BajaNomad - What causes washboarding?

What causes washboarding?

Oso - 7-29-2005 at 06:27 PM

I'm sure many of us have lost tooth fillings and various nuts, bolts etc. on washboard roads. I've often wondered how this phenomenom occurs. At first I thought it had something to do with wind as one sometimes sees similar patterns in dunes. But then, why didn't the same thing happen on either side of the road? I finally got concerned enough to look it up in The Straight Dope:

Dear Straight Dope:

We live in a rural area and on many of the unpaved roads a washboard effect develops. Others I've asked an explanation say it's a result of bumps causing tires to leave the ground and then land, and erosion takes care of the rest. This answer doesn't seem to account for varying speeds, car weights and tire sizes. The ruts seem pretty uniform in their depth and spacing--wouldn't erosion create a more haphazard effect? --mileary

SDSTAFF Hawk replies:

The phenomenon you refer to is known as "washboarding," a wave-like pattern on unpaved roads that might more aptly be called speedbump hell. As you've observed, the ruts occur with striking regularity, belying a chaotic event like erosion.

According to Tom Pettigrew, a Forest Service engineer, the cause is an unlikely source: your car's suspension. (Well, maybe not yours specifically, but it's not innocent in this matter, either.) A vehicle's suspension system distributes the shock and energy of road irregularities with a bouncing rhythm called harmonic oscillation. At each downstroke, the wheels exert extra force on the road, causing the particles in the road to either pack or displace at regular intervals. Once a pattern of ruts starts to establish itself, it becomes self-reinforcing due to what engineers call forced oscillation. The next car hits the same irregularities in the road and bounces at the same rate, causing the pattern to become more and more defined. Forced oscillation overcomes minor variations in oscillation rate that might otherwise arise due to differences in car weight.

Wouldn't variations in speed affect the washboard pattern? Sure, which brings us to another critical part of the feedback loop: you, the driver. Drive too fast on a washboard road and the downstroke exerted by the car wheels may meet the road at a point where a bump is ramping upwards. You know what that means: You bounce off the ceiling. Instinctively most drivers slow to a speed at which the downstrokes coincide with the troughs between bumps, reinforcing the pattern.

Washboarding is inevitable in any unpaved road that sees fairly heavy traffic. The only way to avoid it is to: (a) radically redesign how automotive suspensions are made, (b) give up suspensions altogether, or (c) keep off those dirt roads.

bajalou - 7-29-2005 at 07:17 PM

That's why alot of Baja roads are called "4 or 40". Anything in between beats you and your vehicle to a early death.

:coolup:

Bob and Susan - 7-29-2005 at 07:51 PM

Oso I think....
The correct answer is:

Tires do not produce dust uniformly even on uncorrugated roads, but rather in little spurts arising from rapid bouncing of the wheels.

If the wheel moves slowly, no corrugations are formed, but instead creates a deep rut.

Distances between ruts increase with speed.

When the wheel reaches a certain critical speed, it begins to move in short hops, bounding on random irregularities of the surface.

Hitting an obstacle, even a small one, propels the wheel into the air for a certain distance.

When it lands further down the track, it sprays sand forward and to the side, thus creating the beginning of a crater.

Each time it digs itself in at a crater it has to ride out again and thus repeating the pattern.

To not create washboard roads you must let most of the air out of your tires (hard tires corrugate roads faster), and you must be willing to travel at speeds less than ten miles per hour.

Bruce R Leech - 7-29-2005 at 08:15 PM

they are caused by people out of beer going to fast to buy some more. :bounce:

Great post Oso

Mike Humfreville - 7-30-2005 at 01:31 AM

Here's another thought:

The washboard roads I drive the most happen to also be hilly, so I'm typically going either up hill or down hill. Duh!

But here's the thought part: Typically, cars driving dirt roads downhill need less acceleration. Since 1) it is the acceleration coupled with the harmonic oscillation that forms the washboard and 2) going downhill uses less acceleration, a significant part of the equation is removed or at least reduced.

Since the reverse applies to going uphill, where more acceleration is required, the harmonic oscillation is increased, causing larger washboards.

As a result of all this babble I have developed what I think of as the "up the down side and down the down side" theory, which stipulates that I am less likely to encounter major washboarding if I am going uphill and cross over to the downhill side of the road. Likewise, when travelling downhill, I stay on my own side of the road.

This has worked well for me except during two circumstances: 1) Since everyone else is smart enough to figure this all out on their own, both sides of the road will be equally washboarded, and 2) Oncoming tractor trailers while I'm in the wrong lane!

i think the correct term is...

eetdrt88 - 9-1-2005 at 10:33 PM

Quote:

Originally posted by bajalou
That's why alot of Baja roads are called "4 or 40". Anything in between beats you and your vehicle to a early death.

