How Are <span class="highlight">Corrugations</span> Formed?

Rubbish. Nothing to do with it.

Speed does contribute but not in the manner implied by this contentious comment. See my post further down.

That sounds like the most credible theory I've heard so far.

Note that vehicle speed, suspension frequency etc. are all variable depending on the driver (& their mood!) and the car itself - these should all be random enough that one car's corrugations would be cancelled by the next car (unless suspension frequency is identical and the car is being driven exactly the same way).

I don't know that you'll ever PREVENT corrugations, but you can reduce the speed at which they form as you've said: by lowering tyre pressures, more driven wheels (2 wheels are more likely to start 'skipping' on the corrugations than if all wheels are driven). Since most corrugations seem to be worse in the corners and/or up hills, I'd expect that avoiding hard acceleration would also help to slow the rate of formation of corrugations.

So why are the corrugations basically parallel to each other and normally extend from gutter to gutter?

I'd suggest that because not everyone drives the same distance from the edge of the road, particularly as corrugations begin to form and most people try to avoid the worst ones (and end up making their own).

As you've rightly said, they often do seem to extend gutter to gutter and are parallel to each other. The suggestion that corrugations are formed by a "bow wave" building up in front of the wheel as it rolls along and that would tend to suggest that the spacing of corrugations would depend more on the material of the road (Note that for each vehicle, speed and suspension frequency vary yet the corrugations get bigger and bigger so if these were the biggest contributing factors, you'd expect the corrugations to be very random and even cancelled out by the varying traffic).

I like this explanation too - it seems a little more "scientific" than some I have heard, a little more rational.

I would suggest that there is also a suspension resonance factor that also contributes and can be mitigated in a limited manner by tyre pressures, shock settings and spring stiffness.

Interestingly my Range Rover was little affected by corrugations, and the LandBruiser that I have now seems to jump and skip a bit. The rear air springs might have something to do with this behaviour - some say they "chatter" a bit on corrugations. I am about to find out! Simpson - here we come...

viz

Yes Timbo, I imagine "bow waves" would cause random irregularities.
It was suggested to me some time ago by someone that the major cause of corrugations is rain water washing across the road, particularly on bends with a strong camber or where there is a reasonable crown in the road....What do you think?..( I don't know how long between rain & grader to fix or cause the corrugations)

I don't know that rainwater CAUSES corrugations, but it sure helps to make them worse! Obviously, the rainwater flows to the lowest point so it will find the troughs in the corrugations and it will flow to the downside of any road camber (usually the inside of a corner). As it flows, it takes bits of dirt with it (erosion), making each trough that deeper.

I personally don't think suspension resonance would be significant as almost every vehicle that drives along will have different suspension frequency (except perhaps in a mine where every vehicle is an identical 75-Series ute!).

I am thinking more that resonance is not so different between various vehicles of the same weight and type - within a narrow range at best. Trucks for instance do not seem to be so affected (note: I am not an expert on outback truck driving), howecweI am told that unshockied and empty truck airsprings "chatter'.

viz

Pity the ones at sea make me crook.

Cheers Graeme.

With reference to the research and my comment to Grahame earlier. If we all drove at totally different speeds then the likelihood of corrugations occuring is severly limited. But we must have all speeds covered including both fast and slow speeds.

Thus it follows that if we all travelled at the same speed of say 15Km then the corrugations would be far worse.

Phil

Whilst not disagreeing with the research, I consider that the conclusion that speed is not a factor a bit of a long bow to draw

My reading of the article is about the formation of corrugations, but doesn’t discuss the energy inherent on a wheel travelling at speed.

The faster a wheel is travelling, the more energy is contained within the wheel. When lifted off the surface (even momentarily), this energy will be transmitted to the surface in one spot when full weight is reinstated.

The practical application (excuse the pun) of this is that the faster the wheel is travelling and an obstacle encountered, the more energy is transmitted to the road surface in one spot when it lands. This has a greater capacity to move the road surface and more quickly form more severe corrugations

The harder the tyre (over inflated) there is less capacity for the tyre to absorb the wheel’s energy when it is confronted by an obstacle. Therefore, the some of the forward energy is transformed into a vertical energy and the wheel will go higher and come down harder when it resumes contact with the ground. This will also compact the leading face of the corrugation, making it harder and steeper, increasing the vertical component of the wheel travel

Does stiffer suspension assist in formation of worse corrugations? I think it might

It’s been over 30 years since I have done any Newtonian physics or force vectors, so, if my assumptions are wrong, please correct me

So what do you want me to say. I am not a scientist now a physicist.

