Independant suspension myth by Bushtracker

Submitted: Saturday, Jan 13, 2018 at 11:51
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Come across this post by Mr Bushtracker himself. Interesting read.

I need to qualify a few things. You need to understand, that the knowledge I impart to you is not just my own, I have done this for 50 years, and have been in caravans since the 1960's, 4x4 work in Central America, North America, Africa, and Australia; but also and more importantly I have the added advantage of not only traveling all over Oz, but staying in contact with the accumulated testing of about 1000 of our Clients that report to me on how they are going in the Bush. What this means is continuous research and development is going on. I have met up with the Army on driving tests and driving schools out in the deserts around Birdsville, I do this full time and it has become my Life…. So have an open mind and hear us out.

On the necessity for an independent: The independent suspension adds that tunnel effect under the unit where a normal axle suspension would fall down in the ruts the tow vehicle was making and the axles would drag like a boat anchor bogging the tow vehicle immediately. Now, that is the most common reason that people think that the independent suspension in necessary-NOT TRUE. The independent suspension breaks up the killer of caravans- Harmonic Motion. That engineering term means the motion builds on itself, it doesn’t happen very often; but when the ruts and the spacing happen to coincide with the speed the bounces build on themselves and that shock destroys campers-caravans and the like. Harmonic Motion has destroyed countless of trailers, caravans, campers, broken-turned them upside down, on their side, smashed them up, broken hitches-walls-frames- and generally created havoc over the last 30-40 years. Almost every time I got bogged in the '80s on Frazer, in the bush, on every beach from the Daintree north to the Southern NSW coast, to black soil country in the west, to bulldust wet grease in the Outback, was because the axles on my trailer hit the ground like a plow when the wheels fell into the ruts of the tow vehicle. Axle suspension are not the go in the real Bush…

Now, don't be offended, but let me tell you of another myth that is being abandoned in the Outback. This next myth is that the trailer has to follow the track of the tow vehicle: Not true anywhere in Australia, Africa, or Europe, or where our vehicles are running except on soft beach dune sand where the tow vehicle packs it down a bit. No one I know likes driving on soft dry dune sand and avoids it like the plague. Bushtrackers are not built to track like the tow vehicle because it ruins the layout, and in unnecessary. We could build like that if you wanted, but not until you understand the disadvantages. Obviously you have to arrange your layout to suit such a track. But in almost all conditions except soft dune sand, it is better to track outside the disturbed soil that the tow vehicle is digging in the hard going.
With a beam axle suspension, it tends to dig in and plow dirt instead of rolling over it, while with our load-sharing suspension the load is transferred from front to rear and rear to front and it by nature rolls over the sand better instead of digging in.

We would only custom build them narrow if it was purpose built just for sand dunes. Narrow also means that they are more unstable and easier to turn over if you have to make a radical high speed move on the highway to avoid an accident.. This is the biggest disadvantage and why you cannot do it on a larger van. I personally will never have a narrow track towed trailer or caravan again having owned both, so maybe you need to think about that one a bit and discount the Myth.

Our vans will go more places than most 4 x 4 vehicles will go. The truth is that where one vehicle comes to grief, a better one would get through with a Bushtracker on the back. I know, I have tow eye loops on the back of my chassis of my Bushtracker and have towed many a poorly equipped 4 x 4 through areas where they have gotten bogged.

Our vans routinely go through bad areas, mud bogs, deserts, Cape, all over; and have skid plates on the back half of the chassis to drag them off ledges of false river channels and the like until the suspension hits the ground again. We are not building the look and style of Outback off-road vans like some, we are building the real thing. You at least need to understand what we are doing and more importantly why. Come to the Factory and see for yourself why we are Number One. Why we build the best, have the best engineering, the best equipment, the nicest interior finishes, and why we build more Off-road vans than anyone and are still Booked ahead as far as we are… And find out why our Customers are the ones that sell our vans for us…
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Reply By: Member - David M (SA) - Saturday, Jan 13, 2018 at 15:07

Saturday, Jan 13, 2018 at 15:07
Be interesting to know what he tows with.
Dave.
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Follow Up By: Member - Howard P (WA) - Saturday, Jan 13, 2018 at 15:10

Saturday, Jan 13, 2018 at 15:10
I think he tows with a Dodge Ram 2500?
Howard

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Reply By: CSeaJay - Saturday, Jan 13, 2018 at 15:14

