For a while I've wanted to build a working 2-stage mast on a forklift, this scale is just about big enough to make it happen and only look a bit too bulky.  Mostly so far I've been thinking about what parts to use, but the last couple days I began fitting it together in Studio.

The tire size limitation led me to a heavy duty forklift; smaller ones usually run big front, small rear tires, at this size they use 6 tires with 4 on the front axle.  So scale works out to about 1:24.  Same as the Mack Anthem and car transporter.  Might need battery counterweights, but one goal is to be able to lift the Anthem's container.  From there I pulled the basic dimensions (20 stud wheelbase, 20 stud tall mast).  19 stud helicopter blades are a little long, but there's really not a lot of middle ground there, straight from 8 to 19, brick building would likely weigh too much.

To help keep the design organized, the mast stages are colour coded, yellow ones attached to the chassis, red as the first stage, blue as the second stage that actually holds the forks.  Very likely going to be all black in bricks (no blue 7 length liftarms with alternating holes, yet...).  Yellow and blue slide in the red parts, which have an H shape.  The forks also move 3 studs side to side, I've seen on real ones they have some mechanism to manage this but I don't have ideas to allow that, other than maybe winding string all over the place.

I wanted front wheel drive with a differential, but also keeping the mast as far back as possible, so the diff couldn't go between the tires.  It's going to be a fake engine, no motorization.

I'm not happy with how prominent the small linear actuators are, hopefully once it has a body that'll be less of a problem.  Planning to make them diagonally downward, but I haven't tested what triangle gives reasonable range of motion.  The raising is done by the worm onto 20T gear at the back, through knob gears, and then the new city screws cause I've wanted an excuse to play with some.  They're a bit annoying to convert into the Technic grid; this is a 5 stud deep setup to pinholes on the upper/lower studs.  Which feels like a lot for a piece that's a 2 stud cube.  Once I get some in hand I'll be able to try some more iffy options, like only attaching it from one side, and see if it's still able to run smoothly.

Right now I'm just getting the basic mechanisms in place to make sure they'll fit.  Once I'm fairly confident I have the functions packed into the space, I'll need to build something in bricks to test out the gear ratios.  1:20 on the worm gear is concerningly high, 5 full rotations per 2 studs the forks raise.

A very interesting project. I always thought that the scale of model 42078 was approximately 1/20-1/21, the same as 42128.

Nice idea of using the wing/prop panels as forks!

Not sure if I properly understood your doubts with the worm screw, but maybe knowing that you can stack two black cubes helps?

Then you have more studs to support whatever is attached to it.

Nice use of rhe blades but will they hold the weight of a container?

39 minutes ago, Divitis said:

...with the worm screw,   maybe knowing that you can stack two black cubes helps?...

I didn't know that!  I'm going to have to order some.

Great idea, I love your progress so far.

7 hours ago, Divitis said:

Not sure if I properly understood your doubts with the worm screw, but maybe knowing that you can stack two black cubes helps?

Then you have more studs to support whatever is attached to it.

Basically this: 

The worm is on grid. The connection points are at the two black squares, and the space in between them is unavailable.  The 3x5 opening is about the most I can afford it before it runs into other things. The closest holes available above/below the cube are spaced 5 apart (on the right, using plates with pinholes above/below).  If it's turned sideways then the underside studs line up with a jumper plate, but that makes something 6 plates tall in a 3 stud (7.5 plate) gap so there's no space to do anything at the top. 

Like the simple solution is use the antistud pins, I'd be confident in the strength of this but they're 1/2 plate too thick to fit the 3 stud space.

I do have room to continue outward from here, so maybe I can put a 3l bar through a Technic pin and into the 1x3 round plate... not sure that has anything to stop the 1x3 from sliding away from the worm though.

Looks kinda janky but maybe this is all legal?  If I repeat it for the higher row of studs even better.

I much prefer this 'balanced' style where it's attached to all 4 corners, but maybe with 2 cubes, using 2 corners multiple times is good enough.  The motion is applying mostly vertical force on the cube but with a small torque, so it's more a question of whether it could work loose from stud connections if only the top or bottom of the cube was attached. So thanks for that tip, I'll see if I can acquire 2 cubes.

Edited July 5, 2024Jul 5 by Stereo

The left one should help visualizing the geometry of the cube, but of course it's an illegal and impossible construction.

The right one is a quick attempt at bracing. Depending on the forces you're dealing with you might want to connect it to the bottom of the 5x7 frame too, as now it's only secured by friction on the vertical axle.

 

@Stereo Looks like i misinterpreted your earlier post. This should be more like what you're looking for, using the .2 offset of the headlight brick.

Edited July 5, 2024Jul 5 by Divitis

Great idea for a project; I look forward to the progress that you make. I'm also interested to see how the new worm screws work with the lifting mech. Good luck.

Batmobile has temporarily lost its wheels in service to testing the steering, looks like I can just about clear the 5-wide frame and coincidentally get pretty good Ackermann as well.  I did have to turn it 180 from how I thought it would work.  The steering stop is the 3L beam behind the gear rack.  Though on closer inspection the rack also hits the 3L axle with stud the wheel mounts to.

Edited July 5, 2024Jul 5 by Stereo

That is an interesting way to do it. Looking good so far.

Good, that You are aiming for correct steering geometry, and also wings for forks are interesting.

I have been waiting for these to arrive in the mail, and they're here now.

