GEBE belt drive belt pitch specs

I have been intersted in getting the GFBF belt drive bicycle engine kit-less engine-in the near future,and was wondering if anyone knows the spec's
of the drive belt/driven spoke ring;meaning,the width of the belt,and cog pitch of belt/driven spoke ring???

 

Don't have those specs here as I recall; have we been introduced?

 

The GEBE drive belt is 11/32" wide and 64" long. I measured the length of the belt by pressing it as flat as I could and stretching it as long as I could, then multiplied by 2. I'm not sure that's how belts are normally measured, but if you cut the GEBE belt and stretched it all the way out, it would be about 64" long.

There are some rough specs on the GEBE drive ring in [post=68940]this article[/post] written by a lovely chap who hangs out on MBc. However, the GEBE drive ring is a complex shape, and if you want more dimensions you must specify which ones you want.

I will happily post the cog pitch of the GEBE belt and drive ring if you describe (clearly) how to measure that. I don't know what kind of setup you are considering, but GEBE does sell gears with different tooth counts which already mesh perfectly with their belts. If you could get a GEBE gear on your engine's drive shaft, it might make things easier...

-Sam

 

Sam, the pitch is simply the center to center distance between pulley teeth. It is a function of the pulley type used.

GEBE originally used xl type pulleys and the pitch on those the pitch is .20". The newer kits are HTD (high torque design) type, and I don't know the pitch, because I have the old style. They are metric and come in 3mm, 5mm, 8mm pitches. 5mm is closest to the xl pitch at .197", so it's probably that one.

Belt width on the old xl style is 3/8". If the new ones measure 11/32", that converts to 9mm, which is a standard HTD width, and very close to the original xl type.

I've estimated the number of teeth on my xl spoke ring as 266, for purposes of calculating gear reduction. This includes the blank spots, and is a function of measuring the diameter and calculating from there. It's only an estimate.

 

My 2007 HTD replacement belt is marked Gates 16355M09K. Deciphering the code, this likely means
9mm wide, 5mm tooth pitch, 1635mm length

I have the same vintage belt, bought at the same time, on my bike. The belt currently has 1150 miles, and has stretched approximately 6mm. This slack is taken up by the idler pulley on the motor.

The above referenced article lists the OD drive ring diameter as 17". The 17" measurement is to the outside flange that serves as a keeper for preventing the belt from falling off the side of the ring. The diameter of the drive ring which is in contact with the belt is actually a little smaller at 133cm.

The drive ring has corresponding 5mm pitch teeth molded into the contact surface. However, the teeth are only molded into 90 degrees of the ring, at every other 90 degree interval. This allows the drive ring to be molded as a single piece (missing teeth areas needed for mold release).

The critical dimension is making sure the motor pulley is at a correct distance from the wheel axle, and the motor pulley diameter is about the same as what GEBE sells. If you buy an equivalent GEBE engine somewhere else, then the kit will take care of all the critical dimensions with no modification needed.

 

Thanks for the information on the GEBE drivebelt, Ray!

Now do you know where else we can purchase these drivebelts besides GEBE?

 

GEBE has a propritary belt that has been reinforced with Kevlar threads and I believe you can only get this belt from GEBE. But you can find the same belt minus the kevlar at suppliers like McMaster Carr or a google search for metric timing belts should produce any number of dealers/sources

ocscully

 

'scully is correct...the gates number has a "SPCL" suffix...there may or may not be other belts that have similar width & pitch, but this one is made specially for golden eagle.

dennis gave me some (approx) ratios that might help.

drive-gear:drive-ring

14t=1:19.1
13t=1:20.6
12t=1:22.3