3.5 HP small lawnmower engine

knexkid

New Member
Aug 3, 2008
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Hi,
I am very new to this, but I recently picked up off the curb a simple push lawnmower, 3.5 HP. I would LOVE to put this on a bicycle of mine. The easier the better, but I have seen that since it is a vertical shaft, things become a little more difficult. I also have a stationary bike adapter thing (like the ones here: Stationary Indoor Bike Trainer - Kinetic by Kurt ) I can hook that up to the rear tire, and if I could somehow put power to it, it would be just like a friction motorized bike (I have been able to simply hook that stationary bike thing, and put a cordless drill to it, and rode around my driveway at about a walking pace, obviously too slow) Any suggestions oh how I could rig up this lawnmower engine? I know I am limited due to the shaft, but let me know!!! Thanks!
 

Dave31

Moderator
Staff member
Mar 1, 2008
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Aztlán, Arizona
I have no ideal how to go about making a vertical motor work.

I will move this thread to the DIY forum.....you should get better help thier.
 

Unsolved Rubix

New Member
Jun 22, 2008
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Indianapolis, IN
Well, 1 idea I could see working is that you mount motor over the tire. you attach a wheel of some sort from a skate board and you run it on the sidewall. You just adjust the throttle on it and then blammo you are off.
 

knexkid

New Member
Aug 3, 2008
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I see, that might work...I would probably wear away the tire really fast...but still an idea nonetheless. Thanks...
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
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north carolina
Has anyone ever tried to run a lawn mowers on its side... My mower has the squeeze bulb and I often wondered if it wouldn't run sideways. I have had it almost on it's side cutting banks.

It might be that we could just move the gas tank and have it run horizontal. I don't have any idea I'm just asking.
 

Unsolved Rubix

New Member
Jun 22, 2008
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Indianapolis, IN
I see, that might work...I would probably wear away the tire really fast...but still an idea nonetheless. Thanks...
It wouldnt be that fast. You could run it off the rim if you wanted to see how it would work. You could set it up nicely if you put some time into the structure. Depending on the motor. there is a chance there is no throttle and if there isn't then it would an ALL on or off set up. I have actually put some decent thought into this idea before I just haven't decided start to spend the time on making it work.

and Lawn mowers can't run for a long period of time at much of an angle the oil and gas will find a way out...sometimes through the air filter and there is a big mess. So you are stuck with it being Vert.
 

knexkid

New Member
Aug 3, 2008
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I know it wouldn't be super fast, but I assume, if the engine is running at 3000 rpm, or 50 revolutions per second, and my skateboard wheel is about 2 inches in diameter (2pi for circumference) 50 * 2pi = ~314 inches per second. 314 inches per second = ~18 mph...which is not terrible if you ask me. Oh...and yes, it has a throttle, so the rpm is just an estimate....
 

Sianelle

New Member
Aug 2, 2008
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Hauraki Plains, New Zealand
Um..... A lot would depend on how strong the tyre sidewalls were. Myself I think trying to use friction drive on the side of a bicycle tyre with a 3.5Hp engine could wind up with your tyre going bang suddenly.
A vertical shaft engine really needs a twisted or 'round-the-corner' type belt drive in order to work properly on a bicycle.
This old patent drawing shows an example of how to use a vertical shaft engine to power a bike (the drawing is for a sidecar or a quad though so you'll need to make some changes).
 

Unsolved Rubix

New Member
Jun 22, 2008
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Indianapolis, IN
I know it wouldn't be super fast, but I assume, if the engine is running at 3000 rpm, or 50 revolutions per second, and my skateboard wheel is about 2 inches in diameter (2pi for circumference) 50 * 2pi = ~314 inches per second. 314 inches per second = ~18 mph...which is not terrible if you ask me. Oh...and yes, it has a throttle, so the rpm is just an estimate....
But that is a very Torquey 18mph so you should be able to handle hills like nothing.
 

TCBCustoms

New Member
Jul 20, 2008
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It may work, but dont forget the motor is a vertical shaft meant to be run horizontal. If you flip it the oil may not lubricate the piston. Also the carb will need to be turned. My friend put a push mower engine on a bike, it worked but it was HEAVY. It blew the head gasket so he scrapped it.
 

starrunner

New Member
May 12, 2008
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vintageboatplans.com
Vertical shaft engines just don't go with 2 wheeled bikes, but if you were determined enough, it could be done. The problem would be how far to the left off center that you'd have to mount the engine. Then you could use a belt pulley and twist it and go to a Whizzer type rear wheel belt sheave like the one on the pictured bike. Then you'd need to make some sort of idler pulley arrangement to act as the clutch. I've seen the pedals modified before to do this. And I haven't even mentioned making an engine mount. It could all be done, but with a lot of headaches.
 

aulit

New Member
Aug 24, 2008
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right now the motor is running horizontally (because the shaft is vertical)... you just have to pu it horizontally, but turn the shaft 90 degrees, so it will be horizontal too. It will be the same as any motor, except that you will turn the piston like... 90° to the front...
 
Sep 4, 2008
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hey everyone, i'm the guy large filipino directed your atention to on my space that used verticle shaft motor on bike. i want to asure you that it works quite well!!! tire wear is minimal, two summers, one tire. i used a cut down whell from an old shopping cart[solid rubber] for the drive roller bolted to the bottom of the motor shaft. cut it out with 1 1/2 hole saw. used a skate wheel on left side for idler. 25mph,by car speedo. tink
 
Sep 4, 2008
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starrunner, why don't you go to myspace/retiredtinkerer.com and check out my pictures and my video's of some of the bikes i've built with a vert shaft motor. i asure you sir that they are not hard to build at all and do work quite well. i came up with this so i could show my son and his friends what could be done with a little money and a little creativity. take care tink
 
Sep 4, 2008
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large filipino, thanks for the kind words and the intro to this forum,there are a lot of folks on here with some great ideas, a lot of them young people. just goes to show you that good old american enginuity is alive and well. if my idea for the vert shaft powered bike sparks some interest i would be happy to post directions and measurements for the build. it really is quite simple. going to do one this winter with no welding. vernon