Mounting a Composite box to E350 Cutaway Chassis?

[VanHallen]

Originally Posted by fjefman

Lots of great ideas on that...and something I think all of us would like to know. But none of that is easy or simple to figure out, and maybe I'm just being pessimistic, but I doubt any of the normal "builders" out there will be providing any of that data to our satisfaction anytime soon.

Are you thinking you are going to wait until you have all of those answers until you start your build?

If not, what is it that you have to know/learn before you are ready to make a decision on what you are going to do with your attachment of box to cab and frame?

Genuinely interested in your thoughts on this...what factors will really influence your decision to go forward or not? At some point there is going to have to be a leap of faith, right? Just how far are you willing to leap? ;-)

I suspect one, if not more of us is going to kinda "lead the charge" on this "composition box" idea and learn as we go. However, in all honesty, in my mind, the charge has already been led by everyone out there doing near-solid mounting of boxes to frames for the past many decades.

Jeff

Ironically, I just began thinking about this scenario a few weeks ago. Don't get me wrong I've looked at ECs, Nimbls, SMB Classics, various truck campers, but this specific box on e350 is new to me. The SMB Classic and anticipated launch of Field Van, lead me down this path.

Now that I understand my options a little better through feedback here and other independent research. I am actually moving forward with purchasing an e350 Cutaway as the timing of that will kickstart everything else that has to happen. There appears to be a long lead time for these and buying one is not as straight forward as ordering online or going to the dealer like it is for a Transit or F series. Any suggestions from the group for getting a 2021+e350 would be appreciated?

I just bought a 2003 SMB RB v10 to start using, make updates, and improvements. I really like how it's laid out so having it will be fun and will inform much of the design and features going forward. I'll sell it as the new project is ready to roll.

[b. rock]

Originally Posted by VanHallen

...It would be useful to know what Landcruisers and G Wagons have used when they've mounted smaller but similar type boxes...

Apples and oranges. Much smaller/shorter dimensions which means less weight and less bending forces. Land cruisers are one ton-ish construction (3/4 ton I guess?) with very minimal frame movement off road. I wheeled the hell out of my 80 series and never saw or experienced anything that would indicate frame twist to any noticeable degree, even with 23 yr old body mounts past 200k miles.

Maltec lists their fully built weights to be between 5800-6800 lbs. Earth Cruiser AUS shows their XTR more around 6600-8300. Both a bit less than a fully built E-series (mine is 8400lbs completely empty). Also worth noting, some of other cruiser builds are also slide-in campers on flatbed platforms.

However if you wanted some people state side to ask, think Bison Campers is building some campers for the Gladiators, you could try asking them what they're doing (and I think foam is an option? not positive). ATC4x4 has mounted some similar foam construction campers on a few truck platforms, although I'm not sure how off road oriented they are and he's a one man band. Other ideas would be asking Earth Cruiser US about their Terra Nova (which specifically mentioned a kinetic mount) or the new kids on the block, TruckHouse.

[VanHallen]

Originally Posted by b. rock

Apples and oranges. Much smaller/shorter dimensions which means less weight and less bending forces. Land cruisers are one ton-ish construction (3/4 ton I guess?) with very minimal frame movement off road. I wheeled the hell out of my 80 series and never saw or experienced anything that would indicate frame twist to any noticeable degree, even with 23 yr old body mounts past 200k miles.

Maltec lists their fully built weights to be between 5800-6800 lbs. Earth Cruiser AUS shows their XTR more around 6600-8300. Both a bit less than a fully built E-series (mine is 8400lbs completely empty). Also worth noting, some of other cruiser builds are also slide-in campers on flatbed platforms.

My understanding with the G-Wagen and Landcruisers with habitat is that they are cutting the frame and lengthening the wheel base to 130in. I do agree they're are quite different so I haven't gone down that path just yet. I have looked into Maltec...just haven't gotten a response.

Check out the G-Wagen build below. It would be nice to know if they did some sort of progressive spring mount, fixed mount or some other type, even though it is apples to oranges:

Check this out at 50secs (the youtube series is pretty cool too):

https://www.youtube.com/watch?v=c-7OV65-vdk

As Far as weight goes, the e350 chassis with 7.3 v8 is ~5000, the conversion is ~400, the box is ~1600. So it will depend on how it's all built out" subframe, tank size, spare, poptop, bumpers, winch, etc. I might not make the goal but at least striving for the lighter side of things where possible.