Got a few extras, in case I think of a reason to have a 30 stud long corkscrew.  Maybe see how high the forklift can go since nothing in the rack is length-limited, it'll just get heavier and more bendy. 

When they're attached together perpendicularly they mesh on-grid so maybe they're suitable for some of Henry Segerman's weird rack mechanisms.  Connected with axles so they're only good for compressive force to whichever end of the corkscrew is rigidly mounted, no tension, but that's not a problem for me since the chain already limits it to handling downward loads on the forks.

 

On the design side, hand of god steering is no trouble, but if I want a working steering wheel, it's gonna need to loop over the fork control, under the fake engine, and then back upwards to the cab.  So I'm not quite sure that'll work.

 

Don't think it'll be useful to me, but if you have jumper and regular studs like this, the worm can engage them decently.  Another pair of these on top and you'd have a 6 plate tall mechanism, which is probably worse than just using the cube.  Maybe good for if you want a 2 plate thick thing to be moved by a stationary worm though.

Edited July 16, 2024Jul 16 by Stereo

Very nice progress.

Building IRL has gone pretty well.  Needed one small modification to run smoothly.  The functions work - elevation has the full 20 studs and without the cab on, it can tilt quite far back.  I need to take a few things apart to get the other tires, and some parts to finish up the steering, so I paused here.

The only problem with the screw mechanism is if you keep turning the knob when it's at the bottom, it'll push the screw off the axle, as the top end isn't captured by anything, so there's no hard stop.  I can see some fixes but I need to look closely at it and make sure it won't run into any moving parts.

 

I also realized my 3x7 black panels have Gravedigger stickers on them, so it might end up more dark bluish gray than black on the body.  So that's another part to try to find more of.

Edited July 23, 2024Jul 23 by Stereo

IMO one of my most interesting MOCs I've encountered. Definitely you have high chances to win this contest.

Thanks, interesting mechanisms are my main motivation to build things, more than aesthetic.

Full height with the forks.  Interesting problem with the helicopter blades.  They came in 42125-1 and have never had any playwear, but both of them are curved the same way, so I guess it's due to the molding.  But since I mount one facing "up" and the other "down", the left fork curves down and the right one curves up.  Not much I can do about that.

The steering link to both hand of God and a steering wheel is probably unnecessarily complex, and limits it to a 3 cylinder fake engine. 

I didn't really design this with a linear build order and it's leading to some interesting dependencies.  The front cylinder of the engine can't be installed until the cab is on, because the axle at the front of the steering slides forward through a beam at the front of the cab, to secure its other end.  The bottom of the cab is only attached to the top, so I have to build the entire cab at once and drop it in, then push this axle through, which locks it down.  The engine's only temporarily placed because it drops in on top of that, but I thought it was worth making sure everything rotates.  Anyway, there are some parts for the cab that I had to order from Bricklink, so I'm waiting for those to arrive before I can continue.

The Grave Digger panel is likely here to stay because it's got another of those dependencies.  It's attached to the frame from the middle of the chassis, and that can only be done before the worm gear that controls the elevation is in place.  It was pretty inconvenient to take that out, and reinstall it with the panel partially covering it up.

This shows about how much slack there is once it's loaded, the mast has to be tilted back this much for the forks to be around level.  It does ok holding up my organization bin with unused parts.  The weak point in the lift mechanism is the chain, which unlinks itself, at much less weight than what it takes to bend the blades.   I was testing to lift the Technic Jeep set while holding the back of the forklift down, when I broke the chain.  I guess running two chains would help, but then again it's Lego.  Better if something unclips than bending parts.

Edited July 24, 2024Jul 24 by Stereo

Some people have done tests, and they show that putting chain links with their "teeth" facing outward give much better results at torque handling. Maybe flipping chain links would help. 

Let's say "done for now" because an order I placed 3 weeks ago for a 1x5 thin purple beam and some 1x7 hasn't arrived yet, but everything else has.

https://bricksafe.com/pages/Stereog/heavy-duty-forklift for several more pictures in the current state.

The Purple 32009 double bent beams inspired the colour scheme and shaping; I got a Technic Competition set on sale in 1999 and haven't used them in any MOCs yet.  Unfortunately the colour only ever got used in around 10 sets and the part selection is small, with most of them being rare.  So white and yellow manage the more complicated shaping.

Hoping for a sunny day to get some clear photos for the actual submission post.

Despite using a Technic figure chair, there's unfortunately not enough headroom or legroom to put one inside.

Features:

- raising and lowering mast by 20 studs, using gear knobs on either side near the back tires.

- tilting mast forward and back, using gear knob at the front left tires.

- manually slide the forks side to side for working with different loads.

- steering with Hand of God from above the engine cover, that also moves the steering wheel in the cabin.  Uses ackermann geometry and reaches near 60 degrees on the inside wheel, for good turning radius.

- 3 cylinder fake piston engine behind the cabin.

- engine hatch to maintain the engine, and rear hatch for storage, fuel, or adding extra weights.

Looks really cool, love the color scheme!

Very nice! 

The color scheme really does make it stand out

That looks great, the purple really makes it stand out :)

More pictures in the Bricksafe album.

It can lift the cargo container from 42078, ish.  When it's lower, it's not got enough weight to counterbalance it, but at full height the weight is in a more reasonable spot.

To take photos outside, it's required to pay the pet tax.  She pretty much immediately walked between me and the subject.

Looking good, the color scheme is indeed eye catching!

1 hour ago, CK28 said:

Looking good, the color scheme is indeed eye catching!

I agree, very good.