Design help for foamie

[StaceyK36]

So, I’ve been lurking for a long time finally convinced my husband to buy a utility trailer kit and now we’re starting this ‘hair brained scheme’ as my family puts it!

We’re building a folding foamie with EMT tubes swinging hinges made for the tubing and plastic living hinges on the outside to make the hinge waterproof. The plan is to use a hot knife to burn a channel in the edge of the foam for the tubing to sit in (1.5 in foam. 1 1/16th tube).



It would fold like this and each panel would be pmf. In my scale model I’m having trouble figuring out the measurements of the triangle support.


The basic fold works and I picked this design so that a bunk bed can be set up in the fold out. It folds down small which works for an inexperienced tower and the foam keeps it light for a Honda hrv that’s technically not rated for towing but can tow around 1100 lbs. The goal is to keep it 700 lbs or less.

Any thoughts would be much appreciated!


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[RJ Howell]

There is a whole bunch of, whole bunch of here..

Can it be done, I say ya, but... You need to break down the design to practical parts and understand how it's working/gong together. I get the design (complexity) of the lift and stay of this, yet I wonder if all that is worth the saved gas mileage of a short trailer vs. a full would be... Conversational build, now that's worth a million, but usability?

Show me some more, I'm always game to something different and interesting. I do love a good foam build!

[Pmullen503]

This would be very cool but it gets even more complex once you account for the thickness of the foam.

[StaceyK36]

I think that’s part of my issue. The trailer will be 6 x 9. The base will be 72 in wide with the foam it’ll be 75 in and 111 in long. The front top and bottom folding panels will be 24 in high. The roof will be EMT and foam, and some ply just unsure if I need it? Will the interior be loud if it rains with PMF? My thought was if we needed to carry anything on top the wood would help support it. At this point that’s not the plan but we all know how things change!

The roof as far as I can figure holds the top row of folding pieces so it has to be about 5 or 6 in deep…That’s debatable at this point though. The real stickler is how to decide how big the fold out panels should be and what size the support triangles are that seem to provide the entire structure with stability at least in the model size….

The design was picked because we’re inexperienced towers and our vehicle is only 63 inches tall. I don’t want to tow something that’s looming above us and we’d really like to be able to stand up in it. Thus we’d have to have some sort of pop top, and yes the other design option is similar to the compact 3. We liked the layout of this and the fact that it’s so different but we’re not builders….


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[StaceyK36]

Also, if I used 10 oz duck canvas would this add a lot to width? I’m a little stumped on how to figure out if I’ll making my moving pieces too tight to move….


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[pchast]

I never heard the rain in mine.
I don't remember any bad storms either.

[Pmullen503]

Plan on canvas adding at least 1/8", more if you have overlaps along edges and corners.

I like the sound of rain on mine.

[StaceyK36]

My estimation at this point is that the folding panels should be 4.25 feet by 75 in but the interior support triangles are what I’m struggling with…..


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[pchast]

Have you attempted to make a model of your concept?
I think you should be able to work out your concerns by
doing so.

[WizardOfOdds]

Very interesting, but rather complex. From what I see, the triangle panels could be equilateral (all sides the same length) which makes the vertical height of the trapezoids 86.6% the slope height of the end panels. Using 45 degree right triangles produce vertical ends, other options are also available.

It is not clear to me how you intend to hinge the panels when the EMT is embedded into the foam. And how do you plan to anchor & seal the plastic living hinges to the panels? It seems like you will end up with an EMT tube on both sides of the hinged joints - could be quite strong but perhaps not light. Can you post a picture of the EMT hinge you plan to use?

I had many of the same aims (low tow height, high open ceiling, 700 lb max) for my 4 cylinder tow project (Tip Top Tear Drop link below). Those are difficult objectives for a first build, especially the weight. And yes, I ended up using EMT in the roof and other places.

For what it's worth, I suggest:

1- Yes, finish your model, it will help a LOT. I would buy some foam board from the local dollar store and keep the first model simple, maybe duct tape for hinges. But don't overlook the play you get from duct tape. Pay particular attention to how panels stack when folded, the foam board should be adequate to reveal folding issues. It is not easy to get real panels to fold flat without creating stress points at joints. For example, consider the hinge between the triangle and trapezoid panels: When opened, the panels align into a vertical plane, but rotates 180 degreses to a horizontal stack when closed. And the end panel needs to overlap them without stressing the top-to-end panel joint.

