Help.. BL setup issues (fried ESC)
 

What the heck is wrong with my BL setup??? I recently converted a Tmaxx over to electric and have a whopping 4 runs with it so far and believe I just fried my ESC... :cry:

I run a 7XL with MM on 4S. I’ve been having issues with the 7XL running super hot and captured temps as high as 220F before shutting it down. I thought I was undergeard a bit (51/20) as the MM was only running around 100F and batt just a few degrees above ambient.

So I just received some additional spurs and changed over to (46/20). It seems I went too far in the wrong direction as the MM thermaled twice both times around 175F and the 7XL still runs in the 200F range. It’s been cogging pretty badly on initial throttle now too.

This last run ended with me standing over the truck, body off, taking temps and investigating the cogging...when...the ESC “sparked” and released a small puff of magic smoke. It was literally 1~2 seconds before I got the batt disconnected since I was right-there, and definitely wasn’t a major melt-down. Also one of the 3-motor wires pulled from the board. This may have been the “spark” and smoke, but not sure until I attempt to solder back on and see if it works. But it was hot, at least enough for a wire to un-solder and pull out...

So what gives! I’m pretty disappointed with my setup. It’s got crazy power but so far I’ve yet to get a full run in without overheating the motor, and now ESC. :grrrrrr:

A 7XL can run pretty hot - I found gearing a 9XL to be better - If it got hot enough to melt the solder on a motor lead I suspect dead. At a minimum I suspect you have blown some fets

No harm in trying to put it together but suspect you will be sending it to CC with $50...

I've toasted 2 MM on 1/8... 1 motor magnet cracked and one cogging combustion but with both of these I just ended up with a pile of carbon

sorry to hear about your problems. It seems like you went overboard on the gearing. Like you said... you went in the wrong direction.

You should have tried a smaller pinion with the first set up. A 18T would've been my next choice. Going with the 46/20, you just increased the amount of AMPs going through your electronics.

I was geared higher than you, running 7Xl, 4S.. on fastlane E-maxx about 15Lbs... and 51/24 gearing.. mine was fine..... was your drivetrain rolling freely..

Wait a minute! What? Do I have the equation backwards? Isn’t a HOT motor, with cool ESC and batt an indication of being under-geared (too much bottom end)? While a cool motor with hot ESC and Batt is an indication of being over-geared (to much top end)?

Dropping teeth on the pinion would have been even lower gearing then the original 51/20.

I did just rebuild my tranny using the revo slipper mod. It felt free rolling, at least as much as a newly lubricated tranny would (a little tight until the lube warms and fly's off the gears). :neutral:

Note I also run UE 1/8 diffs, so comparing gearing might not be an exact comparison. Here's my ratio with these two gear combinations:

Original 51/20 gearing (very hot motor, warm esc, cool batt)
Spur/Pinion Ratio: 2.55 : 1
Total Ratio: 14.52628 : 1
Adjusted Speed: 39 mph

Adjusted 46/20 gearing (hot motor, very hot esc, warm batt)
Spur/Pinion Ratio: 2.3 : 1
Total Ratio: 13.10214 : 1
Adjusted Speed: 43 mph

IMO, running 51/20 is over geared with UE Diffs. You should be at 16 or 17 pinion with mod 1. You will find your sytem much much happier. The temps calculations is an estimate only, and not ALWAYS the case. Another problem could be a connection somewhere as well. Also, you are running a ubec correct?

Dropping some tooth on the pinion would make you pull less amp, but with most Feigaos you would still see the motor run hot. Aqwut had it geared really high, but the motor was probably not reaching really high RMPs. One example would be my BPP truck. I ran it today with 5S, 65/17 and 4.3 truggy diffs everything was barely warmer then ambient. Pulled 72A max. I ran a few days ago, same 6/17, but with the 3.30 buggy diffs and pulled 75A max. You will see a lot of people complain about heat issues with Feigaos and some have good luck with them.

Yes, I have heat modifications to help the MM run with a 25C 5000mah 4S pack including a Novak cap, fan on the heatsink, and CC-BEC with red wire pulled from the esc plug and fan wired off BEC.

With my config the motor rpm is just above 35k. Not sure if that’s related but may be close to the ceiling for a Fieago?

Ok. Then I would try the 16T, or even the 17T. Also make sure your connections are ok. Your RPM are right where they should be. I don't even run a cap with my MM on 5s. I do however have a fan on it. :) The only diference between what I run and what you run is the motor. I ran the 10xl on 5s, which now I ahve the 9xl which i have not run. But I run 16T/51T, and everything is happy.

sorry corrected below


Edit: I looked at your link, the others are right. I assumed you were running the stock Tmaxx tranny, 20/51 is too much for the 7xlI ran mine with a 16 tooth pinion. From what i could see, the reason you didn't see temps over 100 was the fan cooled it before the temp checker was used

Thanks all for the comments… So it appears the consensus is that I need to gear down, specifically the pinion. That said and according to BrianG’s calc, a 51/16 combo with my setup results in a whopping 32mph. That’s pretty pathetic for a brushless lipo setup no? Don’t get me wrong, I agree a 7xl is not a suitable motor for my setup, never was intended to be permanent, just testing BL (remember I’m a nitro convert). Dropping all the way down to a 16t pinion will allow me to do instant back-flips, but at the cost of being beaten by a stock E-maxx at top speed. To be honest, I thought the 51/20 was too low geared for my taste :neutral:

yes.. 32MPH is pretty pathetic.. but I honestly don't think it's the gearing.. my ACNC maxx is 15Lbs, UE diffs, UE tranny, all fastlane/ACNCM... I used it for racing last year @ my local track. I used gearing for about 45MPH.. and had no problems... maybe there was a short somewhere, loose battery connections, wires too thin, loose motor connection? I know if one of the motor connections comes off, the esc could easily fry.. It happened to me on my airplane after I crashed.. all I did to my Mamba, was disable the BEC and had a fan on it... I didn't even have a fan on the motor.. I used the 7XL heatsink version..

Also, I upgraded all the wires to 12 AWG & 10AWG...

Thanks aqwut!

Good news, turns out the ESC isn’t totally fried! I re-soldered the motor lead that came off, powered it up, it engaged and operated normally on the work-bench at least. Still may be some damage from the excessive heat it was subjected to. How can I tell if it’s got some burned up fets?

I’m thinking something must be wrong with my drivetrain. I keep swapping around my tire/wheel combinations and did put a new (previously unused) set on before this issue. Looking back the rig was pulling slightly to one side which I didn’t think was too unusual at the time. I had to counter with additional steering servo trim yet I hadn’t touched the steering linkages with my recent tranny rebuild and gear changing. Now I’m thinking one of hubs or wheels was dragging for some reason, possibly causing the pulling to one side and elevated load on the electronics.

I run the UE 6mm CVD shafts and don’t like the hub/hex setup. It secures to the axle using set-screws (instead of hub-pins) and it seems this special hex can slide all the way firm against the bearing/hub-carrier. So when you crank down your wheel nuts, the wheel seems to be pushing against the hex, and the hex seems to slide down the axle shaft and tight against the bearing/hub-carrier. Not sure what’s up with that….