08-21-2009, 07:14 PM
A 4% grade is very steep by prototype standards and is a grade that rarely is reached by most railroads without greatly restricting train length. For example: A locomotive exerting 80,000 lbs of drawbar pull can pull 17,778 tons on level tangent dry track. This same locomotive on a 0.80% grade will only be able to pull a train weighing 3902 tons or a little less than 1/4 of the train it could pull on the level. Looking at it from a different perspective, this locomotive would be able to pull approximately 137 130-ton cars on the level but only 30 130-ton cars up that 0.80% grade. You can find the formula to figure tonnage on grades in railroad engineering manuals, but it is probably a bit to complicated for model railroad use and wouldn't be accurate unless you were using steel wheels on steel rail due to the adhesion coeffients used to derive the formula. Other factors that would need to be taken into account to figure tonnage ratings on a grade would include wheel flange to railhead friction, curve resistance and moisture conditions just to name a few.
I think your locomotive is doing an excellent job of hauling those 5 cars up that 4% grade as it is, so rather than spending the money to put a traction tire on it, and possibly burning out the motor, do like the railroads do and add more locomotives. The other alternative would be to decrease the grade to a more prototypical grade and therefore be able to run longer trains with fewer locomotives. I have very few problems running on grades of up to 6%, but then my passenger trains are, at most, 6 cars long and all cars are powered (I model interurbans and streetcars so if it has a pole or pantograph it has a motor).
:ugeek:
I think your locomotive is doing an excellent job of hauling those 5 cars up that 4% grade as it is, so rather than spending the money to put a traction tire on it, and possibly burning out the motor, do like the railroads do and add more locomotives. The other alternative would be to decrease the grade to a more prototypical grade and therefore be able to run longer trains with fewer locomotives. I have very few problems running on grades of up to 6%, but then my passenger trains are, at most, 6 cars long and all cars are powered (I model interurbans and streetcars so if it has a pole or pantograph it has a motor).
:ugeek: