Motorized Skateboard...?

Kurt_ · Post by **Kurt_** » Thu May 29, 2008 2:06 pm

Well I want to build something cool and unique that will double as a mode of transportation (All ideas welcome).

I figured I'd make a motorized skateboard, an idea I've had for a good 5 years.

It's going to be electric, powered by a 500W electric motor (like the PopSci one, why reinvent the wheel?

) and lead-acid batteries (most bang for my buck). It will hopefully incorporate some sort of regenerative braking systems as well. The body will be a fibreglass construction based on steam-bended plywood.

The problems: (Cost is not a problem, I WANT to spend money on this thing. Just not if I don't have to.)

1) How does regenerative braking work? Is it simply applying a force to the motor in the opposite direction of the motor's travel? (I'm aware the current direction would first have to be switched)

2) Steering. I want something deviated from the typical skateboard (Think snakeboard-style steering) that won't cause me to go wild hitting a pothole or rock at 20 mph. Also, I want to be able to steer, unlike typical skateboards.

3) Where to get flat (3" or less) Lead-Acid batteries that would have enough juice to power this thing for a good 15 miles.

4) The Brakes. Regen is for slowing down more than stopping, is it not? Would I need another braking system? What is a good one to use? Disc brakes seem good but I'm not sure what to search for when looking for 6" or less disc brakes.

DK · Post by DK » Thu May 29, 2008 3:17 pm

500 Watts

That's gonna be a tad dangerous but fun. I'm thinking of bodging an electric tricycle so I can go cycling tour this summer. Just don't like hills so that's where the electric motor will kick in. By law it can only be 250W though otherwise I need a bike licence and insurance.

Battery wise, most EV people seem to be using the new Bosch LiPoly batteries as they're small, light and seem to pack quite a bit of charge. May be expensive though depending on how many you need.

And btw, regenerative breaking is pretty hard to do. Only seen one electric bicycle with it so far.

vskid · Post by **vskid** » Thu May 29, 2008 4:52 pm

http://www.instructables.com/id/Electri ... ain-Board/

Thats a nice overview, it'll probably give you a lot of ideas.

Regenerative braking seems to mostly depend on your motor controller.

Kurt_ · Post by **Kurt_** » Thu May 29, 2008 5:08 pm

I thought I'd just have a relay. One way I get power (which will OBVIOUSLY be adjustable, perhaps through a switching regulator), then when you switch the relay on, it reverses the current to the motor.

Vskid: That's what I'm aiming for, except I was going to build it myself. I'm not sure how trucks work, but I was thinking I'd have a solid axle and an actual way to turn. Perhaps I should have trucks and an actual way to turn (for sharper turns) instead?

ghosstt · Post by **ghosstt** » Thu May 29, 2008 5:49 pm

Kurt_ wrote:I thought I'd just have a relay. One way I get power (which will OBVIOUSLY be adjustable, perhaps through a switching regulator), then when you switch the relay on, it reverses the current to the motor.

Vskid: That's what I'm aiming for, except I was going to build it myself. I'm not sure how trucks work, but I was thinking I'd have a solid axle and an actual way to turn. Perhaps I should have trucks and an actual way to turn (for sharper turns) instead?

Not really sure how that would work. You put a lot of pressure on the trucks when you are riding a skateboard. Even with a solid axle, it would be tough to move it, and even if you did, since the skateboard is so thin, you would barely get any movement. You might want to just stick with the trucks.

Kurt_ · Post by **Kurt_** » Thu May 29, 2008 6:07 pm

Think I should go gas? The idling RPM is the same as the max on the electric motors?

Or should I go with something completely different? Motor on a bike?

I'd feel a little safer riding a bike than a skateboard any day.

Chainsaw + Bike = ?

vskid · Post by **vskid** » Thu May 29, 2008 6:44 pm

Kurt_ wrote:Think I should go gas? The idling RPM is the same as the max on the electric motors?

