Friday, December 16, 2016

SP Tender Swapping (Part 1) - A Game for Prototype Modelers

Prototypical modeling of SP steam engines means more than just learning about the different wheel arrangements of the engines and differences between the different classes within a wheel arrangement.

The SP Mechanical Dept. inherited the Common Standard system of classification.  Much like the passenger car classification system.  This system used a combination of numbers, letters, followed by more numbers.  For example 120-C-2 means the tender has a water capacity of 12,000 gallons, it has a cylindrical tank construction, and is the second class of such specifications.

A general note should be made that the SP moved to put 'high speed' trucks under tenders assigned to faster passenger engine types of engines.  Most SP classes after about 1930 that continued to be used in high speed service had 6-wheel trucks assigned to them.  The slower freight engines and road-switchers used the 4-wheel trucks (120-C-2 and -7) and Andrews-style trucks on the smaller tenders.

Overview of Tender Classes

Let's have a quick look at some common models of various SP tender classes.  This will give us a basis to follow a few easy tender swaps.

Some of the tender classes I will be showing.

Cylindrical Tenders

Tenders Smaller than 90-C-series

There were a number of tenders built in this group.  I will not be talking in depth at this point about tenders that are smaller than 9K.  Most of these tenders fall into the 70-C-seriers of tender.  Over the years these were modified and placed behind smaller and smaller engines, generally ending up behind engines assigned to switching service or requiring short tenders to fit on smaller turntables.

70-C-1/2 Class

A retired SPMW 70-C-1/2 tender from MDC/Roundhouse kit with full-width fuel bunker.

Most of these tenders became fodder for rebuilding into the later 70-C-9 and -10 class switching tenders with narrowed fuel bunkers.

70-C-9 Class

70-C-9 tender from Sunset S-8, -10, -12.

3/4 view of the narrow bunker on the 1213's tender.

The only one that I'll talk about this time is one from the SP 1213, which was one with the modified bunker which was narrowed for better crew visibility when looking to the rear while switching.


SP 70-C-10 tender on the left, with a 70-C-9 on the right. - Both Sunset Models tenders.

Sunset Models imported 70-C-10 class tenders with their 2-6-0s among other engines.  The SP's 1950 tender roster only shows two of this tender class in service, compared to 50+ of the 70-C-9s.  The -10 class has a rounded fuel bunker, which follows the side of the tank and probably simplifies the narrowing of the bunker.

Moving on...


Tenders with a nominal 9K gal water tank, cylindrical design.

90-C tender with low walkway boards - Sunset

The tender above came with a 1980's Sunset C-9 class 2-8-0.  It turned out that this tender wasn't what the C-9 needed to match the photo I had of the engine I wanted to do.  Turns out that the Balboa 100-C "Alternate" tender (seen below) from a Mk-5/6 was the right tender for the C-9.  This tender then became a "spare".  Recently I traded it with a friend for a WSM 100-C "Common" tender (also seen below).

90-C tender from SP 3000/3001 A-6 by WSM/KTM

This Daylight painted 90-C tender is from a A-6 class 4-4-2 from WSM/KTM.  Two engines 3000 and 3001 were painted with Daylight colors on the cab and tender for use on the Sacramento Daylight in 1941.

Moving on...


Tenders with a nominal 10K gal water tank, cylindrical design.

Left - WSM "common" tender & Balboa "Alternate" tender with replacement trucks from Mk-5/6.

Above are the following two tenders placed bunker to bunker to show the differences in the bunkers of the two tenders.  Notice the one on the right has a longer and shallower slope sheet than the one on the left.  While this is subtle, it can be noticed in photographs of the real engines... and with the right model, you can replicate this as well.

100-C-3/4/5/6 (Common)

100-C-series tender - by WSM/KTM - These are VERY common models.

These are certainly one of the most common tenders behind the large numbers of WSM/KTM models imported over the years.  These are standard behind the models of T-28, T-31, P-4, P-5, and others.

This is the type of tender my friend traded to me for the 90-C above, it will soon find a home behind some other medium or small SP steam engine.


SP 8200-8238 (39 tenders, inclusive)


SP 8330-8449 (120 tenders, sans 8333, 8334, 8366 as of June 1, 1950)


SP 8450-8458 (9 tenders, inclusive)


SP 8194-8199 (5 tenders), 8459-8489 (61 tenders)

100-C-1/2/7 (Alternate)

100-C-1/2/7 with more angled fuel bunker - by Balboa from their Pacific Lines Mk-5/6 model - Wrong trucks.


