Discussion in 'Transmission / Drivetrain' started by LewieBike, May 23, 2014.

  1. LewieBike

    LewieBike New Member

    I'm somewhat familiar with Gates PolyFlex belts, as I own a Dolmar/Wacker metal cut-saw which uses the 7 mm Gates Polyflex. They handle, at least in this width, almost 7 HP from the Sachs-Dolmar 72cc engine, and I've been looking at fabricating a drive system for my little 32 cc engined powered bike with an eye towards a flexbelt. Has anyone made or used a PolyFlex belt drive in a bike drive system?

    Seems like the 5MM width would be perfect for a moderate power, 32 cc 2stroke engine application. I've got some parts I'm putting together for this and from my own experience with the Wacker with some pretty long days cutting big pieces of scrap steel and iron into small bits, the Polyflex belts really hold up under use. I guess it surprises me that there are no articles in the forum about home builders using these belts instead of cog-belts or chains. For one thing they're more tolerant of tension and can handle a tiny amount of misalignment.

    This will be driving a fairly large diameter friction drum for the rear wheel, I'm trying to keep the rear drive for this bike as low tech as possible without resorting to an side hung friction drive with a tiny drive diameter.


  2. HeadSmess

    HeadSmess Well-Known Member

    im thinking the belts you mention are the lil v belts like on my mill.

    the ideal thing. i contemplated V belt many times but was stumped by the lack of small sized belts that could take the size pulley i want without undue wear.

    unfortunately, getting these belts in my country is seemingly impossible.

    noone stocks them. to get them from gates directly requires some ridiculous postage fee because i guess dealing with small sales just isnt worth it. i vaguely recall $139 for a $5 belt.... unless i go into mass production and get a loan first...aint happening :(

    the ones i do require i have to order from the original supplier. five at a time to make it worth it. strangely i just had to replace one today. they do seem to be directional... six months perfect, flogged out the week after i flipped it around. could just be due to the way the "break in" wear develops and belt must remain the same way forever after. iunno.

    but yeah. v belts are ideal. the tensioner allows for a really simple clutch as well. id recommend a simple double reduction, can run slightly larger pulleys, meaning more friction area and less bending friction/wear. run a generator off the jackshaft. iunno. its a thought ;) but otherwise...good luck :)

    regards alignment...as long as the driven "off" side is in line with the driving "on" side... v belt shafts can be rotated relative to each other without tensioners/idlers. pretty neat :)
  3. KCvale

    KCvale Motorized Bicycle Vendor

    Barry likes this.
  4. LewieBike

    LewieBike New Member

    Well I can pick up the belt I want pretty easily from Amazon in just about any length. I'm doing this to get away from the fussy alignment nature of Glimer tooth-belts or 'cog belts', as this installation will be subject to small amounts of flex, also with the short run of the belt, about 12~16" center to center.

    And no, as far as making a GEBE clone drive, the engine I'm using is an older Echo 32 cc with an 8 mm OD output shaft ( 0.315"), which is a diameter that tends to be a little hard to get any pulleys made for. I'm on a budget, I have some fabricating skill, and the materials. I just was asking if anyone has used a PolyFlex before.

  5. Tom Allen

    Tom Allen New Member

    5MM? You are going to use a belt that is 1/5th of an inch wide to propel a motor bike?
  6. LewieBike

    LewieBike New Member

    My 72 cc Wacker saw powers a 12" abrasive disk through 1/2 steel plate with ease, that's nearly 6 hp through a 7mm wide belt, Gates Polyflex belts are not your regular car fan belt.

    Look them up
  7. Tom Allen

    Tom Allen New Member

    Can you tell me how long this belt would be? And approx what would be the cost of the belt.
  8. LewieBike

    LewieBike New Member

    Length is yet to be determined, I'm thinking roughly in the 600 to 950 mm length and about $15.95 to $19.00 for the belt before shipping.
  9. Tom Allen

    Tom Allen New Member

    I've noticed that belt shipping is always done by UPS--at least that is what I've found. The lowest rate is 11$. :veryangry:
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