[HELP]How to make a supercar sturdy ?

[Alex Ilea]

Hello all !

I want to ask you guys about building a sturdy car (here comes the noob questions) :

-How you make the part of the chassi that sits between the suspentions sturdy , while haveing a low pozitioning of the central beams/panols (ex 11×3 curved) ? The Aston Martin DB11 by Joeron Ottens (sorry if spelled wrong) is a very good example.

-How to make the roof-pillars strong ? (ex rugged supercar by Didumos69 ) All my previews cars have the windsheid frame loose.

Hope you understand what I ment 

[Blakbird]

1. Keep the chassis rails as far apart as possible both in the horizontal and vertical planes.  Stiffness varies as the cube of distance, so a little distance makes a big difference.  Never build the chassis only one stud thick.
2. Use as many right angle parts (L-shaped liftarms) and diagonal braces as possible.
3. Use frames (5x7 and 5x11 light gray frame boxes).
4. Use friction pins (black) as opposed to frictionless pins (gray) or axles to assemble the chassis.
5. A chassis built from old studded parts is much stiffer than a studless chassis.  A combination of both gives you the best of all.  Check out the instructions for 8466.

[Alex Ilea]

Thanks BlakBird ! 

[BrickbyBrickTechnic]

That answered a bunch f questions I had on the same topic! Thanks IA and Blakbird!

[VKTechnic]

All of Blakbird's points are very true, I've got a couple to add myself:

• For pillar techniques, take a look at Nicjasno's E30 WIP photos. A lot of great techniques that made for a really strong unibody, and they're 99% legal  
• Triangles are your friend! They're the strongest shape, and there are quite a few triangle geometries that work really nicely with LEGO.
• Ditto on Blakbird's "spreading out" point. Try to avoid just building a central beam connecting the two axles (making an I-shape), and try to avoid building a flat floor too.
• There's no such thing as too much bracing! Use cross blocks and such to reinforce structural beams along the length of the chassis.

Hope this helps!  

[Alex Ilea]

Thanks VK ! This topic became so usefull 

[Lipko]

I also advise to build some others' MOCs (there are many good quality instructions for free) to get a hang of how sturdy other cars are. You don't need to design rock-solid chassis.

[Alex Ilea]

12 hours ago, Lipko said:

You don't need to design rock-solid chassis.

You say this and you build one for your car that you have as profile picture ;)

[TechnicRCRacer]

a LOT of connections and support. I kept trying to make a chassis with the older differential, but it wasn't sturdy enough. I discovered in some pro MOCs that some chassis are mostly connectors and cross blocks. This may be a bit hard, though. Anyway, I like long beams with frames in between since I don't usually use independent suspension. If it is RC, try to mount the motor sideways, which allows more room for the battery box. Plus, use the motor as a brace. I hope that this was helpful!

[Didumos69]

Many wise things have been said here already. To me there are several aspects to building a sturdy car: Cohesion, bend rigidity and torsional rigidity. Not all three are always important, for instance in a Unimog chassis torsional flex is desired.

Cohesion - To me, building something that doesn't fall apart and doesn't require any fixing of connections after using it, is more important than building something that is very rigid. To obtain a highly cohesive structure, you have to think about the forces the connections in your structure are exposed to. Make sure the most substantial forces work orthogonal to your connecting pins. For example: When you have several connected beams spanning the length of your chassis, it is better to have them oriented with their pinholes horizontally than with their pinholes vertically. Otherwise your vehicle is likely to fall apart under its own weight. @Jeroen Ottens refers to this practice as using form-locked connections rather than friction-locked connections. Now the example I gave is very simple, but it can be extremely hard to make everything relevant form-locked. When I was testing my rugged super-car I found out that the connections in the left and right sides of the hood slowly declined. So I added a width-wise construction keeping the parts together. I did similar things wherever it was needed, until I was satisfied.

Bend rigidity - To avoid bending in your chassis it is important to have some kind of bridge or console running through the middle of your chassis from the front all the way to the back. The higher, the better. I would say at least 5 studs high.

Torsional rigidity - When your bridge / console consists of several beams (or 'rails') that are not connected somewhere halfway, the four beams together will easily twist. To avoid this torsional flex, you have to make sure the beams remain squared. This is where triangles and squared elements come into play. In my rugged super-car I wanted to have no more than 5 studs space between the seats. After tying my bridge / console together with 5x7 frames there was still quite some twist in the narrow section between the seats. To avoid torsional twist in this section I integrated several 3x5 frames. In addition I used this: part in the top side of the bridge. This 'squaring' reduced torsional flex significantly.

As a source of inspiration, here is the LXF-file with the main structure of my rugged super-car.

Edited March 24, 2017 by Didumos69

[Alex Ilea]

Exacley what I wanted ! Thanks so much ! I am so happy for the great advices that were given here !

[Erik Leppen]

One of the things that help me most in getting a supercar chassis rigid, is to use the middle console (that contains the switch for the gearbox) and connect that to the front and back unit. That way, the chassis is effectively 5 or 6 studs tall, instead of the usual 3.

In a rare case, another option that hasn't been mentioned is, use the roof as an actual cage, by constructing the sides of the windscreen with beams instead of axles. I apologize for the huge picture, but this is a perfect example:

As you can see, even Blakbird's "never build the chassis only one stud thick" is not a holy rule ;) As an added bonus, the seats are also part of the structure.

Similarly, when having the engine between the axles, running a single beam over the engine could also work wonders. This way, the chassis is not just below the engine, but around it.

A few small other considerations that may not have been mentioned:

- blue 3L pins are a bit stronger than normal black pins. Use those if you can.

- if you can, studded beams connected with plates are very rigid. 8448 is the best example of this.

- when vertically connecting beams that are 2L apart (3L total height) you might be tempted to connect them with 3x5 L beams, but I find that the new dog bone beams are a bit stronger. In general, 5x7 and 5x11 frames are your friend, but the dog bone is a wonderful piece to use as well.

- the chassis usually needs to be thinner at the axles than in the center, because the gearbox needs room but the suspension also needs room at the outside. Don't make the difference in width too large. If the chassis is 5 wide at the axle and 13 wide at the gearbox, it's harder to make it strong than if the widths are 7 and 11.

- At least as important as the section betwen the axles, is how you connect it to the axles. Have a beam run through the axle unit, instead of having to stop to make space for steering racks etc.

- A straight construction is stronger than a bent or stepped construction. If you different sections are at different heights, you need more parts and more connections, which results in more play, and more bend.