Linear Actuator

Hi there,

I am building 2 pendulums for a theater production. Ideally they would be some 26 ft long. We made a test with an electric tube linear actuator incl. slide rail mounted to the ceiling and a hinged 10 ft aluminum tube attached to the rod/plunger of the actuator. The actuator was controlled by a simple DPDT relay.

The actuator used was Firingelli's high-speed actuator with the following specs:

Dynamic Force: 22 lb Static Force: 44 lb Speed ("/S): 4.5" (9" at no load) Current: 5A max Duty Cycle: 20% at 100% load, 50% at 25% of load Input: 12v DC Stroke: 10 in

See https://www.firgelliauto.com/products/high-speed-actuator

It works quite well as long as you make sure you don't go over the 20% duty cycle.

Once we tried out a 26 ft pendulum the stroke speed was unfortunately too slow to produce a significant pendulum swing.

We also tested a different model with similar specs from Progressive Automations with a 16 inch stroke which actually made the pendulum swing less (see - http://www.progressiveautomations.com/tubular-high-speed-linear-actuator)

My guess is that a higher speed and duty cycle would significantly improve the results. We've actually tried higher duty cycles up to 60% and achieved a much longer pendulum swing, at least for a while before the actuator burned out. Ouch!

Question to the forum: Do you know of an electric high speed actuators 4 in/sec or more, 22 lbs or more and a duty cycle 20% or (much) more?

I am aware that a pneumatic control would be much better but considering my deadline and the potential noise from a pneumatic actuator I try to stick to electric at this point.

Do you maybe know another forum outside of Arduino that might be able to help out?

Thank you for your help in advance!

Erwin

I wouldn't think it would take a lot of force to keep a pendulum swinging.

Can't you just nudge the pendulum line a bit once each period?

Can you give more detail about how the pendulums' pivots are connected and what sort of materials and are used in the construction. How heavy is the bob of the pendulum?

Thanks Duane for your reply!

The pendulum is swinging and yes, I can keep it going by nudging it periodically. I have to watch the duty cycle of the actuator, though...

Think about the pendulum going left-right-left-right... I have to nudge it left, then pick a right swing, a left swing, etc. You can't nudge at every left-right movement because the motor has to rest basically 80% of the time since it has a 20% duty cycle. I have to skip a couple of swings, then nudge again, skip, nudge, etc.

The problem is that with the long 26 ft pendulum the movement simply slows down very quickly and the set-up looks "weak" for lack of a better word. My solution would be to find an actuator with a higher duty cycle.

The pendulum arm is a 3/8 inch aluminum tube with DMX controlled lights at the bottom. The total weight is about 4 lbs. The pendulum pivots from a perpendicular rod mounted to the tube. The system has minimal friction...

Erwin

Do not double post.