View Full Version : directions for rewinding a turnigy brushless
06-20-2010, 07:32 PM
hey gang,can anyone lead me in the right direction to instructions on how to rewind a brushless motor. not sure I'll try but would like to read up on it and also look into upgrading it. i recently[yesterday] burned my 35-48-1100kv SK series motor while in flight....landed with out a problem and thought the smoke i saw was the esc......but after pulling the motor and esc i discovered the esc was fine and the bell on the motor was spinning stiff. i also had the motor completely apart and noticed a few strands of very thin wire loosely wound around the magnets with broken ends.
seems like the bearing should be replaced and i read about bocca bearings being a good source of replacement bearings.
i cleaned the motor with wd-40 and blew it out with a air compressor,reassembled it but still spun by hand stiff,and hooked it up with no success to get it running....simply chugged alittle and got hot very quickly.
hoping to be show the best thread on rewinding and how to rebuild motors. also how to size the bearings for ordering new ones....thanks for any suggestions my friends, stu:ws:
06-20-2010, 09:33 PM
I'll not discourage you from trying to rewind your motor. It is an interesting intellectual and manual exercise. I've done it once. It probably isn't a cost effective use of your time strictly from a cost of equipment standpoint, however. I've bought bearings from Boca before and had good service from them. To figure out bearing sizes simply measure the old ones. The HK web site says the shaft is 5 mm diameter so that will be the inside diameter of the bearings. Disassembling the motor can be a challenge. Especially getting the old bearings out. You're fortunate in that you don't need to worry about damaging the windings since they're toast:rolleyes: anyway. What I've done in the past is use a piece of steel small enough to fit through the bearing and long enough that, when laid cross-wise, extends nearly the full inside diameter of the bearing tube. You can then put a longer piece of steel through the length of the motor, with one end against the small piece of steel laying cross-wise inside the motor and resting against one of the bearings. By supporting the motor stator with a block of wood with a hole large enough to let the bearing fall out, you can press out the first bearing. I don't recommend using a hammer. Once you have one bearing out you can flip the stator over and either use the same two pieces of steel, or a piece of steel a little smaller than the inside diameter of the bearing tube to push out the second bearing. New bearings can usually easily be pressed in using a block of wood to support the stator and a small block to protect the bearing being pressed into place.
As to rewinding the stator, there are a number of winding patterns used in these outrunner brushless motors. According to the HK web site your motor has 3 turns. Chances are it is a DLRK wind scheme with 3 turns of wire around each stator pole but you need to confirm this as you remove the old windings.. It is most likely wound with many parallel strands of wire. This doesn't give the highest possible efficiency but is MUCH EASIER to wind than a single fat wire strand. There are probably 12 stator poles in your motor. I have no idea whether those windings are connected in a "Y" configuration or a "delta" configuration. You'll need to determine that by inspecting the old windings.
You're already in the correct forum here on WattFlyer regarding brushless motor construction. I suggestion you do some reading as I don't recall posting about rewinding the particular motor you have.
06-20-2010, 11:18 PM
I rewound my motor by plugging the blue motor wire into the red wire on the esc, and the red wire from the motor into the blue into the esc, and the black into the black.
06-21-2010, 01:14 AM
if rewinding is such a chore and not cost effective,is there a way to QC the manufactures work on the windings? an adhesive or something to improve a possibly loose winding . i was surprised at how easy the motor came apart...the bearings dropped out of the motor,no pressure required....i want to order 2 new motors but the reviews on the turnigy reviews are showing a bunch of unhappy customers ....sounds like hobby king has another bad batch of turnigy motors:(.
06-21-2010, 02:31 AM
WOW, I've never had one come apart that easily! At least it'll be easy to measure the bearings! HK does appear to have occasional bad runs on motor assemblies. I guess I've been pretty fortunate as I've not experienced that.
Rewinding is tedious and error-prone but has been done many times successfully. I've done one and was quite happy with the result. My re-wound motor is stronger (though it had essentially the same Kv) and more efficient (which means it runs cooler!). YMMV. In my case the Worst part was getting the old wire off the stator. The windings had been filled with epoxy and getting the old wire off without damaging the green insulating layer that was on the stator was a serious challenge. I wound mine with the fattest possible single-strand wire that would allow me to get the number of turns required (in my case 9) on each tooth. I used old nylon propeller blades and small hardwood sticks to mash the wire into place so I could get it all to fit.
As to "enhancing" a HK motor... Adding a little epoxy to keep loose wire strands from getting into trouble would probably work. Loose, vibrating wires will eventually wear through the insulation and create a short, either between wires or between a wire and the stator frame. Or, as you experience, they can get caught on a rotor magnet and be ripped. The down side is that epoxy is a pretty lousy heat conductor so the wire buried in epoxy tends to get hthat waotter than the wire exposed to free-flowing air. If you don't push a motor with epoxied windings too hard though I'd think it would give good long service.
As far as electrical QC on a manufactured motor you'd want to measure isolation between the windings and the stator. It should be at least 10's of megohms. Measuring actual winding resistance is a bit tough though there is a thread around here somewhere in which inexpensive techniques for doing that are discussed at length. You'd be looking for imbalance. Any significant variation in the winding resistance among the three terminations would indicate a problem. The exact nature of the problem would be hard to tell though. The problem could be a short between wires, or, because of the multiple strand windings, one of the strands not being connected, or there might be the wrong number of turns on one or more of the poles. Imbalance in a delta wound motor leads to "circulating" currents within the windings that produce unnecessary heat generation.
06-21-2010, 04:07 AM
thanks for that info mustangman,i just ordered2 new motors from hobbyking and will pull the motor apart when they get here. i hope to just inspect the magnets,wires,the windings and look for any fileings not cleaned out at the factory. if i see the windings arn't tight i might add adhesive .....would mediume ca work better then epoxy as its thinner and would help the cooling issue better then a layer of epoxy? i hope to get the roar back in the air soon but just the shipping alone will be 2 or 3 weeks:mad:.
i did look at heads up rc 35-48-900kv as an option but never tried the power up motors. also considered the hobbyparts monster motors but again haven't heard much of others using them. for $30 the price is right.
also considered eflite,scorpion,and axi[ in my dreams].....woops,my wallet isn't even considering those:Q.
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