G12 motor performance drop off

[jenson46]

Can any of the slot car motor builders out there please tell me why I am experiencing performance drop off with my G12 motors? Both races that I did last weekend resulted in both motors losing power after the first 3 heats. During practice and qualifying the motors were great, even with some choke and during the first 3 heats were fine. Then there was an obvious loss of power with lap times dropping off by about 0.2 of a second, despite turning the choke off. Both motors are Cahoza setups, which have been reconditioned and honed to .560 air gap with Proslot .540 dia, 45 degree arms. These have been com trued and rebalanced. The springs used are Cahoza light 3 coil. Any information would be much appreciated.

[Sam pan]

What did the comms look like after the race? I'm no motor guy but I'm going to guess it's a brush issue. What brushes are you using? How do you break in the motors?

[hesketh]

There are a couple of likely suspects in rapid performance drop off, heat build up and brush failure. Heat can be caused by a small short or tight spacing that gets worse as heat builds up, or not enough spring tension (that also contributes to brush failure), it's hard to pinpoint from the info you gave. But medium springs, shunts and spring insulation should help if it's a brush problem and check the motor for shorts either in the arm or through the can/endbell. A short won't necessarily stop the motor from working but it can cause extreme heat build up which will kill performance over a couple of heats. These are a few things to check and a place to start.

[hesketh]

OR it might be as simple as dropping a tooth on your pinion. With a big airgap, high timing and thin magnets maybe you need a lower gearing.

[zipperi]

I mostly have killed/made slower my G12 Motors with too big pinions + too soft tires.

[Forsyth Racing]

What kind of track are you racing on??. Big arms are only good on a flat track.

[jenson46]

The track I was racing on at the weekend was a 170 foot flat track with 2 long and 2 medium straights. Corners are mostly slow to medium speed. I forgot to mention that the motors are both shunted.

[Forsyth Racing]

I would gear it 7/42 72P where is this track located??.

[jenson46]

Track is located in Wellington, New Zealand. http://www.zippitynz.com/_images/Slo...C/Track800.jpg
I have tried 7/42 on this track and it doesn't work. Chris Radisich raced at our Nat's here a few years ago and he tried 7T, but went quicker with 8T.

[Forsyth Racing]

You may have a brush hanging up or the arms are bad.

[Zippity]

Welcome to my world

At race time, my super fast G12 turned out to be a flop.

I am still pulling my hair out, trying to figure what went wrong

[Greg N]

All of the above is accurate. I'd add a partially bound up axle bearing or bushing as a possible cause.

Keep looking, you'll find the reason!

Greg

[jenson46]

Thank you everybody for your suggestions.

[cwendel]

Make sure the magnets have a full charge before the race starts. Sounds like the magnets lost charge as soon as the race started. You need to close the airgap up a little to deal with the field dropping during the race. Also use a heatsink on the motor between heats to cool the motor and save the magnets. I have a 12 that needs to have the magnets zapped every race or it is a dog after 3 heats into the second race geared 7/41.


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[swodem]

Just make one fix at a time until you see an improvement. I would true the com then try it. If that makes no diff, zap it. Still no change, try a different arm same diameter etc.
then you'll find the issue.


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