Aristo Covered Hopper, Lowering & Kadee Installation

Aristo Covered hopper, Lowering & Kadee Coupler Installation
Ted Doskaris
October 31, 2009 Initial Release as Rev. GE-B

October 3, 2010 Rev. GE-C - Added material, including Appendix A & B

October 26, 2021 Rev. GE-D - MAJOR Updates include added table of contents, info. about newer Kadee coupler boxes and added Appendix C for optional Nico Corbo's 3-D print replacement lowering bolsters, including option of 3-D print CamPac coupler boxes used with "roller bearing" trucks.



Lowering Car Using Modified USAT Hot Box Trucks:
Aligning Car Floor with End Sill
Test Cars
Installation Considerations & Tips
Dimensional Drawings
Specific details - Lowering USAT Hot Box Truck
Reassemble Modified Trucks
Car Coupler Alignment Results
Weight of Completed Car
Finished Car Comparison
Car Operation on 10 foot Diameter Track

Car Operation on 8 foot Diameter Track
Appendix A - Installation Techniques
Appendix B - Lowered Truck with Tang Couplers

Lowering Car Using Nico Corbo's 3-D Print Bolsters (Appendix C):
Installation of Lowering Bolsters & Chassis
Installation of Kadee 906
Installation of USAT Intermodal Trucks & CamPac BoxesTM




This vignette (article) will include a methods for how an Aristo-Craft covered hopper car can be lowered, including when equipped with body mounted Kadee model 830 or smaller "foot print" 789 centerset (straight shank) type coupler assemblies without modifying the car itself. The same methods would apply to newer, successor Kadee respective models 906 and 907.

The method for lowering the car that requires cutting off the factory bolsters from the chassis and replacing them with lowering bolsters designed & offered by Nico Corbo will be described in Appendix C, including using Aristo factory equipped Bettendorf "hot box" trucks or replacement USA Trains plastic "roller bearing" trucks.

The Kadee 830/906 box is relatively large and includes a single longitudinal spring loaded coupler within it whilst the 789/907 box is smaller and includes a dual spring loaded coupler having a lateral affect. Both types have self centering coupler characteristics.

Lowering the car & Aligning its floor

For installing body mount couplers on the Aristo Covered Hopper car, the most significant items that must be addressed are to lowering the car and align its floor.

As with many Aristo rolling stock products, this car sits too high from the rail head.
In order to lower the car, some folks have done surgical modifications of the car in order to lower it - namely, cutting out the car's bolsters and replacing them with modified or newly fabricated ones of a lesser height. Since the advent of 3-D printing, this becomes a viable choice.

Illustrated below are two possibilities using Nico Corbo's ("This email address is being protected from spambots. You need JavaScript enabled to view it.") replacement lowering bolsters with an example Canadian (aka, Canadien) National car.

Note: Because lowering the car more so by using USA Trains Intermodal trucks, a Kadee 906 coupler will be too close the railhead and snag on track work and not align with the Kadee coupler height gauge. That's why the special CamPac coupler box was designed with small foot print taking advantage of integrating it with the car's end sill vestigial draftgear.
Click on PICTURE that graphically previews what's to be done when pairing CamPac BoxesTM with the lowering bolsters. ("How to" details are presented in Appendix C.)

Lowering bolsters are designed by Nico Corbo. They are available by This email address is being protected from spambots. You need JavaScript enabled to view it..

CamPac Boxes are designed by me (Ted Doskaris) and implemented by Colin Camarillo. They are special order available from Colin by contacting him via his website.

ADVISORY: CamPac boxes are optional when choosing USA Trains Intermodal trucks being specifically designed for use with Nico Corbo's lower bolster version as of September 2, 2021. If changes are made from this version, the CamPac box may not fit, so it's best to first check with Nico.

If interested in utilizing lowering bolsters with or without CamPac boxes, see full detail description at Appendix C.

