Miracles of Channel Stiffness

Miracles of Channel Stiffness

I mentioned yesterday that I was hoping someone would tell me if my calculations were correct. I spent a bit of time checking the spreadsheet (and updating it), and I am now confident that the calculations are correct. Of course, that requires the underlying equations be right....

It is astonishing how non-linear the relationship between thickness and stiffness for a channel is. As an example, with a 4" wide channel, .125" thick, and the verticals are .5" high gives a maximum deflection of .0326" inches. At .25" thick, the deflection drops to .0107". Doubling the thickness cut the deflection by about 2/3.

Making the channel wider, however, is also non-linear in its effects. Doubling the width of the channel only gets about 1/3 more stiffness. When making the trade-off, if stiffness were the only goal, you would want thick but not very wide.

Now, the trick is to call Metal Supermarkets, and find out what sizes of channel they have in stock, plug the dimensions in, and see what makes the best fit. Because the goal is to reduce roll, wider is better. At the same time, the price goes up, and thick contributes more to the stiffness. Since I have to trim the verticals so that the tube fits into the bottom of the channel, I don't want two thick of a channel--because I have to run this through my table saw to make it fit.