Thread: Tandem Suspension Concept

Awful lot of pivot and wear points in that design. Why don't you get a copy of Motor Truck Engineering Handbook and look at the many types of tandem suspension in there. Keep it simple. Single point, air bag, Chalmers, Mitchell suspensions all work well.

Looks to me like you would be multiplying the load at around 2:1 to the shock/strut and I doubt that shocks would work at that angle, Regards Frank.

not a lot of latitudinal stability either....

to achieve what your describing why not just go for something like a camel back setup with the shocks mounted inboard onto the frame?

The springs will work like that but shocks wont.

The load on the top of the strut will be extreme at the least and then your doubling it on the shared strut.

The pivot that the arm swings on would have to be pretty beefy to handle the stresses.

You would be best to have it drawn up in CAD and stress tested, you may find that if you could run the struts vertical by cranking the arms and shortening the arm length then the theory may be plausible.

I don't think it's a bad design, you could use remote reservoir shocks with hydraulic rams for the strut itself, then it could work on an angle but would make it extremely expensive to build.

Cheers Casper

Depending on how you set your spring rates, I don't think your trailing axle will have a significant role in load carrying... that would make it interesting in terms of stability and not wagging the trailer and probably a jumpy empty trailer and a soft loaded trailer. As already said, the springs and shocks wont be particularly effective, especially with the spring rate reducing as further load is applied to the axles. There is a lot of load rippling through the sytem in it. Likewise I think keep it simple and for leaf setups I like just the rocker setup, and for coils I do like the system used by the army dual axle trailers, although they have to be built heavier in the chassis due to the single point loading of the dual suspension.

looking at the link angle, wont the axles have alot of roll steer?

Why re-invent the wheel?-

I'd be inclined to look at existing setups (like trucks etc as has been suggested)

If you're looking around or up to a tonne, what about caravans?- Similar weight, criteria is a good ride so as not to shake it to bits... stable enough to be towed by amateurs, and trouble-free.

Some manufacturers offer differant suspensions at differant prices for differant uses.
-No reason why they can't be beefed up or even changed to air-suspension...

Yes I agree with Serg that the link angles are a bit steep and with Brian that there are too many moving parts to wear.
The more I think about it Steve, from a ride, durability and simplicity viewpoint, I cant go past the centrally pivoted inverted leaf spring setup I mentioned as used on logging dog trailers, before they started using airbags.
The leaf spring pivots capture the centre of the spring in a snug fitting channel to prevent it swing laterally, so no panhard rod or A frame required.
as an example if you were to use Series Land Rover rear springs and wanted an axle spread of 36'' you cut the ends of the springs around 20'' from the centre bolt , drill locating bolt holes at 18'' from centre and firmly clamp the axles to each end of the spring with U bolts.For extra security you could heat up the spring overlap and bend them 90 degrees over the front face of the axle, assuming you use square section trailer axles. The axle with brakes, or if you decide to go ahead and power one axle would require a single upper torque rod. The unbraked or undriven axle would not need one.
Earlier tandem drive Mack trucks used a similar design with a single upper torque rod and the ends of the springs doubled as lower control arms. I think it was known as the Mack Camel Back suspension due to the shape of the leaf spring pack.I used a similar setup with one upper and two lower links on each axle and a shock absorber on each corner on my old 6x6 LandRover, and everyone who ever rode in the back would remark how smooth it rode over rough terrain.
Bill.