Crawler Tech: How to Build a Winch
 

Hopefully this will get put up on the tech article page soon but for now I am posting it cuz I've had so many people ask me about it. Sorry it took so long. Once this is on the tech page I may delete this thread but ask any questions you have. 8)

With scale crawlers being as cool as they are it is only natural to have a winch to get you through those tough spots. I have used several different servos and found that the Hobbico CS-70MG makes a great winch, it is cheap and plenty strong enough to pick up a 6.5lb rig. Another great servo to use is a Hitec HS-645MG or HS-525MG.
Before we begin let’s make sure you realize that you will need a radio with a three position switch to run the winch. My favorite is the Traxxas TQ3 with the 3rd channel modified for a 3-way toggle.

Begin by removing the servo horn, then the four screws on the back, and then remove the front cover. Lift out the center brass gear first and then remove the aluminum output gear. On the CS-70 (and some of the Hitecs) there is a small plastic insert in the backside of the output gear. I use a small allen wrench inserted through the screw hole to push the insert out. On the 525MG there is just a flat plastic piece that sits over the bushing. This is used to turn the pot in the servo to help it find center, we want the servo to turn forever (or at least until we center the winch control switch) so this piece is the first to go.

Next remove the pin in the front side of the output gear. I grab it with a pair of pliers and use a twisting/pulling method to get the pin out. An alternative is to cut it flush with a rotary tool; this method fine but just remember it can never go back to being a regular servo again unless you buy a new gear.

Now plug the servo into your receiver along with power, either from an RX pack or an ESC/battery. Set the winch control switch to the center position and turn on the radio (and the ESC). If you are lucky the servo motor will not be spinning but most likely it will be. Grab the pot adjuster (the needle nose plies in the picture are just for clarity purposes) and turn it until you find the point where the servo stops. It will be touchy but it’s there somewhere. Once you have found the “off” position, flip the switch on the radio to make sure the servo turns when you want it to. Skippy told me that a dab of CA will help keep the adjuster from drifting. I have not tried this before but it sounds like a good idea to me.

Now replace the gears, then the cover and tighten the cover screws. If you did not glue the adjuster pot in place be careful not to bump it or you will have to readjust it.

For a drum I just use a couple of round servo horns. If you use fishing line for your “cable”, string it through a couple holes and tie it off. Be sure to use a good strong line, I tried the stuff that came on one of my fishing reels and it broke all the time. I have had good luck with yellow twine from the hardware store. You can’t have as much line on your drum but it has never broken. To use the twine drill a hole in one of the servo horns close to the center. Pass the twine though as shown in the picture and tie a knot to secure it. Put this horn on the output of the servo, as this will be the one that takes the force when you are winching. Lay the second horn on top of the first so that there is a gap between the two and then install the servo horn screw. Your servo horn screw will just barely grab a couple threads when you install it so don’t over tighten it. If you can find a longer one use it, I used a spare from one of my Hitec 5945MG servos and it worked great; otherwise be sure and tighten the screw every once in a while. The outer horn will spin but that is ok, it is only there to hold the rolls of “cable”, remember, the inner horn takes the load.

After all this, check the servo to make sure the pot is still centered. If it drifts then use the 3rd channel trim screw on your radio to re-center it. The trim is located in the lower left corner of the radio on the backside, right next to one of the case screws. For a hook I use a small picture hanging hook, they work OK but they bend sometimes and don’t look very scale but they are cheap and easy to find. If you have the time and desire then make one yourself.

That’s it! Now install your winch and go tackle those impossible obstacles. Happy crawling.

Griz

Links:
Hobbico

Hitec

Nice write up. You might want to add a link to the servo you used. :)

i just did that to a 645 last keek, havent put it on my 2.2 yet

could you do this to a 1/4 scale servo?

Nice write up! I see a future in Techinical Writing or at least authoring instruction manuals that no one reads!!!

for mine, i did simmilar mod that you did to get the servo to turn all the way around, and then for a spool, i used a sewing thing that i found in the laundry room, it was metal, and it was wider so it allowed for more "wire" thatn your set up, and i also used a VERY small pully from the hobby shop and ran the main line back to the ruck so i could get more power out of it, but even slower return speed, but i could pull my pede up a tree.

good write up!

I'm sure you could. Every servo I have taken apart works on the same basic idea, there is some piece that makes the pot turn as the main gear turns. I don't own a 1/4 scale servo so I could not say for sure but I bet it could be done. You could pull out shrubbery with it I think. :shock: :lol

:lol:

Thanks for the comments everyone, I appreciate it.

I added the links Mike. 8)
Chafey, I would prefer to use the 645 because I have not yet found a replacement gear set for the CS-70. I stripped it when I used it for a steering servo and it is out of commission now. I just had the Hibbico laying around.

If you used fishing line on my spool you could prolly get 10 feet on there. The twine gives you about 2.5 feet but I also have a tow strap that I can use with the with line for more length. Sounds like yours works good too. Thanks 8)

Another option with the pot if you don't want to keep the servo around for another purpose is to just cut it down flush with the bearing or bushing it rides in, i did that with an old traxxas servo, works fine.

Yes, it is the same thing for a 1/4 servo. I bought a tower hobbies cheapo 1/4 (340oz/in) and turned it into a winch using the same steps you have listed. I used three starnds of 20lb test fishing line braided together and I could never manage to stall the winch

just done it with an old futaba to practice on, really well written and easy to follow, should look damn good on my 2.2 with the suprising shell i got lined up, lol, thanks man, it works a treat, what sort of torques required for an average clod crawler to get it shifting?

I made this hook for mine, I also made one for Badger, but can't find it. oops
http://www.nor-calrcrc.com/albums/album02/ace.sized.jpg
If anyone would like one let me know.

anyone know of a tech article on converting the Airtronics MX-3's 3rd channel to an on-off-on switch? They are just on-off from the factory, but I would like to use it to operate a winch. any ideas?

WELCOME TO THE 2.2 CLUB GLAD YOU COULD JOIN:mrgreen:


Hell of a tech artcle Grizz I now know what i need to do to build a winch.:mrgreen:


rckjeep- thats a sweet little hook you made there too.:mrgreen:

I used 50lb spiderwire (fishing line), it looks like synthetic winch line in 1/10 scale.

Nice writeup, my brother was just saying how something like this would be a cool addition to a rock crawler.

Hobbico CS-70MG at Towerhobbies

Thanks for the info Grizz. I didn't see this post back in October when you started it. Very useful with the images and detail.

I did one thing different. Instead of removing the pin, I just pushed it in so that it was flush with the top of the gear. So if I ever want to convert back, (say mid competition and I have no other spare to use), I can pop it open, push the pin back into position and be on my merry way. I only found this out because I was having a hard time getting the pin out :-P


-Sam

This should be a sticky.