Drill motors?

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huntercook
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Joined: 02/18/2008
Points: 8

Howdy.

Sorry if this is really dumb; I'm a noob. Short version: would the motor from a cordless drill be suitable for an ebike?

Specifically, I'm looking at the DeWalt DC900 36v drill, which is allegedly rated for 750W and is going (w/o battery) for about $70-80 on ebay. That strikes me as a lot of power for not much money. The speed controller is in the battery, not the drill, so that's a bit weird, but since I figure I'd be using those packs (DC9360) anyway, it doesn't seem like a big deal. In fact, to my rather uninformed eyes this looks like a really easy way to build an ebike. Buy a drill, battery, and charger, cut the drill up into 3 pieces (battery mount, handle/trigger, and motor), mount the pieces and wire them together, get a rear wheel with an extra freewheel on the side across from the gears, put a sprocket on the drill and chain it up, and you've got a 1hp 36v ebike.

This seems too easy and too cheap for people not to be doing it all over the place, especially when 36v ebike kits are running $400 and up. So, what am I missing?

The next question is whether one could wire multiple batteries up to this thing. I'd be interested in parallel-only options (just for range, although I'm not totally unwilling to swap packs as they die), but even more interested in going up to 72v if you guys think the motor can handle it. Also, if anyone's interested, please head over to the controller forum where I'm asking about using the DC9360 packs as motor controllers, not necessarily in conjunction with the drill motor.

Thanks

Hunter.

p.s. Does it strike anybody else as really strange that the drill kits (drill, charger, and battery) go for $450 on ebay while you can get the three components separately for less than half that?

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IbeRKT
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Joined: 11/08/2007
Points: 50
Re: Drill motors?

Drill motors tend to run at very high RPM's I'm not sure about the 36 Volt But I know that the DeWalt 24V Hammerdrill Motor runs at 21,000 RPM (way to fast for an E-bike). To be able to use that in a Bike you would need to gear it down a lot. You would probably need a two stage gear reduction through a jack shaft or something like that for it to work at all.

I know that the Battle Bot guys will sometimes use these motors for their lighter weight robots but they also use a gearbox to get the RPM's into a range that they can work with.

You can get a gear box for some of the Dewalt Drills at robot market place http://www.robotmarketplace.com/products/dewalt_gearboxes.html
(but I don't think that they have one for the 36 volt drill)

But even with the gear box I just don't think that the Drill motor will have the power needed to run a full sized E-Bike.

IMHO the Drill motors may be OK for something smaller like a Stand-up Scooter, but even that may be pushing it.

spinningmagnets
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Joined: 12/12/2007
Points: 295
Re: Drill motors?

The DeWalt drill may be somewhat "heavier duty" than the Ryobi, but its been my experience with tools that they are built to handle a certain constant duty load, and a temporary peak load. I think if you try a drill (geared down) you will be disappointed after a few weeks. Imagine drilling for a constant 30 minutes through 4 X 4's without even an occasional few seconds for the bearings and motor to cool off.

Here are 3 circular saw bikes:

http://www.austinev.org/evalbum/176.html
craftsman 5425
http://www.austinev.org/evalbum/180
skilsaw 5250
http://www.austinev.org/evalbum/462
skilsaw 5150

Circular saws already have a gear down built in, I'm guessing about 2:1 (making off-the-shelf gears possible), plus its easier to adapt a small gear to the shaft. A saw will be much better than a drill, and even then you may still end up wanting something better soon.

LinkOfHyrule
LinkOfHyrule's picture
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Joined: 10/17/2007
Points: 730
Re: Drill motors?

They're right. Drill motors aren't built for constant load OR efficiency. Just power and torque. I'd stick with a proper scooter/bike/moped motor.

Circular saws can handle continuous load better, but most a series-wound and not very efficient.

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huntercook
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Joined: 02/18/2008
Points: 8
Re: Drill motors?

Thanks a ton everybody. I'm happy to not run down a bad idea.

I am still tremendously interested in the idea of using the DC9360 battery packs to run brushed motors without controllers. There's a V forum posting about it here, but probably the best discussion going on it is over at endless sphere. I think it's really exciting.

Thanks again

Hunter

markzoes
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Joined: 08/27/2017
Points: 6
Re: Drill motors?

Helpful thread.

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