So I have this project that requires this jig. The problem will be easy to figure out, I just don't know what calculation to use. At first I thought it was a torque calculation, but that isn't correct. It's some form of a lever calculation. What I need to know is the Lbs (pounds) or pressure at Point A. Here's the layout:




- 30 lbs of weight 12 inches from pivot point.
- Point A is 10 inches from pivot point.

I'm thinking 36 Lbs. (L1/L2)*30=

Edit: You actually probably need the center point of the 30 Lbs weight as the right end of L1 though.

What type of calculation is that? Some type of lever formula?

I'd say it's a lever formula, the fulcrum being above point A and the distance being however far the 30lb mass extends. You'll calculate a torque, then convert that to a force (pounds).

I don't see that the pivot plays into it nor anything before it if the A horizontal component is rigidly attached to the horizontal component.

Also, if you need the pressure, you'll have to know the area of the contact between the horizontal component and the base.

edit:

Here you go:
http://www.calculatoredge.com/new/torque.htm

edit 2: It might help with more information though, like where are the rigid connections. Is the point of the whole contraption driving the the horizontal member into the base with a certain amount of force?

edit 3 (last one, I promise): I think the problem is maybe we're mixing static and dynamic systems. Is this supposed to move, or just hold something up (or clamp something)?

It's static so you only have to evaluate the pressure with the rotating arm in that position. As the arm rotates the problem gets more complicated. It is a torque problem of sorts because the mass on the end of the lever provides a force down constrained by a pivoting arm. The resulting force up at a different point on the arm would have to produce an equal and opposite torque to be zero net torque.

Torque due to weight = Tw = Fw x L1
Torque due to stick = Ts = Fs x L2

We see because L2 < L1 that Fs > Fw. This is the classic nutcracker situation that force is multiplied by being closer to the pivot point. The pressure requires knowing the area of the bottom of the stick which isn't given. It would be the force divided by the area.

Fs = Fw x L1/L2

In this case the 30 lb weight gives a force on the stick of 36 lbs.

Yeah Fred and Cyber have it. It's static force. Just needed to know how much weight Point A would be applying. Appreciate the info guys!