Poly Chain sounds good. The larger pitch (60% larger pulleys) is a disadvantage but the greater load capacity might allow higher loads and
lower tooth count which might reduce that disadvantage.
If anyone knows the load capacity of 5mm x15mm HTD compared with 8mm x 12mm Poly Chain or can point me to a direct comparison it would save me looking it up.
Goodyear Falcon PD Belts and Pulleys are a Drop-in replacement for Gates Poly Chain GT2. Their Pulleys Cast are Iron or Steel Construction.
http://documents.kellysearch.com/pub/Ha ... 01/22.html
Click on the image for a full-size display:
Unfortunately Gates and Goodyear Pulleys are useless for ebikes unless 5lb and up driven pulleys in a reasonable size and a limited range of sizes are acceptable:
60t 5 lbs:
http://kscdirect.com/item/GAT%2B7718-10 ... -60S-12%0A
Product Description: 8MX-60S-12 2012 SPKT
Category Hierarchy: Industrial Power Transmission -> Synchronous Metal -> Poly Chain GT2 Sprockets -> 8mm Pitch Sprockets, P.N. Series 7715 & 7718 -> For Belts 12mm Wide
Markets/Applications: Use with Poly Chain GT2 Belts or Poly Chain GT Belts.
Number of Grooves: 60
Belt Note: Sprockets for Poly Chain GT2 belts are available in 8mm and 14mm pitches. Abbreviations used for sprocket material: GI=Gray Iron, DI=Ductile Iron, SiS=Sintered Steel, CI=Cast Iron.
Weight (Lbs.): 5.02
Fortunately Pfeifer Industries
sell and produce pulleys in a much wider range of sizes than Gates or Goodyear and aluminum is one option. At $70 per hour custom made (if necessary) even in quantities of one is probably an affordable option.
Stock and Custom Pulley Design / Machining - Prototypes to High Volume
Custom timing belt pulley manufacturing is our specialty. We also stock an extensive inventory of 5mm HTD, 5mm PowerGrip GT, 8mm HTD, 8mm PowerGrip GT2 or 8mm PolyChain GT pulleys.
As a master distributor for Continental ContiTech, we carry a large inventory of timing belts and can fulfill any other power transmission belting needs.
Bourn & Koch CNC Gear Hobbing
~Hobs and tooth ranges currently available
* 5mm HTD, (17 Tooth through 200 Tooth)
* 5mm PowerGrip GT, (16 Tooth through 200 Tooth)
* 8mm HTD, (14 Tooth through 140 Tooth)
* 8mm PowerGrip GT2, (22 Tooth through 140 Tooth)
* 8mm PolyChain GT, (14 Tooth through 140 Tooth)
* Additional hobs available upon request
Material Type: 6061 Aluminum
Also FYI Contitech SynchroChain is a direct replacement for Gates PolyChain GT.
Pfeifer Industries and Continental ContiTech announce their partnership to sell the Contitech SynchroChain timing belt as a direct replacement to the GatesÂ® PolyChain GTÂ® timing belt.
Pfeifer has an the nicest Belt Length/Center to Center Distance Calculator I've found plus some handy pdf's:
http://www.maxtorque.com/calctool/cente ... startx.asp
http://www.pfeiferindustries.com/timing ... charts.htm
Belt Length and Center to Center Distance Calculator
Two of the Four Pitch Diameter (P.D.) & Outside Diameter (O.D.) Charts
http://www.pfeiferindustries.com/pdfs/5 ... d%20OD.pdf
http://www.pfeiferindustries.com/pdfs/8 ... and_OD.PDF
And some excellent Technical information and downloads:
http://www.pfeiferindustries.com/power_ ... ations.htm
How realistic is it to use plastic .25 (#25) or .375 (#35) chain as a first stage with a 3220?
I think Poly Chain might be a better choice if you have some additional space. Matt said 26t 5mm x 15mm HTD pulleys with high belt tension worked for connecting dual 3220's (13 belt teeth contacting the pulleys) so something like 20t/60t with shafts about 6" apart would probably work (?) or maybe even something like 16t/64t (?).