Total Composites flatbed build

[andy_b]

Will the roof of the alcove be the same height as the roof of the camper's main body, or will they be at different heights? (See @IdaSHO 's camper photo in the quote below.) If the alcove and main body will have the same roof height, that may result in an camper's main body interior height greater than you are currently thinking. Keep in mind that having enough height in the sleeping alcove can be quite useful.

Being able to wear boots and a hat inside without scraping the ceiling might be useful to you.

You don't have to match the camper's main body to the flatbed, but I suggest you have good reasons for exceeding the flatbed dimensions, and keep in mind that you might want a good bumper protecting the rear of your camper.

The roofline is flat. We aren't cowpolks so I don't think we'll need boots or hat clearance, lol. We want to match the dimensions of the flatbed to minimize overhangs, etc. I intend to use the stake pockets on the side as rub rails.

Anyhow, since this is the final dimension check off, I was looking at everything more closely and realized that the vertical height in the cabover is only 29". I guess I'm going to need to have the headache rack trimmed to either be flush with the roofline or just remove the upper portion altogether. Our Airtop has around 37" of clearance and we could probably tolerate a little closer since we could stand up elsewhere.

Below are some of the dimensions from the builder (in mm, of course):

 

[1000arms]

Will the roof of the alcove be the same height as the roof of the camper's main body, or will they be at different heights? (See @IdaSHO 's camper photo in the quote below.) If the alcove and main body will have the same roof height, that may result in an camper's main body interior height greater than you are currently thinking. Keep in mind that having enough height in the sleeping alcove can be quite useful.

Being able to wear boots and a hat inside without scraping the ceiling might be useful to you.

You don't have to match the camper's main body to the flatbed, but I suggest you have good reasons for exceeding the flatbed dimensions, and keep in mind that you might want a good bumper protecting the rear of your camper.

The roofline is flat. We aren't cowpolks so I don't think we'll need boots or hat clearance, lol. We want to match the dimensions of the flatbed to minimize overhangs, etc. I intend to use the stake pockets on the side as rub rails.

Anyhow, since this is the final dimension check off, I was looking at everything more closely and realized that the vertical height in the cabover is only 29". I guess I'm going to need to have the headache rack trimmed to either be flush with the roofline or just remove the upper portion altogether. Our Airtop has around 37" of clearance and we could probably tolerate a little closer since we could stand up elsewhere.

Below are some of the dimensions from the builder (in mm, of course):
View attachment 617517
View attachment 617518

29" is a short bedroom, especially if that includes a thick mattress. Are you sure you don't want some additional room, or, do you normally sleep in a coffin? ...

Well, I was thinking hiking boots and a boonie hat, but, either way, you might have missed my point about having a bit of headroom.

Oh, did you mean cowpokes, cow-folks, or ...?

 

[rruff]

Anyhow, since this is the final dimension check off, I was looking at everything more closely and realized that the vertical height in the cabover is only 29".

Mine is 35" which I think is minimal; anything shorter would be too cramped for anything but sleeping (ya ). It will still be an adjustment. Interior height is 76".

How much tire clearance do you a have to your flatbed? What is the gap between your cabover and the cab?

 

[Chorky]

Following. I'd like to see where the OP takes this as I am considering something similar. I'm also curious to see this camper your building!

Liability alone is enough to keep such drawings under wraps, IMO.

I do understand that most have trouble with the last two.... design and fabrication.
That's proof positive in a so many of the sketchy builds.

So proceed with caution.

Personally, without having the engineering background, I overbuild, but with my eye on weights, constantly.
It has proven effective.

I think this is one thing that many don't realize and you pointed it out well. There are the very select few with millions who can buy or build anything. But most of us are severely limited and just try to do the best with what we have. Many have no or few tools, no place to do fabwork, and not enough cash to pay for all said tools, parts, equipement, etc..., and on top of that there are few companies willing to do much custom work, for a variety of different reasons. The OP certainly has room for improvement I think - and I think they understand some of the discussions/thoughts, but at the same time, I think its not a very reasonable expectation that everyone can just do everything like others have suggested when there are time/space/money/tool/knowledge limitations - knowledge being a big one since as many mentioned few are willing to share their ideas due to liabilities and such. It seems to me this is on the right track for what the OP want's to accomplish though, maybe with a few changes over time. Hopefully it lasts as long as they want to use it.

 

[andy_b]

Following. I'd like to see where the OP takes this as I am considering something similar. I'm also curious to see this camper your building!




