Talk:Horsepower

Mushy history
In the History section we have three different stories of how Watt came up with 33,000 ft⋅lbf/min. It's possible 1 and 3 are the same story, but 2 is obviously different. What we don't say, and I would like to have clarified, is whether these are competing stories by different historians, or multiple experiments by Watt used to confirm his definition of the horsepower. Or something else. Just listing the three and leaving it at that leaves me hanging.
 * 1) 12 ft mill wheel, 144 turns per hour, 180 pounds
 * 2) pony lifting 220 pounds in four hours times 1.5
 * 3) brewery horse producing 32,400 foot-pounds per minute

Also I don't understand how the brewer choosing his strongest horse and asking for an engine that produces the same amount of power is a "trick." Can we clarify this? GA-RT-22 (talk) 17:29, 4 April 2021 (UTC)


 * The brewery horse (3) is explicitly marked as a legend, not as a fact. The 'trick' mentioned is that the Watt agreed to match the output of a horse and the brewery owner then supposedly used his most powerful horse instead of an average horse. But this story (if true) is about an installation, not about the determination of the horsepower unit.
 * Watt's early investigations started with a pony, and he then added 50% to get a rough figure for a horse.
 * A horse on a mill of specific dimensions with a specific formula is his actual figure.
 * So, the article is correct in all points. Of course, wording can always be improved and suggestions are welcome.  Stepho  talk 02:09, 5 April 2021 (UTC)

That is not at all clear from the article. Also seems fishy that he should have arrived at the same figure based on an obviously rough approximation like "a horse is 50÷ stronger than a pony", so they can't very well both be true Mike F (talk) 10:26, 23 May 2021 (UTC)

Since both stories are based on different sources, we can at the very least say that so far we don't at the moment have a source for Stepho's claims about the supposed relationship of the two? (sorry, can't edit on phone apparently) Mike F (talk) 10:32, 23 May 2021 (UTC)


 * Also Stepho is wrong about 3) being a legend, or if it is, that's not clear from the article. There are two separate stories in the article, one about "a 'brewery horse' could produce 32,400 foot-pounds" sourced to Kirby, the other about "Watt's first customers, a brewer" sourced to Popular Mechanics. The former is story 3), and the latter is a legend. GA-RT-22 (talk) 13:31, 23 May 2021 (UTC)
 * It seems like both of the sources cited for Watt's calculation of horsepower are secondary sources that do not cite any specific evidence for their claims. On page 354 of "James Watt and the steam engine" by Dickinson and Jenkins, they quote a book from 1782, which provides one version of this computation, based on information from a Millwright named Mr. Wriggley. Confusingly, the calculation seems to have been approximate, in that the figures of a 24 feet diameter circle and a rate of 2.5 turns per minute are assumed, but the value of pi used was seemingly 3.0, giving an estimate of 24*3*2.5=180 feet / minute. This book is available and online here https://babel.hathitrust.org/cgi/pt?id=dul1.ark:/13960/t17m6ks7f&seq=524&q1=33,000&start=1 Atismia (talk) 19:05, 3 December 2023 (UTC)

Section 2 (Calculating Power) is all wrong
The opening statement of the section is wrong. Power is force times velocity, or torque times angular velocity; that notion is not constrained to torque and angular velocity being expressed in coherent or in any units, for that matter.

But then, this just brings me to: the section as a whole is entirely confusing; the page is talking about Horsepower (a specific unit of power, and not power itself), but then it goes about calculating power (making mistaken claims about the torque and angular velocity being required to be in certain units). The statement after the first formula is also incorrect: one does not require a factor;  the calculated power is the calculated power. The statement would be correct if it was talking about calculating power in Watts; but then, again, the whole section is confusing, as it is talking about power (not Horsepower, which is what the page is about), and to make things worse, in the Horsepower page, the calculations for power start with the assumption that the calculation must result in Watts?

