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4g Servo Mounting

Ok, it happened a second time! I glued in a servo only to find it totally frozen. Actually it was fried, baked, cooked, or somehow melted inside by the glue. I applied a sparing dot, but that was still too much heat for this tiny servo.

My plane is a Sparrow, and after a number of crashes one of the servos came loose. That has also happened a couple of times. The glue adhesion to the plastic is a little iffy. I generated a fix, and will make a request to Flite Test as a result.

This fix takes care of both problems, and doesn't make a build that much more complicated. My request to Flite Test is to include a couple of cutouts in the Quick Build Kits shaped like below. The servo next to the cutout is the dead servo, used in this case to prototype the updated mounting method.


Below is the servo glued to the mount by the ears, which keeps the heat away from the gears and other internal parts. I know, I mounted the servo backwards in my haste, but because this was only for strength testing, I didn't tear it apart and start over. At this point there are a couple of options. It is possible to leave the parts which go under the ears too long, and easily trim flush with the servo using a knife extended long from the handle. In addition, for Aileron servos, like in the Tiny Trainer, the back can be cut off flush with the servo as well. It really doesn't add much at this point. Applying a little less glue here is also a good idea to facilitate any of the trimming which may need to take place.


The next photo shows a test piece acting as a fuselage wall. The glue is applied to the foam only and the servo is glued to the fuselage by this mount. I tried pulling, twisting, pushing, but that servo is STUCK to the fuselage! I was surprised at the strength.


I will mount servos this way if I am faced with gluing to the servo body in the future. Has anyone else seen the same problems? I hope this helps.

Andy; Thanks for the caution. I wonder if you could make the foam in "U" shape with hot glue edges together like a fuselage. Maybe I'll make one i have in mind and take a photo of it.


Active member
I use the 9051 servos in my builds. This issue you describe is interesting. I have noted on the 9051 to have one particular problem and that is never screw on you control arm when it is energized or you will strip its gears. Also not to please with the smoothness of their movement but this maybe caused by mishandling. I never been able to associate the reason for their failure to hot glue. We will follow the along and see what other come up with. Have a good at the field...


Old and Bold RC PILOT
If hot glue is causing you problems then do not use it. Try cutting the servo hole slightly smaller than the servo and force the servo into the hole. The FB will hold it firm. For safety just apply a small piece of Duct tape across the servo body, (FB, servo, FB), to stop the servo working its way loose.

Makes field exchange of servos so very easy.

Have fun!


New member
I have had a number of problems with hot glued servos coming loose on several planes. I like the U shaped FB idea and plan to try it out the next time I mount servos to the inside of a fuselage.


Well-known member
I've used a lot of micro servos with hot glue and haven't had an issue... Once in a while ill get a blob too big/too close to the exposed gear of a micro linear servo but I can usually just trim a little with an exact knife and make it work.

I have, however, discovered a lot of different patterns on the plugs. (-)(+)(s) vs (+)(-)(s) and I've fried several by not paying attention to that (or by just putting red to red/black to black when I needed to switch the pattern)