Or should I go with something completely different? Motor on a bike?

I'd feel a little safer riding a bike than a skateboard any day.

Chainsaw + Bike = ?

I just found on a site that 3000 RPMs is an average max motor speed on scooters. Electric can be geared higher because they have high torque at low RPMs a gas engine couldn't dream of operating at. I'd say go electric if you make a skateboard, electric motors are smaller for what you need than gas engines.

Chainsaw + bike would be cool, but starting off from a stop probably wouldn't be the greatest for the engine.

gamecube6 · Post by **gamecube6** » Thu May 29, 2008 7:01 pm

Kurt_ wrote: Or should I go with something completely different? Motor on a bike?

I gotta say, that would be pretty sweet. It'd be like a pre-motorcycle for immature children...

... not that that's a bad thing

Post by **Triton** » Thu May 29, 2008 7:50 pm

you can get 50ah li-polys on bateryspace, but i think they are like 250$ each, probably cheaper lower capacity ones too

ghosstt · Post by **ghosstt** » Thu May 29, 2008 8:06 pm

I've tried the motor on a bike. Created a custom frame from a few bicycles, and mounted a weed whacker to it. I was too heavy, but with a stronger motor, it would have been perfect.

Grandmasterjimmy · Post by **Grandmasterjimmy** » Thu May 29, 2008 8:22 pm

Build a hoverboard. Rubber + skateboard with no wheels + lawn mower engine.
I'm not joking, I seen one in real life. it xan glide on water too,

ghosstt · Post by **ghosstt** » Fri May 30, 2008 4:34 pm

Grandmasterjimmy wrote:Build a hoverboard. Rubber + skateboard with no wheels + lawn mower engine.
I'm not joking, I seen one in real life. it xan glide on water too,

Yup. In one of those how to videos that are on the top of the forums, it was build a hoverkart. it was from make magazine, and it was pretty cool. No steering, but w.e.

Post by **bicostp** » Fri May 30, 2008 6:03 pm

I suggest you take a weedwhacker or chainsaw motor and put it on a BMX or mountain bike frame. But in that case you might as well track down an old moped.

Check the road laws in your state/province. Around here, anyway, anything with 3 or fewer wheels requires a motorcycle license and registration to operate on the road.

Another potential issue is 2-cycle engines. With them, you have to mix the oil and gas together in the right ratio to not ruin the engine. You can't just mix plain motor oil into the gas, you need 2-stroke oil. You can get some here. (Click "Lubricants" on the nav bar and it will be the first thing on the list.) 4-stroke engines don't have that issue.

I know 4-stroke lawn mower engines are in abundance, but never put a motor on its side unless it was designed for that kind of use!! At best, you'll flood the combustion chamber, stall the engine, and gas will pour out of the carb. At worst, you'll seize the engine in a matter of minutes, because all the oil drains away from the crank.

You might find these videos interesting:

http://youtube.com/watch?v=uruaRsCHvk4
http://youtube.com/watch?v=uEykJadNyHU

Rekarp · Post by **Rekarp** » Fri May 30, 2008 6:46 pm

You can get 2-cycle oil anywhere. You just have to mix it in the right parts.

I thought I'd just have a relay. One way I get power (which will OBVIOUSLY be adjustable, perhaps through a switching regulator), then when you switch the relay on, it reverses the current to the motor.

Most DC motors will reverse if you swap the polarity. So just make sure you get a motor that will only spin one way.

For gas look for edgers like this one

http://www.pinnaclepower.co.uk/uploads/ ... _Edger.jpg

They go pretty cheaply and they are already side mounted.

ghosstt · Post by **ghosstt** » Fri May 30, 2008 10:21 pm

Ya, you will need something side-mounted, and at least 5.5 HP. (considering your not below average weight?) I think But don't 2-strokes give out more torque than a 4-stroke? So a 2-stroke could be a better way to go. Mixing the oil isn't to bad.