How to get additional operation out of V5's limited motor count.

Sometimes a robot doesn’t need a precise and powerful V5 motor to raise and lower a turning foot from skyrise, a shifting transmission from sack attack, or a wench or tension release to help hang in starstruck. Sometimes you want a single motor to do more than just operate a single system. So that begs to ask… How can a robot power more than one output with a single motor?

One possibility is to use two rachet and pawls like in Team 1727’s video
to allow clockwise rotation to activate one ratchet, and counterclockwise to activate the other. So long as each subsystem operates such that only one motor direction is needed, it should be possible to have a single motor operate two subsystems, like a transmission and a pivot foot, or a one-way roller intake and a wench.

Since pneumatics are going the wayside, and vex still doesn’t have solenoids to manipulate small systems like catapult releases, what other methods are there of operating more than one action separately with only a single actuator?

You could use mechanisms where they are only powered in certain positions. For example, you have an exposed gear on the lift that meshes with a gear on the base powering another mechanism. So that mechanism only works when the lift is all the way down. You could also use lots of one-time actuations using rubber bands. You could also use field elements to activate certain things. Like I didn’t compete in Starstruck maybe there was a way to make the hanging pipe activate your tension releaser somehow

I like this topic overall, but I’m curious about this claim:

Did I miss an announcement? Without further information, I can’t imagine them eliminating pneumatics. In fact I would expect to see an update sometime in the future.

If pneumatics do go away, then I would expect to see something else like solenoids or smart servos replace some of their function.

As to other ways to activate multiple mechanisms from a single rotational power source, you can construct centrifugal auto shifting mechanisms which would power a different output shaft based on the rotational speed. I’ve done it for non-vex robotics applications in a couple of configurations. One was a governor-like (“balls-out”) drive which moved a gear on a shaft effectively shifting between output sets. Another was a friction drive mechanism allowing both forward and reverse while driving the motor in only one direction. (low speed was reverse, medium was dead-band neutral, medium high to high was forward.) Driving the motor in the reverse direction powered a different output shaft for PTO operation.

My mistake. Last I heard from the proposed ruleset for 2018-19, you can use pneumatics, but it reduces V5 motors from 8 to 6, which is significant.

That being said, @kypyro had a great idea of using a centrifugal governor. That could be used in conjunction with a ratchet-based directional output to allow swapping a single motor’s output between 4 separate axles to be switched between from a single input. Sounds excessive, but could lead to some creative single purpose active mechanisms.

You can also make an auto reversing linear actuator using chain, sprockets and a linear slide. Auto reversing means that once the linear slide reaches its travel limit in one direction, it reverses and travels in the opposite direction.

Drive the linear slide via ratchet with, say, the reverse motion of the motor. Use its various positions as a transmission shifter.

Then, drive another output shaft (again via ratchet) with the forward motion of the motor. With a long enough linear actuator, you could select nearly anything. This type of mechanism appears in some old mechanical and clockwork toys, though the self reversing selector is usually made with a self reversing lead screw. (The sort of lead screw you see on antique baitcasting reels.)

All these things are cool mechanisms, and can be interesting to build. I like doing it, but the time commitment is kinda crazy. So really, the best thing to do is buy more motors. They’re a great value, if time is worth anything.

And that’s how you can do a holonomic drive with a single motor. Not saying it’s worth the effort, just that it’s possible.

I’ve been really tempted to do that at some point, just for the challenge. But there are only so many hours in a day and a lot more in life to deal with.