I thought for a while which set to select for my entry, I wanted it to be something that I own, but also large enough to make for a meaningful scale down, while retaining its essential functions. I considered 42082 and 42043, but then settled for 8868 as I'm quite fond of it, and have wanted to replicate it in some form for a while now.

I'm using 49,5x14 tyres, which have proportions similar to the original wheels, which gives a scale down ratio of about 30%. I also want to retain the original functions as closely as possible, which means for example that the pneumatic slewing function must be replicated. The rules prohibit electronics, so obviously there'll be no motorized compressor, that I'll replace with a manual pump. I'm yet to think what to do with the space freed up from the battery box and motor, we'll see.

8868 had some aesthetic touches uncommon for its time, so I'll try to replicate those too, which makes some paneling necessary but I'll keep the open areas where they were in the original.

I started with 3D modelling to see if I actually could fit the core functions (mainly fake engine and the turntable base) in this scale properly. Moving to physical build now to make sure what I modelled is actually buildable and structurally sound.

 

One of my favourite sets ever! I am excited to see how it turns out :) 

Crud.  When I saw the contest announcement I immediately thought: I need to do 8868, my childhood favorite. Checked the topic list and must have overlooked this post.  Oh well, I guess there will be two. I’m building a bit smaller, will try to post a WIP sometime this weekend. 

 You’re off to a good start, I’ll be following with interest!

Great choice! Although I have never possessed 8868 it is still one of my all time favourites. Your start looks promising and I cannot wait to see the final model.

On 7/1/2023 at 4:34 PM, lcvisser said:

Crud.  When I saw the contest announcement I immediately thought: I need to do 8868, my childhood favorite. Checked the topic list and must have overlooked this post.  Oh well, I guess there will be two. I’m building a bit smaller, will try to post a WIP sometime this weekend. 

 You’re off to a good start, I’ll be following with interest!

Having the same source material is fine, Hopefully we'll both finish our models properly and get to compare the results!

On 7/1/2023 at 5:04 PM, brickphisto said:

Great choice! Although I have never possessed 8868 it is still one of my all time favourites. Your start looks promising and I cannot wait to see the final model.

Yep, it's a great set, one of the best ever.

Some progress. Fitting the turntable and associated mechanism is a challenge and I had to resort to some weird half-stud offsets to manage it. I'm a bit worried about the structural integrity of the build (it has to withstand the presses of the pump), but we'll see about it as I get further into the physical build.

One of the first things I designed was the two white tanks in the side, the best scale would be three stud diameter but it was really difficult to come up with something that has this diameter and is round and also buildable. The best I came up with was the Hero Factory weapon barrel, attached to rotation joint and capped with a dish on one side and round tile on the other. I'm not entirely happy with it, something smoother and completely white with dishes on both ends would be great but those rotation joints don't come in white and I couldn't find a way to connect another dish in place of the tile. It's a minor thing though.

The photo should give a sense of scale and shows some of the structure below the turntable which is going to be attached to the two black pins on the topmost liftarm. There's also some progress on the structures around the engine compartment.

 

Has your 8868 been assembled since 1992? 
 

The rest section looks familiar, very similar to the original. Is the half-pin in the plate with gear rack in system? It seems it wouldn’t align with the piston, but I might be wrong.

52 minutes ago, lcvisser said:

Has your 8868 been assembled since 1992? 
 

The rest section looks familiar, very similar to the original. Is the half-pin in the plate with gear rack in system? It seems it wouldn’t align with the piston, but I might be wrong.

No, it was in disassembled state for at least 20 years, after which I gathered the parts and reassembled it. Now it's missing some parts for being cannibalized to other projects but I intend to fix it for proper comparison photos before the contest ends.

The plate with gear rack does indeed align with the piston, at least according to my 3D model. I don't have those cylinders though, so I'll have to wait for my BL order to come before I can finish the assembly.

Judging by the photo - is it actually 30%? Also what's up with side-by-side comparison with compared models placed in opposite directions ? :D

1 hour ago, SaperPL said:

Judging by the photo - is it actually 30%? Also what's up with side-by-side comparison with compared models placed in opposite directions ? :D

The perspective makes my model look bigger in relation to the original than it is. According to Technicopedia, the original's length is 58 studs, which translates to 40,6 studs with 30% reduction and my model's length is 41 studs from the front grille to rear bumper. The front and rear parts are also somewhat misaligned as they're not attached into each other in any way in the photo. I'll post better comparison when there's more to show.

Isn't it too high though? The original has a 4 stud distance (pin-center-to-center) vertically between the rear axles and the mountpoint of the turntable, and so does yours. Of course the old turntable is much higher, but I think you're still too high.

1 hour ago, pleegwat said:

Isn't it too high though? The original has a 4 stud distance (pin-center-to-center) vertically between the rear axles and the mountpoint of the turntable, and so does yours. Of course the old turntable is much higher, but I think you're still too high.

Yes, the old turntable is higher, but mine is still going to be set somewhat higher than the original. There's no way to I could make it lower without compromising either the differentials or the original slewing mechanism.

13 hours ago, howitzer said:

The perspective makes my model look bigger in relation to the original than it is. According to Technicopedia, the original's length is 58 studs, which translates to 40,6 studs with 30% reduction and my model's length is 41 studs from the front grille to rear bumper. The front and rear parts are also somewhat misaligned as they're not attached into each other in any way in the photo. I'll post better comparison when there's more to show.

