Rail on rail subframes

[Ramdough]

All,

I have a question regarding the rail on rail design.

What is the primary purpose of having the springs distributed down the length of the frame instead of just at the free end?

While looking at the stiffness of the sub frame vs the springs, obviously the springs are much weaker than the torsional stiffness of the frame.

The free end will translate the most and needs the longest springs, so what do the middle springs do? I could see some slight advantages for being stiffer, but not a lot.

Also, I always wondered why you would put the anti-slewing plates on instead of using a panhard bar to control the free end from sliding right and left. I am thinking of doing that so I do not rub while driving.

Thanks in advance.


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[mog]

A- What is the primary purpose of having the springs distributed down the length of the frame instead of just at the free end?
B- The free end will translate the most and needs the longest springs, so what do the middle springs do? I could see some slight advantages for being stiffer, but not a lot.
C- Also, I always wondered why you would put the anti-slewing plates on instead of using a panhard bar to control the free end from sliding right and left. I am thinking of doing that so I do not rub while driving.

(disclaimer-out of my lane)
A- multiple 'weaker' springs than a pair of heavy springs, spreads the work and is more progressive. Easier to build smaller mounts. More redundancy in case of failure.
B- as you can see from the attached photos, progressive lengths
C- simplicity


Photos of 4wheel24 truck at the 2018 Abenteuer Allrad in Bad Kissingen

 

[pugslyyy]

(disclaimer-out of my lane)
A- multiple 'weaker' springs than a pair of heavy springs, spreads the work and is more progressive. Easier to build smaller mounts. More redundancy in case of failure.
B- as you can see from the attached photos, progressive lengths
C- simplicity

View attachment 635385 View attachment 635386 View attachment 635387
Photos of 4wheel24 truck at the 2018 Abenteuer Allrad in Bad Kissingen

I'd also add that most of these body mounting techniques are derived from the Australian Design Rules (ADRs). The ADR does not mention a panhard as an acceptable retention method, but does mention that outrigger mounts should be every 900mm along the frame.

 

[lanceatm]

There is a difference between ADR and VSB6 -one is a code -one is a book of rules. VSB6 is an excellent reference guide for vehicle builders ( it has been superseded to include non commercial chassis)of medium and heavy trucks. In a different life I worked with many talented individuals as liaison to Federal authorities and industry to have codes and rules that make sense.

 

[Joe917]

Mercedes does not approve rail on rail with springs for the older trucks, only 3 point mount or rail on rail solid connection.
Our truck is rail on rail solid connection, 27 years old 430 000 km no issues.