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Old 09-09-2008, 07:23 AM   #31
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Also beware of under gearing. I personnally have seen some motors get really hot and seize from that. Being way over reved, That will heat it up a ton also. I know at some tracks I have run,I have geared up and dropped 20* at times....
I have seen the same John. That's always nice, go faster and stay cooler.
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Old 09-09-2008, 12:09 PM   #32
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Every brushless motor that I've burned up has been because of abuse. Some of the motors that are out there don't have a thermal sensor and won't shut off when they overheat internally.

Clamp-on heatsinks with fans will help reduce the external motor temps a lot but probably don't do as much for the internals and rotor. Cooling a motor in any way usually means that you need to gear to a lower temperature at the end of the run to be safe.

I've tried electric cooling 17.5's in 12th before and to be honest, it really only helps for the first 30 seconds or so. Plus if it's humid out (summer) you end up with a lot of condensed water on the motor both inside and out. Condensation isn't a good thing on the sensors especially with a speedo that automatically switches to brushed mode when it loses the sensors (LRP).

I burned up a couple of motors this year due to abuse and it's hard on everything in the car. The speedo gets screaming hot and it's hard on the ol LiPo's. Fortunately, the Tekin that I'm running will desolder it's self from the pack before it burns up.
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Old 09-09-2008, 01:14 PM   #33
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I would tend to think that mayb you guys have just been unlucky. It may just be that you track is hard on motors (large tracks mean you spend more time at high rpms)

I did some motor testing last weekend to compare performance. On a open track I ran 3 3.5t on 5cell till they dumped to compare on track runtime as well as performance. All 3 ran just over 7 mins and went strong to the end. Hottest motor after a run was the LRP (98c/209f) though this motor always runs hot. Even though they were hot all three motors did same lap times until the very final lap. I would say that as long as its not burning hot the temp has very little effect on brushless motors.
Lol

2 possibilities:

1 - I need to know what cells you used !

2 - you're way under geared if you can last 7 minutes with a 3.5T in 5-cell mod !!!!!!
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Old 09-09-2008, 08:39 PM   #34
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Also beware of under gearing. I personnally have seen some motors get really hot and seize from that. Being way over reved, That will heat it up a ton also. I know at some tracks I have run,I have geared up and dropped 20* at times....
What would be under-gearing? like a FDR of 7 for a 13.5 for example?
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Old 09-10-2008, 08:10 AM   #35
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I dunno what sensor whire does what but as this driver at the Japanese nationals did and a lot lot of other drivers. Not al the whires are connected.
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Old 09-10-2008, 03:15 PM   #36
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I dunno what sensor whire does what but as this driver at the Japanese nationals did and a lot lot of other drivers. Not al the whires are connected.
The pic shows only the battery wires desoldered from the pack. The sensor harness and 3 leads to the motor are attached. Looks right to me.
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Old 09-10-2008, 03:21 PM   #37
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I dunno what sensor whire does what but as this driver at the Japanese nationals did and a lot lot of other drivers. Not al the whires are connected.
I know what you mean, some of the actual sensor wires have been removed, but it may be an optical illusion.
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Old 09-11-2008, 01:53 AM   #38
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normally d wire tat remove is d cut off wire meaning d esc wont cut off when d motor overheat...
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Old 09-11-2008, 02:11 AM   #39
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normally d wire tat remove is d cut off wire meaning d esc wont cut off when d motor overheat...
That's what I thought, I would love to know how hot they get those motors!!
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Old 10-02-2008, 02:23 PM   #40
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Just to update everyone on this. I think my theory proved true. Everyone at our track that had been chilling their motors laid off the last 3 races of the season and no motor failures.
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Old 10-03-2008, 02:06 AM   #41
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But the outdoor temps the last few weeks are about 20 degrees cooler than summer.
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Old 10-03-2008, 07:03 AM   #42
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But the outdoor temps the last few weeks are about 20 degrees cooler than summer.
No they haven't been.
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Old 10-03-2008, 07:30 AM   #43
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Some of the motors failing are geared very conservatively (for example this weekend someone had a Losi 10.5 geared at a 5.2 FDR fail). Some of the ones that have lasted all summer are geared very aggressively. The difference I've seen is just the motor cooler. But thanks for your contribution.

not sure 5.2 is conservative it seems low (more like 13.5 gearing) to me.
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Old 10-03-2008, 07:34 AM   #44
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not sure 5.2 is conservative it seems low (more like 13.5 gearing) to me.
5.2 fdr is very conservative for a 10.5 , here in Florida we gear the 10.5's around a 5.2 and the 13.5 in the low 4's.
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Old 10-03-2008, 07:56 AM   #45
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not sure 5.2 is conservative it seems low (more like 13.5 gearing) to me.
we figured out the issue as noted above. it wasn't heat or gearing. it was motor chilling causing the motors to go bad. Heck, since we figured it out someone came off the track at 225 b/c they forgot to hook up their fan and no problems at all.
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