A replica Quadplex (2-8-8-6-8-2)


It runs a bit fast though which is scary being live steam. It would be impossible to pick up off the floor or ground until it cools off. :)
Why? Axle loading would be no higher then other articulated locos - possibly lower. The more axles for the same weight the lower the axle loading the easier it is on the track.

Agree with bendorsey..the curves and bends cause the problems because the frames are too rigid and the locos tend to 'straighten' out the curves. Every time the big boys had been over a track the maintenance gangs had to go in and do repairs.
The biggest challenge a full-sized 2-8-8-8-8-2 would face would be keeping its steam up -- the Erie and Virginian triplex locos both had this shortcoming. But there was still another problem associated with the design concept -- as the locos used water, their tenders became lighter, which meant the adhesion of the rear set of driving wheels steadily decreased.
WVA-USA is right on.

The triplex wasn't a bad idea but they added two more steam consuming cylinders without adding any more steam producing capacity so it could have a tendency to run out of steam since the boiler might not always be able to "keep up".

Another factor was where they added the extra set of drivers and cylinders. By placing them under the tender as fuel and water was consumed weight on those drivers was reduced and as a consequence tractive effort was reduced so another potential problem might have been running out of TE down the line. Garratts have the same drawback in that all fuel and water is carried on the drivers. Now any dispatcher with an ounce of brains would (or should, lol) realize that and adjust the size of the consist so as not to exceed the TE of the engine when fuel and water levels were low.

Extra sets of drivers aren't the problem on curves. They swivel under the boiler. The problem is that unusually long boiler. Unless its hinged (which the ATSF tried with less then wonderful results) its going to wipe out anything close to the tracks on the outside of curves.

A normal articulated has the rear set of drivers attached to the boiler with the front set swiveling under the boiler. Overhang is all to the front. If a 2-8-8-8-2 is set up the same basic way (rear attached to the boiler and the middle and front sets swiveling under the boiler) overhang at the front would be excessive. On the other hand if the center set was attached to the boiler with the front and rear sets swiveling under it overhang at the front and rear would be no greater then a normal 2-8-8-2. Quite practical I'd think. Boiler would be longer for added steam production and so on.

Could a 2-8-8-8-8-2 be made? Perhaps if the front 2 pairs of drivers and the rear 2 sets were attached to plates which attached to the (very) long boiler. Overhang shouldn't be any more the a normal 2-8-8-2. It would be unusual in that it would not only occur at both ends of the boiler but in the middle too. This is the same concept as multi-bogey flatcars.

Be neat to see wouldn't it?

WVA-USA is right on.

The triplex wasn't a bad idea but they added two more steam consuming cylinders without adding any more steam producing capacity so it could have a tendency to run out of steam since the boiler might not always be able to "keep up". ...

Well actually, the triplex was a bad (design) idea, which is why the concept was abandoned in the U.S. But yes, the triplex design has remained a long-time favorite among model railroaders and rail buffs, despite its failure in the real world.

The laws of physics simply prevented anyone from building a firebox/boiler combination large enough to keep up enough steam, that would fit on the rails at least and still make through a standard size tunnel. The Erie tried to enlarge the size of their triplex's firebox, and keeping up steam was still a problem above 5 MPH. The Virginian also tried, building an a triplex with an even larger boiler and firebox. The VGN triplex was so big in fact it just barely fit inside the railroad's tunnels, despite the fact that the Virginian's tunnel clearances were among the largest of any U.S. rail line at that time. But the VGN's triplex still couldn't keep its steam up above 5 MPH.

Going back to the drawing board, the railroad and the locomotive designers then built the Virginian's 2-10-10-2 Mallets, which accomplished the task that the triplex locomotive had failed to do -- successfully moving heavy coal trains up the 13.4-mile winding, 2% grade between Elmore and Clark Gap, West Virginia, at 15 MPH.
I agree - I've read some (though not all) of your above info on the triplex. Particularly the thermodynamics of a larger firebox and its problems. Some ideas just look good on paper but don't fly worth a hoot. Like how about concrete wheels and rubber highways? Changing a flat would be hell, lol.

As for the VGN 2-10-10-2 tis my favorite steam loco. The stubby tender was so it could fit on existing turntables. Speed was low due to the massive amount of weight in reciprocating motion (side rods, connecting, rods, pistons, etc.). Plus the ruling criteria of the day was to move the maximum number of cars with a single loco - speed wasn't a factor (a criteria that didn't last too long). Sadly no one has made it for Trainz. Paulz Trainz USA does offer the ATSF 2-10-10-2 as payware.

Have you taken a peek at the huge boy? I asked someone who had it how it worked on curves and he sent me a screenshot showing it wasn't articulated at all. Basically its a 4-24-4 but looks like a 4-8-8-8-4. They may have changed it by now - I don't know. Impressive though.