Climax

[martin.knoepfel]

I always wondered why there haven't been any Climax-engines for fast service.

after all, trucks ride much better than a rigid frame with three, four or five axles. several passenger train electric engines have motors connected to the axles by way of cardan-shafts, and they easily make 100 mph.

does anyone know the answer?

of course, Heisler ans Shay engines were not suited for fast trains, because the movements of their pistons had a vertical component.

[Overmod]

There have been discussions on this subject before, I think.

I might mention that the 'step-down' gearing problem does not *necessarily* have to be an issue on a locomotive intended for high speed. Many of the same construction details that characterize later locomotives (as discussed, for example, in the recent issue of Trains Magazine) could have been applied to a geared locomotive; an express locomotive would use appropriate gear ratios to keep piston speeds etc. in the proper range. "Legacy" geared engines were usually used for logging and other indifferent-track services where running-gear flexibility and low-speed power were critical -- one shouldn't expect a locomotive built for such services to be capable of high speed as built!

In a sense, the V-engine locomotives of the '30s and '40s are like the Climax without trucks; my impression is that the choice of V rather than 'horizontally opposed' (as in the Paget locomotive) was done for more than 'packaging' reasons. IIRC one of the Henschel locomotives was said to have run at more than 110mph equivalent without particular problems.

What I believe Martin is suggesting is a steam locomotive with a more-or-less conventional set of cylinders, driving onto quartered cranks on a transverse jackshaft which is then connected via bevel gears to a Cardan-shaft drive and trucks. Note that the imbalance and surge forces in this design would resemble those in a conventional steam locomotive at low speeds, and the vertical component of rod momentum and thrust that led to complaints of 'bouncing drivers' in some of the large steam locomotives at high speed would not be particularly solved by this design -- you're NOT getting rid of a 'vertical component' just because the stroke of the piston is longitudinal. Furthermore, the room required by the gearcase and drive to the shafts would preclude the use of multiple cylinders.

I am not certain you'd gain too much in operational effectiveness by use of this design over what can be accomplished with a Heilmann-pattern steam-electric. For example, many of the better Cardan-shaft locomotives route the driving shaft vertically, through a centerless bolster, which eliminates many of the difficulties involved with long driveshafts going to pivoted trucks. To accompli***his on a Climax-style locomotive would almost certainly involve a relatively high center of gravity, and a shaft tunnel very close to the boiler and hence relatively difficult to maintain or shop. It's easier to design balanced arrangements of machinery when you don't need to figure things like maximum shaft angles into the critical envelope of the design...

In general, American practice seems to have been reluctant to adopt right-angle gearboxes in locomotive drives. One of the principal reasons given for the relative non-acceptance of diesel-hydraulics in American practice was the required maintenance schedule for the gearboxes (a complete oil change every 30 days when some of the Krauss-Maffeis were under warranty, if I remember right). Much easier to cope with this kind of thing when spur gears in a sealed and aligned motor case, with some grease, gets the job done!

My own feeling is that a "better" approach for a high-speed geared engine along these lines, if you want one, would consist of a horizontally-opposed motor (rather than a V type) with comparatively short stroke, driving central Cardan shafts to properly-suspended trucks (more or less a la Heisler, but perhaps with Ferguson couplings between the axles to eliminate the worst of the problems with wheels that become of slightly different diameters as they wear). A V engine with inherent dynamic balance could also be used, but this requires a fairly large minimum number of cylinders; a balance shaft could be used but this adds complexity and may not address problems of augment.