E350 Cutaway 4x4 w/ DIY Pop-Top Composite Camper Box (Build Thread)

[PathNotTaken]

The universal ES bushings already come that way, with a top and bottom piece and an internal steel sleeve that takes a 1/2" bolt, made to fit it a particular size hole (think lower durometer ones are 1.25") in a 1/4" thick frame. I guess you were thinking of something else, and you are correct that they don't provide much vertical movement.

The Ford mounts must be sponge material of some kind if they will compress .75". I wonder if adding another one of those instead of the spring might be better...

Yes I'm aware thats the way the completed ES Bushings come, I was initially planning on just using those before deciding on the ford factory mounts. I'm not using there universal completed bushings, just one of the poly pads they supply.

 

[jwiereng]

Do you have a retailer source for the huck bolts?

Do you have to use special L brackets? Or can you employ regular 6000 series alloy angle?

 

[jwiereng]

Aluminum Weldless Subframe Construction Technique Consideration
Thought I should share a new subframe fastening technique I am considering as opposed to welding the aluminum. The company XVENTURE makes military trailers as well as overland trailers with this technique. Essentially you rivet together the subframe with L brackets and these extreme duty blind rivets. They have a good video showing the construction here. Since they make these for the military and have a long history of doing so with zero failures, the method is quite proven. This would allow me to use aluminum without welding, and near zero user error (aka my crap tig welding). I would still probably weld some less crucial joints along with the exoskeleton part since the joint strength isn't as important there. This does add cost ($1 per rivet, and ~$100 of aluminum bracketry), but I wouldn't consider the cost difference that drastic compared to welding. This will however make my cross brace placement different as the brackets would take up some space.
View attachment 803624

For a simple T joint there is 16 rivets - at $1 each. But it is attractive because I cannot weld aluminum, and I have seen the alu welds crack on commercially made trailers.

 

[PathNotTaken]

Do you have a retailer source for the huck bolts?

blindrivetsupply is the cheapest I've seen, but haven't done much digging. The tool is very expensive so I would definitely look into renting/borrowing/used one.

Do you have to use special L brackets? Or can you employ regular 6000 series alloy angle?

just normal 6061 angle cut to size.

But it is attractive because I cannot weld aluminum, and I have seen the alu welds crack on commercially made

yep WAY higher risk of failure at the weld or more nearby in the HAZ, and countless examples with commercial trailers. Realistically a subframe will probably be fine either due to the strength the floor adds, but the huck bolts offer zero effort bombproof construction.

 

[jwiereng]

blindrivetsupply is the cheapest I've seen, but haven't done much digging. The tool is very expensive so I would definitely look into renting/borrowing/used one.

just normal 6061 angle cut to size.

yep WAY higher risk of failure at the weld or more nearby in the HAZ, and countless examples with commercial trailers. Realistically a subframe will probably be fine either due to the strength the floor adds, but the huck bolts offer zero effort bombproof construction.

Is there a hand powered economy priced rivet tool that could work? Renting the tool seems like a good idea, but might not be possible in my area Niagara Canada. I might not mind the arm workout to same some $$

 

[PathNotTaken]

Is there a hand powered economy priced rivet tool that could work?

There is not. There is no way around getting the special tool. Otherwise you could use standard rivets if you found some strong enough for you.

 

[PathNotTaken]

Subframe Mount Parts Mockup
Finally received all of the parts to mock up my subframe mounts. Things are looking pretty good. Only thing I plan on changing is the size of the bottom washer/keeper ring. (Aluminum part has since been redesigned)

 

[PathNotTaken]

Will you have any guide plates to limit lateral movement of the subframe/camper ?

I'm wondering about the load shifting sideways. The bolt can tilt off vertical (plumb).

Or is it not enough to worry about ?

I considered a guide plate, but I don't think it's necessary. At the top and bottom of the ford bushings, along with the aluminum subframe are three holes with an inner diameter near exact to the 1/2in bolt. This should prevent most of the movement. Also the box is mounted rigid to the cab, and the front mount doesn't have a spring. I think there will be a little lateral movement, but not too much. Most of the guide plate designs I've seen also seem like more of a backup plan than anything else. I know earthcruiser doesn't use guide plates on their Fuso.

