Weight estimation - DIY Ram 3500 with Total Composites or Box Manufaktur

[MilesBFree]

View attachment 793024
I don't know if it is in your calculations, but if you are installing a flatbed, figure around 400-500 pounds removed for the factory 8' bed.

View attachment 793025
And if you are going to 37s, did you add in the weight increase for the 4 tires and rims?

Good question on the set of 37s.

On my track car, the wheels and tires are unsprung weight and the springs, shocks, and brakes were majorly upgraded so it is not a worry. Plus race tires and wheels are lighter than stock (even though larger in dimension), so it's kind of a non-factor.

For the overland rig build, those are still unsprung weight, so my thinking is that they won't contribute to payload. (I welcome your thoughts on this - I may very well be wrong.) I included the spare since it will definitely be payload and sprung weight.

They will definitely need to be added to GVW for purposes of braking at least.

On a related note, at least some of the upgraded suspension components (e.g., airbags in the rear if i add them) also are not considered sprung weight. Springs are definitely not. Control arms maybe, maybe not. Shocks, sorta?

 

[MilesBFree]

You don't need to run duals or super singles. The GVWR of my F450 is 14,000lbs. With 2 of the back wheels taken off the capacity of the 4 remaining wheel and tires is 15,880lbs

Thx. It's looking like they are also not needed on the build i am considering, since GVWR is 11,000 lbs and it looks like i will be under that.

But you do raise an excellent point - weight capacity of individual wheels and tires.

Assuming the 11,000 lbs is split 30/70 front and rear, the rear wheels will need to carry 3,850 each.

I was looking at either an AEV or Black Rhino wheel but think i will need to go with the AEV one since it will carry more weight (4,100 lbs each). The Black Rhino one I was looking at was like, 3,700 lbs max.

 

[MilesBFree]

the 30/70 split is a total SWAG based on a pure guess

 

[Alloy]

the 30/70 split is a total SWAG based on a pure guess

My F450 is 40/60

 

[MilesBFree]

That makes sense given from the factory the weight is more in the front with the engine there and a front diff in a 4x4. The percentages i found for factory config seemed to be roughly 65/35 front to rear. So adding the habitat on the back would add a lot of weight, but a decent percentage mostly on the rear

 

[MilesBFree]

Great inputs, @klahanie. I agree - the CoG is very likely the reason as you said. I originally was thinking of putting the fridge as far forward as possible, then decided to move it backward 24" since the batteries and electric gear may be heavier so put that toward the front. Also, moving the fridge a bit farther away from the bed will reduce the noise from that.

Given how early in the process I am and this is all on paper, I can move the components anywhere - just looking at payload and GVWR. And now CoG, thanks!

But hanging a 140 lb spare, plus let's say a 50 lb bracket, at the very tail end will have a noticeable effect on the CoG.

I need to find the CA dimension for the single cab with 8' bed; was looking for that late one night then forgot to come back to it. Obviously you get that dimension for the CA version of the truck, but even the shorter version of the chassis cab truck seems longer than the 8' bed version?

The wheelbase is 140", but i haven't been able to find the CA distance.

Some digging did turn up the following:

GAWR Front: 5,500 lb
GAWR Rear: 6,000 lb

Base Weight Front: 3,693 lb
Base Weight Rear: 2,624 lb

So the max load on the rear axle can be 6,000 - 2,624 = 3,376 lbs.

Comparing to your thought:

1) If your loaded habitat is 2,500# and it's mounted cog is 14" forward of the RA centreline and your wheelbase is 140" then the habitat weight distribution would be 10/90% or 250# FA/ 2,250# RA.

Looks like it is still good (obviously depending on it is actually built and the real-world CoG ends up.)

That's stock so not including weight removed from taking the bed off and weight added from putting the tray on.

If i can find the CA distance it would really help in looking at the CoG. Will post on the FB 2500/3500 group and see if a kind soul will measure.

 

[MilesBFree]

Update: I found that the shorter chassis cab version of the truck has the same wheelbase as the 8' bed version, and i know that the cab and front end is the same, so the CA measurement of 60" looks good to use.

 

[MilesBFree]

Also, the chassis cab version has a payload of 5,140 lbs. The 8' bed version is 4,600. The difference is 540 lbs. Not sure if all of that is the bed, or if other stuff is left off the back of the truck when the bed is deleted for the chassis cab version.

 

[renottse]

Some actuals for you… realize it’s different camper, however it’s 37’s and a Norweld on a ram.

Pre build and post build axle weights.



So 64% front 36% rear pre build.

