Corrugations

Great article, Phil.

The only thoughts that I can offer pretty much reflect the title of your article - Bloody Corrugations! LOL

I did a little research and found that Mather's findings were published in the Jan 1963 edition of Scientific American. You will have to pay a small fee to get the article.

I found some other links:
Dr Karl. Other Dr Karl writings here and here.
Some search results

Cheers

It isn’t weight related but suspension and relatively small wheel size related which causes corrugations. Softer tyre pressures minimizes the hammering and compacting ground displacement which causes corrugations. Not sure some of the article items are related to corrugations.
Old horse and cart steel bands didn't really create corrugations and it is far better to have your foot under a tyre than a cart wheel, ie pressure is more under cart thin band.
If you speed over the ground, the effective pressure delivered to the ground is less. Only under some areas do rally cars cause undulations where they dig in.
Like high airspeed in a venturi. Slower speed, means the tyre has time to squirm and as it is forced against the road surface it effectively machines some off the road surface due to tyre that tyre squirm which is happening when maximum pressure of contact is occuring. Bald tyres would have far less effect because of no tread squirm. New, big lug tyres which squirm under pressure means more development of corrugations as a result. Tyres, as we all know, do flick out stones from the tread, it must be happening at a smaller level under the moving tread. This is made more so with the action of suspension as it's rebound energy is delivered onto the road surface. Less speed, less energy under tread to be dissipated.
Most suspensions widthdraw the tyre rearwards under compression and therefore forward and harder hitting against any slight rise in surface if it coincides with the down movement.
HQ Holdens had a front suspension which, when compressed took the tyre foward be design. They soaked up bumps and corrugations better than most. I drove on eon back roads for thousands of KMs. It worked.
Less tyre pressure means less cause speed of driving and not as severe development of corrugations. Might be more comfort on the road but the tyre is certainly squirming as it is the primary suspension of a vehicle so may not be reducing the formation of corrugations as people think it does. Less force to the road is the thing which will have the positive effect.

We were talking corrugatioms around the fire one night on the Gunbarrel after a tough day and an old farmer in the group smiled and said “ I never had any corrigations on my farm tracks until my sons started driving.”
That would have been back in the days before any discussion of tyre pressures so he was pointing to the speed factor.
Glad to see the multiple tracks around Well 33 got a mention in your article. I was out that way a decade ago ... it’s a shocking memory. I may have cause to go back next year, not something to look forward to.

Cheers

A good read Phil, wishing you and yours a Merry Christmas,

Agree, "Bloody Corrugations", watched an episode of Outback Truckers and on one particularly nasty stretch of corrugations, they rigged up the spares on chains between the tug and trailer, this flattened out the corrugations some what to allow a smoother ride for the sensitive load. I have often thought about dragging a short length of chain behind both rear wheels and see if it works to break/flatten the corrugations. Will try it one day. Till then. lower tyre pressures and try and find a comfortable speed and curse those that have gone before and not lowered tyre pressures or speed.

Trains cause corrugations on railway lines.....
http://railmeasurement.com/assets/docs/090709-JRRT-corrugation.pdf
Cheers,
Peter
OKA196 motorhome

Phil, great read, but one comment I would like to make. Your statement about corners having no corrugations, sorry mate, some of the worst corrugations I have experienced are on the corners, even finding them on otherwise corrugation free tracks. I think many will recall skating around corners after suddenly finding oneself on bad corrugations in a corner. Good luck with your thesis.

I agree with the speed and tyre pressures being causes.
But also acceleration, and related to that is people not engaging 4 wheel drive to limit wheel slip.
When the wheels are slightly spinning they create the lumps
I was behind a vehicle in the Simpson that I heard on the radio was in 2wd , I could see it spinning up on the woops that were already there, making them worse
Has anyone else observed this?
Wouldn’t it be great to be able to control , say 50 vehicles along a bit of the CSR as an experiment. with pressures down , not accelerating heavily, just driving more gently,etc. I believe it would smooth out .
Same as if everyone drove sand dunes in the best technique possible they wouldn’t be whooped out either.

Ah now I see some other comments about acceleration.

I know the army did a lot of research on corrugations. I don’t know if they ever published anything. I worked with an ex-major who ran me through it once. As I recall they didn’t come up with any silver bullets.

Ahhh, just the thought of them makes me want to be back out there Phil.