[VanHallen]

Here's one of the Maltec's: https://www.maltec.org/mercedes/

Looks like it has solid axles, 35 in tires, and 134in/3400mm wheelbase and weighs in under 7000lbs. I don't know anything about how it's mounted which would be a nice datapoint as there are some similarities.

[VanHallen]

If you're really interested in torsion free systems and related concepts, I found these resources from Unicat to be extremely informative. I was pleasantly surprised in the video how they do a static test to measure the flex of the vehicle. It's also worth noting that Unicat integrates the subframe into the floor of the habitat / composite box which effectively lowers the center of gravity. Lots of good Q&A too, provided you have the time.

https://www.unicat.net/en/frame-assembly.php

https://www.youtube.com/watch?v=LCIoPuUmkb0

[VanHallen]

In the previous video, there are several insightful comments. If you can't watch all of it, as pertains to this discussion, at 1hr:02 Thomas discuss where most of the twisting occurs between the front and rear axles near the cab and at 1hr:08, he talks about why rubber pads should not be used for offroad purposes.

Now, in this much much much shorter video, you can see how the habitat box is mated to the chassis on the 3 / 4 point system and then off for some dynamic testing:

https://www.youtube.com/watch?v=Sa3MeqZQCHA

Certainly these vehicles are larger with heavier loads but designed for much of the same use and similar terrain I intend for this build. I suspect many of the same principles and considerations apply but on a slightly reduced scale.

[fjefman]

Originally Posted by VanHallen

Certainly these vehicles are larger with heavier loads but designed for much of the same use and similar terrain I intend for this build. I suspect many of the same principles and considerations apply but on a slightly reduced scale.

Cool references but this isn't just a "slightly reduced scale." Gravity effects an ant VERY differently than an elephant.

To continue with my animal references I think I've beat the dead horse enough on this "overthinking the flex issue" so I'll hush up for a while. Still enjoying the conversation though.

Jeff

[mk216v]

Originally Posted by VanHallen

mk216v, All good points and to be honest I don't the minimum requirements of an "RV" I think it's sink, bed, and few other things, but know it's attractive for financing and insuring, so it an upfitter can take a vehicle to that point it makes it easier for customers wanting to go that route.

As for ExpoVan, would love to what aspects of their conversion you liked most?

fjefman, Regarding one of my earlier posts regarding testing. As I think about it more, there should be a static or bench test if you will, ideally with the exact material. First, test the a 4x4 converted e350 using a ramp or fork lift without a subframe and attach a flat piece of foam or plywood or the actual product and then drive each wheel on to ramp or lift with a fork lift. The idea is to see if the flat board remains on plane or does it try to bend or buckle. Does the leading edge of the board, move independently of the cab during the flex? It could be the board is in plane but changes relative to the cap. Take vertical measurements to the the ground on four corners with each wheel lifted. Then repeat with the mounted subframe in question taking similar measurements and looking for relative movement of the leading edge to the back of the cab as this will determine whether the box should be hard mounted to the cab or to use some sort of boot mounting to allow for that movement. I'm sure actually doing this test would invite other questions and solution ideas.

After this static test, then doing the driving test (similar to my previous post) with the best solution identified during the static test.

Next, add the box without windows and doors, assuming the cutouts are there for those windows and door. Connect the pass through. Repeat the static test looking for cracks, buckling, delamination, mounting fatigue, etc in the panels, joins and cutouts. Then take it for the dynamic test and evaluate.

During the dynamic testing, looking for the amount sway and whether the box movement is abrupt or tempered. A good slow speed run on rutted, fireroad, and traversing undulating terrain would be a good start.

At this point adding the door windows and redo the static followed by the dynamic. In theory if the box with all the windows and doors survived with now issues in panels, joins, or cutouts, that would suggest the box was successfully isolated so it's safe to add the windows doors and interior build out.

I'm sure there is some sort of protocol that expedition vehicle builders using similar boxes and articulating chassis follow for this sort of thing. This may seem like over kill, but it's got to be safe on the road and last through thousands of miles of varied and sometimes harsh terrain in order to justify spending on this type of build, imo.

Bed and sink at minimum for an RV. And I agree on RV financing/insurance--saves a lot!

EV/MG 4WD; well for starters, a safety bonus are the factory 14.3" big brakes for no charge, since they use very late model front axles. Ease of install with no welding. Totally open source help with all of the part #s laid out, so you can find the best deals on parts yourself. MG is SUPER helpful with questions, even if you haven't bought anything from him yet/with those still learning.

Great stuff VanHallen, you've really put a lot of dedicated thought into this!

