Body Mounting Kadee 907 Centersets to USA Trains Bay Window & Extended Vision Caboose


Body Mounting Kadee 907s to USA Trains Bay Window & Extended Vision Caboose (Without using a glued on coupler pad block or cutting the caboose body)


Ted Doskaris

Rev GE-A,

June 1, 2013

Rev GE-B,

June 2, 2013, corrected part no. typo error. & deleted redundant pictures

Rev GE-B1

November 18, 2016, fixed broken link to vignette, Aristo Covered Hopper...

Rev GE-C
May 26, 2018, Prompted by repair of acquired used caboose, added:
Appendix A, Disassembling the Caboose
Appendix B, Battery Access & Possibilities


The Rock Island blue Bay Window Caboose shown below is my first USA Trains caboose purchase.



This caboose includes factory standard blackened metal wheels housed in typical USAT plastic Bettendorf freight trucks with sideframes having molded in "hot boxes" and 70 ton coil spring pack.


Having examined several sources, it seems a prototype caboose can employ trucks with roller bearings and will have leaf springs rather than coils like the "Barber - Bettendorf" truck shown below.


Shown below is the Bay Window (Blue Rock Island) and an Extended Vision (Red/white Santa Fe) caboose together on a track. These appear to be modeled from the prototypes made by International Car Company. Like the prototypes, they share similarities - but for the obvious differences in bay window vs. upper copula. Both models shown here have been fitted with body mounted Kadee 907 centerset couplers - done using a common method but with a different variation.



The Santa Fe Extended Vision Caboose is my first of this type, too, it being purchased from Greg E. as it was too new for his preferred modeling era. As received from Greg, the Bettendorf trucks in this caboose are equipped with aftermarket LGB metal wheels (LGB67419) with the inboard axles (LGB67403) having the ball bearing version with electrical pickups. The caboose with these wheels rolls effortlessly compared to the drag of standard USAT wheels with friction electrical pickups like the new Rock Island one; however, the LGB wheels measure 0.100 inch larger tread diameter compared to the USAT wheels, resulting in the caboose being raised up by 0.050 inch.



As factory equipped with the same wheels, the two types of caboose have close similarities and seemingly have the same height from the rail head. These pictures show both caboose types on 8 foot diameter track with the Santa Fe one actually being lowered to not only correct for the wheel difference, but to be somewhat closer to prototypical height from the rail head, too.



Body mounted Kadee 907 centerset couplers are installed on these without needing "glue blocks" or making any cuts to the caboose body.



Since prior art methods employing a "glue block" for a mounting pad is NOT used, you can see through the platform floor grates with the couplers mounted. The blue / white one is the Rock Island Bay Window caboose, and the red one is the ATSF Extended Vision caboose.



I decided to use different ways to body mount the Kadee 907 coupler boxes using variations of the same method.


One way is to mount the coupler box with minimal projection from the end sill of the caboose whilst allowing full swing capability of the coupler. This was done on the Rock Island Bay Window caboose.



If the draft gear box were to be mounted more into the recess than that shown in the above picture, the coupler's knuckle would be limited in its swing on one side, hitting the "cut lever".



The second way is to mount the box inverted and projected out more, thus, emulating a "shock control" draft gear box as was done on the ATSF Extended Vision caboose shown below.



As these different type cabooses come from the USAT factory, it does not matter which way is done to them since they share the same under body structure and platform / end sill detail.



Now for the method variations:


In order to body mount the Kadee centerset couplers without cutting the caboose or having to use glue blocks is fairly simple and basic.


1) The coupler tang is cut off from the truck and slightly modified for body mount use.


2) A "gull wing" plate is fabricated that the coupler tang is attached to.


3) The Kadee 907 coupler box is attached to the tang like it would be when truck mounting - making use of the "nub" that fits into the tail of the box as intended. This whole thing now becomes a subassembly.


4) The whole subassembly is mounted on the underbody frame using two existing screw hole locations.


5) The tail of the tang that extends beyond the fabricated plate includes an adjustable screw that becomes a third leg that touches the underbody floor. Thus, the coupler end of the subassembly can be held against the end sill of the caboose without the need for an attaching fastener at that location. The tail screw, also, serves as a leveling adjustment for achieving proper coupler height from the railhead.




6) The coupler box can be installed inverted for better emulating a prototype "shock control" or cushion type caboose.




The conventional box with orientation is described first, then an inverted box example will be described.


Simple Method - with Conventional Coupler Box Orientation:


The drawing shown below is how the Rock Island Bay Window caboose was done. This is fairly easy to do.