However, if desiring to keep the car intact as it comes from the Aristo factory, the original Aristo Bettendorf type truck assemblies can be replaced with USAT brand Bettendorf "Hot Box" trucks (USAT part no. 2033) - albeit modified as later illustrated in drawings.




Lowering Car Using Modified USAT Hot Box Trucks

Using USA Trains Bettendorf trucks (to replace Aristo trucks) are fairly inexpensive to purchase from USAT via Charles Ro Supply Company as they don't come with wheels. If lacking metal wheels, RLD Hobbies packages them in 4 axles to a bag for a reasonable price as shown below.

I modified these trucks by lowering their bolsters 0.220 inch - this value being about the practical maximum limit so as to retain their rigidity and pivot without interference when mounted on the car.

The unmodified USAT Bettendorf truck is shown at the left with the modified one at the right. The below picture shows the under side view. Note the coupler tang must be removed  to clear the axle.

The USAT trucks lend themselves well to the modification whilst preserving their rigidity - something impractical and virtually impossible to do with the original Aristo trucks.
Shown below is the overall resultant 0.300 inch distance from the top of the side frame and  bolster.

When these trucks are mounted on the covered hopper car, there is some minimal, non objectionable, lateral rocking allowed. This affords a desirable amount of articulation with car operation on less than perfect track work since USAT trucks do not include actual working springs as found in the originally installed Aristo trucks.



Aligning Car Floor with End Sill

The Aristo covered hopper car as new out of the box typically must have its floor popped into its intended position at the open end areas of the car. But once doing that, the floor's end area will typically not line up flush with the car's end sill as there is no mechanical connection by design.
Shown below is how the floor typically bulges downward below the car's end sill.

With the car supplied and operated with truck mount couplers this would not be an issue, but when using body mount couplers the floor must be aligned with a consistent attitude, ideally by having its underside surface being made flush with the end sill.

In order to align and secure the floor to the end sill, I made use of a small metal clip modified from what was originally intended as a terminal for an electrical crimp, but the clip can be newly fabricated as will be shown later in a drawing. The metal clip fastens to the floor and extends over the lip of the end sill.

Adapting some common item to use for the floor retaining clip like those shown installed in the cars of these pictures helps so you don't have to fabricate the entire clip from scratch.

I happen to have a box of terminals intended for mating with push-on electrical crimp type connectors. I was able to alter these terminals by using small needle nose pliers and other tools to make the required bends in the same locations like that of a completely fabricated clip as will be illustrated in a drawing. For the clip's fingers, I cut the end off near the outer edge of hole.
Shown in the foreground of the picture below are a couple of altered retaining clips, and in the background are a few terminals as they came out of the box.
Notice the dimple that is almost in the exact place where the hole is to be drilled and tapped for its no. 2-56 screw thread.

With the car lowered and the floor aligned, a spacer shim of about a tenth of an inch is also required to be placed between the Kadee coupler box and the underside of the car.
This spacer is virtually the same for both models of Kadee boxes. Its dimensions will be shown later in a drawing.
Shown below is the black plastic spacer resting on a Kadee 930 rust colored coupler box assembly ready to be mounted on a Union Pacific test car. Note that spacers and shim thickness values may somewhat vary from car to car depending on tolerances, including truck modification consistency. (The truck modifications will be discussed later and shown in a drawing.)

By design, the Aristo covered hopper car floor surface where the coupler box mounts is not completely level across its entirety. Use of the Kadee 880 gauge (980 gauge for newer coupler) is of great value for checking the coupler alignment during the shimming and leveling process.
To level the Kadee 830 coupler assembly in the example Wabash car shown below, a thin washer of 0.032 inch thick is placed under the rear extremity of the box. Again, this value may vary somewhat. 

Similarly, to level the Kadee 789 coupler assembly as shown below, a rectangular shim of 0.010 inch thick (provided in the Kadee 789 kit) was slid under the tail end of the 789 box before the box was fastened down with a rear screw. (The same would apply when using the newer Kadee 907.)


Test Cars

1) Wabash car

My first example car to try the Kadee installation on is the Aristo Wabash covered hopper.

