[TC27] Compact Backhoe

[Ngoc Nguyen]

Those who follow my Technic corner will know that I have a particular liking for shrinking model. And for my next act, I'm gonna shrink... my own model!

Last summer I created this half-backhoe out of 42157. 

 

I've always meant to go back to it and build the excavator arm but I haven't had the chance. Not to mention, at that scale it is hard to make a stable and structurally sound sliding mechanism, as it will needs quite a lot of bracing. But for the smaller model it might be feasible.

 

The sliding mechanism is achieved through a scissor linkage that I developed for the sliding cabin in the Reach Stacker in the Container Play Set MOC.

Edited June 17, 2024 by Ngoc Nguyen

[Ngoc Nguyen]

The key thing about a compact backhoe is, well, compactness. That means it needs to be able to slide and fold the excavator arm neatly. The 49.5 tire scale is the only scale at which these two features can be realistically achieved, so they are must-haves in my model. And I managed to replicate it at least on Studio.

 

 

I'm not sure whether the scissor linkage sliding mechanism will actually work because I haven't built with real pieces yet, but based on what I experienced in my Reach Stacker it doesn't really work smoothly. So I replaced with it with a simpler and more compact mechanism. Compactness is the key.

 

Edited June 21, 2024 by Ngoc Nguyen

[MP LEGO Technic creations]

This is something I'm really looking forward to. Building backhoe graders is always fun.

1 hour ago, Ngoc Nguyen said:

fold the excavator arm neatly

This resembles one of my attempts to fit it into a tight space...

 

[Thirdwigg]

Interesting project, and I'm interested to see what you are able to do. It looks like a lot of functions will be placed, particularly in the rear. I hope you are able to get the sliding mechanism working well, but I like the change from the scissors to the gear rack.

Are you able to change the pivot from the worm with 20 tooth gear system to a worm and 8 tooth gear system? It might help to get the digger a little closer to the cab. It looks a little too long to my eye right now.

[Ngoc Nguyen]

9 hours ago, Thirdwigg said:

Are you able to change the pivot from the worm with 20 tooth gear system to a worm and 8 tooth gear system? It might help to get the digger a little closer to the cab. It looks a little too long to my eye right now.

I did explore that direction but settled with the current one, because the excavator arm is 3 stud thick in the base, which means when it rotates 90 degree to one side there must also be a vertical 3 stud gap. In other words there must be one row of unoccupied stud behind the row with the pivot point. It looks like this.

From:

  O
x x x

to:

x
x O
x

 

Edited June 22, 2024 by Ngoc Nguyen

[Ngoc Nguyen]

This is where I'm at right now.

 

The whole chassis rests nicely on a pair of 3x19 yellow frame, in the middle of which run 3 drivetrains for 3 functions: fake engine, steering, and rotating chair.

The basic shape of the cabin is done. The next major task involves designing the interior, the wheel arch, and the side fuel tanks. I feel like I've hit a creative wall so I'm just gonna leave it here and do something else in the mean time.

[Jundis]

Really nice progress!

Love the little fenders and the overall scaling.

Critic: Blue seat is a must!

[Ngoc Nguyen]

12 minutes ago, Jundis said:

Love the little fenders and the overall scaling.

The rear fenders really gave me headache. The best solution is the Corvette wheel arch, but it isn't available in yellow. 

Then I used two rows of 5 stud long #4 connectors. But the upper row interferes with the pins going to the pin holes of the lower row so I had to make the top row 6 stud long instead. It still looks messy but at least it's better than the former arrangement.

This is the base vehicle without arms btw.

 

[Jundis]

1 hour ago, Ngoc Nguyen said:

Corvette wheel arch, but it isn't available in yellow

Wheel arches from 42151?

[Ngoc Nguyen]

Just now, Jundis said:

Wheel arches from 42151?

No space