B.H.P.

My understanding is that Watt first estimated the output power of a horse, and used it to define a unit of power.  While the Prony brake predated Watt, everyone measuring power used their own units.  Later, people found that Watt was way off on his horse power estimate.  Story I heard was several groups started measuring power of horses, and got together and decided on a value.  However, I never heard/read any details.

Sounds like a neat grad student project to look into this and make details more easily found.

And brake horsepower (BHP) is the useable power, which discounts friction losses and such through the engine and drivetrain.

So yes, that's the power that makes motorheads happy.

Hey,RealG 

    Then it doesn't stand for Basically Happy Person?? Darn!

    I already knew about the B.H.P mechanical thing, I think, Developed by"Watt"You Say, Oh no, that was missileman-2,  watt said that!

Hey wait TB, you're a boat guy!  You know SHP right?  Same-same.  

Real G

And brake horsepower (BHP) is the useable power, which discounts friction losses and such through the engine and drivetrain.

So yes, that's the power that makes motorheads happy.

 

As opposed to Indicated Horsepower (IHP), which was measured with a pressure gauge.  It was computed by cylinder pressure, rpm, bore and stroke. So it was really more of a theoretical power.  Watt felt that customers woul prefer to know actual produced power- it was sort of an advertising thing.  So he advertised BHP.

 Ah Yes!

       Good Old Shaft Horsepower! Didja know? SHP could also be affected by something as simple as the shape of the Petal(That's what's they're actually called) on the prop. Blades is what everyone calls them. Because when spinning they will cut ya! 

        The Math for shaping a Petal is so convoluted it takes a full week even today to come up with a prop that will give the desired or required SHP when it starts spinning( The shaft, that is(. At  knots, Given the prop style it may result in this order given on the bridge, 252 Turns for 24  if you please!) It is a common ( Or used to be ) order. Midway down, On the base of the Engine telegraph there was a box Just below the Bell Shift that you turned the knobs entered the turns required, and the engine room repeated it ,to acknowledge the order

         Most folks are unaware that it used to take a half page of recorded notes in the log to cover a speed change order! It wasn't just lets go faster! It was a concise order from the Captain to the Officer of the Deck to the Quartermaster to the Helm, Engineman and Then, they repeated the order back acknowledging they heard it, Then transmitted to the Engine rooms. Boiler-rooms, and Repeat back to the Bridge!

         It wasn't like today where one or two men held all that power in a joystick! And your prop is in a ring that can rotate 360 degrees, There-by doing away with the helmsman and the engineman positions on the bridge! Right Mortimer, The guy that steers ain't there no more! The Selfsame Joy-Stick for speed also is used for turning Just like a Video Game. One control does it all!