[WIP] Mini Mining Excavator

[teflon]

Hello there!

I would like to show you a (slow and painful) progress on my take on mini mining excavator. Yeah, the Liebherr 9800 R kind. I kinda like the model, the 42100 and Markus is my favorite Technic creator but ... Well, the model is just to big and too simple and I can see some lazy short cuts (having three motors in an arm). And I haven't even mentioned the price, which is hilarious. Sorry about the rant.

So you can imagine my joy when I saw cyberdyne systems' Mini Replica. He clearly showed what can be done in small form factor. However I was wondering if fully motorized version is also possible.

Here starts my story. I've decided to build roughly 1/2 scale model. Yeah, I can be lazy to and dividing by 2 seems easy enough. At the moment I am not into esthetics, it's more about function, so please forgive me some crazy decision.  Let me show you what have I done so far:

I've started with the undercarriage. Simple, two tracks and turntable at the top. Well, the problem is motorization and even the smallest gearing needs 2-3 studs. The results is this:

I am trying to use as little space for gearing as possible. It's not elegant by far:

Motors are hidden in the back:

At this stage, the battery (I am planing on using 2x BuWizz) will be located in the upper portion and cables are going through the center. Is not optimal solution, but solution through the turntable with mechanical connection needs even more space in the body.

Next part was the bucket. I've also choosen 1/4 cylinder, however I've found interesting idea for bucket teeth. I think it works just fine:

The bucket is fully operational.

Next thing was building an arm. I was just trying to mimic the 42100 in 50% scale. However transfer of power at such scale is problematic:

Here is the whole arm:

And this is where I got stuck. I need to fix side M motors, which at the moment are just lying around. BuWizz units will be located at right corners. I am using studded technique just to approximate size. Another problems are universal joint's. They tend to work at angles 0-45°, however the arm swings for 90°. Maybe I should attach motors at an angle. Or do some gear magic. Regarding gear magic - I have to much of them already.

I guess the biggest future problem is how to fit in motors and subcarriage.

Feel free to comment.

[Mechbuilds]

That thing is amazing! Good luck with the project! 

[proran]

Hi! What an interesting project! A lot of motorization in a small scale. I was thinking about building a mining excavator at a small scale for a while now, so I will follow this closely. It is a joy.

16 hours ago, teflon said:

They tend to work at angles 0-45°, however the arm swings for 90°. Maybe I should attach motors at an angle. Or do some gear magic.

Yes, I am afraid you have to switch to gears at the first articulation axis. Similar to the central driveline. In my Mecalac I have to do gears at a couple of places in the arm because of the u-joints' limitations. It is a pain, for sure.

16 hours ago, teflon said:

I am trying to use as little space for gearing as possible. It's not elegant by far:

Here, I would strongly suggest putting the bevel gears in the brackets (these or these). Many people will tell you that no matter what you do the gears will slip under torque. Especially if they are in the driveline used for traction.

Keep up the good work.

BTW, The bucket is absolutely beautiful.

[Jurss]

18 hours ago, teflon said:

The bucket is fully operational.

Maybe leave it manual, just for looks. This looks really weird. 

Otherway I like Your challnege, and how You are dealing with it.

[teflon]

Thanks for suggestions or just words of support.

@proran: Wow, I have missed your Mecalac. You are quite a gear master;-) But I agree with you, probably gears are better and I can try something with thin liftarms (those allow just enough space to set angle gears).

@Jurss: Yeah, I know, the linear actuator is almost larger than the bucket. Perhaps I'll find the solution with gearing alone.

[cyberdyne systems]

That is more than just impressive! When I was building my version, I thought that this is the most complicated thing to be made out of 42100 ... "I have never been so wrong in all my life"! 

[teflon]

Some follow up on my project.

First, the scale. As I mentioned, the scale is about the half of 42100. However, I later found out that 42100 is not in minifig scale (about 1:48) but more into 1:30 scale. Therefore my would be somewhere in area of 1:60 or 1:80 scale. And here is a picture of overlay of blueprints and my (early) design.

 

The build is more or less divided between 3 major parts: Undercariage, main body and the arm.

I was mostly satisfied with the arm but Jurss rightfully complained that the last linear actuator is awkwardly placed. Therefore I changed the design - used  and used some lever to make it more compact. I am using worm gear which makes movement quite slow but it's manageable.

While dealing with the hand, I also changed the way how movement is transported along the arm. Instead of universal joints I have used bevel gears. I am using three triplets on one axle. The axle is also the pivot point of the arm. To get compact enough design, the side of the arms are made from thin liftarms. It didn't sound good on the paper but in real world is good enough and not too flimsy. On the pictures below, the main axle is held in place by red quarter ellipse liftarms.

