GEBE Gearing Questions

[Dr. J.]

How many teeth are on the motor and wheel pulleys? I am trying to figure the gear ratio. Also, does GEBE use a gear reduction where the motor joins the mount or is it a direct (inline) fit?

Thanks,

Dr. J.

 

[bamabikeguy]

There are three available, that screw onto the drive shaft.

Mountain 11 teeth, for acceleration and pull

Standard 12 teeth

Highway 13 teeth for top end speed and highest mileage.

On my demo bike I let folks use I have the standard, and I race along side them with the highway gear.

I'll make pix tomorrow.....so you can see close up the grooves in the belt, the grooves in the spoke ring, and the different gears.

I'll also take a picture of the drive shaft, so you can see how it is attached.

 

[Hugemoth]

Dr. J.

Bamabikeguy didn't address the gear reduction question. There is no gear reduction where the engine joins the mount, it is direct drive (through a centrifical clutch) to the small drive gear/pulley. Also the big ring that snaps on the spokes doesn't have teeth all the way around so it would be difficult to calculate the exact gear ratio.

Moth

How many teeth are on the motor and wheel pulleys? I am trying to figure the gear ratio. Also, does GEBE use a gear reduction where the motor joins the mount or is it a direct (inline) fit?

Thanks,

Dr. J.

 

[bamabikeguy]

Phsew, gotta luv them bachelor of science guys, I was wondering how to explain the gaps in the spoke ring.

Simple explanation, if you didn't have 3 gaps between the 3 toothed parts, the dam thing would take off when you cranked it.

The gaps in the spoke rings are basically "idle" position.

 

[Dr. J.]

Thanks guys for your replies. If I could find the working diameter of the drive sheave (on the motor) and the driven sheave (on the rear wheel) diameters, the ratio could be found. Would anyone have the measurements handy? I have an ongoing rear engine project and would like to find a place to start concerning gearing.

Also, can you take off from a dead stop without pedaling using the GEBE setup?

Dr. J.

 

[bamabikeguy]

Also, can you take off from a dead stop without pedaling using the GEBE setup?

That part is yes, but it is not a big deal to get up to full speed, and peddling maybe 5 times around is enough for the engine to take over.

 

[bamabikeguy]

Here are those pix, of the gear/belt in various stages.

Note: the bottom right is Rocinante, my traveling bike.

Take along a small can of WD-40 or sewing machine oil, a small tad behind the tension arm keeps that road grime from building up, disrupting "free motion".

The plastic cover hides the grime, but every 500-700 miles take a peek.

 

[turkeyssr]

Calculating the gear ratio

Couldn't the gear ratio calcultion be done via the diameter of the pulley connected to the engine versus the diameter of the spoke ring?

 

[srdavo]

Re: Calculating the gear ratio

Couldn't the gear ratio calcultion be done via the diameter of the pulley connected to the engine versus the diameter of the spoke ring?

yes sirreeeee!

 

[mppardee]

24.6:1 gear ratio?

I was considering the GEBE but wanted to know the gear ratio. I found on their site a passing mention of 148 teeth on the drive ring, and http://www.norcom2000.com/users/dci...ent/moto_bike_page/episode006/episode006.html seems to indicate that only 2 out of the 4 quadrants of the drive ring are covered with teeth. So that would be like 148*2=296 teeth total.

With a 12 tooth gear on the motor, that would be 296:12 or 24.6:1 gear ratio. That would give a theoretical absolute maximum top speed on a 26" wheel of:
8000 revolutions/minute * 26/24.6 inches/revolution * pi * 60 minutes/hour / 63360 inches/mile = 25.15 mph max speed. If the engine is at 7000 rpms then speed is only 22 MPH.

The GEBE site quotes top speeds for the 35cc robin-subaru with the 12 tooth at 27-28 MPH - how is this possible without revving the engine to 9000 RPMS?

As far as I can tell the GEBE does not have any freewheel so if you have the throttle on and you are going down a big hill wouldn't the engine brake you at max RPM and never let you go faster?