Can/must this bracing being improved?

[Kumbbl]

Hi all,

i have moded the Mobile crane 8421 so the slewing is now driven by gears. On the one hand it works actually ok but on the other hand i discover that the upperstructure of such a big crane is quite heavy so this slewing drivetrain is obviously under stress. I have tried to keep it simple and i have also tried to brace all axles and gears as good as possible (e.g. the grey axle above the worm gear is only for bracing/bearing the 8 teeth gear at the right end (otherwise also a axlepin without friction could be used but i thought this could be weak).... but i'm not a pro... so the question / plea is: Could you please take a look at the following picture which shows all this stuff:

The red line shows the drivetrain for slewing; at the worm gear a double beared vertical axle goes to the large technic turntable which drives the upperstructucture via the inner ring. left bottom in the picture you see the zoom for the lower bearing ... left top you see the upperstructure from underneth, how the vertical axle is mounted there and how it is braced.

so: Is this drivetrain well braced or with other words: where do you see weak points?

In general now i have a suspicion: TLG doesn't drive slewing by gear trains because the upperstructures of their big mobild cranes are simply to heavy so the slewing can not being guaranted save without cracking gears or at least this needs too much effort in construction/design... Am i right, what do you think?

The small mobile crane 8431 is an exception because its upperstructure is way lighter than 8421 or 42009....

Thanks a lot!

[Saberwing40k]

I'd recommend bracing the 8z gear on the axle above the worm gear, as that will rid out otherwise. It's easy, luckily. Just replace the cross joiner the 16z gear is connected to, and make the mounting axle one stud longer. Everything else looks fine.

[Jeroen Ottens]

I would recommend driving the turntable on the outer ring. That way the teeth of the gears have lot less force on them. You have to put the turntable rightside up then of course.

[Kumbbl]

I would recommend driving the turntable on the outer ring. That way the teeth of the gears have lot less force on them. You have to put the turntable rightside up then of course.

funny, that was my first try - until i saw that this is impossible with 8421 (at least without redesigning the whole upperstructure) :-(

have a look at the bottom of the upperstructure of 8421 and you will see that the changeover catch is so nearby the outer ring of the turntable that there is no room for the driving 8z gear - it would collide with the changeover catch when slewing.... therefore i had to use the inner ring... placing the changeover catch somewheer else would result in a heavy redesign of the upperstruture and i want to avoid this...

[DanFraser]

Instead of the 8t to 8t connection, you could straight through drive that axle by moving the double pin with bush one hole closer to the camera to make way for the axle.

[Kumbbl]

sorry, but i do not understand what you mean...