How many turns on a speed 400 motor - RC Groups
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Dec 14, 2001, 12:49 AM
ultramega super star
stealthy's Avatar

How many turns on a speed 400 motor

I read sometime back that the speed 400 7.2v had 45 turns and the 6v had 35 with 28gauge wire I bought some speed 400 @15-20v 9000 Rpms for 60 cents a piece for experimenting on rewinding them myself, but at 28guage wire and 35 turns, the motors on a gunther prop would only pull 3-4amps with moderate rpms, 30 turn @4-6amps with higher rpms, but not high enoungh.I couldn't fit more then 35 turns of wire with the 28guage, I was using 8cell CP-2400 Sanyo's, Does anyone know how many turns there should be. I've tried 24 gauge wire and could only get 16 turns in, and amps where at 20 and to much rpm for the gunther prop.

I know the motors can be bought fairly cheap and ready to fly, but at .60 and .03 of wire per motor,it's worth a try.
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Dec 14, 2001, 10:13 AM
Registered User

400 info

Check out this link. I hope it helps.

Dec 14, 2001, 10:44 AM
Motors beat engines!
Generally speaking:

Thicker wire=more effiencient

Fewer windings= greater amp draw and higher amps that motor is most efficient.

Since you can't get more windings of the theoretically better 24 ga wire on, try using fewer and fewer windings of the 28 ga till your amps are where you want them.

It should be interesting to see if you can get improvements this way.

It should be possible to exactly place your amp draw right where you want it for a given prop and battery.

Your differing amp draw with nominally the same windings has me wondering if your wire has a different resistance than what the motors come with stock.

I'd compare your total resistance to a known good 6v 400 and see if your even close.

Its too bad you could'nt squeeze in enough windings of the 24 ga as you might have had a real gain that way.
Dec 14, 2001, 11:25 AM
Registered User
Here are a couple of resources for rewinding motors. The first is a set of instructions (directed at slot car motors), the second is info about speed 400 type motors.

I tried rewinding a speed 400 using the suggested 28 turns of #24 wire, for use with 6 cell packs. I didn't glue the wire in place at first, and after a short time some of the coils moved and got scraped against the magnets.
Dec 14, 2001, 01:46 PM
ultramega super star
stealthy's Avatar
Thanks for the input and links. The other problem is get the wire as tight as the stock motors, Having to wrap wire 35 turns X 5 really starts to hurt the hands and everything around you starts to distract you from remembering the last number of turns you were counting.

The other problem is the solder staying on at high rpms, I'll try some different solder. I'll have to build a mini Spotwelder when I find the best number of turns needed.

Would a 5 post comm. have any difference compared to a 3 post, This is one reason I can't fit enough 24 gauge, but it must have some effect having more wire. Better efficiency, cooler running motor?

Dec 15, 2001, 12:34 AM
ultramega super star
stealthy's Avatar
I decide to pull apart a Promaxx 400 7.2v and count the turns and to my suprise, only 40 turns on 26 gauge, unlike the Mabuchi 400 7.2 at 45 turns with 26gauge from what I've read, although I haven't torn one apart, Because I don't have any Tired out yet.