Simple question - accuator selection

[FullMetalBracket]

This is most likely a ridiculously simple question and I'm somewhat embarassed to ask it, but it's my first time performing such a calculation so cut me some slack...

I've been asked to select a linear actuator that will act on a 'beam' which is pinned on one end. The actuator pushes about halfway between the CG of the beam and the pinned support (not really relevant to my question). If I make a conservative guess for coefficients of friction, determining the required actuator force to begin motion requires solving a simple FBD. However, the actuator will obviously need to push harder than this value to actually accelerate the beam.

Actual speed here is not really critical, so what value to I attribute to this angular acceleration to determine maximum required actuator force? Am I going about this calculation completely the wrong way?

Any guidance is appreciated. Thanks!

 

[plasgears]

The force to move the mechanism includes inertia and friction forces and any other connected loads thru the beam. The actuator will see a proportionately larger load than if it were connected directly to the CG location.

 

[hydtools]

The actuator must push with any force greater than the force required for equillibrium in order for motion to occur. How much greater the force will determine the resulting motion kinematics.

Ted

 

[MintJulep]

Since your probably making guesses about static and dynamic friction anyway this is all pretty much approximation anyway.

Solve for the force that your need to overcome static friction and start things moving.

Solve for the force that you need to overcome dynamic friction and keep things moving.

Select an actuator with "enough" force.

The extra force will result in acceleration. Solve for the acceleration and velocity profile. If the resultant acceleration and velocity is acceptable then you're done. If not select a different actuator and start again.