I think the section should either talk about Calculating Horsepower (not sure that's the correct phrasing; in any case, Calculating power in HP units), or, if talking about Calculating power, then let's rewrite to avoid the confusion about the units; Power is torque times angular velocity, and then go on about "if we want the result expressed in XXX units, then ... " (perhaps particular examples of units)

Then again, on third thought.... Why would this page need a section on calculating power? There is a Wikipedia page for power, where it shows how it is calculated. Since we would never calculate power to result directly in HP (since no-one uses a unit of force that corresponds to 550 pound-force), then why talk about this? IMHO, the only important thing (related to power and other units) in a page about 'Horespower' is the conversion factor to/from other units (notably, the Watt).

Cal-linux (talk) 17:43, 21 May 2021 (UTC)


 * Agreed, and I have removed the section, which is also unsourced. This has been bothering me for a while, but it was more of a nagging feeling and hadn't really risen to the level of an objection I could articulate. Thank you for putting this in to words. GA-RT-22 (talk) 17:55, 21 May 2021 (UTC)

Fiscal horsepower in France
This article seems to say that France no longer uses the formula given in the "Tax horsepower" section. Also I don't see why we're giving the formula for France and not for any of the other 200 countries in the world. We should just describe the concept and not give any formulae. Anyone interested in the details can click through to Tax horsepower. GA-RT-22 (talk) 13:24, 22 May 2021 (UTC)

PS in EU
An anonymous editor removed this: "In 1972, the PS was replaced by the kilowatt as the official power-measuring unit in EEC directives." The edit summary says "Might be true, but is an unreferenced claim as the cited document does not exist." The document certainly does exist. Here is the title and reference:. I have not read it, but it does exist. GA-RT-22 (talk) 19:17, 5 November 2021 (UTC)
 * If you took the trouble to click on the provided citation, you will discover that it says that the document does not exist. You have thus reverted an uncited claim, removal of which does not have to be discussed on the talk page. 81.157.153.208 (talk) 14:31, 6 November 2021 (UTC)
 * The wording is misleading. It doesn't mean that the document "Council Directive 71/354/EEC" does not exist. It just means that the url is 404. On Wikipedia we call that a "dead link". We do not remove content just because of a dead link. See Link rot. GA-RT-22 (talk) 14:46, 6 November 2021 (UTC)
 * There is no mention of an error 404 or any hint that the document used to exist but no longer does. The wording is, "The requested document does not exist.". That is not open to misinterpretation, its meaning could not be clearer. You may not have read the document at the link that you provided, but you did miss the bit that the document is no longer extant having been repealed so is not a valid cite anyway. 81.157.153.208 (talk) 17:38, 6 November 2021 (UTC)

Organisations sometimes change the URLs that documents reside at - a pain to us but we have no control over it. We can normally assume that the link worked when it was first added (although typing or cut/paste errors can happen). If the organisation changed the URL then we will see the "not exist" error. This does not mean that the document does not exist - it means that this URL does not point to the document. Computers are dumb, so they can't make the intellectual leap between URL not existing and document not existing. GA-RT-22 has nicely found the corrected URL, so the solution is to update the article with the correct link.  Stepho  talk 00:08, 7 November 2021 (UTC)
 * I just (belatedly) added an archived link and removed the warning.  Mr.choppers &#124;   ✎  14:48, 13 August 2022 (UTC)

Horse power output in the lead
Re this edit:

"Already mentioned further down" is not a reason to remove this. Everything in the lead is mentioned further down; see WP:LEAD. Personally I would leave this in. GA-RT-22 (talk) 23:34, 29 November 2021 (UTC)


 * Fine detail of the unit is perfectly fine in lower sections but doesn't really belong in the lead. However, I'm not super dead-set against it. I still prefer it lower down but if you do put it back in the lead then perhaps reword it.  Stepho  talk 22:33, 2 December 2021 (UTC)
 * Well I'm not dead-set in favor of including it either. I'm usually a fan of short leads anyway. We've got the definition, conversion to standard units, and a bit of history, so I'll defer on this one. GA-RT-22 (talk) 22:52, 2 December 2021 (UTC)
 * How strange - a civil discussion on Wikipedia :) Thanks!  Stepho  talk 00:48, 4 December 2021 (UTC)

Definition of mechanical horsepower
We seem to have a discrepancy. In the Definitions section we say that the mechanical horsepower is equal to 745.69987158227022 watts. This was recently changed, with no explanation, from 745.6998715822702. Is this exact, or rounded? If it's approximate, shouldn't we use a wavy equals sign?

