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Re-winding a hubmotor

Farfle

100 kW
Joined
Jun 27, 2010
Messages
1,759
Location
Redmond OR
I just bit the bullet and ordered the stator stack for my next motor, and ill do the build-thread here. But first I have a few questions.

The gauge of wire in the motor is unknown, how do I tell what gauge it is, burn the insulation off or mic it or with the insulation?

The lam stack can be coated in a green epoxy of some sort to protect the windings from the sharp corners, what is that epoxy?

The glue holding the magnets on is unknown, would it be worth taking them off and re-gluing them with hysol or similar?

ill get pictures of the lam stack and magnet ring when I get it in the shop.
 
The green epoxy is Scotchcast 263, I talked about it here: http://endless-sphere.com/forums/viewtopic.php?f=31&t=20321&p=482141&hilit=scotchcast#p482141

The above post has a data sheet attached. The stuff is not that expensive (I talked with 3M), BUT it comes in 60 lb sacks and you have to buy 9 sacks! I found one reseller that would sell a single sack, but the price jumped to around $25 US/lb, so over a kilo buck for a sack.

If you use slot paper, use calendared Nomex 410 paper. If you need some of this let me know.

Measure the wire with insulation. Then burn it off and brillo pad the goop, and measure again.
 
Thanks BM, don't have the donors in yet, but Ill be posting pictures ASAP. are there any alternatives to the scotchcast? i seriously considered JB weld, its heat resistant, flows well when warm, its cheap, plus, its slightly ferrous. What do you think?
 
Farfle,
IMHO you can side step the coating process completly if your using some nomex paper for insulation.
I am suprised by how easy it is to "pull a short" in the stock green epoxy on the turnigy motors....the nomex is indestructable & even more heat resistant than epoxy. just a light varnish on the stator to fight corosion is all you really need.

I even tried fiber glassing the ends of some rough stators trying to make them short proof...the paper is the bomb for its purpouse.
 
I do have a formulation that I am working on to replace the unobtanium Scotchcast. I have the oven operational, and will have a test batch of the powder formulation in a few weeks. I need to make a miniature fluidized bed however to evenly coat the stator and see if we got it right or not.

I fully support Thuds statement on the use of calendared Nomex 410 paper. It is great stuff. I wanted to use the use calendared Nomex 410 paper over a good epoxy however for the extra protection. Regular brush on I do not believe will give the even coating. The Scotchast is done by heating the stator to a high temperature and then immersing it in a fluidized bed of the epoxy powder. It melts, it flows, it sets in less than a minute.
 
Thanks so much for the help so far, will be getting some nomex paper then. but before that, more questions! so, what wire to use? something that's durable enough for a relative noob to pull (have re-wound countless CD-rom motors before brushless out runners were popular in RC) but still having a good temperature resistance. And one more thing. Its all hypothetical, but assuming the motor is wound with 4 turns of 4 strands of 23guage, I want to double the KV of the motor, and I am taking the lam stack and making it twice as wide, does that mean that it has to be wound with 1 turn of 16 paralleled strands to achieve that? and how the farck would I do that? because one turn of an equivalent gauge single wire, or pair of wires probably wont fit in the slot, and 16 paralleled wires would be a serious handful. Thanks again with the help so far.
 
I can vouch for the Nomex paper too. Really tough stuff. Another thing that helps is to sand off the razor sharp corners on the laminations. I don't think they debur them after punching them out. Just enough so it doesn't feel sharp. There will be far less chance of punching through if the edges are rounded.

Multi-filar windings can have some advantages but also have some challenges. For a rewind, I'd generally stay close to what the original configuration was.

I used some nasty varnish stuff on one of mine to prevent the windings from vibrating. I susupect there is a better product for that. It did work though.
 
Woo! New motors are here :D , ill get pictures of their internals as soon as I can get them apart.
 
This is exciting! Use leather gloves to wind with. And eat your spinach :wink:
 
ooh yeah, winding CDrom motors with 28ga wire is probably a joke compared to this.
 
baaaa. how hard can it be? :twisted: :twisted:

I wind tunigys bare-handed these days as i have caloused up signifigantly pulling 14 & 12g wire for more than a few guys on the board.
but I still HATE winding anything with more than 2 strands.

we looking at 30+ teeth here Farfle? (i'll be happy to watch this one from the side lines LOL)
hubzilla is born......or is that frankenhub?
 
