Washboarding

[72doug2,2S]

It might as well be a kind of torture for man and machine. The roads I've traveled on with washboarding are ridiculous. I've even experienced them travelling through the grass beside a good road to avoid road trash.

So, my question is how does this washboard phenomenon occur? Google has some kind of explanation, but it really doesn't address why.

[masraum]

Great question. I'm curious as well.

And then the washboarding can vary too. You can have them where the "wavelength" is very short, and some where it's quite a bit larger. I'm assuming that may be somewhat determined by how hard the surface is.

[Scott Douglas]

I was always under the impression that washboarding was caused by the tractor cleats of the caterpillar tractor that leveled the road.

[stevej37]

Tires hit a small bump and bounce up and come down and make a depression. The next car does the same, but extends the pattern. Over and over.

[1990C4S]

^^^ That. Self perpetuating.

[pwd72s]

Originally Posted by stevej37

Tires hit a small bump and bounce up and come down and make a depression. The next car does the same, but extends the pattern. Over and over.

That and water runoff from rains...water flowing in those depressions.

[Baz]

Immediately thought of this when I saw the thread title.......

[Tishabet]

Many years ago (late 90s) I did a mountain biking day trip on a trail called cherry mountain loop in NH. The loop was mostly logging road, and had a ton of washboard. There was one section where you're going downhill for a few miles and could really get moving fast, and the vibration from the washboard (this was before I owned a suspension fork) was punishing.

At the end of the ride I realized that the stem of my watch (the little knob you use to set the time) had pounded up and down on the back of my hand so much with the washboard that it had literally worn the skin away and I was bleeding.

[stevej37]

We never used a washboard at home....but we had a wringer-washer...if that counts.

Had to be careful of what you got caught in it. (esp women)

[flipper35]

Every article mentions traffic, but I know a couple places that get washboards pretty bad after a rain with only a few vehicles that drive on it all year.

[pete3799]

Mostly happens on up hills.
All it takes is one rock or pot hole to start it. Under acceleration the drive wheels hit the bump and while the suspension is unloaded the wheel spins just a little before it regains traction.
Rinse and repeat.

[Bob Kontak]

Originally Posted by Baz

Immediately thought of this when I saw the thread title.......

Asheville?

Oh yes it is. The wig center and "Haywood" give it away.

[HobieMarty]

Washa washa washa!!!

Sent from my SM-N950U using Tapatalk

[wdfifteen]

On the gravel roads around here it always occurs at the entrance to a turn or before a stop sign. I think it's a matter of the gravel resisting a bit when the brakes are applied so the gravel slightly slides, when a few stones pile up in front of the tire resistance to the slide increases and the tire rolls over the "hump" created, then the cycle starts again. Running this cycle over and over a few hundred times and pretty soon you have a washboard.

[LEAKYSEALS951]

Haha!!!!
Just got in from a 20 mile bike ride on washboarded gravel roads.

badadadadadadaadadadadaddadadadada....
(hour later)
badadadadadadadadaddadad....
best part of the ride was an interruption in washboard to ford a large stream about forty feet across and two feet deep. Nice cold mountain water. Calgon take me away.

Makes me's thinks of conservation of momentum and long forgotten physics stuff.

Up here in the mountains, it occurs on inclines/declines where the tires slip, and successively pile up higher and higher berms of gravel. All roads around here need to be graded regularly. Weird thing- heavy rain seems to even it out. Also, counties are finding it easier just to pave it than maintain the washboard.

Around here, if I'm looking at a used car, I scout the engine compartment for grey dust. If it's there, it means the car was used on a dirt road, and the struts are going to be shot. Generally, I'll also see bad seals when the dreaded gravel dust is present. Weird stuff, like transmission and main seals get trashed.

[john70t]

Maybe the asphalt mix didn't have enough rock base and whatever is used as the hardener.
Or the road opened too soon during hot weather.

[masraum]

https://www.nhpr.org/post/ask-sam-why-do-washboard-roads-form

Many people have theories about what causes a washboard, and many of those theories are wrong.

That includes the gentleman I found who had an answer to this question: Stephen Morris, a physicist at the University of Toronto, “I thought, as many people do, that the suspension might have something to do with it. It’s one of the common but incorrect reasons that people come up with for washboard,” he told me.

Over a decade ago he and some co-authors designed an experiment to figure out what it took to form a washboard. They built a circular sandbox filled with road material and ran various wheels and plows around the sandbox until washboard began to form.

Morris says that essentially, a washboard is formed by the same stones to skip.

“When you’re driving on the road and you hit a tiny bump, no matter how small, it will throw the car up in the air an amount that depends on how fast you’re going. And if you’re going fast enough you’ll come down and deform the road a little bit behind the bump,” he said, “And that little divot that you put in the road will throw up the next car and so on.”

Washboard is mostly a dry road phenomenon. When the road bed is really wet you tend to get potholes instead. And if it’s a really bad spot you can get this kinda repeating pattern of potholes.

The frequency of the washboard is a function of the average speed of the cars that drive along a stretch of road, because cars all tend to drive the same speed on the same stretch of road, which in a bit of chicken-and-egg feedback loop, that speed is determined “partly because of the washboard of course,” Morris explained.

And a bit of trivia: train rails also develop washboard, which leads to a sound called “roaring rails” and train rails have to be periodically ground down to eliminate the noise.

Many drivers who spend a lot of time driving on gravel roads will tell you the best thing to do is drive fast. Morris (and dear reader, I, too) would like you to consider *why* this works. “If you drive really fast your tire will bounce from peak to peak of the washboard and you will not feel it, and that works except you’re in the air about half the time.”

And having your tires in the air is real bad for steering. REAL BAD.

Meanwhile, driving slowly over the washboard would mean your tires would bounce at a different frequency, and would smoosh peaks.

“If everybody did that, the washboard would be slowly smoothed out, and maybe you could keep it to a manageable level, but the fact is that nobody is willing to do that,” says Morris.

Washboard roads are a collective action problem. What is best for all drivers is not what’s best for every individual driver who’s in a hurry. So next time you’re bouncing along, consider meditating on ways to fight the breakdown of civil society.

[LEAKYSEALS951]

Originally Posted by Baz

Immediately thought of this when I saw the thread title.......

Awesome! $100 bucks says Asheville