How to customize a servo?

[moneybagsfor-rc]

@Bondonutz - thanks, but I would need it to be via receiver for remote operation

@BrianG - I did not know that about the third channel. Do you know any with 3 positions?

@coolhandcountry - It's for a semi automatic 7 speed transmission (doing it just for fun). It's the same concept as the E-Maxx transmission with the paddle shift, however since there are more than two speeds there will need to be 3 "paddles" and thus three forks to shift in and out of gears. The key design is the ratcheting drum that would sit just outside of the transmission. This drum is basically a cylinder with slots etched with a helix-type engraving that guides the shifting forks as you spin the drum. For my current and rough design of the ratcheting drum it requires a 1/4 to guide the shifting fork from one speed to another.

@JThiessen - where can I find robot guys?

[BrianG]

Originally Posted by moneybagsfor-rc

...@BrianG - I did not know that about the third channel. Do you know any with 3 positions?...

Most radios I've seen use a simple switch for CH3 and is usually 2 position. However, the Spektrum DX3r (and I only say this model because I have it and know it can do this) is able to set this switch to be a 2 position, 3 position (forward, back, and center), or linear (makes the servo move the longer you hold the button) settings. The switch is not a toggle, but rather a slide type that is momentary (returns to center when you let go).

Whether or not your particular radio has that level of CH3 functionality is up to you to figure out. But I have a feeling you will need a channel that operates more like the throttle or steering. Meaning; the servo moves in proportion to the wheel/trigger position. CH3 on the DX3r is more "software" driven rather than mechanical like the steering/throttle. Then, do like I describe above and replace the trigger/wheel with a rotary switch that has specifically chosen resistors. This would make it so that each position of the rotary switch would move the servo a set amount. The resistors needed would depend on the existing pot's value and some trial and error, not to mention you wouldn't have much tweakability (EPA and trim) other than playing with those resistor values to get the servo to move right.

Since I assume you need your current steering and throttle controls for their intended purpose, I think you'll need a stick radio so you have more channels to play with: one stick can be throttle/steering, the other can be the modified channel for your tranny.

I know you say this is for fun, but after you get it all working, I wonder if the complexity and weight of the final product will be more work than it's worth.