I think this is one thing that many don't realize and you pointed it out well. There are the very select few with millions who can buy or build anything. But most of us are severely limited and just try to do the best with what we have. Many have no or few tools, no place to do fabwork, and not enough cash to pay for all said tools, parts, equipement, etc..., and on top of that there are few companies willing to do much custom work, for a variety of different reasons. The OP certainly has room for improvement I think - and I think they understand some of the discussions/thoughts, but at the same time, I think its not a very reasonable expectation that everyone can just do everything like others have suggested when there are time/space/money/tool/knowledge limitations - knowledge being a big one since as many mentioned few are willing to share their ideas due to liabilities and such. It seems to me this is on the right track for what the OP want's to accomplish though, maybe with a few changes over time. Hopefully it lasts as long as they want to use it.

What areas have room for improvement? Any suggestions?

 

[andy_b]

29" is a short bedroom, especially if that includes a thick mattress. Are you sure you don't want some additional room, or, do you normally sleep in a coffin? ...

Well, I was thinking hiking boots and a boonie hat, but, either way, you might have missed my point about having a bit of headroom.

Oh, did you mean cowpokes, cow-folks, or ...?

I wasn’t clear but I mentioned the cabover height because I need to increase it. 29” is way too short.

if you read the rest of the post, the interior height is 6’4”and I am 5’6”. That is 8” of free air above me. I need to lower the height of the front wall to increase the height in the cabover.

Cowpoke was what I meant - Stupid fat fingers...

 

[Chorky]

What areas have room for improvement? Any suggestions?

Well I think during the discussion of your bed mounting there are a variety of valid points being made. Even though the springs you are using may be designed to handle the full load of the bed (a water tank), it still might be a good idea to have stabilizing plates. Or possibly even do a subframe of sorts (since the bed is already built) that sits on the truck frame to make sure weight is distributed evenly from the bed on the frame (I think you mentioned using wood?). But at the end of the day like Kenny said this is uncharted territory for a lot of people so it's hard to say what will actually work and not. Also, with the frames of the OBS being so flexible, I would be a little curious to see how strong the mounting points for the springs to the bed are and if the spring load is going to be too strong to allow for the bed to move independently. I also have read talk about spring mounts not really being designed to fully allow for bed articulation, but rather allow for some bed movement, but still causes flex in the bed to some degree - so maybe adding some sort of soft mounting for the camper to the bed might also be something worth looking into? I know I was planning to work with AlumLine on a bed, but like others say they seemed reluctant to do any design differences to specifically allow for spring mounts, requiring me to either find a local shop willing to make modifications that are sound, or seek other options.

 

[rruff]

Also, with the frames of the OBS being so flexible, I would be a little curious to see how strong the mounting points for the springs to the bed are and if the spring load is going to be too strong to allow for the bed to move independently. I also have read talk about spring mounts not really being designed to fully allow for bed articulation, but rather allow for some bed movement.

I suspect that also. Even a very well designed spring mount will impart some torque to the bed and box.

andy-b, at your earliest opportunity I think it would he good to see how your setup responds to full articulation. If you need to redesign the mounting, you may wish to raise the floor of the flatbed a few inches also, which will give you more room in the cabover (with rack trimming).

 

[andy_b]

I suspect that also. Even a very well designed spring mount will impart some torque to the bed and box.

andy-b, at your earliest opportunity I think it would he good to see how your setup responds to full articulation. If you need to redesign the mounting, you may wish to raise the floor of the flatbed a few inches also, which will give you more room in the cabover (with rack trimming).

I've never heard this until this discussion thread, and I can't see why that necessarily would be. Torque would be transmitted to the bed whenever the mounts limit movement. A pivot or springs both by design do that less than another type of mount.

I do agree that an articulation test of some kind is in order. We took that into account when installing it and the installers felt pretty confident that they left enough clearance - I hope they did, lol. That is my least favorite option though as it raises the overall height again.

 

[rruff]

Torque would be transmitted to the bed whenever the mounts limit movement. A pivot or springs both by design do that less than another type of mount.

The frame can only twist relative to the flatbed by compressing the springs. If the springs are very stiff, then the flatbed and camper box will twist too. The camper is the stiffest component in this scenario so it will carry most of the load; it will keep the flatbed and frame from twisting, and you don't want that.

It would probably not be hard to switch to a 3 point style mount if you determine it's warranted.

 

[andy_b]

The frame can only twist relative to the flatbed by compressing the springs. If the springs are very stiff, then the flatbed and camper box will twist too. The camper is the stiffest component in this scenario so it will carry most of the load; it will keep the flatbed and frame from twisting, and you don't want that.

