Thread: Spring Style / Choice. What is the difference?

...and then there is the trailing arm suspension... as dear as.

...and then there's this https://www.woodworkforums.com/f184/c...t-help-132183/ which I thought was interesting and if I had seen it before I started building the trailer I've just finished (with parabolic slippers - tandem) I may have seriously considered.

Originally Posted by Wood66

Eye-Slipper more noise from contact with the slipping end with the chassis (wear and tear on member??)

Sorry, can't answer your parabolic question but with Slipper springs, you can avoid the wear and tear on the chassis by welding in a 'sacrificial' piece of flat bar for the slipper spring to do its slipping on.
Cheers.

Eye - Eye. Commonly called Shackle Springs as they are mounted at a fixed point on the chassis, on what's called the front hanger, at the front eye of the spring, and the rear is suspended by a pair of shackle plates, connected to a dumb jack or rear hanger. Generally, shackle springs have less capacity for the same amount and thickness of leaves than slipper springs. This makes them a little more forgiving for trailers with lighter loads, and is about their only advantage over Slipper springs.
Shackle springs are always mounted with shackles because the spring lengthens as it flattens out causing the shackle plates to pivot. If the spring were to be fixed at both ends, the suspension would be rigid.

Eye - Slipper. Commonly called Slipper Springs, as their name suggests, have a fixed mount at the front, and flat open ended leaves at the rear that slip through the rear hanger. There are several advantages over Shackle springs. Cheaper to buy. Easier to set up when building a trailer. Easier to replace if/when required. Less moving parts, so less maintenance. Even when worn, very little sideways movement of suspension and axle under the trailer.

Parabolic. Another version of a Slipper spring, but instead of several leaves, the spring is one main leaf that tapers in thickness from thin at each end, to nearly 3/4" thick in the middle. Their capacities are more limited to a few set specifications (600, 1000, 1400Kg), and there is no way to increase or decrease this without replacing the entire spring. The main differences between Parabolic and Multi-leaf Slipper springs is that with one leaf there is no friction between the leaves to give a shock absorber effect that you get with multi-leaf springs, so under load, the suspension will oscillate longer, and with only one leaf, there is nowhere for contaminants to get trapped between leaves, so less chance of the spring rusting. This is particularly good for Marine use, and where I would recommend Galvanized Parabolic springs.

Then there's the huge range of Independent Suspensions. Most consist of a trailing arm with a stub axle attached, which is then supported by a spring, either a leaf spring or a coil spring. While a coil suspension sounds fancy, giving a softer ride and greater wheel travel (which in 95% of single axle trailers is not utilised), requires a shock absorber and the room to mount it (most shockers work best when vertical).
The suspension that rod1949 has linked to is Melbourne Trailer's own Independent Suspension, also know as a Knee Suspension or Symons Suspension (named after the inventor). Used predominantly by Coromal Caravans, they dont have a trailing arm, rather a wishbone suspension arm that pivots from the centre of the trailer as opposed to the front.

As usual Yonnee you've come up with the answers, nice one!

I acutally asked about the parabolic springs here at a local store and all i got was "You'd only put those on a light load" the info about not getting anything between the leafs all make sense now.

I've chosen the slipper option for my bike trailer... all gear ordered (major stuff) so I'll be updating that soon.