The real model measures 50 studs bumper to bumper, 52 if you count the bull bar. I think the 58 includes the arm plus gripper sticking out of the back. 

1 hour ago, lcvisser said:

The real model measures 50 studs bumper to bumper, 52 if you count the bull bar. I think the 58 includes the arm plus gripper sticking out of the back. 

Wow, that's true. Looks like I'm going to have to lose a few studs from the length.

So, as it happens, I made some kind of error in calculating the scales and apparently my measures were for something like 80% reduction in size. That's too small a difference for the contest, so back to the drawing board. Going to have to switch for smaller tyres too, the Model Team wheel+tyre appears to have the correct size for scale factor of 0,7 so settling for that for now. Not sure how I'm going to fit the pump as it's enormous, either it's going to stick far out or I'll have to think of some really creative solution to hide it, but we'll see...

If I count correctly, the original is 17 studs high from bottom of chassis to top of battery box. At 70% that is 11.9 studs. I think the new (blue) manual pump is 11 studs, so if you mount it at the bottom of the chassis it should fit upright. Just 1 stud to spare for the drive shaft to go under the pump.

 

Great choice here, used to be one of my favorites as a child, curious to see how you manage to preserve the functions!

33 minutes ago, lcvisser said:

If I count correctly, the original is 17 studs high from bottom of chassis to top of battery box. At 70% that is 11.9 studs. I think the new (blue) manual pump is 11 studs, so if you mount it at the bottom of the chassis it should fit upright. Just 1 stud to spare for the drive shaft to go under the pump.

 

Yeah, gotta think of how to fit it there. Perhaps it's possible.

30 minutes ago, gyenesvi said:

Great choice here, used to be one of my favorites as a child, curious to see how you manage to preserve the functions!

I it seemed to be fairly easy for my misscaled build, but we'll see how it goes for the correctly scaled version. Some differences in proportions are unavoidable, as there's no way to fit pneumatic hosework through the small turntable while retaining the rotation mechanism, and large turntable makes for proportionally much larger base.

So, I started to make a smaller version of it, and it feels surprisingly easy. I must to switch from large pneumatic cylinders to small ones and while that allows smaller scale, I fear they are not powerful enough for the turntable but that's something I have to live with. I'm also worried about the hose routing to the crane as it'll be a very tight fit through the turntable. I managed to lower the turntable one stud by putting the rack gears between the turntable mountings but that forces usage of 8T gear, which reduces the leverage (relative to 16T gear) and the smaller pistons are of course weaker too. On the other hand, the build is stronger and much more compact now and I was able to drop the weird half-stud build for the turntable base.

Here's a render:

 

Had a few busy days doing other stuff but now I got back to building and I have some developments. It's been an exercise of squeezing in all the functions I want and the necessary structures to support them, but I've managed so far. It's going to be a quite dense build, but I think I have the chassis mostly worked out now.

I decided to use large short cylinders for the slewing for more power, but I fitted the spur gears between the turntable attachment points, with a 8T gear in between them. This means it's still weaker than the original but hopefully not too much weaker. This necessitated moving the cylinder attachment points to the outer sides of the racks as there would otherwise be no place for the pump, so I did that. The half-stud offsets make everything more difficult than they should be with the very limited selection of parts to build those with. I really hope TLG makes some more useful parts with half-stud offsets one of these days...

Anyway, here's a photo:

Now there's the nightmare of doing all the hosework for the functions...

Looking good, nice progress!

 The hoses from 8868 era are much more flexible than the new ones, And a bit smaller in diameter too. 

Another progress photo, this time with some progress on the front and some hosework added. For longer hoses I'm using 3rd party silicone hose, which I can cut into exact size and which is similar in flexibility to TLG's old style hose.

I also made a mock-up of the crane to get a sense of the scale and geometry. The claw is functional with the same working principle as the original, only it's more compact. Still, it's quite big and chunky, but I can't see how it could be made smaller, while the boom and jib could perhaps be reduced slightly in size. I would also like to use large cylinder for the boom but it might be too large for this scale. The slewing works fine as it is, though there's no way to fit the hoses through the turntable so I'll have to think of a way to route them through the top of it.

I also had to do some thinking to be able to build the mudguards and front grille in a way that's both sturdy and faithful enough to the original, but I think I managed. Had to resort to studful parts though.

 

 

My entry is nearly complete, with only missing some parts for details that I have ordered and should arrive within next week. I set out to replicate all details and functions that the original had, and I'm happy to report that I succeeded at that! All functions work nicely and I'm mostly satisfied with the proportions and details. There were many difficult parts to the build and with some of them I'm not entirely satisfied, but mostly it turned out nicely. Some parts I redesigned many times over and it's good that I did, the later iterations are significantly better than the first attempts.

Here's some quick photos of the not-yet-finished build with some parts missing. I'll get better photos and maybe even a video if I'm able as soon as have the details finished.

 

So, I didn't receive the parts I ordered in time. This means my build is missing some aesthetic touches and has few parts in wrong colour. Nothing I can do to fix those as the deadline is today so this will have to do. Here's the final photos as far as the contest is concerned, sorry for the cannibalized and mutilated 8868, it has suffered a lot over the years. Higher resolution images at http://www.jousimo.fi/lego/TC25/

 

The finished model looks easily recognisable! Interesting choice of the transparent pneumatic tubes, is that intentional? Did you try it with black ones as well? Did you choose the transparent one so that it does not clutter the whole arm's looks?