četrtek, 10. marec 2016

Lego double beam suspension

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