I just finished building your wonderful crane. It is really impressive. I did not fully understand its true dimensions from the pictures. It is so huge I can freely drive my 42030 Volvo under it. The rubber tire engagement mechanism is genius and I like the gearbox, the diagonal axle trick is interesting.
I love how modular the crane is, it is a pleasure to connect big parts with “pins with stop bushes”, it feels almost like an official set. I hope someone takes advantage of that in the instructions.
Unfortunately, the actual functions work poorly. The need to constantly apply pressure kinda kills the pleasure and the tire slips nevertheless, making the movement not steady (it is really slow anyway). I understand that there is a lot of friction in the gearbox. The top two clutches are not fixed (old school solution) and constantly get in the way when you don’t want them to, making the friction worse. The fact that these gears are not synchronized does not help either.
The lowermost block with 24 tooth gear is not attached firmly enough. I had to put the blue axle pins or even the 4L axle back in place many times, they are easily kicked out when the movement is blocked down the drivetrain. This mostly happens with boom lifting, not with the rope-driven parts. Maybe there was some solution and I missed it?
The upper part of the diagonal axle construction can be easily misaligned. The two 4L axles which hold two halves of superstructure together are highly stressed and also tend to fall off. I connected them with two axle joiners and an axle which helps somewhat. Maybe that part needs more strengthening?
The universal joint has slipped off its 4L axle one or two times under load.
I think two t-shaped beams interfere with engagement of the clutch responsible for boom lifting. The other three are noticeably easier to move.