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Old 09-02-2007, 07:27 PM   #1
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Default cooling brushless motors?

ok we have got our local club to allow 13.5 brushless but we have to run the bonded rotor so from what ive seen thermaling is an issue. so before a pick up a motor and all that i wanna kn ow whats the best way to cool brushless motors down? their sealed so no internal airflow ? i was going to buy the novak heat sink but is that really the best choice short of running a peltier on the car what can i do? cheers
ps why shouldnt i run a peltier? i mean we have huge capacity low resistance batteries lipo which are 200 grams under weight??
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Old 09-02-2007, 07:31 PM   #2
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Eagle Racing has a heatsink with a fan on it as does 3racing. From what I've read, the one from Eagle Racing is much better than 3 racings, but needs a little pressing to fit on Novak motors.
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Old 09-02-2007, 07:46 PM   #3
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in my experience, if the 13.5 is geared correctly it won't thermal, there is a point at which lap times don't go down only the temp goes up, find that point and all should be good, for me it was 5.4 on the indoor track that paved nats was run on, some go to down into the 4's but aren't any faster. large outdoor track i ran a 4.7 at 170degrees, went to 4.9, temp dropped to 155 and lap times didn't change.
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Old 09-02-2007, 09:32 PM   #4
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Bonded stock Novak rotor:
I found that running the bonded rotor you can run the heck out of them for 2 weeks then you have to really watch the temp.

At 130 degrees and under you can get 3-4 weeks out of one, maybe more.?
At 120 and under you will see a speed difference on the coarse it will be a bit slower than the rest of the 13.5's geared at 140 and up. But will last longer.
But at 130-135 it was as fast as any other on the coarse. Driving skill was the key. I had the motors figured out, but was lacking the skill against the fast guys.
Have a bonded rotor on hand, you will need it. And you will likely see a lot of thermoling. Every one will be pushing as close to melt down as possible. Keep it at 130 and it will be fine.
As the rotor gets weaker it will start to run hotter, so thats when you know its time to replace it with a new and only use it for practice. Save your newer ones for racing. I personally think the stock bonded have more top end RPM.

If you gear an old rotor to where it just thermals and then put in a new one you will better see what I'm trying to say.
Thats what I came up with on a n indoor carpet track running foams on an medium size track.
Try to get into the sintered rotors or the new 13mm. Its cheaper in the long run and they will last longer.
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Old 09-02-2007, 09:41 PM   #5
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Quote:
Originally Posted by aus jd 2703 View Post
ok we have got our local club to allow 13.5 brushless but we have to run the bonded rotor so from what ive seen thermaling is an issue. so before a pick up a motor and all that i wanna kn ow whats the best way to cool brushless motors down? their sealed so no internal airflow ? i was going to buy the novak heat sink but is that really the best choice short of running a peltier on the car what can i do? cheers
ps why shouldnt i run a peltier? i mean we have huge capacity low resistance batteries lipo which are 200 grams under weight??
[QUOTE=UN4RACING;3636644]Bonded stock Novak rotor:
I found that running the bonded rotor you can run the heck out of them for 2 weeks then you have to really watch the temp.

Try to get into the sintered rotors or the new 13mm. Its cheaper in the long run and they will last longer.[/QUOTE]

He can only go with bonded rotors.
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Old 09-02-2007, 10:02 PM   #6
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[QUOTE=bxpitbull;3636671]
Quote:
Originally Posted by UN4RACING View Post
Bonded stock Novak rotor:
I found that running the bonded rotor you can run the heck out of them for 2 weeks then you have to really watch the temp.

Try to get into the sintered rotors or the new 13mm. Its cheaper in the long run and they will last longer.[/QUOTE]

He can only go with bonded rotors.
We (HAD) the same rule. They will come around.
Push for the sintered and get it over with. You will save a small bundle of money and a lot of head aches.
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Old 09-02-2007, 10:12 PM   #7
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If you put an additional clip-on heatsink it may just insulate the heat even more. Try getting the Novak one which actually makes contact with the inside of the motor, or just finding the correct gearing.
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Old 09-02-2007, 10:23 PM   #8
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Originally Posted by Tek Nickal View Post
If you put an additional clip-on heatsink it may just insulate the heat even more. Try getting the Novak one which actually makes contact with the inside of the motor, or just finding the correct gearing.
Contact with the inside of the motor? Did you see what you just typed?
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Old 09-02-2007, 10:39 PM   #9
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It makes sense because if you remove the stock purple band, that is the inside of the motor.
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Old 09-02-2007, 10:43 PM   #10
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Originally Posted by BlueBird-sr View Post
It makes sense because if you remove the stock purple band, that is the inside of the motor.
Thank you for pointing that out...I didnt know that. Thats a first, the pitbull has been STUMPED on a Novak product.
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Old 09-02-2007, 10:46 PM   #11
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Quote:
Originally Posted by Tek Nickal View Post
If you put an additional clip-on heatsink it may just insulate the heat even more. Try getting the Novak one which actually makes contact with the inside of the motor, or just finding the correct gearing.
I'm sure you meant the outside of the can.

But the biggest problem in slow motor racing is over gearing. I have raced stock sedan a lot for four years and over gearing just seems to be a big problem with most stock racers. Instead of going to a faster motor, they gear up.
I don't know if I have ever seen any one running stock that wasn't over geared.
Correctly geared is the key but few will do it.
I think Much more is the fan I bought. Its still in the pit box never used it but once or twice.
To each his own, but I think the fans are over rated.?
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Old 09-02-2007, 10:48 PM   #12
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Quote:
Originally Posted by bxpitbull View Post
Contact with the inside of the motor? Did you see what you just typed?
Oops, I meant that it replaces that purple band in the middle of the motor.
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Old 09-02-2007, 10:50 PM   #13
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Originally Posted by BlueBird-sr View Post
It makes sense because if you remove the stock purple band, that is the inside of the motor.
Yeah hes talking about the optional Novak that replaces the stock ring. And not a clip on.
To bad they don't make one with a fan, that would be worth a try.
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Old 09-02-2007, 10:50 PM   #14
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UN, I dont know about for stock, but for modified, they work wonders. You know I am all for gearing to run and win, not to thermal (where have I read that before?????), but to keep the temps in total check, a fan on the heatsink works wonders. I havent run a stock motor and have not a clue when it comes to set-ups, but for modified, run the fan. If the sleeve replacing one had a fan, THAT would be sweet. Sounds like something I may buy and fabricate myself.
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Old 09-02-2007, 10:58 PM   #15
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Quote:
Originally Posted by bxpitbull View Post
UN, I dont know about for stock, but for modified, they work wonders. You know I am all for gearing to run and win, not to thermal (where have I read that before?????), but to keep the temps in total check, a fan on the heatsink works wonders. I havent run a stock motor and have not a clue when it comes to set-ups, but for modified, run the fan. If the sleeve replacing one had a fan, THAT would be sweet. Sounds like something I may buy and fabricate myself.
I believe you. I have been running mods out side in the dirt. I have still not had any issues. I just make make sure its geared right. Now I can see how mod sedan would differ that close to hot ground. On throttle time is greater. The fan on top of geared correctly is a good Idea, I think its proper use of it. I'm with you all the way.
But I see people trying to gear up because they have a fan. Maintaining the temp is a smart use of one. Using one to gear up is not a good purpose of one. I just think over geared is over geared at that point.
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