Single axle v twin axles on caravans

bgt · Guru

Single axle v twin axles on caravans

Whenarewethere · Guru

Only single axle caravans care allowed into Purnululu NP.

Possum3 · Guru

Once a caravan exceeds 18 ft (5.5 M) it is mandated to have two axles.
Quantity of axles is less important than type of suspension 1. Slipper Leaf sprung. 2. Double Eye Leaf sprung 3. Rocker Leaf sprung 4. Rocker Roller Leaf sprung 5. Independent Suspension 6. Air Bag suspension. All types with or without various shock absorber configurations.
Personal preference is Double Eye Rocker Leaf - more robust than any of the others & will better handle gravel and corrugated roads - easier to maintain, easier to make on road repairs in remote areas - doesn't require wheel alignment repairs as much as independent suspensions.

Aus-Kiwi · Guru

Single would would be better put in real rough areas where suspension travel ? Is required ! Depends where your going off the track so much ? Yes the rocker leaf would be my preference !! larger Wheel size gives you higher axle clearance !!

bgt · Guru

No real off road intended. Just the ability to get up a rough graded road to a campsite.

Aus-Kiwi · Guru

Twin then, of good design .

oldbloke · Guru

Twin axle, leaf springs. You will be surprised where they will go with care. Ours if fairly low clearance and to date no issues.
More clearance will raise the centre of gravity so its a compromise. ...As usual.

Buzz Lightbulb · Guru

Single axil would be more fuel efficient because there's less drag.

Greg 1 · Guru

Personally I am not keen on single axle much passed 16 feet. I have owned both single and tandem and on a van of the size you are contemplating it would be tandem. I have always had the roller rocker style suspension on my tandem vans and have travelled all over this country at one time or another without issue. My current van is not particularly high off the ground. As far as Purnulu National Park is concerned, some of the creek bed crossings are quite steep and fairly narrow so you would not want to take a van more than 15 to 16 foot in there and it would need reasonable ground clearance. But I wouldn't take a van in there in the first place. There is a caravan park about a k in off the highway which is a good base. The road in is quite rough with large corrugations and rocky. You could get a two wheel drive in there if it had the ground clearance but it is a bone shaker. 50 ks took us about 2 hours each way in just the car to give you some idea. My UHF aerial undid itself as I watched it it was so rough. Got pulled up just as it parted company with the vehicle. It has never before or since done that trick on all the roads we have been on. 60kph was speeding on that road and you need to let the tyres down. 20kph over some sections was not uncommon. If you set off early, you can have a pretty good look around out there and get back to the van by dark.

darjak · Senior Member

Simplicity independent load share either coil or inverted spring.
I personally wouldnt have anything with axles.

Darjak

Warren-Pat_01 · Guru

Hi but,
I have a 17'6" single axled caravan that follows the car well BUT there is no way I'd take anything but a Trac camper trailer or equivalent into Jonathon's Purnululu NP (thankfully there is a camping ground at the entrance where caravans, etc can be left. If you want to see that park, go by helicopter- it's far safer & smoother!!

Yes, I'd like to have the Coronal equivalent of our Jayco - purely because of the Simplicity suspension.

Peter_n_Margaret · Guru

Possum3 wrote:
Once a caravan exceeds 18 ft (5.5 M) it is mandated to have two axles.

Totally false.

Cheers,

Peter

Whenarewethere · Guru

Warren-Pat_01 wrote:
Hi but,
I have a 17'6" single axled caravan that follows the car well BUT there is no way I'd take anything but a Trac camper trailer or equivalent into Jonathon's Purnululu NP (thankfully there is a camping ground at the entrance where caravans, etc can be left. If you want to see that park, go by helicopter- it's far safer & smoother!!

Yes, I'd like to have the Coronal equivalent of our Jayco - purely because of the Simplicity suspension.

September 2008 three dead. Overloaded & weather too hot for engine.

October 2011 four dead. Flew too low to photograph & crashed.

