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Old 09-07-2009, 12:43 AM   #1
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Default Correct Gearing

For some reason my Mamba max 7700kv system in my associated B4 gets very hot. It doesn't thermal but it gets super hot. Is my gearing ok?
My gearing is 81 tooth spur and 18 tooth pinion.
I am using a peak racing 4800 mah 2s lipo.

I just ordered this fan https://www.rcplanet.com/ProductDeta...ctCode=INT2902
Should I just screw the fan onto the heatsink?
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Old 09-07-2009, 04:55 AM   #2
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Have you actually "temped" the motor right as it comes off the track?
What may seem "hot" may be just fine....
Does it seem to have plenty of power when you drive it?

Next time you run it temp it after about 5 minutes, you definately want to keep it under 140 degrees, if its over that go down 1 or 2 teeth
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Old 09-07-2009, 08:07 AM   #3
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I don't run the car on the track, I drag race with my friend on his street. I am usually doing WOT runs and we sometimes play tag.
I actually just ordered an onboard temp gauge and it will come on Wednesday or Thursday. I also ordered the 84 tooth spur so I will put that in and check the temp.
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Old 09-07-2009, 09:09 AM   #4
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Do you have any other pinion gears? You've ordered the 84 spur - how about trying a 17T pinion - and try both? You will be quicker off the line (good for dragging) but what's the overall length of the area you run? If it's not super-long, you may be overgeared for what you're doing.

Get that temp gauge working and keep it down to under 150/160F or so. When it goes over 180F, it starts to demagnetize the rotor of the motor. Eventually, it'll keep getting hotter and hotter with the same runs due to the electromagnetics not working as efficiently with a weaker rotor. An "instant fix" is a new rotor or new motor.

You may not know if you have been over 180F over the course of the motor - you may have already started to do damage with it. Check your temps with the new gauge after you get it and if it's over 180F with your next "regular run" then you may have to consider what's been done already to the motor.
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Old 09-07-2009, 09:50 AM   #5
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my hobby shop didn't have any 17 tooth pinions but I do have a 16 tooth, the problem is that you can't use the 16 tooth pinion with the 81 tooth spur, they get too far apart.
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Old 09-07-2009, 10:25 AM   #6
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Understood. Well, if you need that 17T can you order one elsewhere besides the shop - or will they order you one? A 17/84 may be slightly better combination than 18/81 - but again, that temp gauge will be your guide.
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Old 09-07-2009, 10:47 AM   #7
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Ok I will see the temps when the temp gun arrives and see if I need the 17 tooth.
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