Boom Arm Math

Hi
I'm desgining a projector screen boom arm for a college project and need help with some math.

http://i54.photobucket.com/albums/g1...oomarmhelp.jpg

I need help in working out B and D from the image I have attached.

The load is 30kg and the span in 12'

Any help work be great!

thanks
Michael

Hello Michael,
A similar problem
A 2000 lb weight is attached to a 20 ft boom which is supported to wall and by a cable attached 11.5 ft above the lower mount. A force diagram shows a 4000lb tension in the cable 2000 lb downward force at the beam attachment and 3464 lb compression in the beam . This is what you need to do for your problem.The distance between the supports must be determined by you .You might try 4 ft. Stresses at the hinges and wall supports have to be calculated

bjhopper

Thanks for the help.
How did you come up with 4ft?
Sorry but i'm really rusty with my maths!

Hi Michael,
As the designer you have to make the decision based on wall or structure attachment and secondly to minimize the costs of materials,4 looks a reasonable start


bjh