And, 46% front 53% post build.

Post build had camper full of food, drinks, clothes. Truck had no people, 52 gallons of diesel, 20 gallons of water, recovery gear, spare tire behind the diff with jack, pull pal and box on the back.

I wanted the camper as far forward as I could so didn’t use the garage solution.

Which means solving the spare wheel problem… so…

If you’re going Bowen or Norweld, delete the bumper and get a Curt C15803, cut the frame attachments off at the cross bar and get something like this burned.



This will allow you to move the cross bar back the 3 or so inches you need to clear the tire. I added height to the above pieces so I cold lower the cross bar and carry a rear winch and still open my tool draw.

Brought a bulldog universal winch plate, clearanced it in center and welded it all together.



Coated in raptor…



Bolted in


So now you’re set for towing and you have a bumper of sorts. Not putting a winch on, just need to extend the brackets 3” (cardboard aided design for the win)

Last part of the puzzle is the winding mechanism to lift the wheel. You need to make a new hole about 1 3/4” rearward of the existing hole. Take the winding mechanism out and cut the tube that carries the wire ( some eye-ometry, a marker and a little thinking about chaffing will get you in the right spot) and mount in the new hole.

Now your 37” ( BFG’s are 36.5” new) is up and under (yep tight but I know it an’t moving) AND you can get that camper forward.

Side view, nothing really looks to untoward.

 

[mog]

1443.4mm or 56.8 inches.



If you visit 2023 Ram 2500/3500 HD Documents it will have the info you could hope for



to include such obscure things as Box Delete Fuel Fill, Box Removal Electrical Changes, in addition to; weights, frontal areas, electrical loads, amps per circuit, etc, etc.
Or you can select any of the Ram models from the top menu.

You should be able to determine your BEW (Basic Empty Weight) CoG from this, and work out your BOW (Basic Operating Weight) CoG with calculations (backed up by scale weights), as you progress.

 

[MilesBFree]

Some actuals for you… realize it’s different camper, however it’s 37’s and a Norweld on a ram.

Pre build and post build axle weights.

View attachment 793418

So 64% front 36% rear pre build.

And, 46% front 53% post build.

Post build had camper full of food, drinks, clothes. Truck had no people, 52 gallons of diesel, 20 gallons of water, recovery gear, spare tire behind the diff with jack, pull pal and box on the back.

I wanted the camper as far forward as I could so didn’t use the garage solution.

Which means solving the spare wheel problem… so…

If you’re going Bowen or Norweld, delete the bumper and get a Curt C15803, cut the frame attachments off at the cross bar and get something like this burned.

View attachment 793424

This will allow you to move the cross bar back the 3 or so inches you need to clear the tire. I added height to the above pieces so I cold lower the cross bar and carry a rear winch and still open my tool draw.

Brought a bulldog universal winch plate, clearanced it in center and welded it all together.

View attachment 793427

Coated in raptor…

View attachment 793426

Bolted in
View attachment 793428

So now you’re set for towing and you have a bumper of sorts. Not putting a winch on, just need to extend the brackets 3” (cardboard aided design for the win)

Last part of the puzzle is the winding mechanism to lift the wheel. You need to make a new hole about 1 3/4” rearward of the existing hole. Take the winding mechanism out and cut the tube that carries the wire ( some eye-ometry, a marker and a little thinking about chaffing will get you in the right spot) and mount in the new hole.

Now your 37” ( BFG’s are 36.5” new) is up and under (yep tight but I know it an’t moving) AND you can get that camper forward.

Side view, nothing really looks to untoward.

View attachment 793429

Wow, thank you! Tons of great ideas!

 

[MilesBFree]

View attachment 793436

1443.4mm or 56.8 inches.

View attachment 793433

If you visit 2023 Ram 2500/3500 HD Documents it will have the info you could hope for

View attachment 793434

to include such obscure things as Box Delete Fuel Fill, Box Removal Electrical Changes, in addition to; weights, frontal areas, electrical loads, amps per circuit, etc, etc.
Or you can select any of the Ram models from the top menu.

You should be able to determine your BEW (Basic Empty Weight) CoG from this, and work out your BOW (Basic Operating Weight) CoG with calculations (backed up by scale weights), as you progress.

View attachment 793439

Again, many thanks! exactly what I was looking for!

 

[Darwin]

It's going to be overweight, or if not, suffer from poor handling. This is purely speculation, so I am open to being wrong. The TC campers that are now 50mm all around will be lighter than the the ones built with the 83 mm roof and floor, so that could work in your favor going with 50 mm all around but once you add up everything in a 'real world' scenario I can see this thing being heavy, maybe not overweight but enough to make the handling suffer.

