[WIP] fully featured hatchback 1:18

[pow]

Hi i'm working on a feature loaded 80's style hot hatchback, because...

Brick builded cars have always been super popular. But somehow the developers usually try to reproduce real mechanics. In my opinion it sometimes would be more fun if the function would follow the form. Like in the Batmobile 76139, for example, where the front wheels don't move back and forth through the fender when steering. They rotate on the spot.

I asked myself: can I do something like that?

Can I build a super compact car without sacrificing features?

So I challenged myself with the task of building a 1:18 scale car, based on parts from the Land Rover 42110.
The following functions should be included:

- manual and motorized version
- manual version with hand of god steering
- motorized version uses 2 M-motors (one each for steering and drive)
- rear wheel drive
- swing arm suspension at the rear axle
- differential
- individually sprung front wheels (rubber band)
- Virtual pivot steering like in the mentioned Batmobil (Step 100 in the 200MB large instruction https://www.lego.com/cdn/product-assets/product.bi.core.pdf/6362924.pdf)
- all doors, hood and tailgate can be opened

The Result so far looks pretty clean and simple i think. You can imagine it took me a while to reach this state.
For example, to make room for a 3x4x8 bricks sized battery box like the BuWizz 2.0, the spring had to go under the roof.

The suspension looks pretty good, i think. And hopefully hides invisibly under the roof. Wohoo!!

Oh and you can't imagine how long it took to develop this simple looking thing like the drivetrain-differential combination in such a tiny package not influencing other sections of the car too much.

Mantra: if it looks simple it took some time to develop.

And what i have learned so far is that building on tiny space means, changing a single part can lead into a rebuild of large areas around. That was super frustrating sometimes. I now have the greatest respect for people who fill such gaps with any complex mechanics. My car is simple compared to stuff you people here on eurobricks often(mostly?) show.

What do you think?

Best wishes :)

Edited December 4, 2022 by pow
typo, brackets in title

[gyenesvi]

I like such small builds, curious what you bring out of it :) Interesting suspension, I once made a similar one, but that didn't go all the way to the roof..

15 hours ago, pow said:

Mantra: if it looks simple it took some time to develop.

Indeed, it often takes a lot of time to reach a clean state!

Quote

And what i have learned so far is that building on tiny space means, changing a single part can lead into a rebuild of large areas around. That was super frustrating sometimes.

I fully agree with this, I have observed the same. Unfortunately, in this sense technic as a building system is like a chaotic system (in the mathematical sense): a small change has long reaching consequences. This is because the technic pieces often do not form proper sub-systems, for example certain parts don't come in various lengths, so you can't just offset something by one stud, you need to redesign the whole assembly. Often, this single-length property of parts introduces a set of constraints that are very hard to satisfy simultaneously. For example, suspension arms, links, CV joints, U-joints, springs, certain types of connectors, they all come in one, maybe two sizes. Also, motors have fixed sizes. If you want to put together a drivetrain and suspension, all those size constraints need to be taken into account, which often conflict. If only Lego produced such parts in multiple lengths, things would become much easier, and much denser and simpler builds would become possible, because it would be much easier to satisfy those sets of constraints. But TLG keeps avoiding such problems and does not introduce missing parts. They don't make much tight small builds, and when they do, they don't make it function rich to avoid the problem (thinking about RWD Ford Raptor). It's a pity, because the building system could be made so much more useful with such additions. But enough of ranting.. was just good to know someone else also realized this 

Edited November 26, 2022 by gyenesvi

[Jundis]

Hopefully you don't get me wrong and I know you put a lot of effort into your build, but I really need to write some (hopefully constructive) critique:

You are using too many little parts to achieve a rather simple mechanism (swing arm) --> the less parts the better

Even you don't have any constraints about the form (hatchback has plenty of room on the rear end), I'd suggest you use 2 soft springs instead of 1 hard spring. You can even use the same lower connection points right above the wheels and angle them diagonally and mount em to the center frame. This gives way more stability.

[pow]

20 hours ago, gyenesvi said:

I like such small builds, curious what you bring out of it :) Interesting suspension, I once made a similar one, but that didn't go all the way to the roof..

@gyenesvi Ah you are speaking of "42099 C model 'Beasty'" at rebrickable?.

Did you use the rocker configuration to get more travel into your suspension or a softer spring - or both?

BTW: i tested some other configurations but only this survived in a backup file, It looks slightly more like your configuration and worked pretty well (the rocker pushes the long end of a 2x4 L-shaped liftarm which itself pushes the shock absorber with the short end).

20 hours ago, gyenesvi said:

[...]If you want to put together a drivetrain and suspension, all those size constraints need to be taken into account, which often conflict. [...]

oh yes, as soon as you try to build to scale, the problems start.
With the small car here, I took the liberty of building a racing version or hot(!) hatchback for this reason. Because of the differential, the rear axle is much too wide to pass as an everyday car.