SP 8000-8052 (31 tenders, sans 8003, 8006, 8009, 8010, 8011, 8013, 8017, 8018, 8019, 8021,8023, 8024, 8025, 8027, 8038, 8042, 8045, 8047-8050, as of June 1, 1950)


SP 8100-8124 (25 tenders)


SP 8490-8499 (10 tenders)

Balboa's Mk-5/6 "Pacific Lines" Medium 2-8-2 comes with this slightly different version of a 100-C tender (100-C-1/2/7).  It can be seen in photos of other engine types.  The trucks however are always the standard SP Andrews tender truck, so replacement trucks are in order.

100-C-1/2/7 class Balboa tender from Mk-5/6 with replacement Andrews tender trucks.

The Mk-5/6s seem to have lost these tenders before the late 1940s, so modeling a Balboa Mk-5/6 will also involve looking for a different tender.

This it turns out was the correct tender to have behind the C-9 (2-8-0) that I wanted to model, so my first tender of this type went to it.  A number of C-8/9/10 engines have this style of tender, with the heavy angle in the bottom of the bunker and the shallow slope angle of the bunker being easily spotting features.

The next larger series of tenders were more numerous in classes and all were rather distinctive...

12000 Gallon Tenders


Sunset "120-C-2" with trucks from 120-C-1 - oops!

SP's 120-C-1 tenders were all rebuilt into 120-C-7 tenders and reused most of the parts including the same trucks.

The 120-C-1s used the trucks that Sunset Models put under the 120-C-2 tenders below.  This means that the Sunset Models 120-C-2s are actually closer to 120-C-1s in appearance.  This issue applies to the tenders imported for Sunset's 1990's production of painted SP F-3/4/5s and also the older unpainted F-1s, Mk-2s, & Mk-4s as well.


Note: that the 120-C-2s are the first SP tender class here to use a longer 6'3" wheelbase 4-wheel truck with a longer wheel base than the Andrews-style trucks shown above.  The 120-C-2 tenders had trucks with clasp brake shoes which were hung from longer horns at the ends of the truck side frames.

The trucks on the model below make these models more correct for the 120-C-1 class tenders as noted above.  The other option is to trade these trucks to other tenders to make more correct combinations.

120-C-2 extra tender from Sunset's importing of their F-3/4/5 series engines during the 1990s. (should be 120-C-1 model)

The 120-C-2 tenders were very common behind Mk-2, -4, -5, & -6 class 2-8-2s, all classes of 2-10-2s (especially the F-1s).  They were not commonly used behind passenger engines such as the Pacifics (P-series) or Mountains (MT-series) because of the 4-wheel trucks.

SP 3259, a heavily modified Balboa Mk-5/6 with a new 120-C-2 tender.

I believe one of my first 120-C-2s came from a Sunset F-5 class 2-10-2.  It was quickly traded to a Balboa Mk-5/6 the SP 3259, which had correspondingly had traded its alternate 100-C to the C-9 (mentioned above).

120-C-3 & -6

Athearn-Genesis 120-C-6 tender (unlettered)

Athearn's after-market tender-only model of a 120-C-6

There's nothing saying that you have to use a brass tender with a brass model or a plastic tender with a plastic model.  Thanks to Athearn bring these tenders out separately, we can now give models an upgraded tender, which many engines after WW2 received.

This class was very common behind SP 2-10-2s of F-3 & -4 classes, MT-1,-3,-4,-5 class 4-8-2s, 2-8-2s in Mk-5 & -6, later class 4-6-2 Pacifics (P-8 & P-10 especially), Even a few C-class 2-8-0s received these big tenders - and looked rather strange after words!


The 5th class of 12K tender SP ordered was different in that the fuel bunker sloped all the way up and to the rear until it meets the top of the tank.  The tank sides are also vertical, but set in from the sides of the bunker.  This results in a VERY distinctive tender, which is easy to spot in photos.

Side view of 120-C-5 WSM model

The 120-C-5 tenders were ordered for delivery with the SP's big 4-10-2 (SP-1,-2, & -3) engines of the 5000-series.  They then started wandering around to assignments behind other smaller engines as the SP-class engines were upgraded with 160-C-series tenders fairly quickly.

