[MT] Three-axle compact crane

[Erik Leppen]

This is (to become) my entry for the Model Team competition. It is a city crane or compact crane. On day one of the competition I made the choice for this subject matter. City cranes are interesting because they don't have a cabin on the carrier - only on the superstructure. Therefore they can be shorter and can manouver tighter places (which makes them suitable for tasks in the city center - hence their name).

This is the first presentable version of my entry for the model team contest. It is not modeled after a specific make or model, but it is inspired by various existing models. The colors are based on what I had in my collection and personal taste.

The size is 45 x 15 including all sticking-out parts. Height (in transport mode) is about 17 studs. Height in crane mode is about 54 studs. The "bulk" of the carrier is 34 x 12. I want to stay within the limit including all parts, so that there can be no discussion about what parts do or don't count for the size limit. The only stickers are the licence plates, these read AP 5342 and are from an official set (I don't know which one).

I'm also keeping up a digital version, hopefully I can get to creating instructions for this one when it's done. Currently, the digital version is fairly up to date and has about 1300 parts.

Functions:

• knob-operated four-wheel steering
  
• knob-operated raising/lowering the boom via LA
  
• knob-operated rolling/unrolling the hoist
  
• knob-operated boom extension
  
• manual slewing
  
• manual outriggers
  
• manual opening engine bay
  

It is not finished yet. Feedback, suggestions etc. are very welcome :D

[Zerobricks]

What an interesting crane an color combination. I suppose this is one of the first entries for the competition?

[TheItalianBrick]

Hello! as I've done many cranes I have few suggestions if you like:

1) increase the size of the wheels, and make the crane with only 2 wheel axle, this will give you better proportions, and more realism as your crane looks "flat" at the moment.

2) no need of a second seat, and it doesn't look real.

3)wider boom, as now looks like a stick, or fragile, and not proportionated with the rest of the vehicle.

4)at the end of the boom (extendable section) there is a sort of brown thing made with curved tiles, is that necessary? cranes normally has a 30 degrees inclined section, thinner aswell.

5)not sure if you did this exercise, but it's always good to make a research on what vehicle we would like to "convert" in LEGO and study it, from all views, etc etc. Looks like you have no references!

Overall it has it's shape, and I quite like it! But I'm sure you can improve a lot and have a very good entry! :thumbup:

Here a ref: http://static.mascus.com/image/product/large/717963ba/grove-rt700,64e341a0.jpg

[efferman]

http://www.autojerabymalina.cz/cz/pujcovna-jerabu/demag-ac55/

Everything right on eriks model

[TheItalianBrick]

http://www.autojerab...abu/demag-ac55/

Everything right on eriks model

In fact I asked if he had some ref for real model. You (he) simply picked a quite unconventional one. Plus looking at the link Erik still needs to get the proportions as his wheels are a 2/5 of the height, where on the one you linked it's nearly 3/5 if not more!

And after all, I understand it's nice to participate with an entry, but we all push for the best model we can, if you want to impress then the 2 axle crane has more chances IMHO! :tongue:

P.S. Efferman do you know the need of the second seat?

[jantjeuh]

Love the colours you've chosen!

[Milan]

Hello! as I've done many cranes I have few suggestions if you like:

..............

Erik is one of the best crane builders! Check his BS gallery, he knows what he is doing.

There are few few city cranes that has two seats in the cab, Demag for example.

Reason for the second seat is simple...the crane can carry one more worker.

About that inclined section, it can be assembly-jib or fly-jib, and it can be set to 0, 15, 30, 45 or 60 degrees, depending on the need and the type of jib, of course.

Erik wrote that his model is not moddeled after any real crane, so the wheels can be this small, and the shape of the crane can be made after his desire.

To me, it looks like a Terex-Demag, just what Erik is specialized.

Dont forget, this is a city crane, it does not need bigger wheels.

AT Cranes do need big wheels, as they are sometimes of the road.

Overall, great entry.

[efferman]

The second seat is for an assistant which took the payload on the crane hook, or simply for the lunchbox of the cranedriver.

For the tires he could maybe try the new 49,5x20 . but it is eriks decission

[Rishab N]

Great work! This is shaping up to be an interesting competition

[Erik Leppen]

Hello! as I've done many cranes I have few suggestions if you like:

[snip]

Overall it has it's shape, and I quite like it! But I'm sure you can improve a lot and have a very good entry! :thumbup:

Here a ref: http://static.mascus.com/image/product/large/717963ba/grove-rt700,64e341a0.jpg

Thanks for the comments. I think you're right on a few aspects.

