Angular Force Required 7

[Foxhole]

Hi all,

I am new here and was hoping that someone would be able to help me with a problem that you will probably find simple.

Looking at the image, how would I go about calculating the force required to equal the applied load?

I am struggling to get my head around calculating angular forces!

Thank you in advance for your help,

Regards,

Adam

 

[renderu]

http://www.imgur.com/tilAUrC.jpeg

 

[renderu]

That was just sum of forces equal zero in the vertical direction. Sorry for the confusion witb the wrong title.

 

[Foxhole]

Thanks for your help Renderu, much appreciated,

I wasn't too far off the right line then, but doesn't the 0.25 mtr moment further increase the force required?

 

[renderu]

Sorry. I'm at work and messed that all up. You need moment around hinge. I'll send update very shortly.

 

[Foxhole]

Thanks mate, really appreciate your help

 

[renderu]

Is the cylinder end inline with hinge? Doesn't look like it. What's that offset distance?

What did you mean by mtr moment?

 

[renderu]

http://www.imgur.com/TqVA0AD.jpeg

This assumes it's inline. Also neglets the weight of the structure.

 

[Foxhole]

Your right, it isn't completely inline, the cylinder end is 12.5mm higher than the hinge point,

I mean't 0.25 metre distance horizontally from hinge point to cylinder end, sorry I'm probably not using the correct terminology.

 

[Foxhole]

It is almost inline so that is fine, that was the figure I was coming out with basically as per your first calculation multiplied by the moment around the hinge.

Great clarification though, as I don't really do many of these calculations very often I have gotten really rusty with it.

Thanks again for your help,

Adam

 

[renderu]

This includes the offset:

http://www.imgur.com/fzginfI.jpeg

 

[Foxhole]

Brilliant info, thanks again

 

[dhengr]

Foxhole:
To completely define the problem you have to add vert. dimensions from some datum, say the top of the deck plate, down to the hinge pin center and to the two pin centers on the hydraulic cylinder. Then think of it this way: the gravity loads always act vertically and the lever arm to them, the point load and/or the dead load of the machine is horiz. or perpendicular to their line of action; the lever arm btwn. the cylinder and the hinge pin is always the perpendicular distance from the hinge pin to the center line axis of the cylinder. This is a kinematics problem, and you see that the lever arm to the cylinder is increasing, while the lever arms to the loads are decreasing, with any lifting rotation. So, your sketch shows the highest cylinder force. You do not want the cylinder axis to get much closer to the hinge pin or you will have an unstable system which could experience snap through. So, provide a solid stop under the platform so it can’t go below the horiz. position shown.

 

[IFRs]

This can be solved quite easily with a scale.
First get the vertical reaction at the left end of the piston using the ratio of lever arms ( 1000 / 250 )
Then find the lengths of the legs of a right triangle formed by the piston's two ends.
The vertical force is proportional to the length of the vertical leg of this triangle.
The force in the piston is proportional to the diagonal length of this triangle.
Note that the sine in the previous answer is the opposite over the hypotenuse which is the same as the vertical side of the triangle divided by the diagonal length, so the answers come out the same.

 

[Cockroach]

5141 N at 11 degrees.

Nobody ever answers the question in this forum, just hand waiving arguments.

Regards,
Cockroach

 

[IFRs]

We teach fishing

 

[dhengr]

Dave:
Very nice, that says it all.

 

[dvd]

Before getting really serious about your solution, you should investigate the motion and look at the cylinder you have drawn. The cylinder looks like it has been cartooned in, and does not reflect actual cylinder dimensions.

 

[Walterke]

I'm just going to give the OP a star for providing a proper drawing & explanation of his problem. This is more rare then it should be.

NX 7.5.5.4 with Teamcenter 8 on win7 64
Intel Xeon @3.2GHz
8GB RAM
Nvidia Quadro 2000

 

[zekeman]

"Cockroach (Mechanical)
11 Mar 13 15:08
5141 N at 11 degrees.

Nobody ever answers the question in this forum, just hand waiving arguments"


Now, now, Cockroach, give the guy a break.
He gave enough geometry to do the problem, notwithstanding some poor nomenclature.
Compared to most other posters, the guy deserves an A.