[MOC REVIEW] Designer Han's Dragline Excavator

[Blakbird]

Designer Han is well known for releasing excellent Technic models with full instructions, usually once a year. This year's epic offering is a dragline excavator, a subject I'm not sure I've seen used in a MOC before, and certainly not in one with full instructions. This is a beautiful and enormous model in unusual green and orange color. There are a total of almost 2200 parts and almost 500 pages of instructions.

But this is not just a good looking model, there is a whole lot going on inside as you can see in this cutaway render.

I'll step through the features one by one. Altogether there are 9 motors, 4 IR receivers, 2 battery packs, and an extension wire comprising the Power Functions components. You can see how compactly the rear 7 motors are installed. They are far behind the turntable which does much to balance the heavy boom. In this case, neither wires nor axles run through the turntable. The entire carrier has a self contained electrical system with its own battery and receiver.

The drive system is very simple. An L motor powers each track independently from a separate channel allowing skid steering. Each motor is geared down 40:1. The use of worm gears does produce some friction, but also keeps the model from rolling backward on a slope. The drive system has plenty of power and is very slow, but this seems perfectly scale accurate.

The slewing system uses an unusual tandem M motor configuration. The motors are connected to the same channel and operate in parallel to drive a pair of worm gears. Two separate spur gears drive the turntable ring gear with a total reduction of 78:1. The slewing has plenty of power but operates a little bit too fast in my opinion. This causes a bit of wobble in the boom when slewing. This can be reduced by using a speed control remote and accelerating and decelerating gradually.

A pair of main winches are driven by powerful XL motors. Each drum has a separate XL motor geared down 3:1. The forward drum powers a cable running nearly horizontally which drags the bucket. The upper drum powers a cable running along the boom which is used to lift the bucket. Both have plenty of power. In practice, they need to be operated together to get the bucket into the proper orientation.

In order to actually drop the bucket, Han developed a unique freefall system. This system uses a pair of M motors to drive a gearbox. When the gearbox is engaged to the forward gears, the XL motors are linked to the cable drums. When the gearbox is engaged to the aft gears, the Xl motors are decoupled because the aft gears don't connect to anything. This allows the bucket to freefall, backdriving the gear train (provided it is heavy enough). It works pretty well, although it the cable gets wound too tight or jams then some external force might have to be applied to help it along. I have found that I almost always use both freefall systems together rather than independently, though I am far from an expert operator.

The final motorized system is an M motor powering a cable drum which lifts the boom. The boom is very heavy and I was skeptical that an M motor would be adequate for the job, but it not only has ample power but may actually move too fast for scale. The motor drives the drum at a 3:1 ratio, and another 3:1 comes from looping the cable around pulleys 3 times. The upper axle in the picture is not geared to the others. It holds the pulley axle and just follows along with the cable.

Han mentions in his description that the model is tricky to operate, and he's not kidding! The controller is not very intuitive and a lot of coordination is required to get the excavator to do what it needs to do. Part of my initial difficulty came from the fact that I was thinking of this more like a crane and there had the boom at a very vertical angle. However, this is actually an excavator and the boom really operates at a nearly horizontal angle. In this orientation it is much easier to control. It is really fun to use once you get the hang of it.

A careful study of the way the cables are connected to the bucket reveals some secrets about the level of control you have with only two cables. The upper cable carries the weight of the bucket, but it is not centered over the center of gravity and therefore the bucket would naturally tilt forward and dump if there was no other cable. The way to make it dump is let the drag cable go slack. The drag cable does not just connect to the front but also loops up over a pulley and back down the the front of the bucket. When the bucket is on the ground, the angle is fixed and pulling the drag cable draws the bucket toward the excavator. However, when the bucket is in the air the drag cable adjusts the angle of the bucket. If you want to lift the bucket, you need to first set the angle with the drag cable and then operate both winches together to raise the bucket without changing the relative tension between the cables.

Han's instructions are excellent as usual, but perhaps different than what you are used to. He uses an older version on LPub that does not use LDView to draw the images, but POV-Ray to render them. This results in a different visual feel. He adds lots of annotations to explain the wiring, the operation of the model, and lots of other building tips. I didn't run into any difficulties building it. If I have any complaint at all, it would only be that the power switches are difficult to access.

To summarize, I highly recommend this unusual and entertaining model. It is not cheap to build and it takes up a lot of space, but the results are well worth it.

Edited August 8, 2016 by legolijntje
Fixed image links :)

[jorgeopesi]

It is very interesting to see crane mechanisms , a lot of to learn. I don´t like to use worm gears like this, do they work well?.

[Alasdair Ryan]

Can you post a picture of it in your collection?

Judging by the photos I think this is probably his most complex moc to date.

[Blakbird]

Can you post a picture of it in your collection?

What would you like to see next to it? My LEGO room is so full that I can't stand back far enough to take any pictures in the room, so I will have to bring the model out to a table.

[Alasdair Ryan]

What would you like to see next to it?

You in a sexy pose?

How about some of the other technic cranes....what is the size difference to the crawler crane off a few years back?

[DrJB]

Impressive as always ... but I do not have any green parts :(

What would be interesting, and maybe that's a question for Rebrickable, is what sets one can start with that'll contain 7-80% of the parts?

