Thread: How do corrugations form?

I cheated and searched on-line - found lots of info...

road corrugations cause - Google Search

Originally Posted by Quigley

I've often thought about corrugations when driving on them, and wondered how and why they form.
There must be an explanation.
The more you think about it, the harder it is to get to a theory that explains it.
Any answers?

Well you see there are these things called Pixies and mini excavators on night shift............................................. ......................................

Corrugations are a sign of energy being transferred from one medium to another, the same as wind on water creates waves. The size of corrugations depends on the speed of vehicles travelling across the surface. Slow speed roads in national parks with a 40km/h speed limit form nasty little washboards. High speed outback trucking forms the monster corrugations 4Wders know and love. Stiff springs and hard tyres form the best corrugations. Blame Toyotas.

Nature abhors a smooth surface. Ripples form everywhere there is movement.

Originally Posted by bee utey

Corrugations are a sign of energy being transferred from one medium to another

Pretty much. My understanding is they're formed by the harmonising of suspension.

Years ago when I used to do a lot of travelling in the NT, Gulf country and up the Cape area I noticed that most of the dirt roads leading to/from the Aboriginal communities in the area would be badly corrugated, worse than other roads in the area. Put it down to the the fact that most of the cars used in these communities were older dilapidated ones with stuffed shockies. Once they hit a bump the wheel would keep bouncing for some distance.

I reckon it's more to do with the roads leading to/from the communities having been surveyed (straightened), formed and graded at some time. This leads to fast speeds which leads to big corrugations. If the vehicles aren't valued by the drivers (cheap bombs or government supplied) this will add to the problem.
A good example of this is the CSR either side of Kunawaritji on the CSR, straight as an arrow for 100 Km in either direction and very badly corrugated. Not helped by the 'drive as fast as possible over corrugations' brigade who generate revenue for the community in the form of suspension repairs . Prossibly the longest most consistently corrugated length of road in the country.

I remember a couple of years ago asking a local at Jervois, in central Australia, if the rather corrugated road would be graded before the upcoming annual rodeo. 'Good heavens no ! ', or words to that effect was the response. Last thing we wan't is the 'young bucks' driving fast on good roads, this just leads to rollovers. We'll grade 'em after the rodeo.

Deano

Something similar to road corrugations for those interested in railways: I gather that 4 wheeled wagons have been mainly phased out because they are wreckers of tracks. When there are irregularities in it, especially sideways, the whole wagon bucks from side to side and makes problem worse. However, when there are 4 or 6 wheel bogies on ends of the wagon, just the much lighter mass of these wiggles.

An old timer from my youth. (gosh, that was a long time ago..) blamed the introduction of those new-fangled tubeless tyres for making them worse...

When driving over the SA unsealed secion of the Nullabor (Same era...) I'd find a speed that took the pain out of them... Faster or slower would hammer the car and bounce it all over the road. The sweet spot would still be noisy, but smooth and stable ride/handling.

1967 Crown with coil suspension and Kleber fibreglass belted tubeless radials. Between 80 to 140 km/h, AFAIR