Anyone have problems with oil getting inside the throttle servo when mounted in the engine compartment. This is the first time trying this. I saw an article in one of the mags that showed how to mount it to the engine mount. If so what measures do they take in trying to seal the servo? I know vibration can ruin a servo so i'm using an old futaba s-133 if it gets ruined that way i'll mount the next one inside. This setup is so easy to do, it will be worth it if it works ok.

with the 4-stroke you won't have much oily gunk in the engine compartment.

The servos are fairly well sealed from gunk getting to the electronics. After use on a PBF (wherre the exhaust goes straight on a sevo when the exhaust deflector pops off... and they seem to pop off every 3rd flgiht ont he PBF's..) I opened up the servo that was most oil coated... and there was no engine oil in the gears. The electroncs section was totally dry. From that point... I don't worry about exposed servos at all... I just inspect periodically to verify no oil got past the gears. (never has yet.)

Depends on the servo type.
Aircraft servos WILL get fuel in the servo.
Car and boat servos (ground) will be resistant to oils.

I have 4 combat models with a full size Futaba servo mounted directly underneath an OS25FX plus 2 sport models with a mini servo mounted under a 46FX and GMS47. Haven't had a problem yet. The servos are mounted on thin foam tape and are held in place with a zip tie. I use a flimsy bracket between the firewall and servo to reduce the risk of stripping gears in a crash. Mounting the servo under the engine is a great way to shift some weight in a tail heavy airplane.

Hi!
Why mount the servo in the engine compartment in the first place??? Oil and grease ...and vibration everywhere...not the best place for a servo...
The picture you are showing seem to indicate that there is plenty of room behind the firewall for the throttle servo.

Regards!
Jan K
Sweden

Thanks for the replys I wanted to mount the servo where i did because i wanted some more weight as far forward as i could get it without adding extra needless weight to the aircraft in the form of lead. I will be mounting 2 mini servos underneath the stab for the rudder and elevators. The reason i'm putting the servos at the control surfaces is because the plane has a full length crutch inside the fuse that makes routing pushrods harder, i don't even think i could get a pushrod into the rear section of fuse now, they would have had to be built in. I hate making pushrods anyway, i would much rather do it this way. Keep in mind this is a plane of my own design, this being the first one, sometimes when scratch building you don't think of every contruction step until it's too late then you just figure out a solution. Position of the battery will be able to balance the rest.

I am much more concerned about the look of that pushrod arrangement than oil in the servo. Have you tested that to make sure the servo moves the throttle smoothly?

Good point about that pushrod set up, you might want to change that to a bell crank set up, and what size motor are you running, are you sure mini servos in the tail are enough.

Yes I tested the throttle servo everythings ok there. It opens and closes the throttle completely, no binding at all. The mini servos in the tail are real close to being the size of a standard servo with 47 oz/in torque, i don't know why there even called mini servos. Can't see any problems with them on a 40 size plane. Engine is a Magnum fs-52, span = 52", area 540 sq/in, length 39".

I have used Hitec servos in the exhuast path for a couple years on a Spad3d .They seem to be fuel proof.I agree with Bent.

Actually my servo won't be in the exhaust path. The cowl encloses it completely. The cylinder stiks out the side of the cowl quite a bit, the pipe and muffler are completely outside the cowl, but engine compartments allways get covered in oil at least mine do. Thanks for the replys i probably don't have anything to worry about.

Canadagoose, I've been doing that for almost 20years now. I used to put the servo in a plastic baggy then screw through it and poke the control rod and wires through it and that did keep a lot of grime off the servo. But one day I decided that the servos I was using were not worth all that effort. I use std cheep-o servos for throttle and started mounting them raw on the old aileron trays they would give us with the radios. Then I got introduced to PFM! Now I use that stuff to bond the servo to the engine mount or fire wall with pull ties, but the engine mount is the best place I've found.

Yes the servo gets covered with a nice coating of dirt and oil. But I have this setup on at least 8 planes with 100 of hours of air time without a single servo fail!

Good luck

Joe Felice

P.S. PFM is sold by Innovative Model Products. Its not cheep! Its also sold as R6000 but it's not the same, just does not hold as well in the engine compartment application.

That engine has a nipple for venting the Crankcase. Make sure you put a piece of fuel line on that nipple and vent it outside of the cowl. A lot of gunk can come out of there!