My narrow knowledge tells me that I’ve only seen (on models) leaf spring trucks on steam loco tenders and cabooses. I’m assuming a leaf spring gives a smoother ride, but there must be quite a difference in the spring strength between a tender and a caboose, given the difference in weight. So in the day of arch bar trucks, for instance, why wouldn’t the shipper using a reefer want a similar smooth ride? But I’m guessing that a leaf sprung arch bar truck never saw the underside of a reefer. Thoughts?
Thanx,
Ross PINYAN - Irvine, Calif.
There is little mystery here. The leaf springs work nicely in cars where the weight changes little if at all in service, for example in cabooses or the bolster springing in a ‘Blomberg’ truck. You may want to look forward at the experimentation with true high-speed three-piece trucks starting in the late '40s, some of which involved leaf springs. Nests of coils with ‘snubbing’ action is a far more flexible approach over a range of car types to be accommodated by one set of parts, and addition of elastomer blocks (think of them a bit like ‘rubber car spring 2.0’) adds suitable damping where required (you seldom see the need for things like hydraulic dampers on three-piece trucks although earlier designs such as Chrysler’s explicitly had them).
I would not assume that leaf springs were not used in reefer trucks. There was a genre of trucks known as “swing motion” trucks. This type of truck was intended for a smoother ride and was widely used on cattle cars and also on cabooses. Swing motion trucks had the spring plank carried on swinging hangers suspended from the timbers making the solid bolster connection between the upper regions of the truck frames. So the spring plank could oscillate side to side while hanging from its swinging hangers. Typically, these trucks were equipped with sets of eliptical leaf spring sets mounted with their length parallel with the swinging spring plank. The leaf spring sets were naturally stable in accommodating the oscillating spring plank. This truck is essentially the same as the Blomberg truck used on diesel locomotives.
The action of the leaf springs caused the leafs to slide in relation to each other as the spring flexed. So in effect, leaf springs have moving parts. The leafs sliding against each other as the spring flexes causes friction, which dampens the spring rebounding action. So they act as shock absorbers used on motor vehicles in addition to just flexing to absorb shock loading from rough track.
Whereas,
Note that ‘swing motion’ and ‘swing hanger’ trucks are two potentially different things, and they control the lateral component of ride more than vertical secondary suspension.
A major issue with any truck involving a separate bolster is that if the springs break or dislocate there is an immediate and catastrophic effect usually leading to derailment.
You should probably link a couple of images to show these, as I think you have a particular interest in many of these largely-forgotten late-1800s evolved truck designs. Some of the things that were tried to improve ‘ride’ as speed and load increased are ingenious but strange to modern eyes.
For the record, the technical term for this is *full-*elliptic. These were extensively used on carriages where extreme light weight and substantial suspension excursion were expected. We are much more familiar with semi-elliptics using shackles to accommodate length changes where needed. I can go into the reasons why full elliptical are and aren’t used if there in any interest.
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The action of the leaf springs caused the individual leaves to slide in relation to each other as the spring flexed. So in effect, leaf springs have moving parts. The leaves sliding against each other as the spring flexes causes friction, which dampens the spring rebounding action. So they act as shock absorbers used on motor vehicles in addition to just flexin
Overmod,
Wow, you provided a lot of info… much appreciated. Now I’ll take a chance and put my surplus (leaf spring) arch bar caboose trucks on an HO wooden reefer kit that’s nearing completion; and see if any rivit counters notice.
If leaf springs work best on equipment with a fairly constant weight why would they be used on steam locomotive tenders? The empty and loaded weight of a tender would vary significantly.
Mark Vinski
Yep 30 tons of coal and 30K gallons of water weigh a gram to two.
Because ride quality does not matter to the extent it would with paying passengers or freight.
[quote user=“Overmod”]
Euclid
I would not assume that leaf springs were not used in reefer trucks. There was a genre of trucks known as “swing motion” trucks…
Note that ‘swing motion’ and ‘swing hanger’ trucks are two potentially different things, and they control the lateral component of ride more than vertical secondary suspension.
A major issue with any truck involving a separate bolster is that if the springs break or dislocate there is an immediate and catastrophic effect usually leading to derailment.
This type of truck was intended for a smoother ride and was widely used on cattle cars…
You should probably link a couple of images to show these, as I think you have a particular interest in many of these largely-forgotten late-1800s evolved truck designs. Some of the things that were tried to improve ‘ride’ as speed and load increased are ingenious but strange to modern eyes.
… with sets of elliptical leaf spring sets mounted with their length parallel with the swinging spring plank. The leaf spring sets were naturally stable in accommodating the oscillating spring plank…
For the record, the technical term for this is *full-*elliptic. These were extensively used on carriages where extreme light weight and substantial suspension excursion were expected. We are much more familiar with semi-elliptics using shackles to accom
You pretty much summarize the difference, and White will indeed provide any additional technical detail.
Swing-hanger trucks (whether inside or outside, a significant distinction when classifying passenger trucks) are intended to do one particular thing: put the point where actual lateral compensation is provided as low in the truck structure as practical. While the practical advantage of OSH in practice was not always ‘compelling’ over ISH (much as for outside-bearing over inside-bearing lead trucks) it isn’t difficult to appreciate the advantages for lateral control as well as minimized roll concerns from a good late OSH design (see the Nee Haven example in White’s The American Passenger Car (vol.2 if you have the separated version).
In a way this can be said to model the action in bolster support of drop-equalizer pedestal trucks (as seen on reefers and express cars in some head-end M&E-type service when good riding was expected).
