Large scale Roberval Balance/Beam design help, please

[Mac S]

1. Design and engineer a scale capable of weighing human beings. I've elected to use Roberval's basic design because of its stability. Consideration: The structure must be erectable by two persons using only human powered hoisting devices. I will use water in the counterweight and man-bucket to achieve initial equalibrium. The 400# notes at the man-bucket and CW are suggestions only because the problem does not tell me the number of people being weighed.



2. Due to weight restrictions (~200#?) of the individual parts to be assembled I'm thinking an open web truss would work well for the primary balance beam. Can someone please guide me to a link or through the process of designing a beam that will work in this scenario? Btw, this is my first time at Physics Forums - it looks like a great site! Thanks for any help in advance!

Roberval link: http://www.lhup.edu/~dsimanek/museum/roberval.htm"



3. I have solved the mechanics of the weighing process (moving the adjustable weight), yet my attempt to solve the beam design has simply been putting the "bones" in place graphically. This problem is for a relatively basic physics course project, but I would like to apply real beam engineering to it as I will be moving into engineering coursework next semester. Please see my basic design in the attached PDF.

 

[Valkarie]

Can someone please provide me with a link or point me in the right direction of defining my beam and calculating the forces it will experience? You can use the equations of beam mechanics to calculate the forces that your beam will experience. A good reference is "Engineering Mechanics of Solids" by Egor P. Popov. It has a section on beam analysis which includes several useful equations. You can also find a lot of useful information online, such as this page on beam mechanics: http://www.efunda.com/formulae/solid_mechanics/beams/index.cfm