:coolup:

8 or 80

simple

jerry - 9-2-2005 at 12:19 AM

people cause washboard ever see a goat trail with washboard?? a pristine beach?? a virgin snow withwash board? nada so everyone drive 80mph the ones that survivewell make less waSHBOARD SIMPLE ITS BETTER THEN PAVING THE WORLD
HAVE A GOOD ONE

pompano,it looks like youre having some fun in that photo...

eetdrt88 - 10-5-2005 at 01:51 PM

you know that is not allowed :lol:

Sharksbaja - 10-5-2005 at 02:09 PM

That photo obviously was shot with Kodachrome film in a Brownie camera

or maybe a bad scan :lol:

THem Texas Longhorns? Brahma?

David K - 10-5-2005 at 03:09 PM

Washboards happen on GRADED ROADS... which is often termed as 'Improved Roads' (vs. unimproved or natural two tracks)! Driving down Baja in the 'old days' was real fun, once you were south of San Quintin or north of Pozo Grande... between which was ungraded two track road (except Santa Rosalia to Mulege, but with so little traffic, no washboarding).

Boycott Graded roads!!! :lol:

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When I first went down the peninsula to the tip:

From near Colonet (where pavement ended southbound) to San Quintin, the road was graded and ready for pavement (in 1962)... But, no pavement came, so the graded road became washboard Hell... The locals created parallel roads to avoid the washboard (and still do where washboards exist and terrain permits).

The highway north from La Paz was paved to Constitucion (El Crucero then) in '61... But, so thin it was gone by '66, recessed back to near Santa Rita... The remaining graded road north to Pozo Grande junction was washboard... The main road went through Comondu in the 60's. The new highway from Insurgentes over to Ligui/Loreto was built in '71-'72 when pavement reached all the way to Santa Rosalia that year... and on to Guerrero Negro by spring '73.... Poor El Arco (once the state border town on the main road) was bypassed in favor of the newer salt mine town!

South from La Paz in '66: Pavement only went 10 miles, then a new graded road went as far as San Bartolo, and almost to Los Barriles where the remaining road to Cabo San Lucas and back around to Todos Santos was a simple unimproved dirt road. From Todos Santos back north to the new graded road, it was a smooth graded road. By 1970, the pavement reached Cabo San Lucas!

The Baja Ca Sur road builders were much much faster than those in Norte. Perhaps because Sur was still a territory (until 1974) and didn't have state government to mess with?

coco's done quite a job...

eetdrt88 - 10-5-2005 at 07:57 PM

down by his place of creating some nice parallel roads at some of the real bad areas....i've gotta say that driving his "newer" roads put a very big grin on my face :spingrin:

Graded roads

jrbaja - 10-5-2005 at 08:40 PM

have nothing to do with wahboard. Vehicles do. Neither of the arroyos to my place down south are graded. They are sandy arroyos. Which smooth out after a rain. But, even with a minimum amount of traffic, they are washboarded within 2-3 days.
And they stay that way until the next rain.

David K - 10-5-2005 at 10:26 PM

:lol:

See there DK

jrbaja - 10-6-2005 at 09:33 AM

If you just post your sense of humor, you are never wrong about anything. It's when you pretend to know something that makes you look stupid.

It's about what causes washboard.

jrbaja - 10-6-2005 at 09:57 AM

And graded roads have nothing to do with it, except for scrambling the eggs.

David K - 10-6-2005 at 04:48 PM

Washboard (corregated) roads are always graded (scraped, bulldozed) first... The 'jeep trails', (unimproved) simple parallel ruts, are always more pleasurable to drive, and when they have a sand base, are very nice to drive...

My point was that graded roads are not always desireable. Not that they are the ONLY place one finds washboard conditions.

It really isn't necessary to prove your intelect by always contesting anything I say here. In fact, you very well may be proving something else.
If I am not on the ball on some information, then let's see if anyone else can spot it.
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A couple years ago, I said Pemex (government run/ price controlled gasoline distribution where no competition from the private sector is allowed) was an example of government socialism. Roberto had a fit and said I was dead wrong... Well, after meeting the owner of a Pemex franchise and learning more... I am all the more convinced it is pure socialism... the way the federal government controls fuel there.

In fact is is even more severe than other forms of socialism, like in Australia where at least private enterprise is allowed, but tax subsidized competition by government run business competes with the tax paying private businesses... like transportation, medical care, etc. In Mexico, there is no competition in gasoline production and distribution.

