Thread: Heavy Duty Flat Top in the pipeline

Hey Sean, Welcome to the forum.

Technically, there's no ADR or Australian Standards requirement for suspensions on a trailer under 4500Kg ATM, only for couplings, lights, tyres and brakes. Some registering authorities can have issues with axle ratings if you use non-standard bearings, so if you starts with an off the shelf trailer bearing setup, then it's easier to obtain any required literature to justify weight carrying capacity when you go to register it, bearing in mind, as the manufacturer, you are the one responsible for the integrity of the trailer for its entire life (barring wear and tear) irrespective of subsequent owners.
Also, you need to be aware of the axle capacity rating difference between load sharing and non load sharing. The axle capacity of a non load sharing suspension must be 120% of its share of the rated capacity of the trailer, so a tandem 3500Kg must have axles rated to at least 2100Kg. Trailer bearing capacities come as 1600, 2000 and 3000Kg, so to get 3500Kg on non load sharing you need to go the 3000Kg. With the 2000Kg bearings, you'd get a 3,333Kg trailer rating. Most independent suspensions are non load sharing, however, if you interconnect the air supply to each of the airbags, then it would be technically load sharing, so 2000Kg bearings will get you 4000Kg axle capacity.

Yonnee,
Thanks heaps. I have read and re read the the VSB1 bulletin over and over and only ended up more confused. Especially on load sharing and the 120% thing.

I will pursue designing my own setup, in short it will be Landcruiser rear leaf springs, with 3000kg axles, except instead of a rear spring hanger, the leaf will be cut short, the airbag mounted behind the axle, shock absorbers in there too and to keep it all straight, panhard rods for each axle. If it all works I should get excellent airbag ride, height adjustability with the ability to make the trailer tilt. I should be able to get the leaf springs and shock absorbers cheap(heaps of them thrown away at the local 4wd shop) and the panhard rod will probably be from the rear of an 80 Series Landcruiser.
I'm open to any other suggestions before I start, last time I built a trailer it was for a portaloo and that was 15 years ago.....
Where is the best place to get the axles?
With a bit of luck, a new kitchen in our house (old kitchen already removed and tiles throughout going down as we speak) will keep the minister for war and finance happy and I can get on with this project (challenge...)
Thanks again
Sean

I agree with you that the new VSB1 is a little more confusing to read than the original. The current version makes it sound like you need each axle to carry 120% of the total load, so for a 1666Kg trailer, you'd need 2 x 2000Kg axles...

Wow, 3000Kg axles. You do know they're made from 65mm Sq. solid axle steel...?? For me, the cost saving dropping 170Kg from 3500Kg to 3333Kg by running 2Tonne axles would be pretty substantial.

Yonnee
No I don't really know what the difference in price would be, but I do want it to be strong. I will weigh up the options when the time comes.
Cheers
Sean