985MG issues

[Cupooterluvr]

I just got a brand new 985MG from Hitec after I sent my old one in because it was twitching so badly. This new one does the same thing, if a little bit less dramatically. I'm starting to think that it either doesn't have enough torque or my RX is messed up.

It's on T/B duty on my 5b, and it has 175oz of torque at 6v. Is this enough? I have done the fuel tubing mod on the brakes. It only twitches and falters when the brakes are applied.

 

[olds97_lss]

Maybe try a different receiver. I run them on my savage and aftershock as t/b servos and they don't twitch at all.

They would twitch when I ran the OFNA micro failsafe. Every time the light blinked, they would twitch. Since I went with spektrum (built in fail safe) I ditched the FS's and no more twitching.

Then again, could be what you think, may not be enough torque for that application. Although, the stock servo (SF-4) only has 90oz...

Maybe check your servo leads to see if the pin is corroded on the receiver or battery. A bad connection wouldn't let necessary current to flow.

 

[Cupooterluvr]

I noticed that my TC4 goes slower backwards than forwards, which could be similar to this.

I don't have another 3 channel to test it out on, else I'd use that until I got a new RX. I'll give it a shot on my JR FM system tomorrow.


Thanks Olds.

 

[olds97_lss]

You need 3 channels for a baja? 3rd channel a kill switch or something?

Just had a thought, does the receiver your using have a BEC? I think some of those limit incoming current and voltage.

Or, maybe try plugging the servo into a different channel just to try it on the bench. Since you have another system altogether... shouldn't be too tough to just wire up that servo and a battery pack to test out the brake strength.

 

[Cupooterluvr]

3rd channel is for a kill switch. One position is engine run, the other position closes a circuit so the spark doesn't fire the engine. There's no BEC.

 

[Mr_Byte]

Does it twitch all the time, or just when the engine runs?

I had an airboat I built with a WeedEater engine, and the servos went nuts when the engine was running. Actually, they were replacement servos, I blew all 3 of the original ones in a freak accident. The new ones twitched like crazy when the engine was running.

A resistor plug fixed the problem.

 

[Cupooterluvr]

It's all the time.

 

[Mr_Byte]

http://www.pololu.com/catalog/product/1211 might help you.

It's a switch that you can use in place of a servo and kill-switch linkage.

Or, what I've played with is tearing down a servo, and putting a relay in in place of the motor, using a diode to make the relay activate in only one "direction", so it's either on or off.

You can adjust it with the potentiometer that's in the servo. My prototype tends to buzz if I don't get it just right. The relay switches the load I'm controlling. In this case, it was to make an on-board glow-driver...still working out the bugs, but I'm thinking I'll use a mini-servo board and a small relay.