Misunderstood terminology

General cycling advice ( NOT technical ! )
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NATURAL ANKLING
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Re: Misunderstood terminology

Postby NATURAL ANKLING » 18 Mar 2018, 10:53pm

Hi,
Power is force x distance in a time normally an hour.............electrical power volts X amps also watts is also an hour.

Torque is a force at a radius.............normally quoted at a particular rpm.................it might sound small but at several times a second will pull a car.

Static torque is just that like undoing a bolt with a spanner. Newton Metres if you like SI.
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BigG
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Re: Misunderstood terminology

Postby BigG » 18 Mar 2018, 11:07pm

MickF is close, but not quite right. Work is torque (or force) multiplied by distance. Power is work divided by time. These are not definitions, just indications of the calculation process.

Airsporter1st
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Re: Misunderstood terminology

Postby Airsporter1st » 18 Mar 2018, 11:29pm

nirakaro wrote:It's the nature of the journalist's job that they're constantly writing about subjects they don't know much about. If I read an article about anything I have some expertise in, I'll find errors in it. And if there are any numbers or sums – they're invariably wrong!


Quite true and the fact is that if you can spot errors in those pieces where you have some expertise, then you can be sure that others will too - meaning that there is nothing in the media in which you can have any great deal of confidence.

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The utility cyclist
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Re: Misunderstood terminology

Postby The utility cyclist » 19 Mar 2018, 12:01am

Mick F wrote:
Brucey wrote:I think that if you ordered a pint of beer and it came over 2/3rds of a pint short, you would resent being called a pedant for pointing it out..... :wink:
We were in a pub yesterday late afternoon and there's a chap in there we know, who is a staunch Brit and anti EU and anti metrication etc.

I wound him up a bit showing him the CE mark on the pint glasses and how they are now smaller pints than when we had the crown on them.
I told him that as the inch is now smaller at 25.4mm (when in the past it was slightly more) it must mean that the pint is smaller too.

:lol: :lol:

the inch is the same, it's the metric that is out :lol: 1 inch is still 2.540005080010160020320040640081280162560325120650241300
48260096520193040386080772161544323088646177292354584709
16941833883667767335534671069342138684277368554737109474
21894843789687579375158750317500635001270002cm recurring
the 2.54 was agreed by the British in the 30s IIRC and the septics followed suit some time in the 40s. The old foot still referred to as a 'US Survey foot'
My old guinness glasses have the pint mark on the side and room for a decent head, now you get short changed in every pub so you're actually not far wrong tbh.

the snail
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Re: Misunderstood terminology

Postby the snail » 19 Mar 2018, 12:14am

sjs wrote:Power (W) = torque (Nm) X rpm / 60 (to get to revs per second) X 2 Xpi, because torque = force X radius so power is force X speed of foot

Or put another way, in SI units the rotational speed is given in radians per second

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Mick F
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Re: Misunderstood terminology

Postby Mick F » 19 Mar 2018, 6:21am

The utility cyclist wrote:the inch is the same, it's the metric that is out :lol: 1 inch is still 2.540005080010160020320040640081280162560325120650241300
48260096520193040386080772161544323088646177292354584709
16941833883667767335534671069342138684277368554737109474
21894843789687579375158750317500635001270002cm recurring
the 2.54 was agreed by the British in the 30s IIRC and the septics followed suit some time in the 40s.
The inch is now 25.4mm exactly having been reduced from 25.4000508 (ish) in the 1930s.

It would be nice to think that they increased the metre to suit us Imperial folk. :D
Mick F. Cornwall

thirdcrank
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Re: Misunderstood terminology

Postby thirdcrank » 19 Mar 2018, 6:55am

The utility cyclist wrote: ... now you get short changed in every pub so you're actually not far wrong tbh.


I'd have said short measure but the point remains the same. The brewing industry, having convinced the authorities that beer drinkers somehow demand that one fluid ounce in every pint should be froth rather than beer, often now cannot even fill a glass to the brim with the froth. You can ask for a top up but why should every visit to a pub include this unleasantness?

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Re: Misunderstood terminology

Postby Vorpal » 19 Mar 2018, 8:15am

tatanab wrote:
Mick F wrote:
sjs wrote:
No!
Well, come on then ............. :wink:

Not maths, just plain simple English.
Power is torque times rpm. There can be no time element in power because I can put out 100 Watts for an hour or for 10 hours, it is still 100 watts.

rpm = revolutions per minute

minute is the time element
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Bmblbzzz
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Re: Misunderstood terminology

Postby Bmblbzzz » 19 Mar 2018, 8:54am

foxyrider wrote:
Bmblbzzz wrote:
tatanab wrote:Some misunderstandings are harder to fathom - such as the work colleague a few years ago who insisted that "evens" was a different speed according to the distance being raced. He understood that it was 20 mph at 10 miles, but thought it was 18mph at 25 miles, above that he did not know. It was a few years of time trialling before he accepted that "evens" is always 20mph.

