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rubertoe
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Joined: Thu Jun 02, 2011 17:14 pm

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...
"If you always do what you've always done, you'll always get what you've always got."

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TGOTB
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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
Posts: 13576
Joined: Sun Oct 26, 2008 09:29 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
Posts: 1698
Joined: Wed Aug 17, 2011 12:43 pm

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
Posts: 2358
Joined: Tue Nov 08, 2011 20:58 pm

You know how fractions work right? 1/3 = 33.333333%
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vermin
Posts: 1698
Joined: Wed Aug 17, 2011 12:43 pm

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.

For Rubertoe, I think TGOTB explains it neatly.

UndercoverElephant
Posts: 5444
Joined: Wed May 27, 2009 09:04 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.

For Rubertoe, I think TGOTB explains it neatly.

Gathers round to watch the engineering slap-fight.

rubertoe
Posts: 3965
Joined: Thu Jun 02, 2011 17:14 pm

So 12% would be 12 vertical metres gained for every 100 horizontal metres travelled?
"If you always do what you've always done, you'll always get what you've always got."

PX Kaffenback 2 = Work Horse
B-Twin Alur 700 = Sundays and Hills

Wrath Rob
Posts: 2757
Joined: Mon Dec 04, 2006 21:53 pm

Yes, by jove I think he's got it!
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fat_tail
Posts: 537
Joined: Tue Aug 14, 2012 08:13 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
Posts: 5852
Joined: Sat May 29, 2010 10:42 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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TGOTB
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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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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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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!

EKE_38BPM
Posts: 5852
Joined: Sat May 29, 2010 10:42 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
Posts: 183
Joined: Thu May 23, 2013 08:49 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!

Rolf F
Posts: 13576
Joined: Sun Oct 26, 2008 09:29 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.

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?!

PS I've drilled holes - I know what bentonite is!
Faster than a tent.......

Jehannum
Posts: 103
Joined: Mon Mar 23, 2009 11:28 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

J.
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t4tomo
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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. .

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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