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aostling
11-04-2009, 06:02 PM
The New York Times business section today ran an article about a new Oshkosh truck developed under a Pentagon contract. It stated that the truck could climb a 60-degree slope. I knew that was in error, and figured that somebody had meant to say "60 percent inclines."

Indeed that is the case. I left the newspaper in the coffee shop where I read it, but I see that the online version has been corrected, as you can see here: http://www.nytimes.com/2009/11/04/business/04oshkosh.html?scp=1&sq=armored%20truck&st=cse.

What is percent slope? I've long held the belief that it is the ratio of vertical rise to distance traveled, which would be the sine of the angle (multiplied by 100 of course). But Wikipedia and my dictionaries define percent slope as the ratio of vertical rise to horizontal distance, which is the tangent of the angle. Anybody have a civil engineering textbook? I'll believe whatever that has to say on the subject.

This brings up a question as to what is the steepest slope a vehicle can manage. I've seen bulldozed firebreaks which almost defy credibility. How steep a slope can a bulldozer climb?

[edit] changed "slope" to "inclines," the word used in the NYT online article

Lew Hartswick
11-04-2009, 06:18 PM
Just looked in the college Surveying book and they don't use
"Slope" as any measurement. The term is used as a description
in talking about railroads as to the "slope" of the fill to the bed from
surounding terain. Again in how to "tape" horizontal distances when
the terain slopes. ( cutting tape ) etc.
But no mention of how angles from horizontal would use it.
...lew...

AD5MB
11-04-2009, 06:25 PM
grade. 6% grade, et cetera

andy_b
11-04-2009, 06:30 PM
a HUMVEE is rated to climb 60% slopes, so some vehicles can certainly do it. a 60% slope looks to work out to about 30 degrees. i have a small crawler (Oliver OC-46) that can easily climb a 60% slope. the problem is i feel like i am going to flip over backwards doing it. :) i wouldn't doubt it could climb a 100% slope (45 degrees) but you would need balls of steel to be driving it.

andy b.

SDL
11-04-2009, 06:33 PM
We used to use the ratio on road signs ie 1 in 10 as 1:10, or 1:4 etc, for a percentage its the fraction as a petcentage, so 1:10 is 10% 1:4 is 25%etc.

Steve Larner

brian Rupnow
11-04-2009, 06:58 PM
I've always wondered about that myself. Wouldn't 100% slope be straight up, as in 90 degrees to horizontal?

kendall
11-04-2009, 07:03 PM
Would think a 100% grade would be 45 degrees. (12:12) 50% would be 6:12 etc.

Ken.

edit: meant to say 50% would be 22.5 which equals 6:12
Being a carpenter, I find it much easier to determine the angle if I translate it into pitch

camdigger
11-04-2009, 07:17 PM
IIRC, grades are measured in percentages while slopes are measured in ratios, especially when specifying "backslopes" as in the inclination of the ditch on the side of the highway is specified as backsloped 2:1 or a borrow pit is specified as backsloped 2:1 on the sides and 3 or 4:1 on the ends.

Motor scrapers should be able to negotiate at least 2:1 slopes... crawlers 1:1 watched them do it lots on assorted sites over the years. It is a bit disconcerting to watch #125,000 of D8H, K, N, or T back out of a pit dug 1:1 and come over balance on the edge:eek: Crawlers are often asked to negotiate slopes deeper than they can dig. Sometimes the operators will push up a small tapered pad at the end so the dozer will dig steeper.

FWIW, it is safer to go straight up or down a slope on a dozer. A dozer on a side slope may slide sideways down hill! Ask any operator who's done it, especially hair raising in bush country...:eek: :eek: :eek:

The Artful Bodger
11-04-2009, 07:26 PM
Baldwin Street in Dunedin is reputed to be the steepest street in the world:-
http://www.odt.co.nz/files/story/2008/04/BALDWIN_STREET.JPG

35% gradient = 1:2.86

aostling
11-04-2009, 07:58 PM
Baldwin Street in Dunedin is reputed to be the steepest street in the world:-


I drove up Baldwin Street when I was in Dunedin in 1995. My car, an old Datsun, strained at the grade. "I'm sure glad I don't have to drive back down this street," I thought to myself (wondering about the brakes). Only when I got to the top did I discover that it is a dead-end street!

Evan
11-04-2009, 08:10 PM
Actually the incline of a road given in percentage is a measure of it's gradient, not it's grade. Grade is measured in grads. There are 100 grads in 90 degrees and the 100th part of a grad is a centigrade. That is why metric temperature measurements were switched to the unit name celsius so to avoid confusion with the unit centigrade.

motorcyclemac
11-04-2009, 08:15 PM
yep...dozers will climb scary steep hills. So steep that the vast majority of your body weight is on the back of the seat and the steering levers will slop back ward if they have much play. I used to ride along with a neighbor who owned a D8. I would sit off to his side on the sheet metal just to watch. I was an enthusiastic kid. He would occasionally go up hill and I would stand up and lean on the roof strut holding on for dear life.

