There is a particular type of 4-wheel truck that shows up on tenders of 4-4-0s during the pioneering era. It can be recognized as having a large elliptical leaf spring above and parallel to the truck side frame on each side of the truck. The spring arches upward and supports the side sill of the tender frame. The ends of the spring are supported on the tops of the journal boxes. So the whole structural logic and load transfer scheme is unique. This design seems to have been quite common, but I have never seen any reference to them in any railroad publication. Does anybody know what this type of truck was called or have any other information on it? RTK

Jack White refers to this construction as the "Live Truck" (cf. Zerah Colburn). The weight is born at the top of the springs at the side bearings, while a bolster between the two spring buckles with a central guide pin kept it together. While it provided rudimentary equalization, it was a rather flimsy and dangeroud design, in that derailment was certain if anything in the truck "broke". White states "it proved to be unstable and prone to derail."Steve Zuiderveen

Steve, Thanks for your reply. In which of Jack White’s books does he cite that information? In his expanded edition of “American Locomotives,” he does briefly discuss live pattern trucks, but it seems that they are all lead trucks of locomotives. They have no side frame other than the spring itself on each side connecting the two journal boxes. They show up in several drawings of entire locomotives. I don’t find the particular discussion that you mention though. It would seem that those live trucks are an earlier practice than what I am referring to, but they are somewhat related in principle.I am referring specifically to tender trucks, and they do have side frames of the typical arch bar pattern that connect to the journal boxes. They have a solid crossbeam that rigidly ties the two side frames together. Between that cross beam and the bottom of the tender frame is a telescoping center bearing that carries no weight, since the weight is carried from the side sills directly to the tops of the journal boxes through the big leaf springs. All the center bearing does is maintain the radial position of the truck while allowing it to pivot. But the way the rest of the structure is put together does raise some questions in particular as to exactly how it is able to pivot.The type of truck I am referring to shows up on the tenders in photographs in the abovementioned book, on page 418, Erie 2-6-0 #254, and on page 515 C&NW 4-4-0 Crawford. This type of truck also shows up on the tender of the famous New York Central & Hudson River R.R. #999 that set the speed record. It also shows up on the tank trucks of the first common carrier, two-foot-gauge engines PUCK and ARIEL. It was quite common throughout the period from the Civil War to about 1900.RTK

I agree with you that Jack White mostly talks about the live truck in relation to lead trucks, but the principles as applied to a tender truck are the same; the bolster only serves to keep the side bearings apart, and do not provide any structure to the truck itself. In essence you now have a four point support system for the tender.Tenders were always notorious riding creatures, and the four-point system did not serve well. I seem to remember the locomotive that I learned on (Huckleberry #2) has a three point support system, where the rear two side bearings ride close, and the front basically rides only in its center plate. Think of a milk stool as being an inherently stable structure; this was also eventually learned for the locomotive itself, as the modern pony truck is arranged for three -point support between the first set(s) of drivers and the kingpin of the pony truck.Steve Zuiderveen

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Kelly,I am not sure, but I think the mode of operation for this kind of truck is for the spring buckle to remain stationary, and for the truck to slew in a parallelogram. What do you think?Steve

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Yes the pivoting seems problematic considering the four-point load contact of the springs onto the journal boxes. The close up photos of this type of truck show that the ends of the leaf springs are resting in iron tubs mounted on the tops of the journal boxes. The tubs have raised flanges on each side of the spring. Presumably these tubs allow the spring ends to slide while the raised side flanges of the tub keep the spring end properly positioned on top of the journal box. Aside from the pivot issue, the distance between spring ends would need to increase as the spring is flattened in loading. So at least one end of the spring must be free to slide on its support point. The slide tubs would allow this spread movement of the spring ends when loaded. Perhaps these tubs allow the sliding movement that would be needed to accommodate the pivot of the truck as well.However, the truck pivot movement between the tops of the journal boxes and the spring ends is circular, not straight. So even if the tubs allowed a sliding action, the fact that the slide is in a curved line would mean that the pivot of the truck would tend to twist the spring from end to end if the spring top is solidly connected to the tender side sill. Maybe the spring top is not solidly connected to the side sill, but is allowed to slide there too. If so, the entire spring would be simply captured in place, but not solidly connected to anything.Maybe because of a relatively short truck wheelbase and close truck-to-truck spacing, the pivot travel was so small that it could be accommodated in the looseness of the spring tubs without introducing a twist to the spring.Steve, you point out the difficult riding and suspension characteristics of tenders. It would appear that the point of this type of truck is to address that very issue by providing four-point suspension in the widest stance possible. I have never seen this type of truck on anything other than tenders. It is a very strange mechanical concept. All of the rest of the wide variety of trucks used on all types of equipment share the same basic components and loading scheme. These mystery trucks stand alone with a completely different loading logic. Something that different would be understandable if it was a one-time, kooky invention, but these were widely used. It seems like there ought to be a well known generic name for them.RTK

You guys have me curious. Can anybody post a link to an online picture of one of these trucks? I don't have the books mentioned.