Shown below is how dramatic this example car appears with an original Aristo truck left in place at the left and the modified USAT truck installed at the right.

Shown below is an underside view of the car having modified USAT trucks on both ends with an installed Kadee 830 box at the left and Kadee 789 box at the right . Note how the truck is allowed to pivot a bit more before its wheels touch the smaller 789 box. This may be of benefit for operation on curves tighter than 8 foot diameter - which is what these cars easily work on with the 830 or newer 906 type boxes.

2) Union Pacific car

I decided to do a second car to check for consistency. In this case I installed the model Kadee 930 at both ends of the car.

The Kadee 930 assembly is the same as the Kadee 830 but made in a rust color, thereby better matching cars painted with brown or "box car red" colors. (The newer rust colored coupler is the Kadee 906R.)
Since these model Kadees have relatively large boxes, I believe color matching cars exhibiting open end type structures tends to lessen the more noticeable visual impact of the larger size box. In this regard, a more prototypical look would favor using the smaller model Kadee 789 or newer 907 box.


Installation Considerations & Tips

1) Coupler box Mounting screws

Only two screws are used to mount either the Kadee 830 or 789 coupler and newer boxes utilizing the in-line holes of the boxes, and the screws are 0.75 inch long no. 2-56 as supplied by Kadee with the 830 boxes. (The newer Kadee boxes no longer supply no. 2-56 screws and nuts, instead having bulky no. 4 self threading screws.)

If using the 789 or 907 box, you must drill a hole centered through this box nub recess area for its forward mounting screw to pass through it. As shown the example below, a washer placed within the nub recess can be used to help center the drill.

The forward mounting screw for each box also serves as the fastening screw for the floor retaining clip. The rear screw's length must be trimmed so it does not protrude much past the floor for the end of the car having the brake assembly - otherwise it will interfere with it, whereas, the forward screw need not be trimmed as there is a hollow recess in the assembly that envelopes the longer screw. For the end of the car devoid of the brake assembly, the screws' lengths can be trimmed for best aesthetics.
The brake assembly of the car is held in place by 3 small self threading screws from the underside of the car. Two screws retain the brake valve and air tank.

The forward most screw head at the brake valve will interfere with the shim used under the coupler box on this end of the car so the shim is to be notched as shown in the drawing to follow. Alternatively, this screw could be removed (left out); however, when installing the forward coupler box screw, you need to press your finger on the forward end of the brake assembly so the screw won't push up on it. Since this portion of the brake assembly is offset from the center line of the car, the screw will have a desired effect of digging into one side of it within its hollowed area, thereby helping to retain it.

2) Shims

The shim material I used for the coupler box spacer included a plastic strip purchased in bulk at an inexpensive price from Tap Plastics. For example, I had them cut a 3/32 inch thick, 3 foot long by one inch wide black colored strip. I sliced off what was needed with a razor saw to the dimensions of that shown in the drawing to follow. I chose the 1 inch dimension since this best fits within the flat portion of the floor pad area when placed lengthwise.

3) Threading floor holes

The purpose of using a tap to make threads in the car floor and metal floor retaining clip is to save one the difficulty of trying to place small 2-56 nuts within the interior confines of the car - particularly on the end having the brake assembly so it would not have to be unfastened; but if you wish, you can body drill for the 2-56 size holes and use the nuts that are supplied by Kadee. Alternatively, self threading screws could be used or used in combination with previously described methods. That said, when using the newer Kadee box, it's desirable to obtain no. 2-56 screws.
Consequently, for the example test cars, I did not have to remove the brake assembly.

4) Floor retaining clip alternative - only when using Kadee 789 box

As an alternative to the metal floor retaining clip (applicable only when using the model Kadee 789 or 907 coupler assembly) the hole that is provided to secure the box lid with small screw could be somewhat enlarged to accept a long screw to pass through the box such that it could thread into the car's end sill lip - thereby serving to fasten the coupler box lid whilst at the same time securing the floor flush with the end sill of the car. However, the upper side of the lip (as shown below with clip) will be at risk of becoming aesthetically compromised if the screw were to break through its center rib.