I really do not care how they are formed but the obvious accusation that they are all caused by high speed racers I find quite the unintelligent blab you get from everyone. If speed was the caused of all road evils then why are the F1 drivers still alive. Yeah I know that's a long bow to draw.Well so is the statement that we should all slow down and therefore there won't be any corrugations.

I only know that I find our car with the load we have, the modofications to the suspension and the much lower tyre pressures it can comfortable at somewhere between 40 and 80 KPH. It has never been comfortable at 15KHP. Driving at 15KPH is quite noticeably teeth shaking as others have said.

I'd be suspicious of anyone saying that speed alone causes corrugations, particularly on outback roads where it seems no two vehicles (or convoys) ever travel at the same speed (ie. you often catch up to slower travellers and/or are overtaken by faster travellers).

From my experiences/observations, corrugations tend to be worst where a vehicle is accelerating (ie. out of a corner and/or up a hill). Perhaps it's not how fast the vehicle is travelling, but how hard it is accelerating that has a bigger effect on the formation of corrugations.

vk1dx,
The speed that your vehicle travels comfortably at has nothing to do with how the corrugations are formed. Speed, wheel loading, tyre pressure all have a bearing on corrugation formation. F1 tyres have very little pressure and the vehicle is very light weight on an almost flat very even surface.
No one has even mentioned axle tramp yet !

KK

Speed is a critical factor in the formation of corrugations.

No stationary vehicle can contribute to them.

Mixed traffic, traveling at a range of speeds, tends to slow the formation of them.

Corrugations are not simply a surface phenomenon.
During the remaking of damaged roads, evidence of regular compaction waves can be observed at significant depths.

They can sometimes contribute to the early onset of a corrugated surface on a remade road.

Timbo Agreed. Thats quite possible.

Kiwi Kia Like I said I do not care how corrugations are formed. I was only saying how we drive. Also our axle tramp (IFS front and live axle rear) has been addressed with our suspension mods.

Phil

Rolly. Exactly what I have been trying to point out but people are saying that going faster than 15KPH is wrong. Bad idea and therefore you are a threat to the community and should be banned.

Here is what you meet. Brainless woman. Not only women and thank heavens they are in the minority. On saturday 20th June this year at approx 7:50AM when leaving the Bungle Bungles, we passed a car that had stopped for us. We were doing 40KPH as we passed. Yes!! 40KPH. I was trying to stay just under and near 40KPH and that's what was on the GPS. The woman passenger had the hide to yell out on the CB "he looks like he is airborn". At 40KPH!!! You have to be kidding. The microphone went back on the cradle and they were not thanked for letting us through. We waved and said thanks to their mates up the road though. By the way the speed limit is 50. I have great difficulty with this ignorance.

Maybe its not the best idea for everyone to travel at 15KPH after all????

Phil

In answer to the comment about F1 drivers I have this to say.

Firstly they know how to drive at the speeds they do

Secondly Nothing is coming the other way ( mostly anyway)

Speed does not kill bad driving does and at any speed.

The harping on by the various Governments that speed kills is absolute rubbish.

Incompetent driving at any speed kills.

The only difference is high speed does it quicker.

When I was young I lived in a remote part of NZ that was reached over 120k of gravel road.

We used to see how fast we could do it and am still alive 40 years later.

Why.

Because we learnt to drive properly.

Had we not I could have been dead several times.

The trouble today is that to many think driving is something you do whilst you are doing something else.

Like changing Cd's, looking at the birds at the bus stop, talking and texting whilst driving and my pet hate those who have to turn and look at the passenger when talking to them.

Lets face it its a full time job and anyone who doesnt treat it as such is as they say "A complete Idiot"

Just my rant

At last someone understood what I was talking about when I mentioned the F1 scene. Everyone was making a blatant statement that speed kills. Yes Its the idiot behind the wheel etc who kills.

I first drove on public roads at 13. We used to drive the farm truck to town with a load of wheat for the trains. All was fine provided you stuck to the stock routes. No main street showing off. Dad actually had me driving competently at over 100 Miles PH before I got my licence. I did not say legally! My driving test was done without my knowledga on the way to a footy match. I didn't know the two in the back were the local Seargent and one of his offsiders. I just knew Dad asked me to stop and pick them up from the bowling club. I had only even spoken to the police when I got my "L" plates. And yes we did do the stop on a hill etc. Even picked the worst parking spot for me. It was a breeze. But that was the luxury of people being abl;e to be trusted and respected.

