2 main design questions:

1) where to get a cheap electric motor powerful enough to do this?

2) how do you attach the motor to something as small as a skateboard axle?

any recommendations would be great, this is planned as a long term project, and budget shouldn't be too high....

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thanks,
david

 

For the motor , head over to your local scrapyard and digout a car windscreen wiper motor. These can give some decent power for little $.

You would obviously be gearing this down, so something like a worm gear might work well, or even a chain and sprocket setup.

Or, just switch to a petrol motor (line trimmer motor), but the problem is that you can't use the skateboard indoors. (mom would kill you either way, so yeah)

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the board would be for getting from the dorms to the classes... just thought it would be fun...

so where do i get a worm gear to attach windshield wiper motor to the skateboard?

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thanks,
david

 

i think the Windcreen wiper gear is already geared down with a worm gear system. It comes with the car itself. Nifty eh!

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so how do i attach a worm gear to a skateboard or any kind of axle? also, will this motor be strong enough to make this project work??

__________________
thanks,
david

 

The worm gear system is already in the wiper motor, it simply has a tapered shaft sticking out. You could attach a spocket to that with a chain drive to a sprocket on the rear axle, feeding either one or both back wheels. The problems are purely mechanical, fitting a sprocket on a tapered shaft won't be easy - you will probably require access to a lathe.

Wiper motors rotate very slowly, but you can increase the wheel rotation speed with suitable sprocket sizes - you might even have to have a couple of stages of gearing, due to the very small wheel size.

It would also be a good idea to feed the motor from 24V, rather than 12V, this will increase speed and power considerably - using a PWM speed controller would help to make it more 'driveable'. Wiper motors are often used at 24V volts, from all reports they seem quite happy that way.

As to the amount of power it will give, you need to try it and see - the motors can be got from scrapyards for very little money, get one and experiment.

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Hi Daviddoria

If your wheels are about 10 cm in diameter, and want to go a little faster than walking (4 KM/Hr), something like 10 KPH, or 166 MPM the wheels must turn at 530 RPM.

A radiator fan motor, with the fan may turn at about 1000 to 1500 RPM taking 15 to 20 Amp at 12V, enough power to impulse your vehicle at the desired speed.

The easiest way to transmit the motor power reducing the speed (is only my opinion) is via a friction drive with a rubber wheel attached to the motor shaft, (use something like a shock absorber rubber mount). With a diameter roll of 3.5 cm. at 1500 RPM you will get 10KPH.
Mount the motor over the wheel, pressing against it with enough pressure to avoid slipping.

With a 12AH 12V battery, a gel cell is safer, and using it only for short periods (3 to 5 minutes) it will last for 5 or 6 rides (assumming 20A ), but anyway the battery life will be very short) .

To justify this post in a electronic forum I would add a motor speed control using a PWM circuit and a power MOSFET , and a electronic horn or siren (just in case).

Regards and good luck.

 

thanks for all the suggestions guys!

what is a PWM circuit? yes yes, this will be very important (controlling the speed). i need some sort of a very basic throttle.

i am going home in like 3 weeks where i will hit the junk yard then i'll be back with more questions!

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thanks,
david