Cheers
Mac.

tattoomike68
11-04-2009, 08:36 PM
grade. 6% grade, et cetera


Thats a six foot rise or drop in 100 foot run. metric is the same 6 meters in 100 meter run.

thats the way it works when you see a sign "6% grade ahead."

Evan
11-04-2009, 09:10 PM
This is the original trail into the Barkerville gold fields during the big Cariboo Gold Rush. At one point the town of Barkerville was the largest city west of the Mississippi and north of San Francisco. This trail still exists and can be driven if you have a narrow vehicle. I have taken my Ford Ranger over it. I don't know how steep the steepest parts are but they are very steep. The trail is at most 5 to 6 feet wide so most full size vehicles won't make it. I can't imagine trying to take a horse drawn wagon up this hillside, especially in winter. Once you start up you are committed. There isn't any place with enough space to turn around past the first switchback. The turns must be negotiated by backing and filling 5 or 6 times.

http://metalshopborealis.ca/pics/yankspeak1.jpg

tattoomike68
11-04-2009, 09:18 PM
This is the original trail into the Barkerville gold fields during the big Cariboo Gold Rush. At one point the town of Barkerville was the largest city west of the Mississippi and north of San Francisco. This trail still exists and can be driven if you have a narrow vehicle. I have taken my Ford Ranger over it. I don't know how steep the steepest parts are but they are very steep. The trail is at most 5 to 6 feet wide so most full size vehicles won't make it. I can't imagine trying to take a horse drawn wagon up this hillside, especially in winter. Once you start up you are comitted. There isn't any place with enough space to turn around past the first switchback. The turns must be negotiated by backing and filling 5 or 6 times.

http://metalshopborealis.ca/pics/yankspeak1.jpg

We went to uculelett, Vancouver island and when they say 11% grade its a damn goat trail, hold the motor homes gas pedal to the floor or you end up crawling up at 15 mph balls out. I know the logging truck drivers know the road and hold it down and get a big head of steam up and keep it rolling. those boys can drive. :)

andy_b
11-04-2009, 10:19 PM
FWIW, it is safer to go straight up or down a slope on a dozer. A dozer on a side slope may slide sideways down hill! Ask any operator who's done it, especially hair raising in bush country...:eek: :eek: :eek:

yup. those nice raised ridges on the grousers that let you dig in going up or down hill work just as well as rails letting you slide sideways down the hill. :)

andy b.

John Garner
11-05-2009, 12:26 AM
That "1/100 of a right angle" unit was a byproduct of the French effort to decimalize metrology after the revolution. They called it the "centesimal degree", and divided it into 100 "centesimal minutes", each divided into 100 "centesimal seconds". The unit-identification abbreviation for the centesimal minute is "c", that of the centesimal second "cc."

The common American-English term for the centesimal degree is "grad" (the British often call it a "grade", sometimes "gradient"), while the Germans think a grad is 1/90 of a right angle, our "degree". Needless to say, this use of the word "grad" to identify two different angular units was a fruitful source of confusion.

To eliminate that confusion, the Fédération Internationale des Géomètres (FIG) -- in English, the International Federation of Surveyors -- officially renamed 1/100 of a right angle the "gon" in 1984 (or thereabouts). Surveyors and the makers of survey instruments took to the new name, but the calculator makers haven't yet caught on. Pity.

motorcyclemac
11-05-2009, 12:35 AM
Evan...that road you posted reminds me of my days back when when I used to drive Mixer truck to deliver concrete. I did a job up on a mountain side. It was a base for a cellular phone tower. I had to back the truck up a road similar to what you showed. It was 3.5 miles up hill with switch backs. You couldn't drive up as the concrete mix would run out the back of the drum. So back in we did. Twas a long time looking in the mirrors.

Cheers
Mac.

darryl
11-05-2009, 02:50 AM
So 100% slope means the rise is 100% of the horizontal distance traveled. Seems like 45 degrees to me.

I went up a skidder trail once in my land cruiser. Going up it seemed like 45 degrees, backing down it looked like about 75 degrees. What a pain that was. Took me 3 hours to turn around 'cause for some reason the cruiser wants to roll if it's leaned that far :)

Not only was that trail steep, it was narrower than the truck in one spot. Trees both sides- I closed my eyes and just kept going. One tree had to give way a little.

Hmm- I kind of miss those 4x4ing days.