Kridifur

I had originally posted this in the Radio section in the Cars forum. But no responses yet:

I understand the concept of ARC, and that the servo will move at different speeds. But what does this entail into real-world performance?
Please explain positive and negative ARC, both on throttle and steering servos.
Please, anyone?

MHawker

My Feedback: (16)

I'm only guessing here, but could you be asking about "Exponential"? ARC over here in the plane world usually means "Almost Ready to Cover" which describes the planes condition.

Exponential is the abililty to change the movement of the servo relative to the sticks range of motion.

Futaba uses Negative Expo to slow a servo down during the middle of the stick travel and then speed up as it gets to the end. JR uses Positive to achieve the same result.

This basically "softens" the sensitivity of whatever surface (or wheels in a car) so that the servo is connected to. This is useful because it makes it more easy to keep stable a plane that is very sensitive to stick movements.

It's also somewhat personal. This means that some people like it and some people don't.

Mike

Lynx

Not sure what you're talking about Krid, servo's are pretty constant in their speed. What you may be talking about about is using oval shaped horns or complex control linkages? This will make servo motion non-linear (constant servo motion will result it a variable control surface movement) It's totally irrelevant if you have the ability to set up curves on that control input and can be minimized by using as simple a control linkage setup as possible.

Kridifur

Yeah that's it, on my Airtronics MX-3 I have settings for throttle and steering ARC (sorry I wasn't more in depth). Which according to the manual states basically what you said. I was just curious if it really makes a difference in cars, or if it was more of an aviation type thing. Thanks for the info.

JohnW

My Feedback: (6)

Expo... real world examples for cars.

Steering: Set the steering so that it is very precise around center (large TX movements = small servo movement, but only around center.) Better control for fast straight runs, yet you have a lot of turning for corners.

Throttle: Engine response is not linear. Most of the RPM change happens in the first 1/2 of the carb. Could set up a expo curve so throttle response is more linear so you have better control over low end.

Yes, it can make a diff. In the above examples, the car steering becomes more precise around center (just like you reduced your throws), but since it is Expo, you still have full lock to lock. Should help improve your steering. Better throttle control can't be a bad thing.

Positive-Negative expo... depends upon the radio maker on which way each goes. Don't know on airtronics... Maybe another airtronics owner can shed some light.

Kridifur

Monkeyboy!!
Thanks a lot bud, you hit the nail on the head.
That is exactly what I was looking for.
I dialed in the expo on the steering (yep, you're right huge difference) and am still experimenting with throttle.
Once again thanks for the info.