540C motors, always hot?
 

I run a 540C 9L motor in an MT2 and it seems that it always runs hot. After the run, the motor is really hot over 150, the esc is about 130 than the batteries are about 120.

It runs on 8 cells and 52/15 gearing at about 30-35mph. It seems like the gearing is perfect, I can hear the tires spin from rolling starts and it has enough top end to go fast.

I had the normal 9L on my 1/8th scale and it never seemed to get this hot. I ran it on the same voltage.

Does any C motor user have the same problems?

150F is fine for a motor, I wouldn't worry too much. Going by the controller and battery temps I wouldn't say its over or undergeared.

I ran it today in slightly milder weather.

After about an 8 minute run, before the pack could finish, the steering became erratic, slow and unreliable, I even had the reciever shut down for a few seconds. I was getting full power from the motor, but the steering was way slower. The ESC was 160, the motor was 180 and the batteries were 118.

What the heck causes these motors to run so hot?

I think the BEC overheated or something.

Judging by the battery vs motor temps I figure maybe it's running a higher ratio. But if I lowered it the esc would get hotter.

To be honest I think that the heavier can insulates the heat and the normal L can motors will run cooler. I don't remember the L can getting any hotter than 150 in my buggy.

A uBEC might help to keep the controller temps down a bit. But 180F for a motor is the maximum that is safe, you don't want to go any higher. Can't say I understand why everything's running so hot. How many cells are you running, and what controller?

9920, 8 cells and I do use a UBEC

I did get a temp reading from the cover of the ubec and it was 88 degrees. It was hotter than the ambient temp.

I was thinking that the ubec overheated, but it really shouldn't have.

hmmm....The problem is probably that your running on too low a voltage. At that voltage the motor won't be doing much more than 23,000-25,000rpm, and at that speed it won't be efficient at all. Low efficiency = heat. That explains the motor getting hot. Your controller is probably getting hot because your having to 'gear up' so much to get any kind of speed, and in doing so your increasing the load upon the motor and hence drawing lots of current. Lots of current = hot controller.

That would be my explanation. You need at least 10cells for that motor, ideally 12 though. Lipo or GP2000 are probably your only solutions (or stacking up the SubC's)

I run the same motor in the same vehicle with 12 IB3800 cells and an Mtroniks Truck controller. My gearing is 52/14. I always use either M2K's or DirtBonz jr. tires. The weather has been about 60~80 degrees. I don't have a temp. gage, but I'm sure my motor isn't getting near 180 degrees. It's hot, but I can hold my finger on it without getting burnt. The controller and batteries both get pretty warm, but cooler than the motor.

That settles it then. The motor is getting hot because it's too far out of its peak efficiency range.

cart213, if you can hold your finger on it for ever, its can't be much hotter than 120-140F.

Wow, this has to be the first "you aren't running enough cells" problem RC monster ever had.

Do any S can motors have a 5mm shaft? I guess I need a smaller motor.

I don't trust the tranny to anymore than 10 cells, and my custom 8 cell pack fits so perfect.

If you've got the aluminum diff cases, which I think you do, the tranny should hold up ok. I haven't had any issues yet on 12 cells, and I'm using the aluminum diff cases, too.

Btw, starluckrc used to have a feigao 540 7s with a 5mm shaft. You could ask him if he still has it. That motor should be a rocket on 8 cells.

Well what esc are you running and do you have the timing set right in it?
If it has a slipper clutch make sure it is not slipping to much either. Have you tried a lower gear ratio to see. May be fall back to a 14 52 gearing.

I want to use a lehner basic now, maybe the 3100 or the 4200 or maybe the 5300. I figure the 4200 would be good.

The pinion sits a bit far on my 540C, so does anyone know the length of the lehner basic shaft?

Can you get a Basic with a 5mm shaft?

The Basic's comes with a 3.17mm shaft (1/8") that is 16mm long. The basic 3600xl or 4200 might be good choices, and I would also look at the 380c 6l.

Do you know if the 6L has a 5mm shaft. I heard the feigao motors have weak 1/8" shafts.

No the 380 size motors only come with a 3.17mm shaft, and it isn't hardened. You best bet is with a lehner BASIC of some sort (XL would be better for your application)

i would think the xl4200 would be about right.

Well, the truck is not that heavy, I don't think the xl will be needed. I'm not looking for fastest, I'm more interested in a top speed at least 28mph and a runtime around 12-14 minutes. Maybe over 15 if I can manage.

If I gear down the 4200 basic I think I'll be satisfied.

You think I can get away with the smaller motor?

not sure. i would personally go for the xl.

4200xl is too hot for offroad, but its great to send your tc3 70mph

As a temporary solution, do you think a 13T pinion, instead of the 15T would help at all?

I was also thinking of using a 550 motor instead for longer track times, still at 9.6v.

Both of these have a 5 mm shaft

540 7s
http://cgi.ebay.com/Feigao-Brushless...QQcmdZViewItem

540 9s
http://cgi.ebay.com/Feigao-Brushless...QQcmdZViewItem

I'd go with the 9s. The 7s may draw too many amps.

Wow, thanks for those links

Keep us updated if you get one of those motors.

I bought the 9s, it'll take a while for me to get it. I also just bought a 13T pinion too. It seems like a great motor to use.

I bought a pinion form mike and it came in less than two days (being about 40 miles away doesn't hurt either). I ran it with the 13T still with the 9L and it definately ran cooler, still too hot to touch after about 4 seconds though and the runtime was aboout 9 minutes. The ESC was less than burning too. And the bettery temp was in check.

I assume the 9s will give faster speeds and longer runtimes. It's weird to think that it will. The 9L was just overall slow and innefficient.

Yeah, it's all about the rpm/V. With your 8 cells, the 9L was only running at 26,000 rpm unloaded. The 9S will do 37,000 rpm with the same number of cells, so it will be much faster.

Of course, if you crammed four more cells on there like me, you'd be hitting 39,000 rpm unloaded with the 9L and going about 50mph without overheating. :p

Less weight the better for me. I noticed that I've chipped some teeth off the front internal diff gears by braking too hard, weight it definately not what I want. The gears usually don't wear, I have 0 wear on the ring gears and the internal gears only stop working when you crack them. It not like a "over time it will wear" thing.

I've seen some hardened ring gears crack too in the RCU forum.