Suspension on a tradie trailer

You might be able to save yourself a lot of time, money & possible disappointment by considering something like this top of the range camping trailer. TRACK OASIS LINK
I went away with somebody that had done what you are planning & whilst the suspension survived almost everything else didn’t, there is far more to a good off road trailer than good suspension. My friend found that out the hard way & had to part with plenty of his hard earned cash for repairs at Innamincka!

It will be the front spring mounts that might need strengthening no matter what sort of spring you go with.

I bought a near new semi offroad 7*4 and i got rid of the silent slipper springs and put in greaseable shackle springs with the offroad dampener that is supposed to do a similar thing to a shock absorber. The front mount that come with the kit is far stronger than the original. It is 1350Kg rated suspension so a bit bouncy unless fully loaded but reducing the tyre pressure to 20 pounds settles it down a lot and the tyres still run cooler than those on the car on the bitumen and corrugations.

I would recomend that you put some serious thought into fitting brakes to it even though rego doesnt require them, you will be happy you did if your towing 750 kg on dirt where there are animals hopping around.

Look at the huntsman site for some ideas.

John
If carrying a load that round axle will have to go, it won't withstand much off road use and the bearings are too small for fitting larger wheels which have more leverage and angular force induced when cornering.
The springs are short and sudden non compliant items which will transfer sudden forces to the trailer body and contents. For life and durability it is best to change them.
Longer, eye each end type springs/rear shackle, will be far more compliant of rough roads and the trailer will not bounce. That will be enhanced by fitting shocks to the axle so it absorbs. I used HJ60 landcruiser front leaves, some leaves removed, with shocks set at an angle. Someone recently said shocks can't be more than 30 off vertical. Mine, for fitting reasons, are around 40 degree from the horizontal and work very well in controlling the 50mm sq axle. The axle moves rearward during spring flex so shocks are mounted behind the axle to the bodywork. Still with 14' wheels though.
PS Landcruiser springs have military wrap of second leaf over the front eye and so is more secure if the main leaf ever breaks, instead of the axle suddenly wanting to leave the trailer, not nice with cheap poorly designed springs.
LC springs also have a larger front and rear eyee than trailer springs and use larger pins and bigger bushes which also absorb shock. Stronger front and rear mounts are required too. Spring hangers made sensibly provide a longer patch of area and weld opportunities to the minimal frame and so spreads the load over a wider area, further lessening any possible failures.
While some trailers are ok, some are not, and require some additional plating or continuation of A frame structure to ensure the forces are taken through sufficient RHS to vital components instead of through some sheet metal areas as many trailers are designed.

If you're looking at doing Outback travel and off road camping you can find plenty of good soft floor campers fairly cheap second hand and I'm sure the outcome would be a lot better than trying to get this trailer ready for such Adventures

John,

Just looking at those pics, IMO the trailer is not really strong enough to do anything but sealed roads and smooth dirt. It's too lightly built and I think if you strengthen some part of it to accommodate better suspension for touring, that will just transfer or impose loads to another part not designed to take them.

I could be wrong and I won't be offended if anyone offers a different opinion!

Cheers

Mate. I think the suspension is the least your worries with that trailer.

Sure it would be ok for a quick weekend trip somewhere, definitely not something I would be comfortable towing out bush for 3 to 4 weeks.

If you think I’m being harsh you only have to see how many GOOD trailers you see abandoned in the outback. Left there as though it just a piece of litter beside the track.

Cheers Greg.

It might survive provided you drive it with a lot of mechanical empathy, but I agree with the guys above, you would probably have to do a bit of work to it to make it bush ready and not have it shake its self to bits.

Flipping it over and beefing up the draw bar so it meets the front suspension mounts, installing new springs, new spring mounts, new wheels, new axle etc.
You are basically up for building a new chassis and dropping the box on top which is going to be a few $$ and a fair bit of work.

Personally, I'd seriously look at a Ex Army TRAILER, LIGHTWEIGHT, CARGO, 750 KG (HAULMARK), MC2.
They are going for around the $1000 mark, are are tough as nails and all you really need to do is fit a new hitch and re-wire the plug.

https://www.australianfrontlinemachinery.com.au/vehicle-types/trailers

I agree with the others who have said the trailer looks too lightly constructed for Outback roads. The easiest way around it would be to remove the box and put it on a more conventional trailer chassis. You may get some good ideas from this one.
TRAILER PLANS

I noticed he has used four shocks after finding two were not good enough. They are on a steeper angle than they should be and so are many on camper trailers and caravans. Maybe that is why so many of them also have four.

Note the way he has mounted the springs. He mentions "axle steer" . Car axles change angles as they move up and down. They swing in an arc around the front shackle bolt. Suspensions with coil springs and linkages do the same thing. Trailers with their short high arc leaf springs mounted at the same height each end under a flat chassis should be in the history books. The path taken by the axle as it moves up and down is the complete opposite to car axles and this does adversely affect stability.

This link shows you where he has taken it.MAP There are thousands of ks of dirt roads on that map but there is no very rough ones like the Canning Stock Route, Gunbarrel Hwy, Anne Beadell Hwy, Sandy Blight Junction Road and the Connie Sue Hwy but I doubt if that trailer would have any trouble handling them.

Unload those slipper springs as they will give you grief. I have several trailers and 2 have slipper springs and both have had spring dislodge from the retaining cradle. This use due to the rough road the boys tow these trailers on to and from job sights. The other trailers are tandem with rocker spring and hve never given any trouble. If you wish to stay with the single axle, I would place eye to eye with greaseable shackle on the rear and beef up the front hanger and replace the bushes. Use new bolts and a nyloc nut with a springwasher and it will not come loose. this is what I have done to all the trailers now

HI
The 1st and 2 nd photo tell a story
Looks like angle steel main frame
Looks like Z or top hat section floor support rail [ left to right ]
Positive its a RHS draw bar


Need at least falcon bearing axle 45mmsq beam
Slippers Springs for the weekender fine but for unlimited miles longer bushing supported springs needed .

My honest opinion is forget it unless you intend to stick to the bitumen and the occasional graded dirt road. To many people try to tow trailers where they should not be and it all ends in tears and lots & lots of expense, believe me I have seen it many times in my travels.
Cheers Bazza