 

[andy_b]

I just finished building a custom Total Composites box in a outfitted similar to what you describe.

To answer your question:

I'm not gonna force this onto a chassis that won't handle it so ok with the answer that i should give up on the 3500 single axle and go to the duellie or even to a 4500 or 5500.

Give up on the 350/3500 chassis (even a dually or cab-chassis). No one builds a hard walled camper like what you describe to just take weekend trips. The weight of “necessary” components adds up fast. As other posters have described, a camper like this will come in around 11,500 - 12,000lbs total GVWR, on the low end. The camper, wet, will be around 3000lbs. A 550/5500 camper is not much more expensive in the grand scheme (since you have to procure it still) and will provide a tremendous increase in value (as a basis for your camper) overall. Don’t bother with the 450/4500 - same amount of work to build around, equivalent pricing, less weight capacity. I disagree with the marketing that an 8’ flatbed camper is suitable on a 350/3500 chassis.

No one is going to leave the suspension, wheels or tires alone on a truck like this alone. They may intend to leave it stock at the beginning but that never holds true for long. The costs of going super single and updating the suspension of a 550/5500 series truck, although substantial, are not necessarily something greater that you would not encounter on a 350/3500 series truck.

I would have Alcan, Deaver, Atlas, etc make you a custom spring pack for the camper once it is completed. The 550/5500 series trucks are just different enough to have issues with off-the-shelf shocks but I’m sure that you could find a good solution with some research and fab work. ADS in Tucson has made some friends of mine with 5500s great custom valved shocks. They are building a set for me, too. Kelderman and Liquid Spring, although neat, do not work IMHO in terms of value compared to custom leaf springs.

The one thing to consider with the off-the-shelf TC camper and a 550/5500 series truck is width. The 81” exterior width puts the camper body within the exterior of most pickup cabs (regardless of weight class). My camper is similarly dimensioned. It looks and works awesome without anything sticking out past the body. However, the wider track of a 550/5500 axle puts a few inches of rear wheel outside of the exterior of the camper body on either side. It isn’t the end of the world but important to keep in mind.

Regarding the indoor bathroom naysayers - they are wrong. We have a interior wet bath just inside the entry door so that the bathroom serves as a mudroom. It is amazing. In the winter, wet gear can dry out without being stolen and year-round the room allows exterior dirt to stay outside of the main living space. It is true that the solid walls intrude on interior space, but it isn’t as bad as you’d think. I am a big believer in having things do the thing they’re intended to do, well. I hate half-measures and a toilet below the dinette seat or in the kitchen is the literal definition of that, to me.

Speaking of toilets - we found that the lightest toilet option is a Wrappon. OK4WD used to sell just the sealing unit only which was a great “deal” in that you didn’t have to gut a system and waste money. IDK if they are still selling those but there is no water, no cassette, no compost, etc.

 

[MilesBFree]

We took a few days off to get our kid to college but are back now.

I agree that this isn't likely going to work. I thought of several more non-trivial items to add and it's looking closer to 11,500 - 12k lbs GVW and likely to go higher. So the 3500 platform is likely out for what we want to do.

And in terms of travel goals / journeys, we aren't looking at weekend trips but rather extended overlanding-type things, like out for a couple of months at a time (with short stints at more traditional campgrounds for laundry, resupply, etc. So the weight as used is likely to be higher.

The reasoning behind the 3500 was to get a truck with more comfort and safey options than the 500 offers (in a single cab), stay within some of the National Park road restrictions, 5-ton bridge limits (yeah, I know 11k is over 5 tons , easier maneuverability, 37s instead of super singles (I'm not getting any younger and wrangling 200lb-plus tires isn't terribly appealing), the MPT 81s* have a bad reputation for balancing, roundness, etc.

Just doesn't look do-able in a hard-sided box. Popup, could probabl;y make it work.

Going to step back for a little while and reconsider the 5500 or F550 option. But then it might snowball and add another 2' to the box since the floor plan i came up with was a bit cramped. But at that point you are basically building a more robust and much more capable C-class RV that is also a lot more expensive. The option to buy a used C-class even cheaper and tow our old Land-Rover behind (or trade our other car for a jeep or new Land Cruiser) starts to come back into play. It's not apples to apples but if we change direction i would want to consider all alternatives.

* has anyone used the Goodyear G275 instead of the MPT81? I haven't seen a whole lot of info on it other than some basic specs and that it wears a lot longer.