Originally Posted by VanHallen

I hope to drive one soon! There are two versions of the 7.3 v8 available for the e350. The performance is the one you described and there is an economy version with 300HP and 425lbs - torque. Both deliver their torque on the low end and are not that different than the 6.8 v10 in terms of the power specs. Both should be a little better than the v10 by virtue of the 6spd transmission and tow haul mode. So far far, I'm satisfied with the v10s grunt on the highway and mountain passes. If the 7.3 with 6spd can equal the grunt of the v10 with a little better gearing for offroad and a little better gas mileage I think it would be a winner in my book. Of course it has to prove to be reliable so I'd likely stay away from tunes that could affect that.

My hope with a composite panel build the whole thing comes in around 8500 or less. If that can happen then compared to many other Fullsize truck campers and High top Vans, it would end up with a very favorable power to weight characteristics which should also help with mpg/range, reliability, on road performance and off road capability. So many builds are going big and I'm just wanting to do something a little different.

Why move away from your simpler/reliable 6.8L V10/5R110? Not inexpensive to "upgrade" to the new 7.3L NA.

Would love to see your composite camper 4WD stay under 8500lbs; would be very very impressive!

Originally Posted by VanHallen

Here's one of the Maltec's: https://www.maltec.org/mercedes/

Looks like it has solid axles, 35 in tires, and 134in/3400mm wheelbase and weighs in under 7000lbs. I don't know anything about how it's mounted which would be a nice datapoint as there are some similarities.

Malte's cabins are carbon fiber, but I'd still be very surprised if they come in under 7000lbs--that has to be dry, not wet. My G500 O'erlandewagen was 6900lbs on 33s/Hutchinson's and everything added was aluminum to keep weight light. Fully loaded for a big excursion, it was 7400lbs with 2 people and gear. So I don't see how they could have a full camper where weight is under 7000lbs.

[VanHallen]

Originally Posted by mk216v

Bed and sink at minimum for an RV. And I agree on RV financing/insurance--saves a lot!

EV/MG 4WD; well for starters, a safety bonus are the factory 14.3" big brakes for no charge, since they use very late model front axles. Ease of install with no welding. Totally open source help with all of the part #s laid out, so you can find the best deals on parts yourself. MG is SUPER helpful with questions, even if you haven't bought anything from him yet/with those still learning.

Great stuff VanHallen, you've really put a lot of dedicated thought into this!



Why move away from your simpler/reliable 6.8L V10/5R110? Not inexpensive to "upgrade" to the new 7.3L NA.

Would love to see your composite camper 4WD stay under 8500lbs; would be very very impressive!



Malte's cabins are carbon fiber, but I'd still be very surprised if they come in under 7000lbs--that has to be dry, not wet. My G500 O'erlandewagen was 6900lbs on 33s/Hutchinson's and everything added was aluminum to keep weight light. Fully loaded for a big excursion, it was 7400lbs with 2 people and gear. So I don't see how they could have a full camper where weight is under 7000lbs.

mk216V, Great info and appreciate your contributions!!!

I'm loving the 2003 SMB v10 and have a few projects like adding a heater. It has been used almost exclusively on the West Coast, so this will help for where we live and travel the most.

We're only thinking of upgrading to the 7.3L v8 cutaway so we can add the composite panel box for a little better space utilization and insulation for 4 season usage and longer trips. I do like a lot of the characteristics of 7.3L v8 with some some added range, 6spd transmission, tow/haul mode) which should be great for mountain passes and offroad with it's gearing.

Our current SMB is going to be terrific in the interim + and at the same time, it's going to be fun to design & build from scratch on a newer platform for decades of future use (hopefully). Remodeling our current SMB is less attractive to us as that means there will be more down time when we can't use it and the layout / systems will still work great for future owners. This way we can also take our time to do the new build right without rushing things. Hope that makes sense!

[b. rock]

https://www.maltec.org/toyota/

The cruiser weights range from 5800-6800 lbs. That's what I referenced in my post. 5800 lbs for the 80 series camper is definitely surprising - but if you ditch the sheet metal past the cab, you're dropping quite a bit of weight.

I haven't watched the full vids yet, but it's worth noting that unimogs and vehicles of that size tend to design frame twist as part of the suspension travel. Pretty apparent in the last few seconds of the 2nd vid. Bit of a different philosophy compared to the E series. It'd be interesting to see some of the full size trucks with flat bed campers off road and see how much wiggling is going on there.

The success of people selling 6 figure campers with some amount of off road chops would definitely bode well for a RB sized E-350 4x4 composite camper of similar quality and finish.