Gradients

rubertoe

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...

tgotb

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.

rolf_f

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.

vermin

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

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

vermin

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

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

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

Wrath Rob

Yes, by jove I think he's got it!

fat_tail

rubertoe wrote:

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

correct .. doesn't sound like much does it ?

EKE_38BPM

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.

tgotb

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...

EKE_38BPM

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?

vermin

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

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.

Runtothehills

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

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?!

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

PS I've drilled holes - I know what bentonite is!

Jehannum

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.

t4tomo

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.

tgotb

t4tomo wrote:

excuse my descent into pedentry.

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

vermin

TGOTB wrote:

t4tomo wrote:

excuse my descent into pedentry.

You've spelt that wrongly(?), it's pedantry.

Cleat Eastwood

Also confusing is that some gradient signs show the gradient at its steepest point. Theres a 17% one near me and the 17% is probably 2ft long - I still have to get off and walk though....and thats going downhill

t4tomo

I did Maths at Uni - I never claimed I could spell.

markhewitt1978

fat_tail wrote:

rubertoe wrote:

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

correct .. doesn't sound like much does it ?

No it doesn't and if you look at elevation on a map etc the hills don't look all that big. There's plenty where you are climbing on your bike or on foot and it feels like 1:1 but it's a very long way from it!

Runtothehills

t4tomo wrote:

I did Maths at Uni - I never claimed I could spell.

Personally I did engineering - this means that not only can I not spell but I think pi is 3, but lets call it 10 to be on the safe side. Not sure why other engineers are being so accurate though, all an engineer needs is good enough not right.

greg66_tri_v2.0

Cleat Eastwood wrote:

Also confusing is that some gradient signs show the gradient at its steepest point. Theres a 17% one near me and the 17% is probably 2ft long - I still have to get off and walk though....and thats going downhill

Yes - the French do it better in the Alps. Markers every km that show the ave and max % gradient over the next km.

So you know when to throw the towel in and give up...

vermin

Greg66 Tri v2.0 wrote:

Cleat Eastwood wrote:

Also confusing is that some gradient signs show the gradient at its steepest point. Theres a 17% one near me and the 17% is probably 2ft long - I still have to get off and walk though....and thats going downhill

Yes - the French do it better in the Alps. Markers every km that show the ave and max % gradient over the next km.

So you know when to throw the towel in and give up...

There are climbs longer than a km? :shock:

EKE_38BPM

Runtothehills wrote:

t4tomo wrote:

I did Maths at Uni - I never claimed I could spell.

Personally I did engineering - this means that not only can I not spell but I think pi is 3, but lets call it 10 to be on the safe side. Not sure why other engineers are being so accurate though, all an engineer needs is good enough not right.

Doesn't a good engineer make x strong enough to be safe using the minimum of material. So, call pi 4. 10 seems like overkill.

CiB

t4tomo wrote:

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.

Hurrah - a good answer. 1 in 8 is the same as 12.5%. It's the same ratio, just expressed in a different way.

FWIW I'd rather we stuck with the 1 in n method - it's so much more meaningful and we all know that a 1 in 3 is chuffing steep and a 1 in 20 is an easy slope. It's also how we always did it until some oik decided that 1 in something is too difficult to understand so we have to do it a different way. We should make life awkward for thickies.

Wunnunda

Was brought up on 1 in 'n' but quite like nn% these days. I tend to view it as "This one will leave you 5% dead....with one it's 20%....but THIS one? You got funeral insurance?"

And with that, I'll slope off...

sketchley

Just remember n% down almost certainly means n% up on the other side.