Some of the fun is in distinguishing different functions of the truck, especially when (as in the Ohio trucks of sainted memory) it’s unclear that the designers themselves fully understood how the things were supposed to work. Note that even the assumption of pin pivot and two side bearers on the transom starts to be confusing when a ‘spring plank’ gets introduced: what precisely separates the imposition of load on the suspension from cushioning and restoring force of lateral shock and motion? As you recall this can get weird in tender trucks, and sometimes be overrationalized to m
Overmod has pretty well laid it out; the whys and wherefores of the advantages of coil springs vs. leaf springs.
“… A major issue with any truck involving a separate bolster is that if the springs break or dislocate there is an immediate and catastrophic effect usually leading to derailment…”
Derailment in any of its many phases is costly to the railroad it happens to. Coil springing while it might not be the perfect solution; is seeming more cost effective in the long run.
#1 The ‘Bottom Line’ is what the management constantly has its eyes on. #2 is the addage: “…If it ain’t broke, don’t fix it…”
With #1 and#2 there are no linitations on experimenting with, or testing a potentially ‘new’ way that might be a true improvement.[:-^]
Coil springs in most trucks are complimented by some sort of snubber or shock-abosorber to elinate the oscilation discussed earlier. This kind of damping is inherent in leaf-springs, as also discussed earlier.
By far the most popular streetcar trucks were the Brill 77, 177, and their derivatives, including the duplicate made by Third Avenue in their own E65th Street shops, but using some parts from Brill. Except for Cincinnati Car Co., even Brill’s competitors used these trucks on some of their production. On this brilliantly-designed truck, the half-eliptacle leaf sprint acts as equalizer bar as well as the main spring.
Keep in mind also that the action of a three-piece truck represents almost an ideal of what is required for effective running. One of the great demonstrations of this was the existence of trains like the Super C, which could routinely reach 90mph without requiring particularly special truck tuning or retrofit. Another was the short-lived expectation that lozenging was so serious a prospective threat to stack-train operation that X-shaped pinned reinforcement between the bottoms of the side frames would be necessary – from time to time I see trucks with the brackets, but no equipment in them.
One point about coils that may not be evident to casual ‘lookers’ is that there may be nine separate spring positions in the sideframe, any of which might have nested coils inside. Note that this facilitates the longitudinal rocking action that makes these trucks so flexible in cross-level following, allows much more metal in support (so each spring can have variable rate wound in for better load vs. unload riding) and, not least, failure or outright breakage of one spring poses almost no danger. The alignment of the side frames with the bolster is a critical part of the design, both to prevent lozenging/skewing resonance oscillations and to help damp side frame motion relative to the bolster – note that some lateral compliance can be included if desired.
I think the critical thing that makes long-travel swing motion on freight cars less ‘essential’ is improvements in line, surface, and LWR low-joint elimination in the ROW. Remember that no little part of the English disdain for equalized locomotives is predicated on ‘permanent way’ standards far higher than North American practice in the heyday of the swing-motion craze. (Things like the ‘Blomberg’ trucks are a bit different as they are leading under power, which is a different discussion).
BTW it is my opinion that you’ll see multiple thin leaf springs in many of the Blomber
I assume the “Ohio Truck” was a design was used only on tenders, and I have seen it in many photos of 4-4-0 engines in the Pioneering Era; with the most recent example being on CStPM&0 4-6-0s built around 1900. I sent a letter and a drawing to John White to inquire about it, and he was not sure of its origin, but thought it may have been called the “Ohio Truck.” So that is not much evidence for the name, but at least, it is one identifier.
I assume that truck design was specifically intended to produce an optimum ride for tenders, which White had described as being the most difficult rolling stock from which to attain a good ride.
The truck has no spring plank. It has a solid wooden transom connecting the two rigid truck side frames. Together, they would constitute the rigid “H” structure when seen in a top view. Then the loading of the tender is carried from the tender side sills, directly down to the tops of the four journal boxes through a large leaf spring on each side of the tender.
The truck does not transfer any weight down onto the transom through a center bearing as is typical of a truck with a bolster. Instead the Ohio truck has a form of center bearing that only keeps the truck in the proper position in the horizontal plane through a mechanical center bearing, but the bearing bears no downward axial loading. Its loading is only radial for the purpose of maintaining the truck location under the tender.
The tender does move up and down in relation to the truck by virtue of its suspension on the four end points of the two el
[C]
Althogh the Brill trucks saw wide streetcar use, they were very rare on interurbans and any rail cars thar ran regularly over 45 mph or carried any heavy loads. But they did cope better than some other designs with some imperfect track. In North America, before the PCC era, a majority of double truck and three-truck articulated cars had them.
Since Ron did so much of the legwork researching these trucks (a few years ago, in a very carefully-detailed thread on RyPN that has many pictures) I’ll let him continue a bit – he can, for example, talk about some very interesting changes that were made over the years to these trucks, many to provide stiffer lateral control of the high arched springs either at the toes or the perches, and to box in the toes where they bear on the H-frame. The ‘history in pictures’ of the high-speed years of NYC999 afford just such an evolution…
We put out a call for people to visit some of these tenders to make specific observations about the curve-following and cross-level ‘articulation’ (in the 4x4 sense) issues. That opportunity remains open today.
An unusual application of the Brill truck was the GE electrification of the narrow-gauge Boston Revere Beach and Lynn Railroad. Wood, open-platform coaches, very similar to typical Chicago, Brooklyn, and Manhattan elevated cars, were made into MU mutor cars with one of the two tracks replaced by a two-motor narrow-gauge Brill 77E truck. This left the car with a coil-spring MCB truck at one end and a leaf-spring 2-motor Brill at the other. Never head any complaint about this. Trailers did not have any trucks replaced.
Have not found a side-view photo showing this adequately. Hope another reader can and will.