Kilometers or Miles?

[cycleruk]

...
Concerning the matter at hand, I really dislike American recipes where dry ingredients are measured in cups. I wonder if there's any practical advantage of mass over volume, or if it's just learnt behaviour on my part.

I'd guess mostly the latter.

But there's a fair bit of international variation in the cup, where there isn't in SI units of mass or volume.

Jonathan

Thinking this morning that there other variable measurements such as a Pinch, Handful and Armful.
Just thought of another - "knob" usually of butter.
Mind you watching cooking programs on the TV, a chefs pinch of salt equals a small handful to me,
The one measurement that gets most of my attention is a "wad" of £. notes.

P.S. MPG for me. I have to convert litres to gallons.

Really drifting of topic now . Sorry

[mattheus]

...
Concerning the matter at hand, I really dislike American recipes where dry ingredients are measured in cups. I wonder if there's any practical advantage of mass over volume, or if it's just learnt behaviour on my part.

I'd guess mostly the latter.

But there's a fair bit of international variation in the cup, where there isn't in SI units of mass or volume.

Jonathan

Thinking this morning that there other variable measurements such as a Pinch, Handful and Armful.
Just thought of another - "knob" usually of butter.
Mind you watching cooking programs on the TV, a chefs pinch of salt equals a small handful to me,
The one measurement that gets most of my attention is a "wad" of £. notes.

That brings us onto other quantities of money e.g. loads. loadsamoney being a unit in common 1990s parlance.

... and from that ...
A colleague used to buy pre-chopped-n-dried logs for his fire. He said the supplier would deliver them in 2 quantities, priced accordingly. You could either have:
- a "load", or
- a "half load"

I got the impression that a "load" was as much as his trailer or pickup would carry safely.

[Pendodave]

I thought that was going to be about nomenclature of slopes on rail systems! Because it's fascinating...
: - )

Haha!
Uk railways are (as you might expect) measured as 1inX. This is measured very slightly differently to the roads, as the ratio is measured with the horizontal distance being along the line of the track, rather than directly from point a to b. Given the gentle curves and gradients on the railway, the difference is negligible in practice.
In Europe (as you might also expect) it's measured as parts per thousand, X/00, so 1 in 30 (3.3%) is 33/00.

Level is represented in all sorts of ways. I believe an infinity sign is used sometimes.

For me, gradients are no longer as important to know as they were (though still handy). When I started, we used locomotives in which power was "tapped on" (and off) in increments which could only be reduced slowly. So if you forgot to tap off before a downhill stretch, you could end up going a bit quicker than you might have liked. Nowadays, power and brakes are pretty adjustable in all directions as required.

[Cugel]

P.S. MPG for me. I have to convert litres to gallons.

What about the e-cars (or e-bikes, for that matter)? Should it be kilometres per watt-hour that's measured?

With e-cars, this might be a meaningful calculation comparable to mpg for ICE vehicles, although it wouldn't (as mpg doesn't) account for height ascent and decent of a journey. Nor vastly different load weights.

For e-bikes, the weight of the rider, not to mention their personal power output/addition, would make a km per wh for the bike alone rather meaningless. I get up to 0.75 km / wh from a near identical e-bike to that ridden by the ladywife, as we do the same route together, whereas she typically gets only 0.25 km / wh, despite me weighing 27 kg more than she does. It comes down to how much the rider employs the motor in similar circumstances compared to another rider; and how much they weigh.

I suppose you could derive some sort of benchmark figure for e-bikes that assumed a certain mean rider weight and a certain mean rider personal power output or even their FTP. But all of the factors relating to e-bike km per wh are too volatile, really. Perhaps the best you can say is that a much heavier bike with a design that pays no attention to aero dynamics, rolling resistance and so forth will have a lesser km per wh figure for the same rider than a lighter bike designed to be more aerodynamically or otherwise mechanically efficient?

[Jdsk]

Watt hours per kilometre, and the inverse, and the equivalent in miles are routinely used to describe the performance of EVs, eg:
https://en.wikipedia.org/wiki/Electric_ ... el_economy

Jonathan

[Jdsk]

...
For e-bikes, the weight of the rider, not to mention their personal power output/addition, would make a km per wh for the bike alone rather meaningless. I get up to 0.75 km / wh from a near identical e-bike to that ridden by the ladywife, as we do the same route together, whereas she typically gets only 0.25 km / wh, despite me weighing 27 kg more than she does. It comes down to how much the rider employs the motor in similar circumstances compared to another rider; and how much they weigh.

