I recently graduated from an electric park flyer to a nitro plane--sturdy birdy with an os .25 engine. I've flown it three times on my property. When I tried to land it the second time I came in a little to high and fast and applied throttle for a go round, but the plane went behind a barn on our property and I lost sight of it. You can guess what happened--it crashed pretty hard nose first.

I repaired the engine and flew again without incidence, but after I landed, the throttle servo would not work. It seems as though the internal gears may be stripped. I can hear the motor moving but no motion on the output. Is this something that happens to servos from time to time?

yep we see it all the time.... especially if im in a crash or something.... ive even had my micro servos go in my foamies from hard landings....


}{unter

i dont know what kind of servos yyou have but if ther jr you can order gears and replace them, just take the four screws out of the case and look

Servo gears will strip in a crash when the control surface (in this case, the engine) is forced back against the servo position. It's an easy fix.

1. Buy the proper gear replacement pack from your LHS.
2. Carefully open the top of the case, noting the position of all components.
3. Take out the old gears (this is why you write down the position of them).
4. Be sure you get all the little pieces of teeth out.
5. Install the new gears, referring to your notes for placement.
6. Lubricate them with a SMALL mount of white lithium grease. You can probably find this at WW in the boating or automotive department.
7. Reinstall the cover.

Dr.1

Or just spent 10 bucks for a cheapie servo

The trouble is the cost for the replacement gears may be 80% on the cost of a brand new servo. When I have gears go, I just buy a new servo.

Thanks for the responses. The servo is a Futaba 3004 and costs about $14.00. I will probably buy a new one and the five dollar gear set, put the new one in the plane and see if I can repair the stripped one.

Thanks,

Carl.

That works for me, Fastsky, if the servo is inexpensive (148, 3003, etc.). If it's a hi dollar unit, replacement gears are cheaper. Besides, let him replace a gear set once. He'll learn more about how his swervos work an how they get so much torque from such a small motor.

Dr.1

fwiw, I keep spare gears for all my servos in the shop. gear replacement is really quick and easy, and gears are usually $2-$3 for your basic nylon geared standard servo, depending on the brand.

For some odd reason Tower charges an arm and a leg for gears, but other hobby shops, such as Servo City, charge a lot less for the same gears. I don't know if SC has Futaba gears, I mostly get Hitec from them. So shop around if the price seems high.

I also agree that it's worth doing at least once on a cheap servo now, rather than waiting to learn how on a much more expensive servo.

Thanks for all the input. I found a local hobby shop that had a replacement set of gears for $5 and replaced them last night. The old set was badly damaged--missing teeth on some of the gears. Servo is good as new and ready to go. I am going to keep a set of gears on hand in case it happens again.

Thanks.

so like increased mechanical advantage due to the different radii of the gears? u could just explain it and not make him tear his servo apart... especialy if uve never doen it before, its very irritating to try and get all the gears back together.


also if u can find metal gears (there more expensive...) but they are much more resistant to sripping than nylon. i prefer using metal gears on my servos, its just a mater ofpreference thoguh

The speed of a modern standard servo is still pretty quick. A standard Futaba S3004 is Speed: 0.23 sec/60 degrees at 4.8V. I have some older Futaba servos given to me and it takes over a second to move the 60 degrees. I used them on a cheapy plane that was given to me but I don't use them any more. [8D]