 

Hi @Jundis thank you for the introductory kind words. I know this kind of communication as giraffe language. A very great and non-violent way to communicate.
You have a good eye for details as I find. And I am grateful for your criticism. Let's put it this way: decisions have been made

Because what I find clean, may seem ridiculously untidy to someone else. Here is a photo of an earlier very untidy state of this suspension and the whole car itself.

Jundis, you mentioned the lower parts of the swing arm. They are one of the oldest parts of the construction. i haven't touched them for a while. Possibly I can rearrange the area. But it depends heavily on the "housing" for the differential. Which is build completely out of 2 types of axle-pin-connnectors.

The idea to hide the shock absorber came up because I find the colors of the parts too flashy. they make the build look too busy.
In a very early attempt I tried to integrate them as a B-pillar. but that didn't work because the spring effect was zero.
In the end they ended up in the roof, since there is a supporting structure under the roof anyway.
Another reason is that there is simply no room to put them elsewhere. Here is a photo of the left C-pillar. It folds way inward.

And the battery box consumes a lot of space too.

As i wrote i'm very thankful for your hints on the build. I will definitely keep an eye on the Swing arm design. Since I haven't looked at optimization potential there for a while. And if you have the feeling it could be cleaned up, others may think that as well.

Best wishes

Edited November 27, 2022 by pow

[Jurss]

Will it be something like mini? As for modern hatchbacks those wheels seems too small. 

[gyenesvi]

3 hours ago, pow said:

Ah you are speaking of "42099 C model 'Beasty'" at rebrickable?.

Did you use the rocker configuration to get more travel into your suspension or a softer spring - or both?

Yes, that one. I used this configuration to bring out more travel and a lot of articulation from the small springs, with that axle construction it would not have been possible to connect the springs to the trailing arms that are also tilting on the turntable. Although it is possible to connect the springs close to the pivot point to allow longer travel, but then the springs become too soft under the weight of such a big model. With such pushrod routing, the springs are not in the way of articulation, but can have optimal springiness as well.

[pow]

@Jurss that is a really good question. The wheel somehow works and there isn't much to choose from. But why not trying to open up the fender a bit to support larger tires as well?!

I just bought 4x tire 35578 with 37x14mm. This is the only tire that still somehow makes sense based on the shape. Everything else is too big or too wide. And if this tire fits, then any smaller tire will fit as well. So everyone can decide for themselves which tire should be mounted. I've created two renders - for size comparison. Tire 35578 is the one mounted as rear wheel.

Your comment was very helpful Jurss. Hopefully I get the tire baked in.

You people are awesome!

[pow]

21 hours ago, gyenesvi said:

With such pushrod routing, the springs are not in the way of articulation, but can have optimal springiness as well

yep, i was amazed at how well pushrod configurations work. I had tested a configuration with 32005a Technic Link as the rocker. That looked incredibly good. The suspension also felt very direct. Disadvantage: It consumes a little more space.

[pow]

I think Jurss' idea to install larger wheels was very smart.

And Jundis: looking over the drive train again helped clear up a construction site that had been giving me a bellyache for a while.

Thanks for your ideas.
What do you think, doesn't it already look quite usable?

Unfortunately, 42110 delivers only 2 black Technic disks. The rims on the front wheels look a bit puny.

Edited December 4, 2022 by pow

[vergogneless]

Hi! Well done on your work!
I'm curious to see how you set up your front suspension system with the rubber bands?

[pow]

As i am a in a hurry i just post two pictures of the front suspension. a few words on how it works will follow on monday.

Or you find it out yourself

[pow]

@vergogneless

Here is a third photo. It's pretty self-explanatory. What i like about this mechanism is that the pivot point of the wheels looks more natural compared to legos default steering mechanisms. where the wheels move forward and backwards a lot.

The blue liftarm with the brown axle is connected to the motor at the front. It pushes the steering arms. The rest is just unholy wizardry. And yes it has a lot of Anti-Ackermann! But that can also be fixed. And if you provoke heavy load changes say push the steering very hard more weight goes into the curves outer wheel and the steering becomes sharper. Plus Anti-Ackermann is used in very fast cars (NASCAR for example). So perfect for brushless motors.

Any questions?

 

Edited June 12, 2023 by pow

[Jundis]

Sry to ask, but did you glue some parts on? How is that slope piece on the front fender attached?

[pow]

10 hours ago, Jundis said:

Sry to ask, but did you glue some parts on? How is that slope piece on the front fender attached?

Gluing: No brick was harmed during build. There is no glue involved.

and the Slope: You'll be surprised how simple the solution is....

And I really wonder why you don't see that more often.

Oh, I'll just throw in the promotional video.

 

Edited June 12, 2023 by pow
added video

[vergogneless]

@pow Thanks buddy, it's terribly ingenious!

[pow]

@vergogneless Thank you. But i don't know if it's terribly or ingenious ;)

But at least it's following the rule: "something is finished when nothing can be removed." -> This steering is definitely finished.

...and no, I am still not satisfied with it.