How did you do your axles

[Rombus]

Our team used a friction fit in alu shaft with cotter pins and spacers to keep it in place. Alu shafts fit though the holes in our alu frame. Can anyone see the issue here? We found out pretty quick that this wasnet the best idea, they were hard to remove after use, and we had alot of problems with them binding in the holes and mushrooming when we were trying to remove them. one had to be hacksawed off and nearly drilled out! We are going to design something better next year.