How hot should an ESC get?
 

At the weekend I did six laps of a race when my car cut out, then it started going again, then it cut out.

I felt the heat sink on the LRP SPX speed controller, and it was too hot to touch.

I was running a 7.5t novak brushless motor and gearing 78/22.

I noticed when it was working, it felts really slow out of the corners, but built up a decent speed on the straight.

I guessed the 22 pinion was too much, so I've dropped it down to 20, had a mess about in the house, and the ESC is still far to hot to touch, and I can't hold the back of my finger on the motor for more than 2 seconds.

Last time I ran the car it was running a 9.5t brushless motor with a 20t pinion, and it ran fine.

Is the 20t pinion still too much?

I have a little chart I found on the internet that I printed out, and it says to start off with a 23t pinion with a 7.5t motor, so I'm confused as to what I might be doing wrong.

to me thats geared way to high or your "punch settings" are wrong on your speedo

What pinion should I be using do you think?

I've checked the power profile, and it's currently set to default which is 'linear'. The options available are Smooth, Linear, Progressive, Aggressive.

Automatic brake is off (I think this can cause additional heat if you have the brake on).

Actually, I didn't realise this, but the ESC tells me how far away it was from the cut off temperature.

I counted 7 flashes, you have to minus 6, leaving 1.
For every 1 flash it's 8c.
So the ESC was 8c away from cutting out when I just tried it in the house!!

The highlighted bits in red you should be able to guess what you need to do i recomend trying a 18t pinion or a 17t

Sorry if this post sounds anal

To be honest I no idea on the internal ratio of the Lazer but it must be in the same ball park as everything else out there in which case a 22 doesn't sound too much, certainly unlikely to have it that hot in 6 laps (2 minutes?) that is assuming it's a sintered Novak, not the old original bonded ones?

Sounds like either the drive train is damaged somewhere or the motor or speedo is dodgy. If you take the pinion off, does it roll freely?

I used to run an 18tooth in mine. Was with brushed, but about the same as a decent 7.5 brushless. I assume it freewheels smoothly?

i ran mine with a 19 pinion at stotfold

i ran a 4.5 on an 18 with no issues, so 22 on a 7.5 should be fine.

either drivedrain binding to put the motor/speedo under excess strain, or you have an issue with the speedo.

I would recommend a strip down and rebuilt of the car and ensure it all rolls freely. There used to be an issue of the diff gears rubbing inside the gearbox housings, so make sure everything is free and don't overtighten anything.
Also make sure the gear mesh of the pinion and spur isn't too tight, there should always be a little movement between the teeth

Thanks for the suggestions.

The drive train feels smooth enough, and if I just let the car run for a few minutes on full throttle then the ESC doesn't even get warm. The problem just seems to be upon acceleration, if there's a lot of it, then it's heating up.

I'm expecting a new Speed Passion motor today, so I'll see what it's like with that.

Is it the SPX Super Reverse? I notice it has a 5.5 turn limit, so I don't know how much margin there is in that. Gearing depends on track size, if you're over geared for the track you could heat it up pretty quickly. Acceleration from low speed is where most heat is generated and a mid range ESC with no fan will be more vulnerable.

Obviously check the drive train spins free, other than that keep gearing down, if the temps don't drop by the time you're running out of ratios there is probably something wrong with the motor/ESC.

I've got my new speed passion motor, and it's having the same problems, like it's struggling to pull away.

One thing I did think of, I did recently replace all the screws on the car for hex screws, so to counter that I've loosened them all off a little, but there's still no difference.

I don't think the car feels like the drive train is stiff.

I've uploaded a video showing the car pulling away and how it struggles, I'm also in the process of uploading another video showing the pinion taken off the motor to show how the drive train moves freely.

http://www.youtube.com/watch?v=IrehkfpeD3k

Won't solve your problem, but running reverse won't do the motor any favours - modified motors don't like reverse (from what I'm told)

Here's the video showing it freely across the floor

http://www.youtube.com/watch?v=MziYGy0UNs8

Brushed modified motors don't like reverse. Brushless motors don't mind one bit.

On the video it looks fine. Doesn't look like anything in particular is wrong with it. Take it down your local club and have someone look over it. Try not to free-rev your car too long without load as it's not too good for the rotor.

Your wires look very long and do you have them all at very different lengths?

all the wires are the same length, but the connections on the motor are different distances away, making some look longer than others.

In the video it's running a 20t pinion as well, would that still be ok, or should I see if using a 16 makes any difference?

Yes running a 16 pinion could make a big difference, give it a try. If it makes no difference there is probably something other than gearing wrong.

Not sure why you went up on the pinion when you went from a 9.5T to a 7.5T, as that seems opposite of what one should do as standard practice.

In my opinion, just changing two teeth on the pinion is not a drastic enough of a change if the motor and esc were THAT hot. Mistake people often make is to adjust by a tooth or two, when they need to change by several teeth to make a difference.

As others suggest drop well down (16T), or until it runs cool, and adjust upwards from there. If it is still running hot, and maybe before hand, check to see if you have some other binding somewhere in the drivetrain.