2- Add up the weights of the major components. One inch EMT is about 2/3 lb per linear foot. That can add up pretty fast! What does your trailer frame weigh? etc.

3- Don't minimize the problem of opening the closed trailer, lift mechanisms are a real challenge.

4- Look over similar designs posted in the Non Traditional section, here is just one similar folding roof:

https://www.tnttt.com/viewtopic.php?f=5&t=64495&start=90#p1230935

Good luck, have fun, and keep us posted.

[StaceyK36]

This is one of the hinges I’ve found.

https://shop.flexpipeinc.com/us_en/ap-h ... ge-bracket



Then this one…..

https://shop.flexpipeinc.com/us_en/hj-2 ... -hinge-set




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[WizardOfOdds]

Yeah, I thought you where thinking of using the 2nd hinge you show. I don't see a need for the slider for your plan.

I considered the 2nd type hinge long ago with the same conduit & foam idea you mentioned. But I wanted to get the same folding characteristics as with wood panels and door hinges, and these hinges did not directly accommodate the placing the rotation axis where I wanted it....

Yes, I could align the panels in a common plane for the opened position (with the panels butting end-to-end but with a gap), but then they didn't rotate far enough to stack properly. If I juggled things a bit I could get them to stack better, but when rotated end-to-end they were in staggered parallel planes. However, with careful attention, maybe your plan can live with it.

Maybe these snap on hinges would have given me all I wanted,
(image at https://i.ebayimg.com/images/g/zVUAAOSw ... s-l300.jpg)

but they are expensive (because they are aluminum?).

Another option was a hinge like this (pic ala creform.com)

which looks like something I might be able to make from from easy to get parts.

By the way, I plan to edit the blurb about the triangle panels in my previous post to make it clear:
equilateral triangles are one easy solution, but there are others. I can add more later if there is any interest.

[StaceyK36]

The slider hinge also rotates in an open and closed movement according to the blurb on the internet. I’m working on my scale model to see if the folding works then I thought I’d get the Emt and hinges to see what hinges work. The living plastic hinge would cover the gap I’m thinking….being glued and the maybe screwed into the pipe. Flexpipeinc.com has some clips that cover the piping enabling you to screw a panel to it….

What other ideas did you have for the triangles?


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[StaceyK36]

The 5x8 trailer kit says it’s about 250 lbs. Fingers crossed once put together it’s around that!


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[WizardOfOdds]

“ I’m working on my scale model to see if the folding works ”

Yes, keep working that model. Post some pictures of it.

“The 5x8 trailer kit says it’s about 250 lbs.”

Are you using the Northern Tool Steel base?

“What other ideas did you have for the triangles?”

Well 45-45-90 and 60-60-60 degree triangles are special cases. The rt triangles give you vertical ends, the equilateral give you the 120 degree apex ends. So I did some math for the general case, but only for a "paper fold", not accounting for thick panels.

The build I indirectly linked above has been updated since my post in the Non-Traditional thread. Here is a direct link

https://www.casa-trotter.com/phpBB3/vie ... =12&t=7838

It is a 3 page blog, so view all 3. You can use a translate to English, but the real value is in the many pictures. Study them, it features the same folding scheme, except he uses right triangles and only builds the lower half.




He uses flat panels with an insulator core covered on both sides with aluminum. I fear trying to use EMT/foam is too difficult.: How will you join the EMT at the panel corners? I don’t want to discourage anyone -- building a trailer has its own built-in ways of doing that -- but this is a very complex build, even aside from EMT/foam problems. I like to classify folding designs by the number of structural hinged and open edges that must be joined during opening. Doors & windows do not count. For example, an A-frame has two end hinges, two side hinges and one open seam (at the peak). This trailer has something like 26 hinged and 2 open joints. (Should this become a popular build, I want to have stock in the hinge makers!) Throw in the need for a lift mechanism, and well, it’s just a lot of risk.