Drill motors - how much can they handle?

Discussion in 'Electric Bicycles' started by Tinker1980, Feb 25, 2012.

  1. Tinker1980

    Tinker1980 New Member

    I got bored a bit ago and tore apart two of my old cordless drills, one a 14.4 Volt B&D, the other an 18 volt Harbor frieght special. The B&D had a bad battery and had been laying around a while, the 18V HF drill I ended up giving the battery and charger to my brother in law.

    Both of these motors and their gearboxes look nearly identical - the only difference is the better clutch (More selections) on the B&D drill, and the B&D drill has some plastic gears, while the HF drill (The cheaper one!!) has metal gears. They both have brushed DC motors and two stage planetary gear reduction. They also both have a "speed control" that consists of a trigger housing, and a transistor screwed to a heat sink.

    Questions are these: How powerful are these motors? Hooked up to the 12v battery in my truck I can't grip the chuck and stall them. How long to they run before getting too hot?

    I've been kicking the idea around of using them on a motorized bike, and building or buying a brushed motor controller. I'm sure there are those who will tell me it won't work, and if you do please provide exaples... and remember that someone, somewhere, once said that putting a motor on a bicycle was a bad idea too.

  2. I don't think they will last very long, but what have you got to lose? I suspect the brushes will wear out quickly in sustained use. Are the brushes difficult to change? It is certainly worth a try as long as you don't spend a lot of time and money getting the gears/drive system worked out. Let us know how it goes.
  3. keatonx

    keatonx Member

    a few years ago i made an electric scooter with one. The only problem is that the drill battery dies after 10 minutes. I also made some small gocarts with drill motors (one was one of those pedal john-deere ride-em tractors for toddlers that i got off the curb). They went about the speed of someone running, but at the time i was in grades 5-7 and really light.
  4. Tinker1980

    Tinker1980 New Member

    I wouldn't be using the drill batteries... just the motors. I'm working welding a sprocket to a 3/8" shaft, griding a hex into the shaft so I can easily attach it to the drill motor. I left one running for an hour on a deep-cycle 12v battery and it didn't seem to overheat it.
  5. keatonx

    keatonx Member

    ive had one start smoking once, though. I was running the chuck against the ground to see how powerful it was. I wasn't even running it for any length of time or slowing it down much. All the sudden massive amounts of grey smoke start blowing from the vents for the cooling fins in the motor. It smelt like fried circuit boards. I have no idea what caused this, but i ran the motor waaay harder after on my go cart and nothing happened.
  6. keatonx

    keatonx Member

    The speed controller that comed with the drill will work fine, ive seen ones that are rated up to 20 volts and 15 amps, and most are pretty close to that.
  7. sparky

    sparky Active Member

    Nobody ever said that putting a motor on a bicycle was a bad idea.

    Also... I'd stick to 18V or higher.
  8. HeadSmess

    HeadSmess Well-Known Member

    you can get 24v 3ah packs made up for roughly $100, depends who you talk to.

    metal gears are of course the better way to go.

    some drill have better speed controls than others and they arent terribly hard to make/find anyway.

    the higher the voltage the less current you have to deal with for a given amount of power, ive ran drills with 48 volts before, with not much more heating than normal. a standard cheap 24v scooter goes ballistic with 48 volts @ 15A :jester:

    basically voltage = speed, current = torque.

    batteries will always be the killer once you have the basic mounting sorted.

    a hi-end drill such as a dewalt even has a 3 speed box :) and will break wrists in low gear... :eek:

    if you wanna get extra tricky, replace the lousy brush motors with super duper brushless types ....
  9. Cavi Mike

    Cavi Mike Member

    Plastic gears absorb shock better and that's why you'll see them in Dewalt and B&D drills. Dewalt drills are known for having the most durable gearbox of any drill manufacturer and I can personally attest to that. I've busted their chucks, I've fried their motors, I've blown their speed controllers and I've shattered their cases but not once have I busted or seen a busted gearbox. In my honest opinion, it's the only good part of a Dewalt drill.

    Also, metal is no longer automatically better than plastic. Plastics have come a LONG way in terms of strength and durability. The exact opposite can be said about metals. There always seems to be some new, cheap way to manufacture small metal parts(like gears in drills) involving metals that either come in powder form and/or have extremely low melting points, neither of which make for a good gear. That's what you'll find in a cheap drill because they're cheaper to make than a properly machined plastic gear.

    As far as the motors, they're really just disposable motors. Once the brushes wear out, it's time to replace them. Plus these are 3-pole motors and they're not great for torque, they're designed for RPM and they'll overheat very quickly if they're stalled or running at a low RPM. And let me tell you, 15amps is nothing when it comes to these motors. In a stalled-out state, I'm sure that motor will draw 30-40 amps no problem.