Matt,Here are a couple examples:http://spec.lib.vt.edu/imagebase/norfolksouthern/full/ns1228.jpeghttp://spec.lib.vt.edu/imagebase/no ... .jpegThere is no conventional bolster, spring nests, or spring plank. What appears in the usual position of the bolster is a cross beam that is solidly connected to the truck side frames. The cross beam carries no weight. The cross beam does have a center bearing, but it is telescopic, so it transfers no weight.RTK

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Kelly,That is an excellent drawing of the truck in question. It has the tub castings on top of the journal boxes to house the ends of the springs. The tubs in your drawing are more like shoes that are enclosed all around the spring except where it enters them. It does appear that the spring ends are intended to slide in the shoes, since there is no indication of a means of attachment other than being captured within the shoe. It also appears that the top of the spring is mechanically attached to the tender side sill.I see what you mean regarding the 999. It does appear that the raised triangular equivalent of the shoe or tub features of the 999 may contain swing links that hang down from the top of the casting and pick up the ends of the springs. This would take out a lot of the friction that would be inherent with the slide tub approach. It would have the interesting effect of raising the tender slightly as the engine entered a curve. The lift would be so small though that it probably would be inconsequential.I notice that your drawing does not indicate any center bearing. It may exist but just not be shown in the drawing. Or maybe there is none. Fundamentally, it would not be needed, however, if included, it would contain the side-to-side forces that would tend to tip the springs over if there were no center bearing. The latest application of this type of truck that I have seen is on CStPM&O class I-1 4-6-0s built around 1902. The tender trucks of these engines too have the same triangular castings enclosing the spring ends like the 999. They also have heavy cast iron buttresses mounted on the top of the crossbeam and rising up high along the sides of the springs at their centers. These appear to be intended to keep the springs from side tipping. I would not be surprised if this type of truck was built with and without a center bearing. However this is hard to confirm by photographs because a center bearing would usually be hidden. The National Museum of Transport has a C&NW 4-4-0 with this type of truck, and they are each equipped with a telescoping center bearing. What is the application of the truck in the drawing you posted? Does the source describe it or designate a name?RTK

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I think a center pin (not a bearing) would be needed if the truck were to transmit braking force other than through the ends of the springs. These illustrations show brakes on the trucks.These are big springs compared with a freight car's. Could the justification for this design have been to find room for a leaf spring big enough to carry the weight of the water?

I have some thoughts to sum up the subject of this mystery truck. I had noticed this type of truck in several old photographs, and became curious about its design, so I did some casual research. So far, I have found no indication of what this truck was called, assuming, that due to its totally unique design, it had a name to differentiate it from other trucks. I would expect that such a name would reflect either the inventor, road of origin, manufacturer, or possibly the design characteristics. It may have had more than one name as a reflection of a variety manufacturers, and of the evolution of design detail that is apparent in the photographs. I asked John White about the name and origin of this type of truck. He was familiar with it, but did not know how it operated. He said he thought it might have been call the “Ohio Truck.” I have found no reference that discusses the origin, purpose, or pros and cons of this type of truck.It appears that the main purpose of this unique design is to provide the maximum possible stability against rocking. Most trucks are center bearing in their primary support with side bearings as secondary support. The side bearings carry no load unless the car body tips to either side. Therefore, to remain normally unloaded, the side bearing must allow some tipping before they come into play. This mystery truck uses side bearing as the primary and only suspension, and to give the most possible stability, the side bearing elements are placed as far apart as possible. The center bearing functions only to maintain the center point for the truck pivot. Whereas a typical center bearing has a thrust and a radial component, the center bearing of the mystery truck has only the radial component. It carries no weight. The greatest mystery of the mystery truck is how it is able to successfully pivot. Even if the spring tips could slide on their supports, there would be friction. While there is not a conventional center bearing that carries the load, there is an equivalent thrust-load carrying bearing in the form of the four spring tips which must slide in a circular pattern on the tops of the journal boxes when the truck pivots. Because the radius of that circle is several feet compared to the few inches of radius in a typical center bearing, the frictional resistance would be relatively high compared to a truck with a conventional center bearing. Adding to the friction would be the open exposure of the sliding elements leaving them liable to become caked with snow and ice. I wonder if these slide points were routinely oiled. If stability was a pro of this truck design, surely pivot friction was one of the cons. John White in his book, “A History of the American Locomotive,” talks about how tenders, compared to other rolling stock, are uniquely difficult to provide stable suspension for. Therefore, the fact that the mystery truck was apparently used only on tenders seems to reinforce the exaggerated quest for stability that its design suggests. I have never seen this type truck on any equipment other than tenders. With the exception of the CStPM&O ten-wheelers, I have never seen it on an engine of any wheel arrangement other than 4-4-0. Curiously (considering the issue of stability) I have never seen it on the tender of a 3-foot-gauge locomotive. Moreover, this truck does not seem to be the product of any one specific locomotive builder. Since it appears to have only been used on locomotive tenders, it may have been manufactured by several locomotive builders collectively following an established pattern. Just guessing by the photographs that I have seen, I would say that this mystery truck was used on perhaps 20% of all standard gauge 4-4-0 engine tenders between 1860 and 1900. Such numbers in use over such a long time suggests that the design must have been considered successful. RTK