Wing Servos - making them easy to get out

[Jef Ott]

12 hours ago, oipigface said:

There's another way detailed on my Graecalis build. (Episode 8, I think) Essentially, I fitted rails that grip the servos on each side - finger tight - then screwed a G10 strap over the top. The tops of the rails are a tiny bit lower than top of the servo, so the servo is gripped tightly by the strap.

Easy to build, and easy to remove the servo. Probably wouldn't work so well with thin servos.

Can you provide a link please oi?

It would be good to be able to see your way too, and I have looked for it a couple of times and become distracted, forgotten what I was looking for. Others may be reading this with the same inability to remember what they're doing, and I am sure a link here would be valid (on this thread). 

Jef

[Rennell]

Thanks for the detailed project images. very precise work.

[EssexBOF]

On wing servos with 3 lugs(Turnugy777's) I cut out a U shape from Lit Ply 1/4 thick.

For those servo's of conventional mounting, I remove the output arm and slide heat shrink over from the lug side, half shrink then cut hole around output shaft, then shrink down tightly with heat gun. Care is needed not to get to hot so as to blow a hole in the heat shrink. Rough up side to be glued down on the wing skin and glue in with Araldite Rapid as this is more flexible than other epoxy glues. It is worthwhile adding a layer of carbon cloth, onto the skin as they are quite thin and light

Use this method for servos in the fin type mounting as well

[thermaldoctor]

I would have thought commercially available mounts from servorahmen or the plywood ones Stan at Phoenix Model Products sells would be an awful lot less hassle and much neater?

[Rob Thomson]

Lol.  After looking at the work on the ply trays....  My 3d printer is looking tempting! 

[isoaritfirst]

I build my own frames from Ply very quickly and easily.

1 either find some ply the same thickness as the servo or stick a few pieces together ( better as you get more ply's)

2 rough Cut into a strip slightly wider width you want for the frame and long enough for 4 frames plus a bit.

3 Cut a "U" into each end. The "U" should be the width of the servo, I never measure this just add another cut until it fits. ( I use a band saw with a stop clamped in place and make successive cuts to identical depth to remove material.) I guess the depth as well, just making it deeper than I require.

4 Now I sand the face of the "U" on the disc sander until the depth is just right to meet the servos lugs.

5 Cut off both ends and repeat into the fresh ends of your stock

6 cut and sand as before and now you have 4 x frames that fit around the bottom of the servo and up to the lugs.

If required - Repeat a similar operation for around the top of the servo.

7 Cyano then onto a thin ply backboard with them positioned tight around the servo.

8(a) cut them out of the back board and then sand all external faces on the belt sander until the frames are neat and of an external size that is appropriate. Also sand the thickness down to a nice match, easier than finding ply of the right thickness) 

8(b) alternatively- don't use a back board - just stick the pieces to the wing skin. (slightly trickier.)

 

Generally nothing is measured or done with any great care during the construction stages - making it very quick, yet the finished item is a great fit and very neat - due to the final sand.

Quicker than popping to the shops...

 

 

[Jef Ott]

1 hour ago, thermaldoctor said:

I would have thought commercially available mounts from servorahmen or the plywood ones Stan at Phoenix Model Products sells would be an awful lot less hassle and much neater?

Servo mounts might not be available for the servo that someone has selected as being the right tool for the job, and if they already have all the materials at hand, the job is complete in less time than even the best mail order service. Hopefully it has been demonstrated that mostly simple hand tools are all that is required.

Please don't discourage people from learning basic skills, but maybe instead put some effort into encouraging those that may want to have a go at making their own parts, but might need a little stimulation to do so.

This is actually in a section called the Builders Workshop. Suggestions on here to buy the items are not really needed, or perhaps I am wrong and the forum should be renamed, the Assemblers Bench.

Well done to all those that are keen to show others what they can achieve in their workshops though, even if they are not appropriate for all types of glider installation, or if similar items can be bought. 

Thanks. 

[oipigface]

Another method that is even quicker is just to wrap the servo with masking tape and glue it in. It's best to use just enough epoxy to squeeze out around the servos edges.

Then you can remove the servo easily by cutting the masking tape and pulling it out, sure in the knowledge that you will have a good guide to where it fits back in.

[EssexBOF]

5 hours ago, EssexBOF said:

On wing servos with 3 lugs(Turnugy777's) I cut out a U shape from Lit Ply 1/4 thick.

For those servo's of conventional mounting, I remove the output arm and slide heat shrink over from the lug side, half shrink then cut hole around output shaft, then shrink down tightly with heat gun. Care is needed not to get to hot so as to blow a hole in the heat shrink. Rough up side to be glued down on the wing skin and glue in with Araldite Rapid as this is more flexible than other epoxy glues. It is worthwhile adding a layer of carbon cloth, onto the skin as they are quite thin and light

Use this method for servos in the fin type mounting as well

I forgot to mention that the servo can be released by cutting through the heat shrink, residual glue removed with a Dremel tool. Also wooden mounts are of limited use for servos mounted in the rear of the fuselage i.e. rudders

Tried masking tape years ago and had no faith in it as it  can lose its adhesive qualities if subjected to heat of the sun on fine days, that why I use the method described now.

Main snag with a wooden mount of any description is that if another type of servo is used that does not fit the mount you have to remove it as I know to cost, unless you are sold on one type of servo.

 

 

 

[Jef Ott]

Good points there Brian,

Know what you mean about not trusting masking tape; I have had a couple of instances of masking tape wrapped servos gradually letting go (over the course of an hour or so), which gives almost in-detectable slop to start with and gradually less control, which can cost gliding performance even on slow models.

Dread to think what might happen on a fast model...

