GTrax and other steam

[CSX2057]

Right,

Here's what I found out on wiki

http://en.wikipedia.org/wiki/Locomotive_wheelslip

What you said is true, there's 2 reasons. To much power and to much weight will cause the Wheel Slip effect. Thats why in Donner Pass they use pushers. Least I'm learning more now.

I'm doing a test theory on Steams how well each can pull by their own power. So far UP Big Boy with 280 psi pulls 50 cars. Challenger with 270 psi pulls 30 cars. NKP Berkshire 250 psi pulls just about same as challenger but! The train stopped passed Verdi. It couldn't pull all that weight and cause alot of friction making it to slip on the rail. Solution Reduce cars or add second Steam for pushing. It can pull! So I'm gonna reduce the weight and see for myself. Not all steams can pull alot of weight.

I use Verdi as half pass to Truckee on 1.1% Grade. Full Pass from Truckee to Norden where there's a 2.4% grade there. Any Steams makes it there that I know how much it can pull without wheel slips.

[CSX2057]

One question I do wanna ask. How can you tell how many cars or pounds can a Steam Engine pull? By Tractive Effort? or ???

[mrennie]

One question I do wanna ask. How can you tell how many cars or pounds can a Steam Engine pull? By Tractive Effort? or ???

Tractive effort isn't constant. The starting tractive effort, i.e. the tractive effort at close to 0mph, is highest, and is really what counts for getting a train moving. Some steam engines had "booster" steam engines in the trailing truck that gave some extra starting tractive effort. They'd switch off at about 15 to 20mph. Once the train is moving at 15 to 20mph, horsepower takes over. HP isn't constant either, but varies with speed and, just like in most cars, the curve of HP versus speed resembled a hump. In my Connie, the horsepower reaches its maximum at about 20mph, and then falls away.

Here's a book that is a "must read" if you really want to understand about steam engines:

http://users.fini.net/~bersano/english-anglais/LOCOMOTIVE%20BOILERS%20&%20ENGINES_Llewellyn_%20V_%20Ludy-1920.pdf

It's packed full of formulae and equations for things like steam and coal consumption, computing tractive effort and so on. On page 128 you can find the equation for tractive effort, which is very instructive (it shows that locos with smaller driving wheels have higher t.e.). Pages 130 to 131 explain the methods for rating locomotives in terms of the tonnage of train they can haul.

"The usual method of rating locomotives at present is that of tonnage. That is to say, a locomotive is rated to handle a train, weighing a certain number of tons, over a division. This is preferred to a given number of loaded or empty cars because of the indefinite variation in the weights of the loads and the cars themselves.

In the determination of a-locomotive rating there are several factors to be considered, namely, the power of the locomotive, adhesion to the rail, resistance of the train including the normal resistance on a level, and that due to grades and curves, value of momentum, effect of empty cars, and the effect of the weather and seasons. The power of a locomotive and its adhesion to the rails has already been considered. From the formula given, the tractive power can be calculated very closely from data already at hand.

There are three methods in use for obtaining the proper tonnage rating. First, a practical method which consists in trying out each class of engine on each critical or controlling part of the division and continuing the trials until the limit is reached. Second, a more rapid and satisfactory method is to determine the theoretical rating. Third, the most satisfactory method is, first, to determine the theoretical rating and then to check the results by actual trials."

That last method should interest you

If you can understand the equation on page 131, it's possible to set up a test run, like I did coming out of Altoona, to check that the train does stall at the distance predicted by the equation. The only slight snag is that you have to check that the weight of the train is correct, which means checking the blueprints of the cars in the consist.

[mrennie]

Something else is that in real-life it was hard to compute the horsepower (and you have to differentiate between the different kinds of horsepower ... usually the one that was of most interest was the horsepower available at the drawbar, to pull the consist, after using some horsepower to move the loco itself and its tender). They'd usually measure it on a test run using a dynamometer car, one that was packed full of measuring instruments. A few shops, such as at Altoona, had static equipment for measuring it on a rolling bed.

[CSX2057]

Thanks Mrennie. I'm not very good on Math Formula. But these are great tips and i'll keep it for future reference, for now I'll stick to the car pulling.


Edit:
One other thing I tried everything else the only ones that are working is the Dampers and Blowers. Thats all I got. It helps a little.