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Old 05-14-2008, 05:11 AM   #1
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Default Heat problems: HPI Rally RS4

Hi guys, some of you may remember the Pro 2 turned into a rally car by the means of a polycarbonate tray on the top and bottom to give the driver more confidence when driving through gravel pits with a belt drive car...

However, after a run to test how the drivetrain was holding up to my Mamba Max 6900kV motor, it was the mamba that was closer to breaking point.

After picking it up and opening the cover, I touched the heatsink and burned my finger. It had that post-burn-feeling last night, but now it is fine. I don't know if that will better gauge the temp.

My question is that I believe I am going to have lots of temp problems. I had been using a TT-01 which was a 20:61 ratio and the 31T (I think):81 spur gear was a bit much. I do also have a 91T and a larger spur gear that is purple from HPI--I dunno how many teeth that has.

However, I think the main problem is lack of circulation. Is there point to putting a fan in a chassis that basically traps the heat? Should I open a hole just in front of the ESC so air can flow through it, and another larger hole in the back so the air has somewhere to go?

Also, there is no room for a heatsink for the motor. Is there any low profile heatsink that is effective?

If this all fails, I will take off the cover. However, one of the reasons I got this was to use the cover (but mainly for the higher clearance. My area is very bumpy/hole-y).



Also...I really can't fit my ESC that well in this chassis. There is basically no room next to the belt.

Thanks in advance for any responses!
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Old 05-14-2008, 05:15 AM   #2
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When I ran my rally (with the cover), I cut a couple of holes in the inner body to help with cooling..

I think I had one in the driver's lap, one in the back by the motor and on behind the drivers (or passengers) heat rest...

I then covered the holes with some pieces of window screen

It worked in all way - I never overheated anything and the screens helped keep most of the gunk out of the inside
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Old 05-14-2008, 05:19 AM   #3
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I guess you could always try to find room for a fan to help?
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Old 05-14-2008, 02:05 PM   #4
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Thanks K, I think I will try that.

Maybe if I combine that with some fans (any recommendations for fans? I will do some reading, but I am curious how you guys put them in in terms of power source and WHAT fans.)

I bought an integy heat sink with fan, and the fan was running off of 7.2V, but would overheat and stop working. hmm...
---

I also forgot to say, I wasn't sure how effective a fan was if it was just circulating hot air. That cover is basically an igloo, and the fan would just convect the heat around. So maybe if I cut holes and used fans it would work?

Is there anything on towerhobbies in terms of decent fans that people have used?
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Old 05-14-2008, 07:21 PM   #5
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I would cut holes like the previous poster suggested, but also make sure you have the correct gearing.
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Old 05-15-2008, 07:15 AM   #6
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Cutting holes in the inner body with a fan should work, but bear in mind if you're in a dusty or in general dirty terrain the bad air will get sucked into the motor...

If you dont think the surface will get into the inner body that much through the said cut holes, then it could help

It is a bit of hassle though. Probably just cutting holes sounds like the best all rounder solution
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Old 05-17-2008, 08:29 AM   #7
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cut a hole and install a dc fan to blow air into the inner body. try to find a place where has the most clean and cold air for the fan's intake.
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