Review: 42055 Bucket Wheel Excavator

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When 42055 Bucket Wheel Excavator was revealed at the toy fairs at the beginning of the year it understandably caused much excitement among Technic fans given that it is the largest Technic set ever in terms of part count -- just short of 4000 -- and dimensions.

Having now built it, I can confirm that it is indeed an impressive machine, but it's really pushing the limits of what is possible with the Technic system and one motor...


The prototype

Unlike the other three large Technic sets released this summer, this one is not based on a real-life machine. Its design is certainly influenced by real BWEs but it looks nothing like any that I have been able to find pictures of. Take a look at some images yourself and see if you can fine one.


Packaging and parts

I won't bore you with pictures of the box but will point out the alternative model which is a rather cool mobile aggregate processing plant. I believe you feed 'rocks' into the top hopper and they come out one end or the other depending on their size and I am told it's fun to watch. I have not built it because instructions are not yet available on LEGO.com but I probably will.

42055 Bucket Wheel Excavator

There are just two new parts in the set: the bucket (6145856) and the 1/4 circle gear piece (6151167) which you can clearly see in the pictures below.


Construction

Instructions are provided in a single 550-page book with construction split over 669 steps. Thankfully parts are in numbered bags. I know some people relish the additional challenge that having all 4000 pieces to sift through would provide but I am not one of them!

42055 Bucket Wheel Excavator

First to be constructed is the truck which is very similar in design to last year's 42035 Mining Truck. This one has a revised cab and front, and no engine, but the unloading mechanism, operated by twisting the black gear on the side, is the same.

42055 Bucket Wheel Excavator

42055 Bucket Wheel Excavator

The chassis/underframe of the excavator is constructed next. The first four of fourteen 1/4 circle gear racks are mounted on the base to allow the body to rotate. The gear in the centre of the circle drives the tracks.

42055 Bucket Wheel Excavator

There's some complicated gearing buried inside which links the tracks, the rotation of the body and the lower conveyer belt via the three vertical axles on the left to the upper body assembly.

42055 Bucket Wheel Excavator

After 225 steps and about 3.5 hours of building the chassis and lower part of the body are complete.

42055 Bucket Wheel Excavator

Next to be added is the lower conveyer belt.

42055 Bucket Wheel Excavator

Bags numbered six builds the business end of the machine and this is the most time consuming of the eight bags, taking around 1.5 hours.

42055 Bucket Wheel Excavator

Following on from that, the rear end of the digging arm is constructed which includes the control panel/gear box. Here you can see the innards before they are hidden by the top panel.

42055 Bucket Wheel Excavator

Now, by this point the model has become so big that it no longer fits on my regular photography table so I was unable to take more photos until I had something bigger. The following pictures are therefore taken with different lighting in a different 'studio' and to be honest I am not that happy with them but hopefully they will serve to illustrate the finished model.

However, we still have not finished construction... At the end of bags #7 the model is functionally complete and can be tested and I urge you to do so because if there is any debugging to be done it will be more easily achieved now.

Bags #8 add the cab, bodywork, walkways, lights and other cosmetic details. Overall, the build time for the entire model is around 7 hours.


The completed model

It's massive! The arm is 75cm long. It stands 45cm high. It's 28 cm wide. There are a lot of nice finishing touches: the walkways, handrails, lights, ladders and so on which enhance its appearance considerably.

42055 Bucket Wheel Excavator

42055 Bucket Wheel Excavator

42055 Bucket Wheel Excavator

It's somewhat front-heavy so there is a bit of a tilt on the body which results in the vertical frame not being exactly vertical. It doesn't seem to interfere with operation though.

42055 Bucket Wheel Excavator


Operation

It's a long satisfying build and the finished model looks great, but how does it operate? Unfortunately this is where it's a bit of a let down.

The machine is powered by a single large PF motor mounted at the end of the arm. Operation is fairly simple: the middle gearbox lever switches between rotating the bucket wheel and the body on its axis or moving the machine forward/back. When you have selected one or the other, you can then choose forwards or backwards movement (right lever below) or clockwise or anticlockwise rotation (left lever) of the body. Whichever you choose, the bucket wheel always rotates in the same direction.

You can't go forwards and rotate the bucket wheel at the same time which is a shame.

42055 Bucket Wheel Excavator

The bucket wheel rotates at something like 6 RPM; forwards/backwards movement of the machine is probably something like 10cm a minute, i.e. it's very slow. I don't suppose real BWEs exactly race across the quarry though, so it's probably realistic.Given the weight of the machine it's a wonder the motor can move it at all. Also, it needs fresh batteries. Anything less than full power from the motor will result in nothing much happening at all.