[afol1969]

What about building in another color? I haven't much green and orange parts....

Greetings

Alex

Edited April 27, 2015 by afol1969

[OneMoreRobot]

Currently building this model, however I shall use SBrick to control functions & add some PF lights.

Enjoying the unusual colour scheme.

[Theo van Vroenhoven]

What about building in another color? I haven't much green and orange parts....

Greetings

Alex

I am planning to build it in red.

Replacing all the green and orange by red is no problem.

[Milan]

Probably his best so far!

[Foggy]

It's a really great model, don't like the colors at all...prefere a red or yellow version..i know yellow is mostly used but i like digging machines in yellow :D

Well would be nice to see this beast beside both 8288 models, that i own, so we can have a comparison and maybe biside 42030 or 8275 that many people here i think have in their collections. ...

Appreciated ;)

[ritztoys]

Blakbird,

You have given all Technic Builders an excellent review of Designer-Hans' crane, especially the cut-away views with great explanations!

Everyone will enjoy building this model, you just made everyone....... :wub_drool:

The details you provided are 'spot on', as you said this model is "well worth it". :thumbup: ( No matter what color is chosen )

Edited February 12, 2015 by ritztoys

[N-4K0]

Amazing construction. The cut-away views really makes one understand just how complex it is.

The color combination of green and orange makes the machine just the more eye-catching.

Great job on this model, Han, thumbs up!

And great job on the instructions. I haven't looked at them, but I imagine it's a good piece of work to make them.

Edited February 13, 2015 by Error404

[Karle]

Nice MOC and helpful review. Where can I get the copy of the plans.

[dougstar]

<p>http://www.designer-han.nl/lego/

Is were you can find the instructions Download

Edited February 13, 2015 by dougstar

[Blakbird]

Here are a few more photos showing the build. I didn't post them earlier because my renders are much better quality. Here are the parts and a close-up of the massive Power Functions content:

How about some of the other technic cranes....what is the size difference to the crawler crane off a few years back?

Well would be nice to see this beast beside both 8288 models, that i own, so we can have a comparison and maybe biside 42030 or 8275 that many people here i think have in their collections. ...

Here are a couple of shots next to 8288. As you can see, Han's excavator is much larger and the boom is much more substantial, although the 8288 can match the overall height in B model mode:

And great job on the instructions, Blakbird. I haven't looked at them, but I imagine it's a good piece of work to make them.

I had nothing to do with the instructions for this model; the praise all goes to Han. I just did some renders.

[Foggy]

Thanks ;)

[N-4K0]

I had nothing to do with the instructions for this model; the praise all goes to Han. I just did some renders.

Ups edited my post

[jantjeuh]

I see Blakbird had to substitute some rare parts for more common ones

[designer-han]

First, thanks to Blakbird for reviewing my Dragline Crawler Crane MOC; and even more with an objective approach! I am very glad to read that the model meets your standards; and they are high IMO, so meeting the expectations is not easy. As well I am fully aware that every next MOC I design sets even the bar a little bit higher in the AFOL field out there. :-)

Regarding the colors; I choosed to use an unusual color scheme, but in The Netherlands the BAM company is well known for these colors. In daily life I see multiple of these cranes outdoor when travelling the work.

I agree the slewing is a little too fast; but gearing it down was hardly impossible within the superstructure (space and reliability in operations; e.g. I did not wanted to end up with crunching gears now and then).

Finally, is this my most complex MOC? No, I do not think so. The Prinoth Leitwolf took much more hassle to get all functions packed into the chassis and to design. However, the Dragline is probably #2 in row.

Edited February 13, 2015 by designer-han

[Edwin Korstanje]

I love it Han :thumbup: .

I think this is one of your best MOC.

[designer-han]

I love it Han :thumbup: .

I think this is one of your best MOC.

:-) Should I leave the crane 'assembled' for LEGOworld later this year :-)

[Blakbird]

I see Blakbird had to substitute some rare parts for more common ones

I could not find any 9L orange liftarms so I used green which actually looks fine. For the wheels on the top of the green boom, I am still waiting on my orange parts to arrive from Finland. I have not ordered the 6L green tiles yet for similar reasons. I will get it done right eventually.

I agree the slewing is a little too fast; but gearing it down was hardly impossible within the superstructure (space and reliability in operations; e.g. I did not wanted to end up with crunching gears now and then).

As I was building it I was thinking that this model would be a pretty good use of SBrick which would allow several things.

• Not only would the slew speed be proportional, but you can actually program the profile so that the slider end point is less than 1, and therefore max speed is less.
  
• You could arrange a more intuitive control layout with some graphics to show the operator which control is which.
  
• SBrick does not offer this functionality yet, but I imagine eventually you will be able to use formulas to combine channels. For example, I'd like to see a control which ran both the drag and lift motors at the same time in opposite directions for pulling the bucket along the boom.
  

[Edwin Korstanje]

:-) Should I leave the crane 'assembled' for LEGOworld later this year :-)

Offcorse Han,

Don't take it apart. I now that the plans for LW 2015 to make just as last year a big digging site an that Legotrucks, Konajra, Jurgen and others are making stuf like yours .

[LEGO Train 12 Volts]

Wow this huge MOC is a real masterpiece! :wub: