Teardrops n Tiny Travel Trailers

I am in the process of designing a pop up Tiny Travel Trailer that would have sleeping accommodation for 4 people, house a bathroom and have an exterior kitchen at the back. It’s body size is 6 ½ ft. wide and 12 ft long and it’s guesstimated weight of 2500 lbs. Although this pushes the envelope of a Tiny Travel trailer, it does however, have a low roof line of 6 ½ ft. in the traveling configuration and is equipped with an exterior kitchen.



As there are many experienced builders and trailer designers on this forum, I would appreciate any opinions you guys have on this design

The trailer will have a body between the wheels arrangement. The main reason is that trailer total weight was not calculated. With the weight of the front bunk bed, batteries propane tanks and possibly a spare tire on the front “A” frame there is a good possibility that the axle would have to be repositioned after construction. Also I would like to have the hitch weight of 7 ½ % of the total weight or about 165 to 175 lbs. to avoid using an equalizing hitch for towing. Another advantage of the body between the wheel arrangement would provide more stability as the pop up roof and the possibility of adding solar panels on the roof raises the trailer’s center of gravity.

The folding roof design is similar to Andrew’s Compact 3 and the Compact GT. The roof will raise straight up and is assisted by adjustable gas springs (lift supports). LS Technologies Inc. of Saskatoon, Saskatchewan advertises that they can modify gas lift supports for the proper output force. This could reduce the required effort to raise and lower the roof. The roof drawings are incomplete as the trail period for drawing program ran out before completing the design work.
However the sealing details, side panels and roof structure construction would be similar to Andrew’s Compact 3.

This trailer features a very low tech front bunk slide out for the fourth person. It is basically similar to a tent trailer bunk end. The way this works is before sliding the bunk end out, two removable bunk support arms are attached to the trailer wall and on trailer frame. The bunk end is then pulled out. The weight of the bunk assembly and the person sleeping on the platform is supported by the bunk support arms. The bunk bed floor is made up or 3/4 in. plywood and the walls roof of the bunk end is ½ in. plywood. The 3/4 in plywood floor slides in and out of groves that are dado-ed inside longitudinal 2x4 or 2x6 lumber which are part of the trailer walls. The sealing method is using an interior compression gasket on the interior flange when the bunk is slid forward and an exterior gasket and flange when the bunk end is moved inward.



The bathroom self storing door is hung after the roof is up. Folding walls will cover up the gaps when the roof is raised. I plan to use a Sealand Sanipottie MSD as the toilet. The toilet would be mounted over a raised platform in which a small black water tank is mounted under it. This gives an additional 8 US. gals capacity to the Sealand Sanipottie MSD holding tank of 2.8 US. gals when the two tanks are tied together. As the Sanipottie has it’s own built in fresh water tank, a pump and permanent fresh water tank is not necessary for it’s use.

The galley plans show that there is no permanent kitchen sink as it takes up valuable counter space and the plumbing for it uses to much space under the cupboard. Dish pans and portable water containers will have to used instead. Since a 3 way fridge is not recommended to be installed against an interior wall, I was thinking of using either an ice box or a 12 volt compressor fridge such as a 3 ½ cu ft. Nova Kool fridge.



My concerns with this design are:
1. Is the large opening for the pop up roof so large that it will make the trailer structure weak and flimsy? Presently the size is 6ft. by 9ft. 6 in.
2. I was going to have the chassis frame built by a local trailer manufacturer using my chassis design. Is my chassis design adequate?
3. Any one out there had any good or bad experiences with the Nova Kool fridges?

Anyway, thanks for your opinions in advance.

Dennis

To see more of my diagrams, go to http://tnttt.com/album_ ... ser_id=605
or at
http://www.geocities.com/d172goy/CanuckTrailer.html

It's obvious that a lot of good work has gone into this interesting design. It will take some time to digest and provide some helpful comments.

One small detail...
The T&TTT album link appears to be for the user's own personal album; for instance, when I follow it, it leads to my album.
The right link for dgoy's album is the one from the Album button at the bottom of his posts:
http://www.mikenchell.com/forums/album_personal.php?user_id=605

This design looks great on paper but how will you keep the water out of the slide out and back of the pop up?

The main frame rails (sides, ends, tongue) are specified as 2"x3"x3/16" rectangular tubing. My 17-foot Boler, at 2400 lb empty and 3000 lb loaded, uses 2"x4"x1/8" rectangular tubing for the main rails, although the 2"x4" tubes of the tongue might be 3/16" thick. The extra section height of the 2x4 makes up in strength for thinner wall, but it is lighter (total weight per foot of length) than the thicker 2x3.

