September 25, 2016 Leave a comment
I have so many pneumatic parts, but I do not build with them often. It was time for me to use them.
Since this would be an intentional pneumatic MOC, I wanted to do something small and simple. I thought a tow truck would work well. As many of my trucks are based on Europian models, I figured it was time to do an American truck. The International DuraStar truck seemed to be a good solution, and they are rather ubiquitous her in the States. It is not too big, and not a pick-up based truck, so it was perfect for me.
I first started with the tow boom. I used the new 1×11 cylinder for the boom extension. I used two of the old 2×9 cylinders for the boom lift. I worked hard to get the boom rigid enough for the extension while remaining small. Still the boom is about twice the width and height of the required scale. It is a little flimsy with a heavy load.
The chassis was more work than it should have been. Working in all the pneumatic parts is simple enough, but giving space for all the tubing and flexibility required much work. Add to the fact that the chassis needed to be strong enough for a Pneumatic pump, and I thought it would be good to have a working driveline, and it got messy fast. Editorial comment: I like clean designs. It’s hard to have clean designs with pneumatics.
The rear wheels connect to a 2 cylinder fake motor in the front. I did not use a differential. It fits, but I could not find a solution to keep the wheel axles connected to the differential while retaining the rear dualies. All of a sudden the choice of not having a differential in 42022 makes a little more sense. I added a little car lift on the back. The elevation is controlled by worm gear, and the extension simply uses two friction connectors. In front of the dualies is a pneumatic air tank on the right, and the two control valves on the left. Hoses fill up the rest of the space. Above the air tank is worm gear transmission for the winch.
I spent a lot of time working on the hood. The cab came together smoothly, but the hood took some work. Working with something that was rigid enough for my standards took some time. I tried some designs with panel, and some designs with plates and wedge plates. Eventually, I settled on a simple studs-on-top brick and plate construction. The mixture of Technic and system looks a little disjointed, but it represented the shape well.
The truck worked well enough. The steering and fake motor worked smoothly and consistently. The pneumatics worked smoothly, and were able to move the functions of the truck well. The car lift on the back cannot handle too much weight.
Two final editorial comments. I am firmly in the linear actuators camp, as I have said before. Fitting rams, running tubing, and trying to use those little valves just to get position of the pneumatics perfect drives me crazy. Second, I really like the 49.5×20 wheel and tire set. It is a great size and has perfect look. But when I build trucks with them I get frustrated. They look better as dualies on the rear, but there is no good connection to a differential on a 15 or 17 wide setup. Eventually I will find a solution, but at this time, they are driving me crazy, so stay tuned.