pivoting frames and mounting campers

[KiwiMtnClmbr]

I know pivoting frames are used a lot on big trucks, and for good reason but what about small pickups like a Ford Ranger?

I'm planning the build of a camper on a flatbed (with back wheel cutouts for having a low as the possible center of gravity). The vehicle will be a Ford Ranger chassis cab (single cab sold without the bed). The flatbed will be about 2.5m long x 1.9m wide x 1.9m tall (8.2ft x 6.2ft x 6.2ft). The fully laden weight of the camper (with everything inside) will be about 6-700kg (1500lb). I'm in Italy and we don't have the choice of bigger heavy-duty trucks like you in the US, so I'm trying to build a hard side camper with all the comfort for long expeditions, but maintaining a small size (with no more overhand than the stock bed) not to make the small pickup unstable in offroad.

Since the frame is much shorter than big trucks I don't think it will have so much flex to need a real 3 or 4 point pivoting frame, but maybe mounting with captured springs can give some help to articulation? What do you guys think?

Check out Tanuki's build on a Ranger.

Yet Another Camper Homebuild Thread

although its more of a barge than a yacht...... A couple of years in the planning, and now 6 months into the actual build Campalot (".......its only a model" - Monty Python quote-ish) has finally made it onto the truck for a successfull test drive Having spent much of the last 7 years on...

expeditionportal.com

Build histories on the french language forums, casa-trotter, which you can read pretty well in Chrome via translate.

Autoconstruction d'une cellule en résine polyester pour Ford Ranger - Page 2 - Casa Trotter

Naissance d'Euskal-Go-bi - Casa Trotter

more ranger stuff:

Choix d'un porteur, Ford ranger ? - Casa Trotter

 

[rruff]

I know pivoting frames are used a lot on big trucks, and for good reason but what about small pickups like a Ford Ranger?

No, you don't need it. They are stiff fully boxed frames. Pivots are only needed on trucks with a flexy C-channel fame.

There is a good deal of tail-chasing involved with trying to get both articulation offroad, and stability and handling on-road. Montypower went with good shocks, a high-articulation leaf pack, and no swaybars for his F250+camper. If offroad performance is your priority that is probably the best approach, but you need to be more careful cornering. Plenty of people prefer good stability with stiff springs and swaybars on both ends.

 

[Paul B.]

We went through all this with our F350 4 door long bed. In the end we just bolted the camper to the frame. Through the utility bed. I think with that sized truck and that kind of weight, you're not gonna have any problems. Your main problem with the whole rig is going to be keeping the weight down. We ran Ford Rangers down in the Saline Valley for years and it's easy to overload those things. Best of luck with it. I really don't think you need any articulation mounting. You could throw the springs on the bolts if you want, why not? It's not that expensive. Just don't put too much weight on the entire rig. We went down that road more than once. Couldn't put enough stuff on it for long trips with wife and two kids.

 

[filippomasoni]

@KiwiMtnClmbr I'll check out those posts, looks like there's a lot of valuable info out there for the Ranger with similar project like mine. Even though it looks like those are for the extracab and I'll have a single cab.

@rruff and @Paul B. Thanks for the advice. Nice to know that's not a thing I should worry about for my build, makes it much simpler to start with. I know the importance of suspension and I'll take care of it once I have the camper fully build and I know the actual weight distribution so that I can choose a suspension setup base on that. Suspension is also something that can be upgraded down the road based on how it behaves both on and off-road and how I prefer it. While the flatbed chassis is something I have to make before the camper box and can't be changed after the fact.

You could throw the springs on the bolts if you want, why not? It's not that expensive.

Do I need to design an attachment specifically for springs or the system is basically just springs on the bolts wherever the bolts are located? Obviously, I'd have to account for the space of it.

Keeping weight down has been my main goal since the start. I'm making spreadsheets of every system component I'll add to the build with weight, specs, etc, and choosing everything with weight at the top of my priorities. I'll travel by myself so I won't have that much stuff as a family of 4, but I'm a photographer/videographer and have a lot of camera gear, computers, hard drives etc. My current rough estimate is 700kg total for the camper, fully loaded with all gear and 200L of water (that would be my goal so that I have a very long autonomy, but maybe it's too much and I'll settle for 150L).
The Ranger here in Italy comes with a GVM of 3270kg so I'll have about 500kg to space. I've seen on some posts they upgraded the GVM of the ranger to 3500kg so I guess the chassis is made for that weight. My goal is anyway to stay under 3000kg and I know that it will eventually grow from my estimate, but I'm doing my best.