120-C-5 rear 3/4 view of WSM model

Also see 120-C-7 and 120-C-8 classes below.


This class of tender I believe could be kitbashed from a 120-C-5 with an additional bunker top, such as the 160-C tender have.  The tender will also need a set of 4-wheel trucks.

These tenders were common behind mid and large sized SP engines, F-class (2-10-2) and Mk-5/6 series engines also.


This class of tender I believe could be kitbashed from a 120-C-5 with an additional bunker top, such as the 160-C tenders have.

These tenders with 6-wheel trucks were common behind P-class (4-6-2), F-class (2-10-2), and Mt-class engines.


These tenders, the largest of the cylindrical type tenders, had what was called a "water bottom" frame.  The frame was actually part of the tank.  This allowed for a flat bottom and top to the tank.  These tenders are sometimes referred to as "semi-cylindrical" by some railroads... however on the SP the SC-type tenders as they're called referred to something completely different as we will briefly see below.

160-C tender from Sunset

The 160-C series tenders were used both with AC-4, -5, & -6 and large conventional engines of SP (4-10-2), F (2-10-2), GS-1 (4-8-4), Mt (4-8-2), and even a few of the T&NO's large Pacifics.

160-C tender from Sunset, rear 3/4 view

The 160-C-series tenders from retired AC-4, -5, & -6 engines were handed down in the early 1950s to equip more F-class (2-10-2) and Mt-class (4-8-2) engines with larger tenders.  By 1954, many 2-10-2s working the San Joaquin Valley freight pool had 160-C tenders instead of their smaller 120-C tenders.

Rectangular Tenders

The rectangular tenders the SP owned will be discussed later in more detail.


Intermountain 220-R tender from an AC-10, -11, & -12 model.

These tenders were specifically built for use with the late model AC-class (4-8-8-2) engines.  Note the T-handle on the oil bunker lid.  This was to lock the lid down so the fuel bunker could be pressurized to 5 PSI, forcing the heated fuel oil to flow the extra distance up to the firebox.  This was also standard on the 160-C and 120-SC tenders assigned to the earlier AC-class and AM-class cabforwards.


There were several tender classes in this volume series.  Some of these big tenders were bought from the C&O and used with the AC-9s and some other large classes, such as the F-5 class (2-10-2).

Semi-Cylindrical Tenders

"Whaleback" SC-series Tenders

These tenders are very uniquely SP in design.  They're used behind many classes of SP engines including the larger ones behind early AC-1, -2, -3, AM-1, and the tanks of this style installed on the ex-B&M 2-8-4 (SP class B-1).  Smaller versions of this tender were commonly seen behind other smaller classes.  I will not be going into very much depth of this type of tender in this post.

120-SC-series tenders are arch-topped tenders.

73-SC & 78-SC-series

An Oriental 73-SC-type "Whaleback" tender.  Similar to Sunset and other importer's models.

This class was most often seen behind C-class 2-8-0s, M-class 2-6-0s, and the occasional S-class 0-6-0s.


These tenders came from retired AC-1, -2, & -3 (2-8-8-2) and MC-1 (4-6-6-2)  class Cabforwards.

120-SC-series tender with as-built straight profile

These tenders also show up behind Mk-5 & -6, Mk-7 & -8 (Ex-EPSW) 2-8-2s, F-1 2-10-2, and even C-class 2-8-0s.

Swapping Tenders

Swapping tenders between different classes and engines within a class was a very common practice on the SP.  Many models are build with one, maybe two types of tenders.  Often the older brass models get the "Standard" tender from that manufacturer or importer.

Unfortunately this is the best photo of the original configuration of SP 2850 that I have, circa 2004.

This is the original Sunset tender that came with the 2850.

Around the same time I picked up a Balboa Mk-5/6, which would become the SP 3259.  However it had a very weird little tender that didn't last on Mk-5/6s past about WW2.  Looking at photos the SP 2850 had just such a tender... although with standard Andrews trucks, not the more "express" style trucks of the Balboa model.

Ah, but wait, here's that extra Balboa Mk-5/6 tender

And again with replacement trucks

The SP 2850 now has the correct tender... but what about the Mk-5/6 that gave its tender up?