Saturday, Jan 13, 2018 at 15:14
Sorry but I just disagree with the tracking. Indeed he said it himself that it is absolutely required for sof sand. Well, fact is that soft sand is a reality in this country if you go outback. Even if only crossing one dune or river bank just to get to the favourate camp, and even if that equates to 1% of the journey, it is imperative if that is the type of travelling that you do. You can travel 1000km of blacktop and dirt road to get to a place like Fraser Island or Ningaloo beach, but what is that worth if you cannot get over the fore-dunes to get to your idylic camp?
Even inland tracks like Anne Beadell is best done with a van that tracks behind the car.
The above comments appear to imply that the only reason they do not build them that way is because it interferes with the internal layout. Hardly a reason to dismiss the benefits of on-track towing
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Follow Up By: Member - mark D18 - Saturday, Jan 13, 2018 at 15:25

Saturday, Jan 13, 2018 at 15:25
CSeayJay

Not sure about his view on tracking as well . But his view on quality independent suspension is spot on .

Cheers
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Follow Up By: CSeaJay - Saturday, Jan 13, 2018 at 19:01

Saturday, Jan 13, 2018 at 19:01
Agreed, independant is king
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Follow Up By: Gronk - Saturday, Jan 13, 2018 at 20:51

Saturday, Jan 13, 2018 at 20:51
The only reference I could see regarding ind susp was that a beam axle would snag or drag against an obstacle. With a 20ft average size Bushtracker, generally you aren't going to go or get to a situation where the axle is going to be the limiting factor !!
95% of Bushtracker owners aren't or can't take them too far offroad....dirt roads are not offroad !!
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Follow Up By: Peter_n_Margaret - Saturday, Jan 13, 2018 at 21:07

Saturday, Jan 13, 2018 at 21:07
"Agreed, independant is king"

Why?

Cheers,
Peter
OKA196 motorhome
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Follow Up By: splits - Saturday, Jan 13, 2018 at 23:27

Saturday, Jan 13, 2018 at 23:27
With a 20ft average size Bushtracker, generally you aren't going to go or get to a situation where the axle is going to be the limiting factor !!
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It should never be the limiting factor. Chances are the tow car will have a live rear axle with the diff centre hanging down lower than the van axle. It should have cleared the way.
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Follow Up By: Gone Bush (WA) - Sunday, Jan 14, 2018 at 00:30

Sunday, Jan 14, 2018 at 00:30
Gronk,

"95% of Bushtracker owners aren't or can't take them too far offroad....dirt roads are not offroad !!"

What you said may be true, but it does not mean that BT's can not get really off road.





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Follow Up By: Allan B (Sunshine Coast) - Sunday, Jan 14, 2018 at 08:21

Sunday, Jan 14, 2018 at 08:21
.
That 3rd pic....... He'll need to use two hands.... pushing with only one hand will never do it.
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Follow Up By: Members - Bow & Nan - Sunday, Jan 14, 2018 at 09:54

Sunday, Jan 14, 2018 at 09:54
I find the biggest problem is low tree branches.
"Work interferes with living"

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Follow Up By: Gone Bush (WA) - Sunday, Jan 14, 2018 at 10:10

Sunday, Jan 14, 2018 at 10:10
That wasn't me, by the way.

This is me:
I'm glad I ain't too scared to be lazy
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Follow Up By: Peter_n_Margaret - Sunday, Jan 14, 2018 at 11:19

Sunday, Jan 14, 2018 at 11:19
I think the pics demonstrate very well why a single axle would perform better in those conditions. That dual axle is well beyond its load sharing capability, if indeed it had any.

Cheers,
Peter
OKA196 motorhome.
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Follow Up By: Members - Bow & Nan - Sunday, Jan 14, 2018 at 11:45

Sunday, Jan 14, 2018 at 11:45




Peter, the suspension works to keep the van level.
Not rock and roll like a single axle.
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Follow Up By: Frank P (NSW) - Sunday, Jan 14, 2018 at 12:48

Sunday, Jan 14, 2018 at 12:48
I think there's a fair chance that Bushtracker has chosen the best suspension for their market.

There's compromise in every design, and they've chosen theirs to suit.
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Follow Up By: Peter_n_Margaret - Sunday, Jan 14, 2018 at 13:02

Sunday, Jan 14, 2018 at 13:02
If a tandem axle is not 100% load sharing, then the weight transfer on and off the hitch and the rear of the tug will be enormous. That will be enough to limit the conditions that can be traversed.
None of that weight transfer occurs with a single axle.

Cheers,
Peter
OKA196 motorhome
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Reply By: noggins - Saturday, Jan 13, 2018 at 19:13

Saturday, Jan 13, 2018 at 19:13
One thing I can't find is any reference as to why there are no stabilisers fitted
Surely this would stop any roll from side to side ?



