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-   -   Robust way to rotate an 18 inch square plate 90 degrees. (http://www.chiefdelphi.com/forums/showthread.php?t=153758)

GeeTwo 17-01-2017 11:36

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

Originally Posted by paul.dornfeld (Post 1632342)
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 https://www.servocity.com said his motor wasn't compliant.

Thank you.

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.

MrForbes 17-01-2017 11:37

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

paul.dornfeld 17-01-2017 11:57

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

Originally Posted by MrForbes (Post 1632354)
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. :)

paul.dornfeld 17-01-2017 11:58

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

Originally Posted by GeeTwo (Post 1632353)
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.

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

paul.dornfeld 17-01-2017 12:01

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

Originally Posted by tr6scott (Post 1632012)
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.

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

Skyehawk 17-01-2017 12:22

Re: Robust way to rotate an 18 inch square plate 90 degrees.
 
A pneumatic system is defiantly the way to go, one piece of advice that is relevant for most mechanical sub-assemblies, is try to reduce the amount of work an actuator has to do. This is especially relevant for heavier loads (i.e. 10 lbs). Use latex tubing, springs (make sure you wire them!) and gas springs to help reduce the experienced weight on an actuator, and torque/power required. Not only will this technique cut down on wear and tear, but it adds some level of finer control. Just be careful with large preloads! ::ouch::

paul.dornfeld 17-01-2017 13:35

Re: Robust way to rotate an 18 inch square plate 90 degrees.
 
Thanks for the great tips. Really appreciate it.


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