Cost: $5 – $40
Time: ~15 mins.
Tools Required: Small screwdriver or hex driver (to remove servo screws), flathead screwdriver, tape, white grease (optional)
Parts Needed: Replacement servo gears
Difficulty Level: Easy – Moderate
Whether you fly RC helicopters, RC planes, gliders or race RC cars, there’s a good chance at some point you’ve had a servo that’s gotten a little funky. It might have been from a crash because of excessive wear and tear or any number of other reasons.
If it’s making a clicking noise, not moving, moving a little then jamming or sounding tired, you’re in luck and can probably repair the servo yourself. In most cases, it’s a problem with the gear train and means that one or more of the gears is stripped or simply worn out.
While I’ve seen a lot of people replace servos instead of repairing them, there’s no reason to waste your money. A new servo might cost $25 to $150 when a new gear set is $5 – $10 for nylon gears or $10 – $40 for a metal gear set and it’s not that hard to do.
If your servo uses nylon (or plastic gears) one thing you might want to consider is replacing them with karbonite or metal gears which are stronger and will last longer.
While we’re on the topic of servo repair, some other things that can need repair are bent gear shafts (pins gears sit on) wires that become disconnected or bearings that have worn out. When you’re taking apart the servo to replace the gears, these are all things you’ll also want to quickly inspect. As long as it’s not the motor, amp or electronics, almost everything in a servo is user serviceable.
(Servo arm removed)
If your servo arm is still attached, you’ll need to remove it or you won’t be able to get the cover off.
(Tape on back of servo)
Put a small piece of tape on the back of your servo. This will hold the back cover on while you’re replacing the gears – if it comes off, it’s darn near impossible to get everything put back together correctly.
(Screws / case removed)
Remove the 4 screws from the back of the servo and take the front cover off being careful not to disturb the order of the gears.
Note how the gears are arranged so you’ll be able to put it back together. If you don’t have a similar servo to refer to in case you get stuck, you can take a quick digital picture to use as a reference.
Also note that the main gear has a tab on it that fits into a slot on the case – it’s very important when reassembling you put the tab back in the slot.
Remove the gears from the case and examine them. If any of them have missing teeth, make sure you fish them out of the servo or they may cause problems down the road. Clean the inside of the servo case using a paper towel or tissue.
Then pop the bearings and plastic pin off the main gear using a flathead screwdriver.
If they’re really tight, you might need to use a little heat from a soldering iron or pencil torch, but only as a last resort – you don’t want to damage the bearings. You also don’t want to melt anything, just soften it up to break the connection.
You might also want to give the bearings a quick look to make sure they’re still running smooth and add a quick dab of grease.
Put the pin and bearings into the new main gear and assemble the rest of the gears on the servo pins and casing.
Be careful to assemble the gears in the opposite order to which you disassembled them. Refer to your spare servo, notes or pictures if you need to.
Before putting the case back together, you’ll need to grease the gears. You can either reuse the grease from the old gears if it’s still clean, or replace it with new grease. White grease works best, but others such as TriFlow can also be used.
I used white grease in a can and just sprayed it on before putting the case back together – it’s quick and easy. You don’t want to put it on too thick, or it will just get in the way and gum things up.
Once you everything has been greased and all the pins and gears are in their respective holes, it’s time to close everything up.
Put the case together, tighten the screws finger tight and check everything to makes sure it’s working as it should.
Don’t overtighten the case screws as it can cause the gears to become jammed and don’t force the case together – when everything is together properly is should smoothly slide into place.
When everything’s done, plug it back into your receiver, turn on your radio and check to ensure everthing’s working properly. You’ll also need re-attach the servo arm in the neutral servo poistion, so now would be a good time to do so.
(Completed regearing of servo)
That’s it. The whole process might take up to 30 minutes the first time, but after you’ve done once, you can usually get the gears replaced in 10 – 15 minutes and your servo will be running like new!Have a question about this article or anything else RC Heli related? Ask it in our brand new RC Helicopter Forum and you'll get expert answers quick.
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