Where I can find the formula? 2

[KrisLizak]

Hi

I have to design a railroad hinge tip wooden crossing gate. Must be 28'. How do I calculate where should I install a small beams between two arms? And how calculate the pressure from wind on those arms?

Thank You

 

[FeX32]

A diagram would illustrate your problem more clearly.

Fe

 

[racookpe1978]

They've been building railroad crossings since about 1830. Been making gate crossing levers for almost as long. 8<)

Frankly, I'd go measure two or three: Don't bother re-calculating how round a wheel needs to be if you don't have to. Also, you may see other "small solutions" on the operable units that are there to solve problems you haven't thought of yet.

Wind load? The vibrating, moving weight of a thin 28 foot lever-mounted as it is pulled up and down will override pure wind loads on a 4 to 6 inch wide flat plate. That is: the twisting force sideways from wind will be small compared to the force from gravity and the dynamic moving forces of the lever. So once you've mounted the boards to the pivot arm - say, perhaps with four 1/2 diameter galvanized through bolts in a rectangular pattern around the pivot block - the wind load will be resisted very adequately.

 

[JStephen]

I would think that there is some sort of design and construction standard for building these as well. You don't want them so weak they blow over or rotate into the train, don't want them so strong or heavy that they act like a guillotine on motorists; there is probably a fixed height and width for them as well.

 

[MiketheEngineer]

How about just go buy one??

 

[KrisLizak]

Thanks guys for all the replays. I will look for more information in old notes made by last engineer.

 

[SalamiVice]

As for wind, if you want a quick check.

Find the frontal surface area being hit by wind.

the solve for the resultant force of this:

Cd=(drag force)/(0.5*(Specific density of fluid)8(V^2)*(Asurface)

where,
Cd=Coefficient of drag, you can approximate this to a general shape and get a value from any fluid mechanics book.

V=velocity of wind.

You have all parameters, so solve for "draf force"


Once you find the Force use this to calculate the bending moment or stress on your structure.


the equation works fairly accurate, compared to a CFD analysis or real life testing.