SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jul 12, 2012, 04:45 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
560 Posts
Discussion
Add one-way tension to help servo centering?

I have an older full house glider with worn metal gears in the wing servos. The servos are glued in and I can't change the gears with them installed.

If I add tension to the servo arm in one direction, will it keep pressure on the gears enough to help the control surfaces return to center more accurately? All I'm looking to gain is repeatable positioning for efficient cruise and thermal settings. Right now the control surfaces have almost 1/4" of play. I have checked that the slop is in the servos, not the external linkages.

Thank you,
Tim
2motheus is offline Find More Posts by 2motheus
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 12, 2012, 05:16 PM
Registered User
R.M. Gellart's Avatar
Joined Nov 2005
3,549 Posts
I would be less concerned with centering versus when those servos flutter on a launch or fast pass. There has got to be a way to get them out, cause in the big scheme of things, they sound like they are nearly unuseable.

Marc
R.M. Gellart is offline Find More Posts by R.M. Gellart
Reply With Quote
Old Jul 12, 2012, 08:16 PM
Registered User
United States, MA, Waltham
Joined Dec 2001
6,931 Posts
They'll be a lot less likely to flutter with that tension on them, though possibly not as resistant as with new gears. And if it was me, I'd check for an increase in current drawn by the servos. I'm thinking this might help, but of course it's much better to change the gears!

What kind of glue?


(I may not see response until next week)
lincoln is offline Find More Posts by lincoln
RCG Plus Member
Latest blog entry: paper blast tube test
Reply With Quote
Old Jul 12, 2012, 09:40 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
560 Posts
Thank you for the input.

Good idea checking for extra current draw if I try some one-way tension on the arm.

The plane is an older built up Topaz. The servo bays are capped on top with a plate of yellowish G10(?) or fiberglass. The plate is translucent enough to see the glue spot holding the servo, but there is no glue beyond the servo edges to test. They seem to have no flex, though, so I think the glue is epoxy. The servos are not wrapped in tape.

Tim
2motheus is offline Find More Posts by 2motheus
Reply With Quote
Old Jul 12, 2012, 10:06 PM
Registered User
United States, MA, Waltham
Joined Dec 2001
6,931 Posts
Heat may (or may not) work. Some epoxies soften at as low as 140F or so. You could also use a dremel with some kind of depth stop to cut the g10 around the glue spot, which would still leave you something to glue to.
lincoln is offline Find More Posts by lincoln
RCG Plus Member
Latest blog entry: paper blast tube test
Reply With Quote
Old Jul 12, 2012, 11:56 PM
Registered User
Toowoomba, QLD, AUSTRALIA
Joined Jan 2008
614 Posts
I've seen photo's where sombody took to glued in servos with a dremel and ground them out.
bjr_93tz is offline Find More Posts by bjr_93tz
Reply With Quote
Old Jul 12, 2012, 11:59 PM
Eggcellent...
tewatson's Avatar
United States, CA, Orange
Joined Oct 2006
2,430 Posts
If there is no glue ridge around the servos, try twisting them gently with flat-jawed pliers. They might pop loose.

Tom
tewatson is online now Find More Posts by tewatson
Reply With Quote
Old Jul 13, 2012, 05:26 AM
Registered User
R.M. Gellart's Avatar
Joined Nov 2005
3,549 Posts
Tom is thinking exactly what I am, those things have got to be able to twisted somehow.

Marc
R.M. Gellart is offline Find More Posts by R.M. Gellart
Reply With Quote
Old Jul 13, 2012, 10:05 AM
Registered User
Mark Miller's Avatar
St. Louis, MO
Joined Oct 2002
2,716 Posts
You should do what ever it takes to replace the servo. They should twist out or if all else fails a dremel with a grinder attachment will work. Also it may be easier to see if the G10 plates will come out easier to get better access. Adding one way tension is kind of akin to using two popcicle sticks and tape to fix a flagging erection.

BTW...I sell popcicle sticks and tape if anyone is in need.
Mark Miller is offline Find More Posts by Mark Miller
Reply With Quote
Old Jul 13, 2012, 01:13 PM
Registered User
uncledale's Avatar
Fort Collins, CO
Joined Nov 2006
157 Posts
Is this a new line of sales for you, Mark? Ay yi yi.....
uncledale is offline Find More Posts by uncledale
Reply With Quote
Old Jul 13, 2012, 06:55 PM
Registered User
Mark Miller's Avatar
St. Louis, MO
Joined Oct 2002
2,716 Posts
As the glider population gets older they have different needs. I am just trying to firm up a softening market.
Mark Miller is offline Find More Posts by Mark Miller
Reply With Quote
Old Jul 13, 2012, 09:20 PM
Registered User
John Walter's Avatar
USA, IL, Naperville
Joined Feb 2003
857 Posts
I learned this trick from Cody to remove glued servos from one of my Supras.

Make 12-18" loop of strong string (say, winch line or a bit smaller). Put one end around the servo arm and the other through a suitable handle (say a screw driver. Have a second person (or 2) hold down the wing very firmly so it can't move. Make strong, sharp tug on the handle and pop out the servo like a loose tooth! Don't pull gradually, that will damage the wing. It's the sharp tug that pops the servo out.

I was apprehensive when we did this at the Nats a couple of years ago, but it worked like a dream. I have since done it one other time with no damage to the wing.

Caution, your results may vary, so don't blame me if you try it and it doesn't work!
John Walter is offline Find More Posts by John Walter
Reply With Quote
Old Jul 13, 2012, 09:56 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
560 Posts
Thank you for the feedback. I've received more suggestions than necessary to solve my current dilemma...

John - great to know - but this is a built up wing with much of the servo plate supported by two light balsa ribs. Nevertheless, with proper support of the plate that the servo is glued to, I think this might work.

The consensus seems to be that the servos must come out. I plan to fly the plane tomorrow and don't have replacement servos, so will not get to this for a while. I'll try to give the rest of the story when I can.

Tim
2motheus is offline Find More Posts by 2motheus
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Hitec One Way Trainer Cord, PN 58310 Greybranch Hitec/Multiplex USA 3 Jul 03, 2012 04:41 PM
Discussion mini cp servo saver mod tension? dreamz123 Micro Helis 2 Jun 16, 2012 06:06 PM
Question Add tension to modded S107 throttle? Chris.S. Coaxial Helicopters 4 Dec 01, 2010 09:06 PM
Help! One of my ailerons is not centered using a one servo aileron beginner4life 3D Foamies 9 Oct 26, 2010 11:26 PM
Discussion help find easiest way to add weight and how? andrewfl Electric Sailplanes 20 Jul 14, 2010 07:13 PM