Remember what I said about testing after bags #7? I did just that and found that the bucket wheel barely moved and kept juddering. It was perhaps not surprising given that the single motor is driving two conveyers, the huge great bucket wheel (which is driven via the upper conveyer) and rotating the body as well. There was just too much friction in the system which was causing the two white slip gears (that you can see in the picture of the open gearbox above) to continually slip rather than drive the output axle.

It's entirely possible that I was not careful enough during construction and mounted gears or connectors too tightly thus causing too much friction but if I -- a Technic veteran with 20+ years experience -- can do that, what hope do kids have of building it any better?

The solution was to replace the slip gears with regular ones, the two large grey gears at the top of the picture immediately above. Now the bucket wheel moves more smoothly, but still not perhaps as smoothly as I would like. Of course, should the mechanism jam or stall for whatever reason the lack of slip gears in the drive chain puts the motor at risk of damage but given they are a commodity item I am not too worried about that.

The arm and thus the bucket wheel can be raised and lowered manually using the black gear on the side of the body which you can see below.

You can also see in this picture the three axles that transfer power from the upper part of the machine to the lower part. They are connected using 'slip axles' which means it is easy to disconnect them for testing purposes.

42055 Bucket Wheel Excavator

One of the cleverest aspects of the machine's operation concerns the lower conveyer belt. The exit from the belt would usually be placed above an awaiting truck to collect the rocks. But, if you have enabled arm rotation, the lower conveyer would rotate as well resulting in the the rocks missing the truck.

To solve this problem it is possible to lock the lower conveyer belt so that it remains stationary even as the arm rotates which keeps it in position above the truck. This feature is enabled using the gearbox lever at the back: push it forwards or back to lock it. There's a lot of slack though, and I think the arm has to be in a particular place relative to the body for it to work properly but when it does, it is a great feature and one that Sariel demonstrates in his video (see below).

42055 Bucket Wheel Excavator

One thing I have not mentioned yet is the effectiveness of the machine to pick up the 'rocks' (1x1 round bricks and 2x2 dome bricks) and transport them through itself. Unfortunately, it's virtually impossible to get the buckets to pick up 'rocks' from the ground and you will see why if you watch Sariel's video. Once rocks are in a bucket though, the machine works well although it does occasionally get jammed up causing it to grind to a halt.

The bucket drops the rocks down the chute onto the conveyer which transports them along the arm. A hinged 'door' prevents them from falling out the end.

42055 Bucket Wheel Excavator

The roof of the cab can be lifted but the seats are too small for a minifigure to sit on them.

42055 Bucket Wheel Excavator


Verdict

Unfortunately, I have to say, I am disappointed with its operation. It's a huge, heavy, complex and impressive-looking model, and given that it's powered by a single motor positioned right up in the back of the arm it's perhaps a wonder that it works at all.

But, it's virtually impossible to automatically 'dig up' rocks so much of the play value is lost as a result. The bucket wheel's motion, on my model at least, is a bit juddery, which can perhaps be explained by my lack of care when building but more likely because it is being driven via the conveyer belt and dozens of gears.

42055 Bucket Wheel Excavator

It's a great set to build and to behold but its operation lets it down a bit. Also, its size -- while impressive -- will make it difficult for many people, myself included, to display. It's not something you could take into work and put on your desk, for example!

I am therefore not able to wholeheartedly recommend this set: Personally I think it's pushing the boundaries of what's possible with Technic, particularly the Power Functions system, a bit too far and the model has suffered as a result.

Die-hard Technic fans will want it regardless but if you are on the fence or have limited funds, there are much better Technic sets released this year that I would buy before this one.


Video review

This is definitely a set that benefits from a video review so I encourage you to watch Sariel's. You can skip past the unboxing and construction to 17m 30s to see the machine in operation.

Watching it again now, I see that Sariel's wheel judders a bit too, so it's not just me...

Have you built it? What do you think? Does yours work okay? Let us know in the comments.


Thanks to the LEGO community team for providing the set for review. The review is an expression of my own opinions and not those of the LEGO Group.

43 comments on this article

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By in New Zealand,

Great review. Thanks Huw. I seem to be on the fence for the purchase of this set primarily due to price.

I would really like the 1/4 round gear racks as they offer a modern alternative to the 4481 Hailfire Droid wheels - http://rebrickable.com/parts/44556 . These new parts offer better connection points and therefore will make it easy to incorporate them into Technic MOCs.

I will probably purchase this set eventually and add some Mindstorms functionality. I would use this as a show display set with 1000s of small grey parts in a LEGO open cast mine.

Would it be possible to do a review specifically on these new curved gear racks, with some specifics on diameter and whether they could be used as a roller bearing?

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By in Australia,

It would probably work better at picking up 'rocks' if they were piled up in a kind of embankment rather than just lying on the ground. That seems to be how real bucket wheel excavators are employed. I would like to see how it goes in a more 'realistic' configuration.

