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Comparing SD70Ace to Stephenson's Locomotion #1

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[quote user="JayPotter"][quote user="fredswain"]  A steam engine with it's larger wheels has less starting TE per the same amount of drawbar horsepower. It sounds confusing but is easy to explain with math if you want me to get that complex with it. [/quote] I would be interested in the mathematical explanation if it can be applied to steam-versus-steam or diesel-versus-diesel.   Thank you.  [/quote]  Hello,I fear, quoting from wikipedia,  same formula also used at steamlocomotive.com ; so for a 2 cylinder loco : <dl><dd><img src="http://upload.wikimedia.org/math/f/6/5/f6572fb694a0dfed305d7c4d8b596053.png" mce_src="http://upload.wikimedia.org/math/f/6/5/f6572fb694a0dfed305d7c4d8b596053.png" class="tex" alt="t = \frac {cPd^2s} {D}"></dd></dl> where <ul><li>t is tractive effort</li><li>c is a constant representing losses in pressure and friction; normally 0.85 is used<a href="http://en.wikipedia.org/wiki/Tractive_force#cite_note-16" mce_href="http://en.wikipedia.org/wiki/Tractive_force#cite_note-16">[note 9]</a></li><li>P is the <a href="http://en.wikipedia.org/wiki/Boiler" mce_href="http://en.wikipedia.org/wiki/Boiler" title="Boiler">boiler</a> pressure<a href="http://en.wikipedia.org/wiki/Tractive_force#cite_note-17" mce_href="http://en.wikipedia.org/wiki/Tractive_force#cite_note-17">[note 10]</a></li><li>d is the <a href="http://en.wikipedia.org/wiki/Piston" mce_href="http://en.wikipedia.org/wiki/Piston" title="Piston">piston</a> diameter (<a href="http://en.wikipedia.org/wiki/Bore_%28engine%29" mce_href="http://en.wikipedia.org/wiki/Bore_%28engine%29" title="Bore (engine)">bore</a>)</li><li>s is the piston <a href="http://en.wikipedia.org/wiki/Stroke_%28engines%29" mce_href="http://en.wikipedia.org/wiki/Stroke_%28engines%29" title="Stroke (engines)" class="mw-redirect">stroke</a></li><li>D is the <a href="http://en.wikipedia.org/wiki/Driving_wheel" mce_href="http://en.wikipedia.org/wiki/Driving_wheel" title="Driving wheel">driving wheel</a> diameter</li></ul>( http://en.wikipedia.org/wiki/Tractive_force ) For playing around with that conveniently, see also please http://www.steamlocomotive.com/misc/TractiveEffort.shtml , works with actual JAVA-version. Byelars   -edit-BTW.: for a 4 cylinder artic. simple; multiply the result with x 2 . The formula is just for starting te.
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