Driving in & out of the NP, people are asked to drive at 50kph, but they don't & they don't let their tyres down either. About 8 went past us while we were airing up & down at the entrance.

That's why they wreck their vehicles & themselves, even more so because it seems that people are running tyre pressure much higher that the sticker on the car.

My car says 32psi & I drop to 24psi. Compared to someone who runs at 40psi & doesn't bother to let air out & people are surprised their cars get wrecked.

Wanda · Guru

Peter_n_Margaret wrote:
Possum3 wrote:
Once a caravan exceeds 18 ft (5.5 M) it is mandated to have two axles.

Totally false.
Cheers,
Peter

Have to agree with Peter, we have seen many 18'6" sigle axle vans, I think its more about weights. I must admit years ago you rarely saw anything above that in single axle they were all tandem, but technology seems to have changed this

Ian

Possum3 · Guru

rvbooks.com.au/australian-rv-rules-and-regulations
1/3/2021 · Centre-axled trailers (legally known as pig trailers) must not exceed 12.5 metres overall. The maximum distance from tow hitch to centre-line of the axle/s must not exceed 8.5 metres. The rear overhang must not exceed the lesser of 3.7 metres, or the length of the load-carrying area (or body) ahead of the rear overhang line.

Peter_n_Margaret · Guru

Possum3 wrote:
rvbooks.com.au/australian-rv-rules-and-regulations
1/3/2021 · Centre-axled trailers (legally known as pig trailers) must not exceed 12.5 metres overall. The maximum distance from tow hitch to centre-line of the axle/s must not exceed 8.5 metres. The rear overhang must not exceed the lesser of 3.7 metres, or the length of the load-carrying area (or body) ahead of the rear overhang line.

If it is correct, that says that you can have a single axle trailer 12.3m long (including hitch). Nothing about tandem axles (which are considered single for dimensional purposes).

Then glider trailers are exempt from the 3.7m overhang rule (irrespective of whether they are single or tandem axle).

"Light 'pig' trailers" can be up to 4.45T GTM. They can have any number of axles including one.

Cheers,

Peter

Wanda · Guru

Possum3 wrote:
rvbooks.com.au/australian-rv-rules-and-regulations
1/3/2021 · Centre-axled trailers (legally known as pig trailers) must not exceed 12.5 metres overall. The maximum distance from tow hitch to centre-line of the axle/s must not exceed 8.5 metres. The rear overhang must not exceed the lesser of 3.7 metres, or the length of the load-carrying area (or body) ahead of the rear overhang line.

Don't know what that all means but there are PLENTY of 18'6" single axle vans out there!

Maybe they fall in line with that regulation, where ever its come from!!

Ian

Tony108 · Member

It is not down to the length of the caravan, it is down to the weight of the caravan. Mine is a single axle 21', not including drawbar but only weighs 1500kg and is perfectly legal.

Peter_n_Margaret · Guru

I have a spare rear axle from an OKA.
I intend to modify it to build a "light" trailer with it.
It will have disc brakes (electric over hydraulic) and the same wheels and tyres as the OKA.
It could have an ATM of 3.5T on a single axle.
I could just as easily and legally make a caravan the same way. Length is no criteria.
Cheers,
Peter

yobarr · Guru

Tony108 wrote:
It is not down to the length of the caravan, it is down to the weight of the caravan. Mine is a single axle 21', not including drawbar but only weighs 1500kg and is perfectly legal.

Interesting.Bit of research shows that tare is 1350kg,leaving 150kg for EVERYTHING.My beer weighs more than that,so I wonder what plans you have for this caravan? Are you planning only day trips? But you're right about weight versus length, and,as Peter has pointed out,large weights can be carried on an appropriate single axle. However,two axles would likely make the van less affected by side winds etc because of extra rubber on the road.It is my belief that the turbulence caused by any one of the 4-trailer roadtrains regularly seen on outback roads would send a 1500kg 21' single axle van base over apex (R Sup) quick smart.Be very careful.Cheers

P.S This is another set of figures I found,again showing only 150kg load.

