Escapement Mechanism

[Bob_W]

I have been searching for some info that would help me understand how to model a clock escapement I will be machining. I can get the pallet to rock back and forth as it would be when controlled by a pendulum, but the problem I am having is with the escape wheel. The interaction between the pallets and teeth on the wheel should causeintermittent motion of the wheel. In a real clock a torque would be applied to the escape wheel and pendulum would be started in motion. As the pallets rock there will be a time when a tooth will push up on the angled portion of a pallet, providing an impulse to the pendulum. Once the end of that section is reached the escape wheel should immediately rotate until another tooth hits the surface of the opposite pallet and locks the wheel. The pendulum causes the pallets to rock back and forth repeating the process.

If I have the pallets rocking, is there a way to get the escape wheel to turn like there is a torque applied? In the picture below the escape wheel would turn CW when viewed from the top. As I am not that experienced in mechanism, nothing I have tried will work. Currently using WF2 and mechanism.

View attachment 4161

 

[Kaz Z06]

You can apply a force/torque motor to the rotational degree of freedom of the escape wheel's axis. Set the value equal to the torque the spring would provide in the real clock in the proper diretion. This should model the clock's mechanism very well.


Cheers

 

[wsylvester]

I remember reading this awhile back. to stage rotations. You can use a table for your servo.





http://www.eng-tips.com/viewthread.cfm?qid=185438&page=9

 

[Bob_W]

Thanks for the replies;

Kaz: I tried to apply a force motor to the wheel earlier but with no success That doesn't mean it won't work, it just means I probably don't know what I am doing because I have never used a force motor before. I thought that it should at least impart a rotation to the wheel but I never got any motion at all, so I assumed I didn't do it correctly and did some searching though my training manuals and PTC site and could find any help. Lot's of stuff on servo's but nothing much on force motors.

I will try again and see if I can get it to do something. I will try the mechanism with just the wheel and see if I can get it to do anything. I'll let you know how I make out.

wsylvester: I wondered about something like that for the wheel, but it seemed it would require me to know quite a bit of detail regarding the tooth size, spacings, pallet ramp angle, and other things not yet known. I was planning to use the simulation to verify some of the clearances and center to center distances so I could complete the design a little more easily. Generally this would be done hand and mechanical layouts but thought I would take the fast, high tech approach


Thanks;
Bob

 

[Bob_W]

I did try the force motor again but still could not get movement while doing a kinematic analysis. The force motor would move the escape wheel when doing a dynamic analysis, but that is not the type I need at this point. I haven't come up with any more ideas, so if anyone has done anything like this I would appreciate the assistance.


Thanks


Bob

 

[Kaz Z06]

Bob,


If your goal is to run a kinematic analysis, clearly a force/torque motor will not apply. You will need to use a servo motor and create a table to represent the exact motion required at each time step. Remember, kinematic analyses assume mass-less. force/torque-less systems. Essentially, you will be dictating when and by how much the escapement will rotate if you wish to make this work under a kinematic analysis.A torque motor used in a dynamic analysis will help you predict the actual mechanism performance based on the torque you provide to the escapement's rotation axis.


Chris