Rack-mount, belt-drive, new build

knobb490

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Aug 13, 2010
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Hi all,

I've started a new rack-mount build. I'm documenting it on my blog which is http://enginepoweredbikes.blogspot.com

This is a belt drive using a 20" rim for a driven pulley, attached to a 26" mountain bike wheel. Take a look at the blog to see what I've come up with. I'd love some ideas on better ways to attach the pulley to the rim if anyone has any.

Thanks!

_______________________
So many freaks, so few circuses
 
Last edited:
My first question is "why do you want to go 14:1 ???"

The HF engine is rated at 3600 RPM. But, 400 RPM on a 26 inch wheel equates to 31 MPH.

So, a 3600/400, or 9:1 reduction gets you 31 mph. Your 14:1 would generate a 50 mph top end, assuming the motor can push you that fast, but, that kind of speed on a bike could be deadly.
 
My first question is "why do you want to go 14:1 ???"

The HF engine is rated at 3600 RPM. But, 400 RPM on a 26 inch wheel equates to 31 MPH.

So, a 3600/400, or 9:1 reduction gets you 31 mph. Your 14:1 would generate a 50 mph top end, assuming the motor can push you that fast, but, that kind of speed on a bike could be deadly.


I agree 100%. Speeding on a $99 bike ????????? PLUS, it draws too much interest from the law !!
 
I have to give credit though....

VERY ingenious with splitting the screws and using them to attach to the spokes!

Please keep us updated as to the progress on the setup here, I know I am interested in seeing it come to fruition!
 
Where's my dog - Thanks for the complement. I'm not sure that I won't be breaking spokes with the set-up but we'll see.

Loquin and Esteban -

What? My math is wrong? Dang, why didn't I pay more attention in high school? Okay, somewhere I must have gotten off track. If it isn't too much trouble, will someone please point out the errors of my ways? I have a lot of them according my family, but if you'll just focus on the math errors, I'm working on all the others.

Goal: Speed of around 20 mph @ 3600 engine rpm. There are a number of conversions that need to take place so that I'm dealing apples to apples.

Step 1 - Determine distance traveled by 26" wheel in one revolution. I think this is wheel diameter x Pi or 26 x 3.14 = 81.64 inches.

Step 2 - Convert previous answer from inches to feet. 81.64 inches/12 = 6.8 feet.

So one revolution of the tire will move the bike 6.8 feet. Now I need to determine how many feet I need to move in one minute to go 20 mph. Since I'm dealing with feet in terms of the tire rotation, I need to covert miles/hour into feet.

Step 3 - Convert miles/hour into feet/hour. 20 miles/hour x 5280 feet/mile = 105,600 feet/hour.

Step 4 - Convert feet/hour into feet/minute. 105,600 feet/hour divided by 60 minutes/hour = 1760 feet/minute.

So the bike needs to travel 1760 feet/minute to make 20 mph. Now I need to determine how many tire revolutions I need to travel 1760 feet.

Step 5 - I determined from step 2 that one tire revolution moves the bike 6.8 feet, so I divide the distance of 1760 feet by 6.8 feet/tire revolution. This gives me 258 tire revolutions per minute to go 20 mph.

Step 6 - The engine is rated at 3600 revoutions per minute. I need to reduce engine rpms to 258 tire rpms. How much reduction do I need? Divide 3600 engine rpms by 258 tire rpms to get a reduction of 13.95:1, rounded to 14:1.

Okay, please straighten me out.
 
No problem, please question anything I'm doing any time. I sometimes wonder about what I haven't taken into account and it helps to have someone looking over my shoulder!
 
New way to mount driven pulley to bike wheel

I've updated my blog with a new way to mount the rim-pulley to the host wheel. You can see it at http://enginepoweredbikes.blogspot.com/. It includes more photos and detailed description. Any thoughts/ideas are welcome.

____________________________
If you need a tool and don't buy it, you'll eventually find you've paid for it, but don't have it. -Unkown
 
I've updated my blog with a new way to mount the rim-pulley to the host wheel. You can see it at http://enginepoweredbikes.blogspot.com/. It includes more photos and detailed description. Any thoughts/ideas are welcome.


Nice work with the P clamps you mounted...

Just do a google search for the coupon and you will find it online!

If not, PM me with your email address and I will gladly send you a jpg of one for you to use!

Keep up the good work....
 
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