SP 2850, with Balboa Mk-4 tender (100-C "Alternate") weathered with 'mud' which nicely matches the Caliente scenery at LMRC.

Buying that Extra Tender

Some importers have commissioned extra tenders to be made, so there are extra tenders that wander around on the market.  The SP 3259 could have received a replacement or "extra" tender from a hobby shop, train show, or ebay such as this 120-C-2 from Sunset, below.

This is an example of a Sunset 120-C-2 tender that can be found by itself if you need an extra tender.

In reality, I ended up trading another friend for a Balboa 160-C tender that I had, in exchange I received a 120-C-2 Sunset tender.  The Balboa engine received a PSC 120-C-3/6 tender that I acquired.  This was all in the days before Athearn-Genesis released their fine 120-C-6 tender.

An unpainted Balboa Mk-5/6 with 100-C- "alternate bunker" tender

Comparing the photo above and below, one can easily see that Balboa's Mk-5/6 with the 100-C tender was trying to be a 120-C-2 tender, but somewhere they got the idea that the 100-C with the "alternate" bunker was the same tender as the 120-C-2 tender, and tried to put some other trucks they had on hand under.  In any case, this just means a bit of extra work for us finding a new tender.

SP 3259 is now happily re-equipped with the correct tender and returned to service

Well, here's another example.  Another Balboa Mk-5/6 again with an extra 100-C tender that will be handed down to some other smaller engine needs a new tender.  This time an Athearn 120-C-6 is selected to match the SP 3266.

Athearn-Genesis 120-C-6 tender can be bought today from a hobby shop or special order for your tender swapping needs.

SP 3266, with a new Athearn-Genesis 120-C-6 tender which was bought undecorated and will soon be decalled.

In both of these cases the model is made correct to the prototype photos and information by acquiring an extra tender.  The old tender can usually find a home with another engine or be reused in maintenance of way service.

An SP 60-C tender with full-width oil bunker (MDC/Roundhouse) in SPMW service

The SPMW 8241 is a model of a tender retired from assignment to a locomotive, and now is assigned to a steam crane or pile driver.  Some old tenders were reassigned to rotary snow plow service or water service after the end of steam.

The Direct Swap

The other option is to find the right two engines that have the wrong tenders and do a straight swap.  Some of my earliest engines happened to have the right tenders for each other.

A 160-C tender

A 120-C-5 tender

A Sunset F-5 came with a 160-C tender, a Sunset Mt-3/4 came with a 120-C-5 tender.  The Mt's almost exclusively didn't use 120-C-5 tenders after about 1946 according to the photos I had.  The number I would choose would need an Mt with spoked main driver, standard crosshead guides, and skyline casing.  I found two engines that were photographed with 120-C-5 tenders after 1946... however they both had either multiple bearing crossheads or replacement disc main drivers.  Neither of those options sounded like fun to fix.

Here's the 4341 with its new replacement 160-C tender.

The Sunset 2-10-2 F-5 class engine that I had (SP 3727), was needing a new number anyway as another member beat me to the number!

An SP F-5 class 2-10-2 waiting for a new number and tender

I looked though some photographs.  SP 3757 was photographed with a 120-C-5 tender.  The rest of the engine details seemed to match up with the model of 3727.  So I redecalled the F-5 by changing one number.  The tenders were easily swapped and patched to change the numbers on the rear of the tanks.  A few years later, and upgrading to DCC required me to change the engine yet again because of a conflicting DCC address with another engine.  This is especially an issue now with DCC.  In a way this was a cloud with a silver lining as it would give me the chance to find another number.

In the end this is a great example of two engines getting a direct tender swap and the owner coming away with two correct models at the end of the day.

In Closing

SP 3203 with swapped 120-SC-series tender arriving at Owenyo.

These games of musical chairs with tender can evolve quickly into three or even four tender trades to get all the engines ending up with historically correct tenders.  While sometimes these can result in easter egg hunts that may last years, they are often very rewarding when finished.

Jason Hill

Related Links:
Modeling SP's Steam Road Switchers (Part 1) - Light

Modeling SP's Steam Road Switchers (Part 2) - Medium

1 comment:

  1. Lots of great information and entertaining stuff. Very helpful for my 1950 steam era modeling of SP passenger traffic, Sacramento area.

    Jim Eaton


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