Thanks for bringing the 'curse of the outback traveler' back to the forefront of my mind lol.








All the best for Xmas and the New Year mate. Be safe, be happy.

Mick and Vik.

Here is an interesting study... Maybe there is a clue here?
On the Gary Junction Road in 2008 there were very few corrugations, but this small crest in the road was a notable exception. On either side, the road was free of corrugations.
Most of the traffic was locals who tend to travel quite fast in 2WD vehicles. I would guess that as they came over this small crest, the wheel spin would increase somewhat?
The corrugations that formed had a quite short wave length.


ps... this is inbetween Kiwirrikurra and Gary Junction.
Cheers,
Peter
OKA196 motorhome

Thanks Peter for that, most of us would probably drive over these and not notice them.
More info to add to the potential causes of Cs.

Dragging a log behind a truck to flatten out the corrugated road.

This log was on display at Tjukayirla Road House for years. It was used by the mail truck going to Warburton etc to flatten the corros. Note flattened bottom of log.

Scary as it is to wade into this debate I can only add my observations and experiences from growing up on farms and spending a lot of time on isolated tracks both sandy and gravelly and at times being the sole user of said tracks. Then getting frustrated that 2 or 3 vehicles have used the track once or twice and trashed it.
Being aware of what your tyres are doing is critical. This is very hard in modern comfortable vehicles because you become so isolated from the surface you are driving on - comfort vs contact with the outside, Driving rough old utes, tractors forklifts and trucks around on mud, sand and dirt gives you a nouse about what needs to happen beneath your wheels in order for you to keep moving and not stuff up your tracks!! You just cant do that these days in airconditioned silence running a 200kW (plus) V6/V8 with armchair worthy suspension....!!!

There has been good info so far about wheelbase, soil, etc etc so just some of my own thoughts...

To prevent or minimise corrugations
1/ The vehicle needs to be well balanced - for example an empty wagon vs empty trayback will form less corrugations with all else being equal due to the distribution of weight over the front and rear wheels - wether in 4wd or 2wd. (Uneven weight between the front and rear causes a tendency for wheel slip on the surface especially when cresting or cornering).

2/ Anything that limits wheel slip makes the most difference - using 4wd for a start - (duh), Limited slip diffs make a huge difference, difflocks on the front - especially unlockers (detroit/lokkas) help even more. (Especially on curves and winding tracks as fixed lockers will cause one wheel to turn more than the other causing tyre slip on one side and digging little holes.

3/ Open diff traybacks/utes/wagons seem to create the most havoc as they get a rock up as they gain and lose traction on opposing wheels. Rocking side to side and axle tramp are no no's.

4/ Tyre pressure!! - Lots already said about this but some conflicting forces at work but as mentioned earlier the main factor is lower pressures to improve traction and limit wheel slip/spin. Modern vehicles with lower profile tyres and carrying heavy loads cannot afford to reduce tyre pressure much anyway so again - why not blame city vehicles driving on bush roads

5/ Acceleration/Driving technique - a no brainer here but how many dont consider it? excessive acceleration allows for wheel slip - lift the foot when heading up inclines take it easy taking off and maintaining speed.
When towing heavy loads you can take a few extra seconds to crest a rise.


All this does not mean that if the perfectly configured and carefully driven vehicle drove over the same surface at the same speed it would not create corrugations due to tyre dynamics and imprefections on the road surface but there is a lot a good driver can do to minimise them.

Of course most dont care about who is following them anyway.

Ive probably forgotted some other observations but it is sunday morning and there are better things going on outside...


My two bobs worth - from personal experience ...45 odd years worth at that

Hi Phil, we met on the CSH in September. See pic for possibly the worst corros on the entire CSH north of Cooper Hills bore. A quick five points for my 2 bobs worth.
1. The bleeding obvious is lower pressures. If you can hear a flup-flup-flup then the rubber is working to relieve the shocks and keep them cooler. Tyres are easier to replace than shocks.
2. You have to get up to speed to match the wavelength of the ridges. Then the flupping is a nice hum and the ride is as smooth as it's going to get.
3. Drive -with caution - on the wrong side of the road so as to go up the less steep sides of the ridges . Your ride will be smoother.
4. Keep left side wheels on smoother edge of track while the right side gets hammered by corros. Then swap so right side is on smooth edge and left side takes the punishment. This gives shocks a chance to cool.
5. Allow SWMBO to get you to stop and take lots of pix. Again, more cooling time and a rest for your back. Cheers, Warrie

Hi Phil, the attached link provides some pretty good info on the causes of corrugations.
http://www.abc.net.au/science/k2/trek/4wd/Overcor2.htm
Regards, Gary M.

