Total Composites flatbed build

[andy_b]

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

Six tiny bolts as @DirtWhiskey said

 

[andy_b]

It wasn't engineered to begin with, though... and does not resemble any spring mounted system I've seen...
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/

As I (and @DirtWhiskey) have mentioned, this is similar to water trucks used offroad. Definitely not an apples-to-apples comparison at all, but I'm not creating a whole new species.

Reasons I chose to avoid a 3-point include:

• Loss of truck as a truck
• Maintenance - the truck has >200k and I anticipate a new motor. Having everything be removable seemed easier to do than a subframe that makes removal a distant afterthought.
• Cost: ~$13k for an aluminum ITB subframe vs $5k for the one I have
• weight and complexity (unless it is made of aluminum, then cost again)
• outside of ITB, no manufacturer of these on-off campers have a true engineering department so similar cost to ITB in my experience but little value added
  • One exception is the current Canadian/US border closure which is expected to stay in effect for the foreseeable future. That added a layer of hassle that made ITB less appealing
• Philosophically, I just don't see the point of going to the cost and effort. I may be wrong and will be back to mention it if so. I find it hard to believe that I'm the only one that doesn't want to turn their truck into a one trick pony when a flatbed dynamically mounted will most likely provide 90% of the benefits at 30% of the cost of a dedicated subframe.

Agreed on the "upward support" issues you mentioned. While looking for an engineer, I remembered that a friend does work in a local lab in materials. He does the stress analysis for their projects. He modeled my chassis-flatbed interface and found similar concerns to those others have mentioned and thought that adding additional vertical support would help. Otherwise, he didn't think that the design had any major drawbacks.

Aware of the spring rate issue and can easily find replacements, as you have also found.

 

[rruff]

Reasons I chose to avoid a 3-point include...

I was think of using the same flatbed you have, and it's not complicated. Instead of the front spring mounts you have hard mounts to the frame, and in the back you'll need some crossmembers (spanning the frame rails) with a pivot in the center.

But hopefully your spring mounts will work well with some modifications.

 

[andy_b]

I was think of using the same flatbed you have, and it's not complicated. Instead of the front spring mounts you have hard mounts to the frame, and in the back you'll need some crossmembers (spanning the frame rails) with a pivot in the center.

But hopefully your spring mounts will work well with some modifications.

That seems like a decent approach. What do you do for the rearmost of the flatbed-to-frame connection?

 

[rruff]

That seems like a decent approach. What do you do for the rearmost of the flatbed-to-frame connection?

My truck has two bed mounts on each side behind the rear wheels. I'll have two crossmembers bolted to these (aluminum tube, probably 3" with 1/4 walls), each with a poly cab mount in the center that bolts to the camper. No subframe; making the floor of the camper strong enough for the load. Most of the camper is hand-laid fiberglass over PVC foam, but I think the floor will be carbon (much stiffer than fiberglass) with reinforcements at the attachment points. That's the current plan anyway.

 

[Woodstockz]

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

Also, approximately how much does the Total Composites box weigh?

Thanks.

 

[andy_b]

Also, approximately how much does the Total Composites box weigh?

Thanks.

Honestly, no idea. A similar build was around 1900lbs, but that included a steel, non-articulating subframe with a giant commercial real door. Hopefully mine will be lighter. ?

 

[rruff]

Honestly, no idea. A similar build was around 1900lbs, but that included a steel, non-articulating subframe with a giant commercial real door. Hopefully mine will be lighter. ?

This guy just weighed his and he's getting ~2,000 lb for the box: https://expeditionportal.com/forum/...mper-build-thread.213614/page-38#post-2845126

Doesn't seem right... I expected it to weigh half that. Mine (10' long floor with a cabover) is not wimpy at all and should be <1,000 lb with frame mounting hardware. The walls and roof are ~1.5 lb/sq ft x 340 sq ft, and the floor/base is ~2.5 lb/sq ft x 70 sq ft. That's 685 lb total, leaving 300 lb for reinforcements.

