USAT Modern tank & Kadees

USA Trains Modern Tank Cars & Body Mount Kadee Couplers

USA Trains Modern Tank Cars & Body Mount Kadee Couplers
Ted Doskaris
December 3, 2016
Revision GE-A

July 2, 2019, amended July 3, 2019
Revision GE-B Added body mount choice Method 4, a 3-D printed coupler box & added reference to Eric Reuter's 3-D print Adapter

Contents:

Preface
USA Trains & Kadee Couplers
Adapter Plate Spacer
Kadee Body Mount Choices
Coupler Height Dilemma

Coupler Mounting Methods

Method 1 Spacer Washer
Method 2 Thin Lid
Method 3 Small Box Footprint
Fabricated Spacer Dimensions
Method 4 3-D Print Small Foot Print Box
Obtaining 3-D Printed Coupler Box

Trucks & Wheels
Car Weight with Kadees
Operational Examples
Video

Preface

This article describes example choices and methods for body mounting Kadee centerset type couplers on the USA Trains 1/29 "G" scale "modern tank cars" for operation down to 8 foot diameter track curves. Generally, anything less than 8 foot diameter curves is probably inappropriate for body mount couplers. Also, layouts should have a straight track section about the length of a longest car between "S" bend transitions to minimize the possibility of pulling cars off the track.

The USA Trains modern tank cars have been available for some time and are made in 3 size lengths. The cars are excellent albeit relatively heavy being made of extruded aluminum.

The first thing noticeable about the cars is the nicely done platform with openable hatch covers over the detailed valves. However, the cover that is retained by the chained pin can be a nuisance when handling the car since the pin is apt to fall out causing the cover to flop open when least desired.

The cars are factory equipped with metal trucks having metal knuckle couplers mounted on them; however, the car chassis does include pads for body mounting couplers. Accordingly, the trucks and their factory couplers are to be removed in preparation for body mounting couplers.

USA Trains & Kadee Couplers

USA Trains does offer body mount coupler assemblies at extra cost that are stated to mate with Kadees. These resemble the Kadee 906 but use a proprietary uncoupling mechanism when compared to the Kadee trip pin that resembles a hose.

The factory truck mount couplers exhibit the typical USA Trains way low to the rail head attitude. Perhaps this height was chosen for low center of gravity that may have been considered beneficial for pulling trains having truck couplers, albeit incompatible with most other brand products. That said, USA Trains offers their own body mount couplers as previously described.

Adapter Plate Spacer

The USA Trains adapter plate spacer for body mounting the USAT extra cost couplers can also be used for Kadees. Interestingly, the spacer can be mounting in different ways - examples shown below.

Adapter Replacement

If needing a replacement, Eric Reuter has developed a 3-D print replica "USA Trains Modern Tank Car Kadee 906 Adapter".

If choosing to have the adapter slightly reduced in thickness by 0.030 inch so a mounted Kadee 906 coupler will better align with the Kadee gauge, Eric indicates he could accommodate that change as commented on the LSC Technical modeling forum, "USAT Modern Tank Car - Kadee Adapter".

Kadee Body Mount Choices

Example Kadee coupler choices for body mounting not only include the Kadee 906 with its wide box, but also the smaller foot print Kadee 907 narrow box type normally meant for truck mounting. The narrow box choice is particularly good for installation on the USAT 55 foot car so its wheels won't bind up when operated on tight curves down to 8 foot diameter. In this regard, inline mounting the box becomes a necessity for operation on tight curves for the 55 foot and 42 foot cars.

Inline mounting a Kadee 906 box requires an additional piece of material and hole for screw threading as illustrated above and below. Note the piece shown below is the minimal size needed; it can extend all the way to the opposite side as previously shown in the white spacer if so desired but should not be so thick as to protrude above the surrounding walls.

Coupler Height Dilemma

When body mounting Kadees with the USA Trains adapter plate spacer, the coupler height is too low to the railhead

Coupler Mounting Methods

There are three example methods to remedy the coupler height problem:
(1) Use the Kadee 906 & raise car by using a washer between the truck and car body (easiest to do)
(2) Replace lid on the Kadee 906 box with thinner one & file down the box lugs flush with thinner lid
(3) Use the Kadee 907 in concert with a fabricated thinner adapter plate spacer. This method requires precision workmanship. (Note: Must use this method for 55 foot car operation down to 8 foot diameter curve track)

(4) Use a 3-D printed direct fit coupler box (now available) that accepts parts from a Kadee 907 kit. This method has the same attributes described in method 3 but without the need for fabricating precision parts.

Each of these methods will be described. All methods can be used on all 3 car lengths with noted limitations.

Method 1, Spacer Washer
Mount Kadee 906 with wheel pockets filed in the sides of the box along with raising the car with a 0.032 inch thick washer is OK if you don't mind the look of the car that already appears high from the track. (Note: This method limits 55 foot car operation down to 10 foot diameter track)

Note: The spacer should be rotated 180 degrees from what USA Trains intended because the wheel flanges interfere with the "ears" when the car is operated on tight curves (8 - 10 foot diameter).

Shown below is the coupler alignment with the Kadee 980 gauge when using the washer to raise the car.