 

[PathNotTaken]

Looks like I need to rethink my spring mounts. The problem is that the ford factory mounts require ~60ft-lb of torque to seat/compress properly. that amount of torque fully compressed the spring with ease: it requires very little torque to compress the springs. I could get a spring with as much as double the spring rate, but that still won't compete with the 60ft-lb. The weird thing is the factory mounts seem to permanently? deform some amount after initially being compressed. I could first torque those to 60ft-lb, then install the spring and torque that down lightly. The problem I see with this is that the ford mount could creep/expand over time which would result in the spring being compressed all the time and losing its travel, and the ford mount not compressed enough. I think this is unlikely though due to the fact the bottom and top of the ford bushing sleeve press fit into one another, but still a concern. Another problem is that in order to fit the bolt inside of the frame channel, I would need to cut a 3/4in hole in the bottom flange of the frame so it can pass through. Not the end of the world and I could fill the hole with a short bolt, but another concern. I guess that leaves me with three options:

1.) Redesign the spring mount to not use the factory rubber mounts at all
2.) Use them as is, get a stiffer spring and torque/compress the ford mount ahead of time, then install spring
3.) Ditch the springs and just go with the ford factory mounts

I think 1 is out of the question, so it's really a decision between spring or no spring. Interestingly enough, sportsmobile with their fiberglass body just uses the factory mounts. I'm sure I'd probably be fine this route considering how short of a platform it is, but the ~3/4in of movement the springs offer gives more peace of mind.

 

[rruff]

Another possibility is to do type of 3-point using the Ford mounts. Basically just put the rear mounts more inboard so they can easily let the chassis flex. Yes, you'll need to bridge across the frame rails, but I don't think that should be a problem.

I used ES mounts and put the rear ones in the center. I was worried that the camper would be kinda "floppy" but I've experienced none of that. It also slaloms great with the swaybars off, but I have upgraded shocks with high digressive damping. The only unpleasant sensation I've noticed is some fore-aft bounce if the road's undulation frequency is just right. I've only had this on pavement occasionally, not offroad. To be fair the truck when empty would ride like a bronco on some concrete pavement, so maybe the camper is just amplifying that.

 

[iggi]

Interesting project, you might find some useful comparisons to converted ambulances. My converted ambo is an E350 on the 138" wheelbase with a 12 ft box. With a crosswise high mount bed in the back it's roomy enough for two that I wish I'd trimmed a couple feet off the back while I did the roof raise to improve my departure angles. You must be quite tall if you can't fit sideways.
Most ambulances are built with aluminum frames and certainly see a lot of abuse. I haven't yet seen a report of a frame fracture, even from people that have installed multiple windows and cut parts of the frame out to achieve it.
The ambulances boxes are quite overbuilt and heavy. I'm about 9600 lbs currently loaded up with water, fuel and gear.

 

[PathNotTaken]

 

[PathNotTaken]

Subframe Assembly
Assembly has gone smoothly for the most part. I first mounted all the painted steel body mounts to the frame using plastic mounts, then bolted the cross members in. These plastic mounts are 3D printed and are temporary. I'm using these instead of the final rubber mounts as they are rigid and will not flex, allowing me to keep everything aligned and square during assembly.

Frame-members are 6061 2x2 3/16 and 1/8, and some 1x2 1/8. Between the steel body mounts and aluminum framing are three layers of protection against galvanic corrosion: paint, anti-corrosion tape (Hesken 3543), and marine ant-corrosion compound (Lancote) all over the connection. All bolts that pass through the tubing have an internal aluminum sleeve to prevent crushing and red loctite/distorted thread nuts for permanent installation. I then began laying out all of the various members to make the initial framing. This took quite a while to get everything aligned perfectly.

L brackets made of 6061 1/4in 3x3 angle connect the tubing using BOM Rivets. Each rivet requires ~6000lb clamping force to shear in place, and has a tensile strength of 3250lbf and shear strength of 5100lbf. This construction technique has many advantages over welding, but it does however add cost and require a specialty tool for install. I got the idea for this construction technique from XVENTURE trailers, who have a proven track record of zero failures being used for overloading and as heavily abused military trailers. When installing the BOM Rivets, I use a generous portion of lancote to prevent galvanic corrosion. While it worked great for this purpose, the Lancote got over all my tools and was a mess to clean. I am switching to a chromate primer and doing a wet install (got this technique from aviation manufacturing). This should make less of a mess and not require clean-up before painting.

With my subframe being as low as possible, I didn't end up having as much clearance as I thought over the fuel tank components. Because of this, I'm currently in the process of building a steel x brace that is less tall and will greatly improve the torsional stiffness with the minimal height I have to work with. Overall everything is incredible strong and overbuilt, per usual!

Next steps are to finish this x brace, start framing the drop down shower pan, and then frame out the lowered entryway.

 

[rruff]

Awesome! Thanks for the update.

 

[jwiereng]

Looks great. Love the photos. Please elaborate on the description about the Chromate primer and wet install