The cranks were a challenge for me, it had a lot of problems like a lot of problems. One of the problems was that when it was time to build the crank all my pieces were smooched together and when i finally got tin together it was not strong it it was just a mess. My second problem was that I used crank b and when I was building that it completely broke down like everything just ripped into pieces. As you can see it was really big struggle.