So over the holiday I managed to finish my Servo Winch 2.0. I started with a TowerPro MG996R, which only cost $11
(click here). You will also need M3 threaded rod (minimum of 45mm.
I used this one), 2x M3 nylock nuts, several small M3 washers, a bearing, an aluminum spacer (I used
this one), two small round servo horns, and some decent epoxy. (I used Loctite 5min epoxy)
It's being powered by an XYS-BL20A micro brushed 2S 20A ESC ($14 on eBay. Make sure to get the one WITHOUT a brake)
Step 1: Remove the four bottom screws, remove the bottom cover, and pull out the control board.
Step 2: Remove the wires going to the back of the motor. The little red dot marks the + connection. This will be where you attach the wires going to your winch controller.
You'll note a single screw at the bottom of the cavity previously covered by the control board. This connects to the potentiometer. Remove that screw and the potentiometer.
Step 3: Remove the top cover (taking note of the order of the gearing, and remove the final drive gear. Underneath, where the potentiometer had been connected, you will see a translucent plastic insert. You have two options here. 1) Remove the insert or 2) Drill it out. I couldn't find a way to remove it in one piece, so I went with Option 2. Don't worry about removing all of the plastic. Remove just enough that you can fit your threaded rod through. (Be careful not to drill out the threads in the metal) [This photo shows the drive gear sitting in the top cover]
Step 4: Cut a slot in the front of your housing for your line to pass through. IMHO I cut mine a little too wide.
Step 5: Cut a hole in the bottom cover. This should be just wide enough to fit your bearing of choice. (I used a spare one from my T-Maxx/Rustler. These need a spacer to fit snugly on the M3 rod)
Step 6: The small circular servo horns were too wide for the servo housing, so I had to shrink them. The easiest way of doing is to attach them to a Dremel cut-off mandrel, and run it against a file or a piece of sandpaper until you get it down to the right size.
Step 7: With your servo gears and top cover attached to the housing, thread your rod into the final drive gear from the inside. Continue to thread until you have a long enough section sticking out of the top that you can fit a nylock nut.
Step 8: Slide the following onto your threaded rod in this order: washer, servo horn, aluminum spacer, servo horn, washer, bearing, washer, nylock nut. Don't crank it down; you don't want any pressure on the servo housing. With all that installed, cut off the excess rod, then remove the assembled spool from the servo. Mark the position of each servo horn on the rod, then remove everything from the threaded rod.
Step 9: Place epoxy between the two lines you had previously marked on your threaded rod. Slide the aluminum spacer back onto the rod, with one servo horn on either side centered between the lines. Place epoxy between the mating faces of the spacer and the horns. Hold for a minute, then sit it down and walk away.
Wait until it cures before doing anything else. When you're done it should look like this:
Step 10: Drill a small hole through your aluminum spacer. This will be where you attach your winch line.
Step 11: Reassemble the spool assembly. The short section should go washer-bearing-washer-nut. A single washer goes onto the other end.
Step 12: Thread your assembly back into the final drive gear. (I put a touch of blue Loctite into the threads at top of the gear.) Tighten until the washer just
barely contacts the servo housing. Put the nut onto the other end.
Step 13: Tie your winch line through the hole, and wind it up.
Step 14: Reinstall the bottom cover, and you're finished.
Results: This winch rocks! Its easily strong enough to pull the truck straight into the air without stalling. (although - to be fair - it does struggle
just a little bit when doing that.) The epoxy has held up great, and I have to break my winch line. "thumbsup"
Total cost was ~$30
Servo - $11
ESC - $14
Hardware - $3
Notes:
The hole for the bottom cover was slightly off center, so I had to enlarge it to fix that. I put some epoxy to shrink the hole closer to the bearing diameter. I then put a small length of heat shrink tubing around the outside of the bearing to give it a snug fit.
My winch line is old yoyo string. It is strong enough to do what it needs to do, but I'd like to find something with a smaller diameter so I can fit more on the spool.
I used an 8mm wide spacer so it would wind slightly more quickly at the expense of a small amount of torque and a smaller line length capacity. You could easily substitute a 6mm if desired.
I haven't worked out all the bugs with my controller system, chief of which is the fact that the 20A micro ESC I'm using is limited to 7.4V, and I used 3S batteries. For the time being I'm running the winch off of its own 180mAh 2S lipo, which I velcro to the side of the servo housing.
Next up: Get a nice scale winch hook and some tow hooks for my bumpers, plus a dirt anchor.
Its my attempt at a shameless copy of the KMS K3. I really like the way they look, but I can't personally justify that kind of money on a winch. I have more fun making things than buying them anyway. 