This will send Hubzilla home. Not sure what its going to be named, but its 63 teeth. Im thinking a name something along the lines of PITA :lol:
 
woo! have pictures, the stators weren't as wide as Id hoped, so I may end up doing three of them, but will see what it looks like with two.

100_0012.jpg


100_0013.jpg


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looks like it will be 38mm wide, and 260mm in diameter, with 63 teeth and 56 magnets.
 
just cut one of the coils, and it looks like its 6 turns of 8 wires, as there is 48 wires passing thru one slot. Is this correct?
 
Got the windings cut off and machined the stator cores to mate flush with eachother. But when i was machining the magnet ring to be flush to the magnets I effed up, hopefully not too badly. I lathed the very edge of the magnet ring a little tiny bit which fractured the edges of the magnets. None of them are cracked, and a non-cracked magnet ring will be right next to it, if all else fails i can buy new magnets, as they are just flat magnets and not any special curve.

2011-12-27204605.jpg

2011-12-27204757-1.jpg

2011-12-27205353.jpg
 
The magnet chipping is not a real show stopper. I wouldn't worry about it other than you should paint or epoxy over the exposed magnet material. The tiny decrease in magnetic strength will slightly change the voltage constant but probably not enough to measure.
 
Farfle said:
Got the windings cut off and machined the stator cores to mate flush with eachother. But when i was machining the magnet ring to be flush to the magnets I effed up, hopefully not too badly. I lathed the very edge of the magnet ring a little tiny bit which fractured the edges of the magnets. None of them are cracked, and a non-cracked magnet ring will be right next to it, if all else fails i can buy new magnets, as they are just flat magnets and not any special curve.

2011-12-27205353.jpg
I bet the magnets chiped when the stator was installed into the magnet ring last. To many people are not carefull enough with that.
 
If you want to see what effect the chips in the magnet have, put a sheet of white paper over the magnets and sprinkle some iron filings on. Tap the paper slightly and you will see the lines of flux. I don't think you will see a huge difference between the chipped ones and the perfect ones.
 
Arlo, they chipped when I tried mashing into them with the toolholder at 860 rpm while i was machining the sideplate. If any of you get to machine magnets, i would highly reccoment high speed steel, as it produces a spectacular magnesium-like fireworks show.
 
Farfle said:
Arlo, they chipped when I tried mashing into them with the toolholder at 860 rpm while i was machining the sideplate. If any of you get to machine magnets, i would highly reccoment high speed steel, as it produces a spectacular magnesium-like fireworks show.
lol sweet.
 
Farfle said:
just cut one of the coils, and it looks like its 6 turns of 8 wires, as there is 48 wires passing thru one slot. Is this correct?

No, actually they are 96 wires thru one slot if you count the other coil. :D
Is it some kind of known motors you use, or is it something new?
 
parabellum said:
Farfle said:
just cut one of the coils, and it looks like its 6 turns of 8 wires, as there is 48 wires passing thru one slot. Is this correct?

No, actually they are 96 wires thru one slot if you count the other coil. :D
Is it some kind of known motors you use, or is it something new?

Correct sorry, yes 96 per slot. And it is a known motor, its a magic pie hubmotor :D
 
Ok, the existing wire mics out to be .55-.51mm with burned-off varnish and .61mm with varnish. What guage wire is it?

2011-12-28142342.jpg


2011-12-28142722.jpg
 
More progress made, I think Doctorbass would be proud :D . I got the two magnet rings glued together with DP420, Thats a B*$&# by the way. They do NOT want to be side by side, ended up machining a massive plywood plug that gets pressed into both rings, screwed it and the bottom ring to the table and stacked the two, and held them together with vise-grips. Hopefully it comes out tomorrow when the glue dries :shock: . Oh and heres some side-by-side comparisons with an old crystalyte outer case:

100_0022.jpg


100_0021.jpg


100_0018.jpg


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