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By in United Kingdom,

@Huw after the testing after bags 7 and after replacing the gears, did yours rotate?, as mine doesn't rotate properly and the bucket wheel (like yours) is very slow and juddery along with the conveyors.
I still think it's a great set and as your review stated, lacking in power for the size.
Great review.

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By in United Kingdom,

^^ Yes, it works OK now, and ^ that's exactly the fix I did here although it should of course work with the clutch gears. Sariel's seems to, although it does stall at the slightest touch of the buckets.

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By in Netherlands,

A nice review of a set I've definitely been eyeing.
The model reminds me a lot of smaller type bucketwheel excavators, especially something like a Sandvik PE-100 ( http://www.directindustry.com/prod/sandvik-mining/product-40142-354732.html ).

I have to say, it impresses me quite a bit as far as integrated functions are concerned, but just adding one or two extra motors would have improved the model a lot. As the review states, it seems to be asking to much of just the one single motor.

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By in United Kingdom,

That first photo of the crawler base without anything else on it made me realise how much I want an update of 8480 Space Shuttle

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By in Germany,

I'm nevertheless very impressed by this set, especially than I'm more into building and displaying rather than operating it.

One question though. Is it simple enough to replace clutch gears with standard ones after completing the model, or it'd better be done during building?

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By in United States,

It seems to me that there must have been an engineering challenge to perform the maximum amount of functions with a single motor. While I can appreciate that design challenge it does seem like the set suffers from this. Beyond the performance issues a miss to me is having the elevation of the arm being manual instead of powered. I guess they just couldn’t find a way to connect it to the single motor.

I’m still looking forward to getting this and I plan to experiment with adding additional motors and remote control functions (and lights, lots of lights). I would like to put a separate motor in the wheel area to independently drive it instead of it being driven by the belt. I would also like to add 2 motors in the base to drive each track separately and provide steering functionality.

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By in United States,

Wow that is really big! Great review Huw.

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By in Netherlands,

Thanks for the review. If this thing would've worked properly I'd have bought it. I don't sit around playing with Lego anymore, but I don't really see the point of building something massive that in the end just doesn't do what it's supposed to do.

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By in United Kingdom,

Fantastic review, and the photos were more than adequate for me to judge it, so I wouldn't worry on that score!

As much as it pains me to say this, given the incoherent glee with which I reacted on first seeing it, I don't think I'm going to buy it. While it's very good value and a fantastic source of pieces, I think I'd have preferred to see them charge more and build an extra motor in - though presumably there are logistical and marketing reasons why they didn't.

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By in United Kingdom,

Well to be fair it does do what it's supposed to, but only just and only if extreme care is taken during construction and you use the 'hand of God' to help with the loading.

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By in Canada,

Interestingly enough, the BWE doesn't intrigue me that much, but that alternate build of the aggregate plant - that looks pretty awesome. I'd love to build that (if it works).

Nice review, and the pictures look good.

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By in Finland,

Great shots as usual. Does anyone know what the "MK III" label on the excavator stands for? Is it a reference?

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By in Germany,

too me, the model looks similar to machines used in Germany to harvest 'brown coal' at the surface. And in fact, they dig rounds but not from the ground, more by digging into vertical walls of sand+coal. Now it may be pretty tricky to simulate something like that with Lego for easy pickup.

A link to a picture of what I mean is here:

http://www.urlaub-und-reise.magazin-2011.de/02/17/9010395-kuenstliche-seenlandschaft-in-der-lausitz/

so from that point of view, I consider the model quite representative and may look forward of getting one...

EDIT: in fact, looking at your images above, you found similar pictures as well, but as said, the idea is to dig into vertical walls, not pick up rocks/earth from the ground

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By in United Kingdom,

Yes that is undoubtedly where the inspiration came from given this one will rotate and dig at the same time but as you can see the design of the body is quite different.

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By in Canada,

I don't own many Technic sets but have contemplated this set. I recall reading several years ago on Brickset about 8043 http://brickset.com/sets/8043-1 and that after its initial release Lego produced a second version or fix (similar to Wall-E). Not having a large amount experience with Technic builds I think I will wait to see if a new version is released to improve functionality; I do regret never picking up 8043.

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By in United States,

I am confused. Why couldn't they include more than one motor in a 4000-piece set?!

I don't really like this set. It doesn't look very good, and it doesn't seem to run properly... what's the point, then? Plus it's too big to display, and very expensive.

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By in United States,

I wonder if those yellow circular gear parts could be use to make a motorized turntable for trains..... of course, their would be major track overhang due to the small size of the ring, but could it be done?

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By in United States,

It's awesome watching a LEGO thing this big be able to move at all. It can't have been too hard for them to have made it with a second motor, though, could it?

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By in Netherlands,

Thanks for another great review! I've just pulled this of my short list of 'wanted sets'... But, thanks to your reviews, the Volvo EW160E is now on that list :-)

Can we expect a review for the 42054 Claas Xerion any time soon? I'm doubting about that one as well....

