Can I reverse polarity on a Servo??

[savagefromthesprings]

I have an HPI CK. Moved my front steering servo to the axle. Now I made brackets for the rear axle and mounted a second servo. My trans/receiver doesnt support a third channel, so I spliced the two servos together..

What I was hoping for was the rear wheels to turn opposing to the fronts (for tighter turning radius). Well, it didnt quite work out that way.. Is it possible to reverse the polarity on the rear servo to make it oppose the front? Is it as simple as switching a wire around (like switching polarity on a subwoofer), or will this burn up my servos/receiver etc..

Thanks for any advice!

[Spiftacu1ar]

you can't jsut switch wires in the cable going to the reciever. You need to open up the servo, and itch the leads going to the motor itself. OR, you can put a few bucks down and get a y'splitter that also switcehd direction. Someone had a link to that in anotehr thread. I frogot what its called.

[clockworks]

You can buy a Y lead with a built-in reverser for one of the servos. Google "servo reverser".

Spif: Have you tried reversing the motor wires yourself? I'd've thought that the servo would get very confused with the motor going one way, but the feedback pot going the other way.

[savagefromthesprings]

well that sucks.. I wanted to crawl tomo, but I guess its gonna have to wait till I get a splitter.. So, opening up the servo, what do I switch around?

[Biscuit]

I wouldnt open up the servo and try to change the wires. Would be much more simple and pretty cheap just to get the reversing Y cable and use it. Plus that way if you ever need to use the servo on something else you can with-out having to change it back.

[Dr.Frank]

Just turn the servo about 180° and it shoukld work

Greetings Frank

[clockworks]

Originally Posted by Dr.Frank

Just turn the servo about 180° and it shoukld work

Greetings Frank

I don't think that will work, certainly not just if you flip it.
It would work if you had the servo facing forwards (horn to the front), but it would need a totally new and complicated mounting. It'd also be vulnerable to damage, sticking out between the wheels.

Something that would work, if there's enough clearance, is to fit the horn pointing up, rather than down. You'd need a longer steering link.

Another alternative would be to convert the front steering to "behind the axle".


Going back to Spif's idea of reversing the motor wires, if you also reversed the wires going to the pot, it would work fine.
Reversing the motor wires is easy enough, once the servo has been stripped, as the wires are soldered to the PCB. Just unsolder them and re-solder the other way around.
Swapping the pot wires is a bid harder. You need to cut the solder tracks going to the 2 outside connections, then add 2 wire links to reverse them

[savagefromthesprings]

got it! mounted a short arm on the servo facing upward. That reversed the direction of the wheels. So, instead of the arm moving in the same direction of the wheels, with the arm facing up, it reversed the direction.. gonna take some pics and post them.. Nothing fancy. I dont have any tools to work with (travelling in an RV), so its just a basic setup.

[savagefromthesprings]

4 wheel steering didnt cost me a dollar. Servo was a spare one in my box of junk. Made the brackets out of a scrap piece of plastic. Turns on a dime now!

[Spiftacu1ar]

Originally Posted by clockworks

You can buy a Y lead with a built-in reverser for one of the servos. Google "servo reverser".

Spif: Have you tried reversing the motor wires yourself? I'd've thought that the servo would get very confused with the motor going one way, but the feedback pot going the other way.

You'd also have to switch the wires from the pot, lol. Forgot to mention that. But no, I have not done it myself.

B/c of the way a pot works, switching the two outer wires on it (the center is a common), will essentially switch the diretion.

Again, no I have not doen it myself. Before undertaking such amod, I would serach the forums, as there is a probably a fuill guide. If not, you could make a new thread.

But, you got it all foguired out, so I guess that's no necceasry :P

[JohnRobHolmes]

It is easy to mod the servo. Swap the motor leads, and swap the outside two pot leads. Otherwise you could mount the linkage above the servo instead of below. Clockwise rotation becomes an opposite push that way, although linkage angles are not the best. See the WK pics above, you can see that the rear servo has the arm facing up.

[savagefromthesprings]

Originally Posted by JohnRobHolmes

See the WK pics above,

Crawler King. It was a RTR model.