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Calculate the horsepower of a steam engine?

mgt3

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I'm trying to figure out how to calculate the horsepower of a steam engine.

With an ICE, the power of an engine's design is determined by the energy of the fuel, the fuel flow, and the engine's thermal efficiency. Is there an analogue equation to calculating the horsepower of a steam engine?

It's relatively easy to make 300 horsepower with an ICE V8. Can the same be done with a steam engine? Is there a practical limit to the amount of power steam engines produce?
 

gibbykart

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Age
24
Last Subscription Date
08/22/2017
HP=PLAN/33,000

Indicated Horsepower=P*L*A*N divided by 33,000 (the number foot pounds per minute determined by James Watt)
P=Pressure PSI
L=Inch of stroke (double if double acting)[this what I was told by a old navy steam engine operator]
A=Area in square inches of the face of the piston
N=Number of strokes per minute.
Hope this helps. -Mike
 

Bill Hazzard

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08/28/2008
The largest reciprocating steam engines that I know of made about 20,000 HP, so 300 is nothing.
 

mgt3

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Excellent! Thank you! This is exactly what I was looking for. :)

---------- Post added at 07:54 PM ---------- Previous post was at 07:51 PM ----------

20,000 horsepower?! Could a 300 horsepower steam engine ever fit inside an automobile?
 

Randy Musselman

Registered
In the formula, you would quickly reach limits with the LAN variables which leaves the possibly biggest opportunity with P....it may a bigger problem to get a big enough boiler in the car which has a burner heat rate large enough to reach 300 hp.....Throwing efficiency out the window, look at the power density of the flash steam engines used on the model tethered hydroplanes....if you scaled that up it would be terrifying.....serious blow lamps! Get the Experimental Flash Steam book from Camden Miniature Steam services in the UK.....interesting content. Then the key is to not burn the car up in the process!

---------- Post added at 08:28 PM ---------- Previous post was at 08:19 PM ----------

Blow lamp madness.....

https://m.youtube.com/watch?v=CJBG7k3DIms
 

Gary K

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Last Subscription Date
07/15/2019
Steam Engine Horsepower

Example: An engine with a 9” bore, a 10” stroke, a speed of 250 rpm, and 150 lbs. boiler pressure – The size of a 50 H.P. CASE steam engine.
P = 50% of 150 = 75 lbs.
L = 10 / 12 or .833 feet.
A = 9 x 9 x .7854 = 63.617 square inches.
N = 250 x 2 = 500 power strokes per minute. (This is for a double-acting engine, for a single-acting engine, power strokes are the same as the revolutions.)

75 x .833 x 63.617 x 500
----------------------------- = 60.2 indicated horsepower
33,000

Since this is the power developed by the steam in the cylinder, it represents the indicated horsepower, which is greater than the brake horsepower by about 10%. Subtracting 10% we have: .10 x 60.2 = 6.02 ( 60.2 – 6.02 = 54.18 or rounded off to 54 B.H.P.)
 

cyberbadger

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Last Subscription Date
11/13/2013
mgt3 said:
Could a 300 horsepower steam engine ever fit inside an automobile?
It could be done "fairly" easily in theory, but that's not the full story.

The PLAN calculation is just one calculation.

The full story is the difference between Internal Combustion and External Combustion.

For IC's that's all you need - the engine. For EC's - You need an Engine + some type of boiler: fire tube/water tube/flash steam/etc.

Just look at a steam railroad locomotive - the actual engine(s) on it are tiny compared to the boiler.

Another part is almost all practical steam engines are 1-strokes (double acting). So a 2 cylinder steam engine is like a 8 cylinder gasoline/diesel 4-stroke engine in terms of power strokes per revolution.

Also if you think diesel engines develop a lot of torque, steam engines kick diesels in the head. :) (I like diesels a lot)

Doesn't mean you can't make a fast lean car/motorcycle with steam if you want to...

http://www.smokstak.com/forum/showthread.php?t=138575

-CB
 

JBoogie

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38
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11/12/2013
Ahhh,
Knew it wouldn't be long before our resident philosophaster would chime in. Thanks CB!
 

cyberbadger

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11/13/2013
Ahhh,
Knew it wouldn't be long before our resident philosophaster would chime in. Thanks CB!
Thanks for the witty ad hominem attack. :D

Do you care to actually reply about why there is anything wrong with my post?

