Are Servos Considered Electric Motors?

[Calvin_1631]

The standard HITEC HS-322HD Servo that comes in the KOP does not seems to have enough torque for what we need it to do... So we want to but a servo such as this one: http://www.servocity.com/html/hs-75bb_retract.html

However, reading <R46>, it says we can not use electric motors other than those in the KOP. So is a servo an electric motor or just a servo motor? I can't expect FIRST to be that crazy and not let us use other servos.

Thanks in advance!

[Dave Flowerday]

Originally Posted by Calvin_1631

However, reading <R46>, it says we can not use electric motors other than those in the KOP. So is a servo an electric motor or just a servo motor?

A servo is simply a motor with feedback built in. You may only use additional Hitec HS-322HD servos per <R46>. Other servos would not be permitted.

[AdamHeard]

If you are alright with shortening the throw of the servo, you can increase the torque of the kit servo. This may solve your problem.

[Brad Voracek]

Originally Posted by AdamHeard

If you are alright with shortening the throw of the servo, you can increase the torque of the kit servo. This may solve your problem.

Hmm, could you explain to me how this would work? I'm not following. Could solve a lot of problems.

[MrForbes]

I think what he meant was that if your design will work ok with reducing the travel of the mechanism attatched to the servo by moving it closer in on the servo arm, you can get more force out of it.

You can't increase the torque of the servo.

[AustinSchuh]

Use lever arms, and a linkage. Put one of the lever arm arms on the servo. Set up an axle with a lever arm on it also. Figure out the length of the lever arm on the axle such that 180 degrees of motion on the servo moves the lever arm on the axle 90 degrees. Those 90 degrees should be centered in such a way that when the servo arm is at 1/2 of it's turn, the axle will be at half of it's turn.
Now for BAD ascii art.

         Linkage Linkage Linkage
         l                     |
         l                     |
         l                     |
         l               |Servo Servo Servo|
         l               |Servo Servo Servo|
         l               |Servo Servo Servo|
       Axle
       Axle

In this diagram, since the servo arm is shorter than the output arm, it will move the "Linkage Linkage Linkage" near(I didn't do any calculations for my bad art) 90 degrees for 180 degrees of servo motion.

Also just thinking out loud, Could you possibly use two servos. You could place the servos on opposite sides of the mechanism, and after writing some code to reverse the pwm values, you would have two servos, and therefore double the torque, working on actuating one mechanism.

Good luck. If this does not make sense, ask again, and I bet someone can draw a better* diagram.

*Not ascii art

[AdamHeard]

Yeah. A linkage was what I meant, not literally chaning the torque outputted by the servo.

The best example you can work off of is the camera mount. Look at the linkage on there when you get a chance. If you change the length of the arms, the amount of end rotation changes. If you change the servos ~ 160 degree into ~80 degrees, the torque is doubled.

What and where are you trying to do this, it may be more effective to use a globe or window motor.

[Andy A.]

To add to the consensus, servos are considered servos, and you may use them so long as they are identical to those in the kit and unmodified. They are however powered by the 7.2 volt back up battery, so if you do use them extensively make sure to keep that battery charged up.

The no modification part means no continuous rotation mod, unfortunately. If we could do that, I'm sure some team would have long since ganged a bunch together to squeeze just a little bit more wattage out of a drive system.

-Andy A.