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Best method for mounting teflon servo arms to a base (metal or wood)?

I am currently working on a simple tilt system for a mobius camera on a quadcopter. Basicly, when FPV flying, I want to be able to look directly down, and straight ahead, so I know what is below me as well as get some good footage.

I have 3 parts that need to be mounted together. A small, sub-micro servo, a plastic shell/case for the mobius camera, and a fabricated piece that extends from the bottom of the quadcopter, to the servo, allowing just enough room for the servo to turn the camera ~90 degrees.

I have hot glued the camera case/shell directly to the servo, so that the arm of it is free to turn directly above the center hole. The arm that mounts there then somehow needs to be mounted to a little board or something that extends down from below the quadcopter body. That piece is not difficult to mount, however, the teflon servo arm needs to firmly mount to that piece. So far I have tried hot glue (peels right off the teflon after some vibration) and universal JP weld (that grey and black stuff that takes a REALLY long time to set, and same problem).

Whenever possible, I prefer to not use glue, as it is messy, sloppy and bad-looking, as well as permanent and fragile when it does work. I may sometime plan to change the design, I would prefer better mounting techniques, and do not want the bonds to break with large shock from a crash landing.

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rickharris2 years ago

Servo arms expect to be connected to a push rod via the holes. If you want to connect direct screw or bolt a small ply wood plate to the servo then you can glue the ply wood using common glues.

-max- (author)  rickharris2 years ago

I think that is what I wil have to resort too. In the mean time, I am going to need to repair the quadcopter, I was having issues with the PIDs, and dumb-thumbed it, and completly busted the wood frame. Once I build a new, better design, I will try that.

seamster2 years ago

It's sounds like you need to use mechanical fasteners, rather than adhesives. If you added some photos of the parts that need to be fastened together, that would be helpful to be able to determine what's feasible.

-max- (author)  seamster2 years ago

http://www.alofthobbies.com/media/catalog/product/...

That is the servo arm that I am referring to. I am not sure exactly what material they are made out of, teflon is just a guess. It could be nylon too. A slippery plastic none the less, and it feels different than a polyethylene, the stuff water bottles are made of. The feel of it is closer to a milk jug, if that means anything at all.

The leftmost one in that picture needs to be mounted to a strip of metal, or a block of wood. Since those objects are ready avalible to me, I can make them any shape I want.

The JP weld stuck to the metal fairly well, and the servo arm broke cleanly off, leaving an inprint of it in the expoxy. I was able to press fit it back it, and smere hot glue completly around everything, so that even if it dies not bond to the plastic, it still will be held into place solidly. I wguess I will see how long that can hold up.

seamster -max-2 years ago

Hmm. Those look like standard nylon servo arms. The piece that you are attaching... does it need to pivot at the end of the arm, or is it being attached as an extension? Or something else.

Any photos of the part you need to attach to that, or even a sketch of the desired final assembly?

-max- (author)  seamster2 years ago

Purely as an extension. I really just need it to be longer, and have a bent flat surface at the other end for crewing into the bootom of the wooden quadcopter frame. It is currently mounted with hot glue, since I am too lazy right not to get out a drill and mount it permanently with screws. When I get the chance, and find some sharp drill bits and wood screws short enough for the job, I will do that.

seamster -max-2 years ago

Ah. Without seeing the actual parts, I'd say a pair of tiny bolts and nuts, one through the farthest hole in the arm, and the second through a hole drilled closer to the other end, so there is good support. Interesting stuff!

Are you going to post some info on it when you're done?

-max- (author)  seamster2 years ago

I figured it would boil down to that. I do not know if any local hardware shop would have the ridiculously tiny screws or bolts/nuts that I would need. The servo arm, at the end, is really thin, thinner than the small nuts/bolts I already have. I guess I could also try JP plastic weld, or something else designed for nylon.

If you can't find the small hardware you need you could try the MAcGyver method...

Push thumb tacks or nails through holes in the arm + mounting plate. bend the ends and secure them with some sort of epoxy/glue !

If you have all Four point of contact, it should survive a few good Crashes :D

Did you think of Loka glue?

Or UV curing resin in general for that matter?

You could connect your part to the servo arm, make a nice mould from Playdoo and fill with UV curing resin.

Apart from that Cyberbond has special glue for Nylon and JB has the plasti weld stuff, the normal JB won't stick to Nylon.

Bond It also has special glue for Naylon in the list, especially the B4-xx series of glues.

You can dissolve Nylon in Formic Acid and through this create strong bonds to other Nylon parts but weak joints with dissimilar materials - and it is not a nice acid to work with due to health risks.

But as I said 2K stuff like KnetIt for metal gives extreme strong bonds that can be drilled, tapped and whatever more, when I use it with good enough all round coverage it is usually not the bond that fails.

Although for a clean and nice looking joint I would prefer UV curing Epoxy resins.

-max- (author)  seamster2 years ago

If I do, it will be an entire 'my quad build' log, and I may include those details. I will see what I can find, thogh at the furthest end, that servo arm is only like 2.5mm wide, and the hole in the center of it is like 300 microns. It is like 20AWG wire or something. In fact, that is what is really was designed for! Thats why there are so many holes. These things are meant to be mounted on a airplane, and control all the flaps, with a little wire.

Do it the other way around:

Take the servo and press it into some formable 2K putty to give you the gear pattern.

Do the putty on a flat surface and cut to the shape of your desired arm.

With this you get something that can be easily glued and it still sits firmly on the servo.
There is not much that can stick to nylon unless you use an acid erosion process first on the nylon.

-max- (author)  Downunder35m2 years ago

Putty, ehh, this needs to survive some crashes, I have bent bits of metal from crashing, punctured lithium batteries, and totaled the wooden frame time and time again, will that survive?

I've got some hydrochloric acid available, as well as citric acid, acetone, rubbing alcohol, ethanol, vinegar, and potato chips. No idea if any of those will be helpful in eroding the plastic, but if anything is for sure, HCL-flavored chips are way more sour than lays salt 'n vinegar chips!

Anyways that may be somthing to try, I will look into it!