Very Wierd Motor Problem

[A Gower]

hi,

i was racing buggies last saturday, and everything was find nutil i decided to get my motor skimmed by someone there, first of all the armature was a brand new infinity handwound pro armature and was in mint condition with a orion core can and endbell, however i did notice on the armature that the windings were coverd in what looked like plastic. but anyway i was watching this person skim the motor and he was doing it a very wierd way, he had the tip set in the middle of the comm and moved it in until it touched and then moved it sideways along the length of comm but not in a smooth movement he did it in little bits, turning the wheel a quarter of a turn at a time. he also didnt go right to the end, it was left with a unskimmed bit which is about 0.5mm long on the winding side. i didnt think this would make any differnce so put the motor back together and put my car down on the track for the start of the final where i had qualified 1dt in B and to my horror nothing happened, the car just sat there. but after checking it at home i found that the armarure just wont spin inside the can, and i have tried it in a differnt can and still it wouldnt spin. i also tried a differnt arm in both cans and they worked fine.

so i have narrowed it down to the armarute and;
Will they way he skimmed it stop it from working atall?
Will leaving that unskimmed bit stop it from working?
And are the infinty armature ment to have this plastic covering the windings and would this stop it from working?
And one last thing if i cant get it to work should i take it back to the person and get him to sort it out or buy me a new one? as i no it has happened through no fault of my own!!

Many thanks
A Gower

[DA_cookie_monstA]

The plastic coating is called Potting the windings, to stop them from moving so the armature stays in balance.

Often when skimming, you don't take the skim right the way to the bottom of the comm to protect the bit of your lathe, but he seemed to do it a VERY strange way indeed.

The fact that the armature will no longer spin in the can seems to me more a shimming problem (too many shims), I would check this first, if curious you can put the armature into each bearing individualy and check it spins, then assemble the motor.

If you are not use to stripping and rebuilding motors, I may suggest you take it to someone you know who can (preferably not the guy who skimmed it) and get them to build it.

[A Gower]

the armature spins in both bearings and i origianly thought it was the shims so i took them all out minus the fibre washer still didnt make any differnce.

i have been rebuilding my motors for the past 4 years without any problems and proberly know more than the person thta skimmed it, unfortuetly the lathe belongs to the club and only the adults that run it are allowed to actauly do the skimming otherwisw i woudl do it and would proberly do a better job!!

Thanks for you help
A Gower

[tyreman]

I have recently hade problems with my team motors where the armature became stuck in the can now this seemed to be caused by, very hot ambient air temp think it was about 30deg C thus added with the heat the motor generates = extreamly hot motor.

At first i thought that I had left a shim floating around in the motor but this was not the case. Tha cause of the problem was that due to the heat the armature segments (not the copper) had expanded ever so slightly thus causing them to rub and grind on the side of the magnets in the can,
but when I put a new armature in it was fine this could have been the case with your motor and not the fault of the person that skimmed it for you.

At the end of the day we all have our own different ways of skimming a motor, so to put the blame on someone who has done you a favor by skimming your motor for you is a bit unfair, as next time you need a motor doing he and others may now refuse incase they end up being blamed for something they have no control over.

Now if they take a dirty great big chunk out of your comm then there is a case for complaint but I would be very careful in how you put this matter to the person in question.

[Southwell]

That is a very wierd way of skimming! Still the best way to ensure its done properly is by buying one and doing it yourself. They are pretty reasonably priced

[burgie]

have you checked in between the segments of the comm for swarfe?

I presume you mean the armature will not spin when power is applied to it - a little bit of swarfe would cause a "short" and the motor would not spin.....

[A Gower]

i would get a lathe but i just cant afford it. and yeah i checked down the gaps between segments and its perfectly clear!

and as for the armarue segemnts (not copper) expanidng slightly, it sounds the most reasonable explanation yet but i was racing in the rain and it was about 15'c but the motor did come off hot, is this a standard thing that happens to infinity armatures? and is there anything i could do to fix this?

many thanks
A Gower

[A Gower]

ive fixed the problem it was just where the windings join the (arm comm) one of them had come loose and wasnt touching but now ive fixed it and it works fine.

Thanks to anyone the helped
A Gower

[tyreman]

I would send it back to Infinity or lesro if the winding have moved or come loose as it will inevetbly do it again see no problem as to why they wouldn't replace it for you

[Southwell]

if the windings comes loose the arm is useless and wont work properly so send it back for a replacment.