What is the end result you are after? If as you said earlier it is a part of a motorcycle swing arm that you want to work out, you could have made 10 of them by now. It’s 3 pipes, one of them bent. You could make it out of toilet roll or paper towel tubes and a bit of cardboard. Even in steal with tak welds.
Even if you manage to model this correctly and hollow it will still cost about 250 dollars to print from most places, so you print it, get it back, it doesn’t fit, you spend another 40 hours remodelling it, pay for another print wait for it to arrive in the mail…
If the final swing arm was going to be made of titanium and would be ridden on the first trip to mars it might be cost effective.
As for your current model I really don’t know what to tell you. You don’t seem to understand the concept of groups separating geometry. The model should be 3 groups that you can pull apart and each should be a solid. None are solids.
Here’s one of your earlier ones cleaned up and made hollow along the pipes.
SwingarmBox.skp (263.9 KB)