Ron
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Follow Up By: Shaker - Saturday, Jan 13, 2018 at 21:19

Saturday, Jan 13, 2018 at 21:19
The only factory camper that I know that has a sway bar is Conqueror.

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Follow Up By: Member - Phil G (SA) - Sunday, Jan 14, 2018 at 20:06

Sunday, Jan 14, 2018 at 20:06
Vehicle Components in Brisbane offer sway bars on their Cruisemaster
independant caravan suspensions, but I haven't seen the need
2012 Landcruiser 200 Altitude
2015 New Age MR16E Deluxe
2003 Tvan

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Reply By: splits - Saturday, Jan 13, 2018 at 23:18

Saturday, Jan 13, 2018 at 23:18
If independent is absolutely essential then surely they can come up with something better than a trailing arm. This bloke is talking about the bush but what about sealed roads at highway speeds? That is where all vans spend most of their time and continue to roll over with monotonous regularity. Trailing arms just help them to do it by rolling the whole thing from ground level not to mention tilting the wheels at the same angle as the van and reducing tyre contact with the road.

Apparently low speed extreme bush performance is more important than the best possible level of stability on highways and freeways..

Cars don't seem to fall apart because of these harmonics. Landcruiser utes that have been the kings of the Outback for as long as anyone can remember still have live axles front and rear. They were leaf sprung at both ends for decades. Maybe they worked properly because they were designed and developed over the usual six to seven year period at a cost of millions. As for caravans, well who knows.

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Follow Up By: Athol W1 - Sunday, Jan 14, 2018 at 08:26

Sunday, Jan 14, 2018 at 08:26
Splits

Harmonics can and do cause cars and trucks to fall apart. There are numerous known cases of this occurring over the years, and these can be in street vehicles or in racing vehicles/conditions.

One big difference between the Landcruiser with its beam axles and the caravan with 2 beam axles is that the caravan axles are normally mechanically interconnected for load sharing purposes. It is this mechanical interconnection that is responsible for a lot of the harmonics that can destroy the van, or parts thereof.

You may have noticed that he majority of heavy long distance transport are now using Air Bag suspension systems. These are known to the road authorities as ROAD FRIENDLY SUSPENSION. Whilst they may give a better ride for the fragile load being carried that better ride is because they have eliminated some or all of the harmonics that occur with the mechanical load sharing system They are known as road friendly due to the lack of the harmonics from the mechanical suspension resulting in less damage being done to the road surface.

As for your comments on the TRAILING ARM systems, I would much rather have a trailing arm independent suspension system to the 'swinging arm' style (commonly seen on the Coromal brand of caravan), but I would also prefer the swinging arm system to the beam axle and rocker that is used by most of the lower end manufacturers.

I have towed vans with each of the 3 types of suspension, my current van is a Jayco Silverline with their trailing arm, coil and shock absorbers.

Regards
Athol
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Follow Up By: Member - Andrew & Jen - Sunday, Jan 14, 2018 at 09:44

Sunday, Jan 14, 2018 at 09:44
Splits, have you ever seen the suspension on a Bushtracker?

The reason I ask is that I suspect you are thinking of a "normal" trailing arm suspension setup.

The Bushtracker (the older ones at least) have a Simplicity setup. The newer ones have a similar suspension manufactured in Qld near the Bushtracker factory.

A massive cross-member has a leading arm and a trailing arm fitted to each side, with a large leaf spring between the two arms and secured in the middle under the cross-member. This gives a firm ride with minimal side rocking and yet is load sharing and minimises vertical movement over minor undulations.

I have towed our 18' Bushtracker tens of thousands of kms in all mainland states and on all types of surfaces from bitumen to bush tracks on stations, including out of the way and off any track camping spots, all with no issues.

Towed with a suitable vehicle matched to the van (GVM, wheel base and GCM), it tracks on the road like it is on rails, even when meeting quad road trains at cruising speed and in cross winds.

Cheers
Andrew

PS I also own a Tvan with trailing arm suspension, This also tracks well and it's ability to handle all types of terrain while maintaining a smooth ride is well established.
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Follow Up By: Members - Bow & Nan - Sunday, Jan 14, 2018 at 09:49

Sunday, Jan 14, 2018 at 09:49
Athol, our new Bushtracker has independent, trailing arm,self leveling air suspension.
"Work interferes with living"

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Follow Up By: Athol W1 - Sunday, Jan 14, 2018 at 10:29

Sunday, Jan 14, 2018 at 10:29
Bow & Nan
Your Bushtracker would have arguably the best suspension (in principle at least) that is available for both on and off road use. As it is independent and air then, if multiple axles, would be load sharing via the air line connection. This air connection between axles removes the harmonics that are generated when there is any form of mechanical connection between the axles, including with the Simplicity suspension. Your van and its contents should ride very well and suffer little damage from road shocks.