The major cause of corrugations is an inadequate level of clay binder in the road base.
You can build roads using anywhere between 15% and 85% of either clay or sandy material.
That is, you can use between 15% sand and 85% clay, or between 85% sand and 15% clay.

Pebbles and small rocks assist in surface binding, along with the fine clay particles.
The problem is, a road built with 85% clay sets solid, and won't corrugate when dry - but it becomes greasy when wet.

On the other extreme end, a road surface built with 85% sand and 15% clay is great to drive on when wet - but it will corrugate when it dries, because there is an inadequate level of clay particles to bind the pebbles, rocks, and sand into a hard compacted surface.

As a grader and dozer driver, and road builder of more than 50 yrs experience, I can assure you the reason you run into corrugations on Outback roads is because they have never been formed up properly, nor built with the correct proportions of road base materials.

Outback roads and tracks are merely graded from the loose topsoils, that only rarely contain enough clay to bind properly.

In many areas, you can do a deep ditching cut with a grader, forming the roadside drain, and bring the deep clay to the surface to enable the clay to be mixed with the loose sand and topsoil.

By working the mixture of deep clay and sand and topsoil back and forth across the road formation, in a large windrow, you can generally produce a good blend of clay, sand, pebbles and rocks, to provide a very serviceable road surface - particularly if the soils are wet, by either recent precipitation, or by utilising a water truck.

An adequate level of moisture assists in compacting the fine particles of clay in tightly around the larger particles of sand and pebbles, thus providing a very firm surface that will resist corrugations.

Where the soil has deep levels of sand or topsoil, it is necessary to find an outside source of suitable road base material, that then has to be trucked in, to provide satisfactory material for the road surface.

As you can well envisage, this gets costly. Shire Councils spend multiple millions of dollars annually, in finding sources of gravel and other suitable road base materials, and then stockpiling them, and then loading and trucking them to the desired areas.

Naturally, if you can find a suitable source of good road base material fairly close to where it is required on the road, this cuts trucking costs.

Stockpiling road base requires both experience and skill. Many Shire employees have neither, and as a result, their choice of road base and execution of the stockpiling is poor.

Stockpiling involves bulldozing a slope, usually around between a metre and three metres deep in the selected road base material.

By doing this, the original soil profile is blended - because there is generally loose topsoil on top, then a layer of gravelly or pebbly material, and usually clay or sometimes even rock, below that.

By forming a slope of about 30 degrees, and dozing down that slope, to the level where the soil profile is becoming too clayey, or too rocky - and then lifting the dozer blade up to its full height, and pushing the blended materials up into a sizeable heap, that a front end loader can dig into, provides an excellent road base mix.

Many operators make the mistake of just pushing up soft gravelly soils, with inadequate levels of clay or rock.
This material is unsatisfactory for road base, and will corrugate rapidly, once laid.

I used to stockpile thousands and thousands of cubic metres of road base annually for local Shire Councils in the W.A. wheabelt.
You've more than likely driven on a lot of my selected gravel road base.

A very experienced old Shire foreman told me one time, that to produce good road base, "It's gotta be hard gravel. If it rips hard, it goes down hard".

What he was referring to, was that the naturally hard compacted gravel soils contained the necessary ingredients that ensured that they compacted and bound well, and provided low-maintenance gravel roads.

All that it takes to fix corrugations is the application of serious quantities of selected quality road base - and that road base has to have the correct proportions of sand, fine clay, and gravel or ironstone pebbles, or other suitable local small rocks, along with good levels of moisture, to ensure a well-bound and well-compacted mixture, that provides a solid surface very resistance to corrugating.

Cheers, Ron.

Good read, Phil, on an interesting, but also annoying occurrence.

Have seen plenty of corrugations over the years, big & rough, small but irritating. However, the most unusual I recall seeing, and driving on, were some on the Old Jim Jim road, between the Kakadu Highway and the old Cooinda Store.

These were spaced mostly about 4’ (1.2M)apart, varying in height up to 125mm, and often with an intermediate corrugation, though only on one side. Was somewhat unusual to drive on, in an 80 series, but we weren’t in a hurry.

Bob