Hitch ball through crossmember?... Maybe..

[sixbennetts]

Yup. It looks like he mounted the hitch ball to the crossmember, but reinforced it first. Considering that as well, maybe a big [ shape that slides down over the crossmember AND frame sides, and bolts through that group of holes in that area. That would take most of the hitch ball weight off the crossmember and place it on top of the frame rails.

I love his idea of cutting up a cheap nylon chopping block to make a thick washer under the hitch ball! Clamp it in a vice, hit it with a small hole saw for the ball shank, then a bigger one for the outer edge! Adding a big thick washer, and the weight is spread over a larger area. Brilliant!

My wife, "Honey! Have you seen the chopping block? I'm making dinner and I swear I saw it in the....."

 

[sixbennetts]

Large "[" shaped reinforcement plate over the forward crossmember. Bolted through the frame rails with existing holes, padded with urethane sheet, and hitch ball drilled through both with a nylon or urethane washer.

Yup. That'll do, pig.

 

[sixbennetts]

Probably just go with the urethane sheet, but yeah, just thinking out loud. I love the idea of finding cheap alternatives that work. Like the frame of the trailer becoming the subframe.

 

[sixbennetts]

Added the urethane pads to the mock-up drawing for the front mount.

 

[Zuber]

So, you will have two complete sets (4 each) of leaf springs at the back? One set on the truck and one set supporting the trailer house. Seems like that will be very floppy, where on a side hill the trailer springs will be in tension - a situation they never were designed for. Also, on large vertical movements, the trailer can be moving up while the truck frame is on the way down. Two bodies with close to the same weight attached by a spring. This won't end well.

It would be a better design, to join the two weights and have one set of springs (the truck springs) tuned correctly and controlling the one mass.

The stepped frame has very strong rigid members at the front and weak twisty members to the back. You are using them in reverse. To use the strength to strength, you should essentially load the trailer backwards with the ball hitch at the rear.

Hopefully, this is still at the white-board stage of design and other designs are being considered.

 

[sixbennetts]

The trailer won't know it's not on it's tires, encountering the exact same side-to-side forces it handles when it goes down a trail. It will act just like it always does, tipping to match the terrain. And as I said above, I'll be adding shocks to the trailer axle, as well as the hitch ball area, (to arrest drastic, sudden side-load).

I'll take it for a spin, and add limiting straps if I have to.

 

[Zuber]

The trailer won't know it's not on it's tires, encountering the exact same side-to-side forces it handles when it goes down a trail. It will act just like it always does, tipping to match the terrain. And as I said above, I'll be adding shocks to the trailer axle, as well as the hitch ball area, (to arrest drastic, sudden side-load).

I'll take it for a spin, and add limiting straps if I have to.

Not quite. Instead of the trailer sitting on the ground, it is now attached to a tall frame 3 1/2 feet above the ground. It will see a lot more side to side pitching.
Also, it is not just bouncing on the surface of the ground, it is attached to an equal weight that is pushing it up AND pulling it back down. The trailer springs are much, much softer than the truck springs. It will look like one of those little statues with a spring for a neck.

 

[sixbennetts]

We'll see how it goes with the shocks and limiting straps. I can always change it.

 

[dan85]

The trailer won't know it's not on it's tires, encountering the exact same side-to-side forces it handles when it goes down a trail. It will act just like it always does, tipping to match the terrain. And as I said above, I'll be adding shocks to the trailer axle, as well as the hitch ball area, (to arrest drastic, sudden side-load).

I'll take it for a spin, and add limiting straps if I have to.

would be wary about how high it will all end up and then how much sway that induces. you might find attaching your truck chassis directly to your trailer chassis (with all trailer running gear removed) and using spring mounts between the two chassis would be a cheap and effective way to mount it and reduce the height and excess movement.

 

[sixbennetts]

Very good advice, thanks. That's my fall-back position. After all, nothing is permanent, right? I'll have a choice to go above or below the axle with the trailer springs. Most of the campers I've looked at had very little suspension travel, only a few inches at most. And the shocks I'll be adding between trailer frame, (subframe), and truck frame will easily handle a sudden sideways fling, I think. With the front pivot, and the trailer axle being just behind the rear tires, I'll be able to mount it as low as the truck frame step dictates without having to worry much about scrubbing a rear tire on the camper frame. Except for the occasional jolt, the distance between camper frame and rear truck tires will be pretty much constant.

And if not, cheap, light 16' campers are a dime a dozen up here in the Adirondacks. If it brakes it, I'll replace it. Disposability.

 

[javajoe79]

I don't like the hitch ball idea at all really but I definitely wouldn't put a soft washer under the hitch ball. If you want to cushion that assembly, cushion where the reinforcement bolts to the frame. The cushions you have drawn between the frame and the reinforcement plate aren't really doing anything. either.