If you are willing to do so, you could trim off the center rib and take advantage of a center flat area of the lip to install the screw from the top down - passing through the 789 or 907 box to secure it.



Dimensional Drawings

The following includes drawings that illustrate where to drill holes in the car floor for mounting either Kadee 830/906 or Kadee 789/907 type coupler boxes, the required floor retaining clip, and the modifications required of the USAT Bettendorf trucks:

Kadee 830/906 or 789/907 coupler box mounting Locations, etc. - Specific details

The Kadee 830 & 906 type box uses hole locations 1 &  3 as shown in the drawing.

As shown below, the car's floor holes for mounting the coupler box can be located and marked with a scratchall tool by pricking the soft plastic. The resultant dimple will facilitate drilling the holes.

I use a pin vise to drill out the floor holes to the desired size as indicated in the drawing.
Typically, I start with a small pilot drill, then progress to the finished drill size.

A pin vise with the finished drill size is shown below. Also, note the notch at the tail end of the black shim on the coupler box is to clear the floor screw that retains forward section of the car's brake assembly.

The holes are then tapped for the no. 2-56 screws as shown below.

As shown below, the example Kadee 789 box has a different rear screw location than the 830 & 906 type box. Either box type only requires two screws, but the rear screw is located differently.
The Kadee 789 & 907 box uses hole locations 1 & 2 as shown in the drawing. 


Specific details - Lowering USAT Hot Box Truck

The new in the bag USAT Bettendorf truck assembly must first be disassembled by removing the screw that secures each side frame to the truck bolster ends, after which the side frames can be withdrawn. The side frames are made with pockets that accept the truck bolster ends.

As can be seen in the above drawing, lowering the USAT Bettendorf truck requires 4 modifications that involves: (1) removing 0.220 inch from the height of the side frames' pocket, (2) removing the same value 0.220 inch from ends of the truck bolster sides, (3) notching out a small section of the rib on the underside of the truck bolster, and (4) removing the bolster's coupler tang.
The following detail description is expressed mostly in terms what material is to remain on the side frames and truck bolster rather than what is to be cut off:

1) Cutting down the USAT Bettendorf truck side fame pockets

The USAT truck appears to made of a nylon type material - it being somewhat though to cut, but using a fine tooth razor saw works well.

Shown below, the razor saw is used to make the lateral depth cut of the side frame's pocket.
The scale is helpful to initially locate the saw. Though in the example depicted here the scale appears to be at about 0.200 inch, move the scale as needed to make sure the desired amount of the pocket that is to remain is to be 0.235 inch as per the drawing.  

Shown below is how the saw has penetrated through the pocket wall of the side frame.

Shown below, the razor saw is being used to make the slice parallel with the side frame - stopping when reaching to the desired depth.

Shown below is the USAT Bettendorf truck side fame with completed cuts made to its pocket.
Note, If mistakenly taking off too much material, you can use small piece/s of duct tape acting like shims to build back up the pocket height. If taking off too little, you can file down the pocket to the desired height.

Any cleanup of the side frame pocket cuts is done with a file as shown below.

When done, the desired result is to have the side frame pocket height measuring 0.235 inch. As shown below it's a bit short by 0.010 inch - correctable by using a small piece of duct tape placed on the lip of the pocket to build it back up.

Shown below is how the cut down pocket of the side frame on the left compares with the original on the right.

2) Cutting down the USAT Bettendorf truck bolster sides

Shown below is one of the sides of the truck bolster. Both sides are to be cut so that 0.335 inch remains. (As depicted in the upper part of the picture, the distance from the upper side of razor saw to the top of the bolster.)

When done, the desired result is to have the height of the sides of the truck bolster measuring 0.335 inch as shown below.


