[MOC] Mercedes-Benz W108

[jtlan]

Hello everyone! First-time poster here.

Here's a model I built of a Mercedes-Benz W108. I built this with the goal of putting as much mechanical functionality in as small a space as possible. The resulting model is 14 studs wide (not counting rear-view mirror) and features:

• 4-wheel independent suspension
  
• Moving inline-6 engine connected to the rear wheels
  
• Hand-of-god steering which also turns the steering wheel inside
  

The scale is roughly 1:15.

It's kind of chunky partly because I was going for an "old-style" technic feel, and also because the actual W108 is rather boxy.

As on the actual vehicle, the front wheels feature double wishbone suspension and the rear wheels use swing arms. Because the model is so narrow the differential isn't located between the rear wheels, but rather connects to them through a pair of shafts:

You'll notice that the universal joints don't seem to correspond to any hinged parts; they're there to accommodate misalignment between Technic beams! There are a few locations in this model which feature sub-millimeter precision; if people are interested I can write a post later about alignment and why it's bad to pass an axle through more than a pair of beams.

Speaking of sub-millimeter precision, the front steering depends on the fact that a lift arm is slightly narrower than a stud. Here's a view into the steering mechanism with the engine removed:

The dark grey and black lift arms in the center of the image form a parallelogram linkage, so the dark grey steering links get actuated in sync. You can also see where I put the differential...

Speaking of the engine, here it is:

It's based off the excellent "fake engine" by laixEngineering. I highly recommend this engine for smaller models; not only is it better scaled than the massive engines built with the actual piston parts, it also makes a pleasant diesel rumbling sound when spun.

Due to the relatively small size of the model I didn't have room to model some features, such as a gear shift or the rear seats. It's actually possible to motorize this model, although the steering/drive motors take up all of the interior space and the battery box looks rather silly sticking out of the trunk...

Full gallery here. Thanks for stopping to take a look! I'm happy to answer any questions about the construction, precision alignment, etc.

Edited February 8, 2014 by jtlan

[Hrafn]

I'm impressed with the number of functions you squeezed into that space! The engine is nice, too. I would have thought that the plates with clips would eventually start sliding on the bar - do they hold up OK in real life?

[jtlan]

The engine is nice, too. I would have thought that the plates with clips would eventually start sliding on the bar - do they hold up OK in real life?

I've run the engine for quite some time and I haven't had anything bad happen. Those vertical clips hold quite tightly, and there's no force trying to slide them axially along the bar (unless you consistently crash the car into objects at high speed). There's not much force twisting them around the bar either, since they're only lifting a 2L axle and a half-bush.

The other nice thing about the engine design is that it's possible to adjust the phase of the "cranks" so engines of different configurations can be modeled.

[Brick_Sticker]

Very nicely done, the gear setup in the rear for driving the differential is particularly clever. Lot of stuff crammed into a small space!

[timslegos]

So many details in such a small package, well done!

tim

[Lakop]

That looks really nice. You've done a good job on the functions too and your engine is very clever.

Thanks for sharing.

H

[Junpei]

Great model! The functions are stunning for such a small model, and you have captured the old-style studded look very well.

TLH

[piterx]

really nice man!

i love the old school way it looks :)

[Technyk32231]

Very cool! Why is there a center differential, though?

[jtlan]

Very cool! Why is there a center differential, though?

There's no room between the rear wheels for the differential, so it's mounted in the middle of the body and drives the two wheels through two separate driveshafts. I could have gone without, and that would have let me get more details in, but the idea that the wheels could be scrubbing bugs me. In practice, I suspect it wouldn't make much of a difference if I didn't have one.

The actual W108 seems to have the differential mounted on one of the swing arms, but there wasn't room to try that here either. The Lego differential is just too large at this scale!