Mounting a composite camper box on 4x4 E350 chassis

[fjefman]

@rruff I see your point and maybe I'm being completely dense but I still think much of this concern over stiffness/flex on a vehicle this small is just hyper concern with no supportive data suggesting that. Again, I'm open to admit that I'm just being ignorant, but I've been considering this for year and have spent countless hours researching and reading and watching and talking with people and have yet learn anything that says this is a stupid idea. Is a pivoting subframe better? Sure. And building with carbon fiber and titanium would be better as well. Is it necessary? I don't think so. I mean there is a point at which the box is so stiff that it keeps the chassis from flexing at all. That is how all OEM van bodies function after all....and exactly how SIP work...individually the components are flexible, put them together and it has very different properties.

That said, you did get me thinking about minimal frame reinforcement up front and poly mounts.

As to my panels. Right now I'm looking at getting a precut flatpack kit from GEX. They look like the only option for any sort of custom work. https://www.globalxvehicles.com/diy.html. That said, if there are other options then I'd love to hear them.

 

[rruff]

I'm not sure that a van body is that stiff in torsion, since they are open at the back. If there was a very similar case... like maybe double-wall composite foam closed refrigerator boxes that are hard mounted and do just fine, that would be supporting data for your case.

Yes, you can make a box that is stiff enough to keep the chassis from flexing. But that box then needs to be *strong* enough to take very high loads and not crack. Plus this increases the stress on the chassis, cab, etc... that it may or may not be strong enough to endure.

Have you asked GXV about this? Total Composites also does custom campers. The owner of that company weighed in on the previous page.

 

[CalgaryMcLean]

The stock E-350 frame is quite flexible. I don't have the measurements in front of me, but it is easy to get more than 4" of vertical displacement or twist between the back of the cab and the frame when measured at the crossmember just behind the gas tank. More than 10 degrees. And this is with a 138" wheelbase. A 158" wheelbase would have more twist.



The stock Ford spacers used when mounting a typical commercial body wouldn't add much stiffness.



Commercial bodies flex along with the frame.
Ambulances are very stiff, but also very heavy.
Average RVs flex and have poorly built interiors that also flex, until they fall apart.
A normal cargo van is going to be stiffer than a bare chassis, but will have some flex and can have door alignment issues when parked a bit off camber.

I suspect that a composite camper body is going to be less forgiving to flex that a stock, steel van body.
The composite camper body is going to resist the twisting forces with little flex until it can't and then something gives way.

I don't expect that any of the composite camper body manufacturers are going to commit to how much stress their products can safely resist. Too many variables.
They will likely say to isolate the camper box from the frame flex or make sure to stiffen the frame "sufficiently".

 

[DirtWhiskey]

Forget the 3 point engineered mounts. Not saying they don't work. Just saying they are not as widely used or clearly understood. Solid mount in the rear and spring mounts mid and front. Literally 10s of thousands of water and tankers trucks all over the continent doing extreme duty with extreme weight. How the military (M1079 M1978 et al) does it too. Just my 2 cents.

 

[carterd]

I am contemplating a composite box on an E-350 and think using Earthcruiser's CORE subframe concept for the Isuzu NPR / Fuso might be a viable option. The CORE chassis uses a low profile subframe that rigidly attaches in front and uses spring mounts for the rear positions (8 mounts total). The CORE chassis/subframe was tailor made for composite bodies. A similar subframe could be mounted to the E-350's 12 stock mounting points. This would place the floor of the body about 3-4 inches above the frame rails. The subframe would need to have an offset around the axle hump on the frame.

 

[Bikersmurf]

How are Ambo boxes mounted?

Ambo boxes are well built, stay connected to the vehicle frame mounting system whatever that is and survive rollovers. These boxes have to add stiffness to the frame one would think and that may be good or bad from an off-road perspective.

Ambulance Rollover Crash - Crash Testing by Braun

www.ems1.com

Crestline ambulance boxes are sold mounted. Based on memory it is mounted using 1/2” aluminum plates welded to the bottom of the Aluminum cage/box. Solid mounts using 5/8” bolts or something similar. The box essentially has no flex, and I’m sure it stiffens up the e350 frame.

 

[PathNotTaken]

Reviving this thread since theres was a lot of talk about people wanting to build composite bodies on e350 campers, but from what I can tell @CalgaryMcLean is the only one to go through with it. Are there other examples, or did people change their mind?

I am in the planning stages of my build, and am leaning towards an e350 chassis with a composite box. I off-road heavy so durability and longevity under these conditions is a priority. I think mounting the box rigid to the frame/cab in the front, combined with spring mounts in the middle/rear makes the most sense.