I have recently noted that the new Jayco Silverline caravans are now also available with their version of trailing arms with air springs, replacing the steel coils and Aeon rubber blocks that are in my van, and this is available with their ON road, or Touring, van and is also height adjustable for when the occasion demands.

Regards
Athol
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Follow Up By: splits - Sunday, Jan 14, 2018 at 13:20

Sunday, Jan 14, 2018 at 13:20
Cheers
Andrew
PS I also own a Tvan with trailing arm suspension, This also tracks well and it's ability to handle all types of terrain while maintaining a smooth ride is well established.
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I would prefer that any day to a trailing arm or the swinging arm design that pivots sideways from near the centre of the chassis.

It is cornering at speed on highways or sudden swerves that concern me.

Straight trailing arms, not semi trailing arms, lean the wheels over with the van and their roll centre is at ground level. That is not acceptable with the level of suspension technology that is available today.

This link explains semi trailing arms. They change wheel angles to assist with stability. Trailing arms don't.SEMI TRAILING

Why don't van manufacturers use this design? Maybe it would involve too much expensive research and development to get it right for each van. At the moment there may not be any pressure on them to go down that path. That may change though due to the rate van accidents are increasing

The MC2 design in your Tvan is not your typical trailing arm. It does change wheels angles in relation to the trailer body and I doubt if its roll centre is at ground level..

Its long axles pivot from the opposite side of the chassis. From the rear they look like a live axle car with two panhard bars with the middle of the axle missing
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The roll centre on a panhard bar equipped car is where the centre line of the bar crosses the centre line of the car. That puts the roll centre well above ground level and maybe even slightly higher than a beam axle leaf spring design. That would make a major contribution to the trailer's stability.

There is a lot more to that design than just long up and down wheel travel.
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Follow Up By: Shaker - Sunday, Jan 14, 2018 at 18:49

Sunday, Jan 14, 2018 at 18:49
Vista RV Crossover have taken the MC2 concept a step further, by adding an extra link they have eradicated the bump steer & increased the wheel travel.


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Follow Up By: splits - Sunday, Jan 14, 2018 at 23:06

Sunday, Jan 14, 2018 at 23:06
Vista RV Crossover have taken the MC2 concept a step further, by adding an extra link they have eradicated the bump steer & increased the wheel travel.
---------------------------------------------------

That does not surprise me.Suspension design has been improving steadily for about the last eighty years and research into it will never stop..It is a pity it is not progressing as well as it should be with many caravan builders.
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Follow Up By: Blown4by - Monday, Jan 15, 2018 at 23:08

Monday, Jan 15, 2018 at 23:08
AtholW1 The jury is still out re air bags on heavy commercial vehicles being a 'road friendly suspension' and transport/road authorities in many jurisdictions are re-evaluating their thinking on this. Yes the air suspension gives a better ride quality and affords better protection to the load whether it be livestock or fragile goods. However if you drive behind such a vehicle you will see the air suspension working overtime to cope with the undulations so common on our sealed road surfaces and all that absorbed force is transmitted back in to the road surface hence the resultant damage. Also there have been engineering studies done to investigate why heavy vehicle combinations with air suspension on all axle groups wander all over the road and why inexplicably instances have occurred with professional drivers of rigs finding themselves on the wrong side of the road or at least not in the position on the road where they intended the rig to be. To counteract this, what is very commonplace now in the heavy commercial vehicle body building industry is a dog trailer with leaf springs at the front and air bags at the rear to try to counteract the 'self-steering' effect that is induced by the lateral movement of the drawbar when the trailer 'rocks and rolls' on its air bags.
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Reply By: Members - Bow & Nan - Sunday, Jan 14, 2018 at 10:06

Sunday, Jan 14, 2018 at 10:06
Bushtracker have three different types of suspension.

A heavy version of Simplicity suspension.
Trailing arm coil suspension.
Trailing arm, self leveling air suspension
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Reply By: Crusier 91 - Sunday, Jan 14, 2018 at 14:32

Sunday, Jan 14, 2018 at 14:32
Bushtracker
Bushtracker product testing (air bag suspension)


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Follow Up By: Crusier 91 - Sunday, Jan 14, 2018 at 14:42

Sunday, Jan 14, 2018 at 14:42
Bushtracker through the sand hills
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Follow Up By: Members - Bow & Nan - Sunday, Jan 14, 2018 at 15:44

Sunday, Jan 14, 2018 at 15:44
Not the air suspension that they now use.
They now use trailing arm not leading arm.
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