The following pictures serve to illustrated installation of the coupler subassembly:



When done, the Kadee 907 centeset coupler is to align with the Kadee 980 gauge for proper coupler height to rail head distance.



The height of the Bay Window caboose measured about 5.08 inches from the catwalk to rail head.



This caboose is higher than prototypical. At 1/29 scale (when scaled up) this would be about 12 ft, 2 & 1/2 inches compared to the prototype of 11 ft, 9 & 7/16 inch - shown in the example drawing below. This is about 5 inches too tall (or about 0.170 inch when scaled down to 1/29).



None-the-less, the caboose looks very appropriate coupled with the Raised up GP 38 loco (by 0.094 inch), much less (at 3 foot distance) than the so called "10 foot rule" would suggest.


Alternative Method Variation - with Inverted Coupler Box Orientation:


The drawing that follows is an example of how the ATSF Extended Vision caboose was done. This particular example was more involved because it included LGB wheels of larger tread diameter that raised the caboose up by 0.050 inch. Consequently, this caboose was lowered 0.125 inch, not only to correct for this, but to better optimize the mounting of the coupler box and better resemble (though not exact) a prototype car height. As a result, this example caboose is lower to the railhead when compared to the Rock Island Bay Window caboose previously described.

Note: The thickness of the metal plate in the following drawing is 0.035 inch:


Note: Although the dimensions shown in the above drawing are optimized for the caboose with larger LGB wheels, the tail screw does afford coupler leveling adjustment (within reason) for other car heights from the railhead.


The following pictures serve to illustrated installation of the coupler subassembly and other detail items done to this caboose:


When done, the Kadee 907 centeset coupler is to align with the Kadee 980 gauge for proper coupler height to rail head distance.



The height of the Extended Vision caboose with larger diameter LGB wheels (but modified with "lowered truck") measured about 5.0 inches even from the catwalk to rail head.



Though this caboose was lowered, it is still higher from the rail head than prototypical when scaled up from 1/29 scale.


Installation Comments:


Both USAT Bay Window and Extended Vision Caboose types use Bettendorf freight trucks; however, for the caboose examples described here the bolster part differs in that it's made of soft plastic has no ribbing on the surface that pivots against the car bolster and has a notably longer tang. If it is desired to retain the original truck without cutting off the tang, the USAT Bettendorf truck, part no. 2033, can be used. The entirety of this truck appears to be made of nylon, including its bolster.


Lowering a caboose is done by modifying the truck by lowering the bolster with respect to the side frames using the same technique described for the "Aristo Covered hopper, Lowering ...", albeit with different values removed.


Note: Truck bolsters on USAT cabooses may be made from Nylon material, not just soft plastic. It's unknown why the factory made the bolsters with different materials. Nylon is preferred for its durability.

In the example ATSF Extended Vision caboose, the trucks were "lowered" by 0.125 inch that took into account the ribbing on the substitute Bettendorf P/N 2033 all nylon trucks that were used in place of the factory ones that came with that caboose.


The illustration that follows describes installation detail with respect to coupler assembly and if using a "lowered" truck to lower the caboose. Though the illustration is of an example ATSF Extended Vision caboose, the same considerations apply to the Bay Window caboose type.


A close up view of the truck with retaining means for the electrical pickup wires is shown below.


Note that care must be taken to make sure the mounted coupler assembly is straight as shown below.  This is one of the most significant things in the whole project to watch out for and get correct whilst at the same time maintaining the proper height per the drawing, but it's doable with patients and care.




Appendix A, Disassembling the Caboose

The repair of an example damaged USA Trains bay widow caboose will be described that necessitated disassembly.

Disassembly includes separating the underframe and roof from the car body.

To repair the damage done to this particularly caboose, only the under frame needed to be removed.
Removing the roof to access the battery compartment is shown in Appendix B.

The example USAT used bay window caboose shown below had a broken away truck - tethered by wires!

Underframe Removal:

There are 8 total screws that retain the underframe to the car body, including those hidden under the trucks.

To access the hidden screws under the trucks, the trucks can be removed and set along side whilst still tethered by their power pickup wires. Normally, there is no need to unsolder or remove the power pickup apparatus from the trucks - unless other issues are to be addressed, which was done in this example caboose.

After the underfame screws are removed, both end panels can be gently pried loose in order to pull away the underframe (with tethered trucks) from the car body. (End panels will remain captive to the roof with ladders & poles - so be careful not to dislodge them)

The underframe removal is illustrated below:

Note the clever design is such that there are no wires between the underfame and car body.