Method 2, Thin Lid
Mount Kadee 906 with wheel pockets filed in the sides of the box but replace the Kadee 0.070 inch thick box lid with a thinner 0.040 inch thick one. The plastic material for the replacement lid can be obtained from TAP plastics. They can cut a 1 inch wide strip of ABS plastic at low cost. The material typically is textured on one side and a smooth on the other side that can be used to aesthetic advantage. The strip can be cut to into pieces for making several lids.

Shown below is a 42 foot car with thin lid.

Shown below is a 29 foot car with thin lid.

Method 3, Small Box Footprint
Mount a Kadee 907 type box that has a small foot print on a fabricated thinner adapter plate spacer. Compared to using a Kadee 906, this method allows the 55 foot car to operate down to 8 foot diameter track.

The illustration below demonstrates the desire for using the small foot print Kadee 907 narrow box in place of the Kadee 906 wide box assembly.

Fabricated Spacer Dimensions
ABS plastic material 0.170 inch thick can be obtained from TAP Plastics cut in a 1 inch wide strip. The material typically is textured on one side and a smooth on the other side. The strip can be cut to into pieces for fabricating several spacers used for mounting a Kadee 907 narrow box coupler assembly.

The measurement of bosses on the chassis coupler mounting pad are used to establish the location of the holes in the spacer. A 9/64 inch drill is used for the 4 holes.

Note: This method requires precision workmanship but can be mitigated if a template is used.
By using a precisely made template, "slave" spacers can be made with virtually the same precision.

Using Template

Using a template, "slave" spacers can be made as illustrated below.

Mounting the Kadee 907 fabricated spacer

To mount the spacer, screws different than those provided by USA Trains along with washers are needed as described in the following illustration. They can be obtained from Grainger.

Alternatively, though not as good, screws with integral washer heads can be salvaged from 332 size track as illustrated below.

Fastening the fabricated spacer is described in the illustration below.

Method 4, 3-D Print Small Foot Print Box
Taking advantage of current technology, using a direct fit (no spacer) 3-D printed coupler box can save much time when compared to fabricating precise parts to mount a small foot print Kadee box. Like method 3, the 3-D printed box also allows the 55 foot car to operate down to 8 foot diameter track.

Optional 3-D Printed Coupler Box

Available is a 3-D printed "CamPac BoxTM" that elevates all the effort to make discrete parts to body mount Kadee centerset couplers on the USA Trains modern tank cars.
Illustrated below are example cars equipped with the 3-D printed direct fit (no spacers needed) small foot print boxes fitted with Kadee centerset couplers.

The 3-D printed CamPac BoxTM is optimized to use parts from the 907 kit, including the late version Kadee coupler. Illustrated below are 3 example versions of couplers so that the proper one can be identified for use in the CamPac BoxTM" Early versions are not intended for use as their coupler shanks would need to be drilled out in order to fit and perform properly.
Illustrated below are 3 example versions of the Kadee "G" scale centerset coupler.

The late version coupler from the Kadee 907 kit is to be installed in the CamPac BoxTM as illustrated below. (Of course, 2 boxes are to have preinstalled parts for each car.)

With the coupler parts preinstalled in a CamPac BoxTM, refer to the illustration below for its installation on the USAT modern tank car.
Note: Should screws to mount the box be unavailable, substitutes can be supplied when obtaining (ordering) the CamPac BoxTM.

Illustrated below is an example car with coupler alignment with the Kadee coupler height gauge.

Often, the installed preassembled box coupler will align with the Kadee coupler height gauge, however, should the need arise, shims can be utilized as illustrated below.

Obtaining 3-D Printed Coupler Box

The 3-D printed "CamPac" coupler box is designed by me (Ted Doskaris) in concert with Colin Camarillo who has the software expertise and 3-D printer to implement them.
If desiring to obtain these boxes (1 pair supplied per car) for this application (other applications available, too), contact Colin Camarillo via his website , and specify the box application with quantities (e.g. USAT Modern Tank Car) to be ordered.

Trucks & Wheels
The USA Trains trucks typically have wheel back to back spacing on the low side of NMRA specs.
In this case, re-gauging the wheels toward the higher end of specification will improve, albeit small, wheel clearance from the coupler box for operation on tight track curves. This is particularly useful when using the Kadee 906 wide box (previously described Methods 1 & 2).

A description of what's entailed for gauging the wheels is provided in the below illustration.

Operational Examples

An example 55 foot car with body mount Kadee 907 narrow box is shown below.

The 55 foot car having a very long wheel base has the most truck swing on curves, therefore, the least wheel clearance from the coupler box on tight curves but still operates OK on 8 foot diameter curves.

An example 42 foot car with body mount Kadee 906 wide box is shown below.

An example 29 foot car with body mount Kadee 906 wide box is shown below.

The 29 foot car having a very short wheel base has the least truck swing on curves, therefore, the most wheel clearance from the coupler box on tight curves; consequently, this car will likely operate OK on some curves less than 8 foot diameter.

Car Weight with Kadees

These cars being made from extruded aluminum are notably heavy compared to typical plastic cars. This is of benefit in train operation on tight curve tracks because the cars won't readily "string line" (pull off the tracks) when in a long train. However, the tradeoff is when heavy cars are in a train that must ascend grades. In this case multiple locos may be needed for longer trains.

The 3 tank cars of different lengths vary about 1/2 pound from largest to medium to smallest.