Re: SVRy #250 and #251 side tanks

Speculation on my part.

SVRY had to make a substantial effort and expense for these engines. Besides buying them and transporting them, they had to:

Steal the tenders from the 19 and 20. Was it because these were the largest SVRY tenders or the least liked/poorest condition engines?

Add oil bunkers and lines to the tenders.

Remove the rear coal bunker and rebuild the rear of the 50/51 to include the drawbar and buffer for a tender.

Convert 50/51 to oil burning. Did they use salvaged or new parts?

With all this work there may have been some concern that either the tenders by themselves were too small to make it between water tanks with an adequate reserve - or to see if they could remove the water tanks without causing too many issues.

Remember that carrying the water in the side tanks offered a couple important advantages to Uintah vs. building them as tender engines. The extra weight of the water on the drivers increased the factor of adhesion. I've just found claims by GE that while steam locos were designed for 25% adhesion, in reality they were closer to 18-20%. It is known that on slippery/poor rail adhesion can be as low as 20% even for a diesel-electric. So did SVRY test the 250on several trips while varying the amount of water carried in the side tanks to be sure that they could remove them without making the engines too slippery. In the factory, they had scales capable of weighing each axle, I doubt SVRY had this capability. Also remember that they had already remove the coal bunker which would have removed some weight as well as changing the weight distribution. If I recall, later photos show the 250/251 having scrap rail as part of the running board being carried by the former water tank brackets. So at least SVRY was smart enough to add so weight back to compensate for carrying some water plus the weight of the tank itself.

Adding more weight (whether diesel or steam) does increase adhesion for starting and at low speeds, but where grades are concerned that weight still has to be drug up the hill, reducing the amount handled behind the drawbar. I wonder if SVRY ever considered leaving these as tank engines, or if they couldn't carry enough water/oil in their tank configuration? These would have had a higher tonnage rating as tank engines vs. tender engines, the weight of fuel and woter wouldn't change unless you were carrying more, plus the weight and extra friction of the tender itself.

Dan