If you're cutting the trailer tongue back anyway, you should just alter your crossmember or fab a replacement crossmember with a large heavy duty bushing to bolt to. That way the crossmember still does it's job as a structural component but the camper mount is still "soft"

Using the trailer leaf springs sound like you will end up with a rather tall camper. Like others have said you should just let the camper frame rest directly on the truck frame and make some spring mounts in the back. Or, solid mount the back and spring mount the front as other who know these trucks have indicated, that is what the truck frame design is meant for.

 

[John M.]

I'm a visual thinker, so here's some thoughts. Hitch ball will have a urethane washer under it. Haven't decided whether ball plate will be bolted to the two crossmembers or welded, (they will be steel, now aluminum as shown). Urethane pads between plate and frame rails. Haven't decided which way the U bolts will go, probably nuts up so they'll be easy to tighten if it gets loose. Obviously, the trailer hitch itself will be shortened considerably to get the front of the camper as close to the cab as possible. If I measure correctly, I *might even get a couple spare tires between the camper and truck cab.

About the trailer's stock axle. Obviously, I'll replace it with something stronger, or maybe sleeve it with heavy wall tubing. But it will be square or flat rectangle in profile, not round. I'm also considering a simple underslung truss under the axle, depending on how wide the spacing is between the trailer springs compared to the truck frame width.

Where did we land on the A, B, C, or D on the first image, re: axle placement on the truck frame? I'm doing my reading here, and I thought I read the rear 2 points on a single-point-forward 3 point subframe should be just in front of the rear spring hangers. Sound right? Obviously, I *might have to move the trailer's spring shackles to meet that point.

When thinking of attaching the trailer to the truck chassis using the trailer suspension, you have to consider the "slinky effect" of sprung mass on top of an already sprung platform (the truck frame). This thing might have some very surprising and non-linear leaning behaviours! I think you might be designing a "shifting load".

Also, vehicle suspensions are designed for a life in compression, with roll dampened by shocks and struts. Rarely is tension applied to an axle and set of leaf springs, and usually it's no more than the mass of the axle and wheels. The design you are proposing will need shocks and some limiting straps.

It is a novel approach and may have it's benefits, but will have some serious issues to solve along the way.

J.

 

[sixbennetts]

When thinking of attaching the trailer to the truck chassis using the trailer suspension, you have to consider the "slinky effect" of sprung mass on top of an already sprung platform (the truck frame). This thing might have some very surprising and non-linear leaning behaviours! I think you might be designing a "shifting load".

Also, vehicle suspensions are designed for a life in compression, with roll dampened by shocks and struts. Rarely is tension applied to an axle and set of leaf springs, and usually it's no more than the mass of the axle and wheels. The design you are proposing will need shocks and some limiting straps.

It is a novel approach and may have it's benefits, but will have some serious issues to solve along the way.

J.

Yes, both shocks AND limiting straps are planned. And correct me if I'm wrong, but the sprung subframe that is so popular here for adding a composite 'house' to the back of a fuso has the same potential for the 'slinky effect'?

I'm simply suggesting using the trailer frame AS the subframe, and controlling it's movements accordingly. Same spring travel distance, (up and down), same side-to-side tilt to follow the rear truck frame twist, (hitch ball), and same limiting of fore-aft movement, (hitch ball again), just like a standard 3 or 4 point subframe used here on expo for years.

But for a lighter load.
Using readily available, less expensive, off-the-shelf parts.

 

[SkiFreak]

And correct me if I'm wrong, but the sprung subframe that is so popular here for adding a composite 'house' to the back of a fuso has the same potential for the 'slinky effect'?

I would argue that these are two very different setups, using different types of springs and movement.
But hey... it's your build and you can do whatever you like.

As others have noted, it's an interesting concept, so I will be interested to hear how/if it works out for you.

 

[quickfarms]

Unless the Fuso rides harder than an FT900 you are over thinking this.

When I mounted the HiLo on the FT900 I had air bags planned to go between the trailer and the truck bed but after tuning the truck springs to my actual weight it rides better than my wife’s Honda.

For my front mount I used a gooseneck coupler welded to the bottom of a new crossmember in the shortened trailer tongue.

There is a subframe connected to the original suspension mounts that contains fork pockets

The rear of the trailer frame is bolted to a cross beam that attaches to the bed using container fittings.

For this build I would mount large angles to the outside of the frame using the crossmember holes and longer flange bolts. I would bolt a thick wall box tubing to the angles across the frame. A ball would be mounted in the top of the box tubing

For the rear I would attach a sub frame to the original spring mounts and use the truck bed springs and locating guides to attach the trailer to the truck frame

Let me know if you need some pictures