Jeeeezis Dude

jrbaja - 10-6-2005 at 05:42 PM

Is everything political with you? Who gives a rats katootie about your feelings on Pemex gas stations? Or politics?

Do you hold elections around your campfires just to keep in practise?

When I see someone post something inaccurate or wrong info, I usually say something. So do many others on here and I'm sure we expect to be called on misinformation ourselves.

The thing is, you spending so little time here, most of your info is wrong, limited, or out of date when it comes to Baja. And there's no hiding that with double talk.

And it seems as if your info on off roading has some limited slips as well! Maybe if you picked up the pace a little you would be doing better than half fast :light:

David K - 10-6-2005 at 08:40 PM

Are you blind, jr? Do you look at anything on the Trip Reports forum?

I go to Baja monthly or more for camping, off roading, moteling, eating, exploring, photography, now even having dental work done...

What's more, I share my trips to Baja with you guys who are interested by posting photos and details of people, places, and things of interest to travelers and adventure seekers...

Yet you want to get the newbies or ?? to believe that I "spend so little time here..." LOL!!!

What is it you do here on Nomad?

Complain, name call, act superior because you live (in a gringo enclave) next to Rosarito Beach... Grow bamboo to help locals create an industry, noble but will anyone besides you get to buy direct from them?

You ask us to bring you clothes and bug spray, so you can take it to them... Well, sometimes I guess... There is still a case of repellant waiting for you to take south (one year after you said you were).

Why are you so full of spite for me and my friends here (you name call 'chicken coupers' or something childish like that)?

We (Nomads, most I consider friends) enjoy going to Baja, we help the locals (without bragging here) in various ways, we read and post on Nomad to keep a connection to Baja and maybe meet others who share our addiction.

WHY does that scare and bother you so much that you must be negative so often? Why can't you be the nice guy that you used to be? What has happened to you jr?

Washboard roads-------

Barry A. - 10-6-2005 at 10:33 PM

Pompano explained it pretty darn well, I thought. I have always noticed that graded roads DO have more washboard than the jeep tracks that David K. talks about, and I believe that this is caused by people driving faster on graded roads than on jeep tracks. Take everything that Pompano presents, coupled with "speed", and you get horrible washboard. I seldom have encountered washboard on jeep tracks, except where the jeep track is very straight, which in turn allows for speed. I concluded that speed is the main culprit, but I could be totally wrong.

David K - 10-6-2005 at 10:50 PM

I think you are right Barry... I didn't say that it only exists on graded roads, but that graded roads all seem to become washboard (if the rescaped frequently to knock down the little berms of sand/gravel).I dislike graded roads when compared to unimproved roads...

In Tim Walker's great web site www.timsbaja.com, he has a link to the scintific explanation for what causes washboarding... Oso pretty much has the same explanation: bad suspention + speed = washboard.

I will get the link and add it here...

[Post note: I can't find it there, so I posted on Fred's asking where it might be.]

[Edited on 10-7-2005 by David K]

JR---------

Barry A. - 10-6-2005 at 10:52 PM

JR said:
"When I see someone post something inaccurate or wrong info, I usually say something. So do many others on here and I'm sure we expect to be called on misinformation ourselves.

The thing is, you spending so little time here, most of your info is wrong, limited, or out of date when it comes to Baja. And there's no hiding that with double talk."

-------JR This information posted above about David K. is wrong, and inaccurate.

Bob and Susan - 10-7-2005 at 05:45 AM

Here is an older article on WASHBOARDING

http://www.gi.alaska.edu/ScienceForum/ASF6/619.html

Why Do Roads Corrugate?
Article #619
by Larry Gedney
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This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Larry Gedney is a seismologist at the Institute.
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Washboard roads are a bane to travelers worldwide. This includes, of course, Alaska, where the options for getting away from it all would be limited indeed if gravel roads are excluded from one's itinerary.

Corrugations that produce washboard roads are not limited to those with sand or gravel surfaces, but are also found in asphalt pavements and even in railroad tracks, although on a less severe scale.

It would seem that such a common phenomenon should be readily understood and explainable, but the fact is that the process which produces them was a subject of controversy among engineers for many years.

One of the most popular theories was that a tire, even as it rolls, pushes material ahead of it in a heap.

Once the pile reaches a certain size, the tire rolls over it and starts the process again.
As it developed, this is incorrect.

The January 1963 issue of Scientific American contains an article by Dr. Keith B. Mather, now Vice Chancellor for Research and Advanced Studies at the University of Alaska, which puts the matter to rest once and for all.

