Question about group 12 motors.

[The Joker]

Monty,riddle me this. I race on a 155 blue king track, probably a little flatter than most. It has three taps and uses a combination of a 75 amp power supply and 2-8 D batteries, the voltage is usually set at 14.2 volts. When I run on the track alone my lap times are around the high 3.2 to mid 3.3 seconds. When there are more than 3 racers on the track my lap times go to 3.4 to 3.5 seconds, this is inspite of any traffic problems that may arise. By the 5th heat on the lap times are religiously mid to high 3.5 seconds. The setup I have used has included Mura, Mura cryo,Proslot blue dots and SMQ magnets to which I have zapped prior to, after and not at all. I have tried Big foot and Gold dust brushes. I have used Koford, Champion and Mura springs of multiple tensions. I have tried Koford, Proslot, Mura, Champion, and RJR cans and endbells. As well I have tried Koford and Proslot arms of mutiple timings. My question is, is this drop off normal? It doesen't seem to effect the guys I race against as much as me. As a matter of fact some seem to get faster towards the end of the race. I understand that some can be attributed to brain fade, but still I think there should be at least one hot lap in there somewhere. The car and the motor setup never seem to have a bind so I don't think the car is tightening up. From some of the previous posts I would say from the power indication that this would be a low power track, is this correct? I more or less confirmed this by trying the SMQ setup and it responded to the suggested pinion change, it also ran hotter than normal inspite of the smaller pinion=more revs. If this is right, and I know you have covered this before, should I be running a high timed arm 42 deg and up and low power magnets? Or should it be low timed arm with high power magnets? OR should it be high timed arm with high power magnets OORR should it be low timed arm with low power magnets??? I think I've tried it all but I am open to suggestions. I also would like to know about arm spacing in a setup. I have seen both spectrums on this, from arms that just barely keep the com from falling out to very minimal side movement, I know that having the arm centered in the magnetic field is important for efficency but one guy that is blistering fast sets his up just enough to keep the com from hitting the brush hoods and enough to keep the arm from falling out the gear side but thats it, I'd say he has at least 1/8 of a inch of slop in the setup. Is there something there that I'm missing? Could this side play be used as a way of cleaning the face of the brushes each time he puts power to the motor? One more question, where is a viewable and preferable downloadable version of the newest USRA rules? All I can find is the 2000's, anyone????

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Joker,

If all of that is a regular trend, then yes, its the track power. To minimize the difference between practice and race laps, a few more power taps are probably desireable, and maybe of a heavier guage.

Lets assume, however, that the track owner is not about to rewire to suit your desires. With modest power, I'd try high timing with medium magnets first. Then, go progressively weaker with the magnets and see if you can get power back out. Run fairly low gearing no matter, as its never good to strain the motor even if there isn't enough power to fry the arms. Lower timing will reduce the difference between practice and race times, but not make you any faster (i.e., probably slower in both ranges). Avoid various causes of drag, to include running too much air control or too much tire.

As for armature spacing, you need to be careful to avoid binding, but there isn't any advantage to being sloppy. The possible downside to excess endplay is variable gear mesh.

The 2002 rules have to be out there someplace, but its the 2003 rules, with lots of new motor options for Gr.12, that you need to watch out for.