Spring width? Off road trailer experts, need some info!

[1speedlos]

I'm in the process of assembling parts for a trailer build, which I'll put up a separate thread for, but I have a few questions. For reference, I'll be using the trailer for both humble, lumber-store runs, as well as Big Bend/Yellowstone/backcountry camping trips, and bike race base camp duty.Like so many of you, I'm operating on an extremely limited budget, but have found some pretty interesting stuff for free!

I have an axle that has to be rated at 5,000 lbs., and an aluminum frame, some fenders, and odd bits. My plan, to keep the weight down for the TJ, is to use the aluminum frame for a base, bolt a steel tongue assembly to it, and build a steel frame for a flatbed with a removable rack for base camp use.

My first question- how far apart do the leaf springs need to be? The frame is 29" wide- should I bolt crossmembers below for mounting the springs wider?

Next, should the axle width be narrower than the jeeps, or as close to the same as possible? I have read that the vehicle rear wheel to trailer axle length should be at least 75% of the vehicles wheelbase, but what if it's longer? I have 85" of frame length to play with.

Eventually, I'll be putting air bags on it, and changing to independent axles on it, but for now I think I'll just put leafs and shocks on it. Any advice on figuring out which springs and shocks to use?

Thanks in advance for any advice, and I'm looking forward to sharing my build!

Los

 

[ntsqd]

Do you have pictures of the frame in question?
Sometimes it is better to just start from scratch even if it doesn't seem like it. Pre-existing items can force compromises that later bite you.

A trailer doesn't need to articulate. It really doesn't want to either since that moves the CG relative to the axle. So "in-boarding" the springs is a bad move. Place the springs as close to the tires as is reasonable.

I would suggest using reasonably long springs for their suppleness, but you MUST use dampers with such a spring. Leaves are not known for being supple and the shorter that they are, the less of this that they have.

Use a stiff damper. Since most dampers are designed for vehicles with people in them you very likely can't get too stiff.
Note that the Adjustable units typically only adjust the rebound. That is good for perception of ride quality in a vehicle where the body's mass greatly exceeds the suspension's (unsprung) mass. In an Expo type trailer you can't get close to that same mass/mass ratio so you need more rebound damping or the spring's rebound from a bump can attempt to launch the trailer & it's load.

 

[1speedlos]

Thanks for that. I spent 16 years working in the bike industry, so I know bicycle suspension very well, but damping adjustability with automotive stuff is new to me.
Oh, and I can't tell you how much I appreciate not seeing the effect of slowing shock stroke referred to as "dampening."
I'll have to think about whether or not it's worthwhile to keep this frame. Thanks for bringing up some good points!

Los