 

[IdaSHO]

Yeah that's way too heavy.

Even my OMGITSMADEOUTWOOD!!!! shell weighed in at less than 1000lbs

Fully dressed, dry, I'm at 2200

 

[Victorian]

The weight seams correct. The steel bars in the rear wall and front wall probably added several hundred lb. The arctic tern entry door is around 50lb ... the support braces should be somewhere around 35lb... you ad this all together and the numbers start creeping up on you. We are having thanksgiving today... will check my files tomorrow when I’m back in the office to see what our engineers estimated originally.

 

[rruff]

Even my OMGITSMADEOUTWOOD!!!! shell weighed in at less than 1000lbs

Wood is good! I made one 20 years ago that was similar to yours only with 2.7mm Luan skins, 3/4" core, no steel supports, and a fairly thick layer of fiberglass (1.5oz mat?) on the outside. Floor was 5mm Luan and 1.5" core and bolted to the frame. It seemed plenty solid and had no issues. It isn't a bad way to go at all, just need to be careful with penetrations into the wood from outside.

... will check my files tomorrow when I’m back in the office to see what our engineers estimated originally.

Thanks! I remember seeing some of your panel samples on a scale and they were not heavy. I'm curious to see how the weight breaks down.

 

[Victorian]

Here are our basic weights. Please keep in mind that each order we process is slightly different and therefore these number can vary! By adding internal structure to mount tires, awnings etc you need to calculate ~3lb per sqft extra. To be fair, we have these mounting points in the rear wall as a standard. If the customer is very keen in saving weight, we can certainly delete them.
Overall you can't built lighter, faster or more thermal efficient than with our system.

All 12”X12” / 300mmX300mm

- 83mm/ 3.23” Floor panel including internal Fiberglass tube/Steel structure at 2’ /610mm spacing 4.12kg/9.08LB

- 83mm/ 3.23” Roof including wire Chanel 0.93kg/1.9LB

- 83mm/ 3.23” Rear wall including internal structure 2.35kg/5.18LB

- 50mm/2” Side wall 0.68kg/1.49LB Add internal structure for Awning mount ect. Ad 2.35kg/ 4.4lb per ft/300mm

Fiberglass poltrusions ~ 0.8kg/ 1.76LB per ft/300mm

Kommerling 600ml sausage type adhesive 0.89kg/1.9LB (on average you need between 24 and 36 tubes)

 

[DirtWhiskey]

This guy just weighed his and he's getting ~2,000 lb for the box: https://expeditionportal.com/forum/...mper-build-thread.213614/page-38#post-2845126

Doesn't seem right... I expected it to weigh half that. Mine (10' long floor with a cabover) is not wimpy at all and should be <1,000 lb with frame mounting hardware. The walls and roof are ~1.5 lb/sq ft x 340 sq ft, and the floor/base is ~2.5 lb/sq ft x 70 sq ft. That's 685 lb total, leaving 300 lb for reinforcements.

Hey RRuff will you have a build thread? Just learning the the magic of hand laid glass. Very interested.

 

[rruff]

Hey RRuff will you have a build thread? Just learning the the magic of hand laid glass. Very interested.

Ya, I probably will...

Nothing magic about it, but I like that you have more freedom with shapes. It would be a *lot* of work to make a nice smooth finish like you get with TC panels. If you are ok with it being a bit lumpy and rough with visible seams (like mine!), then it's not bad. The upside is that it will be facited and rounded and hopefully more aero.

 

[socceronly]

A composite camper is very stiff. Any vehicle flex that gets passed through to the camper can cause it to crack. Spring mounting the camper, either through a subframe or this method here, allows the camper to move independently of the chassis, hopefully improving its longevity.

Curious. When they say a bed is torsion free, what does exactly mean?

If have a flatbed on an F350 say, and building a camper on that, is it possible the bed itself is fixing this torsion problem?

Forgive me, just learning this stuff.

Thanks
JM