-- Edited by yobarr on Saturday 13th of November 2021 09:36:18 PM

Long Weekend · Guru

Now that's what I call a road train!

Luckily, I have never seen one on the open road so far. Just thinking about overtaking one gives me nightmares.

Murray

Peter_n_Margaret · Guru

58 wheeler on the Strzelecki Track.
youtu.be/XyqmLd_GowQ
Cheers,
Peter

Possum3 · Guru

Around the same area in Lyndhurst SA, in 1995 we passed a seven trailer/wagon cattle truck - Had to put the old Pajero out in the scrub a bit to get by - that thing was flying along about 60 -70 Kph.

I had seen the big trains out in the paddocks before, never on the roads.

The four trailer ore road-trains make up about half the traffic out Marble Bar way and kill hundreds of prime cattle every year, they travel day and night non-stop.

yobarr · Guru

Possum3 wrote:
Around the same area in Lyndhurst SA, in 1995 we passed a seven trailer/wagon cattle truck - Had to put the old Pajero out in the scrub a bit to get by - that thing was flying along about 60 -70 Kph.

I had seen the big trains out in the paddocks before, never on the roads.

The four trailer ore road-trains make up about half the traffic out Marble Bar way and kill hundreds of prime cattle every year, they travel day and night non-stop.

You're right,Possum.They're 60 metres long,have 110 wheels,and weigh 205 ton wheen loaded.The ring feeders are over the middle axle of the dolly,rather than at the rear,making the whole rig more stable,with the trailers tracking perfectly.They're only 615HP,with 18 speedboxes,but sit steadily on 90kmh once they're rolling.Supposed to swap drivers after a 12 hour shift to keep them running 24/7,but if there is a hold-up somewhere, maybe puncture,loader problem,unloading problem (they're side tippers) or something else,the new driver can be waiting 3-4 hours to start his shift! As for overtaking,the usual couple of flashes of the right blinker is used when it is safe to overtake.Cheers

KJB · Guru

yobarr wrote:
Possum3 wrote:
Around the same area in Lyndhurst SA, in 1995 we passed a seven trailer/wagon cattle truck - Had to put the old Pajero out in the scrub a bit to get by - that thing was flying along about 60 -70 Kph.

I had seen the big trains out in the paddocks before, never on the roads.

The four trailer ore road-trains make up about half the traffic out Marble Bar way and kill hundreds of prime cattle every year, they travel day and night non-stop.
You're right,Possum.They're 60 metres long,have 110 wheels,and weigh 205 ton wheen loaded.The ring feeders are over the middle axle of the dolly,rather than at the rear,making the whole rig more stable,with the trailers tracking perfectly.They're only 615HP,with 18 speedboxes,but sit steadily on 90kmh once they're rolling.Supposed to swap drivers after a 12 hour shift to keep them running 24/7,but if there is a hold-up somewhere, maybe puncture,loader problem,unloading problem (they're side tippers) or something else,the new driver can be waiting 3-4 hours to start his shift! As for overtaking,the usual couple of flashes of the right blinker is used when it is safe to overtake.Cheers

Nice clear, explanatory Pics.. KB

KJB · Guru

Long Weekend wrote:
Now that's what I call a road train!

Luckily, I have never seen one on the open road so far. Just thinking about overtaking one gives me nightmares.

Murray

No need to overtake - just sit back a distance and enjoy the trip........ KB

Wanda · Guru

Peter_n_Margaret wrote:
Possum3 wrote:
Once a caravan exceeds 18 ft (5.5 M) it is mandated to have two axles.