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By in United Kingdom,

I'm building the Claas now. You needn't have any doubts about it.

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By in Denmark,

^When do you expect to post the Class review?

Hope it will be positive - need to buy something!

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By in United States,

The B model for this set (mobile aggregate processing plant, I believe) is actually more enticing for me! But this still ranks lower in priority for me to get this year than the Claas. Great honest review of the usability of this set.

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By in Netherlands,

@Huw: Thanks for the heads'up. Still curious towards your review though. :-)

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By in United States,

This set is really a monster, wonder how that would look in my room....

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By in United Kingdom,

Claas review might be up tomorrow. I've completed it now, rain is forecast tomorrow, so I should have time to photograph and hopefully write something up as well :)

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By in United Kingdom,

How is the weight of the body supported and centred over the ring gear? Is there a big technic turntable at the centre of it all? And I think I can see dark grey pulleys, perhaps rolling round above the teeth or in the groove of the ring gear? I'd be concerned about how much weight that can bear before cracking the inner part of the ring gear...

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By in Poland,

@Joefish:Yes, there is a turntable in the center. Pulleys too.

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By in New Zealand,

@ TransNeonOrangeSpaceman:
42009 MK II Mobile Crane was designed by Markus Kossman, hence the MK in the set's name. I would expect that Markus Kossman designed the BWE as well, given that the set has MK III stickers.
Both sets have multiple functions powered by one Large Motor.

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By in United States,

Some one may have said it already but I think it is based off a Sandvik PE100 Bucket wheel.

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By in Germany,

I prefer the B-Model. Its a pity that LEGO does not include the instructions for it.
Btw, many thx for this informative and objective review.

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By in United Kingdom,

The instructions for the B model will be available online soon.
I've been really excited about this set since January, it's just a shame it doesn't function slightly better. I'm still going to buy it along with the other 2 new technic sets this weekend. There is a video on YouTube showing how somebody has built in full RC functions and instructions on how to do it, it doesn't look too difficult either.

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By in United States,

"I don't suppose real BWEs exactly race across the quarry, though, so it's probably realistic."

Now I want to see BWE races! Talk about extreme sports!

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By in United Kingdom,

I saw this set in TRU a week or so ago, and I was quite surprised by the size and its relatively low price (especially for its size and piece count), but I suppose a large number of those pieces are connecting pins and bars, which maybe make Technic seem better value on a £:Parts scale.

But this was a good review in as much as I enjoyed looking at the model and techniques yet made it rather plain that the model has faults, and at that price point I think most people would want as faultless a model as they can get. The forward lean of the model is concerning (could it potentially damage something?) and the lack of power to the wheel is a bit worrying too. It does sound like it's potentially over-engineered to the point that so many gears and functions are used that the system just can't handle it too well.

Maybe I'm wrong, maybe I'm cynical, but I can't see this set doing too well. It strikes me as the sort of set you look at, think looks nice and then focus on sets with better working functions or more... practical sizes for display.

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By in United Kingdom,

Here is a link to the full RC mod version on YouTube.

https://m.youtube.com/watch?v=D1rzv_eLAY8

The mods don't look too difficult to implement if you have the parts and spare motors. The results look excellent. Even the little white dumper truck has RC!!!

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By in Poland,

Isn't this set powered by XL motor? I think i see it on the photos.

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By in United Kingdom,

Yes

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By in Guernsey,

Thanks for a great review, Huw. People's early concerns about the single motor and the machine's overall weight (check out that lean!) seem to have had some foundation, unfortunately.

Having now seen some reviews, and some pictures and videos of this thing in action, my enthusiasm for the main model has lessened but the b model looks more enticing than it did at first. I just wonder what percentage of the piece count is used in the b model? It looks some way smaller than the main build, at least to my eyes.

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By in Russian Federation,

As for the very badly moving bucket wheel - please check that you`ve placed the 1/4 circle gears identically in those 2 parallel circles of the wheel. Instruction doesn`t pay much attention to it, but 4 linked pieces don`t truely form a perfect circle. I firstly assembled the wheel with 45 degree offset for 1/4 circle gear joints between two circles (that is expected to make the structure more robust) and I could barely move the wheel of unattached digging arm after that. With this displacement, circles don`t match and their flaw shapes add friction by wheel rollers and also the wheel gets moved to the one holder side after 2 turns adding even more friction and that periodical scratch.

If placed properly, it turns like a charm.

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By in Germany,

An interesting build to see the methods used, but really I think it will probably get dismantled pretty quickly and put back in the box and on ebay. It promised so much, but I think the motorised drive needs a lot more thought. No motorisation of the up/down bucket control is a also let down, and the gearing isnt as powerful as it needs to be. I wonder if they had added this how that would have impacted the price point?

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