Servo Geartrain Lash
09-16-2006, 09:02 AM
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Servo Geartrain Lash
What if anything are you guys doing to measure your lash?
I measure mine when new, and then as a reference to see how they are doing
when the need arises.
To start from the beginning, when I get a new servo, I burn it in on the bench for
15 minutes on the HiTech programmer in the auto mode where it sweeps back and forth.
Then I set the servo rigidly in a jig and bolt an arm on that has a 12" pointer on it.
I set the servo at 900 1500 2100 and take the lash using a ruler in millimeters.
Usually the lash is taken with power to the servo.
I say usually because I do vary the technique depending on which brand of servo is being tested.
I'm a bit stymied by some of the readings I got today while checking out and logging
a few servos I hadn't done yet. Some were spank brand new, and a some were recent repairs.
To give some reference, some had .5mm's of play and some had as much as 2.5mm's.
A couple were around 4mm.
The reference from the manufacturer was that at 4mm the gears should be replaced.
Most servos they see are between 3 and 4 normally.
Yikes!
I know we take our linkages very seriously and spend lots and lots of time to avoid
slop and get precise geometry-resolution and linearity.
It seems to me that stuff like this boogers it all up
Heck, with 3 servos that have 2mm play each at neutral, would you even need to match
them up?
Maybe I'm too anal, but even the 2 and 2.5mm that I am seeing looks like miles
at the end of that pointer. Is it because it's so long?
To further twist my mind, on a couple of the brand new servos, I was able to move the
arm easily at the extremes for about 5mm's.
This didn't seem like gears, but just felt kind of loose if that makes any sense.
Doesn't seem right to me at all, but I'm in information overload right now.
I use 8411;s, 8611's, 5945's, and 5955TG's.
This was posted on another board with no responses, so some of you may be seeing it again.
I apologize for that.
Maybe I ask dumb questions[&o]
I measure mine when new, and then as a reference to see how they are doing
when the need arises.
To start from the beginning, when I get a new servo, I burn it in on the bench for
15 minutes on the HiTech programmer in the auto mode where it sweeps back and forth.
Then I set the servo rigidly in a jig and bolt an arm on that has a 12" pointer on it.
I set the servo at 900 1500 2100 and take the lash using a ruler in millimeters.
Usually the lash is taken with power to the servo.
I say usually because I do vary the technique depending on which brand of servo is being tested.
I'm a bit stymied by some of the readings I got today while checking out and logging
a few servos I hadn't done yet. Some were spank brand new, and a some were recent repairs.
To give some reference, some had .5mm's of play and some had as much as 2.5mm's.
A couple were around 4mm.
The reference from the manufacturer was that at 4mm the gears should be replaced.
Most servos they see are between 3 and 4 normally.
Yikes!
I know we take our linkages very seriously and spend lots and lots of time to avoid
slop and get precise geometry-resolution and linearity.
It seems to me that stuff like this boogers it all up
Heck, with 3 servos that have 2mm play each at neutral, would you even need to match
them up?
Maybe I'm too anal, but even the 2 and 2.5mm that I am seeing looks like miles
at the end of that pointer. Is it because it's so long?
To further twist my mind, on a couple of the brand new servos, I was able to move the
arm easily at the extremes for about 5mm's.
This didn't seem like gears, but just felt kind of loose if that makes any sense.
Doesn't seem right to me at all, but I'm in information overload right now.
I use 8411;s, 8611's, 5945's, and 5955TG's.
This was posted on another board with no responses, so some of you may be seeing it again.
I apologize for that.
Maybe I ask dumb questions[&o]
09-16-2006, 03:23 PM
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RE: Servo Geartrain Lash
The 5955TGs should have had virtually no slop in them -- their biggest feature right now is that their titanium gears just don't wear, even after hundreds of flights.
09-16-2006, 09:55 PM
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RE: Servo Geartrain Lash
I love my HS5955TG's, tight - no slop, center always, fast and very strong.
Have them in a 36%AW Katana and the four in the wing will lift the front of the plane off the ground when proped up and the tail wheel on the ground.
Have not got lots of time on them but they have been good so far.
Tony
Have them in a 36%AW Katana and the four in the wing will lift the front of the plane off the ground when proped up and the tail wheel on the ground.
Have not got lots of time on them but they have been good so far.
Tony
09-17-2006, 02:07 AM
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RE: Servo Geartrain Lash
I just picked up five 5955's myself.
Haven't used them in a plane yet, but they are the servos that I can move the when the programmer is at 900 and 2100.
By that I mean that I can move the servo arm about 5mm by hand while at those extremes.
Next time you have one on the bench, see if yours act the same.
I guess they're OK?
Haven't used them in a plane yet, but they are the servos that I can move the when the programmer is at 900 and 2100.
By that I mean that I can move the servo arm about 5mm by hand while at those extremes.
Next time you have one on the bench, see if yours act the same.
I guess they're OK?
