Author Topic: #7 Status and Tractive Effort  (Read 1723 times)

Matthew Gustafson

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#7 Status and Tractive Effort
« on: January 22, 2013, 01:08:53 AM »
What work has yet to be done on the #7 this year to achieve that goal of it getting running again? Can anyone post a list please in numerical order please. Also I know the current museum site at Portland is mostly level and no grades but if there were some grades could #4 (or #3) can pull all those coach's with ease or will it struggle? What is their pulling power maximum?
« Last Edit: January 22, 2013, 01:11:07 AM by Matthew Gustafson »
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Bill Piche

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#7 Status and Tractive Effort
« Reply #1 on: January 22, 2013, 06:04:50 AM »
What work has yet to be done on the #7 this year to achieve that goal of it getting running again? Can anyone post a list please in numerical order please. Also I know the current museum site at Portland is mostly level and no grades but if there were some grades could #4 (or #3) can pull all those coach's with ease or will it struggle? What is their pulling power maximum?

We need to update the punch list, but it's still long. We'll probably have something out once we have our winter steam crew meeting in February.

The museum area isn't entirely level, actually. The approach (heading west) to Cutter Street crossing is the ruling grade on the line, and it's just over 1% for just under a quarter of a mile. Going back to the museum it's a little bit under 1%. There's about a 1/2% - 3/4% grade at fish point, as well. #4 didn't have all that much of a problem when I was running her, but that doesn't mean that you can't have problems.

It's all about train handling and situations, and we have taken steps in recent years to eliminate variables. Example: A few years ago, when we first started running 7 cars on the train for winter, sometimes the engineer would slip trying to get over the hump at Cutter. That was caused primarily by having to slow down to let the brakeman off to flag the crossing. (And yes, people still use the road even in the winter. Why? I have no clue since the launch is theoretically closed and it's a little cold for the beach.) The solution for this was to have a flagman on the ground for when the train came through, which allows engineers the option to 'run up' the approach to the crossing. That's just an example, there's plenty other things that make Polar challenging for the engineers (weather is one, lack of a rear sander on 4 is another, and so on).

As for which engine would have a tougher time: #3 would have a tougher time than #4 (train loads being equal) because of the larger drive wheels and the lighter body in full. The story (as I have heard it) was that, on the old Monson, the Hinkley locomotives could pull 1 car load of slate at a time, #3 was designed for pulling 2 car loads of slate, and #4's design was tweaked so that it would pull 3 car loads at a time. Exact weights and tractive effort? That I don't know the equations for.

Even at reduced pressure nowadays, #4 is still strong as a ox if you know how to push her buttons the right way. She has more than made up for her past as a "problem child" locomotive down at Edaville with how well she runs nowadays. I think, with the right crew, she could probably still give #10 a run for her money going up the ladder.  ;)(P.S.- not looking to start a tractive effort fight, just having a little fun.)
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Steve Smith

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#7 Status and Tractive Effort
« Reply #2 on: January 22, 2013, 04:38:54 PM »
Bill, the Locomotive Cyclopedia for 1947 gives the following formula for tractive force for a two-cylinder simple locomotive (i.e., not compound) adopted by the Association of American Railroads, Mechanical Division in the 1924 Proceedings:

Tractive Force = [(K)(P)(C squared)(S)] รท (D)

Where:  K = Constant from table below
            P = Boiler pressure, psi
            C = Cylinder diameter, inches
            S = Piston stroke, inches
            D = Driver diameter, inches

Values for K

Cutoff,%   versus  K

90         .85
80         .80
70         .74
60         .68
50         .60
« Last Edit: January 22, 2013, 04:43:18 PM by Steve Smith »