I suppose that nothing lasts forever, and servos do eventually wear out, so buying spares when buying for the initial assembly makes sound sense, especially if fitting frames.

[isoaritfirst]

If you use masking tape wrap the servo very neatly with cuts in the tape allow it to fold very neatly around the corners. 

I had models that had wrapped servo with no problems over many years. And all of my models go fast 

[Buzz]

2 hours ago, isoaritfirst said:

If you use masking tape wrap the servo very neatly with cuts in the tape allow it to fold very neatly around the corners. 

I had models that had wrapped servo with no problems over many years. And all of my models go fast 

I have also regularly used masking tape method, but would add to make an overlap on the face of the servo that goes against the wing skin. I am sure that this helps keep the masking tape secure and tight.

My planes go almost as fast as Mikes 

[oipigface]

3 hours ago, Buzz said:

I have also regularly used masking tape method, but would add to make an overlap on the face of the servo that goes against the wing skin. I am sure that this helps keep the masking tape secure and tight.

My planes go almost as fast as Mikes 

Sad to say, the only plane I've had that has gone faster than Mike's, had a neat installation with frames done at the factory!

Whenever I do my own installs in thin wings, I use masking tape wrapped round twice as Buzz suggests, and I can't recall ever having had one work loose. I fly both in quite cold conditions and in some quite hot ones. A taped installation can be made almost bulletproof by fitting a strap over the top of the servo. (Of course, this also makes it a little more difficult to remove.)

 

[Rob Thomson]

Trick with masking tape...   Sand the way edge. 

 

Makes it stick better to itself and of course the air frame! 

[isoaritfirst]

Its like anything on here - there is always someone that has a problem by not understanding the "issues". 

That doesn't make the technique itself faulty just the execution..

 

[isoaritfirst]

The other issue with any servo mount onto a moulded wing is how the install will effect the wing skin itself.

A big flat plate stuck to the skin can end up creating a big flat wing skin. 

This can be alleviated by sticking the plate down with a thick mix of epoxy and micro balloons to create an infill between the skin and the plate.

Or you could sand the plate to match the profile.

Don't weight it down while it sticks, let it sit gently on its bed.

Bigger plate spread the load - but generally create larger flat areas that show on the top skin.

Smaller plates are less prone to this but offer less support, however this can be remedied by adding a fix to the opposite skin.

There are various ways to do this. Current favored choice is a strap across the servo opening that is thick enough to be fixed to the servo as well as the inside of the wing skin.

Alternatives can be to simply make a soft balsa block to fit ontop of the servo and fix the servo cover to this and its own fixing positions with a removable glue such as UHU.

Or box the servo hole out with vertical ribs before installing the servo plate. Light and simple, with soft balsa or even blue foam. Dont force fit, or they will show. loose fit on a bed of epoxy/balloons.

 

With all of these - try to use as little glue as possible, servos get knocked out along the line of the push rod - so actually require very little fixing if they are done right. Also probably better in a bigger hit to break out the plate than smash the servo or the surface.

Over the years I have used less and less without issue

[Brett82]

I agree with what Mike says above about not trying to use to much glue and its better for the servo to pop out than for the servo or wing to be destroyed because there is so much glue it just doesn't budge on a really heavy impact. 

But that makes me wonder about how to actually glue them in. I've always just taped and glued servos in as I've never worried to much about stripping gears and such due to the types of models I used to fly. F3F is now making me think more about it though.

The tape method is simple enough: wrap the servo in tape, glue the tape to the skin, to remove the servo carefully cut the tape, take out the servo then remove the tape (and possibly glue) and repeat the process for the new servo. 

If I have got this right then in Jef's last pic the tape at the back of the frame will stop any glue going on the servo itself so it can be glued in without removing the servo. If you don't use the tape then would you simply spot glue the frame down with CA, remove the servo, then epoxy the frame being careful not to get the epoxy onto the inside of the frame where the servo goes? I suppose micro balloons or micro fibers would increase the thickness of the epoxy so it doesnt run and can be positioned around the outside of the frame. 

I might have answered my own question but would be good to see if you guys agree. Thanks

Brett

[Jef Ott]

5 hours ago, isoaritfirst said:

Or you could sand the plate to match the profile.

Don't weight it down while it sticks, let it sit gently on its bed.

Bigger plate spread the load - but generally create larger flat areas that show on the top skin.

 

Yes, totally agree, use the thinnest smear of Araldite Rapid which will still squash out to form a slight location bead, profile the frame and chamfer the edges to reduce the adhesion area and 'soften' the edge (see photo in OP), so that it lets go with the shock of impact. When I have to replace the frame (following such an unplanned event), it gets a drop of cyano into the epoxy 'female', making field repairs as good as new.

[Phil.Taylor]

Masking-taped-epoxied servos are a pet hate of mine when buying used planes. Masking tape is designed to come unstuck - and I dont like refixing the resulting wobbly servos - had to do it several times. So - please use electrical tape or heat shrink if Im going to be buying one of your planes 😄

Phil.

[Jef Ott]

6 hours ago, Brett82 said:

If I have got this right then in Jef's last pic the tape at the back of the frame will stop any glue going on the servo itself so it can be glued in without removing the servo.

Yes, spot on, Brett. 

It is easy to get an even, thin, smear of Araldite Rapid right over the surface that way.

That last pic's masking tape barrier was just to show the idea. When I fit the frame into the wing, the glue face will have been profiled (to fit the Xantia top surface), rather than flat. I will post pics when doing the install.

I also make a point of dry fitting it and getting the pushrod alignment perfect, then mark the wing and frame so that the freshly epoxied frame can be placed onto the marks for that little extra confidence.  Again see the OP pic.