Rack-mount, belt-drive, new build



loquin

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Jan 11, 2008
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2,210
2) Engine size, legality and visibility - No question that this engine is bigger than a 49cc and more obvious. In the community where I live, I have driven past law enforcement on two occasions. As I approach them, I shut down the engine and simply pedal past them. I don't know if I'm legal or not, or if they care, but I make an effort to use discretion when I know they are around.
The fuel tank and air filter up on top make the engine look even bigger. I've seen a small engine external diaphram fuel pump that you could use with this engine. You would have to drill/tap a hole in the crankcase, insert a hose nipple, and run a hose to the fuel pump. This way, you could place the tank at or below the engine level, making the engine less conspicuous. Likewise, you should be able to relocate the air filter with some judicious hose usage. Unfortunately, I don't think you'll be able to do anything with that big pull starter sheet metal...
 

knobb490

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Joined
Aug 13, 2010
Messages
37
Unfortunately, I don't think you'll be able to do anything with that big pull starter sheet metal...

I suppose I could simply remove the pull starter all together since I rarely use it. Most of the time I just throw the clutch lever to engage the belt which then turns the engine over and starts it up. With all those engine elements relocated, the visual bulk of the engine would certainly be reduced. But unless I get hassled from law enforcement, I'm planning to just stay stock for now.
 
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happycheapskate

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Nov 5, 2009
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1,392
I like your budget-build ULGE motor bike. That is badass!

I think your speed calculations are off because you forgot to include the tire.

With the engine mounted or a simulated weight, you can use chalk to mark a driveway, and measure out 1 or 2 rotations of the rear wheel with tire at desired pressure. This will be a truer reading of the wheel circumference in use.
 

knobb490

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Joined
Aug 13, 2010
Messages
37
20 inches isn't 20 inches

I meant to comment about this previously, but forgot. Thanks to Happycheapskate, I'm reminded about it again. I was inspecting the driven pulley (bike rim) attached to my rear wheel and had a tape measure nearby. I decided to measure the diameter of the pulley and learned that my assumption about the bike rim pulley was wrong.

What I thought was a 20 inch rim is actually 16 inches. It's the outside diameter of the bike tire that's 20 inches. So here I was, thinking I had a 20 inch rim with a drive ratio of about 13:1, when really, I'm at about 10.5:1 That's probably part of the reason I'm so far above off my original goal of 20 mph top speed. Other parts of the reason may be that the engine is running faster than 3600 rpm, and Happycheapskates comment about the 26" wheels.

I'm going to take his suggestion to measure actual distance of one or two rotations on the 26" wheels and see how it all comes out.

By the way, does ULGE stand for Utility, Lawn, Garden Equipment?
 
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happycheapskate

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Nov 5, 2009
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Yes, that is what I meant, Utility Lawn and Garden engine, as compared to automotive or motorcycle engines.
There are lots of home built road legal full size motorcycles that use large lawn tractor or generator engines. Check your local laws.

http://www.youtube.com/watch?v=YtaY4Zg0hNs
Street motorcycle with hydrogen generator

http://www.youtube.com/watch?v=Trlp6aNDN24
1972 motorcycle with air cooled diesel generator engine swap
 

knobb490

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Aug 13, 2010
Messages
37
It's been a few years, but I recently made some changes to my belt drive bike. Loquin suggested a centrifugal clutch, but I couldn't find one with the pulley dimensions I needed so I built my own using a comet clutch from Amazon to start with. I found that snap rings on the clutch allowed me to remove the sprocket from the bell. I then purchased a cast iron 1.5" pulley from eBay and tack welded it to the bell housing with both the bell and the pulley on a 5/8" shaft to keep them in alignment during the tack welding. In operation, to reduce strain and heat build up on the clutch, I start off under pedal power, then spool up the engine to engage the clutch while I'm already moving. I've only put 20 miles on it, but it's working great so far. I like the simplicity the centrifugal clutch brings to riding.
 

Dirt girl

New Member
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Jan 26, 2021
Messages
4
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
Hiya!
 
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