 

[KiwiMtnClmbr]

Somewhere in those links I posted are references to getting the GVWR of the ranger uprated to/over 3k. Also, I think some failures and issues with that goalset - tread lightly. Even if the frame could handle it, why run that heavy if you don't have to? Keep after the weight savings I say!

 

[filippomasoni]

Somewhere in those links I posted are references to getting the GVWR of the ranger uprated to/over 3k. Also, I think some failures and issues with that goalset - tread lightly. Even if the frame could handle it, why run that heavy if you don't have to? Keep after the weight savings I say!

I read about it in the thread. The fact it can be upgraded to 3500kg means the chassis is strong enough for that, which is a great thing, means I have a greater "real margin of safety". I'll look into it, but I doubt Italian laws will allow that. Anyway, I don't want to have such a heavy vehicle, my plan is to be below 3000, so if I end up going a bit more I'm still under the 3270kg original GVM.

I'll start asking some questions over there, as it seems more on the topic than here.

 

[Christian]

I wouldn't be worried too much about vibration form the engine and chassis... There's very little that will stop the shake rattle and roll found on corrugated dirt roads! There's always going to be a certain amount of vibration. Looking at your drawings, in theory if you have your front and rear pivots in the center line of the chassis, then you shouldn't need the complexity of connecting arms like you have drawn in... A simple pivot and greasable bush would surfice. Then, as the 4 'points' are rigid, but can only flex in the direction required, you could do away with the Lord rubber things (that look like oversized tractor cab mounts), and replace them with 4 decent shock absorbers to allow the travel required while giving a dampening effect and not a restrictive effect found by the Lord system... Just my thoughts.

Hi Sitec! I didn't see your reply, sorry!

I didn'd explain my design well enough, it seems. The LORD mounts are used tractor cab mounts. They act as the cross-sectional mounts/axis in a 3-way setup. They control movement in the front, securing box and cab to the chassis, while allowing some flex/vibration dampening.
The Watts linkage acts as the longitdinal bearing in a 3 way setup, but with the ability to flex vertically. It might not be needed, but it will ensure some comfort.

The downside is, that having the box being able to sway in the rear, makes cornering more unstable. That is why I have added the standard truck suspension airbags on either side. They will support the weight in the rear, while dampening vibrations and bumps transferring from chassis to box.
On paved roads, the airbags will be isolated, so side stability is maintained. In rough terrain they will be linked allowing air to move sideways, so the chassis can flex, without stressing the box.

 

[Sitec]

The downside is, that having the box being able to sway in the rear, makes cornering more unstable. That is why I have added the standard truck suspension airbags on either side. They will support the weight in the rear, while dampening vibrations and bumps transferring from chassis to box.
On paved roads, the airbags will be isolated, so side stability is maintained. In rough terrain they will be linked allowing air to move sideways, so the chassis can flex, without stressing the box.

I contemplated this, but then decided to utilise the Anti Roll bar from the front of our donor truck. It was sat there doing nothing, and it's job is to do exactly what I needed under the rear of our Hab box, so I went with that! Time will tellif that was the right decision!



The small piece of 100 x 50 RHS sat between the chassis and hab box rails was there to keep the hab box at the correct distance from the chassis while I mounted the anti roll bar in place.

 

[Joe917]

Hi Sitec! I didn't see your reply, sorry!

I didn'd explain my design well enough, it seems. The LORD mounts are used tractor cab mounts. They act as the cross-sectional mounts/axis in a 3-way setup. They control movement in the front, securing box and cab to the chassis, while allowing some flex/vibration dampening.
The Watts linkage acts as the longitdinal bearing in a 3 way setup, but with the ability to flex vertically. It might not be needed, but it will ensure some comfort.

The downside is, that having the box being able to sway in the rear, makes cornering more unstable. That is why I have added the standard truck suspension airbags on either side. They will support the weight in the rear, while dampening vibrations and bumps transferring from chassis to box.
On paved roads, the airbags will be isolated, so side stability is maintained. In rough terrain they will be linked allowing air to move sideways, so the chassis can flex, without stressing the box.