I wouldn't dare to try and change the CD's nor send a text message nor stuff around with the laptop nor the GPS. We don't talk much either when on the road. Just light chatter and diections. I lose all track of what we are talking about because I am concentrating on the corrugations and looking out for pot holes and fools etc etc. Plenty of them around too. Certainly not TAKING A VIDEO.

This is why we like isolated bush roads without the highway fools and without the city 4WD lot and the do gooders and the "private" police/vigilanties. On one track in the Kimberley in June we did not see anyone else for a whole day apart from a bloke rounding up his cattle. Just a smile, a wave, tip of the hat rim and we were on our way. Excellent day couldn't have been better. Six hours to do 132Km!!! And just the bush and us.

Just my rant and back to reality. And I don't feel like using the spell checker either this time. have a great day.

Phil

For those who do not believe in letting the pressure in your tyres down, check out the tyre shapes on the wagon towing the tyres

We have a great number of govt vehicles that travel down corrugated roads.

The private citizen caught doing this on a public road likely would get charged with creating a traffic hazard despite the fact they are doing a public service!.

Also your fuel economy is going to suffer towing that resistance.

So - if the device was left along side the road - why couldn't the various govt vehicles (where its all of us paying for the extra fuel) simply hook on and tow it the length of the track, unhook at the end and it's the next govt employee guys turn to tow it back the other way?

Having actually built (and paid for) some roads in the past including bitumen ones, I can see a downside to the towing of tyres, compared to grading the road.

That is, that the accumulated gravel material, can flow around the outside of the towed device - and where it comes close to the edge of the road, the surplus material is thrown clear of the road verge where a road grader cannot pick it up and move it back onto the road syrface.

When you paid millions of $ to win cart and spread that gravel onto the road - you can't afford to have it thrown clear of the road surface, off into the bush where it can't be recovered for use grading and filling the road in future.

Even contract grading quickly destroys a road base surface - because the canny contractor - will grade the road with less passes of the grader - by pushing surplus material off the road and into the bush. Less passes with the grader equals less time and fuel - more profit to the contractor grader.

For this reason shires should own their own grader and employ their own grader driver. In the end it is cheaper because they can conserve their own purchased road base material.

A GOOD grader driver (who's not an independent contractor) can grade the verge first to win back road base thats been pushed off the road buy vehicular traffic & water wash from rain etc.

When that material is won back it is then graded to the center and the road re crowned and graded with it's original road base. This process can go on again and again, with minimal loss of road base material.

A contractor on the other hand can grade, deep from the middle of the road to the outer edge pushing the excess material off to the sides into the bush past the verge where it can't be recovered with less passes of the grader and less fuel & time - hence more profit.

Contract graders can seemingly cost less to maintain the road than your own grader and operator except when it comes time to BUY more road base to replace whats been pushed off into the bush and lost.

As always - there's a right and a wrong way to do the job and the wrong way is the fast easy cheap way.

Cheers

What on earth brought that on. I just wated to get some types of people to check out heavily lowered tyres. And you come up with some tirade that is totally off the track. On sand its fine.

Are you seriously thinking I condone the towing of tyres. Come on mate get a life.

Feel better now that you have wrongly cajowled me.

Gee its good to see you have paid for your roads as well. So do we all pal.

Fair dinkum and aren't the twits in the photos are yanks not aussies.

?????

Gday Flywest,

I never would have thought there was anything technical about grading a road.

Thanks for that input - you learn something everyday.
(I too believe that the use of outside contractors by councils/shires and Govt. depts. is not necessarily beneficial.)

Peter

In this case perhaps we can put the tyre towing thing to rest, they are smoothing the surface so that they can see footprints left by illegals attempting to cross the boarder.

.

Probably but if you do, do it slowly or you may put corrugations in the paint.

Interesting thought Vertical corrugations LOL

I made one o' them about 30 years ago (from railway line) for errm, 'groomimg' farm tracks...

Worked very well too, if I say so meself...............

;-))

Roger is obviously a member of the 'Skip over the top' brigade, I'd say........

;-))

Yes, I saw that type of rail whilst working as a traffic controller at a rail-crossing, it was hard to believe, that it looked like it was melting, not much to do while waiting for traffic ( vehicles or a train) so I was just wandering up and down the tracks when I came upon what you described, thanks for the update