In the event either the side frame pocket or bolster side were cut a bit too short, it is to be appreciated that the longer of the two will dictate the overall assembled result of the truck. For example, if the side frame pocket were to be less than its targeted 0.235 inch height but the bolster side height is at its targeted 0.335 height, the assembled truck will be OK. Likewise, if the bolster side height were to be less than its targeted 0.335 inch height but the side frame is at its targeted 0.235 inch height, the assembled truck will be OK.
This, of course, may not work out if either of them were grossly wrong. 

3) Notching the underside of the truck bolster

Notching is required so that the bolster sides are allowed to seat all the way into the side frame pockets when the truck is reassembled.

A small rib section next to the side of the truck bolster must be cleanly removed down to base surface. Using a razor saw to do this is shown below to make the initial cut at a distance of 0.070 inch, minimum.

You can use a small needle nose pliers to bust off the small piece after the cut is made and clean up with an X-acto knife and small file held on its side as it passes through the cut out area of the rib.

4) Remove the coupler tang from the truck bolster

Due to the lowering, the axle will interfere with the coupler tang when the truck is reassembled, so the tang must be removed far enough inboard of the axle. The tang could be cut off at the bolster, too.



Reassemble Modified Trucks - with wheels & check results

Install the wheels between the side frames and the bolster into the side frames' pockets.
Use the original screws to secure the side frames into the bolster. A properly modified and reassembled truck will feel rigid and strong just like the unmodified truck when attempting to wiggle the side frames.

Checking the result after reassembly should yield a measured distance of 0.300 inch on both sides of the truck as shown below. If one side is different than the other the car can assume a lopsided stance. If much less than the 0.300 inch value, the car will sit needlessly high requiring more shim distance between coupler boxes and body of the car. If much more than 0.300 inch, the truck won't fully seat over the pivot post of the car body bolster as the side frames with rub against it when the truck pivots. Adding a spacer washer over the truck bolster pivot post may mitigate this.

Accordingly, if not 0.300 inch, corrections must be made. Take the truck apart. First try swapping the side frames at the bolster ends and recheck for the proper 0.300 inch measurement on both sides.
To correct, if more than 0.300 inch is measured, you can use small piece/s of duct tape acting like shims to build back up the side frame pocket height and / or truck bolster side ends. If less than 0.300 inch, you can file down the height of the side frame pocket and / or the bolster side ends to the desired height.


Car Coupler Alignment Results

Shown below is the Aristo Wabash test car with the model Kadee 789 installed as coupled to the Kadee 880 gauge.

Shown below is the Aristo Union Pacific test car with the model Kadee 930 installed as coupled to the Kadee 880 gauge.

As shown in the above pictures, it is to be appreciated how the floor retainer clip's fingers straddle over the car's end sill lip. This serves to align the floor with the end sill whilst keeping the end sill from pushing out due to forces incurred when its retaining screw is tightened down.


Weight of the Completed Car

Shown below is an example Frisco Covered Hopper car with lowered USAT trucks having USAT metal wheels that measures 2.31 lbs.


Finished Car Comparison

Shown below is the end view of an Aristo UP covered hopper car as factory equipped with Aristo trucks but with ART-29111B metal wheels retrofitted. Having no mechanical retention by design, note how much the floor bulges downward by what appears to be its entire thickness!

For comparison, shown below is the like kind car with the modified (lowered) USAT trucks and Kadee 930 body mount coupler installed (Note the dramatic space difference between the side frames and body bolster between the two cars. Ditto for the wheel to floor proximity.)

Though it looks like the side frame of the modified USAT truck is touching the body bolster, the truck pivots OK. Also, note how well the floor is flush with the end sill in the center area where the coupler box is located. The floor retaining clip is responsible for accomplishing this.

Shown below is a side view comparison of two Aristo Union Pacific covered hopper cars. The car on the right has the lowered USAT trucks and body mount Kadee couplers whilst the car on the left is "factory" but for its metal wheels.

Note how the hopper dump areas of the lower car is closer the rail head - it being in line with the lower ends of the truck's journal boxes. When examining pictures in books of prototype covered hopper cars, this appears to be very prototypical.