Ask White Acorn what they think of using LORD mounts : https://expeditionportal.com/forum/...failure-or-a-gxv-failure-pic-included.110780/

Before you start engineering a mounting system not approved by the chassis manufacturer you better be pretty sure of your abilities.

 

[Christian]

I contemplated this, but then decided to utilise the Anti Roll bar from the front of our donor truck. It was sat there doing nothing, and it's job is to do exactly what I needed under the rear of our Hab box, so I went with that! Time will tellif that was the right decision!

View attachment 687107

The small piece of 100 x 50 RHS sat between the chassis and hab box rails was there to keep the hab box at the correct distance from the chassis while I mounted the anti roll bar in place.

That's brilliant! So simple, but I have not seen that anywhere before. Really great idea, and if you find it too stiff or too soft, it would be easy and reasonable to have a new one made.

 

[Christian]

Ask White Acorn what they think of using LORD mounts : https://expeditionportal.com/forum/...failure-or-a-gxv-failure-pic-included.110780/

Before you start engineering a mounting system not approved by the chassis manufacturer you better be pretty sure of your abilities.

We actually discussed that a few posts back. But it seems they did not used the large washer which LORD and other manufacturers recommends in order to "safetify" the mount.
These mounts from a load of different suppliers are used in all kinds of applications without failures like that. But it must have been either faulty or used incorrect to fail like that.
I tend to believe the latter.

I am kind of sure about my abilities... But does that mean I think I am right, or that I don't trust my own ideas? ;-)
I think what I plan is going to work, and do what I want. But I do know some of us might have a slight tendency to hyperfocus on our own designs, that's why I come here to have them evaluated and questioned.

But it isn't that far from the body builders manual in where the loads are applied to the chassis.

 

[Sitec]

If you find it too stiff or too soft, it would be easy and reasonable to have a new one made.

If it's too soft there'll be a big rubber block go in where the temporary 100 x 50 RHS is... If it's too hard, I'll get the flap disk out and make the Anti Roll Bar thinner in the middle! (I joke of course! )

 

[Sitec]

Before you start engineering a mounting system not approved by the chassis manufacturer you better be pretty sure of your abilities.

I hear you. With that in mind, I tend to build in a 'get out of jail' card for everything I build that is in unchartered waters for me. The system I've built (though used many a time before with seperate subframes) is slightly different in that I'm using the chassis and Hab Box as the bottom and top subframe to save weight and height (which negates the need for a subframe that sites the pivots above the twist axis on the chassis, which in turn builds in unnecessary loads). I have all the points in line with or as close to spring mounts as possible, the theory that the chassis is just there as the lower subframe and the springs will carry the load. I have the bathroom and shower walls located above where the Hab Box pivots are, and have additional diagonal spars internally in these walls so the load is carried through the Hab Box meaning the body acts as the upper subframe. I've also built it with a 100mm gap between the chassis rails and the Hab Box base so that if it all goes belly up, I can at least slide a pair of 100 x 50 RHS rails into the gap and make it rail on rail. Wish me luck!

 

[Christian]

If it's too soft there'll be a big rubber block go in where the temporary 100 x 50 RHS is... If it's too hard, I'll get the flap disk out and make the Anti Roll Bar thinner in the middle! (I joke of course! )

Just heat it untill red in the middle ;-)

 

[rruff]

I contemplated this, but then decided to utilise the Anti Roll bar from the front of our donor truck. It was sat there doing nothing, and it's job is to do exactly what I needed under the rear of our Hab box, so I went with that! Time will tellif that was the right decision!

View attachment 687107

The small piece of 100 x 50 RHS sat between the chassis and hab box rails was there to keep the hab box at the correct distance from the chassis while I mounted the anti roll bar in place.

I'm not sure that is actually what you need. You have the pivots to allow articulation of the frame, and to reduce/eliminate stress on the camper. It seems that the swaybar would simply work against this... ? I think it would be inferior to the spring loaded rail on rail systems, because they have a solid connection between the frames (well, they are spring-clamped together) allowing for good "normal" performance, but will allow some motion when the twisting stress gets too high. When this happens, some stress gets imparted to the camper, but hopefully not too much. With your pivoting system the swaybar does basically nothing to resist small motions (like you'd encounter in normal driving), but imparts high stress when you have a lot of twist.

If there is too much sway on a pivoting system, I think shock absorbers between the frame and subframe would be the best. This would damp any sudden motion between the frame-subframe but still allow full articulation and be stress free when you get crossed up offroad.