Physics Help Forum Triangle of Forces

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 Jul 31st 2017, 08:15 PM #1 Junior Member   Join Date: Jul 2017 Posts: 1 Triangle of Forces So I am still a beginner in Physics and work asked me today to calculate if a 63mm Bore Pneumatic Ram will do the required job. Anyway, so I know how to calculate the weight capacity the ram can handle if it is at a 90 deg angle however if the ram is on an angle then I am stuck. I need to get back to them today and as a part student, I am finding this hard. any help would be awesome It wont let me attach a image however, the ram is on a 65deg angle. the ram is connected on a surfaces level of 1008, connection 360 from the left end. the weight which it needs to support is 106kg.
 Jul 31st 2017, 09:45 PM #2 Senior Member   Join Date: Apr 2017 Posts: 134 so ...imagine the ram pushing up perpendicular...every meter the weight is raised , the ram is extended a meter ... now angle the ram , every meter the load is raised vertically , the ram has extended more than a meter ... this makes it easier on the ram , it can now raise a heavier load ... if the ram is sloped 60*to the vertical , and the load is only allowed to move vertically then every meter the load is raised the ram is extended 2 meters ... so ram only needs to push half as much , a one tonne ram could raise a 2 tonne load Cos the angle angle of ram 60 to vertical ...cos 60 =0.5 ... a half tonne ram could lift a 1 tonne load angle of ram 30 to vertical ...cos 30=0.866 ... a 0.866tonne ram could raise a 1 tonne load angle of ram 0 to vertical ....cos 0 =1 ... a one tonne ram can raise a 1 tonne load
Aug 1st 2017, 03:08 AM   #3
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Location: Somerset, England
Posts: 688
 Originally Posted by oz93666 so ...imagine the ram pushing up perpendicular...every meter the weight is raised , the ram is extended a meter ... now angle the ram , every meter the load is raised vertically , the ram has extended more than a meter ... this makes it easier on the ram , it can now raise a heavier load ... if the ram is sloped 60*to the vertical , and the load is only allowed to move vertically then every meter the load is raised the ram is extended 2 meters ... so ram only needs to push half as much , a one tonne ram could raise a 2 tonne load Cos the angle angle of ram 60 to vertical ...cos 60 =0.5 ... a half tonne ram could lift a 1 tonne load angle of ram 30 to vertical ...cos 30=0.866 ... a 0.866tonne ram could raise a 1 tonne load angle of ram 0 to vertical ....cos 0 =1 ... a one tonne ram can raise a 1 tonne load
I particularly chuckled at the last one.

A 1 tonne ram acting horizontally can raise a 1 tonne load vertically.

No way.

Welcome to the forum, Anne.

Firstly never be afraid to ask if you don't know.
Don't guess.

Your ram will have specified maximum and working pressures.

The axial force F exerted by the ram is the product of the piston (bore) area and the pressure.

F = A x P

The pressure developed is only what is needed to lift the given weight, up to the maximum allowed.

You have said that the ram axis is set at 65, but omitted to say whether this is with respect to the horizontal or vertical.

The force exerted by the ram in any direction is given by the formula

force in a specific direction, f = axial force F times cosine of the angle between that direction and the ram axis, a.

f = F cos(a)

This force must be equal to or slightly larger than the weight to be lifted.

So in your case, if 65 is to the horizontal then angle a to the vertical is 25.

One more thing, your weight is 106 kg, which is a unit of mass not force.
The weight is the gravitational force exerted by the Earth on this mass and is equal to 106 times the gravitational constant which is 9.81.
This force is measured in Newtons.

So you have

F x cos(25) = 106 x 9.81

or

F = (106 * 9.81) / cos25

and P is F/A = (106 * 9.81) / A *cos25

Note that the diameter may need converting to metres to get the pressure units correct.

Aug 1st 2017, 03:18 AM   #4
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 Originally Posted by studiot I particularly chuckled at the last one. A 1 tonne ram acting horizontally can raise a 1 tonne load vertically.
You haven't read my post carefully

"angle of ram 0 to vertical ....cos 0 =1 ... a one tonne ram can raise a 1 tonne load"

angle of 0* to vertical IS vertical it's acting vertically and can lift 1 tonne ..

I specifically spelt it out with examples and not formulas since our poster said he is a beginner.

Aug 1st 2017, 03:56 AM   #5
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Join Date: Apr 2015
Location: Somerset, England
Posts: 688
 Originally Posted by oz93666 You haven't read my post carefully "angle of ram 0 to vertical ....cos 0 =1 ... a one tonne ram can raise a 1 tonne load" angle of 0* to vertical IS vertical it's acting vertically and can lift 1 tonne .. I specifically spelt it out with examples and not formulas since our poster said he is a beginner.
My apologies.

You are correct the last one is actually correct.

But the dangers inherent in trying to use a half tonne ram to raise one tonne are still there.

It can be done if the ram is part of a larger machine, for instance if the leverage is right.
But that was not the substance of the original question.

Last edited by studiot; Aug 1st 2017 at 04:02 AM.

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