I have several questions that are related to something I am designing. I am having a hard time finding the correct formulas I need, so I am here :D Anything will be helpful, from general topics/ideas to get me in the right direction, to specific formulas. I do not mind abstract ideas, this is a hobby and learning everything is more fun than the actual project :) 1. I am creating a hollow torus (circular pipe) that is a partial vacuum. I need to be able to calculate the failure point of any material used to create the torus (steel, acrylic, etc). I would imagine this to be the structural integrity of a circle, given that a torus is a series of circles. 2. Inside the torus will be an object that will be nearly the same diameter as the inside that moves and is lubricated. I need to calculate the friction/drag between the object and the inside of the torus. Ideally, this would be a formula that I could use with any given area so that I can chart the change in friction with the change in size. 3. A variation of this that would also be helpful is to calculate the friction of wheel-object or wheel-wheel contact on a tracked system. 4. I would like to be able to calculate the gain in pressure from leaks. For instance, if the inside of the torus is 0.02 atm, and the outside is 1 atm, how many atm per second would enter into a hole that is 1 square mm. 5. Last but not least, how do you calculate the change in boiling point in relation to pressure deviating from 1 atm? The only thing I can find is calculators do to it for me, and I want to calculate it myself. Edit: One more thing - Are there any free CAD programs that would do structural calculations for me? I'm using sketchup currently.