SpudFiles

So right now I'm in the process of designing a motorboard (basically a beefed-up skateboard with an engine) powered by a 49cc chainsaw engine. The thing will have two wheels in the front that steer when the front half of the board is leaned back and forth and one back drive wheel that stays perpendicular to the road. I found some tires within the size and price range I want but am not sure if they'll survive the wear and tear of what they'll be facing. The front wheels would be from a kid's Razor dune buggy designed to hold 120 pounds plus the weight of the buggy and go about 15 mph, and the back wheel would be from an electric scooter designed to hold an adult but also go only about 15 mph. My board would be going about 25 mph and weigh about 180 pounds with me on it (I'm a pretty skinny guy).

There's also the question of whether or not #25 chain is enough to transmit the power from the engine to the drive wheel through a series of sprockets. My math said it will, but I left a lot of factors out.

Front wheels:
http://www.monsterscooterparts.com/du.html
Rear wheel:
http://www.partsforscooters.com/119-33_ ... gory=98780
Video on which I'm basing my design:
[youtube][/youtube]

Pretty cool. I agree with you on wheel choice. I believe they will hold up. I wouldn't strap my feet into it though, impossible to bail. How do you control speed?

The chain has to be rated for both the speed and force. The force is limited to the torque the engine will produce regardless of your weight. You want a high speed chain for the engine sprocket.

Some commercial boards from the 1980's used a throttle in a tennis ball. You hold the ball and press the button. This was a safety as if you dropped the ball such as falling off, it returned to idle. An ankle band kill switch is recommended.

Yeah I would just have a little loop to stick my toes under, not those snowboard-style bindings in the video. The controls would be a pair of levers on a handheld bar with one lever controlling the throttle and the other the brakes. Given that a 49cc engine produces about 2.5 hp at 12000 rpm, some very basic math said #25 chain should survive the force. That being said, though, the horsepower is just an educated guess and the rpm is with no load.

Hey thats awesome
I think Im going to build one my self
How much is your budget?

Only about $200, but I've already got a few parts, most importantly the engine

how much do you think an chainsaw engine can cost?

I got one for about $50, but it was in pretty rough shape when I got it. If you look around ebay long enough you can probably find a used but running 33cc engine for about $60-$70. A 40cc+ engine in the same condition will probably run about $80.