Metal gear servo play

[WTF]

Anyone know how much play is ok with metal gear servos? I am using some Hitec 5945 that have alot of freeplay but still seem to work ok.

[Vic3D]

I have the same issue with the slot on my elevator servos (5945) and its pissing me off.

[adrian]

all metal servos devolope play or slop - this is due to hard work - fact - only the new titanuim gears seem to last longer - this is for all brands of servo

[adrian]

i renew gears atleast once a year

[exeter_acres]

the 5945's are the worst of mine too... my 5955's are holding perfectly (titanium) but the 5945's are all a bit sloppy....

[KrisW]

Every brand of aluminum/bronze/steel metal geartrains will develop slop in them, though some will develop slop slower than other makes or designs. The 5945 HiTecs are good for about 125-150 flights usually (from my own experience) before they develop enough slop to make centering a problem. JR 8411 and 8611 servos seem to get sloppy long before their HiTec counterparts. . sometimes in as few as 20-25 flights.

With a sloppy geartrain, on center, it's possible to get some more life out of the gears by reducing the slop on center. This is the main area where people complain, because the gears get about 90% of their wear inside the first 5-10 degrees of movement. By merely taking the top off the servo,, then rotating all the drive gears (not the output gear) by 180 degrees, you will take the most worn areas of those gears out of the equation, and re-establish tigher tolerances on center. This is because you are putting areas of gear teeth with less wear on them, against other gear teeth with less wear on them, which results in a tighter feel on center. ON CENTER is the only place that you will see the gain, however, but since the gears are loading up against a force (like air movement on the control surface) as they rotate, and zeroing out any lash. . AND because not all the worn areas will be hitting eachother all at the same time anymore, you will not have a noticeable degradation in movement accuracy throughout the movement range off center. This little trick should get you an additional 75-100 flights, or so, out of a set of gears before it's time to change them.

How much slop is too much?? If you can take the output arm, with the servo energized, and move it back and forth 1/32", then this is excessive movement. 1/16" is getting REALLY sloppy, and needs to be addressed quickly. With a digital servo, the arm should be "locked" in place, under light loads, so what you will be seeing if it moves at all is the slop worn into the gear train. That 1/32-1/16" is on a 1" long arm. Another test is to de-energize the servo, and just wiggle the arm back and forth. If the arm "clicks" or has a noticeable dead spot that you can wiggle on, then you are getting slop that should be addressed. It's up to you what you do about it.

Somethig else to be said here . . . 6 years ago we had only ANALOG servos. . they were very easy to move off center before they would energize and try to hold position. Even a worn 5945, on center, is TONS better than any analog servo out there. It's all a matter of perspective on how tight you want things to be.

Gearsets for the 5945 HiTecs are the same as for the 945 analog servos, and cost about $20/set. If you are going to swap in a new set of gears, be sure to get the moly-based gear lubrication grease from HiTec, or use a heavy-moly based synthetic grease available form Auto parts stores. White Lithium is NOT an advised lubricant. . nor is graphite powder or non synthetic grease.

[bob_nj]

Hey Kris,

What happens if you do rotate the output gear?
"By merely taking the top off the servo,, then rotating all the drive gears (not the output gear) by 180 degrees"

In other words, can you file down the stop and rotate the output gear?
What does the stop actually do?

Thanks_bob

[Shawn Berkheimer]

	Quote: Originally Posted by bob_nj
	Hey Kris, What happens if you do rotate the output gear? "By merely taking the top off the servo,, then rotating all the drive gears (not the output gear) by 180 degrees" In other words, can you file down the stop and rotate the output gear? What does the stop actually do? Thanks_bob

You can do this but the output gear must be rotated 180 degrees to properly engage the pot. the downside is that the servo no longer has a mechanical stop and if someone picks it up and rotates it all the way over it can kill the pot.


shawn

[bob_nj]

Can you elaborate on this a little?
Any pictures or diagrams?

I'm going in the shop right now to try to sort this out?

Thanks_bob

[BR289]

Also check to see how hard the servo has to work to "center" itself. Binding in the linkages will cause the servo to overwork itself and burn out. Sometimes its hard to "See" the binding.

[aerowiz]

guys, $20 for some gear sets, c'mon.

its cheaper than replacing servos and it is relatively easy to do.


aerowiz