Single valve gear set on a duplex drive locomotive

Trains Magazine Steam & Preservation
21

I call it the “OR class” by reflex, as the first place I heard about it (and only place for many, many years) was a somewhat cryptic reference in the Ransome-
Wallis Encyclopedia of World Railway Locomotives.

I am delighted to see that the inimitable Mr. Self has gotten around to describing the TP1-1. That engine is kind of the ‘three great tastes in one candy bar’ of the locomotive world: rocking levers, jackshafts, and Still-style steam/IC operation all in one package. (I am tempted to consider this a result of smekalka tempered by killing all the competent engineers in the wrecker trials… but that might be uncharitable. And I do love me a mechanical complexity (see the avatar).

As a note: I considered the OR23 to have only two cylinders (not four as he indicates), very long and with multiple ports, each containing the two DA pistons. This was vaguely reminiscent of the arrangement in the OPOC engine so beloved of Bill Gates near the turn of this century.

I think he is being a bit too hard on the AA20. Its intended use was in Dona-Cristina-like continuous service on, as I recall, coal trains to industrial facilities in the Donetsk region, on a long virtually straight line built to light and not very certain standards. It would not have been expected to pass through any switches or crossovers, except perhaps those in a wye (with very long frogs and radius of curvature!) to turn it. My suspicion is that it was treated much as railway workers were in that era, and expected to handle all sorts of traffic, with everyone being shot when it did not. The thing I’d like to know is why it was preserved all the way into the decade of the '60s…

22

Firstly, I should correct my last posting. The simplified valve gear details are from Le Fleming and Price’s book, not Westwood’s.

There was another locomotive that retained the “OR” classification, the OR21. This was a larger boilered version of the OR 18 / LV class. In fact the LV, OR21 and OR23 were generally similar in overall layout. The high pitched boiler allowed for the opposed piston mechanism to be fitted above the driving wheels on the OR23 without major change in the layout. Clearly the OR21 was midway between the other two in weight. Some additional weight must be expected from the opposed piston mechanism, but maybe not ten tonnes.

The OR21 was intended as a replacement for the FD class, but only three were built as construction changed over to diesel electric locomotives.

The TP1 was summed up by Louis Marre’s comment of “What could possibly go wrong?” But it is good that Self has finally added it to his otherwise excellent summary.

I agree that his evaluation of the AA20 is excessively negative. I suspect that it did have track spreading problems but not so great that a place could not be found for it. My work has exposed me to bureacracy in many forms, and I expect that AA20-1 remained for so long because nobody actually gave instructions for it to be disposed of.

Peter