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Paper models, photos and musings of a Paper Kosmonaut

26 March 2017

ZIL 4906 [9] some improvement

even though I promised myself not to tinker too much with this model, I encountered a little dilemma earlier today. The cranes are supposed to stretch all the way back to make an angle of about 130º with the deck, to reach out far enough for grabbing the Soyuz capsule. These cranes now only made it to 80º max. So, it had to be done. I had to take it apart carefully and redo it.
In short, They now bend back to 130º. I did this by making an extra piston, so the arms could stretch much further backward.

This was the original configuration. And as far back the arms could reach. Clearly not far enough.


And this is how far back they can reach now. Thanks to the double piston it now looks much better.

It started by ripping the cranes apart. I wasn't that worried about damage because the cranes are very worn out in real and I was planning to weather then anyway. So, I carefully bended the parts where the pivots were and broke the crane's arms loose. First thing to alter were the pivot points themselves. Being loose parts and smaller than the arm's width, they were prone to tearing and suffering from tensions while moving them.



I took a piece of spare kit with the same colour and glued it over the bent part of the arm. Now the pivot point was more or less incorporated into the full structure and less prone to breaking off. I had to adjust the width of the new strip a little but this is something no one will notice in the end.


Up next were the pistons themselves. I used the original part for the top piston. 
I measured it and made a new hollow piston with the inner diameter of the smaller one. Inside, I made a small strip of paper in the top to create a stop for the inner piston, which got a thicker strip around its bottom. This way the piston would never leave the shaft.

 

After this, the outer piston shaft was made again, now with a larger inner diameter to fit the new piston. Here too, I made stops to keep the piston inside the shaft.



Now all that wasleft was to replace them on the crane bases still on the truck's deck. They fitted well and weren't a fuss to get back in position at all. The result however, was spectacular:




I measured the reach with a flimsy first prototype of my self-designed Soyuz capsule and it had the right distance from the vehicle, the height was correct and with this redone, I finally can get on with another small detail correction of the cranes: the secondary piston sets on the arms itself to further extend the arms.
More on that next time.

See you!
--PK
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