Two part TTT - raised roof?

[Thunderknight]

Okay...so I am thinking about how to get my TTT tall enough to stand in without being unstable to tow. Chatting with my coworker today, here is what we were thinking:
(my current frame is HF 4x8, already floored, awaiting the rest of the design

A box, mounted to the floor, consisting of 4 walls and no roof. Perhaps 3 feet tall.
A slightly larger box, 4 walls and a roof but no floor, perhaps also 3 feet tall. This will go over the smaller bottom box. This upper box cover the lower box during towing. During use, this upper box will be raised up to a position where the bottom of the walls are almost level with the top of the lower section walls. The gap will be sealed with a rubber gasket.

My biggest conceptual problem right now is how to raise the lower part. I am thinking of some kind of jack or geared track on the outside of the smaller box that would act to raise the larger box.

Probably the closest analogy would be a regular pop-up camper, but with hard sides.

Being only ~3 feet tall, it should easily resist tipping during towing. But then when I arrive, I can crank/jack it up and stand right up in it. 6 feet tall on a 4x8 frame seems like it would tip too readily...unless I load the bottom heavily to keep the cg down.

My other idea (this one sounds even wierder) is to raise the upper part using an external lift (like an a-frame with a pully) and then lock it in to place when it is raised. The external lift could then be stowed until it was time to take the trailer down.

Any thoughts?

[dhazard]

Check this out…

http://purplesagetradingpost.com/sumner ... index.html

[bdosborn]

How about arm power to raise the pop-up portion? That's how George raises his pop-top:



http://home.earthlink.net/~g.teague/index.html

Bruce

[reiltear]

http://www.tnttt.com/viewtopic.php?t=17093&highlight=vardo

http://www.tnttt.com/viewtopic.php?t=3740&highlight=

[Thunderknight]

I saw both of those when I was searching around.

We were figuring that by having the top section be the slightly larger section that slips over the smaller lower section, it would eliminate any water issues. It allows means the full square footage of the trailer benefits from the raised roof.

I figured that I would need some kind of mechical assist to raise the top because of the weight. The winch idea looks interesting (actually I have one like that laying around). Perhaps if I mount that on the tounge, then mount a "mast" in front of the box, taller than the raised box, with a pully, and use that to crank the top up.

I don't think the basic construction will be complicated (two boxes), but I am struggling with the lift mechanism.

Edit: Reiltear: Thanks for those links. You were posting when I was typing. I had not seen those in my search earlier.

[bobhenry]

http://www.llund.com/pne_cyl.htm
Air power to lift ,once it's up block or pin it into place, Using a small compressor you could control the rate of assent and decent by controling the air flow. Gang all 4 lift tubes together and it will raise level and without cocking or binding.

[angib]

I'm increasingly coming to the conclusion that you've got the right idea about how to make a simple, leak-proof pop-up.

Following the winch idea, you don't need to lift from above - you can lift from a sheave (fixed pulley) on the top of the lower side walls like this:



The tricky bit is finding a long enough place to put the links that join the four cables into two and then into one - you really want to have turnbuckles (is that a US term as well?) so you can adjust the length of each cable.

But the other plan is just to make it light enough that you can lift it by hand - though maybe you want to have some sort of latch that holds it up on the way - than you could walk to one end, lift a foot, walk to the other end, lift a foot there, walk back to the first end......

Another plan is that you only really need standing up headroom in one place. For example, you don't need it over a dinette where you can't stand up. So consider making the upper box just a bit bigger and hinging it at one end. Then all the lifting is at one end and you can add gas struts to make it easier. What you get is really Mike's Winter Warrior but wihtout the hinge halfway along the roof.

Here's a design I did on these lines:





The door size is a bit awkward (and would be very difficult to enlarge) but that's a small price to pay for simplicity.

Andrew

[jeep_bluetj]

Lift idea #1:

If you look at my trailer ( <=== there in my avatar) those are rodless pnumatic cylinders. I stick air in em and it goes up. Takes about 20 seconds to put up. I also have 3 gallons of air for jeep tires, air mattresses, and to pump water with.

I got em for free, but with your lift profile you could use standard pnumatic rams. (Cheap surplus). I needed about 48" of travel, not somethng you'd find with a standard cylinder. And the rodless ones are just kinda cool anyway - the piston inside the cylinder is connected to the car outside the cylinder with a big horkin magnet.

Lift Idea #2:

Andrew's solution is simple and pretty easy. It's very similar to how commercial pop-up tent trailers work (except for the really complex telescoping part).

