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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Wed Mar 23, 2016 10:01 pm 

Joined: Sun Aug 22, 2004 8:51 pm
Posts: 1483
Location: Southern California
Yesterday, I sent a link for this thread to an acquaintance who normally does not read this forum nor other internet forums, but is knowledgeable about the CP and interested in 19th century railroading. He replied to me with this message:

"Interesting, thanks. I believe the Imperial Irrigation tender dates from the 1880s-early 90s when CP/SP converted a number of older locos into 0-6-0s. these were likely retired in the 1920s-early 30s, making the tender available."

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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Wed Mar 23, 2016 10:18 pm 

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While we are on this subject -- someone provide some clear pictures, drawings, and detail views of the six-wheel tender trucks CP used...

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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Thu Mar 24, 2016 12:05 pm 

Joined: Mon Jun 13, 2011 9:52 pm
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Location: Albany, NY
Ron Travis - It appears to me the IID tender sits on a true three point suspension. The 'equalizing beam' looks to support a center casting in the frame and the outer ends are hung in links that are clamped in the spring clamps (the links/beam ends are or should be free in the side frame casting guides), so the front truck is a single support point at the center casting. I doubt the springs contact the carbody to act as side bearings, but hard to tell from the available pics - they appear to suggest the side sills are made up of two plates far enough apart to allow room for the springs to move. The pin that comes up from the truck bolster into the equalizer is only for maintaining the centering/position of the bolster/side frame assembly.

The rear truck is centered/positioned by the ball & socket and the weight is carried directly from frame side bearings through the springs to the side frames.

The Stanford tender looks to have a modified three point, with the rear truck riding on heavier side springs that carry all the rear weight to two points with a center pin for centering/positioning.

The Stanford front truck carries most of the weight on the two transverse springs (instead of the IID's beam) with the lighter side springs also providing side bearing and secondary load spring functions.

Maybe Mr. Morris or someone else can shed more light on the IID front truck side bearing/frame design issue.

I had read about three-points on early tenders long ago but never had the chance to see any up close. Glad to finally see how it went together.


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Thu Mar 24, 2016 12:24 pm 

Joined: Sun Aug 22, 2004 2:46 pm
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Location: St. Louis, MO
Another example of this type of tender truck is at the Museum of Transportation in St. Louis County, MO. These are under the tender of C&NW 4-4-0 #274, built by Baldwin in 1873, later sent to the Winona & St. Peter RR, then back to the C&NW before to going to the Purdue collection in 1905. It came to the museum in 1951. It is also an example of a loco with two steam domes for more steam storage that was common at the time.

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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Thu Mar 24, 2016 5:13 pm 

Joined: Sun May 15, 2005 2:22 pm
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Train Detainer,

I hear what you are saying about that bar above the truck bolster in the one truck of the IID #151 tender. I just don’t see enough details to confirm that, and the theoretical explanation seems to pose unresolved questions about the details that I do see.

One of the unresolved questions goes to how the ends of that iron bar are attached, and the function of what they are attached to. The other unresolved question goes to how the top-center of that iron bar is attached, and the function of what is attached to. None of those details are shown in the photos.

Clearly, the iron bar slides up and down on the round pin. Is the pin solidly connected to the truck bolster or solidly connected to the tender frame?

The design of this general class of truck that I am familiar with has a telescoping set of cylinders at the center bearing location. One set is attached to the truck bolster, and the other set is attached to the tender frame. Then the tender side sills rest atop of the spring arch. Therefore with that familiar design, the telescoping center bearing does not carry any weight.

On the IID #151 tender, I see what you are saying about the springs appearing to rise higher than the side sills, but in that case, I assume that the overall structure of the side sill is supported by the spring, and the actual contact point is hidden behind the dropping, outer flange of the side sill.

In what you are describing with the big equalizing lever, the tender weight would be transferred to the center of that bar, and yet it appears to telescope there. How can it telescope and still carry a load?

If it is an equalizer lever carrying a center load, I guess it could accomplish that by having a ball or socket feature at the top side, center of the bar; and a corresponding ball or socket feature on the bottom side, center of the tender frame. That would transfer the load directly into the center of the bar which would then be free to rock for equalization.

However, how can the bar rock with that round pin entering a bore in the bar from the bottom? That round pin appears to have a fairly snug fit into the hole through the rocking bar.

