Rs540s Getting Darn Hottt!

[Anand]

Hello all,

I am using a stock RS540s motor in my Boomerang Re- release, initially I used the 13T pinion which was getting my motor very very hot. Less than "1/2 a second with finger on the motor hot!"

Now I have changed the pinion to the 15t, but while the top speed has increased a bit, low end torque is poor, but the motor continues to get as hot. I am running an Ansmann 7.2V, 4500mAh battery of the standard Tamiya TEU-101Bk ESC. Run times are like 20 to 25 minutes with "front yard bashing". Is this heat normal or am I doing something wrong? Also there is excessive vibration in the front arms which I attribute to poor dogbone-cup axel design, is it possible there is too much load on the motor due to friction?

Anand

[Jonny555]

First thing is make sure the drive train is nice and smooth with no tightness anywhere. Make sure the pinion isn't too tight against the spur gear.

If all that is in order you will need to lower the gearing. By replacing the 13t pinion with a 15t you have upped the gearing which will put more pressure on the motor and cause it to get hot. Try going back to the 13t pinion but fit a larger spur gear. If you can't then fit a smaller pinion.

Be sure that the motor has got good air flow around it. Air flow is very important. The cooler the motor the more power it will generate because the energy isn't being converted to heat.

[TA-Mark]

Do you have bearings fitted? Plastic/brass bushings are for shelf models that don't run.

[Anand]

Hello Jonny555 & TA-Mark,

the drivetrain is smooth so long as the front arms don't hang down to their lowest point, if they hang down to their fullest extent, then their is a lot of vibration. I can see that the up down motion is due to the inadequate angle of the axles with the dogbones.

The pinion sits with just enough pressure as this is regulated by metal spacers (flat bars) and I am following the manual.

I will do what you say as far as going back to the smaller pinion, and will order even smaller ones soon.

The car is equipped with bearings throughout except on the outside of each wheel.

Thanks a lot for your inputs and advise!

Anand

[TA-Mark]

Hello Jonny555 & TA-Mark,

the drivetrain is smooth so long as the front arms don't hang down to their lowest point, if they hang down to their fullest extent, then their is a lot of vibration. I can see that the up down motion is due to the inadequate angle of the axles with the dogbones.

Adding a rubber o-ring inside the damper, under the piston, on the damper shaft will reduce the drop of the front suspension and prevent the dogbones from binding in the drivecups. Another option is to fit shorter eyes to the bottom of the dampers if possible. Continuing to run with the dogbones binding may cause damage to the dogbone or break the side off a drivecup.

If the dogbones move in/out too far, try fitting a rubber o-ring inside one of the drivecups to reduce the amount of end play. If the dogbone is not parallel to the upper and lower arms, be aware that the dogbone will move in and out of the drivecup as the suspension moves through it's full travel. Packing the dogbone too tightly will cause them to become very tight if they do move in and out as the suspension compresses.

[Anand]

Thanks for the reply,

For now I am limiting the downward travel of arms by putting a spacer (foam tape) on the area that limits the upper arm from going down. Also I am experimenting with removing the front dog bones altogether, as well as the transmission drive shaft that leads to the front gear box, thereby converting it to a Rear wheel drive only! lets see if that throws up anything! The rear suspension has vibration too but not as much as the front. I will post my observations tomorrow,

Thanks,

Anand

[WillyChang]

is there any glitching from your AM or FM radio?

not unknown for 540s to come with internal shorts, had one in a TL01 where 1 pole was shorted

and although it ran ok on testing - it drew heaps more current and comm sparked like an arc welder.

Motor got so hot it unsoldered its wires whilst gently running on flat ground.

All that sparking also glitched the radiogear more than usual.

Try another known-good 540 and see how it goes.

[Anand]

No glitching from the radio, I am using a Futaba 4VWD, using only a 2 channel Futaba receiver. By the way I changed the car to rear wheel drive only, and the heat problems went away, but the rear wheels had very poor grip and the car was basically skidding all over the place....too much wheel spin if you ask me. Obviously a car balanced for 4 wheel drive is not going to do too well with rear wheel drive. Anyway that narrows down things a little and focuses on the cr@ppy dogbone axel arrangement. next order of things some decent universal joints!

Thanks for your advice,

Anand

[stu22]

Find an IR temp gun and get an accurate measurement of the temp. 150-160F is a normal temp and really doesn't "feel" that different from 200F using the finger test.

With what you're running, unless you have a different problem, it should be fine.