It would probably not be hard to switch to a 3 point style mount if you determine it's warranted.

I see your point and this brings to mind the main limitation of the spring mounts which is excess sway, as previously mentioned. Assuming normal mechanics (big assumption), the spring on the opposite side would extend an equivalent amount with almost no resistance. That should mitigate the twisting, but allow a lot of sway. By keeping the weight (and inertia) of the camper box down, I am hoping to limit that effect.

I could certainly switch to the 3-point style, and I'm not against doing so if needed, but that brings us back to the issues behind why I didn't do that to begin with.

Good conversations.

 

[DirtWhiskey]

I wouldn't bother with the 3 point mount. Frankly not sure why a complete re engineering of your mounting system is even in discussion. Follow your path. Be comforted that it has been shown to work an order of magnitude more times than fancy 3 point systems. No need to reinvent the wheel and some sort of tension bounding will be GREAT when in off camber situations. Just check the spring tension (I suspect they are too strong but really have no idea) and plug the gaps with wood to spread the stresses along the rail.. If you have more questions use fast guns for the camper mounting which would give you "backup" springs if you're really that worried about torque. Also a hell of a lot easier to mount and unmount vs aligning four to six tiny bolt holes.

I am not sure a completely independent mount is needed or even smart on these trucks. I have even seen way too much sway, hence Idasho's super awesome shock idea (which I will be "borrowing" thanks man!). And remember with a 3 point, you are moving stresses around on the frame in unpredictable ways that require a lot of thought. With a spring mount, the idea is you always have all of the load along an entire frame rail. Stay the course. We tend to WAY overthink things on this forum.

 

[Woodstockz]

Interesting build. Thanks for the details.
How will you attach the camper box to the flatbed?

 

[1000arms]

29" is a short bedroom, especially if that includes a thick mattress. Are you sure you don't want some additional room, or, do you normally sleep in a coffin? ...

Well, I was thinking hiking boots and a boonie hat, but, either way, you might have missed my point about having a bit of headroom.

Oh, did you mean cowpokes, cow-folks, or ...?

I wasn’t clear but I mentioned the cabover height because I need to increase it. 29” is way too short.

if you read the rest of the post, the interior height is 6’4”and I am 5’6”. That is 8” of free air above me. I need to lower the height of the front wall to increase the height in the cabover.

Cowpoke was what I meant - Stupid fat fingers...

It's time to finalize dimensions and I'd love to get some input from other camper owners. ... I want the camper to be a low as practical. ... How close can the ceiling get to your head before it feels claustrophobic or unpleasant? ...

I did read through your posts. I mentioned standing up wearing boots and hat to answer your question regarding camper ceiling, my head, and claustrophobia/unpleasantness.

 

[rruff]

I wouldn't bother with the 3 point mount. Frankly not sure why a complete re engineering of your mounting system is even in discussion. Follow your path. Be comforted that it has been shown to work an order of magnitude more times than fancy 3 point systems.

It wasn't engineered to begin with, though... and does not resemble any spring mounted system I've seen. And it appears that it would transfer a lot of twisting force to both the flatbed and the box... which is the reason why it exists at all.

These trucks have a flexible frame for a reason. It allows for a high payload (stiff springs) and keeping the wheels on the ground. Newer trucks are going to a fully boxed (stiff) frame and worrying less about keeping all wheels on the ground. The stiff frame certainly simplifies camper mounting (no need to make a torsion-free subframe) and should improve on-road performance, but will have different issues offroad.

It's complicated because there are major tradeoffs at stake even with very well sorted designs.

I could certainly switch to the 3-point style, and I'm not against doing so if needed, but that brings us back to the issues behind why I didn't do that to begin with.

What were the reasons? Sorry if you mentioned it, I looked and didn't see anything.

It appears that your springs are very lightly loaded as it sits? As configured they will only pull down on the flatbed as it tries to move upward (relative to the frame) from twisting. When they bottom out, then you will get upward support at that point. Otherwise upward support is only where it rests near the midpoint of the frame. But that issue can be fixed easily by providing support at the corners as well.

The other obvious potential issue is the spring rate. I looked up the springs you are using and they say "3000 psi"... but that isn't a spring rating. If what they really mean is 3,000 lb/in then that means it will impart 3,000 lbs of force with a mere 1" of movement. I'm pretty certain that is *way* too stiff for your application. But you should be able to buy weaker springs easily enough. Plenty of options here: https://www.mcmaster.com/compression-springs/compression-springs-7/