And the larger question is this: Why would you need a telescoping joint at the truck center when you have a rocking bar fixed to the center point with a ball and socket joint? The ball and socket joint would keep the truck positioned on its pivot center as well as allow the equalizer to rock.


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Thu Mar 24, 2016 11:43 pm 

Joined: Wed Sep 25, 2013 12:36 am
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Location: Anchorage, Alaska
I already posted the first photo. The circle shows where the cross equalizer hangs from the bottom of the spring and supports the weight of the front of the tender. (Cross equalizer may not be what CP called it. I call it that because is similar to the cross equalizer at the front of the suspension of our Consolidation.)

The two additional photos give a bit different view. I haven't' tried to tell whether they are of the front or rear truck.

Note that the first couple of photos of IID #551 in the thread show the frame at the front truck is bent next to the spring clamp. That suggests to me that the spring is not firmly secured. A different view of the spring hanger is shown in those photos.


Attachments:
Spring hanger.jpg
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side.jpg
side.jpg [ 86.65 KiB | Viewed 995 times ]
side 2.jpg
side 2.jpg [ 120.35 KiB | Viewed 995 times ]
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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Thu Mar 24, 2016 11:55 pm 

Joined: Wed Sep 25, 2013 12:36 am
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Location: Anchorage, Alaska
I found a drawing of the tender for CP-229 (circa 1882?) that the late Charlie Dockstader sent me a number of years ago. Charlie was a master modeler of live steam models and built operating 1/8 scale models of CP-229 and El Gobernador. He also designed and placed in the public domain a simulation program that covers at least 20 types of locomotive, tractor, and steam boat valve gear, including one of Stevens' designs.


Attachments:
CP-229 tender - reduced.jpg
CP-229 tender - reduced.jpg [ 157.44 KiB | Viewed 995 times ]
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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Fri Mar 25, 2016 11:55 pm 

Joined: Mon Jun 13, 2011 9:52 pm
Posts: 42
Location: Albany, NY
Quote:
In what you are describing with the big equalizing lever, the tender weight would be transferred to the center of that bar, and yet it appears to telescope there. How can it telescope and still carry a load?

If it is an equalizer lever carrying a center load, I guess it could accomplish that by having a ball or socket feature at the top side, center of the bar; and a corresponding ball or socket feature on the bottom side, center of the tender frame. That would transfer the load directly into the center of the bar which would then be free to rock for equalization.


Mr. Travis -

This appears to me to be the way it goes together, with some guesses in the rear truck where we can't see how the castings connect the side frame to the truck bolster or the spring guide/spring interface. It isn't to scale since I have no measurements, and I exaggerated a couple of things for clarity. The two trucks are different, but all loads to the truck frames pass directly from the spring ends to the pad atop the journal boxes (not shown). Note the difference in side sill bolt/rivet patterns between front and rear, suggesting different types of frame spreaders.

The front truck provides the 1st of the three load points via the center plate and beam to the hanger links incorporated into the spring bundle. The top of the beam doesn't telescope, it is the center plate bearing for the truck. Only the pin that rises from the truck bolster telescopes into the beam and acts as a guide to stabilize uncompensated motion between the truck frame/springs and beam, with most of the motion taking place at the center plate/beam contact like a more traditional truck mount. The spring bands on the front truck appear not to contact the side frame plate in the more recent post and probably act as non-constant-contact side bearings to improve overall stability somewhat.

The rear truck provides the 2nd and 3rd (side) load points at the frame/spring-clamp contact point. I see what looks to be a rubber liner in the rear truck center bowl that I would assume is for additional flexibility and assume the ball does not normally contact the bottom of the bowl on the truck bolster as shown. I think there is probably some type of slide on the back of the spring bands on this truck that is guided by the vertical channel you see attached to the top frame casting to help keep the springs in proper location.
Attachment:
IID 151 suspension.jpg
IID 151 suspension.jpg [ 139.51 KiB | Viewed 947 times ]


Mr. Morris -

It appears to me that the pic labeled 'side' is the front truck (engine step visible and sun/shadows reversed from 'side 2') and 'side 2' is the rear truck (frame bolt pattern, no engine in background, and corner of rear kick-board visible). The fact that neither is in complete shadow would put both views on the right side of the engine.

