Way too much heat!

[baw888]

I'd say your 14 g wire is too thin,12g is more like it. Your cap gets over worked if the wires are losing to many volts.

[Si Coe]

Now that is an interesting subject.

Its fitted with Novak 14G wire, which is odd for an LRP, so I'm guessing its been rewired at some time in the past - unless they come with no wires at all. I thought it was thinner than I expected, but then the link wire between the two halves of my saddle lipo is made of the same wire (sans the Novak logo) so upgrading the esc wire isn't going to help.

I recharged the pack used for testing and in about 30 seconds on the ground running and a minute workbench revving its taken out 1700mah! That suggests that the wire itself isn't faulty its just receiving an insanely high current. The motor stays cool, so that energy must be being dumped somewhere, presumably in the esc. Typically the only reason for such a high current is a short, which means I'm surprised it ran at all.

[blue_pinky]

I've always thought bullet connectors are better in 1/10th cars, as I understand it they have a higher current limit than deans...no plastic to melt...and a more solid solder joint that takes more heat to desolder itself if something electrical fails!

[blue_pinky]

Originally Posted by Si Coe

Now that is an interesting subject.

Its fitted with Novak 14G wire, which is odd for an LRP, so I'm guessing its been rewired at some time in the past - unless they come with no wires at all. I thought it was thinner than I expected, but then the link wire between the two halves of my saddle lipo is made of the same wire (sans the Novak logo) so upgrading the esc wire isn't going to help.

I recharged the pack used for testing and in about 30 seconds on the ground running and a minute workbench revving its taken out 1700mah! That suggests that the wire itself isn't faulty its just receiving an insanely high current. The motor stays cool, so that energy must be being dumped somewhere, presumably in the esc. Typically the only reason for such a high current is a short, which means I'm surprised it ran at all.

Hmmm, I agree, wire gauge is not playing a part in your problems...something else is definately at fault. In fact none of your components sound like they're being used beyond spec, so shouldn't be creating that much energy if they are all working correctly!

If it's not any of the soldered joints, then it sounds like something is broken

[Rocking Donkey]

Be very careful with such a hot motor revving it without its wheels on the ground. Check this out;

http://www.teamnovak.com/tech_info/f...g_warning.html

It is worth taking the motor apart quickly to make sure everything looks as it should.

Also with so much current current flowing though your system it really is worth using the shortest, thickest, best quality wires you can.

My understanding it that buggies draw much more current than touring cars. The highest current draw is under acceleration. The added weight of buggies and less flowing tracks cause a lot of stress for the electronics, where touring car racers tend to run at a more consistent pace. Also for Mod touring cars they only have 5 cells, and 6.5T Lipo

[Fabs]

Originally Posted by Rocking Donkey

My understanding it that buggies draw much more current than touring cars. The highest current draw is under acceleration. The added weight of buggies and less flowing tracks cause a lot of stress for the electronics, where touring car racers tend to run at a more consistent pace. Also for Mod touring cars they only have 5 cells, and 6.5T Lipo

That's where you're wrong, 5-cell mod is about the hardest thing on the electronics there is. Lower voltage means hotter motors and more amp draw. I barely use half of the capacity of my cells in my 4WD using a 5.5, and they're pretty knackered, whilst with TC to be able to last I'd need new cells every 2/3 national. Been there, done that.

Anyway this sounds to me like a shortcut issue, either at ESC level or at Motor level. Could be that when the wires were changed some solder inside the ESC went a little bit astray and is causing sparks.

[djmcnz]

I think talk of TC v's off-road is a red hearing... the test times Si Coe is using are so short that the weight/wheels etc aren't the problem. Yes, if he was getting 10 mins off a pack then one could look at that, 30 seconds… no. All said and done a 4WD buggy is happy to run for hours on a 3.5 brushless with the correct speedo.

Your saddle connector is near 50C (too hot!)... what about the pack to ESC and ESC to motor wires, were you able to get temp readings from those? The hottest wire will (typically) point you to the highest resistance ergo, the start of your problem.

If your ESC to motor wires are not hot then the problem exists in the ESC or on the powered (battery) side of the ESC... wires, connectors, batteries, ESC etc, etc.

Do you have a 540 silver can motor to try? Might be worth buying one for nothing to eliminate the motor before sending anything in for investigation.

Check the 4mm pack connectors as they're notorious for increasing resistance over time as noted above.

All your deans, 4mm's and wire gauges are adequate for the current you're running. 12g is preferred for the currents you're running but 14g is more than adequate.

Got a volt meter? Check the current across the system with that, when it drops significantly you've identified where you're losing it...

My bet, unless it's the packs/pack connectors then it's internal to the ESC... disconnect motor, measure current on motor output from ESC under throttle (no punch) and if it's SFA you have a winner (loser!).

Good luck!

[Si Coe]

Well I'm waiting on the utterly brilliant Jamie at SMD to send me a new capacitor before trying again.
I'd not considered the 540 idea, I have like 100 of them in my lab at work. I knew I couldn't test it with one of my sensorless brushless motors, but forgot the Sphere does brushed too.

Battery - esc wires didn't get temp reading before cap blew, but were very hot, esc-motor wires merely warm.

Jamie reckons the problem is in the motor, but within the endbell which is why the can is still cool. When I get the cap I'll investigate further.

[Si Coe]

Sorted - Well I think. Opened the motor endbell to find a blob of solder shorting the B and C wires together. Because this was in the endbell not the winds the motor wasn't getting hot but everything else was. I bodged a capacitor from an Ezrun (wrong rating but its what I had) and gave it a test. 4 minutes running before the insane speed caused me to break a wishbone, and everything is at acceptable (if on the warm side, but its a hot day) temps. Battery recharged to have used 2200mah in that time - much more like it.

Not sure the cap will hold as its not the right one but the car now works.

Thanks all, especially SMD for great service/advice, boo sucks to Modelsport for taking far too long to send my new transmitter.....