Power Pickup & Wire Routing Considerations:

If there is a need to remove the truck power pickup apparatus, the following illustration may be helpful:


Bolster Repair:

The truck mounting post was sheared off from the bolster leaving minimal material in which to thread a screw. So a plug is fabricated to be placed within the hollow side of the underfame bolster area.

The illustration below includes dimensions.

Note: If it is desired to obtain a ready made 3-D printed repair plug, contact Colin at This email address is being protected from spambots. You need JavaScript enabled to view it.


Repair plug installation is Illustrated below:


Replacement Mounting Screw & Bushing:

A longer screw is needed to thread into the plug when refastening the truck. Also, if the sheared off truck mounting post is damaged or missing, a replacement bushing will be needed.

Two screw choices are to be described.

One choice is to use a longer #2-56 screw, illustrated below


The better choice is to use the Metric M2.5 longer screw, illustrated below:
(The M2.5 screw body is similar in diameter to the original factory screw, therefore, does not need shrink tube to makeup for the difference in space.)


After the repair plug is installed, the underframe can be reinstalled on the car body in the reverse order in which it was removed. (Ensure car end metal poles & ladders are properly seated within roof holes - otherwise the end platforms will be pushed down and not be level)

In this example a bushing was substituted for the post that was sheared-off.

Truck Re-installation:

Note: In the following illustration, the drill and tapping for the selected screw can be done before or after the underfame is installed on the car body.

Body Mounting Kadee 907 Coupler Boxes:

With repairs completed and underframe reinstalled, the "gullwing" plate was used like dimensioned and previously described for the extended vision caboose having projected coupler boxes. In this example, there is sufficient trail screw adjustment to level the couplers for alignment with the Kadee 980 gauge.

Note the top lid, also, serves to keep the end panel against the underframe platform - so no glue is needed (preferably not used) to fasten the end panel to platform.



With the caboose now repaired, its weight is shown below:



Appendix B, Battery Access & Possibilities

To access the battery compartment within the caboose, the roof can be removed as illustrated below:
(Note: For method to be shown, the underframe is to be removed first - previously described in Appendix A)

With the roof removed, the battery can be installed or replaced; however, consideration can now be given for providing a means to externally directly measure the state of an installed battery OR for mounting the battery externally.


An Experiment using a Lithium-ion battery:

USA Trains specifies a Ni-Cad 9 volt type battery for the caboose that the user supply and install for keeping the rear light flashing when track voltage drops below a predetermined value (approx. 14 vdc from my measurement).

My experience with Ni-Cads in power drills is they tend to self discharge when not used in awhile - like a few short weeks. Since the caboose must be taken apart to install the battery, and the battery must be pre-charged before installing it, this can be a disincentive for using it should it discharge.

Compared to Ni-Cads, Li-ion type batteries characteristically don't self discharge nearly as much over time. The Li-ion 9 volt battery is also higher in energy capacity than the Ni-Cad. Accordingly, a test was perform using a Lithium-ion 9 volt 600 ma hour battery externally connected to the caboose.

Like the factory intended Ni-Cad battery, the Li-ion battery is to be pre-charged, too.

The circuit design within the caboose is intended to maintain a keep alive charge on the 9 volt Ni-Cad type battery and presumed to be specific to it. So for sake of experiment, the Li-ion battery is diode isolated so internal circuitry does not come into play, particularly when the caboose is track powered. That said, the experiment was done without employing track power but still diode isolated.

Results of the experiment are illustrated below:

It is not good practice to directly install the Li-ion battery type in the caboose given its high energy capacity without analyzing the internal circuitry for determining possible changes to it. Accordingly, if using the Li-ion battery type, it can be isolated from the caboose charging circuitry with a diode as done in this experiment.


Compared to the factory Ni-Cad battery, the Li-ion battery has notably more energy capacity and does not self discharge nearly to the extent of the Ni-Cad battery over a long time period.

Given the experiment, if one were to operate the caboose with flashing rear light on a layout with a track voltage less than about 14 vdc (when the battery would supply power to the light) for a 2 hour session, the battery charge (when discharged from 8.4 to 7.4 vdc) could last for 84 sessions before needing a recharge. With the battery connected externally, If you ran your train that way for 84 consecutive days (almost 3 months!), it would not be inconvenient to remove it, and put it in a dedicated charger for the next extended run.

To further take advantage of the 9 volt Li-ion battery higher energy capacity (9 volt batteries also available greater than 600 ma hour duration used in test) there is the possibility to change / modify the incandescent lighting circuitry, including substituting LED lamps, so the battery can provide sole power to the caboose without relying on track power at all. An externally accessible battery is particularly advantageous in this application.





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