I have often been asked how did they figure that the 10 hp Stanley is only 10 horse power? The 10 hp stanley is equal in performance to a 1930 Ford model A in most respects and the model A Ford is rated at 30 horse power. I personally have done this comparisome of cars and they are pretty much equal in weight, and performance, yet the Ford is rated at three time as much horse power. How come?



SSsssteamer

I can't recall at the moment,,But the Stanley HP was a rating,,at standard pressure and RPM,,, a standard for rating steam engines,,having nothing to do with ALAM or other gas car people,,,[ I cant recall what these were,] I think near 300rpm /100PSI,,,, Maybee Dave or George will remember,,,I recall seeing it somewhere,,,,,,,,,,, Gas cars:: most of these HP were taken from the ALAM horsepower FORUMLA , based on piston area ,, and piston speed,,[NOT RPM],,,details on this in all [?] Dykes book,,These ratings have little to do with developed HP ,, as the engines developed at a different rate from formula change,, The following is subject to checking,,1908 Packard so called ''30'' developed this at 650rpm and 84 hp at around 1250 ,,, 1925 Packard 8 developed [max] 84 hp at around 2600 ,,,The old car was faster,,, 1915 Pierce 66 hp model developed 66hp around 700rpm and 150 around 1500rpm,,,max rpm was 1800,,so says the handbook,,haha,,,Most of these engines had 4:1 compresson,, One of the old timers claimed the 10hp Stanley could put out 90 hp,,,and the 20 hp was 150,,,Hopefully George may comment on this,,,,later as time permits,, Cheers Ben

My belief has always been that Stanley HP was always rated by boiler size. Take the Model H, in 1906 it was rated at 15 HP. Later on it was rated 20 HP with the same engine. The only thing that changed was the gears and boiler size. The 15 HP had 60:60 gears and the 20 HP had 56:60 and a 23” boiler. Same engine size.

Rolly



Edited 1 time(s). Last edit at 07/19/2006 01:20PM by Rolly.

Pat,
Stanley rated the 10HP as 8HP on the dyno, the 20HP at 15HP and the 30HP at 25 HP. Think Rolly is correct as it was related to boiler output with standard firing rate and feedwater being pumped/replaced. With the feedwater shut off and running on the water reserve in the boiler the 8 would become 12, the 15 23 and the 25HP become 37HP. This is without drawing down the pressure. The 20HP Stanley can momentarily(with feedpumps off and drawing on boiler reserve for a minute or so) can produce over 80HP. The standard 30HP car with its factory firing rate of 6GPH could put out over 120HP. The 1906 racer, with its 11+ GPH firing rate could put possibly 180HP if the engine didn't break. Remember a steamer will put out near its rated maximum horsepower over a large RPM range where a gas car only at its peak horsepower rpm.
Take a look at the Walton Doble book page 95 that has road force graphs and a horsepoer graph for one of the German lorries and you can see how much more area under the first graph a steam unit has over gas engine with all its transmission shifting. Plus automotive gasoline engines may only put out there rated horsepower for a very short time before rising engine temperatures lead to detonation and loss of power. Steamers love getting hotter!!
Best, George

Thank you Ben and George. I hopefully can give the right answer next time a person asks why steam hp is rated so low for the work that it actually does. The answer will be that "steam horse power for a steam engine is rated entirely different than the horse power which is calculated for the Otto Cycle."

Be interesting to put a Stanley on a rolling road but it would take a lot of time to investigate hp with and without drawing down boiler pressure, with and without pumps etc - shop might get a bit steamed up!

Has anyone tried it?

Mike