In addition to this, I don't think anyone has mentioned stiffening up the frame itself? This is typical in off-road racing industry. It seems in an ideal world a frame has zero flex and suspension does all the work, but since this isn't a reality, which not try to reduce the flex as much as reasonably possible? The only penalty I foresee is weight from the extra material used for cross bracing, however I think a well engineered brace wouldn't add much weight. This would give a better foundation for either a springs or pivot system.

I also do think @ScottPC point about the scale of an e350 camper being much smaller is a good one. These vehicles are much smaller and lighter to begin width than basically any of the other composite box mounting-ready chassis (earth cruiser, mog, etc).

 

[rruff]

The only penalty I foresee is weight from the extra material used for cross bracing, however I think a well engineered brace wouldn't add much weight.

I recall someone with a Tiger saying the subframe was just square steel tubing, ladder style with edges... and it was welded to the top of the truck frame. I'd be mostly concerned about the front cross-member where it attaches to the frame, where there is a transition from stiff to flexy. Is the front of the E series boxed like the pickups?

Tiger made a few with a pivoting frame too. I don't know if this was to solve a problem or just to try out, but it didn't handle well and they stopped doing it.

 

[Victorian]

There are 4 Total Composites campers mounted on E series trucks. All have some sort of articulating subframes either build by the customer or our builders. It's up to the owners and builders to share details of those trucks. We are just the box supplier. But in any case, I thought I should let you know that it has been done

 

[PathNotTaken]

There are 4 Total Composites campers mounted on E series trucks. All have some sort of articulating subframes either build by the customer or our builders. It's up to the owners and builders to share details of those trucks. We are just the box supplier. But in any case, I thought I should let you know that it has been done

Thanks for letting me know. I hope they share as I'd love to see their builds!

 

[PathNotTaken]

Overland explorer Vehicles are supposedly working on one. They posted a teaser on one of the social media platforms a while back. Using new cutaway with a quigley conversion as a base chassis. Might release more info by end of year.

I like the whole idea but have a few reservations including finished height (if doing an overcab camper), available payload after conversion, and axle ratings. Front would obviously get swapped out but the door sticker wouldn't. Likewise the rear axle is only tagged for 6,050 IIRC to prob rated higher by the mfr. And I suppose tire ratings might be a concern. Of course lighter build would be better.

For the frame would the F450 E450 be beefier ? Beefy enough ? I realise you'd prob want the 138"wb for compactness which is E350 only.

e350 is preferred because of short wheelbase + shorter overall length (for same size habitat) due to hood design (~25in). I don't think payload is remotely a concern with a well thought out build. Finished height I agree is too tall imo to be standing height for me (6'6), which is why I'm wanting to do a raising roof. However, my travel style is different from most and I see why a fixed roof is preferred by most. Anyways, I don't want to derail the thread anymore considering this is one of the few discussing mounting composite campers on the e350

 

[CaptainBuilt]

2014 Ford E350 with 12ft box. Here's what's under the floor. No room for flex.

 

[Daviticus]

For what its' worth, the 2000 Wheeled Coach E450 Ambulance I'm converting to a camper at work uses OE Ford body mounts in OE locations along the frame, with the box hard mounted to the cab. Likewise, my 1995 Quigley E350 DRW with an enclosed service box also uses OE Ford body mounts along the frame, and the box is hard mounted to the cab. I can't speak for the ambo, but I definitely hear movement when my Quigley is flexed out, to the point where I am concerned I'll rip a mount out of the service box. I planned on losing the service box in favor of a pivot-mounted flatbed with a removable composite box, and a rear cab cap to separate the cab from the habitat.

 

[Steve_382]

Overland explorer Vehicles are supposedly working on one. They posted a teaser on one of the social media platforms a while back. Using new cutaway with a quigley conversion as a base chassis. Might release more info by end of year.

I understand they are thinking about 2 models with garages large enough to keep bicycles inside and hope to have one ready for Expo East later this year. It really sounds like what I may be looking for. Just a bit over 20' long overall on the 138" wheel base sounds very interesting. Hope they will incorporate the vehicle cab seats into the layout. I can sacrifice some winter insulation for the increased living area and ease of moving between the cab and the cabin. Also, it would be nice to be able to recline the front seats while driving or just parked looking at the scenery.

LITE Industries/Overland Explorer Vehicles

 

[b. rock]

I just checked out their website and it's $122-146k for a hard sided camper, not including the truck or subframe? That tempered my enthusiasm a bit. A composite box (unassembled) is in the range of $18-20k. Subframe, call it $12-15k. I'm not seeing the big jump from there?

Then again, I saw an Aeon RV over the weekend and thought it was cool. $220k, however they are still selling.