MY TRAILER FRAME DESIGN

[Kody]

G'day guys
This is the drawing of my trailer frame showing all the details of the layout. All going well, I will begin building it next week. The dimensions are in millimeters but the length is 120 inches (10 feet) and its 60 inches wide (5 feet). The walls of the cab will be fitted to the outside of the frame to keep the full 60 inch width inside. The "A" frame is not shown as I will add that on after the basic frame is constructed. The top of the frame will have 2 3/4" x 1 1/2" pine bearers bolted to it and the 1/2" ply floor will be screwed to the bearers. The 2 3/4" wide pine bearers sound like overkill but you will see why I am using these when I begin to post the pictures of the build in the build section. The cab will be bolted to the bearers through the sides and will overlap the frame down to the bottom of the RHS. I will be using 1/4 NF-28 tpi bolts but would much prefer 1/4 BSF -26 tpi. At least I can still buy !mperial bolts here, ( I hate the metric system with passion!). There are no dramas using 1/4" dia. bolts as the core strength is still far greater than threads cut with a die. The bolts made by a manufacturer have rolled threads and in a high quality bolt, the minor diameter still has ample strength. All the bolt hole will be drilled first before welding and transferring the holes to the floor ply will then be an easy task. Before I weld all the parts of the frame together, I will slip a 1/4 bolt into a piece of RHS and see how much load I can apply before the bolt snaps or the bolt has pulled completely through the timber bearer. I really don't want to go up to 5/16" bolts unless it's absolutely essential. Six of the 1/4" bolts will go through the 1/2" floor for extra strength and integrity.
All the open ends of the RHS will be covered by welding an inside fitted plate and the finished frame will be given two coats of Cold Galvanizing paint. The finished colour will be red. The springs are mounted on a short length of 2" x 2" x 1/8 RHS as the 1 3/8 wide RHS is not wide enough to support them.
The drawing for the side view and section of the cab is almost complete and I will post that also to show you what I am building. Any comments are welcome.

Kody

[KCStudly]

Sorry if I am stating the obvious, but this has bitten other builders before.

Make sure you know what your material will be for the ceiling and roof. Some people have been misfortunate to realize after the fact that 60 inch Baltic birch will not land on walls that are spaced 60 inches apart inside. If you are using 60 inch stock for you roof and ceiling and want your walls to overlap the sides of your trailer frame, you might consider making the frame = 60 - (2 x wall thickness), that way the 60 inch skins will cover to the outside of the walls. Otherwise there is a lot of material waste using larger sheets.

When I was laying out the cut lists for TPCE I thought that there would be plenty of cabinets and stuff that would use these extra off cuts, but there ended up being so many big pieces needed, and the small pieces for the cabinetry also needed to be long and slender, that it just didn't work out that way. I ended up piecing the panels for my floor and bulkhead together just to save a few sheets. In hind sight I should have just made the camper a little narrower, or, if I thought I would have another use for the leftover, just bought the extra sheets up front and saved on shipping cost.

If you are using larger metric stock, or are planning on installing a nailer shaped to the inside top edge of your walls that may not be an issue for you, but then there is still an uneven transition to deal with where the edge trim will want to be.

I planned from the beginning to be 64 inches out-to out on my 1-3/4 thick walls in order to fit a std 60 inch Queen size mattress, but could have saved lots of material cost if I had just cut down a foam mattress enough to fit in between walls that were 60 inches outside to out.

I'm looking forward to following your build.

Do you have a thread going in the Build Journals section yet?

