Cantilever Hinge End Loading

[Gobiman]

Hi,

Possibly a simple analysis:

I have a hinged cantilever support (see pic) supporting a 5032 N end load. The 45deg support strut experiences a 7117N tensile load and I have sizes this to suit.

My question, lies at the hinge pin. What forces will this hinge pin experience? I presume it will be the vertical load along with some horizontal component.

Will the bending moment of the beam effect this?

The hinge will be mounted in double shear so as to reduce the load on the pin.

The entire design is for a folding platform.

I appreciate all input.
Thanks.

 

[hokie66]

Since the pin has to take both the vertical and horizontal component due to the loading, its load will be the same as on the diagonal, 7.1 kN.

Now you have the problem of how to provide adequate structure to support the forces from the vertical cantilever and from the horizontal strut. There will be about 6 kNm of bending on the vertical cantilever, and this along with a bit due to the eccentricity of the vertical member has to be resisted by the beam, I assume in torsion. A wide flange section as you show is not much good in torsion.

 

[rb1957]

no, the pin will react only the horizontal component of the diagonal strut, 5032N. The diagonal strut is in tension, sqrt(2)*5032N. The post is in compression (5032N) and bending (due to the lateral component of the diagonal strut). the reaction at the base of the post is 5032N (down) and a moment (= 5032*1150Nmm), since this is the only attmt to the rest of the world.

 

[hokie66]

Yes, I gave incorrect advice. The pin only sees the horizontal component. The second paragraph of my reply stands.

 

[handleman]

Also of note: if this is really a "platform", assuming a point load at the end will give you different reaction forces than using a (probably more realistic) distributed load or a load at the platform center.

-handleman, CSWP (The new, easy test)

 

[Gobiman]

Thanks for the replies.

The vertical cantilever is a support post. (100x100mm box to be precise) I have calculated the max. deflection and bending stresses in this due to the 5032N force acting on this.

I realise that the wide flange section is not much good in torsion, but for the loading involved and the flange size, this is of little concern. I might consider adding stiffeners to the rear of the vertical cantilever at the base to distribute the load over the flange.

The pin I am concerned with is the pin at the base of the post hinging the platform and not the pin(s) at the diagonal strut.

I assume this pin would experience a vertical load?

I realise that a uniform load would be more realistic but I am calculating a worst case scenario situation here.

 

[handleman]

No, no vertical load on the pin as you have drawn it with the load weight acting only out at the end of the platform. That is why I said you need to evaluate a more realistic loading model. If you need a "worst case", increase your load, don't locate it incorrectly.

-handleman, CSWP (The new, easy test)

 

[handleman]

Oh, and if the safety of a human being is at all involved with this structure in any way, pay a qualified person who understands statics to fully evaluate it.

-handleman, CSWP (The new, easy test)

 

[rb1957]

draw a free body diagram of the structure ... the 5032N load and it's reaction to the rest of the world, at the base of the column, clearly a force and a moment reaction.

now a free body of the outer end of the beam, where the load is applied ... clearly the beam is in compression (5032N). thus the pin you're interested reacts only transverse load.

i'd also analyze the column, but the critical section looks to be at the base.

BUT, as handleman is trying to tell you, if the 5032N load is distributed over the length of the beam, then the answer, as far as the pin is concerned, is completely different. if you've assumed a pinload at the remote end is conservative, it is conservative as far as the reaction at the base of column is concerned; but it may be unconservative as far as the beam and pin are concerned.