What was the rationale for the cylindrical Vanderbilt tender? Was it capacity? Center of mass? "Slosh" factor?

HI

According to my 1930 locomotive cyclopedia , first they were cheaper to built , because less rivets were needed . Because of less rivets it did decrease the chance of leakage of water
Also inside the tank were splash or slosh plates ,these plates are better known as Baffle plates, to minimize the water from surging , depending on the size of the tank , as many as six plates could be used .

As for tank capacity as much as 21,500 gals of water , and 24 tons of coal , was used on a Great Northern Vanderbilt tank , that rode on six wheel Commonwealth trucks , Pat

Cylindrical tanks with dished ends are self-bracing. Rectangular tanks are not; they require internal cross-braces and reinforcing to prevent bulging. Rectangular tanks are generally built with an complex internal square-honeycomb of antislosh baffles (with holes big enough to crawl thru) riveted to the sides and bottom of the tank. They're a perfect nightmare to chip out with a needle gun or sandblaster. You're constantly on your knees in a dark confined space, surrounded by a dust storm of rust and crud. Cylindrical Vanderbilt tanks require a much simpler system of cross-wise and fore-and-aft anti-slosh baffles. This gives the Vanderbilt tank some advantages:
- less steel needed, so easier & cheaper to construct, and less deadweight... an important consideration, since roughly half the weight of a loaded tender is steel.
- easier to clean out
- easier to inspect and keep relatively free of rust
- somewhat better visibility towards the rear when switching.

Tender tanks tend to rust out on the side sheets near the bottom. S.P. Vanderbilt tender tanks (and probably most other Vanderbilt tanks) have an extra-thick lengthwise bottom plate in this zone. They survived daily service in the steam era, plus years of neglect in outdoor display, in surprisingly good condition. The two S.P. 4-6-2 Vanderbilt 12,000-gallon tenders I'm familiar with (S.P. 2467 & 2472) had a lot of corrosion on the anti-slosh baffles and their angle irons. They seem to have served as the sacrificial anodes or cathodes, whereas the tank body is in much better shape. Fortunately the Vanderbilt anti-slosh baffles & their angle irons are relatively easy to reinforce or replace.

Disadvantage of Vanderbilt tanks is that they're longer than high boxy rectangular tanks of the same capacity. Longer turntables & roundhouses were required.

Many older rectangular tanks had serious rust-through problems while in daily service - look for patches riveted on the outside. After another 50 years of outdoor display and neglect, it's often cheaper to build a new tank than try to patch the old one.

The one-piece cast-steel "water-bottom" rectangular tank design solved m,many of these problems. A huge cast-steel "waffle" functioned as the underframe, tank bottom, lower part of the sides, and bottom baffle supports. The worst rust-thru areas were compensated by thick metal where it was needed. Structurally this was much more weight-efficient than a tank bolted to a separate underframe. Later-model S.P. cab-forwards and 4-8-4s used this design.

During WW2, German State Railways (Deutsche Reichsbahn) built welded semi-Vanderbilt (cylindrical bottom, flat top) tender tanks that also functioned as the underframe. It saved steel and deadweight. Modern tank cars use this design approach.

- Doug Debs

On a mathematical analysis, a cylinder tender will hold 79% of the volume of a square tender of the same clearance dimension. So the maintenance reduction is penalized by lower water capacity.

Iron and machinery world (1901), Volume 90 (Google book)

Quote:
The Vanderbilt Tender.

Cornelius Vanderbilt, who has set a pace that railroad inventors have found hard to follow, has just obtained a patent for an improved type of locomotive tender. The mechanical genius of the family of millionaires has thus added another to an already long list of successes in the field of discovery and invention.

Friendly experts at the Grand Central Station say Mr. Vanderbilt has now on record from ten to twelve inventions for locomotives alone that are of great importance. They reverse methods which hitherto have distinguished locomotive architecture, and the Vanderbilt type of locomotive is now practically a distinct one.

Mr. Vanderbilt's latest invention to receive the sanction of the government through the Patent Office is a tender consisting of a cylindrical water tank and. superposed on the end next the locomotive, a coal box of new design. The old fashioned square box construction, heavy, clumsy and unscientific, is done away with. The tender runs on two ordinary coach trucks of four wheels each. On the platform rests a cylinder resembling the tank on an oil car. This carries the water, about six thousand or seven thousand gallons.

Over the end of the tank, next the locomotive, the coal box is placed. An inclined partition divides the box from the tank. The partition terminates in a horizontal plate, which forms a part of the bottom of the box. The capacity is seven or eight tons.

There is an aperture in the front plate leading into the fuel box. The fireman, standing in front of his furnace, is in easy reach of the opening, and the sloping sides of the receptacle carry the coal to his shovel as the supply in the tender is gradually used.

Some of the advantages claimed for the Vanderbilt tender are greater carrying capacity for both fuel and water; the cost of construction and maintenance is reduced, and the facility of construction increased. The utilization of commercial forms of iron is made a leading feature. Economy in carrying and handling.coal and water, lightness and at the same time increased strength of the parts of the tender, are all said to be attained, by the Vanderbilt model. In the cylindrical water tank the wash of the water and consequent constant strain in the old style of tender is reduced to a minimum in the new type.

A locomotive equipped with all of the Vanderbilt improved appliances has recently been turned out by the Baldwin works in Philadelphia, with one of the new tenders attached. A model of the Vanderbilt cylinder tank tender was on exhibition in the railroad division at the Pan-American Expo

[Edit: Converted book image to text for easier reading]

Wow, straight from the millionaires mouth! Thanks for post all these replies!

Would Vanderbilt himself have been actively involved in the design, or did someone come up and say I have a good idea, and convince Mr. Vanderbilt to finance it and he put his name and patent on it?