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Old 01-03-2007, 02:26 AM   #1
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Default Stock Motor Gearing/Heat

I was after some help from an experienced 1/10th stock 27t racer,
My issue is my motor (Trinity CO27 pro, fully rebuilt with 4499 brushes) temperature is at 190 degrees Fahrenheit after a 5 min run on an open outdoor large track.

My total roll out is 30.5mm ,can under gearing (always running at max rpm) cause motor to overheat?
I was told that gearing could be the issue but i thought that gearing higher would make more heat?

By the way i have the gear mesh and chassis roll test checked & had it checked by LHS as well and it has no binding at all.

could it be a dud motor?

any advise much appreciated
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Old 01-03-2007, 05:51 AM   #2
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This is where I'm confused....some say if u gear it low for acceleration and the motor run at its highest RPM would actually reduce the heat as the motor is running freely....

Some other people said that if you gear it high for top speed and the motor would struggle to drive a heavier load thus generating more heat...

Which is true anyway....???
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Old 01-03-2007, 07:50 AM   #3
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Although I haven't really had a problem with gearing for a long time, I believe if you are geared too far under, it can cause the motor to run a bit hotter as will being overgeared.

How different is your gearing to the 'recommended' at your track.

My motors come off at about 86C, that's on the outside of the can and in our cooler climate.

What sort of ambient temps have you got?

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Old 01-03-2007, 08:06 AM   #4
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And here I have been trying not to exceed 75c. Our ambient temps lately have been around 20c. I was running at 77c, then when running at another track where I gear lower by 2 teeth, my car was just as fast and the temp was at 75c. Splitting hairs, however, I'd rather gear my car lower if it's just as fast.
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Old 01-03-2007, 12:37 PM   #5
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Recomended Gearing for my track is around 35mm total rollout, so i am way under geared i thought.

Ambient temps are from 25c to 35 c

My car is very slow in top speed and does not keep up at all,

i done another temp test and its at 98c (210f) at 30mm rollout as soon as i come off the track.
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Old 01-03-2007, 01:55 PM   #6
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At those temperatures I wouldn't be at all surprised if your motor is demagnetized. Once that happens it loses its ability to put out power, so you'll never get performance from it at a decent temperature.

I'm not exactly sure at what temperature these POS iron magnets are permanently effected, though.
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Old 01-03-2007, 02:21 PM   #7
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So does that meen that no matter how i gear this motor it will always run way too hot? ie: is running way too hot a symptom of stuffed magnets?
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Old 01-03-2007, 02:36 PM   #8
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Quote:
Originally Posted by LOSI123
So does that meen that no matter how i gear this motor it will always run way too hot? ie: is running way too hot a symptom of stuffed magnets?
No
the co27t runs between 2-3 teeth more on pinion then a monster on 48dp
if your 64dp (finer ratios) then between 4-5 teeth more ,then thats about it

the co27t is the most inconsistence motor from one co27 to another
you have to look at the dyno sheet to find out if it`s a revvy one or a torquey one
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Old 01-03-2007, 02:47 PM   #9
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thanks, it says 18,500 rpm @ 5.0v and 97nm torque

what total rollout would you recomend for a out door bitumen open large track with rubber tyres
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Old 01-03-2007, 02:50 PM   #10
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Quote:
Originally Posted by LOSI123
thanks, it says 18,500 rpm @ 5.0v and 97nm torque

what total rollout would you recomend for a out door bitumen open large track with rubber tyres
now i`m buggered ,don`t do Foam racing it`s all rubbers over here (uk)

also the figs for your motor are done with are in a different way & machine then with a ICE or others
so can`t help
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Old 01-03-2007, 02:57 PM   #11
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Quote:
Originally Posted by LOSI123
thanks, it says 18,500 rpm @ 5.0v and 97nm torque

what total rollout would you recomend for a out door bitumen open large track with rubber tyres
Is that from the sticker on your motor can? Here are the numbers from my sticker: 21,844 @5.0V, 64watts, 97.8 nm. Quite a large diff in RPM.
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Old 01-03-2007, 02:59 PM   #12
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that is with rubber tyres, i didnt say foams
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Old 01-03-2007, 03:01 PM   #13
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yes thats the figures on the can from trinity them selves

18,500 rpm
97 torque
58 watts
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Old 01-03-2007, 03:11 PM   #14
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Quote:
thanks, it says 18,500 rpm @ 5.0v and 97nm torque
That moter is better suited to a smaller track where the torque is more important. My motor sticker shows the RPM at 21,307 and torque at 94.9 and is great for my oval pancar. Because of the high temps you've run that motor at you will never get good performance, both the rotor and the can mags are roasted. You could have the can mags zapped and get a new rotor but its easier to just buy a new motor. The next time you buy a motor make sure and check the numbers and match them to the kind of car/track. Higher RPM's for high speed oval or larger less technical track, more torque for the opposite.

Oh and yes undergearing can cause the motor to overheat as well .

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Old 01-03-2007, 03:23 PM   #15
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If you ran the motor right out of the box I would recommend trying it again, but first cut the comm and put new brushes in. Sometimes the comm is not true from the factory which will cause brush bounce and excessive arcing which will wreck your brushes and lower your max rpm. Those numbers on the can are pretty bad though, you certainly could have got a bad motor. If the car runs out of speed really fast on the straight keep gearing it up, undergearing can also cause problems with heat since the motor is very inefficient at high rpm.
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