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Heat in on road motorand gear ratio

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  • 1 Post By F1fletch
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Heat in on road motorand gear ratio

Old 08-10-2020, 12:16 PM
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Default Heat in on road motorand gear ratio

I race on-road in florida. the two track are the exact same tracks I race on. One is outdoor asphalt and the other is indoor black carpet with no a/c. I have been running the two track with the same gear ratio and never had a problem with motor temps. Now that it is really hot the temps on my 1/12 went for 90's -115 to 175,215 and one tooth change in pinion 197. (with fan). I've never run a fan in my 1/12th. Motor used has been checked out and it is fine. Placed a new motor in yesterday with a fan at the indoor track. the highest my motor was 141. I did change the gear ratio by 4 teeth on the pinion (56---52). I was not as fast as I have been. With high temps here in florida how does that effect the motor in a race. I have tried raising the drive freq. in the esc from 2-8 (hobby wing). I want my old performance before it got really hot . Do I go higher on the drive freq on just have to got slower and be less competitive in my class (different gear ratio).
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Old 08-10-2020, 02:08 PM
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Put a fresh rotor and bearings in.

As long as the motor doesn't get hot enough to roach through the plastic insulation on the stator windings, the rotor and the bearings are the only heat wear items. Brushless motors are very tough. Rotors are a wear item, but until lately, brushless motors were evolving as fast as our rotors were wearing out. So we just bought new motors. Weak rotors will also make the motor run hotter.
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Old 08-10-2020, 04:38 PM
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the Rotor is not weak- 1700. Now compairing my two motors I see why one was faster-RPM. But I was just trying to figuire out the hot land and track temps to the same gear ratio I've been running. I was competitive with the 3 fast guys until this weekend. New motor and new gear ration but did not have my normal speed. I was trying to get rid of the heat and keep in lower. Now I'm going back to my old motor with the new gear ratio but the next race is asphalt. Still would like to run my old gear ratio without cooking the motor. would the drive freq help by raising it higher?
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Old 08-10-2020, 07:19 PM
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Nope. Go low.

Try fresh bearings I guess.
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Old 08-10-2020, 07:38 PM
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I have compaired both motors on my motor machine. (new and old) the motor that took all the heat was completely gone threw with no ill effects except a shim- so I was told. I also have the motorlyser sheets on both and have my cheap motor machine results. I don't rebuild motors I let the pro's do it. I will be installing my old motor back into my car as it is still better than my new one. I basically have 3 more races in the Florida heat (August- September). Just wanted to find about the heat effects and how to lower it without a fan.
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Old 08-10-2020, 07:45 PM
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My .02. Keep the motor under 140. I was running a bit over and halfway through the race, I lost a lot of grunt. I later found out the motor was timed a bit too high. If you have a good cooling fan and are hitting those motor temps you need to gear down. You won’t make more power with more gear or timing at that point. Also remember higher drive or brake frequencies while smoother develop more ESC heat so that could be a consideration as well. Our temps are close to 100 with track temps over 140 for a large part of the day.

Run a fan ....even with blinky you need it. Cooler runs faster
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Old 08-10-2020, 08:35 PM
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well heat is only transferred by a couple methods. conduction, convection, and radiation. A fan would help with convection but if that is a no go then you have to focus on the other two. add thermal paste or a heat sink or a vent or ... adding metal to transfer the heat to allows the heat to be distributed more evenly as long as the metal surfaces are bonded well.

has your friction changed?
has your timing changed?

are you running the same body indoors versus outdoors? airflow through the body helps.

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Old 08-11-2020, 02:23 AM
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The two bodies I use are the same for each track I only run one out door and one indoors. the tracks are the same both times I ran them .My next race is the outdoor track- I switch bodies and ride height . Same tires just don't true them down that low.
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Old 08-11-2020, 10:54 AM
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Originally Posted by BullFrog View Post
I race on-road in florida. the two track are the exact same tracks I race on. One is outdoor asphalt and the other is indoor black carpet with no a/c. I have been running the two track with the same gear ratio and never had a problem with motor temps. Now that it is really hot the temps on my 1/12 went for 90's -115 to 175,215 and one tooth change in pinion 197. (with fan). I've never run a fan in my 1/12th. Motor used has been checked out and it is fine. Placed a new motor in yesterday with a fan at the indoor track. the highest my motor was 141. I did change the gear ratio by 4 teeth on the pinion (56---52). I was not as fast as I have been. With high temps here in florida how does that effect the motor in a race. I have tried raising the drive freq. in the esc from 2-8 (hobby wing). I want my old performance before it got really hot . Do I go higher on the drive freq on just have to got slower and be less competitive in my class (different gear ratio).
I've had some of the same issues on black carpet track w/o a/c. When it's 90º + inside, my motor seems to go up 15-20 more degrees than normal. Not sure what the answer is without losing gearing and or timing.
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Old 08-11-2020, 11:04 AM
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Did your timing slip?
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Old 08-11-2020, 12:25 PM
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No it did not slip.
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