Corrugated Roads a natural phenomena???

Hi Quino,

One guy I enjoy listening and watching is Dr Karl Kruszelnicki. He has a webpage on the ABC's website and there's a 3 part article on corrugated roads. Makes for interesting reading.

Check it out here.

Of all the roads we travel on, the Shire road to our farm is the worst for corrugating. It is worst on the inclines at either end of the road. It gets graded twice a year, and it doesn't take long for those little ridges to start forming; first on the inclines. The faster you go, the more bounce to start the corrugations. Once they have started, they make you bounce more and increase rapidly. Washouts and stoney roads are far kinder on cars than this road. Well that's my observation anyway. Now i'll get back into the kitchen. Enjoy the rest of the weekend.

Motherhen

Dr Karl wrote a series of articles on this.

You can find the articles on the ABC web site in the science area.

Very interesting read. I think it has been linked in a previous post in the Archives of this forum.

Cheers
Muddy

I believe it is the rebound from the springs of the vehicles, shocks, tyre pressure and coil springs. As the spings hit a bump - pothole, it contracts and then expands at a rate that it hits the ground with a thump and condenses that piece of ground it hits. Thus starting another bump behind the first one, if the shock adsorbers are worn or just tired they can't stop the second rebound and the process continues!
well thats my theory anyway
If you drive on a sandy track behind a leaf sprung vehicle, the corrugations dont seem to be as bad as when you follow a coil sprung vehicle. Just an observation and a personal one at that.

Hi Quino

Check out post 1227 posted May 29th 2002 and other posts using "corrugations"

But is worth visiting again for an update on peoples ideas

Bill

Does it matter? The only solution to corrugations is not to drive on the roads.

Ofcourse if you go fast enough and start aquaplaning ,so to speak, on the top of the 'gations then you will not feel the bounce effect and your CD will not skip a tune.

There is not much you can do about it.

I guess I, like many others, have too, also wondered.

I do know one thing, they always seem worse at crappy stock grids, where vehicles have had to either slow down, or pick up the pace again.

Very interesting post!

Wolfie

I think they are caused by women drivers. hahah

I spent a happily alcoholic evening over dinner with Ron Moon a few months back - mostly discussing corrugation formation. That discussion became the subject of one of his recent Columns in 4X4 Australia.

The cause of the discussion was my mentioning that I spent two and a half years in Africa studying road surface conditions. I collected a huge amount of data and thought that I had found the probable cause/s - much as the good Dr Karl propounds - and that it had a lot to do with pneumatic tyres.

On my return however I was dismayed to find a report written in the later 1800s on the build-up of corrugations on South African bullock cart tracks. Further research showed that corrugations even form on the vertical steel guides of lifts!

I have come to belief that a corrugated surface is the natural condition of a dirt road, but that there are many and varied triggering causes.

To some extent they may even be wind-caused sand dunes on a smaller scale.

As with Karl I became aware of a few tracks in non-windy bits of the Sahara that are travelled only by huge 100-tonne plus trucks - these seem to stay corrugation free - here I believe the very high ground loading and huge footprint of the tyres does a steamroller act.

What is very clear though is that on many tracks the build-up is speeded up by drivers braking and accelerating before and after bends. It is interesting that this occurrs more on tracks used by tourists than similar tracks with roughly the same amount of local traffic.

So some of youse guys appear to be doing it to yourselves!
Collyn Rivers

If wind and rain were the cause, then everywhere would be corrugated, not just the roads.

They are caused by people selfishly towing trailers!

Actually, my theory is that when a wheel rolls on a surface it creates a bow wave in front of it. This is significant on soft surfaces like dirt roads, less on bitumen, and very small on a steel train track. When the bow wave is big enough the wheel rolls up and over the crest and starts the process again. The next wheel to roll along the same track does the same thing, making the crest a little higher. Under braking or acceleration the wheel applies a shearing force to the surface of the track, loosening material (dirt) and increasing the size of the bow wave. Highly inflated tyres mean a smaller area of contact with the road and the resulting increased pressure loosens more dirt. Same with heavy loads. Suspension bounce also increases damage to the troughs (the vehicle is only in contact with the ground for a fraction of the time so the pressure is greater, and the forward motive force can only act for a fraction of the time so a small wheel spin occurs each time the wheel hits the road which breaks up the surface).

So if my theory is right, there would be fewer corrugations if people travelled slower, let their tyres down, had lighter loads on each wheel (use a trailer ;-) and braked and accelerated gently.

Same way braking bumps are formed on a motoX track or dirt track, they are formed by vehicles of different weights and speeds traveling the road, Karl believes it so i do too.

Its a fascinating discussion. What I'm amazed about is that there is still no defining answer. Plenty of theories and a few experiments that provide some clues but not all the answers.

I too have wondered how they form.

Personally I can't agree that suspension, or tyre pressure a a major factor as every vehicle is different enough to prevent a uniform outcome. It must have more to do with the road surface than anything else because that is the constant in any particular context.

Vehicle setups seem to only contribute to the speed with which they form.

I thought Dr Karl's first article was the most convincing as it involved a controlled experiment.

But it seems we still don't know for sure.

At least it will continue to provide subject matter for the camp fire and an alternative to the Toyota/Nissan, Hiclone, Tyre Choice discussions.

Gaz