Bachmann 4-8-4 sp4 post war steam loco

[aswamina]

I am thinking of purchasing a bachmann 4-8-4 sp4 post war steam loco.  I think the part# is 50204.  Three questions :

a) Is this a discontinued model because I cannot find it on the "Product Information" section in the Bachmann website ?
b) What is the minimum radius for the track to support regular operation (no derailment) for this loco ?
c) How many regular Bachmann box cars can this loco pull up a 3% gradient slope ?

Appreciate your feedback on the above questions.

Regards,
AS

[Doneldon]

asw-

Bachmann only sells the SP GS4 with DCC. They have two numbers: 50201 and 50202. All of Bachmann's locos with DCC are dual operating so you can run the loco on a DC system without worries. The decoder will automatically detect which system the layout uses.

What radius a given locomotive will clear is only partly a function of design because, as everyone on this board will tell you, there are always some locos of a given design which will clear tighter curves than they were designed for and others which will require broader curves. So ... you really have to check out the explicit loco. That being said, the Bachmann Northern should do okay on 22" curves but it won't look very good doing so. It might have trouble pulling long passenger cars through such curves and turnouts but should do better with freight cars which are shorter.

The same principle applies to pulling strength but to a lesser degree. Your Northern should pull a reasonably long string of freight cars on the straight and level but its pulling capacity will be a bit less on curves, due to friction between wheel flanges and the sides of the railheads, and much, much less on grades. Three percent grades are extremely steep. Twelve inches to the foot railroads would use such a grade in only the most extreme circumstances and they would begin planning a new track alignment before the three percent grade was even completed. You have to think of a locomotive pulling cars up a hill as more like a locomotive lifting cars up and over an obstacle. Thus, a locomotive on a three percent grade may only be able to pull 30% as many cars as it could pull on the level, and maybe even not that many. Add a curve and the number goes down some more.

The thrust of all of this is that you should explore ways to ease your grade. You can do that by using more linear distance for the same elevation change. Or, if you have a trestle going up and over a second track, lower the upgrade at the same time that you add a downgrade to the lower track. In that way, you stretch out the total vertical movement over both grades, making each less steep.

You can increase your loco's pulling power by adding weight and by using friction tires on some of your drivers. Be aware, however, that friction tires are not prototypical and they interfere with electrical pick up. It would be better to lessen your grades than to load up weight in your loco and add friction tires.

A final alternative for getting trains up steep hills is using a helper. This can be tricky in DC because both locos will receive the same voltage but they won't necessarily move at the same speed with the same power. It's comparatively easy to consist helpers with DCC because you can speed match the locos to compensate for motor, gearing, bearing, wheel diameter and wheel material differences.

I hope this is more helpful than discouraging. Do let us hear about your progress and how you've solved your problems.
                                                                                                                                                                                    -- D

[aswamina]

Thank you . This was very helpful.  With the space constraints I have, I can only redo the benchwork to accomodate 2% grades and 24 inch radius.  I am hoping this will help smooth the operations.

Regards,
AS

[Doneldon]

I can only redo the benchwork to accomodate 2% grades and 24 inch radius.

AS-

I predict that you'll be 100% happier with 24" radius and 2% grades than you would have been with 18" radius and 3%.

                                                                                                                                                                       -- D