Totally false.
Cheers,
Peter

Yep again, thats what I thought, I have seen many 18+ft caravans. Certainly used to be rare for anything over 18ft but that seems to have changed over the years, I guess all to do with suspension ratings

Ian

Tony108 · Member

yobarr wrote:
Tony108 wrote:
It is not down to the length of the caravan, it is down to the weight of the caravan. Mine is a single axle 21', not including drawbar but only weighs 1500kg and is perfectly legal.
Interesting.Bit of research shows that tare is 1350kg,leaving 150kg for EVERYTHING.My beer weighs more than that,so I wonder what plans you have for this caravan? Are you planning only day trips? But you're right about weight versus length, and,as Peter has pointed out,large weights can be carried on an appropriate single axle. However,two axles would likely make the van less affected by side winds etc because of extra rubber on the road.It is my belief that the turbulence caused by any one of the 4-trailer roadtrains regularly seen on outback roads would send a 1500kg 21' single axle van base over apex (R Sup) quick smart.Be very careful.Cheers
P.S This is another set of figures I found,again showing only 150kg load.

Mine has a tare of 1304 kg and has been uprated to 1500 kg. With the van loaded with all necessary equipment etc I have 35kg for food and clothes. I am a single traveler so i don't have to carry all the mandatory items that a partner would need. Its all been weighed and calculated on a spreadsheet. I needed a low weight van because I like my car, so the van has to work around the car. All other items will be carried by the car. In about 2 years When I retire I plan doing the lap or part of. I know i cant carry as much as a lot of you but I reason that the more you can carry the more you will carry. I am pretty confident I will have all I need. I have had road-trains pass me and the whole rig handles nice, its down to how its all loaded, if its loaded correctly, van and car, it shouldn't be a problem.

-- Edited by yobarr on Saturday 13th of November 2021 09:36:18 PM

-- Edited by Tony108 on Sunday 14th of November 2021 03:51:15 PM

yobarr · Guru

Tony108 wrote:
yobarr wrote:
Tony108 wrote:
It is not down to the length of the caravan, it is down to the weight of the caravan. Mine is a single axle 21', not including drawbar but only weighs 1500kg and is perfectly legal.
Interesting.Bit of research shows that tare is 1350kg,leaving 150kg for EVERYTHING.My beer weighs more than that,so I wonder what plans you have for this caravan? Are you planning only day trips? But you're right about weight versus length, and,as Peter has pointed out,large weights can be carried on an appropriate single axle. However,two axles would likely make the van less affected by side winds etc because of extra rubber on the road.It is my belief that the turbulence caused by any one of the 4-trailer roadtrains regularly seen on outback roads would send a 1500kg 21' single axle van base over apex (R Sup) quick smart.Be very careful.Cheers
P.S This is another set of figures I found,again showing only 150kg load.

Mine has a tare of 1304 kg and has been uprated to 1500 kg. With the van loaded with all necessary equipment etc I have 35kg for food and clothes. I am a single traveler so i don't have to carry all the mandatory items that a partner would need. Its all been weighed and calculated on a spreadsheet. I needed a low weight van because I like my car, so the van has to work around the car. All other items will be carried by the car. In about 2 years When I retire I plan doing the lap or part of. I know i cant carry as much as a lot of you but I reason that the more you can carry the more you will carry. I am pretty confident I will have all I need. I have had road-trains pass me and the whole rig handles nice, its down to how its all loaded, if its loaded correctly, van and car, it shouldn't be a problem.
Looks like you've got it sorted Tony! Just be aware that effective load carrying capacity of the Jag is only about 600kg,and maximum towball weight is only 175kg.The other thing that you will need to keep a close eye on is the weight on the car's rear axle,as that axle has a low carrying capacity of only 1420kg.Beware! Good to see you taking an active interest in being safe,but I still reckon a 1500kg single axle van that is 21' long will get blown around something wicked,but at least your car is more than 50% heavier than your van.Well done. Cheers

-- Edited by yobarr on Sunday 14th of November 2021 04:18:51 PM

yobarr · Guru

KJB wrote:
Nice clear, explanatory Pics.. KB

Thanks Kerry.I always do my goodest! (Sic) Cheers