SpudFiles

So the other day I got a complete mini bike frame for FREE. I want to make it electric the only thing is how big of a motor to get. I was thinking a 36v 650 watt motor but will this be enough to push around 250 pounds at 20 mph?

650 watt is roughly ~0.9 horsepower.

250 pounds at 20MPH with a 1HP engine? Maybe, given a favorable wind.

yeah that is what i was affraid of. maybe i will just get the 750w or maybe the 1000w motor. any other ideas other than gas.

the best motor you can have is your legs
done be lazy

You should look into getting an inexpensive chainsaw...
They come in many sizes and powers.
And because they use chains, you can easily modify it to spin the back tire.

MountainousDew wrote:You should look into getting an inexpensive chainsaw...
They come in many sizes and powers.
And because they use chains, you can easily modify it to spin the back tire.

thats high-class ghetto right there

i would get the biggest electric motor you can buy

To bad the biggest motor is in the order of several thousand kilowatts.

Chainsaw is your best bet. New motors that size are very expensive.

yeah, I have an electric chainsaw, however, it's a plug-in chainsaw, so you'd have to mod it.

if it's a 24 volt system, you could always try getting a 36 volt controller, and extra battery, and run that motor, it may decrease it's lifespan a bit, but most people who run a motor like this don't have problems. overheat may be an issue on occasion if you're a heavy rider.

That's cool man, I've built an electric scooter; it was a fun build. It was only 250 Watts, but I added more batteries, a 2nd controller and motor for 500 watts. It pulls me pretty good, and I'm around 200 Lbs. If you weigh 250, that 650 should pull you around no problem, but you could always add an extra motor like I did. I posted pics in another thread already, but here...



I'm actually waiting on a 49cc starfire engine for my bicycle, I'm turning a schwinn point beach cruising bike into an old-school boardtracker. it's scheduled to show up tomorrow. I can hardly wait to start my build!

Good luck with that mini bike!

Oh one more thing, your speed is dependent on how many teeth the wheel sprocket has, the smaller the sprocket, the faster you go, but the motor has to work harder to get up to speed. the key is finding a nice trade off between top speed and torque. try to get a couple different sprockets and see what works to your liking

Any idea on gear ratios. I got a 60 tooth on the wheel right now and the motors all come with an 11 tooth sprocket. I got a 11 inch wheel in the back.

far_cry wrote:the best motor you can have is your legs
done be lazy

Haha Flintstone it. Im 105lbs I bet I could get it to 20mph

Wow, you are skinny! I'm 13 and I weigh 130 lbs...
Do you not eat?!

Im 5 feet tall and I eat a lot. I just have a metabolism faster than a 2000hp dragster

Well, For starters, Convert the Watts to Joules. with a 250 watt motor, you are doing 250 joules of work (or have the ability to add 250 joules of energy) every second

Assuming where you are is perfectly level, and theres no air, Ect, We can use the following (air resistance is proboably not a big worry. Just give a large margin of error)

To calculate Kinetic Energy (in joules), You do

1/2*Mass(kg)*Velocity^2

And by studing the Diagram of whats going on, we can see that

Kinetic Energy Initially (or Zero) + 250 = Kinetic Energy Afterwards

Now I dont know the masses, But if you do some relatively basic algebra, you can solve for velocity. This velocity is the amount of velocity you will gain every second, Or, To simplify it, The acceleration capable of your machine.

If this is wrong, Someone please god tell me. Im doing a project right now that requires all this stuff........