-CB
 

gibbykart

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24
Last Subscription Date
08/22/2017
CB I wouldn't call a locomotives engines small, they just look small compared to the actual monstrosity of the engine size but Just look at Pere Marquette 1225's engines, she has 2 of them each at 26 inches by 34 Inches, much bigger than most engines that we on the forums own. Or the Union Pacific Big Boy's with 4 Cylinders each 23 3/4 inches by 32 inches. The Big boy also produced 6000 draw bar horse power.

I did the calculations for a Big Boy,based on a 300 PSI(/2=150) normal working boiler pressure, and using the optimal speed of 35 mph (Found on Wikipedia) I figured out that it goes .58 miles every minute so that means 3062 feet and the wheels are 68 inches*3.14=214/12= 17.83 feet in circumference so that means 172 strokes per mile times 2 for double acting.

SO:
150*32*443*344=731481600/33000= 22000 IHP per cylinder at peak performance, correct me if I am wrong but that is one powerful engine, and has a combined IHP of 88,000 at 35MPH (But 2 of the cylinders actually are low pressure feeding on the exhaust of the other 2, a compounding system)

*NOTE:This is just a quick calculation and someone fix a flaw if I made one without too much criticism.
 

James Bosma

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Last Subscription Date
02/03/2016
Here is a pic of a 500 HP steam engine will need a big car flywheel 18 feet in diameter and a 21 inch piston
 

LAKnox

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Age
62
Last Subscription Date
01/15/2016
CB I wouldn't call a locomotives engines small, they just look small compared to the actual monstrosity of the engine size but Just look at Pere Marquette 1225's engines, she has 2 of them each at 26 inches by 34 Inches, much bigger than most engines that we on the forums own. Or the Union Pacific Big Boy's with 4 Cylinders each 23 3/4 inches by 32 inches. The Big boy also produced 6000 draw bar horse power.

I did the calculations for a Big Boy,based on a 300 PSI(/2=150) normal working boiler pressure, and using the optimal speed of 35 mph (Found on Wikipedia) I figured out that it goes .58 miles every minute so that means 3062 feet and the wheels are 68 inches*3.14=214/12= 17.83 feet in circumference so that means 172 strokes per mile times 2 for double acting.

SO:
150*32*443*344=731481600/33000= 22000 IHP per cylinder at peak performance, correct me if I am wrong but that is one powerful engine, and has a combined IHP of 88,000 at 35MPH (But 2 of the cylinders actually are low pressure feeding on the exhaust of the other 2, a compounding system)

*NOTE:This is just a quick calculation and someone fix a flaw if I made one without too much criticism.
Gibby, double-check your specs on the Big Boy. Pretty sure it's a 4 cylinder simple. All cylinders are 23.75", according to Wiki. Makes the calcs simpler. :)

Lyle
 

GreasyIron

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Last Subscription Date
12/28/2019
Is it worth it to build a miniature steam engine from a kit to learn how steam engines work?
Beauty is in the eye of the beholder!

You certainly can learn how steam engines work without building a kit. But if you need an excuse to build a kit why not! :brows:

---------- Post added at 07:07 PM ---------- Previous post was at 06:58 PM ----------

Doesn't mean you can't make a fast lean car/motorcycle with steam if you want to...
-CB
I believe CB linked a modern experimental motorcycle using a Stanley engine. While not comparable to today's records, automobiles built Stanley and similar - Doble comes to mind - were used for some land speed records in their time.
 

gibbykart

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24
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08/22/2017
Ok that was my misunderstanding. I knew that the Big Boys were of the Mallet type, but they were not true Mallets. Mallets use a compounding system while the Big Boys, and quite a few other engine types actually used Simple systems. Sorry for the confusion. I should have put 23.75 but rather I put 23 3/4 as a accident, which I did use 23.75 on the calculation, sorry for any confusion. Either way though that is still one POWERFUL engine. -Mike
 

DianneB

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.... Either way though that is still one POWERFUL engine. -Mike
Check out the specs on the DM&IR Yellowstone locomotives - they actually developed more tractive effort that the Big Boy. But the DM&IR were in the iron ore business and didn't go for publicity.
 