Lift Idea #3:

4 Airsprings and muscles. Get in, and push up. The airsprings will assist. To go down, pull down. Easy/fast/simple, and not too expensive if you find a good source of the airsprings.


Lift Idea #4:

Jackscrews. Use some 3/8 all thread inside some PVC and conduit. Drive with a chain,belt, or individual electric motors. This is actually the idea I've been kicking around for awhile. It's complex though. With a lightweight top, standard UNC allthread will work OK. I've tested my prototype to 150lbs per screw, multiple extentions and retractions without galling the threads. It really should be acme or square thread, but hey, gotta save $$$ somewhere.

Lift Idea #5:

Use a single long jackscrew down the center under the trailer, and hook lift cables to it. (This is EXACTLY how a coleman pop-up works). You'd need to use acme thread for this. (An old garage door opener track would be superb)

[jagular7]

You should look at Alaskan Campers. They have already have that design.

Biggest problem you will have is the overall height associated with the structure rigidity. By keeping the rectangle design (longer than its width), you get a better rigid structure in direct comparison to that one which is square. A track system with many supports would hold the upper and lower portions better than not so many. How many? Depends on the weight and surface area you have.

If you have ever camped in a pop-up during rain and wind, you would know the top swivels in the wind. Then with is not being 'rigid' to the rest of the camper, the rain hitting the top echos through the camper. The canvas does the same thing.

If anything, you could look at building a lower box which would be 4-5' tall. Then add a fiberglass truck topper over top. With the fiberglass top down, you could still enter and walk through though bent over. With the topper either popped straight up or at an angle, you would have standing room. When at an angle, you really don't need the top space with a table/bed at one end of the camper. You really don't use that upper space for standing. Most campers are square due to the easiness of making it that way. Think about where you actually need the 'standing head room' and draw out that area for it. Then configure a pop-top camper for that requirement. You would probably be better with a rear entry design. Have you seen the pics for the Winter Warriors?

[Thunderknight]

Thanks for all of the replies.

I think this will be my plan:

Frame the lower part of the TTT to be 4 feet high without a roof at this time. This is for a few reasons:

1) I can't decide how I want to do the raised roof! I think I need the lower part in place to better visualize my next step.
2) Standard size (i.e. 4x8x4)
3) Just fits in my garage at 4 feet high (on top of the trailer). This will allow me to get the lower part done while it's still too cold here to work outside.
4) Should be high enough to get inside the 4' trailer and raise the roof if I go with a design that has to be done from the inside.

I think I know how I want to frame (stick) and skin the walls (1/4" exterior). What I am still pondering is what to use for the framing. Weight is not a big concern to me, so I'm tempted to go with 2x4x48 because it's an easy size to work with, easy to get in quality (vs. the 2x2 and 1x3 and 1x4 they have at the local stores are all warped and/or split and/or knotted...but I know I could rip the 2x4s down too). For the small number I will be using, the savings in weight doesn't seem worth the hassle. Plus a 2x4 cavity would allow me to put in standard fiberglass batts for an R-13 rating. Nice and easy to put in a 16" OC stud cavity versus cutting strips of foam (which I did for the underside).

(I'm prepared to duck as the bricks are thrown, because this beast will be compared to building out of bricks! )

Before I start the walls, am I asking for trouble (besides weight)? I feel there are definite advantages to using the 1.5" thick (2x4 dim) framing method, including ease of assembly, availabity, standard electrical (i.e. boxes and running the wires through the studs).

I did consider doing 1x4 framing, but then the insulation won't quite fit and it seems like a thin surface to screw the skin to.

Hey, it works for houses...right?

[Laredo]

Here's my tip: if you're really gonna frame it out of 2x4s, build it 4'6'' wide!!

The reduced interior dimensions won't seem like a lot at first, but when you finish those thicker walls, you will be amazed at how many things that do fit on a 4x8 floor no longer fit on the now 3'9''x7'9'' floor.

[angib]

you will be amazed at how many things that do fit on a 4x8 floor no longer fit on the now 3'9''x7'9'' floor.

Actually, if the outside of the upper, lifting box is only going to be 4'x8' (so it can be skinned with normal 4x8 ply) then the inside of the lower, fixed box will actually be 3'4"x7'4"!

The 4" loss each side is made up of:
1/4" upper box skin
1-1/2" upper box framing
1/2" clearance between boxes
1/4" lower box skin
1-1/2" lower box framing

Andrew