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Old 04-15-2008, 10:45 AM   #6076
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Hey Mitch,

I have seen this sort of thing happen before because of the very low internal resistance that lipos have... when you pull alot of current through them the voltage will tend to drop very hard compared to a nimh ...the way the circuitry works is that it can only "see" the voltage and if the voltage drops out below a certain level these "blips" can occur.
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Old 04-19-2008, 11:19 PM   #6077
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Steve, I was talked into upgrading my 10.5 GTB combo to a 3.5motor. The speeds are decent (50mph????) with my Xray T2 but the GTB wants to thermal after 3min with the gearing recommended. So I reduced the gearing to 15Pinion / 120 Spur. Pulleys are stock: 20/32. This would be the smallest gearing I can go without the underdrive pully set. The speeds are still ok but GTB is close to thermal at 3min. GTB showed 170's The motor temp is about 130's. I am running rubber tires also.

What can be done to get the temps lower so I can worry less?

The track is a large and smooth outdoor nitro track with back straight 180' long so I would like to increase the gearing if possible. I'm not sure of the top speeds but when I was geared in the 10:1 area the car felt the quickest around the track and would make a nitro car look slow. I also only break at one infield corner since the track is a fast and not real technical. The rest of the track can be had just by releasing the throttle some.
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Old 04-20-2008, 12:41 AM   #6078
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Gearing too low can sometimes cause thermalling issues as well.

It sounds like your previous ratio of 10.0 was closer to what you would need for a large track like what you are describing...were the temperatures 170 on the ESC with that gearing as well?

How old is the GTB in question...?

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Originally Posted by trailranger View Post
Steve, I was talked into upgrading my 10.5 GTB combo to a 3.5motor. The speeds are decent (50mph????) with my Xray T2 but the GTB wants to thermal after 3min with the gearing recommended. So I reduced the gearing to 15Pinion / 120 Spur. Pulleys are stock: 20/32. This would be the smallest gearing I can go without the underdrive pully set. The speeds are still ok but GTB is close to thermal at 3min. GTB showed 170's The motor temp is about 130's. I am running rubber tires also.

What can be done to get the temps lower so I can worry less?

The track is a large and smooth outdoor nitro track with back straight 180' long so I would like to increase the gearing if possible. I'm not sure of the top speeds but when I was geared in the 10:1 area the car felt the quickest around the track and would make a nitro car look slow. I also only break at one infield corner since the track is a fast and not real technical. The rest of the track can be had just by releasing the throttle some.
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Old 04-20-2008, 02:35 PM   #6079
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with the 10:1 ratio the GTB would thermal in 3min. At the almost 12:1 ratio the GTB is 170 at 3min/ 130 motor.

Would the wiring cause the excess heat? I have 14ga wires installed since I was only running 10.5/13.5 motors.

I will look into creating space around the ESC for more airflow. Maybe novak could have Zalman make some coolers for the GTB. The blue heatsink is for the northbridge processors and have about the same footprint as a GTB heatsink. I would perfer the gold heatsink desing with a fan.


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Old 04-21-2008, 04:54 PM   #6080
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Hey Steve, just got a used GTB system and set my transmitter. I don't yet have a BL motor. My question is what does it mean when every time i power the esc off, and when i switch it back on, the red LED is on and the yellow is flashing? is it because I don't have a motor solder in place? any input will be appreciated, thanks.
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Old 04-21-2008, 05:14 PM   #6081
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Was this pretty much the first time you ran this motor or had it been run before?

Just to be sure you're runningthe fan on the ESC as well, right?

Quote:
Originally Posted by trailranger View Post
with the 10:1 ratio the GTB would thermal in 3min. At the almost 12:1 ratio the GTB is 170 at 3min/ 130 motor.

Would the wiring cause the excess heat? I have 14ga wires installed since I was only running 10.5/13.5 motors.