Since the spring groups on the front truck have no guide or stabilization, their position relies entirely on having weight constantly on the hangers and spring ends, so if the tender rocked violently or was otherwise lifted and set down (or dropped) without attention to keeping the springs vertical, they could rock either direction and have the side frame land on them. With their advanced age, I would guess that there's quite a bit of wear that would prevent the springs from staying vertical with or without a load.

Another observation is that 151's front truck bolster appears bent (and probably broken) in the 'kingpin and cross equalizer' pic, with the left side frame accordingly tilted in the 'front journal' pic. Also, note the welded up holes on the side sill above the rear truck and new rivet pattern. Frame repair for worn out spring pad?

The CP229 drawing is interesting in that it shows two identical trucks similar to IID151's rear truck. Maybe they tried doing away with three-point on this one?


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sat Mar 26, 2016 2:22 am 

Joined: Wed Sep 25, 2013 12:36 am
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Location: Anchorage, Alaska
Train Detainer - I think I agree with your description.

My understanding/recollection is that the weight on the front truck passes from the car bolster to the cross equalizer. The ends of the equalizer hang from the center of the springs by the bands around the springs, where the weight is transferred to the springs. The ends of the springs transfer the weight to the casting above the journals and the ends of the springs are able to move fore and aft on top of the journal as the springs are compressed or relaxed.

On the rear truck, the weight is taken from side bearings on the underside of the frame which rest and slide on plates on the top of the springs so the truck can pivot. The ends of the rear springs are able to move fore and aft on top of the journal as the springs are compressed or relaxed.

The ball joint (or maybe more of a cup) on the rear truck locates it side to side and front to rear but does not transfer any weight.

Although it appears to be bent, I don't believe the front truck bolster carries any of the weight at the center. In 135-140 years almost anything could have caused a bend. Since the side frames and truck bolsters are rigidly attached to each other an incident causing a twist of the side frame could have sprung the bolster.


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sat Mar 26, 2016 1:03 pm 

Joined: Sun May 15, 2005 2:22 pm
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Train Detainer and Dick Morris,

Thanks for adding some more information. The drawings in particular are very helpful in communicating the details. I have been curious about this type of truck for quite some time, and have picked up bits of detail along the way. I have done some cad modeling to help clarify the design, and I have noticed that there appear to be some variations in the design while still following a core principle.

Overall, these trucks strike me as a radical departure from more common practice, so it is surprising how popular they once were. It is also surprising how obscure they seem today despite that popularity. So I am very interested in the photos provided here because they contain lots of information, and some of it is new to me. I would like to understand and clarify it as much as possible.

My basic assumption about the majority of these trucks in general is that the tops of the springs carry the weight of the tender transferred from the tender frame at the sides. I call those features “side sills.” Also, that weight transfer point is a sliding contact as shown in the line drawing of the tender of CP #229.

One general point involves the concept of three-point suspension. I have seen some close-up video/photos of the Kloke Leviathan tender, which appears to have such three-point suspension, although I would have to review that to refresh my memory. As I recall, that tender has one truck of the type under discussion here, while the other truck of the conventional arch bar type with sprung bolster, coil springs, spring plank, etc. What is unusual about the one truck of the type discussed here is that it appears to have a very precise fitting, telescoping center bearing; almost looking like a pneumatic or hydraulic cylinder with a polished rod being perhaps 6-8” diameter. I had assumed that this truck follows the basic design that I have understood, but is just more refined with better fit and precision of the center bearing.

I see that the IID #151has two different trucks under the tender, and this may also be related to a three-point suspension, but I have several questions about both of them. For now, I am focusing on the one with the secondary iron bar above the bolster of the truck. I have several thoughts that I just want to throw out for consideration, and not as final conclusions.

If the iron bar showing in the photo is an equalizing lever, the top of the bar near each end cannot be contacting the tender frame. In fact it would need maybe 4” of clearance to the tender frame in order to accommodate the rocking action. I can’t tell how much space there is between the rocking bar and the bottom of the tender frame at the side sill. Although, I suppose it would be acceptable for this tender frame to bottom out on the top of the spring, producing the effect of a non-constant contact side bearing.

