It's rare for the alternative 'B' models of Technic sets to garner much attention as they are usually not that interesting. However, that's not the case with 42055 Bucket Wheel Excavator. Many of you have been asking about the mobile aggregate grader to find out whether it's worth building: does it work, how does it work, how many parts it uses and so on.
So I thought it was only right that I should build it myself to try and answer those questions. I didn't take my BWE apart, I bought another set, from Amazon.co.uk at a bit below RRP.
This isn't a review as such, but my observations on building and operating it.
TL;DR: yes, it works, but not without problems.
The first thing to bear in mind is that you will need nearly all of the parts to hand to build it because, unlike the main model that's built from numbered bags, to build this you need to open all of bags #2 - #8 and sort the parts before you start. Consequently you'll need a very large area to work on.
Bags #1 don't need to be added to the pile because they are for the mine truck, which is built identically to that for the BWE. I didn't build a second one.
The model uses something like 75% of the parts and, crucially, the new parts in it are used only for cosmetic purposes so if you have enough Technic laying around you might be able build the actual mechanism without resorting to dismantling the BWE or buying another set.
The completed model
The completed model looks impressive and suitably industrial. Gearboxes allow the single XL motor to propel the machine back and forth or operate the grader. You can't do both at once.
The left-hand output conveyer in the image below can be raised and lowered using gears on the side, while the one on the right can be rotated about 180 degrees.
(Note: I took the pictures outside in the garden this morning so they have a nice 'warm' tone to them.)
A third conveyer sits at the bottom of the input chute. It moves much slower than the output belts.
This side of the machine is not shown in any official shots but I think it looks quite impressive: the battery box sits on one side while two exhaust stacks occupy the other.
This is the end that the large pieces come out of. The conveyer assembly has a large turntable top and bottom allowing it to be rotated by the black gears, or simply pushed round.
So, how does it work? Quite cleverly as it happens, but unfortunately the mechanism is buried deep inside the machine so is impossible to photograph without a major dismantling. (Yes, I should have photo'd it before finishing it, I know...)
Basically, as the conveyer moves an 'agitating plate' is raised when the 1x5 beams on the belt pass under its end, which then drops again once it has passed. This in turn causes three axles under the input chute, mounted at a slight angle and spaced to allow 1x1 rounds to pass through them but not the 2x2s, to move up and down/vibrate as well. The 2x2s travel on top of the axles to their exit on the left (in the photo below) while the 1x1 fall through to theirs, on the right. You can see the ends of the three axles in the picture above.
That's the theory anyway... It's a neat mechanism and it almost works. Generally, the 2x2s always exit the machine correctly but the 1x1s often don't.
There are a number of issues that cause this and other problems:
- Occasionally, 1x1s will exit with the 2x2s. It seems to happen if they are carried along inside on top of multiple 2x2s or land sideways on the three axles. If that happens they invariably drop into the depths of the mechanism rather than travel along the belt because it's not been designed to stop them doing so.
- As the 1x1s ride up the correct conveyer, if they are close to the edge they sometimes jam on the sides, and if they are standing upright they can get stuck right at the end, by the yellow beams. In both instances the machine grinds to a halt
- If 'rocks' are poured into the exit of the input chute rather than on its conveyer belt you end up with too many inside which can cause the agitating mechanism to fail to operate properly.
- The 1x1s often just sit on the agitating plate and sometimes never exit. This is because (a) they are not spherical and (b) the plate is not completely smooth, so depending on how they land, they don't always roll down it. The plate's up and down movement is not sufficient to encourage them to move!
After experimenting this morning, I found a simple fix for the latter problem which doesn't solve it fully but does improve things considerably:
Here's the end of the agitating plate. The black axle is raised and lowered as the beams on the belt pass underneath it. By adding the 1.5l tan pin to the middle hole of the beam, the axle is raised a bit more and, importantly, falls a bit further, which jolts the 1x1s into motion and generally causes the machine to operate a bit more smoothly.
If the 'rocks' were LEGO footballs and 1x1 spheres (which don't exist) I am sure it would work perfectly, but as it is, yes, it works, but not without problems.
Nevertheless it's a very interesting machine to construct and operate and if you have the opportunity to build it for yourself I encourage you to so do. Perhaps you'll come up with some fixes for the other issues...
Thanks to Evvilspoon, who's also built it, for confirming that it was not just my model that had problems with the 1x1s.
This is definitely a model that benefits from a video review but they are thin on the ground on YouTube at the moment. If I wasn't hopeless with a video camera I would have had a go myself.
However, I did find this one by Desert Eagle LEGO Technic Creations this morning that shows how it works, and how it jams. It's in Russian with subtitles.