Single Axle Spring Mounts on Flatbed Trailer

I would suggest studying a few well built, Pre-Engineered trailers of the same caliber as the one you are designing. Without knowing more specifications on your particular built, its hard to give any real answer.

But In general, all the calculations have been done long ago. So there is no real need to do them over, unless you really wish to, or your trailer is a one off custom build.

There was a document (Standards Australia or more probably SAE, can't remember which as this was 35 years ago for me) that outlined all that you need to know. Basically the centre line of the axle in relation to the deck and the (spring) mass of the trailer can be used to determine hitch load. If I recall corerectly the answer to that question is around 10% of the mass of the laden trailer - too much loads the tow vehicle pull and drops the towing vehicle, too little decreases stability.

But the core of your core of your question is (presumably) about where to put the spring hangers when leaf springs are used and a spring shackle/pivot style attachment is used rather than the cheaper and cruder slipper/pivot type method.

All I can recall is some indicative stuff. For example the spring can be broadly treated as a three piece system, about 1/3 fixed in the middle and 1/3 at each end of this, to the spring ends, that arc up and down to simulate the spring flattening. You can use this to get an idea of amount longitudinal movement that takes place - this effects bump steer and shackle angle change during bump and under load. First important point is that the shackle must not go over or go near going over centre. Less important it that a long forward spring hanger, about equal to the camber (bend) of the spring will cause the front part of the spring to be near horozontal and the axle to move up and down near vertically with change in load and reduce axle steer in bumps. Very important point in getting a good design, as distinct from something that works, is that the length and starting angle of the shackle, and the spring camber interact . This can make the actual spring rate vary from 50% to 150% of the nominal spring rate within the normal operating range of the spring. A good design will aim for 50% nominal spring rate when the trailer is unladen and 150% when it is laden.

If you can't find the document that I referred to above (or one similar) then the above is probably enough to allow a rough geometric assessment of what you propose to be done.

I believe if I understand your question properly it would depend upon the structure of your deck. The springs need to be wide enough apart to be stable, but not so wide that they create tire/fender clearance issues. Without seeing your design or at least your dimensional needs and component dimensions it is very difficult to answer your question.

The springs must be mounted to the frame of the trailer. The wider the frame is, the more stable the trailer will be to swaying on turns if all other things remain the same.

As for the distance from the axle, try to determine the sprung weight of the trailer loaded, and unloaded. Select a spring that will live comfortable with that weight. Then do a test fit of the wheels, tires, springs, and desired hight of the trailer. That should give you an idea of the placement of the spring hangers. Don't forget to figure the deflection of the springs as they are loaded. Your spring supplier should be able to help with this. Good luck.

You have to know a couple of answer about your trailer structure and your loads which will be start start back of your trailer and it s gonna finish end of the trailer. Or what will you carry w your trailer for instance -single point loading or spread loading- they are important for your axle position. If u don't know or don't calculate you will be get big problem when you are pulling your trailer. All reasons are gonna effect your car that cause I am asking for. for example, if you don't calculate and put your axle close end of your trailer, your car carries more then it s suppose to carry. Your car's pulling weight limit must be approximately 200pounds (support's reaction force-it s not your trailer's capacity dont misunderstand me please.) . If u put your axle 20inches different then it s suppose to be, your car can be brake etc. anyway, You have to tell us, first of em; * What will you carry w your trailer and how * How much weight can your car pull? (or you can tell me your puller model, truck-car-van etc) * How many inches is your tailer length ? ( I would prefer mm(millimeter-metric system) I know that my answer was too late, but it s very important and can be useful.