4x4 off road trailer

The next was to add the A-Frame (Disselboom).

The best way to do this is to put the A-Frame underneath the floor. Do not weld it to the corners of the floor as this is not very strong.

I heard a campfire story years ago that if you extend the legs of the A-Frame, they must point to a point behind the ends of the axle. How true it is I do not know but I have build three trailers that way and they are extremely stable at high speeds and it works out that the A-Frame is narrow which makes it possible to turn sharper. So whether that story is true or not, it works for me.

The illustration below should explain what I am trying to say. The blue circles indicate where you would weld it to the chassis when building a normal trailer. My trailer is a tipping trailer so the attachment to the chassis was a little bit more complex than this. I did not add the explanation of the tipping part because it becomes too complex and might confuse most of the readers.

It is a good idea to weld the A-Frame to the chassis before you attach the axle. It just makes it easier otherwise the axle will be in the way and make it difficult to weld it properly.

To center the a-frame I measured the center of the width of the trailer at the front and at the back. I then laid a long length of 25mm square tubing on the frame connecting the two marks. I determined the points where the back of the a-frame must be and then lined it up with the square tubing find the point where the two legs will meet.

Always remember if you weld something like this it is advisable that you clamp the pieces you want to weld in position before you start welding. Then first tack all the pieces in place. Make 100% sure it is in the right position. Then only start welding it properly to the chassis.

After you welded the a-frame to the chassis you weld a 8mm plate to both the top and bottom end where the tow coupling will be attached.

The legs of the a-frame on my trailer is each 2.1 meters long and only 1.1 meters of that is on the outside of the trailer, the rest are under the floor.

I added hinges to the rear ends of the a-frame in order to enable the trailer to tip. I simply used huge hinges which one use for heavy gates and welded the one end to the a-frame and the other to the frame of the trailer. I bought these Hinges from Stan Rio in Silverton Pretoria (a normal steel dealer). See pictures below:

This hinge will be strong enough to withstand the up and down forces when driving on rough terrain. The biggest force exerted on the a-frame is the forward force when pulling it. For that I welded a 12x12mm square bar on the a-frame at the inside of the floor. This square bar will work as a stop to prevent the forward movement of the a-frame.

On the outside I welded a 50x50x5 angle iron. I screw a bolt through this bracket into the floor to attach the floor to the a-frame. On the floor side I welded an extra 50x50x6 angle iron to make it stronger.

And in the end it can work like this.

Next I had to position the axle correctly on the spring packs. For this I've put the chassis upside down and attached the spring packs to their position. Then put the loose (I bought new axle) axle bracket on top of the springs pack and then the axle on top of the bracket. I did this with the wheels on. Then I made sure that the gap between the wheels and the frame are exactly the same on both sides.

I then tacked the brackets to the axle. Removed the axles and welded the brackets properly to the axle. Below are photographs of the axle with wheels and the brackets welded to the axle.

The type of axle is another long debate. A braked axle (one with brakes) will cost you about double the price of a un-braked axle. If your trailer plus load weighs more than 750Kg it must have brakes. I did not use a braked axle because at the time I could not afford one and we do not load the trailer that heavy. Some people might say that you need brakes when off-roading and you go down a steep hill, this might be true but I have not had any problems up to now. The axle I used I bought new from Roadque in Pretoria.
(012)332-4612. The axle is rated for 1.8 ton, but because it does not have brakes I can only use it for 750Kg.

Building your own off-road trailer