Then in the "Mechanical horsepower" section, we say that it's 745.699 watts. Again, is this exact? If so, how do we reconcile it with the differenct exact value given in the other section? If not, shouldn't it be a wavy equals? Also, if it's rounded, shouldn't it be 745.700? GA-RT-22 (talk) 19:27, 5 December 2021 (UTC)

I see this has been discussed before, at Talk:Horsepower/Archive 2. GA-RT-22 (talk) 00:57, 6 December 2021 (UTC)

The precise numbers were lost in this series of edit by :. Since we're talking about the definition here, I think we should go back to the precise numbers. Failing that, we should change the equal signs to approx equal signs. GA-RT-22 (talk) 20:56, 6 December 2021 (UTC)
 * This number is stated without any cited reference. I find it highly dubious that 14 digits of precision are warranted. I suspect this undue precision was due to an editor calculating a ratio and taking all of the digits that were presented on their calculator. Please use reputable sources.12.151.33.163 (talk) 21:35, 6 December 2021 (UTC)

I think that the unit of measure is the main problem, not its value.... It should be called HORSE ENERGY RATE or HORSE WORK RATE (at which the energy is transformed into force) and it should be expressed in J/s not W because power is synonymous with force in common languages and that can be misleading through its name and its unit of measure (W). The fluid's flow doesn't have a simmilar unrelated definition. More details in this publication: [https://marius-ciclistu.ro/pdf/The%20power%E2%80%99s%20mislead%20in%20thermal%20engine%E2%80%99s%20regard.pdf "Power is a denatured mirroring of force and acceleration in thermal engines' regard."] Marius Pantea feb.2017. (Also HP as a unit of measure has been banned from official records in the automotive industry since the '70s, being replaced by W.) — Preceding unsigned comment added by 2A02:A58:843B:A900:C1E8:37B3:BCA0:5FAF (talk) 22:15, 1 March 2023 (UTC)


 * Be aware that you are answering a discussion from over a year ago.
 * Wikipedia just reports on facts - it doesn't try to create new standards. "Horsepower" is the term used in the real world (including formally by engineers until recently), so that's the term we use.
 * Horsepower is not quite banned but certainly deprecated in favour of Watts (most countries mandate W but will allow hp as a secondary unit). The US is the main standout in keeping hp in mainstream use, even though their engineers use W. In any case, Wikipedia reports on historical terms so that people reading old books, car magazine, train magazines, etc, will be able to interpret the meaning. As the saying goes, those who don't study history are doomed to repeat it. It also helps to see where the definition of power (whether in hp or W) came from. Before James Watt there was no formal definition of power - just the fuzzy feeling of power being somehow related to strength/force/endurance.  Stepho  talk  23:38, 1 March 2023 (UTC)


 * I tried to create new paragraph but I couldn't. You said "Before James Watt there was no formal definition of power - just the fuzzy feeling of power being somehow related to strength/force/endurance.". Funny thing is that after James Watt defined power, for the majority of people, it means the same thing. Wiki should present facts. I'm not saying that this article is not useful. All I'm saying is that it is time we open our eyes. Over 200 years had passed since this marketing definition was born and it might be the time to patch it. — Preceding unsigned comment added by 2A02:A58:843B:A900:C1E8:37B3:BCA0:5FAF (talk • contribs)


 * You are not very clear. From what I can decipher, you want to rewrite the last history books for the last 200 years. Which is not WP's job.  Stepho  talk 01:14, 3 March 2023 (UTC)