Shown below is an end view of the UP car with lowered USAT trucks and body mount Kadee 930 couplers installed so the car's overall height can be appreciated.

Shown below are GP40s & SD45 pulling a 45 car test train with the Aristo Wabash and UP covered hopper test cars.



Car Operation on 10 foot Diameter Track

The USAT SD70 is one of the worst case locos that can be used for testing operation of a car on curve tracks with respect to coupler action and any possible tendency to force a car off the tracks. This is because of the long wheel base of the loco along with its unfavorable as designed truck pivot location - the two of which combine to project this loco's front pilot (and coupler) to an extreme outer position on curves. 
My USAT SD70, when the below picture was taken, had been custom fit with body mount swinging Kadee 787 medium offset coupler box assemblies. (The swinging box helps mitigate the ill effects of the SD70 design.)

Shown below is an overhead view of the SD70 coupled to the Wabash covered hopper test car with the Kadee 789 body mount assembly on a 10 foot diameter track curve.

Shown below is an overhead view of the SD70  coupled to the other end of the Wabash test car with the Kadee 830 body mount assembly on a 10 foot diameter track curve.

Both coupler box types performed well with the SD70s pulling a 45 car train.
However, the vertical displacement of the SD70 coupler on the curve section of the track was better when coupled to car having the Kadee 830 assembly.
Since the SD70 has medium offset Kadee 787 couplers, there is a natural tendency for them to tilt downward when loaded with a heavy train. So such characteristics are not unexpected.

In this regard, when I did the same test with Aristo GP40s or SD45, there was virtually no vertical coupler displacement. The GP40s and SD45 I used are equipped with custom fit body mount Kadee 789 center set couplers.
Shown below is an overhead view of a GP40 coupled to the Wabash test car with its body mount Kadee 789 in a 45 car train on a 10 foot diameter curve track.

Shown below is an overhead view of a GP40 coupled to the UP test car with its body mount Kadee 930 in a 45 car train on a 10 foot diameter curve track.


Car Operation on 8 foot Diameter Track

I also tried testing the car on 8 foot diameter curve track. My layout is mostly 10 foot minimum diameter worst case for its main line, but rail yard access uses 8 foot diameter track - so I could not test a long heavy train load on this area of the layout.
That said, the Aristo Wabash test car with Kadee 830 on one end had no problem when the car was artificially loaded with my hand at one end with the SD70s coupled to the car at the other end.
Shown below is an overhead view of my SD70 having modified swinging Kadee 787 box with its offset coupler coupled to the Wabash test car with Kadee 830 on an 8 foot diameter curve. (This was done before being upgraded years later with aesthetically pleasing and functionally better CamPac 3-D printed swinging boxes fitted with Kadee centerset newer couplers from the 907 kit)

However, when I turned the car around and coupled the end having the Kadee 789 box to the SD70, the car - when artificially loaded - would tend to left its front truck inside wheels from the rail head.
Shown below is an overhead view of my SD70 having modified swinging Kadee 787 box coupled to the Wabash test car with Kadee 789 on an 8 foot diameter curve.

The below picture shows the side view of the Wabash car with Kadee 789 coupler when coupled to the SD70. The wheels are lifted above the rail head when artificially loaded in this circumstance. This did NOT happen when trying the car with an SD45.

Irrespective of what is a prototypical mismatch, it is not expected to use an SD70 to pull such cars on tight curves as 8 foot diameter, but if done it appears the Kadee 830/906 on the Aristo covered hopper car is the better choice here. The Wabash test car with the Kadee 789 operated OK without incident on the 10 foot diameter curves with the USAT SD70 and long train, and the car was also OK when coupled to either of Aristo's SD45 or GP40 on 8 foot diameter curves - which would be more of a prototypical lash up - given such cars were likely long gone when the SD70 entered service on the real railroads.
That said, the overall results of installing either the Kadee 830 / 930 or 789 example type coupler assemblies in conjunction with lowering the car solely owing to truck modifications and using a floor retaining clip worked beautifully.


