Calabar, on 12 January 2012 - 09:29 AM, said:
I think this is simply a dummy "all-in-one" model to show the bug.
Indeed, I posted a dummy (generic) model to explain the bug as requested by Superkalle.
Apparently the dummy also failed to explain the problem properly.
I encountered this one while building an alternate version of Creator Set 6753 Highway Transport in LDD 4.1.8 Extended. I have recently finished the model and it is now posted
here. The bug is in Version 3 - the Salvage Truck. It is part of the salvage crane. The boom of the crane can be made to extend/retract by turning a single gear wheel that grips into the toothed bars on the boom.
If following the instructions, the initial position of the gear wheel is directly above the separation of the two toothed bars - it grips into the ends of both toothed bars. In that position, LDD does not allow it to be fitted (shown by Red Wheel in mock-up).
If - in LDD - the boom is moved (1 stud or more either way) the gear wheel is no longer positioned above the end of a toothed bar, but grips into the other teeth of the bar. Then LDD has no problem of letting the gear wheel fit and grip (shown by Green Wheel in mock-up).
Maybe this picture helps explaining:
It is official build: for the instructions for this Truck see
here. The construction of the movable crane with gear wheel and the tooth bars is on pages 33-39.
I have an actual set at hand (it my son's). It is now in it's main transporter version (no chance to check the problem now - I need permission to touch it

). We have built it into this model before and I cannot remember encountering problems with brick stress in the crane.
As I've said before: I think it is a problem with the modelling (boundaries) of the ends of Toothed Bar 3743.