I suppose you could derive some sort of benchmark figure for e-bikes that assumed a certain mean rider weight and a certain mean rider personal power output or even their FTP. But all of the factors relating to e-bike km per wh are too volatile, really. Perhaps the best you can say is that a much heavier bike with a design that pays no attention to aero dynamics, rolling resistance and so forth will have a lesser km per wh figure for the same rider than a lighter bike designed to be more aerodynamically or otherwise mechanically efficient?

It depends what you're trying to measure. Are you looking for a single figure that describes the eBike? Or a momentary figure for a particular load, gradient, wind speed, mass of rider, degree of assistance etc? Energy/distance (or its inverse) is an appropriate measure for the latter and for comparisons.

Jonathan

[Jdsk]

PS: The SI symbol for the watt is an uppercase W. I don't know why it's so often written as lowercase.

[Cugel]

...
For e-bikes, the weight of the rider, not to mention their personal power output/addition, would make a km per wh for the bike alone rather meaningless. I get up to 0.75 km / wh from a near identical e-bike to that ridden by the ladywife, as we do the same route together, whereas she typically gets only 0.25 km / wh, despite me weighing 27 kg more than she does. It comes down to how much the rider employs the motor in similar circumstances compared to another rider; and how much they weigh.

I suppose you could derive some sort of benchmark figure for e-bikes that assumed a certain mean rider weight and a certain mean rider personal power output or even their FTP. But all of the factors relating to e-bike km per wh are too volatile, really. Perhaps the best you can say is that a much heavier bike with a design that pays no attention to aero dynamics, rolling resistance and so forth will have a lesser km per wh figure for the same rider than a lighter bike designed to be more aerodynamically or otherwise mechanically efficient?

It depends what you're trying to measure. Are you looking for a single figure that describes the eBike? Or a momentary figure for a particular load, gradient, wind speed, mass of rider, degree of assistance etc? Energy/distance (or its inverse) is an appropriate measure for the latter and for comparisons.

Jonathan

I'm not looking for anything. As you may recall, I feel that vast reams of data about things is often of little or no utility except to the obsessive counters of beans and other countables.

[Cugel]

PS: The SI symbol for the watt is an uppercase W. I don't know why it's so often written as lowercase.

To annoy pedants?

[sjs]

Watt hours per kilometre, and the inverse, and the equivalent in miles are routinely used to describe the performance of EVs, eg:
https://en.wikipedia.org/wiki/Electric_ ... el_economy

Jonathan

Watt hours per mile for me. Anything between 200 and 300, depending. Probably we should be forced to use J per m.

[Jdsk]

Watt hours per kilometre, and the inverse, and the equivalent in miles are routinely used to describe the performance of EVs, eg:
https://en.wikipedia.org/wiki/Electric_ ... el_economy

Watt hours per mile for me. Anything between 200 and 300, depending. Probably we should be forced to use J per m.

Yes, it's a useful measure and it's always interesting to hear how EV users are taking it up.

Jonathan

PS: Yes, SI would be J/m. But craft units are often useful pragmatic and/or temporary solutions. As long as they're traceable to SI!

[nirakaro]

The two common methods for expressing slope on roads are both ways of describing the tangent of the angle of inclination.

Splitting hairs, but I'd have thought the sine would more useful, to give the actual distance pedalled. Though how steep would it have to be to make a difference?

[Jdsk]

The two common methods for expressing slope on roads are both ways of describing the tangent of the angle of inclination.

Splitting hairs, but I'd have thought the sine would more useful, to give the actual distance pedalled. Though how steep would it have to be to make a difference?

I'd guess that the tangent is more commonly used because it fits more easily with surveying methods. But the sine has been used on rail systems.

...
Though how steep would it have to be to make a difference?

The small angle approximation:



0.3 rad ≅17°≅ 30%

Jonathan

[sjs]

The two common methods for expressing slope on roads are both ways of describing the tangent of the angle of inclination.

Splitting hairs, but I'd have thought the sine would more useful, to give the actual distance pedalled. Though how steep would it have to be to make a difference?

I used to think that slope was indeed a measure of sine not tangent, but apparently not. Sine would be more natural, both because distance along the slope is more easily measured than along the horizontal, and because things that matter, like the force acting against you on the slope, are proportional to sine, not tangent. As mentioned upthread, it seems they do it properly on the railways.

[DaveReading]

PS: The SI symbol for the watt is an uppercase W. I don't know why it's so often written as lowercase.

The capital letter of course reflects the fact that the unit is named after a person.

Fortunately ee cummings wasn't a scientist or engineer.