|Feb 18, 2009, 12:16 AM|
Rewind of a Turnigy SK 3530-1400
Hi guys. i`m new to this so be gentle. LOL
I bought this motor and it does what I need, but after boinking the prop shaft pretty hard on a tail-heavy "landing" it appeared to have broken one or more magnet-wire. It would only stutter.
After reading several helpful threads, I`m going to try to rewind it close to the factory specs, but with better single strand wire, or maybe two strands of smaller wire if that seems better. I`d like to do a single if it will fit.
It`s a 12 tooth stator with 14 magnets and I`ve found some good diagrams for this type of motor.
I was able to count 9 turns of the wire they used. Their wire seems to be the weak point of this motor. It is made of 10 strands of very thin wire.
I was able to get it apart without doing too much damage. I see now that I should have used more heat. I can do better next time I guess.
The magnets seem to be glued in fairly well.
My plan is to stop by RS and get some practice wire tomorrow. Also order some good wire once I see what size/sizes to try.
Here are some pics of what Ive got. Any suggestions will be appreciated.
|Feb 18, 2009, 03:52 PM|
Wow.. great thread! I have a SK 3536-910kv on it's way to me and I hope to be able to rewind it after it arrives. I've never removed a stator from it's bearing tube in a motor like this one so you're definitely one step ahead of me.
The specs say the motor I'm receiving is an 8T motor so I'm planning to go with 7T of 20 or 21 awg wire because I'd like to raise the KV a little bit. This is all just a guess on my part though until I have the motor in hands and have the time to take it apart.
I can't tell you what gauge to use but my only advice is to try to use single stranded wire if possible. Also keep in mind that Radio Shack wire is good for practice, but I've never been able to wind a motor with that stuff and not have a short. I've also read that that it has a much higher resistance than quality wire does so that's another reason not to use it.
I know that's not much to go on, but I hope it helps.
Good luck with your motor!
|Feb 18, 2009, 05:57 PM|
Thanks Shawn, any advice at this point for me is good advice. LOL Thanks for the input. When you get yours please add your stuff here too, if you want.
Well, I`m officially a motor re winder, I guess .
I sopped by a RS at lunch and picked up some magnet wire, just for practice. I have newbie wire coming from gobrushless.com. It (the RS wire) comes as a 3 pack with 30, 26 and 22 gauge wire, green, red and gold, respectively.
I pulled up the diagram below from my saved pics and thought I`d just see if I could translate the diagram to the stator. I used the 30 gauge wire, just because it was the smallest and there`s more of it. The first leg went well although I miscounted the stator when I was crossing from #2 to #7 and had to unwind #7 & #8 and re do them.
So I had one leg done, let`s do two. OK, it was starting to make sense. So I did the final leg. Now, I was just throwing the wire on the stator and holding the stator in my hand. I was just trying to get the wire in the right place and count 9 turns. I think I ended up with what you would call 9.5 turns on each stator post.
Well I couldn`t resist. It looked like it might work, so I soldered on some bullets and hooked it up to an old esc (knowing that I might fry it). I need to read how to check for shorts, but time was short. i had to get back to work.
So, I hooked it up, added my servo tester to control the esc and plugged in a 3s lipo. What do you know, it armed properly and sat there waiting for me to turn the dial on the tester.
I gave it the juice, and it started up and ran as pretty as you please!!!! Very cool, because last night this motor was just another paper weight.
I need to test it tonight and see what kind of KV I`ve got.
Of course, this is just for test with the 30 gauge wire. Is it correct that the kv reading will be the same, even with the small wire on it? I`d like to get about 1500kv for my application.
I hope my wire gets here by Saturday, so that I can wind a real motor and see how it goes.
|Feb 18, 2009, 06:06 PM|
Shawn, as far as getting the stator off of the bearing tube, it was not that hard. I used a monokote heat gun to heat mine up and it was enough. I`ve seen that some guys use a soldering gun and just cram it in the bearing.
When I pried the stator off it didn`t take much force. The bottom of the stator is protected by all of the wire, but I did scar up my back plate some. In the future I`ll see if I can slip a thin sheet of metal in and pry against that instead of the back plate.
Also some of the wire came off easily, but some seemed to be locked on with CA glue. A lot of heat should take care of this too. I didn`t use enough heat and did damage some of the enamel on the stator. I plan to touch that up with some epoxy before the real wind.
I`m anxious to see what the kv looks like. More later. Lee
|Feb 18, 2009, 06:52 PM|
Well, 9.5 turns is too many. The spokes on the front of the bell seemed to work well to get a good tach reading. I just set my tach for a 4 bladed prop and shined a flashlight on the front of the bell.
I tested with 3s, 4s and 5s and got pretty consistant readings.
12,700 rpm / 11.9v = 1070kv
17,100 rpm / 15.7v = 1090kv
21100 rpm / 19.75v = 1068kv
Looks like I need to try the stock 8 turns, but these results are real cool.
