Way too much heat!
 

Well after the problems with my LRP Sphere / LRP X11 7.5 combo it was suggested I try another motor, so I acquired a Novak 4.5R. Now I know its a 'hot' motor, but I didn't expect what happened.
First test run (D4, stock spur, 18 pinion on tarmac) it ran for about 3 minutes, before one of the battery leads came desoldered. It had near totally drained a 4300 Lipo in that time, and the Deans connector had melted!

So thinking I'd got the gearing wildly wrong, I switched to the smallest pinion I own, a 15, soldered on a new deans plug, put a different pack in and tried again. This time I managed about 30 seconds before a wire came unsoldered. The Deans connector had melted again.

By now I'm getting concerned, so after replacing connectors (again) I tried gently revving the car on its stand. As you nail the throttle you can feel the wires getting warmer. Even off the ground, the heat is immense. However the drivetrain itself rolls nice and freely.

All the wires involved are 14awg Novak, the connectors proper Deans. The ESC gets hot, but doesn't thermal. The motor is very warm, but not scorching.

I assume something is badly wrong here, but what bit is at fault?

Black to black - Red to red

4.5 + 4wd buggy is not a good idea, it is more a TC morot.

Also, the ESC settings are probably far too wrong for that motor.

I wanted to see if the ESC was working after earlier problems, so I used what I had. In any case a 4wd buggy on tarmac with the shell off isn't really any harder on the motor than a touring car.

But you might be right about the settings being wrong - the brakes seem awful sharp.

Si

Check your battery connections = if you have 4mm plugs into the battery they can get loose and dirty and as resistance equals heat...........

MattB had a similar problem with his - new 4mm plugs and a clean out of the battery sockets (think he used nail varish remover on a cotton bud) and job sorted...

Maybe something shorting on the motor connections or even on the carbon?

no, the loading on the motor from the transmission is a lot more, bigger wheels to rotate for starters, plus a buggy weighs more too.

But, as long as the motor is ok, I would look at the settings, timing advance and throttle limiter for starters.

Check your solder joints on your speedo and check all your connectiong in my opinion sounds like a dry joint.

A

OK, well......

Set the punch, brakes etc to minimum. Manual doesn't mention timing advance.

Put the car on the stand, then temp gun in hand gentle rev the motor. After about 10-20 seconds at 1/3rd throttle, motor is at 28C, ESC is reading 41.8C and the wire joining the two halves of the saddle is at 48.2C. Then the capacitor exploded in a shower of sparks. I switched off immediately

So I'm guess that due to the fact the motor never even got warm the problem isn't there. I guess its the ESC, hence the capacitor blowing. I take it a faulty capacitor alone wouldn't cause these problems?
In which case who fixes LRPs (its second hand so no warranty) and what sort of price are we talking? This foray into sensored motors is proving expensive and fruitless so far.

Glyn Ward is the man you want to talk to about LRP repairs. Im sure someone will come along with his details.

A

sphere or sphere tc,?? sphere has a lower limit than a 4.5

The capacitor could of been at fault, email SMD for tech support.

Its a Sphere TC. Well at least thats what I was told it was - I bought it off Kopite. It doesn't have any stickers on it though so I'm only going on his word. It does have the heatsink and the fan, and certainly looks like a Sphere TC!

Is it worth replacing the capacitor and trying again. I can easily source a replacement capacitor and fit it, but I'm concerned repeated attempts to isolate the fault might just damage more things!

Contact Jamie at SMD.

I have Pm`d you Derek Baileys details - hes the man :thumbsup:

No Rich you're da man!!!:thumbsup:

Yea if kopite says its a TC its a TC he is a trust worth guy.

A

I'm sure he is trustworthy. Its just with no stickers I can't confirm or deny!

Thank you everyone.

I've emailed SMD tech support to hear their verdict, and kept Derek Baileys details to send to for repairs. I think I've sent him stuff in the past (like 10+ years ago!) and he was very good.
In fact I might send a bust servo along as well.......

Hopefully I can get it all up and running soon. For the few minutes it ran it was pretty mental fast with that motor!

Keep us all updated, dude.

small wire
 

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.

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.

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!

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 :(

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

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.

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!

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.

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.....