LAKnox

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62
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01/15/2016
Check out the specs on the DM&IR Yellowstone locomotives - they actually developed more tractive effort that the Big Boy. But the DM&IR were in the iron ore business and didn't go for publicity.
If what Wiki says is believable, the Alleghenies were also more powerful than the Big Boys, though seem never to have been used to their full potential. They were dyno'd right at 7500 hp. The experimental Triplex had nearly 200,000 lbs tractive effort, but was so under-boilered that it wouldn't run more than about 10 mph.

Lyle
 

Malcolm Young

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As far as draw bar horsepower goes, I believe that the Chesapeake & Ohio class H-8 Allegheny 2-6-6-6 simple 4 cylinder articulated locomotives were the most powerful steam railway locomotives ever built, they were said to develop 7000 hp at the draw bar.
When the first one was built in 1940 the axle loads were falsified to get them below the maximum limit of the railroads that had to be used for delivery to the C & O, so in fact they were heavier and more powerful than the Union Pacific 'Big Boys'.
Articulated locomotives that were not compound were never (or should never have been) called Mallets. Anatole Mallet's patent was for a COMPOUND articulated design only.

Malc. :cool:
 

Gary K

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Last Subscription Date
07/15/2019
Check out the specs on the DM&IR Yellowstone locomotives - they actually developed more tractive effort that the Big Boy. But the DM&IR were in the iron ore business and didn't go for publicity.
Northern Pacific Railway No. 5002 2-8-8-4
In 1928 the Northern Pacific’s first 2-8-8-4, the 5000, was built by Alco, and after very successful trials 11 more of this type were ordered from Baldwin’s. For years these Yellowstones were the world’s largest locomotives and they still remain near the top in this class. They were designed to haul 4,000-ton trains the 216 miles between Mandan, North Dakota, and Glendive, Montana, up 1.1 per cent grades, which service they have performed most satisfactorily. Some improvements such as the addition of roller bearings have been made and their tractive power as last reported was 145,930 pounds.
Builder – Baldwin Locomotive Works.
Cylinders (4) – 26” x 32”.
Weight, total – 1,125,400 lbs.
Steam Pressure – 250 lb.
Fuel – 27 tons.
Water – 21,200 gal.
Dia. Drivers – 63”.
Tractive Effort (orig.) – engine – 140,000 lb., and booster – 13,400 lb.
R.R.Class – Z5.
Note:These Yellowstones were used by DM&IR in the Minnesota iron mines too.


Union Pacific Railroad No. 4000 4-8-8-4
The 4000 is one of a fleet of 25 such locomotives – the largest and heaviest steam motive power in the world. These “Big Boys” have a total length over couplers of 132 feet, 10 inches, and their basic design was developed by engineers of the Research and Mechanical Standards Department of the Union Pacific. Their objective was a locomotive capable of hauling maximum tonnage and maintaining schedules without helpers over the Wasatch Mountains on a ruling grade of 1.14 per cent between Ogden, Utah, and Green River, Wyoming, 176 miles. Tests were made with earlier articulateds and the result was this design, the mechanical details being worked out by Union Pacific engineers and those of the American Locomotive Co. These 4000 series locomotives can operate on any part of the system and can do up to 80 miles per hour, but produce maximum power continuously at 70 miles per hour. They were perhaps the Union Pacific’s most important factor in their handling of wartime freight, developing 6,000 drawbar horsepower at 45 miles per hour, and each doing the work of two other locomotives one of the toughest hauling jobs on any American railroad.
Builder – American Locomotive Co.
Cylinders (4) – 23 ¾” x 32”.
Weight, total – 1,208,750 lb.
Steam Pressure – 300 lb.
Fuel – 28 tons.
Water – 25,000 gal.
Dia. Drivers – 68”.
Tractive Effort – 135,375 lb.
R.R. Class – 4000

Courtesy of American Locomotives
 

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