Working at the University of Melbourne, Mather observed that vehicles passing over the unsurfaced roads of Australia's "outback" did not produce dust uniformly even on uncorrugated roads, but rather in little spurts arising from rapid bouncing of the wheels.

This led to the construction of a laboratory apparatus which would permit the observation of wheel and road interactions under controlled conditions.

The first experiments utilized a five-inch wheel mounted on the end of a shaft which pivoted about the center of a sand track 24 inches in diameter.

Locomotive forces were provided by pushing the arm around the track with a finger.

Unexpectedly, this soon produced little corrugations several inches apart in the sand.

Encouraged by these results, Mather then proceeded to construct a somewhat more elaborate system equipped with a variable speed electric motor, which drove the axle, a spring-mounted wheel and a revolution counter.

Parameters such as weight, size of wheel and stiffness of spring were made independently adjustable.

Among the more significant findings were that:
If the wheel moves slowly, no corrugations were formed, but a deep rut instead;

it did not matter whether the wheel was driving or idling, at sufficient speeds, washboarding occurred;

the trough-to-trough distances between ruts increased linearly with increasing speed; and

sand was not pushed ahead of the wheel and then overridden to begin another cycle, as had been commonly believed.

The most important contribution to understanding washboarding lay in the observation of how the corrugations are actually formed.

When the wheel reaches a certain critical speed, it begins to move in short hops, bounding on random irregularities of the surface.

Hitting an obstacle, even a small one, propels the wheel into the air for a certain distance. When it lands further down the track, it sprays sand forward and to the side, thus creating the beginning of a crater.

Each time it digs itself in at a crater it has to ride out again and thus repeats the pattern.

If traffic were to move at widely diversified speeds, different "hop-lengths" might tend to cancel each other out, but depending on road conditions, all traffic tends to travel in a rather closely constrained speed range, thus compounding the problem with each successive vehicle.

Corrugated roads would be all but eliminated if people followed two simple rules.

First, they must let most of the air out of their tires (hard tires corrugate roads faster), and second, they must be willing to travel at less than ten miles per hour.

Since it seems unlikely that either of these guidelines would be followed, the only thing that remains is to construct all rural highways out of three-foot-thick reinforced concrete--not a likely prospect for the foreseeable future.

[Edited on 10-7-2005 by Bob and Susan]

David K - 10-7-2005 at 08:05 AM

Thanks Bob & Susan!

Not to change the subject

jrbaja - 10-7-2005 at 09:15 AM

but are there more repellants at Baja Cactus besides the 5 cans you dropped off David ? I know there is baseball stuff waiting there but as far as I know, they already gave me the repellants that were there and I took them south a long time ago.

David K - 10-7-2005 at 10:21 AM

I am only reporting what Antonio told me, that the case of repellent he took there, from here, that I purchased, was still there.

Antonio is at Baja Cactus right now and will likely IM with me later tonight on his new lap top, so I will have him double check. If it is still there, would you please pop in and take it south next time?

Thanks JR.

I was told the 5 cans were from you

jrbaja - 10-7-2005 at 01:27 PM

Did you also buy a case I wasn't aware of? Anyways, as soon as I drive down I will get um. Gracias.

David K - 10-7-2005 at 02:00 PM

I bought a full case (sealed box) which I think was at least 6 cans... but it was so long ago it may have been a dozen??

Perhaps stopping into the Baja Cactus lobby just to see if there is anything for you there (from others who reacted to your requests) would be a wise regular thing to do... it is staffed 24/7 unlike the other motels in town.

Rather than the baseball equipment sitting there unused for so long, I think the doner okayed that it went to one of the local teams who could really put it to good use. This is just hear-say, but you can check with Antonio or the person who left it there for you last July, to validate that.

David

jrbaja - 10-8-2005 at 11:54 AM

When I picked up the bag with your repellants in them last December, that's all they gave me. 5 cans in a bag.

If I could afford to drive down everytime someone left a donation there, I would be very very happy.

I also didn't realize there was a time limit on how long things stay there before being distributed locally. Antonio didn't mention it when I talked to him a couple weeks ago.

But, now that you are invloved, there seems to be some confusion going on. Like whenever tourists like you get involved with foreign affairs.

Outdated information, false information, and exactly what I was talking about in the other post.

And David, you sure seem to like bringing up my donation program. Maybe you should try it yourself sometime instead of searching for lost missions and whining about what others are actually doing! :light:

soulpatch - 10-8-2005 at 01:35 PM

This was an entertaining thread until you two started your sniping again. Maybe we should ask Doug to have a DK and JR topic heading for exclusive one-upmanship. Maybe you two could edit your bullchit out of this thread so it is what it started out as. As soon as you do I'll dump this post.