1. I'm not going to change the subject of choice ;) (I actually wanted 4 axles but that was over the length limit and would be too symmetric, thus less exciting). But do note that the reference you are posting is an all-terrain vehicle. This is a road vehicle. So naturally it has smaller wheels and a smaller ground clearance.

2. Some real cranes have two-seat cabins, and I just consider it logical that a crane operator can bring his/her assistant along to the construction site. Cranes with carrier cabins have two seats too. Also I personally thought it looks better :)

3. Good point. I could widen the boom. It remains to be seen if the LA will fit (as it has to fit between the "blocks" on the turntable. But I might be able to move it a half-stud sideways, which would enable it to be wider. Might be worth an experiment :)

4. I have thought about adding a jib, but haven't yet found a way to do it in a non-ugly way. But looking at references I see some cranes have closed jibs (rather than lattice jibs) so it might be feasible. Who knows.

http://www.autojerabymalina.cz/cz/pujcovna-jerabu/demag-ac55/

Everything right on eriks model

I think I'm heavily inspired by my own AC70 of ages ago, but it has more likeness to this AC55 than I'd imagined :P Thanks for finding the match :D

In fact I asked if he had some ref for real model. You (he) simply picked a quite unconventional one.

Maybe the place where you live has other vehicles than our place, but if I do a google search for "city crane" then what I get is close to what I built ;) So I don't think it's as unconventional as you might think :)

But even what if. As I said it is not a real vehicle. It's merely a realistic vehicle. One that could exist. Not one that necessarily exists.

the 2 axle crane has more chances IMHO! :tongue:

I saved your image for future consideration :D (But not for this compo.)

Love the colours you've chosen!

Thanks! Yeah I'm quite happy with how it turned out as well. (But I like playing with color combinations.)

Erik is one of the best crane builders!

[snip]

Overall, great entry.

Heh, thanks :D

Yes, I might add a jib, if I can get it to fit and look OK.

For the tires he could maybe try the new 49,5x20.

Those might be a good fit, but unfortunately I don't own them (and I don't like the idea of buying parts for a specific MOC. Budget is limited at the moment. But to be honest - I want those tires anyway...)

Thanks all for the replies so far :D

[grum64]

I like this very much

I'll be following it's progress with great interest.

Edited August 25, 2014 by grum64

[aol000xw]

It looks weird because city cranes are somewhat weird, or at least not that common and that is ok but.... anyone knows that amazing computer fans brand? Noctua?

Well, there is a bit of Noctua effect on the crane and the background color does not help at all. I'd love to see it at a more favorable scenario. I like the sleek lines in the superstructure but the black portion of the cabin does not look that good.

Really quick and dirty... and I like it way more!

[Erik Leppen]

I'll be rebuilding the model, using the original version as inspiration. First of all I got the larger tires from 42024, so I'll be using those. The WIP of the new carrier:

I make those photos with my phone, once the model is complete I will be using a proper camera, and take pictures on a better time of the day.

The larger tires made the carrier three studs longer, which can be problematic since the old model was 45 studs including everything. It also sits a bit higher off the ground, which I like. I changed the stairs on the sides to gray, I didn't like the black. Unfortunately I don't have the plates 1 x 2 with ladder in gray, so I used panels.

I might switch to gray rims to reduce the "mass of black" effect of the wheels. I could also use wheel covers, but I don't know if there's any of which I have six.

This however is the easy part. Creating the new superstructure and boom will be the main challenge :)

[Zerobricks]

So far so good! Keep us updated!

[Black-Build]

Looking good already!

[Erik Leppen]

Next-up was the new boom.

As mentioned by the replies, the original boom was too thin (mainly too low). So, per the advice, I increased the height. I also increased the width, and put the attachment point further upwards and backwards, to the boom could be longer. This is close to the real life Demag AC-55City which I use as inspiration.

Increasing the boom size has another advantage and that is that I managed to get a third section in. It won't be controlled in any way, but at least it's there, so the model is more poseable and has bigger reach. The second section is one of the weakest pieces of engineering ever to be found in a crane boom, but hey, it works.