If the 2"x4"x1/8" is good enough for my longer travel trailer - and it certainly seems to be - then I think it might be a better (lighter, probably stronger) choice for the Explorer... although it would make the whole trailer 1" taller.

For an example of how a larger and thinner box is more efficient, compare these two lines from the table in the Tongue strength page of Andrew's design library:
Square Tube - 2" x 2" x 3/16"
capacity (lb-in), vertical/horizontal: 20,900 / 20,900
weight (lb/ft): 4.32

Rectangular Tube - 2" x 3" x 11g (1/8")
capacity (lb-in), vertical/horizontal: 28,000 / 22,300
weight (lb/ft): 3.90

The table doesn't go up to sizes taller than 3", but it is for teardrops and tiny travel trailers. The well-constructed Escape 17 is almost as heavy as the Canuck Explorer is planned to be, and uses 2"x3" tubing.

dgoy wrote:The trailer will have a body between the wheels arrangement. The main reason is that trailer total weight was not calculated. With the weight of the front bunk bed, batteries propane tanks and possibly a spare tire on the front “A” frame there is a good possibility that the axle would have to be repositioned after construction. Also I would like to have the hitch weight of 7 ½ % of the total weight or about 165 to 175 lbs. to avoid using an equalizing hitch for towing. Another advantage of the body between the wheel arrangement would provide more stability as the pop up roof and the possibility of adding solar panels on the roof raises the trailer’s center of gravity.

This seems like a sensible plan, and also allows an interior free of fenderwells, but...

It looks like the body is designed to be just about at the maximum width allowed without wide-vehicle clearance lights (80"). The outboard wheels will add a couple feet to that, and ID and clearance lights become required. The inside wheel also runs a foot closer to curbs. If I were starting from scratch on a trailer design, I would want to stay under 80" wide for the body and the wheels.

I am a little concerned about the mass balance. I don't see anything wrong with a tongue weight of 7.5% of the total weight, but where this low is common (in Europe), the mass isn't stuck out at the ends like this design. They don't put lots of propane and batteries so far out on the tongue as we normally do here, and the Canuck Explorer also has the teardrop-like feature of piling the whole galley (with appliances, kitchen equipment, and food) at the very back. This makes the trailer like a flywheel on a vertical axle: hard to start turning, but also hard to stop turning, and thus hard to control.

Maybe Andrew would like to add polar moment of inertia to the Trailer Balance worksheet? Putting the masses at the end makes the polar moment of inertia high, which more like a flywheel.

A longer tongue would make the trailer more controllable (or stable), even with the same mass distribution. A longer tongue could also mean less tongue weight for the same distribution and axle location, or allow the axle to be moved further back with the same tongue weight. If it were longer, maybe the body could just be longer instead of having the bed slide-out, with minimal weight increase (especially if the battery and propane are kept under the bed, instead of moving them forward with the body extension.

I'm surprised that no one else has anything to say.... maybe people don't watch the "Non-traditional Designs" area?

Well, I'll just keep going on the parts which interest me!

The tongue is an A-frame of the same material as the main frame rails, which seems like a reasonable and effective design; however, it appears to end at butt joints at the front crossmember.

The usual practice with A-frames is to continue past the front crossmember to the main frame rails. The extensions provide a better attachment to the rest of the frame, a direct connection to the main rails to carry the forces applied to the tonque, and diagonal bracing.

Often, this is accomplished by having the top of the tongue members attached to the bottom of the rest of the frame, but the Explorer has the tongue at the same level as the main rails, presumably because the frame is low, and placing the tongue under it would be too low. I can think of a few ways around this:

- Notch the tops of the tongue members significantly to clear the front crossmember - the tongue would still be lower, but not as much. The front crossmember could even be lower in profile (2x2 with a 2x3 frame, for instance) - and with thicker walls if necessary - to provide more clearance.

- Run the tongue on top of the frame. This is rarely done, and it places welded joints in tension (meaning some gussets are likely called for) but I have seen it done in a mass-production travel trailer. The interior plan would need to consider the tongue members above the floor.

- Run the tongue right through holes in the front crossmember, which would then likely be a channel (rather than tube). This is the design used in my Boler B1700 travel trailer.

- Add sections of tubing between front crossmember and main frame rails as if it were a continuous A-frame to the frame rails, but is just interrupted by the crossmember, then plate across the crossmember joints (at least on the bottom) to tie the pieces together into effectively a continuous structure.

