Having a trailer built need your help

[Davagio]

I am having a man weld a trailer together for me and i have some basic questions as i know nothing about frames. I am sure this has been covered in 20 threads but to be honest there are so many posts on this board that a person just gets lost. So if you could answer some basic questions that would be great.

5X8 is the size of trailer i am making by the way

The Metal

1. 2" or 3" 3/16 angle?
2. 2x2 tube?
3. 3x2 Channel?

What is your thoughts on this matter, I want a happy medium (not overkill) and of course i am trying to keep weight at a minimum


Axle Distance from the rear

2. How far back should the axle be mounted? 30-40% from the rear?


Frame Modification needed?

3. I am planning on doing an over the fender (making it a 5x9) build so can i just extend the wood over it without making the frame larger (behind and and in front of the wheels)?


Anything Else Helpful you could add? Thanks

[Kody]

The initial decisions are the most important when considering a new project like this. I had to make the same decisions when I designed my own trailer frame. I decided to make my frame from 2 x 3 x 1/8 RHS (Rolled Hollow Section aka :- Rectangular Hollow Section). This section was used for the frame perimeter and the A frame draw bar. The center of the frame was filled in with 2 x 2 x 1/8 Angle Steel. The problem is that the frame must also be as rigid as possible and still be as light as possible. If the frame is able to twist and flex as it's traveling over rough and uneven roads, the timber structure fastened to it, will also twist and flex. This can impose huge loads on all the joints of the woodwork resulting eventually in failure of the joint and probably a horrendous repair job. Some structures ,eg, monocoque, can absorb a much greater amount of punishment but this type of structure needs to be carefully designed and very carefully made.
A trailer frame made from 2 x 2 x 1/8 RHS is great for an all steel box trailer as the steel sides add immense strength and rigidity to the frame itself. Without the extra steel supporting the frame in a TD I feel that this lighter construction would lead to failure sometime in the future when you certainly don't need a failure of disastrous proportions.
A frame made from 3 x 2 Channel will weigh as much as one made from 3 x 2 x 1/8 RHS and possibly a little more. I myself don't like Channel steel as it is very awkward stuff to cut and fit and weld up. It is so much easier to cut and weld RHS. The biggest advantage of using RHS is that there are no "hidden" pockets to collect mud and dirt which will exacerbate the forming of rust, even though the structure is painted with the best paint there is. RHS is also very easy to paint. When I built my own frame, I also filled in the ends of every open tube to keep the water and crud from entering into the RHS and creating rust within the section.
The frame can be completely made from steel that has been galvanized. Galvanized steel comes in two forms, hot dipped or electroplated. Hot dipped steel must have the zinc (ie, the galvanizing coating) ground off every site where welding is to be done. The welded joint must then be re-coated with a zinc rich paint (commonly known as "Cold Galvanizing" paint). I have used the electroplated galvanized steel and I will never use it again. It is a pain to weld and the fumes are horrific and dangerous. When welding this type of steel, it is very difficult to keep a stable arc. Welding galvanized RHS burns away the zinc coating on the inside of the RHS. The outside joint can be painted but the inside will rust where the zinc was.
You may be able to buy 2 3/4 x 1 1/2 x 1/8 RHS to use for your frame. This might be suitable for you but I would go the 2 x 3 x 1/8 for preference.

My own trailer frame is 5 foot x 10 foot. The axle is about 41 inches from the rear of the frame measured from the outer end of the frame which equates to 34% of the trailer frame length, the draw-bar length notwithstanding.

If you are modifying the length by extending the floor bearers over each end of the frame, you may or may not require extending the steel framework at each end. A timber strut can be bolted on across each end and then a timber form to suit the shape/s of the ends can be easily added shaped to suit. If the ends are verticle or sloped, the woodwork is easy. If the ends are curved like mine, some extra thought will be needed to blend into the curves. This extra work sounds difficult but it's not hard to do.

Look for my own building posts and you will see photos of my trailer frame. I have also fitted shock absorbers/dampers to the axle but I'm not sure if these are shown.
Hope this post helps you, The other guys here will no doubt offer you more info and post welcome comments, for and against for what I suggest. Take heed of what they say and compare all notes. Good luck with your build.

Kody

[Davagio]

Kody thank you for your response, i guess the trouble i am having with the most is having people respond to my post so i can get suggestions!

And I will definitely put some thought into some of your ideas. Building the foundation is a critical step as you stated, and you have helped me with some of your advice

[wingloader]

Search for the "X II" build by Zach. He did a 5 foot wide over a 4 foot trailer. I am using his ideas to design mine over a 4x8 trailer as well. His design was awesome.

Joe

[nevadatear]

Have you checked out the trailer tutorial on the drop-down list at the top of the page under "design resources"?

[Davagio]

Have you checked out the trailer tutorial on the drop-down list at the top of the page under "design resources"?

I have been looking through that actually, i appreciate you pointing me in that direction. I am still confused as far as what metal i should be using because his teardrop will be about 400lbs lighter than mine so i am not sure how much of a difference that would be in support needed for my own frame.

[asianflava]

This is the frame for my 5x10, very minimal with only one crossmember which stabilizes and strengthens the tongue. The Dexter axle serves as the rear crossmember. It is all made of 2x2x1/8 square tubing. I ended up changing the tongue to a larger tube though. Just remember that the frame only serves as a solid attachment point for the coupler and the axle. The strength and rigidity comes from the trailer body's box section.

[alaska teardrop]

I am still confused as far as what metal i should be using because his teardrop will be about 400lbs lighter than mine so i am not sure how much of a difference that would be in support needed for my own frame.

Some years ago forum member, Paul C, supplied the Australian government 'tongue strength regulations'. They are the only engineered - no guessing guidelines that I know of. Member, Andrew, has deciphered the formulas & explained how to use them here: http://www.angib.pwp.blueyonder.co.uk/t ... tear84.htm

You can plug in your intended trailer weight, tongue length and tongue design in order to determine the safe & proper steel (or aluminum) structural shape & size to use.

Fred

[Davagio]

Search for the "X II" build by Zach. He did a 5 foot wide over a 4 foot trailer. I am using his ideas to design mine over a 4x8 trailer as well. His design was awesome.

Joe

Thanks that does look like an interesting build, and can maybe help me when i get into the design aspect of it.

[Davagio]

This is the frame for my 5x10, very minimal with only one crossmember which stabilizes and strengthens the tongue. The Dexter axle serves as the rear crossmember. It is all made of 2x2x1/8 square tubing. I ended up changing the tongue to a larger tube though.

Did you end up using a 2x3 1/8 on the tongue?

Also how long is that tongue it looks at least 4 feet from the pictures, and is there a reason you didnt add any a frame supports? Just curious

[asianflava]

After I built it, I used it a few times and I felt that the tongue was too weak so I chopped 18 inches from it. The only drawback was that it made the trailer tricky to backup. It was fine for years until I had to move the tongue broke in Jackson, MS. Granted, the trailer was overloaded (everything that couldn't fit in the truck) and the road was very rough. It was packed so full that a box slid against one of the doors and hit the lock from inside. The combination of the extra weight and the hammering was probably too much.

I wanted to replace it with 2x3x3/16 but the trailer repair place couldn't get it on short notice. They ended up using 2x4x1/4, a little overkill, but I had them add the 18 inches back to the length. The way you see it in the picture, the tongue extends 5 1/2 feet from the front crossmember, but only 4ft extends past the apex of the front trailer body.

I didn't add any frame supports because it doesn't need it. The rear doesn't see much weight because of the galley, and the front is to strengthen the tongue. The Dexter axle also acts as a crossmember because it is a tube connected to both sides.