Gradients

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rubertoe
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Gradients

Postby rubertoe » Fri Jun 28, 2013 07:32 am

What with the "hills that make you get of and Walk" thread, there is a lot of talk about gradients.

I am confused?

Can someone explain to me in lay terms what is meant by a gradient described as a % (i.e 10%) and what is meant by a gradient described as a fraction (i.e 1/3).

And what it means in real terms? if say traveling over a 1000m (or 1 Km/mile) or whatever on a 10% climb how many meters above sea level would I end up at if I started at sea level...
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TGOTB
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Re: Gradients

Postby TGOTB » Fri Jun 28, 2013 07:37 am

A 1-in-10 gradient (aka 10%) means that for every 10 metres you go horizontally, you go up 1.
1-in-4 (25%) means 1 metre vertical for every 4 metres horizontal.

More generally, a 1-in-n gradient (100/n %) means you climb 1 metre for every n metres horizontal.
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Rolf F
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Re: Gradients

Postby Rolf F » Fri Jun 28, 2013 07:56 am

This might help. The Y and X columns are effectively 1 in X with the equivalent percentage to the right.

So you'd go up 100 meters in your 1000 m travelled horizontally.
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vermin
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Re: Gradients

Postby vermin » Fri Jun 28, 2013 08:27 am

Rolf F wrote:This might help. The Y and X columns are effectively 1 in X with the equivalent percentage to the right.

So you'd go up 100 meters in your 1000 m travelled horizontally.


WOT? :?

cyclingprop
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Re: Gradients

Postby cyclingprop » Fri Jun 28, 2013 08:35 am

You know how fractions work right? 1/3 = 33.333333%
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vermin
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Re: Gradients

Postby vermin » Fri Jun 28, 2013 08:41 am

cyclingprop wrote:You know how fractions work right? 1/3 = 33.333333%


I have a first degree in Engineering. Ergo I understand gradients. I have no qualification in gobbledegook. Ergo I do not understand Rolf's message. :wink:

For Rubertoe, I think TGOTB explains it neatly.

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UndercoverElephant
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Re: Gradients

Postby UndercoverElephant » Fri Jun 28, 2013 08:43 am

vermin wrote:
cyclingprop wrote:You know how fractions work right? 1/3 = 33.333333%


I have a first degree in Engineering. Ergo I understand gradients. I have no qualification in gobbledegook. Ergo I do not understand Rolf's message. :wink:

For Rubertoe, I think TGOTB explains it neatly.


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rubertoe
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Re: Gradients

Postby rubertoe » Fri Jun 28, 2013 08:46 am

So 12% would be 12 vertical metres gained for every 100 horizontal metres travelled?
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Wrath Rob
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Re: Gradients

Postby Wrath Rob » Fri Jun 28, 2013 08:48 am

Yes, by jove I think he's got it!
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fat_tail
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Re: Gradients

Postby fat_tail » Fri Jun 28, 2013 08:48 am

rubertoe wrote:So 12% would be 12 vertical metres gained for every 100 horizontal metres travelled?


correct .. doesn't sound like much does it ?
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EKE_38BPM
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Re: Gradients

Postby EKE_38BPM » Fri Jun 28, 2013 08:49 am

rubertoe wrote:And what it means in real terms? if say traveling over a 1000m (or 1 Km/mile) or whatever on a 10% climb how many meters above sea level would I end up at if I started at sea level...


Expressing gradient as a percentage is much more accurate and it is easier to work out how much you've climbed.
From sea level, if you travel 1000m horizontally on a 10% climb, you will end up 100m above sea level (100 = 10% of 1000m). A 15% gradient would mean a 150m climb etc.

The fractional description of inclines is a bit rubbish. The difference between 1 in 4 and 1 in 3 might not seem much in terms of raw numbers, but it means that the first one (1 in 4) is a 25% incline but the second one (1 in 3) is 33%.
When you get to lower numbers, 1 in 15 is just under 7% and 1 in 14 is just over 7%, so they give you less information.