Likewise, there would need to be similar clearance between the bottom of the bar near each end, and the top of the truck bolster. Looking at the photos again, I can see that it does appear that the ends of the iron bar are hung from the bottom of the spring bundle. That large, central casting which is part of the truck side frame, appears to have a recessed pocket at its top to clear the ends of the iron rocking bar as they drop downward past the top of the truck side frame.

In any case, it does seem apparent that the iron bar is a rocking equalizer, although there is some remaining mystery surrounding the details at the center of the bar where it connects to the tender frame.

So the truck with the equalizer bar is a two-point suspension truck. There is another version of this basic truck design that does not have an equalizer bar, and it too is a two-point suspension truck. Judging from the available photographs, there must have been thousands of these basic trucks in use. It would be interesting to know how many had the rocking equalizer, and how many just used the tender frame as the rocking equalizer. Note that I am referring here only to the two variations described. The truck with the ball joint center bearing would be a third variation, but I am setting that aside for later comment.

While the iron bar apparently is a rocking bar equalizer, it is hard to see what advantage it offers over having the tender frame be the rocking equalizer as it loads its side sills onto the tops of the springs; as is the case with many of this general type of truck without dedicated equalizer bar. Perhaps there may be an advantage in keeping the spring set more stable by hanging the load under the spring rather that compressing the spring from above. Since both types of truck design are two-point suspension, I assume that both types were could be used on tenders with four-point suspension.

Therefore, on a four-point suspension tender, you could have two trucks with equalizing levers, two trucks without equalizing levers, or one of each. Many photos of tenders with this type of truck in general show two perfectly identical looking trucks under the tender. Whereas, it seems likely that tenders with three-point suspension would show differences in the outer appearance of the two trucks, even though they both use the big elliptical leaf springs. On the Leviathan, I seem to recall that the two trucks appear to be quite different since one has the leaf springs and the other does not.

So the IID #151 has one truck with a dedicated rocking equalizer lever, which may or may not be atypical for this general type of side bearing truck. It also has another truck that appears to have a ball joint at the center bearing. So, at this point, we are talking about three different variations of this basic side bearing type of truck. I am going to further ponder the truck with the ball joint.

A relatively late version of this type of truck was shown and described in an article by Joseph Follmar in the fall 1995 (Vol. 22, No. 4) issue of North Western Lines. The article was about C. St. P. & O. class I-1, 4-6-0s built around the turn of the century (i.e. 1901). This execution incorporates rather sophisticated castings, including raised buttresses to prevent the springs from tipping over.


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sat Mar 26, 2016 4:26 pm 

Joined: Wed Sep 25, 2013 12:36 am
Posts: 220
Location: Anchorage, Alaska
Quote:
Leviathan

Am I correct that Leviathan is based on the O'Conner Engineering Labs drawings done for the National Park Service for the Promontory locomotive? If so, using it as a source of historical practices and design may not be very helpful.

Essentially the entire drawing set for the NPS locomotive can be found at http://ibls.org/mediawiki/index.php?tit ... ocomotives. My perception in studying the drawings is that the NPS locomotives are not historically accurate copies of the prototypes, but rather operational full sized "model" locomotives made to look like the prototypes. For example, many pieces that would have been a casting in the prototype were fabricated out of plate or bar stock. There are also a number of pieces that are the same for the two locomotives or the same with only cosmetic differences.


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sun Mar 27, 2016 6:15 pm 

Joined: Mon Jun 13, 2011 9:52 pm
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Location: Albany, NY
Mr. Travis -

It seems to me you are trying to lump too many types of truck into this discussion about IID151's two distinctly different types. CPRR was a RR with its own ideas about equipment engineering, much like PRR, and I would argue that it is important to keep in mind that CPRR's notions of best practice didn't necessarily follow with everyone else's. Mr. Morris' statement about Leviathan and the Park Service's replicants is spot on and their design should be considered largely irrelevant to discussion of actual historic trucks/suspensions. I have not looked at the prints, but I have to believe that they were designed to use the basic historic concept but incorporate some modern features for ease of maintenance and reliability. It is well known that three point suspensions were common (particularly on tenders) in the era following the development of the 4-4-0, which was so successful specifically due to its use of that suspension to overcome the prevalent poor track conditions. If these trucks were developed in 1872 per WPE and in use in the 1880-1890 period as Brian Norden's friend suggested, the fact that CP229's design appears to show a four-point suspension in 1882 would indicate that this AJ Stevens design was rather late in the three-point game.

