Motorized rotating platform (180 degrees, periodically)

[hansyhop]

Hi,

I'm trying to build a motorized rotating platform, and was wondering what drive system to choose.

The platform is 1.2 meters in diameter with two cylindrical objects (max 25 kg each) attached on top - total weight to rotate approx 80 kg. I want the platform to be programmed to periodically rotate 180 degrees, (for example every 3 hours), so that the two cylindrical objects switch position. It needs to be precise.

My current solution is to have four wheel supports under the platform and one center support with bearing. Then have a stepper motor with a drive wheel connecting under the platform, rotating it by friction. What I was wondering with this solution is if the platform will stop precisely enough, and not continue to rotate some degrees over 180. The rotational switch does not need to be very fast, approx 5-10 RPM.

I was wondering if anyone here had a clever input on this problem and how to calculate the needed torque to rotate the platform (inertia, friction etc.?) and which stepper motor or other types of motors, with transfer is recommended?

If you need more data, just ask!
HOP

 

[berkeman]

Hi,

I'm trying to build a motorized rotating platform, and was wondering what drive system to choose.

The platform is 1.2 meters in diameter with two cylindrical objects (max 25 kg each) attached on top - total weight to rotate approx 80 kg. I want the platform to be programmed to periodically rotate 180 degrees, (for example every 3 hours), so that the two cylindrical objects switch position. It needs to be precise.

My current solution is to have four wheel supports under the platform and one center support with bearing. Then have a stepper motor with a drive wheel connecting under the platform, rotating it by friction. What I was wondering with this solution is if the platform will stop precisely enough, and not continue to rotate some degrees over 180. The rotational switch does not need to be very fast, approx 5-10 RPM.

I was wondering if anyone here had a clever input on this problem and how to calculate the needed torque to rotate the platform (inertia, friction etc.?) and which stepper motor or other types of motors, with transfer is recommended?

If you need more data, just ask!
HOP

Welcome to the PF.

What angular accuracy do you want to achieve? What are you going to be driving the stage with? Would position feedback on the angular position be helpful?

 

[hansyhop]

Welcome to the PF.

What angular accuracy do you want to achieve? What are you going to be driving the stage with? Would position feedback on the angular position be helpful?

Hi!

The final solution would probably be an off-the-shelf rotation stage driving the platform from the center, since they are very accurate. Then I would maybe not need the supports ether.

As a prototype, I was thinking about the solution explained in first post. A (stepper) motor, running a drive wheel. I have no experience with this and how accurate I can have them, especially when its a drive wheel that transfers energy to the platform and how accurate it will stop. I am open for other solutions too.