I think the 1 in x roadsigns are (very slowly) being phased out.
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Re: Gradients

Postby TGOTB » Fri Jun 28, 2013 08:59 am

EKE_38BPM wrote:Expressing gradient as a percentage is much more accurate

Only if you restrict yourself to using integers. For instance a 17% climb could be described as 1-in-5.88 with exactly the same level of precision/accuracy. In fact, describing a 1-in-3 climb as 33% is *less* accurate, as it's actually 33 1/3%

I also have a degree in engineering. It may only be a third, but I did get good marks for pedantry...
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EKE_38BPM
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Re: Gradients

Postby EKE_38BPM » Fri Jun 28, 2013 09:04 am

I studied engineering (civil) but left before I got my degree. I lost marks for assuming too much knowledge in others (everyone knows what bentonite slurry is, right?
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vermin
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Re: Gradients

Postby vermin » Fri Jun 28, 2013 09:05 am

EKE_38BPM wrote:I studied engineering (civil) but left before I got my degree. I lost marks for assuming too much knowledge in others (everyone knows what bentonite slurry is, right?


Lol - I am actually writing about bentonite slurry at this very moment. Or rather, I am posting here to avoid the tedium of writing about bentonite slurry!

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EKE_38BPM
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Re: Gradients

Postby EKE_38BPM » Fri Jun 28, 2013 09:10 am

vermin wrote:
EKE_38BPM wrote:I studied engineering (civil) but left before I got my degree. I lost marks for assuming too much knowledge in others (everyone knows what bentonite slurry is, right?


Lol - I am actually writing about bentonite slurry at this very moment. Or rather, I am posting here to avoid the tedium of writing about bentonite slurry!

Kind of sounds like why I left my degree.
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Runtothehills
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Re: Gradients

Postby Runtothehills » Fri Jun 28, 2013 09:13 am

rubertoe wrote:So 12% would be 12 vertical metres gained for every 100 horizontal metres travelled?


Yes, but please note this is slightly different to saying 12 vertical metres gained for every 100m travelled on the bike as the 100m is travelled horizontally.

For most gradients this can be more or less ignored: it means 12m climbed for every 100.7m travelled on the road for a 12%. Even at 30% you're doing 30m of ascent for 104.4m. Pedantry for the win!

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Rolf F
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Re: Gradients

Postby Rolf F » Fri Jun 28, 2013 09:22 am

vermin wrote:
cyclingprop wrote:You know how fractions work right? 1/3 = 33.333333%


I have a first degree in Engineering. Ergo I understand gradients. I have no qualification in gobbledegook. Ergo I do not understand Rolf's message. :wink:

For Rubertoe, I think TGOTB explains it neatly.


Well D'uh! I didn't put the link in. Do I have to do everything around here?! :lol:

http://www.engineeringtoolbox.com/slope-degrees-gradient-grade-d_1562.html

PS I've drilled holes - I know what bentonite is!
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Jehannum
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Re: Gradients

Postby Jehannum » Fri Jun 28, 2013 09:44 am

Sorry, but 12% is closer to one in eight, so 1 unit climbed for every 8.3 units of horizontal travel.


12% = 1 in ( 100/12 )

= 1 in 8.3333


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t4tomo
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Re: Gradients

Postby t4tomo » Fri Jun 28, 2013 10:26 am

EKE_38BPM wrote:Expressing gradient as a percentage is much more accurate and it is easier to work

The fractional description of inclines is a bit rubbish. .


:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
sorry nearly spat my coffee out at this one, so excuse my descent into pedentry.

Neither is more or less accurate, its just a different way of expressing a number.

Its like saying kgs are more accurate than lbs, i.e complete nonsense.

if something is a genuine 1in3 then to say it is 33% is less accurate, as it is 33.33 (recurrring)%

and vice versa a genuine 9% slope is not 1 in 11 its 1 in 11.11111(recurring).

In steps of whole numbers and restricted to "1" in then %age is a finer scale at steep slopes but fractions is a finer scale once slope is less than 10%.

For the record i'm not an engineer.
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TGOTB
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Re: Gradients

Postby TGOTB » Fri Jun 28, 2013 10:48 am

t4tomo wrote:excuse my descent into pedentry.

You've spelt that wrong, it's pedantry.

:lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
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