Robust way to rotate an 18 inch square plate 90 degrees.

In general, what would be the most robust way to internally rotate a plate from horizontal to vertical (hinged on the bottom) that when in a vertical orientation is 18"(h) x 18"(w) x 3"(d).
We have researched cams, linkages, pulleys, acme screws, etc and are wondering what you think the most robust method of rotating a plate would be with very limited resources and no machining capabilities.
Thank you, so much for your time.

Have you looked in to air?

Pneumatics are good they just may take up to much space.

Otherwise I’d look into using either a window motor / 775 pro with a 100:1 ratio connected to a through shaft
and supported by bearings on either side

Yes. air is good, but without a pneumatic specialist we are going to pass on that his year. Thanks for the motor/gear suggestion.
Is the trough shaft a long, screw drive?
What kind of bearing system would mount onto the plate?
(We are trying something new and really appreciate the help, thank you.)

One option would be to attach the plate to a shaft and then use a motor with a large reduction to rotate the shaft, rotating the plate. Another option is to put the plate on hinges and attach spring to the end so the plate is always being pulled one direction. Then attach a rope to the end of the plate and use a winch system to pull in the rope, pulling back the springs and rotating the plate. There are plenty of other options, those are the ones that came to me off the top of my head.

Numerous teams have pinned chain to the perimeter of a place and driven that chain with a sprocket/motor. Usually supported by a lazy susan of some sort.

Yea, this setup is pretty cool. It’s like 2 gears. With #35 chain the margin of error between the sprocket and the moving piece is huge.

Just my opinion, but you (personally) should become the pneumatic specialist. At a high level I feel that simple pneumatics are a lot easier than simple motors and shafts.

The first option is what I was referring to, and I’d use bearing blocks to support the shaft right after the motor and after it came off the other side of the plate.

Linkage driven by a window motor is a simple way to do this. Linkage is pinned to a disk that is rotating at the end of a shaft. This is the same linkage concept as translating rotational to linear movement. It is essentially two position.


And they are very addictive for a low resource team, more forgiving on the build, and easier to program, and less likely to self destruct when the programmers get a hold of it.

If you use a motor, when you raise it you want to hold it up… so motor runs into a stop, then what… turn the motor off, does it fall, stall the motor into a hard stop, does the motor burn up… we have been a successful low resource team, we use a lot of pneumatics. We have more resources now.

How much does this “plate” weigh? How much time are you willing for this process to take? These two numbers can tell you how much energy per move and power during the move you need. Once you know these, you can quickly eliminate actuators which are too small or way too big.

Also, it seems strange to call something 1/6 as thick as it is in the horizontal direction a plate; is it really that thick?

I would definitely use pneumatics for something like this. It’s mysterious, but once you make a little effort to understand it, it’s simple, and makes moving hinged things really simple. Best part…no machining required! you can make hinges with a drill and a bolt.

But you do need to be aware of the limitations of pneumatics. They mostly only work for things that need to be in either of two positions, not stopping in the middle. And the motor that powers the compressor is not very large, which means that you cannot get a lot of work out of the system…so use it for relatively small low force things. Don’t try to lift a robot with pneumatics! instead, use it to actuate things.

Weight with its load ~ 3 lbs (I estimate the CG arc will be about 12 inches from center )
The measurements are the overall volume, the actual plate is more like an “L” shape probably made out of 1/8 to 1/4 inch thick material. (don’t know yet, but I think the weight is correct either way).

Would like it to complete its 90 degree rotation in < 3 seconds (more like a slamming up action)

As an aside, who makes FRC compliant actuators, please? The one company I found last night said his motor wasn’t compliant.

Thank you.

Yes, I am seeing the great advantage for learning pneumatics!
Thank you so much for the extra tips and considerations.
I have put this in my off-season planner for learning and experimenting with. Right now, time is not available, though, so I am seeking an end-run through some combination of cams, linkages and levers that I can make out of plywood or the aluminum tubing on hand.

This sounds like a good job for a light pneumatics. If you need intermediate positions, look into a heavy duty servo or light motor (e.g. some flavor of PG) with sensor feedback.

The FIRST servo rules have relaxed significantly in 2017 (after a significant relaxation in 2016), so you may want to re evaluate the compliance yourself. IIRC, the only servo specific requirements this year apart from how you power and control it (R36) are that it have a retail value under $75 (R32).

Edit: When setting up pneumatics, you should make sure that your mounting gives you good leverage at your angles of greatest load. For lifting a plate/box around a horizontal hinge, the cylinder should be pushing (or, less optimally pulling) just about straight up at the bottom of the stroke, but can be at a relatively shallow angle (e.g. 30 degrees) at the top of the stroke, because the CoG isn’t rising very much there. Going the other way will require a much larger cylinder that will slam the plate to the top of the travel because it is overpowered there.

I guess my message didn’t get through! Pneumatics is simple. Really simple. Way simpler then levers, cams, linkage, motors, transmissions, belts, gears, etc.

Seriously…spend an hour, learn pneumatics, you will know all you need to know to make things move easily and quickly.

Thanks, I will. :slight_smile:

Thanks, I can see your suggestions. They make good sense.

Thank you for the encouragement. I am looking in to learning “air”.