### Author Topic: DeWalt 18v motor  (Read 7386 times)

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#### DuckOfDeth

• Beginner
• Posts: 2
##### DeWalt 18v motor
« on: July 12, 2006, 08:28:20 PM »
First time post, as I run rc electric boats. I am installing a DeWalt 18v motor in a 36" boat, and currently have three 7 cell 3700MaH NiMH packs. If I run 2 of the packs, I am only creating 16.8 volts, not enough to really make the motor get the rpms that I want or need to turn a 51mm prop.

My question to you learned people, is if I run 3 packs at 25.2 volts, will I

a) be happy as a clam,

b) wish I'd bought a 820BB motor from Graupner, or

c) watch in horror as the DeWalt motor heats up and melts a hole in my cheap ABS hull?

I ask this of you because the fine boating folk really don't have a need for such a motor as it weighs too much, and at 1100 rpm/v, doesn't really tickle thier fancy.

I was hoping that  one of you might know how far I can overvolt this 1.5 hp monster?

Duck

• Supreme Robot
• Posts: 11,702
##### Re: DeWalt 18v motor
« Reply #1 on: July 13, 2006, 04:52:43 AM »
http://www.societyofrobots.com/actuators_dcmotors.shtml

What wattage is the motor rated for? You can calculate if your motor will overheat by multiplying the voltage you will use by the expected current. If that number is less than the rated wattage, it wont melt.

Is the motor casing heat sinkable?

Also, have you considering using a switching voltage regulator? They are similar to voltage regulators but much more efficient.
That one can only do 10W so you might need another in parallel. Do you know what the expected motor current drawn is?

So if you drop that 25.2V (or maybe higher with fully charged batteries?) to 21V with a switching regulator, and say your motor has about 2A draw, that would be about (25.2V-21V)*2A=8.4W

#### DuckOfDeth

• Beginner
• Posts: 2
##### Re: DeWalt 18v motor
« Reply #2 on: July 13, 2006, 02:17:47 PM »
Thanks for the info, most of it over my head (just a plumber, you see). Can't find wattage specs on the drill motor. And the available room in my hull won't allow a heatsink, however I can fabricate a water jacket to cool the motor if I find it necessary.
The motor is out of an 18v cordless drill, and I have used them to drill 1" holes through 4x4 lumber and the motor never gets hot, a little warm maybe, but never blistering hot. I'm hoping that by asking it to push 8 lbs of batteries and hull, that  it won't be reaching it's limits.
Thanks again for your response, and if I can find the wattage, I'll use your formula to figure it out. Meantime, i'll be launching tonight, hopefully to the tune of 'No Magic Smoke from the Boat Tonight",

Duck