I will look into creating space around the ESC for more airflow. Maybe novak could have Zalman make some coolers for the GTB. The blue heatsink is for the northbridge processors and have about the same footprint as a GTB heatsink. I would perfer the gold heatsink desing with a fan.


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Old 04-21-2008, 05:14 PM   #6082
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It means that you don't have a motor sensor harness plugged into the ESC!

Quote:
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Hey Steve, just got a used GTB system and set my transmitter. I don't yet have a BL motor. My question is what does it mean when every time i power the esc off, and when i switch it back on, the red LED is on and the yellow is flashing? is it because I don't have a motor solder in place? any input will be appreciated, thanks.
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Old 04-21-2008, 06:16 PM   #6083
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The fan appears in working condition, but I went ahead and ordered a new fan if my current fan is not pushing volume of air needed.The new fan should be on the GTB by race day. I may end up turning my ESC 90 degrees to allow for better airflow around the heatsink. The RX that I have mounted vertically will be moved to top of the servo. The Xray's T2 just have little real estate for mounting all-that-jazz.

I think a porcupine style heatsink may fare better than just straight fins. Also it would reduce the weight just a smidge. Mounting the ESC close to other electronics would not affect the airflow as much if one side was block by a tall object such as my vertically RX.

I guess the devil is in the details.
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Old 04-21-2008, 06:53 PM   #6084
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Thanks Steve!!
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Old 04-21-2008, 08:46 PM   #6085
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Hey Steve,

How come ESC's get so hot even though the on resistance of the mosfets are in the milliohms? I think I read something a long time ago that its because the fets are spending too much time in the triode region (is that the right word?) and aren't being switched fast enough. I'm not sure though. Don't hold back on the technical explanation.

-Jon
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Old 04-21-2008, 08:59 PM   #6086
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Steve- There is practice the day before the warm up race. I think I'm gonna be sick that day so I'll see ya there if you're allowed to leave the farm.....LOL
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Old 04-21-2008, 09:06 PM   #6087
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Hey Steve,
I ran a 17.5 w/4cell SS GTB in my 12th scale all this winter and am puzzled by something. At the beginning of the winter I was truing my tires way down to reduce rotating mass, but I couldn't get the gearing right with the pins I had so in final desperation I ran the biggest pin smallest spur and full height tires. This finally made the car go fast. Once I had found that magic rollout I figured I'd get back down to smaller tires again. What I found was with an identical rollout, the car was faster and came out of the corners harder with full height tires. This has stumped me and I'm really at a loss to explain it. It feels like I'm looking at some kind or perpetual motion machine or something. Can you 'splain it to me please
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Old 04-21-2008, 09:09 PM   #6088
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Any guess on who makes this motor? I don't think it's a Feigao. It might be the most blatant Novak copy yet.

http://cgi.ebay.com/Team-SPEED-Tamiy...742.m153.l1262
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Old 04-21-2008, 10:00 PM   #6089
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Steve
Im just starting to race 27t stock class with my xray t1fk04 and what would be a good ratio as a starting point? im running 6.09 as my final gear ratio with a 93 spur to a 27 pinion. The track is short and tight with one main straight
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Old 04-21-2008, 10:07 PM   #6090
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Yeah, we are definately looking into other heat-sink options for future ESCs/updates and whatnot.

Anything you can do to improve airflow through the heatsink is good.

Quote:
Originally Posted by trailranger View Post
The fan appears in working condition, but I went ahead and ordered a new fan if my current fan is not pushing volume of air needed.The new fan should be on the GTB by race day. I may end up turning my ESC 90 degrees to allow for better airflow around the heatsink. The RX that I have mounted vertically will be moved to top of the servo. The Xray's T2 just have little real estate for mounting all-that-jazz.

I think a porcupine style heatsink may fare better than just straight fins. Also it would reduce the weight just a smidge. Mounting the ESC close to other electronics would not affect the airflow as much if one side was block by a tall object such as my vertically RX.

I guess the devil is in the details.
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