Strange servo behavior

[Egnix]

I recently put a Hitec 645 on my MRC along with an aluminum servo horn and I have it powered off of a CC BEC (using the default 5.1V output).

Every once in a while, I'll notice that my wheels now are turned (to the left) when they should be straight. I don't know if they are "drifting" to the left, or if there is a jump at one point in time. (No, steering trim wasn't changed)

From just looking at it, it has the appearance like maybe the servo horn slipped a tooth. But with a brand new servo and (aluminum) servo horn (that still look new and not stripped), I find that hard to believe.

Is it possible there's a problem that the BEC is only providing 5.1V instead of 6V?

Any thoughts?

[cartronicshn]

Originally Posted by Egnix

I recently put a Hitec 645 on my MRC along with an aluminum servo horn and I have it powered off of a CC BEC (using the default 5.1V output)......


Is it possible there's a problem that the BEC is only providing 5.1V instead of 6V?

Any thoughts?

Don't quite follow, if you have it set at 5.1v that's the voltage your servo should be looking at at, unless you program the bec for more voltage.

[Egnix]

Originally Posted by cartronicshn

Don't quite follow, if you have it set at 5.1v that's the voltage your servo should be looking at at, unless you program the bec for more voltage.

Right. That's what I said.
Some people have said you should provide 6V to the 645. I wouldn't expect 5.1V to cause a problem, but I thought it would be worth asking.

[Espeefan]

Any servo should run just fine on 4.8 to 6 volts. All I can guess is, like you, the servo horn is slipping on the output shaft, but if it's a HiTec arm, and it came with the servo, then it should fit perfectly. How tight does the horn slide onto the output shaft? It should be so tight, it's almost impossible to remove from the servo without needing to pry the thing off. I've had this exact problem you describe one time too. It was an improper servo horn, that fit snug enough to fool me into thinking it was the correct one, when it wasn't. Maybe try running a different horn, like one of the plastic ones that are included in the box and see if you still have the same problem.

Also, when you notice the wheels have drifted off center, and you turn the steering the opposite way, do the wheels still end up back in the old, turned position, or do they center up again? It's rare, I am sure, but I guess it could be a bad potenimeter inside the servo.

[Egnix]

The servo horn didn't come with the servo. But it's the aluminum Hitec horn that Hitec's webpage lists as fitting the 645 (don't have the horn part number handy). The horn fits snugly (takes some wiggling to take off).

After turning in any direction the weeks return to the off-center position.

So far, it's always off-center with the wheels pointing to the left.

[Espeefan]

If you have a programmable radio, have you tired re-centering the servo's neutral position with a sub-trim menu? Also, have you reversed the steering channel at all? If you have some sub-trim dialed into a servo, then realize the channel needs to be reversed, you then need to re-do the sub-trim adjustments because they will trimmed the wrong direction. I'm just throwing out the posibility that maybe something got changed in your radio, especially if the servo continues to be off center at neutral. I'm not really sure how much experience you have with crawlers and radios at this point, so if this obvious to you already, just know I am bouncing ideas off you and don't mean to insult anyone.

[cartronicshn]

Also what rig? is it heavy? does it return to center if you have that end lifted up on the air?

[Egnix]

Originally Posted by cartronicshn

Also what rig? is it heavy? does it return to center if you have that end lifted up on the air?

Losi Mini Rock Crawler.
No, it does not return to center when lifting it up.

[cartronicshn]

so we can assume that servo horn is ahead one tooth or two from center?

[wbillylee03]

Could you re-center the servo and then put a mark on the shaft and horn to see if it is slipping?

[Egnix]

Thanks for all the comments.
It's looking like the used dx3 I picked up off ebay. Re-bound to my stock Losi radio and had 0 problems.
hrrmmm