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Old Nov 18, 2012, 12:51 AM
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R Zielinski's Avatar
USA, NH, Madbury
Joined Dec 2007
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Help!
How hard is this to fix?

I nosed this motor in, pushing it back against mounting screws. A screw head crushed the wires. I've never worked on motors, so I don't know how to get the stator off the thrust tube. It looks like there's enough wire in there to graft on new wires, but I wonder how hard it is to solder that coated wire. I also can't get the 2 stacked front bearings out. Looking for advice on fixing vs. replacing with a $50 no name motor. It is a nice Reaper GR 60, so hate to use it as a paperweight. If anyone is interested in fixing these wires and getting the bearings out for a fee, let me know.
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Old Nov 18, 2012, 01:14 AM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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Ouch.

That's a pretty tough repair unless you want to completely rewind it. The motor leads in this case are just the ends of the windings extended out, so to solder them you'd have to strip the enamel off all the individual strands. I use fire and sandpaper... That in itself is a tricky proposal with so little wire to work with.

Getting the stator off the bearing tube without damaging the windings any further would be a challenge. Normally, I like to bolt the backplate to some sort of mount, wrap the stator in a few layers of protective cloth or leather, and then twist and pull it off with a large pair of pliers. Heat is usually required to soften adhesives, but I've had a few that didn't need any. That heat will hammer the winding insulation, though, so ya gotta be careful. Maybe pop the bearings out if possible and stick a soldering iron up the bearing tube for a few seconds...
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Old Nov 18, 2012, 07:28 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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It it the motor in the image? The GR-60XL?

Here is a thread on getting motors apart, that and some photos to see if it looks like it is worth re-winding would be a good start:

http://www.rcgroups.com/forums/showthread.php?t=1079423

Jack
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Old Nov 18, 2012, 09:53 AM
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R Zielinski's Avatar
USA, NH, Madbury
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Argh. I was afraid of that. I'm not really up to attempting a rewind on this. It looks like it has 12 miles of wire in it, packed VERY tightly. I bought this used and was told it was the original GR 60 with Kv about 850. However, there were apparently some XL's sold that had no identification and used the same label. It certainly looks like the thinnest wire possible, so I can't imagine what the XL windings look like. Wouldn't it have to be even thinner to get the Kv down? Maybe this IS the XL version. I never put a tach on it. Looks like a moot point anyway, as it will make the same aquarium feature either way.
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Old Nov 18, 2012, 10:04 AM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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My guess is that it's wound with many parallel strands of very thin wire, which is a common practice that allows manufacturers to keep just one wire gauge on hand while using it for many different motor sizes and winding schemes. To lower the Kv of a motor, they just run less strands in parallel to get more turns in there. There are probably only a few actual turns on that stator.

If you rewound it with one strand of much thicker wire (or maybe two or three in parallel), you could almost certainly increase copper fill, efficiency, and performance without a really huge amount of effort.
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Old Nov 18, 2012, 10:15 AM
Jack
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What C₄H₁₀ said!

The total surface area in all of the parallel strands decides the current capacity. So ten parallel small strands can be as good as one large strand. The number of turns and termination method use, and only those, decides what the Kv will be for the set of components in the motor. The surface in the wire decides the current capacity.

It is impractical to use a single large strand and wind a motor that large. Also it is easier for cheap Chinese motor makers to have to only stock one size of wire (0.25mm dia. typically) and just vary the strand count to wind different motors. Other wise they would have to stock a wide range of wire sizes.

Look at the image, that is an 18 turn motor with a factory wind and the same motor rewound to about the same turn count with a single strand. It is also a different wind but that is incidental to my needs as far as best matching the motor to a prop and battery voltage.

Your bigger motor may be a re-wind candidate, I think using two or three larger strands would be the approach I would take.

Jack
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Old Nov 18, 2012, 04:49 PM
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If the wires aren't shorting each other or to the case, I'd just cover the whole area with shoo-goo.
Maybe a coat of polyurethane varnish over the exposed wire and then a coat of shoo-goo.
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Old Nov 18, 2012, 04:51 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
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Hoppy, some of the strands themselves are severed. The motor might still run without them connected, but efficiency will take a big hit.
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Old Nov 18, 2012, 05:26 PM
Space Coast USA
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If those aren't motor winding wires that are cut, I don't think it would be a problem. If they are motor windings, I agree with you.
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Old Nov 18, 2012, 05:40 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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The damaged wires are the windings, you can see that in the photos.

They brought the bundles of the parallel strand winding wires out and cased them in heat shrink tubing.

That is very typical work.

The motor needs to come apart, and have the bearings and windings checked. When you fire up a motor that is damaged like that you are playing "you bet your ESC" if you have not checked things out. And burned up ESCs are a lot harder to fix than motors...

Jack
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