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Drill Motor Conversion

Old 09-28-2003, 12:17 PM
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Dezynco
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Default Drill Motor Conversion

I have an old Black and Decker cordless drill with a 12 volt motor. I believe that it is about a 600 size motor. If I use this motor for an aircraft, what kind of performance can I expect? Also, do I need to solder the resistors across the terminals to reduce interference, and which size resistors, etc. do I need for the task? I've never done this before, so any help would be appreciated.

(BTW, the reason that I disassembled the old drill is because it is cheaper to buy a new drill than to replace the battery packs, which were dead, so I figured I would be a fun experiment to use the motor as an airplane engine.)
Old 09-28-2003, 04:26 PM
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Lynx
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Default RE: Drill Motor Conversion

If you solder a resistor across the motor terminals all you're going to do is generate a lot of smoke heat and waste a crap load of battery power => Those are capacitors not resistors, HUGE difference. And small value ceramic will do (the little orange/beige disks. You can probably put a lot more than 12 volts through it as long as you don't run it at 100% throttle all the time and cooling is adequate. Experiment untill the engine starts to smoke <smirk>
Old 09-28-2003, 04:32 PM
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Dr Kiwi
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Default RE: Drill Motor Conversion

Unless you can find some identification numbers on the motor it will be impossible to determine what sort of motor it is, and the only way will be to try it out! It could be anything from nominal 6v, 7.2v, 8.4v or even 12.0v. If it is the last you'll have to use 10-12 cells or more to extract all its potential power.
For capacitors, you need one ceramic disc 0.047uF capacitor (Radio Shack Part #272-134) between the + and - terminals (make sure you put 1/16" heat shrink insulation on the wires so they don't short out. Ideally, you can also solder two more (of 0.01uF), one from + terminal to the casing, and the second from - terminal to the casing.

Cheers, Phil
Old 09-28-2003, 05:13 PM
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Lynx
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Default RE: Drill Motor Conversion

There are methods for determining the charactoristics of a DC motor but they're difficult to the uninitiated. You have to be able to measure the current while the motor is stalled, the voltage at the motor terminals while the motor is stalled, and be able to measure the voltage the motor generates when you spin it at a certain RPM. Also the no load current of the motor. All of those values allow you to generate (mathmatically) everything you could ever know about your motor, accept the max voltage it can take and the heat disipation ability of it because both of those depend on the environment it's in too much. There's a program called motocalc that can help you generate the numbers you need from readings you get and just about anything else you need to find out how an airplane will perform with a given motor.
Old 09-29-2003, 09:05 AM
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Dezynco
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Default RE: Drill Motor Conversion

Thanks for the help. Right, I ment to say capacitors, not resistors - there is a hugh difference! The motor has "JOHNSON" stamped on the case and some other marking that I cannot read. All the measurments on the motor show that it is a pretty standard size. I'll treat it as if it is a 600 because all the gearboxes, etc. from Hobby Lobby match up. I'll also put a 50 amp or larger speed controll on it. I noticed that anything lower than 12 volts won't even spin the motor, so I assume that it is a 12 volt motor. Does that sound OK?
Old 09-29-2003, 08:48 PM
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Dr Kiwi
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Default RE: Drill Motor Conversion

I suppose you could roughly work out the Kv of your motor by noting what speed it was supposed to run the drill at, knowing the original gear ratio and assuming the original rechargeable 12v input. I imagine you should be able, and might need, to run it on 12-14 cells or more - that way you might get ~300W out at 20A.

Cheers, Phil
Old 10-04-2003, 03:34 PM
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zxcv11
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Default RE: Drill Motor Conversion

Dezynco, see my other post here
[link=http://www.rcuniverse.com/forum/Electric%2F%2540_Trainer_Conversion/m_1177912/tm.htm]http://www.rcuniverse.com/forum/Electric%2F%2540_Trainer_Conversion/m_1177912/tm.htm[/link]

.....that motor will work WELL!![8D]

Bri

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