Talk:Dynamometer

message: But what was Gustave-Adolphe Hirn's pandynanometer? It does exist  Cutler 11:08, 7 March 2006 (UTC)
thread_title: Pandynanometer

message: What is an eddy current dynamometer? --Gbleem 04:22, 1 June 2006 (UTC)
replies: text: See answer below by =Motorhead. I have added eddy current or electromagnetic brake to the article under heading: Types of absorption units. --C J Cowie 16:27, 1 June 2006 (UTC)
thread_title:  Eddy current? 

message: I work at an engineering company and i am under the impression that William Froude invented the dynamometer. This article indicates it was Charles Babbage. Charles' page indicates he did a lot of work with computers, which were called 'engines' but nothing to do with dyno's. Could you confirm your source for this?  :o)
:Gaspard de Prony invented the de Prony brake in 1821. The de Prony brake (or Prony brake) has been considered to be one of the earliest dynamometers, but I don't know if it is claimed to be the first. C J Cowie 14:15, 23 June 2006 (UTC)
replies: text: Since William Froude was born in 1810, the invention of the Prony brake must have predated whatever type of dynamometer he invented.C J Cowie 14:27, 23 June 2006 (UTC)

text: According to http://www.froudehofmann.com/about_1.htm, William Froude invented the hydraulic dynamometer in 1877 and Heenan & Froude was established and produced the first commercial dynamometers in 1881. C J Cowie 14:37, 23 June 2006 (UTC)

text: I have found a couple of references that indicate that, in about 1838, Charles Babbage built "what must have been the first example of a dynamometer car" for testing railroad engines. The information about Babbage needs to be moved to the dynamometer car article and the information about de Prony and Froude put in this article. C J Cowie 22:49, 23 June 2006 (UTC)

text: I have moved the Charles Babbage material to Dynamometer car and added a history section to this article with information on the de Prony brake and the invention of the hydraulic dynamometer by William Froude. --C J Cowie 00:40, 24 June 2006 (UTC)
thread_title:  Inventor of the Dynamometer 

message: This type uses magnetic flux to apply load to the engine. I thought i'd let you add it though to maintain the flow of the article. It is 'Electric' in design but does not have the motoring capacity. —Preceding unsigned comment added by Arnie1066 (talk • contribs) 
Froude made a "regenerative" hydraulic motoring dynamometer in the early '80s that was installed at Ford Dunton, UK.  The engine under test drove an off-the-shelf fixed displacement swash plate pump for which the casing torque reaction could be measured by a load cell.  The hydraulic hoses were hooked to a similar but variable displacement swash plate pump drive by a synchronous AC motor of around 300 hp.  Clearly by varying the variable pump's swash plate setting torque could be applied either way to the test engine, transferring power to and from the electric grid.  — Preceding unsigned comment added by 125.237.51.60 (talk) 00:22, 5 November 2011 (UTC)
thread_title:  Another type of Dynamometer - Eddy Current 

message: what about a reference to the dynamometers that are attached to the axle, removing the wheels to proceed with the testing.  Maybe someone can mention those. --Cirilobeto 22:51, 27 August 2006 (UTC)
thread_title:  Another type of dyno 

message: What about dynamometers that use a prop or fan and air? --Gbleem 15:31, 5 October 2006 (UTC)
replies: text: They are mentioned in the types section.--=Motorhead 14:25, 6 October 2006 (UTC)
thread_title:  prop dynamometer 

message: "Dynamometer" is also the name of a device for testing a person's grip
strength.  I don't know enough about it to create a separate article,
and I can't think of any good way to integrate it into this article.
Keith Lynch 17:26, 15 October 2006 (UTC)
thread_title:  Another usage of the word 

