Author
You can see the pictures here http://www.bigbigplanet.com/about/sim/rccars/mantis
(towards the bottom of the page).
WHAT I USED:
1) A Yokomo T-max rebuildable stock motor
2) 15 meters enamel-coated wire from electrical wholesale/retail shop (opposite Pudu Plaza main entrance). Not sure what gauge the wire is but it is quite thin, so I managed to get 40-winds before I ran out of space on the armature.
3) A soldering iron, some solder, solder paste, third-hand tool (can get all at that same shop)
4) Epoxy glue
5) Dremel tool, cutting disk, SAFETY GOGGLES (or a small file might work too, but much slower)
6) A sharp knife or small file to scrape the insulation off the copper wire in some spots
7) Motor bearings to replace stock bushings (optional)
HOW TO UNWIND AND RE-WIND:
Get the new copper wire ready and remove all kinks and tangles before you remove the original copper wire. When you remove the original wire, make a mental note of how the wires are wound. When the armature is free of the old wire, wind the new wire on the same way. Keep the winds close and neat and tight. Make 40 turns and then mark where the wire needs to be soldered on to the commutator. Scrape the insulation off this part and solder it onto the comm solidly, without using too much solder. Now move on to the 2nd stator and do the same. When the third stator is done, cut the wires so that the ends are just the right length to be soldered onto the comm. This part can be a little bit tricky. The last few winds will try to unwind themselves a bit, but don't be satisfied until you can get the last few winds quite tight before soldering them down. When you are satisfied with the tightness of the last few winds, cut the ends of the wires so that they are the perfect length, remove some of the insulation at these ends and solder them onto the appropriate part of the comm.
EPOXY:
Mix some epoxy and brush them on the copper wires and let it dry. This should prevent the wires from expanding and unwinding when they heat up.
BALANCING THE MOTOR:
If you are into RC planes, you probably have a propeller balancer that you can use to balance the armature. I didn't have such a thing, so I just stacked up 4 cd-cases into 2 piles and hung the armature between them by the shaft. The armature would roll with the stators hanging down between the 2 stacks. When the armature stops rolling, the lowest part of the armature is the heaviest part. I'd mark this down and grind away a little of the stator here with a cutting disk. (WEAR GOGGLES, KEEP THE ON/OFF SWITCH WITHIN REACH, NEVER DROP THE ROTARY TOOL WITH THE CUTTING DISK SPINNING AND ALWAYS WASH YOUR HANDS THOROUGHLY AFTERWARDS).
The idea is to remove parts of the stators that are heavy and add epoxy to the parts that are light, but I found that removing material was a lot easier than adding material. I had to remove very little material at a time because whenever I removed too much material, I had a tough time getting the armature back into balance. Because of the limited smoothness of the cd-cases and the limited levelness of the ground, the balancing results were inconsistent, but I was satisfied when I rolled the shaft along different places on the cd-cases and found that the results were 'evenly inconsistent', if that makes any sense.
I'm pretty confident it is now sufficiently balanced for the low RPMs that the motor will be spinning at.
TESTING:
I have not had time to give the motor a real world test, but I will do so when I get back from my honeymoon in July. It takes quite a bit of juice to get the motor turning. At first, I tried 4X AA-sized rechargeables and the motor didn't turn, but when I put in 6 sub-C cells, the motor spun at a decent rate. It is definitely slower than a 27-turn silver can but I am not sure if it will have enough torque for some of the projects I want to use it for.
More reports later when I test the motor out in the buggy as well as in a rock crawler.
CREDIT:
Everything I know about winding motors came from this thread http://www.rccrawler.com/forum/showthread.php?t=3160 on http://www.rccrawler.com
The method of balancing the motor came from cotharyus of rccrawler.com while the idea for using a prop balancer was given to me by johnrobholmes also from rccrawler.com.
DISCLAIMERS:
I would discourage using your own hand-wound armatures in official races because you will likely either not be allowed to use it in the race OR the race organisers may ask to unwind your motors after the race to check that it follows the rules and regulations of the race, hence ruining your cleverly-wound armature.
Rotary tools are dangerous, especially when used with a cutting disk. ALWAYS USE SAFETY GOGGLES, always keep a firm grip on the tool, always keep the on/off switch within easy reach and use clamping vices to hold parts that you need to work on whenever possible. Always wash your hands, arms, face, etc to get rid of the metal/plastic dust etc after working.
Balancing a motor is very difficult to do. In this post, I've successfully made 40-turn motor with a relatively low top rpm, so balance is not a major issue for me. If you are to use my methods to wind a 'hot wind' low-turn speed motor, it might not work very well at all because the armature might be too unbalanced at high rpms, and it could cause damage to your motor, battery, esc, radio system, and/or RC model.
Use only insulated copper wire to wind motors. Many shops sell copper wires for hanging picture frames and these are not insulated. If you use uninsulated wires to wind a motor, you will unwittingly be building a 1-turn motor and put yourself in danger of burning down your motor, esc, batteries, RC model and/or house.
Happy modding.
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