How to messure Leverage, Leverforce in Creo Mechanism

[MA_9965308]

Hello,

is it possible to measure the lever force over time in Mechnism dynamics?
I have a simple lever mounted in the middle. On one side it is moved with a hydraulic cylinder.I know the displacement and the force in the cylinder. I would like to define these parameters. The vertical force that acts on the other side of the lever, I would like to show over the cylinder length or the time.

Is this possible? Unfortunately I did not find anything in the help.

Greetings
Morian

[tbraxton]

Yes, it is possible. See the below link for the measures available in Mechansim. To investigate results in the time domain you will need to define a force motor to represent the hydraulic force applied as a function of time. This could be a constant force or vary with time.

https://support.ptc.com/help/creo/creo_pma/usascii/index.html#page/simulate/mech_des/measures/about_meas_results.html 

Application of a motor in Mechanism:

http://support.ptc.com/help/creo/creo_pma/usascii/index.html#page/simulate/mech_des/motors/To_Define_a_Motor.html 

[MA_9965308]

Thank you for the fast reply @tbraxton 

Could you help me with some more details? I defined an force motor and rund an analysis. But which analysis ist the correct one? I think, that i need an dynamic analysis, because by using force balance i get only the force for one situation. Am I right with this? 

Which categorie do i chose, if i want to show the lever force in an Graph.

I would be very thankfull for any futher information.
Greeting 
Morian

[tbraxton]

If the results vary with time then you will use a Dynamic analysis. Without a free body diagram I am not clear on what you are trying to measure.

You can measure the reaction force at a mechanism connection or the net load on the force motor.

To Create Connection Reaction Measures (ptc.com)

 https://support.ptc.com/help/creo/creo_pma/usascii/index.html#page/simulate/mech_des/measures/net_load_measure.html 

[MA_9965308]

sorry,
I should have attached a picture at the beginning.

Now I got one. I want to define the green cylinder force and measure the vertical red lever force. The cylinder has a stroke of 200 mm.  I want to display the lever force over the time or over the stroke.

I want to know how much I can lift in each position. On a paper, this is not a problem with this simplified design. But in Creo I don't know how to do it yet.
Is it now understandable?

Greeting 
Morian

[tbraxton]

One option is to measure the torque at the pivot pin joint where force motor is applied. This will enable the derivation of the force at the location you want to solve for.

[MA_9965308]

Thanks for your help, but I'm not comfortable with this solution. I have one that is probably just a little more convenient. I have added a circle to the assembly that is placed at the pivot point of the lever. I connect the circle with a guide connection to the pivot point where I want to know the force. At this connection I can define a motor. With the static force at the cylinder I can measure the connection force of my motor. 
But this solution works only if I know the path of the movement point. Im sure there is still  a better way to measure the force.

Regards Morian

[MK_9183946]

Hey Morian,

did you find any better solution to your case? i am stuck with the same situation problem, still trying to figure out if it works or not

any ideas?

regards

Markus

[SweetPeasHub · Accepted solution]

Use a large damper to make the simulation quasi-static.

This is a solution for finding a series of static balance forces along a change in configuration for any mechanism.

To do this you need to use a quasi-static style of analysis. If you add a large damper as shown with long simulation time duration so inertia effects are negligible, you can get the force out vs cylinder extension. This is still a dynamic analysis requiring mechanism dynamics extension.

A constant force motor was applied at the cylinder and the net load measured at the damper.

If concerned that the damper force is not pure Y direction, you could also reverse those and have a constant downward force at the output and the damper at the cylinder.  Or you could just send the bottom attachment of the damper down significantly in Y.

This seems simple enough but I believe this is a better answer to several similar questions in the community and it just popped into my mind today and I thought how dumb I was not to think of this yet!  😀  Thanks for reviving this question! I have Creo 10 models if you like a model.

[MK_9183946]

Hey there,

that sounds like a reasonable plan!

many thanks for the hint I will try it out one I am back from vacation next week

if you have some models please share 🙂

probably adding additional planar joint to the anchor point could help in only getting true y forces?!

i need to test it but I am more than happy with your reply

many thanks

Markus