message: Time and again I encounter the claim that power cannot be measured directly on a dynamometer, which is simply rubbish.  Now I find the same thing on Wikipedia, which is rapidly becoming the universal repository for disinformation.  This article makes this claim:
"Only torque and speed can be measured Power must be calculated from the torque and speed figures according to the formula:"
This is rubbish.  It categorically ignores inertial dynamometers as a class.  With inertial dynamometers, rotational speed is repeatedly sampled in order to deduce angular acceleration, and power is deduced from angular acceleration and from the inertial moment of the drum.  Moreover, it is not at all difficult to visualize a dynamometer that is equivalent in effect to a brake dynamometer, but would operate not by using a brake per se, but would accumulate energy in a form other than heat, and would do so in a manner in which the rate of increase of that more usable form of energy can be regulated and measured directly.  For example, if the drum is replaced with spinning masses held in place using arms of variable, controllable length, the inertial moment can thus be regulated, with the effect being the same as a brake dynamometer in that the steady-state power output is measured, by multiplying together the steady-state angular velocity and the inertial moment.
It is thus demonstrably true that the statement that I quoted above, is patently false.  Moreover, the introductory definition is patently false:
"A dynamometer ... is a machine used to measure torque and rotational speed (rpm) from which power produced by an engine, motor or other rotating prime mover can be calculated."
This definition contains arbitrary, unsupportable presumptions about the basic nature of how physical quantities are measured.  It states outright that power is not measured directly, but is rather calculated from torque and the rotational speed.  This is incorrect on multiple levels.  If it is meaningful to distinuish between that which is measured directly and that which is measured indirectly, then neither torque nor rotational speed are measured directly.  You measure distance and time in order to measure speed, and you measure distance and force in order to measure torque.  The distinction between that which is measured directly, and that which is measured indirectly, is illusory and meaningless.  And that is in addition to the fact that it is simply not true that it is necessary to first measure torque in order to measure power, not even in the case of brake dynamometers as a meaningful class.  As such, the summary definition is absurdly incorrect.  It should simply say that a dynamometer is an apparatus used to measure the instantaneous rate at which a system is performing usable work.
This article also misrepresents the most important distinction between classes of dynamometers.  Dynamometers fall into two general classes: those which measure steady-state power, and which give results that are uninfluenced by the tendency for the system to absorb energy, and those which measure power dynamically, which give results that are influenced by the tendency for the system to absorb energy.  Inertial dynamometers, which are not even mentioned in this article, give results that are influenced by the tendency for the engine under measurement to absorb energy in the form of internal kinetic energy, the amount of which depends on its aggregate inertial moment and its instantaneous rotational speed. --- Preceeding unsigned commentary by:  Terrible barbarian 11:25, November 15, 2006 
:"With inertial dynamometers, rotational speed is repeatedly sampled in order to deduce angular acceleration, and power is deduced from angular acceleration and from the inertial moment of the drum." -- In other words, speed is measured repeatedly. Acceleration is calculated from successive values of speed data samples and the time interval between speed samples. Instantanious torque is calculated from acceleration and the inertial moment of the drum. Instantanious power is calculated from instantanious speed and torque. Power is not measured directly it is "deduced" AKA calculated. Speed and torque may not actually be measured directly, but there are transducers that convert such things as time and force measurements to speed and torque indications. -- C J Cowie 19:18, 15 November 2006 (UTC)
replies: text: Although I don't believe the lead paragraphs of this article are "blatantly incorrect," I agree that the it is too focused on measurement of speed and torque. A more general statement might be better. "A dynamometer is a machine that is used to apply a load in a controlled way to a prime mover such as an engine for the purpose of evaluating the performance of the prime mover." -- C J Cowie 21:35, 15 November 2006 (UTC)
thread_title:  The introductory definition is blatantly incorrect 

message: Many types of AC and DC motors can function as either motors or generators. Permanent magnets are not required. —The preceding unsigned comment was added by C J Cowie (talk • contribs) 15:24, 7 December 2006 (UTC)
thread_title: Re erroneous edit

message: I wish the person who found this article rubbish would spend as much time replacing the article as criticizing it; then there would be real benefit and it would make Wikipedia less of a repository of misinformation, as the writer terms it. The comments in that notice strike me as sound and valuable observations--please share them publicly!
My own observation is that dynamometers have applications for testing forces in lots of contexts not mentioned in the article--springs spring to mind.
If I had better technical knowledge I would contribute, rather than adding my own ignorance to what appears, and I can only add these observations, which I hope can be constructive.
BLATANTLY INCORRECT  —Preceding unsigned comment added by 69.134.70.213 (talk) 15:39, 21 September 2007 (UTC)
thread_title:  Accuracy and completeness 

message: Can anyone explain what an 'exterequire' is?  I am guessing that this is an artifact of a bad edit back in May 2008.  I'd gladly correct it but I'm not too sure what the initial intent was.  Assuming that this is the case, I will just go ahead and correct it. Cam Finnigan (talk) 20:53, 7 September 2008 (UTC)
thread_title:  Eddy Current Brake Composition 

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thread_title:  External links modified