Barrel Cam (Linear motion to Rotational)

[damica1]

Has anybody see a real world device like this that could be purchased?

https://www.youtube.com/watch?v=vRnCQUViFRc

I'm wanting to convert the Up & Down movement of an "Oilfiled Pumpjack" to a single RPM for each stroke.

Thanks

 

[jaden]

I used to work with printing presses. A similar mechanism would oscillate an ink roller to ensure even coverage. However, couldn't you directly sense rotation using a proximity sensor and a flag on the drive shaft?

 

[drbitboy]

One way to convert linear motion to rotational requires is a crank. The yellow barrel cam in that video is driving the blue rod, not the other way around; I don't think the linear motion of the blue pieces can drive the yellow piece through the point where the groove is tangent to a plane perpendicular to the axes, at least not without a significant flywheel (momentum) to get over that deadspot. That said, a single-crank system requires a flywheel as well.

 

[TheWaterboy]

Such a mechanism is idealized, in that design or a crank style, you will have an on-center situation to deal with at each end of the stroke. It can either stall or revers direction at the center position. Even with a flywheel to carry it over the potential is still there.

You must intend to drive another mechanical device from this ?

 

[chelton]

A wire rope and a sheave would probably be much easier to implement.

 

[ndzied1]

I'm wanting to convert the Up & Down movement of an "Oilfiled Pumpjack" to a single RPM for each stroke.

Thanks

That is exactly the reverse of how a pump jack operates. Watch these videos. The rotary motion plus the mechanism is what gives the pump jack the up and down motion.

https://youtu.be/sccZ3RE-9YA

 

[damica1]

That is exactly the reverse of how a pump jack operates.

https://youtu.be/sccZ3RE-9YA

That is correct!

I want to put a "Rotary Encoder" on the rotating shaft so that I can know at what "Degree" the the unit is in within it's "Up/Down" cycle.

 

[drbitboy]

That is correct!

I want to put a "Rotary Encoder" on the rotating shaft so that I can know at what "Degree" the the unit is in within it's "Up/Down" cycle.

Ah, we have a miscommunication: you don't want to convert the linear motion to rotational motion, you want to measure the rotational position and then convert that knowledge to knowledge of the the linear position of the other side.


What is your target resolution i.e. how many unique measurements per cycle? What is the target accuracy? What is the period of one rotation? What PLC are you using?

 

[Cetronic]

I have used a Kuebler encoder which produces a 4-20ma signal over a 360deg single rotation maybe this will assist. Google Kuebler encoders will produce info.

 

[_Dock_]

Why couldn’t you just scale an absolute single turn encoder?

 

[Peter Nachtwey]

This looks like a mechanical non-linear gearing problem.

We, our customers, do that sort of thing all the time electronically. We can measure the rotational position, angular velocity and acceleration rate and use a non-linear function and its derivatives to compute the linear position, velocity and acceleration.
Do you remember the chain rule?

 

[damica1]

Thanks, all this gets me thinking in various direction.