My main goal here is to take this inexpensive motor, up-grade it and fine tune it to the kv that I need. It seemd to be plenty happy running at about 340 watts for 5.5 min at full power with the stock wire. I`m hoping to get 400 watts out of it with good wire.
It does have the thin laminated stator and the two "big" bearings that I`m looking for.
|Feb 18, 2009, 07:08 PM|
Here`s a combat plane built by my friend, Lester, for 3696 RCCA combat. It`s a great match for this motor on 3s at about 180 watts. We spin a 9/6 APC-e prop at a spec 9k rpm. We fine tune the max rpm with the atv on the radio so that everyone runs at 9k.
This is a Romanian fighter from WWII that was a Russian fuselage mated to a French engine and a Romanian wing. The IAR-80. A very little modeled WWII fighter. I can`t wait to cut the streamer off of it. LOL
|Feb 18, 2009, 09:03 PM|
That last test with 9x6 afraid.
Do not try the motor with propeller, if not well secured. (never with your hands)
Possibly because you realize, it seems that three a little damage in his right hand.
Congratulations on your successful wind.
Now if using the no. 22.
|Feb 18, 2009, 09:52 PM|
Thanks Manuel. Of course, you are right about safety. I`m showing a bad example. I have some good quality #22 wire ordered. So I`ll use that when it gets here.
I used your diagram to wind the motor. It is the best that I`ve seen. Very easy to follow with success. Thank you for your rewind threads. They were full of good information that helped me do this on my first try. Lee
|Feb 19, 2009, 07:57 AM|
Congratulations on the motor rewind! You've done very well for a first time winder! I also appreciate the advice for removing the stator from the bearing tube. Because I don't have a heat gun I'll probably try with the soldering iron first and then go from there.
I do have to agree with Manuel though; watch those fingers! You need them for winding your motor when the 22 awg shows up!
|Oct 30, 2011, 06:07 AM|
I was given a fried SK 3530-1400 to rewind recently. From what I have read, these tend to burn up quite easily. Not sure if this is due to people trying to run them at their advertised power handling of 470W or original winding method. Either way, always liking to crack open a new motor I took the challenge.
Dismantling the motor I found it to be quite well built. Big bearings, sturdy bearing tube and back-plate with plenty of room both in front and behind the stator makes it a dream (to me at least) to work on. The stator is measured 28mmx10mm with a rather large 13mm bearing tube hole. Once the stator was removed, I noticed that the stator did not fit tight to the bearing tube. I mean if you pointed the motor up, the bearing tube/back-plate would slip out the bottom without issue. This made me concerned about reassembly.
It was wound with 11 strands of 30ga (measured) wire with 9 turns per tooth dLRK and terminated Delta. The wind was decent enough and filled the stator slots almost completely. I was not given any request to rewind to a specific kV or performance spec, so I went back with the original wind but with single strand wire.
The original wire has a total cross sectional area equal to solid wire between 19ga and 20ga, but closer to 20ga. The 20ga was impossible to fit. 22ga was a breeze, but left too much open space for my liking. 2P-23ga was perfect, but I did not have enough to complete the job. I settled on 22ga and rewound the motor. It finished out at 2.8oz (79.4gr) which was lighter than its original 90gr. I attribute this to the now lower copper content and was concerned about its performance.
I tried something new for adhering the stator to the bearing tube. It is a metal version of one of those cut-and-knead, epoxy putty sticks and is rated to 250F. It worked like a charm to fill the gap created by the very loose fit. This stuff is quick set too. You knead it for one minute then have only 2-3 min to work with it before it turns into a rock. I also used this stuff (pressed between the magnets) to balance the bell.
Testing the motor is what surprised me. I tested it with two different props – an APC 9x4.5 glow and an APC 8x6E. I’m not 100% sure the 9x4.5 prop was a glow prop as it looked just like an ‘E’ style prop (not a ‘Scimitar’ style) only much, much heavier build. The test data below looks to be right in line with that from Dr. Kiwi’s test of the original wind. The following values are from memory. I forgot to send the Eagletree data home, but will update them as soon as I get the data.
APC 9x4.5 ‘glow’ (non-Scimitar)
11.5V, 11750 RPM, 25A
11.6V, 12000 RPM, 24A
The odd thing is that after running these tests at around 275W for a minute to two in pusher configuration, the motor was barely warm to the touch. Even after letting it sit for a bit and letting the heat ‘soak’ through, the temperature rise was hardly noticeable. Why does single strand seem to have better power handling capabilities than multi-strand?
|Nov 03, 2011, 07:48 AM|
Why does single strand seem to have better power handling capabilities than multi-strand?
Conventional wisdom would say, for the same volume of wire, lower overall resistance.
Can we use the analogy of a certain volume of water through one big pipe will go more easily than the same volume through dozens of small bore pipes?
|Nov 03, 2011, 01:59 PM|
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