You seem to be confusing the front and rear truck designs. The front truck is not a side bearing truck. If it were, the tender would be a four-point suspension and there would be no reason at all for the beam. It would most likely be identical to the rear truck with the gapped ball and socket design and identical to the CP229.

Quote:
However, how can the bar rock with that round pin entering a bore in the bar from the bottom? That round pin appears to have a fairly snug fit into the hole through the rocking bar.

And the larger question is this: Why would you need a telescoping joint at the truck center when you have a rocking bar fixed to the center point with a ball and socket joint? The ball and socket joint would keep the truck positioned on its pivot center as well as allow the equalizer to rock.

Going back to your 3/24 @ 17:13 post, the front truck bears the tender weight on the centerplate/beam center and the beam transfers the weight to the springs which transfer it to the side frames above the journals. The post attached to the truck bolster (apparently fixed to the bolster with flathead rivets) telescopes into the beam and carries no weight to the truck frame. It is only for lateral and longitudinal (x,y axis) truck frame positioning and the beam and truck bolster pitch and roll (rock) together, just like any more modern truck with a flat centerplate bearing. The telescoping pin has to provide that vertical (z axis) movement between beam and truck bolster due to the changing distance between them due to spring motion. All vertical motion of the truck is related entirely to spring motion. As I stated before, it appears the top of the front truck springs do not normally contact the tender side sills, so there would be no normal load-bearing function there, making this a true three-point suspension.

Quote:
If the iron bar showing in the photo is an equalizing lever, the top of the bar near each end cannot be contacting the tender frame. In fact it would need maybe 4” of clearance to the tender frame in order to accommodate the rocking action. I can’t tell how much space there is between the rocking bar and the bottom of the tender frame at the side sill. Although, I suppose it would be acceptable for this tender frame to bottom out on the top of the spring, producing the effect of a non-constant contact side bearing.

Likewise, there would need to be similar clearance between the bottom of the bar near each end, and the top of the truck bolster. Looking at the photos again, I can see that it does appear that the ends of the iron bar are hung from the bottom of the spring bundle. That large, central casting which is part of the truck side frame, appears to have a recessed pocket at its top to clear the ends of the iron rocking bar as they drop downward past the top of the truck side frame.

The pics clearly show the ends of the beam not contacting anything but the links under the center of the spring groups and a fairly large clearance (probably all of 4") between the top of the beam ends and the tender frame - far more than the amount of spring motion would require. If the spring groups on this truck are in fact acting as free side bearings, the amount of clearance (and frame/beam lateral roll) would necessarily be minimal. If you look closely, there appears to be about 3/4" of free space between the bottom of the beam ends and truck side frame. This isn't much, but the springs on 151's front truck appear to be very old and probably very worn out at the ends, which I mentioned to Mr. Morris in the note about side sill damage. This truck is very old, appears to be mostly all original and in desperate need of rebuilding, so we have to keep in mind that it isn't sitting as it did when new. If I had to venture a guess, I would say that with new springs there was probably 1.25" of free space between beam ends and truck frame (based on the guide cup height), requiring a high degree of precision in manufacturing the spring groups. The spring rate and finished shape of the leaves/group would have to be very consistent for proper performance. This truck design is not very forgiving at all in that regard if I am correct.

Quote:
On the IID #151 tender, I see what you are saying about the springs appearing to rise higher than the side sills, but in that case, I assume that the overall structure of the side sill is supported by the spring, and the actual contact point is hidden behind the dropping, outer flange of the side sill.

I don't see this as a valid assumption. If you look at the pics of the side sills above the trucks, you can clearly see that the rear truck has a centrally located bolt above the spring group to hold the frame-mounted spring bearing (like the CP229 drawing shows). The sill at the front truck has an entirely different bolt pattern and no centrally located penetration for a bearing, so I take this as another sign that the side sill at the front truck acts only as an occasional non-contact side bearing.

Quote:
If it is an equalizer lever carrying a center load, I guess it could accomplish that by having a ball or socket feature at the top side, center of the bar; and a corresponding ball or socket feature on the bottom side, center of the tender frame. That would transfer the load directly into the center of the bar which would then be free to rock for equalization.