I also increased the mechanical advantage of the LA (moving about the connection points of LA and boom, changing the shape of the triangle formed by boom, LA and frame.) However this comes with the disadvantage that the maximum elevation angle has decreased. The maximum reach is now as follows:

As with the previous version, the boom is off-center to allow a 5-wide cabin. Also, there's almost no bend-through of the boom at the joints of the sections.

The red parts at the end are temporary :) The gray bricks at the end of the second section, I'm afraid, are not. But i might change about some of the colors used.

[MajklSpajkl]

Is the third section of the boom extracted manually or simoultaneously with the second section while turning the gear on the first section? I love how compact the whole 3 section boom is!

Edited September 25, 2014 by MajklSpajkl

[Erik Leppen]

There's no feasible way to control the third section other than manually. There's too much friction.

[jantjeuh]

I think this update is going to be a great improvement of an already good-looking design Curious to see the end result! Good to see you're sticking to the same colour scheme as the original.

Edited September 26, 2014 by jantjeuh

[Rockbrick]

BOOOM shake the room... that is impressive - the base is perfect - be careful with the cab design

[Erik Leppen]

The superstructure.

It's not yet done, I'm not yet happy with some things. Also the cable drum and hook are still missing. I changed the cabin's top and front to light gray because I happened to have the right parts in that color, and changed the windscreen from vertical to slanted. I changed the counterweight from straight to curved, which is closer to reality.

On the carrier, I moved the turntable two studs backwards and completed the engine bay. I also moved the spare wheel to where it is on pictures of real cranes of this type.

Also, contrary to the model team spirit, there won't be doors... also the carrier could use a bit more lights at the sides.

Stuff that needs to be done: front end of the carrier, outrigger footers, some space to store outrigger footers, boom end, winch, hook, controls in the cabin, and general polishing.

[efferman]

looks great. i think this will be my winner

[Rockbrick]

why the two seats?

one would be enough if it you could tilt it up and out a bit ?

[efferman]

the original has two seats too. for the assistant or the drivers lunchbox

[Erik Leppen]

I have built the entire yesterday evening to put the finishing touches to the model, and I am proud to announce that it's finally finished. I'm done! And I'm pretty happy with it.

Just in time, because I was getting frustrated by it. Fiddling for half an hour on a part no one will even notice was pretty frustrating. Just today I thought of a neat way to have the outrigger footers done, a solution of a problem that persisted the entire time, so that one's finally solved as well.

I measured the dimensions, it's 45 x 15 studs including everything. The carrier is 39 x 12.

These are the functions. A pretty decent list, if I say so myself:

• Four-wheel steering - via knob on the back of the carrier
  
• Outriggers - manual
  
• Slewing - manual
  
• Boom luffing - via LA
  
• Boom second stage extension - via knob on boom.
  
• Boom third stage extension - manual
  
• Hoist - via knob on superstructure
  

Also, per the advice on the previous photos, I decided to look for another spot to take the pictures, and the garden presented itself as a perfect opportunity, where the model's colors look much more vibrant than the attic's floor that's almost exactly the Lego tan color.

As you can see I changed the rims to light gray. I experimented with wheel covers, silver 3x3 dishes being the only option I had (the ones from the 10220 VW camper van), but I opted against it because it gave the model a classic look, where I thought a more modern look fits the type of model better. So I went with the lime dots of the prototype.

The engine cover doesn't open. Also I still have no doors, as I saw no good way to add them without harming the look of the cabin. Also the shape of the superstructure forced me to remove the Technic frame inside, so there is no vertical bracing for the part that holds the boom, but it's still pretty rigid. I'm quite happy with that as well.

I moved the attachement point of the LA one stud upwards to increase the maximum elevation angle of the boom.

The part that caused me a lot of frustation is the crane head and the hook. I wanted to use a pulley, but that required the boom end to have a point to attach the string to, and the size of the pulley in the hook meant I couldn't "pack" it for road travel neatly. The current packed position is still not perfect (very little ground clearance) but at least it fits.

I managed to hide the hoist behind the La's attachement point, and I could neatly use the off-centeredness of the constructon to put the driving gears for the hoist at the side, within the counterweight. So that's why the knob for that is on top. There "gear on friction pin" that Technic sets use is not present, the system somehow has enough friction by itself.

Anyhow, I'm happy. This is already a great competition - otherwise I wouldn't have built this. I might do instructions if I have time.