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Old Nov 19, 2014, 04:41 PM
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mrbassman's Avatar
Chula Vista, Ca.
Joined May 2006
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Question
Johnson Motors

One of my friends gave me a Johnson motor. It says on it HC970, has the 1/4 inch shaft, and is a brushed motor. That's all I know about it, and that's more than he knew.....How do I find out if it's a 6 or 12 volt motor, if it's timed differently forward and reverse ?? Not sure what I have here. I'm assuming an Mtroniks 40A esc would be ok for this, but once again, I'm not sure.

Thanks,
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Old Nov 19, 2014, 05:35 PM
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Joined Dec 2004
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The timing of the motor would be zero if the motor turns the same RPM in both directions. As for voltage of the motor, you would have to know what the motor run RPM’s at maximum efficiency and then see what voltage will run the motor at that RPM.

Once you know the voltage of the motor you can run it under a static load with a car fuse in line, and keep increasing the amperage of the fuse until it stops blowing to find the amp draw. If you have a shunt amp meter you can direct read the amperage of the running motor.
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Old Nov 19, 2014, 06:06 PM
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1. Know the speed you want to run at (depends on prop size, see the chart at:
http://matthewsmodelmarine.wordpress...all-geared-up/
Maybe you want 3500rpm for a 4" prop?

2. Chuck the shaft in a drill press at a known speed, and run it as a generator.

3. Measure the output voltage on the leads.

4. Motor's kV is: Drill press speed volts. (3600rpm & 6V out? KV = 3600 6 = 600 rpm/V )
> This means the motor's free speed will be 600rpm on 1v, 1200rpm on 2v, etc...

5. ...and 3600rpm on 6V! Just what you want, so run the motor on a 6v battery (it will actually slow down a bit with the prop load in water, but that'll be ok).


Of course, your motor will vary... test it and see.


Oh, and this doesn't mean it's a "6 volt motor". It just means that it will do what you want on 6v. It might actually have been designed to run at some max speed like 9600rpm on 24v...
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Old Nov 19, 2014, 06:43 PM
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United States, CA, Bellflower
Joined Jul 2012
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Take a peek:
http://www.jameco.com/webapp/wcs/sto...001_2167437_-1
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Old Nov 19, 2014, 06:57 PM
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Take another peek:
http://www.johnsonmotor.com/en/resou...dc-motors.html

"HC970" is merely a frame size, a normal round motor with 3 poles about 2" in diameter. An HC970 could be further customized with ANY number of windings... there is absolutely no guarantee that the HC970 sold by Jameco is the same as mrbassman's motor.

Test and see...
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Old Nov 19, 2014, 07:00 PM
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But... that Jameco "special buy" (probably a surplus lot), sure looks like a good deal for about a 4" prop on 12V...
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Old Nov 20, 2014, 02:49 AM
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Wirral, UK
Joined Jan 2007
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sorry to hijack this thread, but whilst the topic of Johnson motors is here, we run a cheap class of shop bought kit race boats, called club 500. The supplier gives everything you need, the motor is Johnson 550hc. Some members are saying a replacement motor, a Johnson 600 is the same. I have spent hours trying to find this info out. The idea of this class of racing is that no mods are allowed, but seeing as these motors are dirt cheap on ebay, is the 600 the same as it was a replacement? nobody is selling a 550 so it might be true?

Any help appreciated,

Thanks
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Old Nov 20, 2014, 08:41 AM
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I thought I might as well add more confusion to the motor size debate on mystery motors. First off the number, which everyone calls CAN motors by, i.e. (380, 400, 540, 550, 600, 700, 920, 940), well you get the idea, is simplely the size of the can of the motor. It has nothing to do with the power or speed that the motor will produce other than allow for the size of the magnets and the number of turns of wire that can be put into the provided space.

If you have a given size motor say a 600 size can, other factors come into play which will allow for the speed and torque that the motor will produce. Designers of motors must have a given set of requirements to produce a motor which will fit the bill. The size and type of permanent magnets, the gage and number of windings on each segment, the number of segments, the type and composition of the brushes, whether or not to use a torque ring, type of bearings, all come into play on what the final product will produce in power.

When in doubt or unable to find the specs of a given motor, when all else fails, there is the trial and error testing on your own to produce a set of specs for the motor.
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Old Nov 20, 2014, 07:08 PM
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Tollytime's Avatar
United States, MI, Macomb
Joined Nov 2006
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Here's a 550

This is what you do with a brushed motor after you properly identify it.

Setting up a brushed motor for a scale boat (0 min 16 sec)
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Old Nov 20, 2014, 07:37 PM
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Motor City
Joined Dec 2004
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Looks like you need a bigger hammer! Hardly made a dent in that thing...
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Last edited by patmat2350; Nov 20, 2014 at 10:01 PM.
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Old Today, 03:30 AM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Overloaded electric motors compilation (6 min 40 sec)

Electric motor blow compilation 2 (3 min 58 sec)

Your doing it wrong
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Old Today, 04:37 AM
Submarine or Target?
ericbphoto's Avatar
United States, SC, Piedmont
Joined Jul 2013
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mrbassman,

You may notice that some people are decidedly biased against brushed motors. Feel free to ignore them except when they are providing entertainment.
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