You keep referring to a ball and socket for the front truck, which appears to in fact be a plain centerplate bearing (albeit upside down from modern practice and a PIA to keep lubricated). I could be wrong and the bearing might indeed be a ball and socket shape, but still it would be constant contact and load bearing, unlike the rear truck. The rear truck very clearly has a ball and socket type connection, and this seems to be a point of confusion. The rear truck ball and socket would have to be gapped as I drew it (and probably a bit more) in order to provide the vertical movement between tender frame and truck frame as there is no other mechanism for it. This gapped ball and socket arrangement accomplishes the same function of the telescoping post on the front truck - x,y axis positioning of the truck frame relative to the tender frame. Further evidence of this is that the rear truck bolster appears to be slightly twisted in the pics on either side of the center casting, indicating the truck was shoved forward at some point beyond the bolster's moment.


It does not appear to me from the pictures that CPRR hardware complied entirely with M.C.B. standards (would be early for M.C.B. in 1872) and I would be interested to know the truck dimensions, particularly journal size and side frame centers. Another question - has anyone seen three point tender suspensions with the two points in front and the single at the rear so that the suspension over loco/tender would be 1-2-2-1 instead of 1-2-1-2? Does anyone have close contact with IID151's owner that could verify any of this discussion?


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sun Mar 27, 2016 6:56 pm 

Joined: Thu Mar 13, 2014 2:34 am
Posts: 419
Location: Port Jefferson, NY (LIRR MP 57.5)
The more I look for these trucks, the more I find them -- or at least trucks of similar design -- and sometimes in unexpected places.

For example, on the Woodstock Railway in Vermont:
Attachment:
WoodstockRwy_JGPorter.jpg
WoodstockRwy_JGPorter.jpg [ 336.76 KiB | Viewed 849 times ]


I haven't been able to find much on this engine's history, but from the rectangular builder's plate and round domes I think she may have been a Schenectady, which goes back to WPE's comment on the previous page on the similarity between Schenectady and Central Pacific tender truck designs.

(I have seen this photo before, but will admit I had never paid much attention to the tender trucks.)

-Philip Marshall


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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Sun Mar 27, 2016 9:01 pm 

Joined: Wed Sep 25, 2013 12:36 am
Posts: 220
Location: Anchorage, Alaska
I got a few dimensions from the IID #151 trucks. The side frame top bar is 1" thick, the arch and bottom bars are 7/8". All are 4" wide. The space between the bars for the journals is 8-1/4". The two columns/bolts at the side of the large center column casting are spaced at 6-1/2". The three columns at the side are spaced at 5". The main bodies of the journal castings are 7-1/2" wide and hole spacing for the covers is 8-1/2". I measured wheel base at 44-1/4". The tank is 17' long.

Attached is a partially completed model which shows my take on what the casting on the top of the front truck looks like. (The piece of the lower part of the truck bolster sticking out still needs to be trimmed.)


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Model truck.jpg
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 Post subject: Re: Early Central Pacific Tender Trucks
PostPosted: Tue Mar 29, 2016 3:56 pm 

Joined: Sun May 15, 2005 2:22 pm
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Train Detainer,

Maybe I am overcomplicating the discussion as to how these trucks fit into the general practice of the time. That is just how I perceived the topic as being continued out of that other thread. There, it was about the generic truck type and we talked about specific examples. So I did not understand the topic of this thread to be only about the trucks on IDD #151.

Both of the trucks on #151 are different than anything I have learned about the basic generic design that I mention, although they both appear to be variations of that basic generic design.

I had not given any thought to which truck is front and which is rear in what I wrote. I have tried to refer to the two trucks as the one with the equalizer lever, and the one with the ball joint. I might have also misstated which one was single point suspension.

On page 1, when I referred to a ball and socket joint on the truck with the equalizer, I was doing so only hypothetically in absence of any indication by the photos of the detail of the connection between the rocking lever and the bottom of the tender. Being that one truck definitely appears to use a ball joint, I was assuming that the rocking lever might likely use one as well. Do we know for sure that the one evident ball joint does not carry load?

For as intriguing as the mechanical details of these two trucks are, the design theory is also quite a challenge to absorb. Generally the design objective of these trucks and their relatives of this era seems to be to provide the greatest ride stability with the greatest ability to accommodate track irregularity.


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