Rather more days later than I originally anticipated (1), and I’ve got round to dismantling the Tracked Crane and building the 9391 ‘B’ model, the bulldozer.
It’s a fairly simple build which doesn’t take long at all. In terms of functionality, it’s leaning towards the ‘basic’ end, with the bulldozer blade that raises and lowers being the only part that moves courtsesy of some ‘Technic engineering’. There are two spikes on the back (still not entirely sure what they’re for - some sort of plough-type thing?) that also move, but that’s a simple ‘get hold of it and move it’ arrangement.
It’s smaller than I expected, and comfortably sits on the palm of your hand. It’s probably not unrelated to the fact that there are several parts left unused in the bag. With the two mini trucks, virtually every part was used in both models - I guess as things scale up, it’s not always possible to recycle everything.
Still, a nice little model.
The Lego Technic 9391 'B' Model - the Bulldozer
One of the things that I found interesting was the use of angles, which I hadn’t seen in my previous builds. Up until now, everything has been clipped in using multiple connectors, meaning that nothing had any play in it. However, the uprights for the cab roof are only fixed at one point, in order to allow those uprights to be held at an angle. The upshot of this is that rather than being a rigid structure, the cab roof actually has a fair amount of play in it, and can be wobbled backward and forward. While I can understand why the build is like this, it’s a little disappointing, and I’d probably be looking for some way to reinforce one or more of the beams in order to give the structure some more rigidity.
Probably just me being picky. (2)
As mentioned, a pretty straightforward build, with a gearwheel at the back of the ‘dozer turning an axle with a wormgear. This drives the gearwheel on a second axle which is attached to the end of the blade arms, enabling it to be raised and lowered.
The plough / spikes at the back are simply hinged, but they use friction pins so that the spikes stay in whichever position you put them. The caterpillar tracks are, understandably, exactly the same as the crane, and work well on textured surfaces like carpet, but tend to slide on smooth tables.
All in all, a fun little model - not as interesting (to my mind) as the ‘A’ model, but a nice build all the same.
The gearwheel for raising the blade can just be seen at the back of the vehicle
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(1) It's a lot easier to build, and more importantly, photograph, models when you've got good daylight. At the moment, that means building at weekends. No fancy light tents for me.
(2) No 'probably' about it.