 * For thermal engines, the torque on all the rpm range is more relevant than the power graph or power peak(max). In other words, power is LESS relevant than torque(force) in thermal engines. That is the patch I was talking about. PS. Even when calculating the energy, using power is less precise than using force and distance. I rest my case. Thank you. — Preceding unsigned comment added by 2A02:A58:843B:A900:9469:5682:5C3D:C708 (talk) 09:22, 3 March 2023 (UTC)
 * Hi. I found an interesting fact that power meant "ability to act or do" or "potential" in the 1770s https://hsm.stackexchange.com/a/3255/19097. So horse power meant horse ability to act or do work or horse potential. Also https://physics.info/power/ in here it sais that Watt thought of power as F*v because the energy concept was later defined in 1840 by Joule https://www.britannica.com/science/Joules-law. So the energy rate is a younger concept than power (ability to act or do | potential) is. 2A02:A58:843B:A900:5032:21CA:27F9:B0E5 (talk) 22:11, 4 October 2023 (UTC)

Reference to PferdeStärke (PS)
I was surprised not to see any inclusion of PS (PferdeStärke, literally horse power) units in the Horsepower article. PS units have gained wider scientific adoption in the EU over their less scientific hp or bhp counterpart. Williamdelany (talk) 22:24, 21 April 2022 (UTC)
 * PS is just the German abbreviation for horsepower. Germany, like most of the world uses the customary metric horsepower which is very close to the imperial hp (based on the distance between King Henry I's nose and thumb). German sources may use PS for metric as well as imperial hp, although sometimes they'll use the English abbreviation for clarity. There is a whole section devoted to the metric hp. Here is the difference:


 * 100 PS
 * 100 bhp


 * There is no reason we should use this abbreviation for metric hp, except that Germany, South Korea, and Japan all do - for somewhat unclear reasons. For many car lovers in the US (and UK), foreign cars use PS. Sadly there is no universally accepted abbreviation for metric hp, and PS is obviously inappropriate for a Portuguese or Finnish car. The best we can do with the Wikipedia conversion templates is this:


 * 125 hp-metric =125 hp-metric


 * Best,  Mr.choppers &#124;   ✎  14:43, 13 August 2022 (UTC)


 * in addition also understands "PS" as well as "hp-metric".
 * 125 PS =125 PS
 * I suspect that Japan uses the term PS due to their WWII connection with Germany, when they borrowed quite a bit of technology from Germany. Eiji Toyoda's autobiography says he spent considerable hours at that time redrawing many diagrams in metric for Toyota during that time. Korea probably copied Japan.  Stepho  talk 01:40, 14 August 2022 (UTC)
 * That's what I used to think, until I realized that Japanese sources from the 1950s use HP... did they change back once the occupation ended? It is mysterious and I haven't been able to find out. I still think "PS" is generally an ill-fitting abbreviation to use for metric horsepower but I will give it a pass on cars from those three countries.  Mr.choppers &#124;   ✎  15:55, 14 August 2022 (UTC)

NHP for turbines
The section on NHP says it's calculated from piston area and speed, which makes it sound like it would only make sense for piston engines. But turbine engines have NHP too. How is that calculated? An example is at RMS Empress of Britain (1930) which cites as its source. GA-RT-22 (talk) 23:01, 23 August 2022 (UTC)

Measurement
The first part of this section made no sense. It effectively stated:

P1 - L1 = P2 - L2

P2 - L2 = P3 - L3

P3 - L3 = P4

therefore:

P1 - L1 = P4

where:

P1 is gross power

P2 is brake power at crankshaft

P3 is power at output of transmission

P4 is power at power at wheels;

L1 is losses within the engine

L2 is losses in the transmission (gearbox?)

L3 is losses in the prop shaft, axle etc.

I have rearranged the content to the form:

P2 = P1 - L1;

P3 = P2 - L2;

P4 = P3 - L3;

I acknowledge that the expressions 'indicated horsepower', 'shaft horsepower' etc. are misnomers (should be 'indicated power', 'shaft power' etc., regardless of the units used, 'horsepower' being the unit historically used in measuring power) but I have left them in because they are in common use among some who deal with engines, hence the abbreviations 'nhp', 'ihp', 'bhp' etc. 203.23.239.198 (talk) 02:42, 25 September 2022 (UTC)

Discussion at Talk:HP Inc. § Requested move 13 May 2024
You are invited to join the discussion at Talk:HP Inc. § Requested move 13 May 2024. InfiniteNexus (talk) 19:13, 22 May 2024 (UTC)