JITTERY CAR

[extrememacko]

Hello, Im new to the modern electrics but I have mixed old with new;

I am running 27 turn brushed stock motors with nosram dominator evolution esc and modern 2s lipo in a buggy. My buggy works fine on the bench but as soon as i try to drive it away it just jitters about and doesnt respond properly to signals.

I have 3 escs, 2 radio sets, 2 lipos and 3 stock motors, I have tried all combinations of these to see which part is faulty but it makes no difference!

Is there some incompatability with lipos and old style brushed escs?

The only combination that works is when i try a Keyence speedo but even then when the car goes further than 20 metres it sometimes disobeys the tx. The nosram and lrp qc3 are jitterers and cause the motors to get very hot and start smoking almost straight away!

Please help!

[Danny Harrison]

I believe there is specific esc setting for brushed and brushless motors. I'd try that first.

[johnnygibbon]

1. embrace the modern age of rc
2. throw the brushed motors in the bin
3. buy a brushless motor
4. buy 2.4ghz radio gear
5. rejoice in the reliabillity and general happiness of modern day electrics

hope this helped , it did for me

[extrememacko]

thanks, throw in the bin eh, mmm ill think about that.

Settings found on the keyence, no mention on the others manuals.

Would be interesting to know why they need a special setting, Whats the difference between dc power from a nimh and dc power from a lipo?

[Cardnim]

Originally Posted by extrememacko

Would be interesting to know why they need a special setting, Whats the difference between dc power from a nimh and dc power from a lipo?

I dont believe there is any difference in the batteries, but if you are running a brushed motor from brushless esc then thats the problem.

Brushed motors send current into the brushes, then into the commutator which causes a magnetic field, and this is then pushed round by the permanent magnets in the can of the motor.

A brushless motor is completely different.
The current from the battery (via esc) goes to three different electromagnets which have to be fired in an exact sequence in order to create the rotation. (A,B,C)

It is this sequence which is causing your jittery-ness I believe.

Your esc thinks it is needing to pulse the current to different parts of your motor because it thinks it is driving a brushless motor... when actually, it should just be sending a constant variable current to control the rotational speed of a brushed motor.

Just a guess, but hope it helps.

[extrememacko]

Thats interesting but my issue is the opositte, I am running a brushed motor with a brushed speed controller.

[john333]

Sure you're not putting too many volts through it? if you're on lipo they are 8.4v fully charged

[sosidge]

Ignore what people have been "advising" above - there is no reason why a car with brushed electrics and an AM or FM radio can't have it's interference issues solved - the old technology was fine for 30+ years of RC racing...

It's surprising that all of your interchanged gear should offer problems - it could be that multiple components are faulty, it could be that your installation is untidy, or it could be that you are in an environment with a lot of electrical interference (housing and power lines).

The basics are...

- Good condition gear
- Charged batteries
- Don't coil wires and make sure the antenna is the correct length and running out of a long tube (not bundled under the shell)
- Make sure the motors have capacitors fitted

[bodgit]

Do you have capacitors fitted to all your motors.

[extrememacko]

All motors have those little yellow capacitors fitted, perhaps the escs are all just broken! but it is strange, when I put the same stuff in my b4 then that goes ok within 20 metres only though! Its weird

[extrememacko]

But it is a bit of a cooincidence that the only one that works, the Keyence speedo, is the only one with a special setting for lipos, the others dont, what is this special setting why would it need one?

As for the voltage too high comment, so if I try and charge just 1 cell then in theory it should be ok?

[bodgit]

Have all the motors had their coms skimmed and are the brushes free moving and decent length.

[Danny Harrison]

Originally Posted by extrememacko

But it is a bit of a cooincidence that the only one that works, the Keyence speedo, is the only one with a special setting for lipos, the others dont, what is this special setting why would it need one?

As for the voltage too high comment, so if I try and charge just 1 cell then in theory it should be ok?

Lipo batteries need a low voltage protecter so they dont drop below 3v a cell

[extrememacko]

ok so that trick wouldnt work unless i used a dedicated 1s cell (I guess)
Yep, motors are all ok in terms of brush length etc, also dont forget, on the bench, no issues with jittering, motor accelarates and stops as normal, its when i put it on the ground that the jittering begins if i just try and drive.
steering goes mad too

[Tobamory]

prob not like mine but, my K1 jittered and I needed to fit a capacitor to the receiver, because the Savox servo was drawing too much power. only happened far side of track never when I was sat on it

If I swapped out the servo for a lower specktrum model it went away.

Have you tried a diff servo, because if that draws too much power as the car travels away it starts to jitter. its what mine was.

these solve it

http://www.rccarshop.co.uk/index.php...protector.html

[Big paul]

Hi mate when brushless came out I used a lrp brushless esc with a 27 tern motor and lipo batt,no problem at all they were designed to do this. Have you soldered two wires out of the three on the speedo together.I'll try and find my instrutions to see exactlly how to do it.