Asked — Edited

Modify A Micro Servo For Constant Rotation

I have learned a way to modify a micro servo I have many micro 9g servos Hextronik hxt900's. I bought a bunch of these from hobby king because there way cheap and had fine reviews there.

I found that the pot can not be removed because it's the axle for 2 of the gears. The gears are pressed on tightly and turn the axle witch in turn run the pot.

User-inserted image

After carefully taking the servo apart and pulling the gears off the shaft here are the steps i used to modify the servo.

(1) center the pot turn it left and right both directions and get the little metal tab as close to center as possible. (after centering i put a drip of super glue in there to make sure it stays put)

User-inserted image

(2) after realizing i have no drill bit that small (or even a drill that will hold a bit that small) I found a piece of welding rod that fit snugly and clipped a small bit of rod off with a pair of dykes leaving a little sharp burr on the rod.... That sharp burr on the rod turns out to be the cutter. If you have no welding rod i bet any small steel wire (that fits snugly in the hole) would work.

(3) The gear that sticks threw the top case is the tightest fitting of the two that need drilled out. I lightly tightened the small end in an electric drill and held the wire rod in a pair of pliers. while running the drill i pushed the wire rod in and out of the center hold a few times noticing small shavings of plastic being shaved out.

User-inserted image

(4) You will notice a small plastic tab on the bottom of that gear spinning around while on the drill. That little tab needs to be removed. I used a pair of toenail clippers and snipped it off..... It worked really well.

User-inserted image

(5) The smaller gear that needs drilling is not as tight on the axle and has 2 sets of gears on it so i would not suggest using the drill motor just spin the gear in your fingers against the wire rod. you will see some shavings come out.

That's it make sure there are no plastic shavings left on the gears.... maybe add some grease if you have it and put it back together making sure the gears spin loosely on the axle and that the gears are in the correct order and your set to test it out on the ezb. We may find it makes a bit more torque also because that second small idler gear is now spinning free and were not wasting torque spinning the pot.

Good Luck


P.S. I have found that both servos ive done spin at slightly different speeds.... Cheap POS's so i will be doing a few more and trying to find a couple that spin at the same exact speed.


Upgrade to ARC Pro

Experience early access to the latest features and updates. You'll have everything that is needed to unleash your robot's potential.