Corrugated roads.

Search. There was a very detailed and scientific article posted some time ago.

met a young babe many, many years ago who was doing research into this for a thesis......the end result was lots of pages and diags and graphs and photos and.......too fast for the condition of the surface and tyre inflation and spring/rebound and.......in the end I think I just had a beer and accepted that's the way it is - now if we could just people to vary their tyre pressures life may be just a little bit smoother on the dirt roads...rgds

The general consensus seems to say that car suspension travel causes them. I always thought the wind had a hand in it...you get ripples in sand dunes. They call them washboard roads in the US.

Corrugations are a natural occurrence on roads that don't have a solid stable base, tyre pressures, speed and suspension has very little to do with the severity in a sense but are the number one cause of it.

The way to fix it is don't drive on the road.

Even well designed bitumen road suffer from it, dirt roads are much more prone to it due to how they construct the underlying base, most governments and councils will not spend $10's of millions on digging out the soil and construction a proper base, they might do this in some small sections but not the whole road unless it is a priority with high traffic flow.... or someone else pays for it like a mining company.

To do something like the Canning would cost $100's of millions for no real financial or economical gain...... it's easier to send a grader through every 6-12 months at a cost of $200,000 per year.

Gday
Corrugations are caused by the' harmonic oscillation of the vehicles suspension'.

Hi Members - I blame GOD....just going overboard with the speed humps. Natures way of slowing everybody down. lol lol

This link will explain all (I think)Corregated roads

Ian,
many years ago I did some work on a station in the Kimberley. Every week someone going for a drive was told to drag an old railway sleeper sized piece of wood with some sheep wire behind it down to the main gate (7km). This spread the loose dirt and flattened the emerging corrugations before they became a problem.

When I had a turn I took a good close look at the corrugations and noticed the way in which the sand grains of different size had collected together and were forming the ridges. This is consistent with the physics article cited above. Also explains why you tend to get less severe corrugations in areas where the sand has fairly uniform particle size.

The worst ridges I have encountered were in Mongolia which when coupled with the potholes made life interesting.

All adds to the joy of remote travel.

Many years ago when I was doing a Diploma course at TAFE one of my Geology lecturers answering a question on this subject relied that a majority of corrugations result from the material and road base that are used to make the road, he also said that if the same material was used to make bitumen for a road it has been known to also form corrugations.

They also are worse on uphill slopes. One started they tend to increase the bounce and increase the corrugations even more. When outback roads are graded, the underlying corrugations are not cut out, so soon "bounce back". Going slow and low tyre pressures will slow the progress.

Motherhen

Isn't an up-hill slope the same as a down-hill slope - just depends on your compass point?

Corrugations occur whenever a load bearing wheel runs over a fluid surface. This even includes steel train tracks.

My theory is (cough) that the wheel pushes a bow wave of the road material ahead of it. At a point, the wheel then runs up over the accumulated bow wave and starts again.

The next wheel to come along accentuates the rippling and before long corrugations have been formed.

If the road surface is soft, such as the sandy roads of Central Oz, then the process occurs quickly. If the vehicle suspension is set up to bounce (over inflated tyres and hard shocks) the road is damaged more quickly. The tyre leaves the surface and when it hits the surface again it is spinning and chews away at the surface. Thats why corrugations are worse in acceleration and braking zones.

My solution to corrugations is to spread the load over a greater length of the road surface. This can be achieved by having a dual wheel bogey like setup, a caterpillar belt like attachment, or more simply by deflating the tyre sufficiently to give a long patch of road contact. This also means that a lot of the surface irregularity is absorbed by the tyre before it is transmitted through the wheel into the suspension, then the chassis, and finally the occupants teeth.

That solution requires big wheels and high profile tyres. If I were invited to design a bush tourer it would have wheels and tyres borrowed from a Unimog. The tyres would be run at around 10 psi.

That is my theory.

Why do sand deserts have sand dunes?