- Put the tongue members under the frame until forward of the crossmember, then bend or step the tongue up to the desired height for the coupler. The traditional lightweight moulded fiberglass travel trailers took the bend approach (although Trillium did it poorly and created a weak point which often eventually failed); the Escape 17 uses (or at least used in the ones I have seen) bends in 2x3 tubing, very nicely done; the current Outback (a Trillium design by Team Trillium Trailers in Calgary) has a step created by overlapping sections of tubing.

The frame drawing specifies the axle as a Dexter Torflex #9, or possibly a #10.

A #9 is only good for 2200 lb, but the expected weight is over that, even without cargo. Unless there is some plan to reduce weight, it will need to be a #10.

The #10 Torflex has a capacity of up to 3500 lb. If the loaded trailer weight never exceeds, say, 3000 lb, it might be a good idea to order the axle with the rubber rods cut shorter to soften the suspension to match, for better ride and control. Better a bit too stiff than a bit to weak, but if the trailer weight can be determined before the final axle order, a slightly more optimal configuration can be built.

The drawing shows the frame, suspension arms, and tires with no space between them; of course, this is not true. Actual overall width will depend on the tire width, wheel offset, and hub face to hub face width; and the width across the hub faces in turn depends on the frame width, and the required overhang past that for the specific axle series.

While the rubber springs of this axle design do have some inherent damping, it is still not enough for optimal suspension action (although most people consider it adequate). Shock absorbers fix that, and it might be easier to plan for them now (mounting bracket considerations, space between frame and suspension arm) than later.

Hey... I like it. It'll take alot of work, and it'll need some creative sealing (unless you do a westfailia tent thing on the pop-up, that design seems to work pretty well)

It's dang close to my pop-n-slide-leaksalot design which I'm starting to build. I'm not all that worried about sealing cause I don't camp in the rain.

brian_bp has some great comments. I doubt 3/16 would be necesssary, particularly if some strength comes from the 'box' sitting on top of the frame (there'll be some flex where the door is). I think you could really reduce the weight a bit.

And, I'd definitely move the tires inboard, and have the fenderwells hidden under the dinette. You loose some storage, but you won't be constantly rubbing the tires on the curbs. Move em back too, as your galley is going to be heavy.


As far as tounge attachment, I've made my last 2 trailers kind of like boat trailers - the main frame rails ARE the toungue rails. I cut a triangular notch into the frame rail and bend it and weld it. It's not cut all the way through. For a DIY, I liked that better than a bent toungue (like a boler) or a raised coupler (Like a HF trailer comes with) The pics of the tent thing in my album kinda show this -- look at how the coupler is a attached.

jeep_bluetj wrote:...As far as tounge attachment, I've made my last 2 trailers kind of like boat trailers - the main frame rails ARE the toungue rails. I cut a triangular notch into the frame rail and bend it and weld it. It's not cut all the way through. For a DIY, I liked that better than a bent toungue (like a boler) or a raised coupler (Like a HF trailer comes with) The pics of the tent thing in my album kinda show this -- look at how the coupler is a attached.

I like this idea (for rails becoming tongue). The only problem for most trailers is that you need to
- make the bend inward while still under body, or
- make the bend more than the 25 degrees which is normally used to form a 50-degree A-frame (and live with the resulting wide tongue might limit turning angle), or
- live with a quite long tongue (which might be just fine, especially with a relatively narrow trailer).

brian_bp wrote:[I like this idea (for rails becoming tongue). The only problem for most trailers is that you need to
- make the bend inward while still under body, or
- make the bend more than the 25 degrees which is normally used to form a 50-degree A-frame (and live with the resulting wide tongue might limit turning angle), or
- live with a quite long tongue (which might be just fine, especially with a relatively narrow trailer).

The long tongue (about 3' - 4') works out great for me, as I put a firepit on the tongue for travel. I also bend'em back straight and use a straight coupler, not a 50 degree coupler to help move it back. So I have 8" or so of double toungue straight back, then it Y's out to the A frame. This helps alot with the turning radius issues. It's similar to a typical boat trailer but I can't bend it on dies, I need to cut and weld. On the tentthing, It's held up amazingly well (1.5" x 2.5" 11g frame rails). That gives me a 3" x 2.5" straight part on the tongue. It's plenty strong. I did it to keep the clearance under the tongue as high as possible, it's pretty simple to do, saves a tiny bit of weight, and I had a coupler for 3" sq tube laying around.

Dennis,

I am new on the forum but, I am really considering building a very similar design. Any build pics yet?

Heath