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Old Aug 24, 2006, 07:05 PM
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BlazerB52's Avatar
Fenton,MO USA
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What is the maximum allowable Air gap(mag& stator) for GBx build?

Got parts to build GBx motor. Single, Double and Triple and 22.7mm stators. When I try to use the magnets I have:

5x4x1mm flat
5x5x1mm flat
5x5x1 curved
5x5x2mm curved

I either have to big of Gap? Or the mags rub the stator. Do you have to turn down the stator.

Same problem with 20mm build also.

Using the bought stators, not stuff robbed out of cd-roms.
Thanks
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Old Aug 24, 2006, 07:37 PM
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fly_boy99's Avatar
San Jose, California, United States
Joined Oct 2004
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Your best answer is to go consult the GoBrushless rotor
calculator.

Try and get between .15 and .30 airgap... of course lower is better.
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Old Aug 24, 2006, 07:46 PM
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olmod's Avatar
Australia, VIC, Cranbourne East
Joined Apr 2004
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On the gobrushless site there is a caculator for working out drum sizes for flat magnets,the magnetic gap controls a ballance of torque and speed the closer the gap the more torque and efficiency is what ive found from experience generally speaking. do not try and turn the stator down the legs of the teeth will bend out of shape no matter what others say,what you can do is use a fine flat mill file or a diamond file and while spinning hold against the stator and you can reduce the diameter that way without distorting the teeth.hope that helps . cheers
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Old Aug 24, 2006, 08:07 PM
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Wanted to ask because it seems that half the stuff I am building seems to have a rub issue. And have not read on here(rcgroups) people with this many problems. Just wondering if I am doing something wrong or is it just part of the build process. Have a 20mm double and can barely get a .002 feeler guage between the stator and mags. The stator ends do not have enough to file down to get bigger gap. Used 1mm curved magnets. Do they even make .9mm curved to use instead?
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Old Aug 24, 2006, 08:27 PM
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The 22.7 stator build on GOBrushless site I was trying to duplicate build #GBL_00015 which is 14T of 24 Gauge(man that was hard to wind)WYE 5x5x1mm mags N48
12 magnet poles

Says I should have a air gap of .9928mm---seems large to me?
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Old Aug 24, 2006, 08:33 PM
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Quote:
Originally Posted by BlazerB52
Wanted to ask because it seems that half the stuff I am building seems to have a rub issue. And have not read on here(rcgroups) people with this many problems. Just wondering if I am doing something wrong or is it just part of the build process. Have a 20mm double and can barely get a .002 feeler guage between the stator and mags. The stator ends do not have enough to file down to get bigger gap. Used 1mm curved magnets. Do they even make .9mm curved to use instead?
are you sure you don't have excess glue sitting on the magnets facing the
stator shoes ? what I do is this: when mags are in position I put a bead of
medium ca on top between mag and flux ring...once dry I remove the
magnet spacer, throw the can by the shaft on the dremmel and then I roll
the can by hand one rev while dripping thin ca as it goes around. Without
wasting time I grab a toilet-paper tube, put the can in it and spin it.
Finally, I use medium ca between the mags and spin that too with the
dremmel. After an hour or so I take an xacto blade and carefully clean the
mag surfaces...no rubs. The GBx stuff is designed for no rubs _provided_
the stator was not distorted during pressing it on the bearing tube.

Peter
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Old Aug 24, 2006, 08:34 PM
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Quote:
Originally Posted by BlazerB52
The 22.7 stator build on GOBrushless site I was trying to duplicate build #GBL_00015 which is 14T of 24 Gauge(man that was hard to wind)WYE 5x5x1mm mags N48
12 magnet poles

Says I should have a air gap of .9928mm---seems large to me?
yes, this is too large a gap. If you're using the GBx bell+flux ring then you
should use 5x4x2 mags or the GBx curved mags from www.strongrcmotors.com

Peter
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Old Aug 24, 2006, 08:43 PM
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Fenton,MO USA
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I use the spin bell in drill with paper tube method. Also I go back with x-acto knife and clean any glue off magnet surface. I am using Black CA to glue magnets. Magnets that I was going to use are the curved 2mm magnets and I don't have a gap. When i put measurments in the gobrushless rotor calc says I have a negative gap. Put 2 magnets(oposite each other) in bell and slipped on stator and just barely able to go in. No gap. All my stuff is GBx.
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Old Aug 24, 2006, 09:23 PM
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olmod's Avatar
Australia, VIC, Cranbourne East
Joined Apr 2004
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try blueing the ends of the teeth with a black marker pen when dry try a turning fit into your drum then examine the rubs on the teeth ,you may have an off centre stator to bearing tube situation and the only way to fix is to dremel sand away the high spots that have rubbed and recheck.that is if the drum is true to the shaft.
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Old Aug 24, 2006, 09:50 PM
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Quote:
Originally Posted by BlazerB52
IMagnets that I was going to use are the curved 2mm magnets and I don't have a gap. When i put measurments in the gobrushless rotor calc says I have a negative gap. Put 2 magnets(oposite each other) in bell and slipped on stator and just barely able to go in. No gap. All my stuff is GBx.
something's wrong...the ID of the GBx can is 27 mm, the stator OD is 22.7,
with 2mm curved mags you have an airgap of 0.15mm. The GB calculator
only works with flat magnets. Can you post a link to what can you have ? is it
like this ?



Peter
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Old Aug 24, 2006, 10:23 PM
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Here is pics of some of my stock. Measured cans and these are the measurements. They are GBx.

27.15
27.17
27.13
27.18

22.64
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Old Aug 24, 2006, 10:40 PM
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you got the right parts...I guess you have to determine where the rubs are
to figure out whether the flux-ring got distorted upon pressing it to the end-bell
or the stator got distorted or the shaft is out of alignment.

Peter
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Old Aug 24, 2006, 10:49 PM
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I use a small pinion press. And when I spin stator in the bell. I dont see any wobble. Feeler gauge seems to be the same all the way around bell between mags and stator..
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Old Aug 24, 2006, 11:08 PM
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Quote:
Originally Posted by BlazerB52
I use a small pinion press. And when I spin stator in the bell. I dont see any wobble. Feeler gauge seems to be the same all the way around bell between mags and stator..
so what makes you say you have mags rubbing on stator ? sound ? can it
be coming from the bearings ? the 2mm curved mags make the can slam
onto the front bearing if you don't hold onto it as you're inserting it.

Peter
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Old Aug 25, 2006, 12:23 AM
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The feeler gauge I am using is only .002". For 20mm motor.

And that is even a chore to get it in it.Thats why I was asking the original question.

That is why I think it is why it is still rubbing. Put some marker on stator and is okay hand turn. But when I chuck it up in drill it rubs a little in the center where two stators are joined. I have sanded it down as much as I feel safe. That is why i was asking for help was not sure if my parts are the right stuff(magnets,ect.)

Some of the confussion is my fault I am building two motors at the same time a 22.7mm and a double 20mm. Both have same issue: 20mm has magnets glued and rubbing, but 22.7 does not have magnets glued due to fit issue.

By the way I appreciate the help.
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