Question for steam fans......

[Jacktal]

Which was the better puller?The 4-8-8-4 Big Boy or the 2-8-8-2 Mallet?That's a thought that came to my mind while comparing the two engines.They both had sixteen powered wheels and since I believe locos were limited by a weight per wheel rule,I think they must have been pretty close to eachother,as far as traction is concerned.The Big Boy was indeed heavier,thus the extra sets of wheels to comply to the rule,but was it really that much stronger?Just curious.

[ndbprr]

That isn't an easy question to answer. A number of factors influence the answer. The first one is which 2-8-8-2 do you want to compare to the Big Boy? It is a fairly complicated formula that considers weight on drivers, driver diameter, Tractive effort, steaming at maximum exertion of force, piston bore and length of stroke, curve radius and several other factors. The Big Boy was the largest engine but that doesn't necessarily mean it was the most powerful or capable of doing the most useful work.

[Anonymous]

We had a friendly fight on the forums about this some time ago.

The N and W Class Y6b Mallet has awesome tractive effort and will keep any train moving (5-20 mph) no matter where the track goes.. up hill down hill side hill and upside down. The power lies in tractive effort and small driving wheels which gives "Strength" to the engine when the train is heavy and the grades are steep.

The Big Boy is designed to keep a large train moving fast across wide open and hostile western reaches where grades are kind of small but are very long. These kinds of grades occasionally gets very steep and awesome. The Big Boy is capable of keeping enough steam and horsepower at the wheels to maintain high speeds with long trains.

Viewed another way you have western engines Horsepower versus the eastern engines Torque.

As ndbrr stated in order to have a steam engine to do a job properly to what you need it to do is a combination of different factors.. some more suited to the east and others better for the west.

For sake of "What if" let us put the Big Boy on the Eastern Mountains and the Y6b Mallet out west. I think this what would happen:

The Big Boy will not have room to reach it's best power and constantly waste fuel and water slipping on some of the brutal eastern grades and probably stall a time or two. It will probably get the train delivered but will be late, worn out and dead on the law.

The Mallet will crawl at 40 Mph and run out of fuel and water long before it arrives at the destination. The logistical support required to feed and water these engines probably will remove any benefit with this engine out west.

Now keep in mind that various engines such as the Challenger, 2-6-6-6 and 2-8-8-4's as well as the Cab-Forwards all are pretty similar to this problem but are designed for thier specific areas of operations.

And finally the classic problem remains "If the train does not move, add more locomotives"

And so you had 3 Mallets of the Y6b class up front and perhaps 2 on the rear of a really heavy train. Or two Bigboys up front. I am too young to ever know the power and glory of these monsters in thier heydey.

[M636C]

During World War II, Santa Fe bought some ex N&W 2-8-8-2 locomotives of the Y-3 class which they used as pusher engines on grades. They were not really useful. and there was a proposal to rebuild some older 4-8-4s with the Y-3 boiler.

If you compare a Bachmann 3765 class 4-8-4 with a Rivarossi Y6b, you can see how the boilers are about the same size.

The end of the war and the availability of diesel road locomotives meant this was never actually done. But it would make an interesting Kitbash.

It does show that in boiler power, the Y6b was nearer a large 4-8-4 than a 4-8-8-4, although comparing models of FEF, Challenger and Big Boy will indicate the relatively small boiler size increase for the bigger locomotives, particularly if you subtract the smokebox volume as non productive.

Peter

[Anonymous]

The N&W Y6b was used for heavy coal drags on steep grades in the eastern mountains. The Big Boy was used to pull long, heavy freights over moutains at high speed. Let's put it this way:

The N&W took a locomotive 30% lighter than the Big Boy, and somewhat smaller as well. At 25 mph, both locomotives had 5300 HP, so the N&W could do more with less. Of course, just like the Big Boy vs. Allegheny debate, the two locomotives never did the same tasks, so this will be another unsolved mystery in the wonderful world of railroading.

So in the end, they really aren't better than eachother because they never did the same tasks.