4x4 trailers, build your own

Then I added the floor. I used a 3mm thick plate for this. Some other off-road trailers also use 3mm thick floors, but most of them only use 2.5mm thick floors. Because my trailer will be a multi purpose trailer which will be used to load bricks and mortar, I decided to go for a thicker floor. If you only use your trailer for camping, there is no reason your really should use 3mm, I am sure 2.5mm would be perfect for you. Because my trailer is 1.2 meters wide, I only had to cut off a 400mm piece on the length of the plate. No cutting on the length was necessary.

I have a big (1.2mx2.4m) steel table. I placed the sheet for the floor on the table and put the frame on top of it. Then welded the floor onto the frame.

I actually screwed up big time here. I know that the metal will expand as it heats up So I started at the one end working towards the other end as to give it space to expand to. Still the metal distorted and my floor is not nice and flat. I should have welded smaller runs at a time and allowed for cooling after every second weld.

Just to overdo it nicely, I also welded the corner supports to the floor.

And then welded it all the way round on the outer edge.

I added extra support on the inside of the lip channel in order to prevent the lip channel from bending open. I added 20mmx3mm flat bar.

On the area where the saddle is attached to the frame, I welded an extra 50mmx5mm flat bar for extra strength. I was afraid that the thin wall thickness of the lip channel might not be enough to support the vibration from the springs. It actually happened to me years ago on a tour through Namibia where our trailer's one saddle broke out from the frame and damaged the frame. Luckily we did not loose the trailer and repaired it in Swakop by doing exactly what I did here, to weld in another piece of flat bar.

Just to make sure the flat bar cannot move, I gave it a proper weld just above each saddle.

The position of the axle is a much debated point. It is very important to put the axle in the right position because it will influence the stability of your trailer. One place where it must definitely NOT be is in the middle of the trailer or in front of the middle.

The further you put the axle to the back, the more stable your trailer will be. BUT if you put it too far back the load on your vehicle will be too much. The position of the axle is pretty much a personal choice. Some of the off road trailers have it as far as 300mm behind the centre. I personally do not like this because you will end up with a high load on your tow bar. I know of various people who had to put in firmer suspension for their vehicles because of such trailers. I placed my axle 150mm behind the center of the trailer. (This is the center of the floor part of the trailer, excluding the tow bar)

In order to determine where you have to weld the saddles for the leaf springs, determine the center of the floor. At this time the floor will only be a rectangular block, but the time has come to now mark the front of your floor clearly. Get the center of the floor and then measure (in my case) 150mm to the back and make a clear mark.

Attach the saddles to the spring pack and put the spring pack on the frame so that it stand up in position. You will note that the bottom blade will have a hole in it. That is the hole that will keep the axle in place. Align that hole to the mark you made where the axle must be. Only do the one side for now. Position the spring pack. Make sure that it is aligned properly and then only tack each saddle to the frame. Now you measure the distance from the front saddle to the front of he frame and use that measurement to determine the position of the saddles on the other side.

I might also mention that I bought a new axle and at this time the axle brackets was not welded on yet. If you bought a second hand axle with the brackets already attached to it you would have to fit the spring packs to the axle and then put it on the trailer in order to determine the position of the saddles.

Building your own off-road trailer