Im in the process on building something similar with the rack you see in the picture.
What I want to know is if its possible to determine the optimal length of the tube on the frame and on the rack to allow the max load under stress without the rack breaking/bending on a spot that its not mounted on the frame, and what would be the max load?
and if it is, how to calculate it? :)
things that i know:
- number of tubes
- length
- diameter
- thickness
- bending tube angle
- stainless steel type
worth saying that this is more of a learning exercise.
More of an engineering problem – see the subfield of engineering called “statics”. Physics has equations for everything here, but the specific combinations of materials and geometry and so forth is solidly engineering.
Then, the route to go would be physical testing. As long as the load is not balanced in front of the front axel, the bike should be drivable. If it’s balanced in front of that axel, then you will have a real limit eventually where the back tire is no longer able to make contact with the ground. The load would have to exceed your body weight somewhat.
If you exceed that load, you’re probably fine on smooth ground. The welds in the frame are likely first to go. During an impact (bump in the road), engineering statics no longer applies, and you end up in dynamics. So you could load it up and it’ll be fine sitting in one spot, and then start pedaling and hit a bump and a joint crumbles or something.
Finally, the bike probably has a rated maximum rider weight listed by the manufacturer. If you just want to play it safe, find that number, subtract your weight, and go nuts.