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Author Topic: Motor identification needed  (Read 1152 times)

mudway

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Motor identification needed
« on: September 06, 2020, 04:04:32 am »

A friend has given me a couple of these motors he picked up in the UK some years ago at a Model Boat Show. There are no markings on them and they weigh 630g each, diameter of 52mm and length if 85mm.  Multi pole. Quite a good torque on 12 volts where they pulled 1.3 amps no load.


I'm guessing they are some sort of 900 series motor but no idea of the manufacturer or the designed voltage   (12 or 24v?)


Has anyone come across these beasts. They look too good to chuck away.
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malcolmfrary

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Re: Motor identification needed
« Reply #1 on: September 06, 2020, 08:18:22 am »

About the only semi-scientific check that can be done is to short the terminals, put the shaft in a vice and turn it one half of a complete revolution, counting the number of resistances you feel to get the real number of poles.  That, and hooking up to a prop in water to see how it moves water, and what current it pulls under load.
Obviously no telling what is on the inside, but should be a fine tugboat motor.
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mudway

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Re: Motor identification needed
« Reply #2 on: September 06, 2020, 08:26:34 am »

Thanks, the in water test will be tomorrow but it has 6 poles.
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Tug Fanatic

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Re: Motor identification needed
« Reply #3 on: September 06, 2020, 08:29:40 am »

I suspect that they will be at least 12v. In a way the spec doesn't matter much as long as they do what you want them to do.

What is the stall current and free running rpm on 12v?

There are literally hundreds of specs for motors which look identical as many 540 owners have found out.
 
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mudway

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Re: Motor identification needed
« Reply #4 on: September 07, 2020, 04:13:12 am »

Don't think this is a tug motor. I was thinking of using it or both of them in a 46" Huntsman. Did some tests this morning and as well as wondering what the specs are, I wondering where I can get some more.


My normal fast boat motor set up is a single John Darke 785 motor on 4S and a 32 mm Graupner s/steel 2 blade prop. I tested the Darke on the same props as the 900 and interesting results. The 900 with the 45mm graupner aluminium prop moved a lot of water. Not as much as the Darke but at less amps.
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DaveM

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Re: Motor identification needed
« Reply #5 on: September 07, 2020, 12:34:18 pm »

These are Johnson 900 motors and I've handled two totally different versions. One does about 12000RPM on 12v and will happily handle 24v; this is more or less equivalent to the old Graupner Speed 900. A big Perkasa with that power train and a 55X prop will be ballistic. From the data you supplied it looks like this is the version you have. I used to buy mine from a golf-trolley manufacturer in Chesterfield, UK, but he stopped using that motor and I've no idea whether there are still any left in the marketplace. As far as I know I bought his last two trays of "perfects" and he was selling off some more water-damaged ones for a few months afterwards..
The other type was/is marketed by CEM Models and called a CEM 900 High Torque. It is rated at 12v when it will turn at 3000RPM - just the ticket for a large tug.
Dave M
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malcolmfrary

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Re: Motor identification needed
« Reply #6 on: September 07, 2020, 02:02:20 pm »

Thinking about poles - 6 is unusual for a permanent magnet motor - usually its an odd number to ensure self starting.  3, 5, 9, 11, that sort of thing.  When turning manually, one clonk for each time an armature pole passes a magnet pole, so count the full circle, divide by two.  Rule of thumbing again, but generally, the lower the pole count, the faster the motor will turn.
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mudway

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Re: Motor identification needed
« Reply #7 on: September 09, 2020, 09:51:11 am »

These are Johnson 900 motors and I've handled two totally different versions. One does about 12000RPM on 12v and will happily handle 24v; this is more or less equivalent to the old Graupner Speed 900. A big Perkasa with that power train and a 55X prop will be ballistic. From the data you supplied it looks like this is the version you have. I used to buy mine from a golf-trolley manufacturer in Chesterfield, UK, but he stopped using that motor and I've no idea whether there are still any left in the marketplace. As far as I know I bought his last two trays of "perfects" and he was selling off some more water-damaged ones for a few months afterwards..
The other type was/is marketed by CEM Models and called a CEM 900 High Torque. It is rated at 12v when it will turn at 3000RPM - just the ticket for a large tug.
Dave M
Thanks Dave. I think these might be the water damaged ones by the state of the casing. Doesn’t seem to have affected the working as they are very smooth. I might just try one with a 45mm Graupner Aluminium prop I have sitting here.

Meanwhile, he turned up again with some more big motors. These both have Buhler stamped into the case as well as a sticker saying “12 Force” as well as saying they are 12 pole. One is 750g and 88 x 62mm. The other is smaller at 430g and 65 x 48mm. Will have to get some shots of them and do some tests. God knows what else he has in his garage. Hopefully some motor mounts for them.

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