Thread: Engineering design question for tandem trailer

This catalogue is from Industrial Springs in Adelaide. It shows pictures of:

http://www.industrialsprings.com.au/download/cat009.pdf

Eye to Slipper, single axle

Eye to Slipper, tandem axle

Eye to eye shackle, single axle

Rocker - tandem

Rocker - triaxle

Single point suspension - tandem

There are no pictures of air bags or coils on control arms.

Cool. Thank you

Dave TTC
Turning Wood Into Art

Originally Posted by Wahoon

Is there any substance to this. Having just looked at new trailers from several trailer manufacturers, there are a lot of brand new tandem trailers out there that don't have load sharing suspension.

Originally Posted by KBs PensNmore

ADR INFORMATION

Australian Design Rules (ADRs) now apply to the building of Caravans, Trailers and most trailed vehicles. It is your responsibility, whether you are a manufacturer or a private one-off builder, to conform to these regulations. Our staff at SA Trailer & Chassis Equipment Pty Ltd will be able to help you with general ADR enquiries on Brakes, Suspensions, Trailer Plates, Lights, Wheels, Tyres and Chains etc.
For specific ADR information and copies of the current ADR regulations, please contact the Department of Road Transport in your state.
GENERAL POINTS ON ADRs FOR TRAILERS


SUSPENSIONS

1. Trailers up to Gross Trailer Mass (GTM) of 1999kg - Can use Slipper, Shackle or Rocker Springs, or Independent Suspensions.
2. Trailers with GTM from 2000kg to 4499kg - Require a Load-Sharing Suspension when in tandem or tri-axle configuration.
3. Trailers with GTM fro 4500kg and over - Require ADR-Approved Suspension Kits.

Sorry about that I had been misinformed.
Kryn

I'd like to add something to this if I may.
It has always annoyed me that the Transport Authorities in each state seem to think that they know better than the National Department of Infrastructure and Regional Development. NSW RMS for instance, has decided that any trailer that requires a breakaway system, cannot be registered unless the tow vehicle is fitted with a monitoring system for the breakaway battery. And while I understand the sentiment behind it, how can you possibly restrict the registration of a trailer depending on the tow vehicle at the time.
However, I cannot find anywhere on the sa.gov.au site that mentions anything about restricting registration of trailer over 2000Kg GTM to those with load sharing. This is not requirement in the VSB1 bulletin (section 19), the National bible for building small trailers.

With regards to my original query, I have decided to change the design of the trailer.

This is because the air bag setup I was going to use was under leverage, and the air pressures would be too high for the fittings and air hose to cope with. That also meant the pressure needed to actually lift trailer and car from ground level was quite high.

So I am still working out what design I will do. It may be a trailer with a tilting drawbar initially

Thanks for everyone's input

Originally Posted by Yonnee

I'd like to add something to this if I may.
It has always annoyed me that the Transport Authorities in each state seem to think that they know better than the National Department of Infrastructure and Regional Development. NSW RMS for instance, has decided that any trailer that requires a breakaway system, cannot be registered unless the tow vehicle is fitted with a monitoring system for the breakaway battery. And while I understand the sentiment behind it, how can you possibly restrict the registration of a trailer depending on the tow vehicle at the time.
However, I cannot find anywhere on the sa.gov.au site that mentions anything about restricting registration of trailer over 2000Kg GTM to those with load sharing. This is not requirement in the VSB1 bulletin (section 19), the National bible for building small trailers.

Hi Yonnee

a comment from the "inside" ...
unfortunately the National Department of Infrastructure and Regional Development has a tendency to adopt the lowest common denominator when it comes to some standards. The "expertise" tends to reside in the States or private industry.
What is acceptable in WA or NT is not necessarily acceptable in Sydney or Melbourne traffic -- hence the differing requirements.
I think the rule in NSW is that you can't tow a trailer with a breakaway system unless the tow vehicle is fitted with a monitoring system. It then follows that if you present for registration without the appropriate tow vehicle your trailer won't get registered, because if it were you wouldn't be able to tow it home.

Originally Posted by ian

Hi Yonnee

a comment from the "inside" ...
unfortunately the National Department of Infrastructure and Regional Development has a tendency to adopt the lowest common denominator when it comes to some standards. The "expertise" tends to reside in the States or private industry.
What is acceptable in WA or NT is not necessarily acceptable in Sydney or Melbourne traffic -- hence the differing requirements.
I think the rule in NSW is that you can't tow a trailer with a breakaway system unless the tow vehicle is fitted with a monitoring system. It then follows that if you present for registration without the appropriate tow vehicle your trailer won't get registered, because if it were you wouldn't be able to tow it home.

Hi Ian.
So, if you've just bought a new 2500Kg GVM caravan, and in the next month or so are upgrading your tow vehicle, why would you want to spend several hundred dollars getting a battery monitoring system fitted, that's not a requirement in any other state? What makes NSW roads so different that requires you to know mid trip how charged your break away battery is?
Isn't that like making you fit cameras to all 4 inner wheel arches to monitor your brake pad thickness or tyre tread depth while you're travelling?
Or saying that if you front up to your registering authority with a new car with front SRS airbags, compliant with all the ADR's, and the authority in that state says, "sorry, you can register that car in this state until you have side curtain airbags fitted", but that vehicle is perfectly legal and registerable in every other state...


Sorry for the hi-jack Surfin...

One thaught.

IF you have two axles on completely seperate suspension systems .... but those suspension systems are air bag bassed .... they can most certainly be load sharing ....... this is the basis of the "Road friendly" air bag suspension on the majority of new heavy trucks and trailers.

Its simply a matter of connecting the air bags on the same side togther.

I have a pending car trailer rebuild on the back burner ... I considered some sort of airbag system .... there where attractive points ....... BUT .... if there is no permenent air system on the tow vehicle or some sort of engine powered compressor mounted on the trailer ..... things get messy

On the matter of the suspension alone ....... the best option would be some sort of 3 or 5 link suspension system with the air bags either directly on top of the axle or located directly behind and in line with the chassis rail ...... I considered this could be achieved with suspension components drawn from a coil spring landcruiser or patrol ..... his would provide pre engineered components .... swingimng the arms outside the chassis rails would improve axle to tray clearance ........ ahh yeh but what a fiddle.


If you want a tray that drops flat to the ground, you are left with no choice but independednt suspension and another engineering chalenge ...... chasis regidity in a structure that is not a closed form.

serioulsy ..... if you want one of these lay flat trailers ..... its gona be a hell of a lot cheaper, easier and safer to buy one.

cheers