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Old 04-13-2005, 08:40 AM   #1
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Default Motor - magnetic field center?

I hear terms bandied about where builders "center the armature" in the can's magnetic field.

Can someone tell me how you can tell when or if your arm is centered properly?
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Old 04-13-2005, 09:10 AM   #2
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Take out all shims in the motor and reassemble. Spin the armature a couple of times and it will rest in its natural magnetic field. Then put shims back in accordingly.(top , bottom) A properly shimmed motor will make more power and run smoother.
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Old 04-13-2005, 10:32 AM   #3
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For stock motors (bushings) I would suggest you shim both ends until the arm rests in the field center and there is less than a millimeter of space that it can travel outside of the center either way. The closer the better, without being snug. I also recommend using at least one teflon shim at each end to provide the least amount of friction when the arm moves (due to cornering forces) and causes the shims to rub against the bushings.

For mod motors (bearings) you can shim it snug but not tight. Most of todays high-end motors come with o-rings that fit the arm snug, but beware that the arm may be pushed ouside of the field with o-rings.
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Old 02-03-2007, 12:52 PM   #4
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what if your motor wants to pull towards the pinion side always? I have a co27 that was only run once, it was overgeared at first, but I fixed that. Do the magnets need to be rezapped?
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Old 02-03-2007, 01:10 PM   #5
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Originally Posted by MikeXray
what if your motor wants to pull towards the pinion side always? I have a co27 that was only run once, it was overgeared at first, but I fixed that. Do the magnets need to be rezapped?
just place a thin teflon shim in each side and thats it , once the motor spools up it will go to the center of the magnetic field on its own, if you shimm it just a little bit off center it will bind up once the motors spools up . I ran motors on my Turbo 45 dyno with the armature shimm in center and then the armature with 2 thin teflon shims and accorging to the dyno the motor with the teflon shimms averaged between 5 to 8 more watts and atleast 2,000 more rpms.
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Old 02-03-2007, 01:20 PM   #6
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Shimmed higher toward endbell will increase RPM slightly, Shim toward bottom of can will increase tourque slightly. Yes never shim totally with no play either.....
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Old 02-03-2007, 02:00 PM   #7
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i`m following you John

shimming in 27`s with bushing`s ;;

take shims out both ends put arm back in ,endbell on & fasten the screws down as the timing ring comes up to clamp endbell down the magnetic field changes due to the metal timing ring ,ping the arm around (spin it,make sure arm is free in bushings ) then add shims till there is a nats play either end of arm,allways use phenolic washer on comm end

if you just put endbell on can by finger pressure this gives you a false reading,

Note;;when power is applied to motor the arm will move one-way or the other any way ie;;spool up it could push against endbell,,off power it will push against can end or vica versa,till it`s settled then sits in middle (which is very rare coz we are all ways on or off power
i use nickle shims ,since the magnets don`t mess with them

there are a couple of very fast 27 drivers over here that don`t use shims atall & the arm floats around like a Pr@~k in a bucket & do very well


this does not mean i`m right ,it` works for me just passing Good info
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