Help with a trailer

Craig
Suggest you look at myswag.org Aussie forums dedicated to campertrailers with a lot of people building them. A great place to ask that question.

Craig,

I did exactly what you describe with the drawbar extension to a trailer that I have. This was done some 30+ years ago and it has been dragged over some pretty rough ground behind various 4WDs since with no ill effects. As you are proposing, I extended the additional extension square bar back as far as the axle mounts.

As far as the axle extension goes I would think it would depend on the inherent strength of the axle itself and the load you will be carrying. To properly calculate whether the existing axle would be suitable is way beyond my engineering abilities.
Mind you I'm assuming you intend extending the existing axle. If that is not the case and you are replacing with new then all that calculating should have already been done by the manufacturer and they should have that data available.

Good luck with your project

Cheers
Pop

What is the intended use of the trailer?

Besides the wider/ie, longer axle, which would be a replacement of suitable capacity like Pop mentioned, why doe sit require a larger distance from hub to springs?

If going to be used off road, then with the new axle ability you would need to fit larger, longer springs to the trailer has a more compliant suspension to absorb bumps, plus shock absorbers.

If requireing a longer drawbar, perhaps cut the present A frame sections about 300mm bck from coupling and extend from there to a coupling pad. Some top and bottom doubling of the steel will be required to restore integrity to the A frame. Possibly at the sides of the join too.

I saw a large tradies trailer, Glazier, done that way and it had plates at the sides but not the top and bottom which is where the load and stresses are.

My trailer was built using a Isuzu tub so I matched the springs and track width of the Isuzu which meant there was a fair distance from the springs to the hub. The downside is we constantly bend axles. It takes a few outback trips but it starts to camber the tyres and we have to straighten the axle.

If you want to widen the track of the trailer, why not get some rims with a different offset?

A rim with -55mm offset will increase track by about 100mm.

Bob

" I am doing some work to my trailer. I need to make the axle wider but I can't move the springs any further out. This means there will be a lot more distance between the springs and the hub. Would this be a problem. "

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It could be but to be certain I would suggest you talk to a major trailer manufacturer. The size of the axle usually has to be larger the further the wheel is from the spring.

It will also have an effect on the operation of the springs but it may not be all that much of an issue on a trailer. It is on cars.

We have all heard of "spring rate". A few people have heard of " spring load" but I have not come across very many. There is also a feature called "wheel rate". This link explains it Wheel Rate

hi
There are recommended axle protrusion measurements past the spring .
This depends upon axle/ bearing diameter .
Generally 170-200mm , refer to vehicle components web site

The answer depends somewhat on where you are going to tow the trailer and what loads you are going to carry. A new longer bare axle is not that expensive and they are only manufactured from mild steel. Whilst many will disagree I have seen plenty that have been cut in the middle and extended by plug welding a sleeve over the two halves to achieve the required length. Plug welds are preferable to running welds circumferentially across the top/bottom & both sides of the axle (if it is a square axle) or all round the axle be it a round one. For extra strength the axle can be 'strapped' on the underside if required. If the existing bearings are 'car size', usually Holden or Ford, I wouldn't be too concerned about the additional loads imposed by larger diameter wheels. If you do join the draw bar by 'fish plating' over the joined sections, weld (horizontally) 'along' the the plates but do not weld (vertically) the ends. Should the axle have spring centre bolt locating plates make sure once you have centralised the new length axle across the width of the trailer you tack weld the plates back to the axle by placing the tack welds at the front and rear of the plates (not at the sides) so effectively you have welded 'along' the axle not 'across' it.

Wheel spacers are another way of widening the track not sure about the legalities in each state but you need to look at what the safe max distance is for your axel or upgrade to a larger axel for safety.

lets start at the very beginning .. because its a very nice place to start.

1/ you want to extend the drawbar 500mm, that is half a meter.
Ya best option there is to start again ..... cut the old one off and fit a new one in taller section ... a rectangular section will give you more strength for weight and cost.
90 x 90 x 6 HELL ... that is just heavy, and not particularly strong.
Go look at some similar commercially built trailers of a similar size and weight and see what they are using.

2/ if you are increasing the track but not the loading points on the axle it does not matter if you do it by extending the axle or increasing the wheel offset, the engineering result is the same ...... the distance from the centre of the tyre to the bearing point remains the same.

All too often trailer axles are bare minimum spec, the smallest axle the smallest bearings and the smallest wheels that will pass legal requirements.

If you don't skimp on the size of the axle and the type of bearings the overhang should not be a problem

If you are trying to fit bigger wider wheels .... longer axle overhangs are inevitable.

Don't try to fit bigger wheels on lighter axles.

Fit the wheels on hubs that have bearings that are similar to the vehicle those wheels came off and that will require the appropriate axle.

If you are fitting 15 or 16 inch rims with 4wd tyres, don't try to do it on ford or holden bearings and a light axle.
Use landcruiser bearings and an appropriate axle.

YES and you will need bigger brakes to cope with the wheel diameter.

AND

Remember this trailer will now need re-engineering ..... it will probably be easier to re-compliance and re-register it as a new trailer

cheers