Sticky Throttle

[MattWadzRC]

Hey guys, quick question when i accelerate after getting my car running, it sticks for a little bit and i have to break to stop the sticking, and the servo is making a jittery noise, I've adjusted the trims, and still no luck, any ideas?:\

 

[Metalhead Matt]

Check for binds in the linkage and carb slide. If nothings binding, it may be time to upgrade the servo.

 

[basketcase45]

Also could be that the batteries for the servos/ reciever are weak. recharge or get new batts., depending on your situation. Does it work properly when the engine is not running?

 

[Scrogg]

I'd def. look at the linkage. everything has to operate smoothly, and align properly. If the servo is pulling the carb all the way open to the point it can't move any further, you need to adjust the linkage and turn the rate down. a carb slide or rotary carb should never be opened to the point it reaches the carbs' mechanical stop. It will wear out the carb, and burn up the servo. Same thing with the brakes, you don't want the servo straing at idle or at full brake position. If it is engaging the servo saver a lot when you apply the brakes, you need to readjust. If there is too much tension from the throtttle linkage when the brakes are applied, it will burn up servos. I see a LOT of people running 1/8th scale truggies and buggies make this mistake. All of these conditions will eventually burn up the servo and possibly end up in a run away, even with a failsafe and throttle return spring. Revo linkages are a good example, very difficult to set up properly. Takes a lot of time and patience to do.

 

[revo_rob_1984]

I agree with checking the linkages and as far as what scrogg said about revo linkages he is 100% correct i have a revo and the linkages were a pain in the butt to adjust when i upgraded my motor, but all is well now

 

[PaulC]

I didn't know it wasn't supposed to hit the carb stop. I just adjusted mine so there was no servo hum at full throttle. Thanks The carb was slightly sticky at full throttle, until you closed the throttle fully, I assumed it would 'wear in'.

Brakes however... if the servo is not straining, what is pulling the brakes on? I mean there are just 2 plates of metal pushing on a textile disc, surely to produce braking with what is in effect a disc brake constant positive pressure must be applied. No?

On my motorbike, if I pull the level it moves until all the slack is taken up in the hydraulics and the pads are rubbing on the disc, but the bike won't slow down much. It takes me to apply pressure to the lever, which doesn't move much but takes more and more pressure which is transfered to the disc brakes and slows the bike rapidly.

So surely in RC servo terms the servo has to produce pressure after the 'pads' have met the discs and thus make a straining noise?

When I adjusted mine for no servo hum I get no (or very little) brakes.

 

[hamz9561]

The servo should not be straining when braking, but it should be applying some clamping force to the disk from the pads. The servo shouldn't be at the end of its travel when apllying the braking force.

 

[Scrogg]

Correct hamz, find the mechanical advantage in the brake setup...don't rely on the servo to do the job with brute force. A good 100+ oz of torque servo is my minimum requirements for throttle/brake servos. I can make a 40 oz. servo do the job almost as good though. I just do not trust cheap analog servos. My rigs are usually $1500 or more total investment. Radios and servos are the last place to skimp. They are the most critical parts on a r/c IMO. My last runaway was with a Revo, cheapass Traxxas servo....the new digital ones. i rushed installing it to get to the track. I did not set it up 100% properly, 15 minutes of running and it took off WOT. No damage, but it still pissed me off. Servo was one use old but over the 30 day warranty.....my fault anyways.