[TC22] Mini Rough-Terrain Crane

[lmdesigner42]

Hi everyone. I had an idea some time ago to make a miniature version of 42082, using 49.5 mm tires, but didn't make much progress on it. Seems like a perfect fit for this contest though! The approximate size is 13x12x45 studs when folded, so it fits in the required volume. Planned features are:

• 4-wheel steering
• Synchronized outriggers
• Superstructure rotation
• Boom extension/elevation
• Winch

Below is the very rough chassis:

More updates on the way.

Edited May 4, 2022 by lmdesigner42
changed picture links

[lmdesigner42]

I have built the boom and roughed out the chassis and superstructure. The extension height is pretty satisfying!

There will be two knobs on either side of the turntable, one to rotate it and the other to extend the outriggers using a central shaft and lots of gears. Not much space available.

[mdemerchant]

How are you extending the boom?  I don't see a gear rack or any string.

[Jurss]

Interesting, that build of boom is something new, at least for me. Looks also good, really technic.

[2GodBDGlory]

Yeah, the boom is really nice! It looks strong, and the half-stud sides help keep it compact.

[lmdesigner42]

Sorry for the very late replies, need to turn on my notifications.

@mdemerchant The boom will be extended by a piece of string (to be added) running over the top of the boom, inside, and then tied to the base of the extending section. There's a millimeter or two between the beams which allows the string to fit.

@Jurss @2GodBDGlory Thanks for the positive comments on the boom! I borrowed the alternating triangle technique from a mobile crane I saw some time ago with multiple extending sections. I am pretty happy to have something sufficiently strong but only 3 studs wide.

 

Current progress update:

Outriggers are now working, all 4 are synchronized and can lift the chassis slightly. I'll need to work a little faster this week to finish in time for the contest.

[lmdesigner42]

All done! Final size is 14x14x45 or 8820 cubic studs. Time for the entry post.

 

Features include:

4-wheel steering – Smooth 4-wheel steering with steering shaft running through the center of the chassis. Wheels are just the right size to allow a close fit with other chassis parts.

Synchronized outriggers – 4 outriggers controlled with a black 12t gear on the left side of the chassis with a 1:1 ratio. Somewhat stiff, but the outriggers lock into the lowered position and lift the chassis slightly.

Superstructure rotation – Controlled by black 12t gear on right side of chassis. Also rather stiff, since a 3L axle with stud is used to add friction.

Boom elevation – XL linear actuator gives more than enough range of motion, a bit over 90 degrees.

Boom extension – Dual winches are attached to the inside end of the extending section, wound in opposite directions. One string used for retraction goes through the back of the boom, the one for extension runs over the boom, around the end, and inside the top. Turning the 12t gear on the side one way retracts one winch and extends the boom, turning it the other way pulls on the other winch to retract the boom. A ratchet is included to prevent collapse when extended.

  

Main winch – Includes separate ratchet and custom hook setup, strong enough to lift 9V battery box with batteries and PF L motor with the boom extended when at the right angle. The low weight of the crane is a greater limiting factor than the strength of the boom.

Exterior details – Cabin with seat and control sticks, headlights, taillights, raised engine section, and hazard stickers.

Size comparison with 42128:

See more pictures at https://www.bricksafe.com/pages/lmdesigner42/mini-rtc

[Jayden]

very nice crane but i think you need an entry number - 25 in the entry topic

[1980SomethingSpaceGuy]

We need a special category for cranes in this TC !  
I like the general look and feel of this one, I think you really did a great job with that boom structure.

[Erik Leppen]

I really like this one. Somehow I especially like the shape of the superstructure. I think this angled shape is just how cranes like this actually look. It's a rather minimalist shape, but that's exactly how real cranes look as well.

I also really like the truss-like boom structure. Nice find with the triangles, and the extension/retraction mechanism is just genius. Bonuspunt for using a nonstandard way to control it, rather than the same-old long gear rack.

The boxy shape of the carrier also works, but I have the idea that is'a bit big in compraison to the superstructure. A somewhat skinnier carrier (more ground clearance) would have made the model look even more realistic, I think. But that would be my only remark. The gray color contrasts nicely with the yellow/black combo of the upper part. Also, the boom has got a quite nice range. Great entry.

[lmdesigner42]

Thanks for the positive comments!

@Erik Leppen the real rough-terrain cranes are very minimalist, which looks great but leads to rather tight builds for Lego versions. I agree that the carrier looks slightly too bulky, this could have been fixed maybe by going to a larger scale (62.4 mm wheels) or using bricks and plates for the chassis.

[mitx2529]

this crane is amazing!

the chassis is functional in small size

especially the angled of the boom is very real 

 

great moc

[lmdesigner42]

Thanks for the praise @mitx2529, putting functions in a small chassis is hard. There's a lot of other good examples of compact builds in the other contest entries.