The body has dimensions of 17 x 14 x 8 studs. At the time I was choosing a studded technique since I was convinced to fit two BuWizz bricks easier. Well, this will be changed in the future but for now, let's see some pictures. The color scheme in the moment is white and black. I intend to switch to all while towards the end of my build. I will order proper bricks when I know what I need.

The body is quite compact while holding 2xL and 2xM motors and 2 BuWizz bricks. There are a lot of cables.

Side view:

Front view (sorry, I have used a phone and the perspective & barrel distortion drives me nuts  but for finished :product I'll switch to more decent equipment):

I am also proud on my cable management and color coding. Neat, huh?! Actually BuWizz' are not so terrible to fix in place. They are not heavy and using only two pins allow good and stable positioning.

And one view under the skirt. The bottom motor is the one that lifts the arm.

Unfortunately, the third part of the built - the undercarriage is the most problematic. A proran mentioned it, my building technique was not match for this. I've redesigned the bottom par also but I am not sure if I have managed to improve the construction. The construction is sturdier, however I have used newer treads, which are a bit too wide. I am not sure I like it.

It will be continued ...

[Mechbuilds]

That's SOOOOO compact.. 

[Maaboo the Witch]

Tiny Liebherr! Cool work. 

[jorgeopesi]

I like compact MOCs but they have to have a minimal structural integrity, in my opinion if you build it a bit bigger you will have even a better MOC.

[teflon]

Once more to the breach, my friends ...

As mentioned yesterday, I was not happy with the undercarriage and also having some issues with main body, I've changed both.

Side view shows that I went studless. I guess I am more familiar with this despite my age. Basically I agree with Jorge, however construction is not weak. I can grab it by the arm and it can be tossed around without a problem. It even passed my FLL test (while coaching robot building for First Lego Leagu one of my requirements was that robot survives fall of about 30 cm - this prevented some nasty surprises further down the line).

The final surface will consist of plates or tiles, hence pins. In addition  to esthetics, they should serve as additional support. However, since I don't have them in right (white) color, I will not show them yet.

Front view shows connection of arm to the body and bevel gearing:

A view from bottom:

I wanted to put all of my seven motors in the body (and to drive the undercarriage through the turntable such as 8043 https://brickset.com/sets/8043-1/Motorized-Excavator). There is some room but the problem is gearing, that takes almost as much space as motors and therefore could not be done in such a small space.

However, those big treads bothered me a bit more. I've made an alternative version out of old treads and here is a comparison:

For rotating the structure I've used worm gear to give me some slower rotation.

Comparison side by side shows lower profile:

Top view shows that newer undercarriage (right) is much narrower and more in the line with the original blueprint (scale ~1:72)

So you can guess my next bunch of photos will show a new studless body on narrower undercarriage.

BTW: Does anybody misses the undo button with lego bricks? I sometimes disassemble some complex part only to realize that I cant repair it nor put it in previous state. Yup, a physical Undo would be nice!

[mpj]

The undercarriage with old tracks is much more realistic and in scale, so I agree with you to use smaller tracks.

I like it very much, I understand it is very challenging 

The actuator on the side of the boom, the one operated with a wormgear, is for the bucket opening? How does it work?

[cyberdyne systems]

I like your progress really much! It seems soooo complicated! So, I've continued my research on miniaturization and came up with this really small crane which nonetheless has even more functions than my mini-Excavator! They are made in the same scale, so, if you want after the completion of your current MOC you may want to make RC version of my little crane ;)

 

[teflon]

I guess the more I am approaching to the end of the build, more and more things I want to change and repair. I guess this is Lego Dunning–Kruger effect. As mentioned before, I have went backwards and used old-style treads. They look okay for this scale. I have also repaired the main body using technic frames 5 x 7. They are not necessary, however after some days sitting on the desk, the model seem loose, gears start to jump and I have to take a lot of attention to get it back in the form.

Nevertheless, I have made some progress and here are some pictures. The side view:

The side-top view shows the upper part:

Front view of the arm.

And arm functions:

There was a question how bucket opening works. I've tried to draw out the principle: I am running the worm gear, which rotaters a pair of gears, the larger of them is pushing small linear actuator. When it is prolonged, it pushes small lever forward and on the other side that pushes small lever forward. Then the pushrod moves the bucket.

Model is suitable to push itself into air, bu of course deformations are quite karge.

I still have to take pictures of the interior and the undercarriage (which is also changed). And at the and I'll try to convince my son to make video to demonstrate our work.

Nevertheless I am getting quite happy with the built. It's quite sturdy (besides some minor parts).