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landing gear servos problems

Old 06-20-2008, 07:08 PM
  #1  
ltbidrawn
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Default landing gear servos problems

i just bought a low-profile cirrus servo specifically designed for landing gear.
it's very torquey yet slow. sounded perfect for retracts.
the problem is the servo has a 190 degree throw that binds the pushrods.
despite using a spektrum radio, the servo appears to be non-adjustable—it seems to have a pre-set throw.
is there a way to reduce its travel?
or is there a way to use it with the existing throw?
or, is this simply a cheap $25 servo that should be trashed?

I'm thinking it's the latter of the three.
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Old 06-20-2008, 07:12 PM
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newjak
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You can adjust the servo travel through your Spektrum radio. Don't trash that servo just yet. The end point adjustment is not hard to do. If you don't have the manual I can guide you thru it. I have a DX6 and DX7
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Old 06-20-2008, 07:14 PM
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cliffh
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are you saying that the servo doesn't respond to a reduction of the "end point adjustment" on the transmitter? Have you tried another servo to make sure you are doing it correctly?

If it was me, I'd probably be setting the end point adjustment on the wrong servo.

Cliff
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Old 06-20-2008, 07:15 PM
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pd1
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Some servo arms either have slots to move the push rod location or have enough area to drill new holes.
The movement of the push rod at the servo arm must be the same as the throw length of the retracts.

The Spektrum does have end point adjustment so you can reduce the throw that way.

All that said, I really don't like mechanical retracts.
If the servo pivot isn't exactly where it should be, one retract always is troublesome.
Usually on retracting.

Paul

Last edited by pd1; 06-20-2008 at 07:15 PM. Reason: I type too slow.
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Old 06-20-2008, 07:57 PM
  #5  
ltbidrawn
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Default using a DX6

Originally Posted by cliffh View Post
are you saying that the servo doesn't respond to a reduction of the "end point adjustment" on the transmitter? Have you tried another servo to make sure you are doing it correctly?

If it was me, I'd probably be setting the end point adjustment on the wrong servo.

Cliff
ummm...endpoints? can you adjust travel endpoints with a DX6? i've been trying to adjust the gear via servo travel function. it is absolutley non-responsive....appears to be an "all or nothing" actuation.
am i doing this wrong. jeeeze, i hope so. i'm about ready to pitch the whole thing and make it a belly flopper.
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Old 06-20-2008, 09:47 PM
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newjak
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Originally Posted by ltbidrawn View Post
ummm...endpoints? can you adjust travel endpoints with a DX6? i've been trying to adjust the gear via servo travel function. it is absolutley non-responsive....appears to be an "all or nothing" actuation.
am i doing this wrong. jeeeze, i hope so. i'm about ready to pitch the whole thing and make it a belly flopper.
If you have the manual look on page 42

1. turn on the TX
2. press SCROLL and INCREASE simultaneously
3. press SCROLL until "TRV ADJ." appears
4. press CHANNEL button until desired channel appears.
5 move the channel or switch in the direction you want to adjust travel. move stick in opposite direction to adjust travel in opposite direction
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Old 06-23-2008, 03:42 AM
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flypaper 2
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Pretty well all retract servos are not adjusable for a reason. They go to the ends, then shut off cold so they don't draw power. What you have to do is put about a 15 degree bend in the end of the pushrod about 1/2" from the end, on the servo end. This way it won't bind with the servo hub and the opposite pushrod. Another point is to measure the full stroke of the retract itself from lock to lock, Lets say it's 1/2" Take half of that and measure from the centre of the servo screw, out 1/4" on the servo arm and drill a hole. Same thing on the other side. Now when it makes its 180 degree turn it moves the pushrod 1/2" Once you get them set up they are very trouble free.

Gord.

Last edited by flypaper 2; 06-23-2008 at 05:15 PM.
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Old 06-23-2008, 05:04 PM
  #8  
Glacier Girl
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Yeah I believe as flypaper said, retract servos are not travel adjustable.
It's a matter of using a servo wheel instead of the arm and playing with the distance from the servo center point to get it to work. Sometimes can be a real bugger.

I think it was Vintage1 that had something posted a while back about how to set up control rod lengths and such for a one time on the money retract install.
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Old 06-23-2008, 07:01 PM
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ltbidrawn
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Default i shoulda paid more attention in school

Originally Posted by flypaper 2 View Post
Pretty well all retract servos are not adjusable for a reason. They go to the ends, then shut off cold so they don't draw power. What you have to do is put about a 15 degree bend in the end of the pushrod about 1/2" from the end, on the servo end. This way it won't bind with the servo hub and the opposite pushrod. Another point is to measure the full stroke of the retract itself from lock to lock, Lets say it's 1/2" Take half of that and measure from the centre of the servo screw, out 1/4" on the servo arm and drill a hole. Same thing on the other side. Now when it makes its 180 degree turn it moves the pushrod 1/2" Once you get them set up they are very trouble free.

Gord.
dude, you're using like, geometry and stuff here. very clever. back in high school, I remember thinking how worthless this was.
guess i wasn't so smart after all.
great idea...thanks.
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Old 06-23-2008, 07:14 PM
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flypaper 2
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I know what you saying. Math was my worse subject. I think I learned more about it after I left school, when I needed it.
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