[Kody]

G'day KC
Many thanks for your notes and comments on floor width and wall thicknesses. Yes, I have given many hours of desperate thought into how wide, how high, how long to make the TD. Nothing is final until I make the first cut in the steel RHS's. I have drawn stacks of drawings with the CAD to explore and develop a suitable size that will prevent as much waste plywood as possible. The big problem here in Aust. is that very few sheets of ply are made and sold in Imperial Units. The overall width of the cabin will be 61 inches (?) and yes,this does create a huge amount of wasted plywood. I drew up a profile view and layed out the 12mm plywood for the walls. UGGHH, so much waste! I need 5 sheets of 1200 x 2400 x 12 for the side walls. This will result in about 30% loss of ply with 4 sheets. The roof and ceiling will be about the same so if I can make the ply go further by restricting the height and width an inch or two there would be a big saving. My greatest concern is not the cost or how big or small the living area will be. My concern is that my precious wife suffers from claustrophobia and every extra inch is a blessing for her. I will still be looking much deeper into the finished sizes for H, W and L before I start.
I much prefer to lay the roof ply with the grain going across the the cabin roof rather than parallel to the centerline. This makes it much easier for the sheet to bend around the profile as the profile shape has a fairly sharp and decreasing curvature at the ends. Again, there will be significant waste to consider. Very little can be used for other parts of the construction. The only sheet I can buy that measures an actual 5 feet x 10 feet x 1/2 inch is the plywood for the floor, all other sheets are metric. The 4' x 8' equivalent in metric size measures 47.24 inches x 94.48 inches, (3' 11.24" x 7' 10.48" x .47").
The first photos I will be placing and sharing in my build post will be of the steel cut to size and photos of the all important welds. All the welding will be done using the common stick welding rods. The choice of rod will be Satincraft 6013.
All comments either positive or negative from everyone are most welcome

Kody and Joe

[asianflava]

IMHO You can ditch two crossmembers, you don't really need them. I only have one for the tongue to attach to, the torsion axle in the rear keeps the rear in check the floor doesn't even sit on it. If you are going to set the body so it overhangs the frame, it might be easier to build the body first then build the frame to suit the body. I built my trailer like this because building the body first wasn't as much of a financial commitment. I figured that if it wasn't working out to my liking I could abort the project without too much loss. It also gave me more room to work since I built my 5x10 trailer in a single bay of my 3-car garage, immobile cars took up the other 2 spots.

BTW: I am one of the ones that found out that 5X5 baltic birch isn't really 60in it's about 60 1/8in. It worked out because it gave me some clearance to tuck the frame into the body. The only spot where I got burned was that my hurricane hinge is a little shorter than optimal.

[Kody]

After going through all the different parameters and crunching the numbers, the decision has been made at last. The inside width of the cab will be 60 inches. This fits in with the standard size of axle. It also provides the maximum width possible using a 5' wide sheet of ply for the floor. To cover the roof and ceiling, I need to purchase 8' long sheets of ply and cut them to aprox. 5' 2 1/2". A total of 10 sheets will be used and when all cut, there will be a total a loss equal to 3 1/2 sheets of 1/8 ply. This will equate to $55.50 in lost plywood. My wife said that $55.50 was cheap to gain two extra inches of width from wall to wall inside. I can buy 6' long sheets of plywood from Brisbane but the transport cost will be as great or more than the 8' long sheets. I have yet to decide on the thickness of the wall panels, it will be either 12mm or 15 mm. The 15 mm thick looks to be best choice. The next size up is very heavy and difficult to handle on my own. I can see an endless chain winch appearing in the shed very soon. There is a place here that sells some very beautiful luan plywood, will check this out further.

Welding the tongue only onto the one single cross beam in the front is not allowed here for trailers. The regulations state "The drawbar (tongue) must be securely attached to a substantial portion of the trailer". This means fastened to a minimum of two cross bars or use an "A" frame also welded to two cross bars. If the trailer should be inspected, the inspecting officers can become rather excited if the trailer isn't built properly.

Kody and Joe

[bobhenry]

Don't worry about the waste ply. There is really no such thing. Cabinets , shelves and even tote boxes are very necessary items. I am still using smaller pieces of Lexan from my 2007 build.

Here is where my waste osb wound up............



you notice the gally wall went in in two pieces because that was the biggest waste pieces I had
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Installing a backer panel for the front storage shelves helped to take the wiggle out of the front end being installed as a shear panel.

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The little flip out cabinets were later covered with a veneer of luan and varnished but the osb made a great solid little storage box and counter substrate. I piece was also used as the let down counter/pantry door.