After watching some youtube videos I noticed some trucks had some weird suspension on them...

It looked something like this:

So naturally I started investigating and found that this is a type of setup called a twin beam suspension.

So I tried to replicate one in Lego. To explain the concept behind this hybrid, here's a series of stages leading from live axle suspension to the double beam setup:

In order:

Yellow setup is a live axle

Red setup represent the change from dependent suspesnion to independent suspension

By extending the half axle lengths (blue) we get a lower change in wheel angle relative to the drive surface (camber)

And finally by extending the swing arms PASS the center point we get a double beam suspension

And here's a version with drive and steering:

So what are the advantages compared to the live axle?

- Its independent, which as name suggest aloows the wheel to work independent from each other

- Lower unsprung weight

- Less moving parts - to keep a live axle in place you need several linkages. Here the axle pivots around one central point

And disadvantages?

- Complex design, the axles have to be made to travel pass each other without interfering.

- A need for a CV joint which needs to allow the axle to slide in and out

- Not as robust

- Hard to implement portal gears without making the wheels slide sideways excessively

- Camber changes are still present

I also made a video explanation of the principe. You can skip to 4:30 to see the final version in action:

So the final question. Is it useful? Fo me as far as the Lego version goes....no. The disadvantages outweigh any possible advantages. Also lately I have been working a lot on long travel double wishbone suspension which outperform any other previous suspension system in almost all categories.

The only usefulness in this design I see is realism, if you are building a replica of a truck that has such suspnesion.

Because I want to hear your opinion, here's the LDD link to the suspension, so you can try to make your version and improve upon my prototype:

Download prototype here

Edited March 10, 20168 yr by Zblj

I have seen Volvo using something similar for the rear suspension of some FWD cars. Similar as in your example, one of the the hingepoints of the left suspension unit is at the right of the car and vice versa.

The best illustration I could find is this exploded view:

To clarify, the left wheel attaches to hub (nr13) and the front of the car is a the left of this image. The hinge points of each suspension half are parts 6 and 2.

Edited March 10, 20168 yr by Cumulonimbus

Rare concept, as you say I only use it in case of a replica MOC, anyway is always good to know more about new configurations.

Nice implementation) Real ones have additional longtitudal links. Zblj, did you thinked about using bionicle ball joints for that type of suspension? Without differential and drive it can be simple and robust... I'm already want to tinker something myself)

I've seen it alot on trophy trucks,. Very interesting concept, specially the driven version on the photo,..

Really cool prototype. How would you transfer dive to the universal joint coming of the suspension setup at the moment? Also, what does the [POC] tag stand for in the topic title?

Cheers

Nice video for explaining suspensions to kids, and them having the build IRL. Comments are well taken, but nice to have another way of building in the tool chest.

Really cool prototype. How would you transfer dive to the universal joint coming of the suspension setup at the moment? Also, what does the [POC] tag stand for in the topic title?

Cheers

I dont understand your first question. I think you can see the way power is transfered via CV joint?

EDIT:

Oh I think what you mean, main power to the diff. Siple use another U joint and transfer power as you would to a live axle.

POC stands for proof of concept, a moderator or admin, shortened the title.

Edited March 10, 20168 yr by Zblj

Hi,

i love 4x4 & trophy truck races, like baja 1000, etc...and and this type of suspension is fairly common in these races, but this trucks are only rear wheel drivw.

but I had never seen the 4x4 configuration . really I think the biggest advantage is the mixture of long travel and fairly reliability / resistance.

anyway you have achieved a good reproduction of something very rare

Looks great Z! That suspension design was pretty common in many of the late '80s / early '90s Ford trucks and SUVs. It's a slick setup and has some nice travel.

mmm, This is really interesting! It could bring a lot of travel to really small systems, I bet.

Edited March 15, 20168 yr by ChocolateEinstein

It's the first time that I see this type of suspensions!

Thanks for your curiosity!

I learned something new!

Very interesting.

The nice thing about this suspension type is that it offers a relatively subtle variable camber angle - especially when the beams surpass one another substantially - with less moving parts than for instance double wishbone suspension.

Many rigid axle suspension types typically have an extremely varying camber angle which is not very good for road holding. Tatra suspension is another example of such exaggerated camber angle variation.

Less rigid suspension types such as McPherson strut suspension and double wishbone suspension usually have a variable camber angle with a virtual rotation point way beyond the center of the car to confine the camber angle variation. Twin beam axles accomplish this with long parallel beams and less moving parts, which is what I like about it.

When it comes to building lego suspensions I still prefer the double wishbone setup because it is strong and can be easily adjusted to specific handling characteristics.

Thanks for putting in the effort and sharing this with us.

Diederik

Edited March 11, 20168 yr by Didumos69

I dont understand your first question. I think you can see the way power is transfered via CV joint?

EDIT:

Oh I think what you mean, main power to the diff. Siple use another U joint and transfer power as you would to a live axle.

POC stands for proof of concept, a moderator or admin, shortened the title.

Ok, Cheers!