I know (because I've gathered from things said and written) that evens is 20mph, but I don't understand the concept that lies behind the figure. What does it represent? Why is it 20mph? If, as I vaguely think, it represents a "decent minimum" time trial speed, then I can't understand why it does not change with distance (or even as average times drop compared to historic standards).

My understanding is that it refers to taking an even number of minutes to cover 25 miles when anything even approaching an hour was rare! So evens is always 3min/mile. So 30mins for a 10, 1.15 for 25, 2.30 for 50 and 5.00 for 100 miles. I never questioned this as my grandfather who was racing in the 30's always referred to evens in those terms as did my parents and everyone else I came into contact with in riding TT's over a 3 decade period.

I think the terms used today are fast and flippin' fast!

Okay, thanks. :)

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Patrickpioneer
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Re: Misunderstood terminology

Postby Patrickpioneer » 19 Mar 2018, 9:22am

I think there is just too much to know in our modern world, the big problem is when myth becomes fact.

Marcus Aurelius
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Re: Misunderstood terminology

Postby Marcus Aurelius » 19 Mar 2018, 3:24pm

Vorpal wrote:
tatanab wrote:
Mick F wrote:Well, come on then ............. :wink:

Not maths, just plain simple English.
Power is torque times rpm. There can be no time element in power because I can put out 100 Watts for an hour or for 10 hours, it is still 100 watts.

rpm = revolutions per minute

minute is the time element


If you want to know how much effort went into your ride, you have to be looking at the time component ( duration of the ride )not just the power you were producing,which is the product of your Cadence ( usually measured with a cadence sensor) and the torque ( measured by strain gauges, in the cranks, or pedal axles / bodies). The metric you want, is the number of Joules ( product of Power and ride duration ).

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Re: Misunderstood terminology

Postby Vorpal » 19 Mar 2018, 4:51pm

Marcus Aurelius wrote:
Vorpal wrote:
tatanab wrote:Power is torque times rpm. There can be no time element in power because I can put out 100 Watts for an hour or for 10 hours, it is still 100 watts.

rpm = revolutions per minute

minute is the time element


If you want to know how much effort went into your ride, you have to be looking at the time component ( duration of the ride )not just the power you were producing,which is the product of your Cadence ( usually measured with a cadence sensor) and the torque ( measured by strain gauges, in the cranks, or pedal axles / bodies). The metric you want, is the number of Joules ( product of Power and ride duration ).

I don't actually. I don't even have computers on my bikes. I was just pointing out that strictly speaking, rpm contains an element of time. 8)
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom

BigG
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Re: Misunderstood terminology

Postby BigG » 21 Mar 2018, 11:24pm

Power most certainly does have an element (strictly a dimension) of time despite tatanab's statement. It is work that has no time component. The work done to climb a hill slowly (to allow air resistance to be ignored) is the same whether it takes 1 hour or 10 hours. It is the power that varies being 10 times greater in the faster climb. Tatanab's 100 Watts would require 100 Watt hours of work if maintained for 1 hour. It would require 1 kW hr if maintained for 10 hours. The whole purpose of variable gears is to allow us to match an acceptable work rate to an acceptable cadence.

Marcus Aurelius
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Re: Misunderstood terminology

Postby Marcus Aurelius » 24 Mar 2018, 6:17pm

BigG wrote:Power most certainly does have an element (strictly a dimension) of time despite tatanab's statement. It is work that has no time component. The work done to climb a hill slowly (to allow air resistance to be ignored) is the same whether it takes 1 hour or 10 hours. It is the power that varies being 10 times greater in the faster climb. Tatanab's 100 Watts would require 100 Watt hours of work if maintained for 1 hour. It would require 1 kW hr if maintained for 10 hours. The whole purpose of variable gears is to allow us to match an acceptable work rate to an acceptable cadence.


Different equations. Power being the product of Torque and cadence ( rpm ) minutes ( or seconds ) being the time element, which is a separate animal ( yet attached to ) the measure of effort, which is the product of Power ( Product of Torque and Cadence) and the duration of the applied power. Confusing isn’t it? :lol:

Mike_Ayling
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Re: Misunderstood terminology

Postby Mike_Ayling » 25 Mar 2018, 10:14am

Clipless pedals!

Mike