Appendix A - Installation Techniques
- Coupler Box & Floor Retaining Clip

The example car used here is the Aristo Rock Island covered hopper - shown with its installed, modified USAT lowered trucks with USAT wheel sets and the newer Kadee 906 couplers. The traditional Kadee 830 / 930 coupler assemblies work the same way. (Notice I took the opportunity to pre-paint both coupler box and floor retaining clip so they would be less noticeable.)

The reason for using a floor retaining clip can be seen as illustrated below.

Note how the floor bulges below the ends of the car. The reason for this is that the car is made with its four floor mounting posts recessed about 0.070 inch too much below the edge of the car whilst the end bulkheads are about flush with that same edge - thus, forcing the floor bolsters and ends upward as illustrated by angle of the rods.

The floor mounting screws could be backed out some to help minimize the effect, or the floor could be removed in order to put spacer washers on the mounting posts; however, doing so will further lower the bunker outlets - maybe too close to the rail head after the lowered USAT trucks are installed.

Another possibility is to trim off the bottom straight edge of the slide-in end bulkheads by about 0.070 inch, but then the floor would have to be allowed to recess further up into the car end areas. This would be a way to lower the car even more than described in this article and would require a less thick and dimensionally different coupler box spacer and retaining clip - a lot more work, and you would likely have to use some touch up paint, too.

As the car comes from the factory, occasionally one or both end bulkheads are not completely seated, and this should be checked before proceeding.

Now for the installation process:

The first thing to do is to loosely mount the coupler box with its spacer using both front and rear mounting screws.
Loosely mounting the box at both its front and rear holes keeps these parts from swinging around at the most inopportune time during the installation process.

A washer should be slid under the rear of the Kadee 830 or 906 type box.
I use a small no. 4 nylon washer. (Depending on cumulative tolerances, the washer thickness required for final leveling the box can vary anywhere from 0.030 inch to 0.060 inch.) At this point in the installation process, just use any thickness within this range.

Whilst aligning the coupler box with its spacer squared up over the floor, thread the rear screw in for a minimal snug fit.

Thread the front screw in so that its end just begins to appear above the plastic surface of the floor.

Now insert the floor retaining clip by angling it so that it will go under the brake valve

Assure the clip is centered once it is under the brake valve. It's OK if the clip assumes a  downward tilt when first inserted as it will tend to straighten out and align during the fastened process.

With the car placed upright and overhanging a bit on a table, hold on to the clip with your finger, then thread in the front screw.  It's OK if the clip lifts a bit off the floor whilst doing this as it will be cinched up later.

The screw is to be started into the floor clip that was previously tapped for a 2-56 thread.
Note: In the event the screw is unwilling to thread into the clip, the tip of the screw can be ground with a conical point for better locating itself into the clip's hole. I only had to grind a conical tip on the screw for 2 of 25 cars completed.

Before grinding the screw's tip, first put a couple of nuts on it so they can be subsequently backed-off for cleaning up the threads.

Once the screw is started into the floor clip the car can be turned on its side for torquing down the screw.

Since the plastic floor had been previously tapped to accept the screw for easing the  installation process, it can now be "stripped-out" as the screw is further tightened down completely. (As the metal clip accepts the force of the screw it will prevail over plastic.)

After all is done the coupler box should be snugged-up against the floor as shown below.  The nylon washer at the rear of the box can been seen, too.

Note the floor does not bulge downward where the coupler box is located.

Shown below is a black Frisco covered hopper car that had to have its coupler box front mounting screw ground with a conical tip to facilitate fastening the clip.

The lowered USAT trucks can now be installed as shown below on the Rock Island car.

With the car placed on a track, check for coupler leveling. I used the Kadee 880 gauge. (The newer gauge is the Kadee 980 that I got sometime later.)  Note the coupler used in the example Rock Island car is the new Kadee 906, but the gauge is equipped with the Kadee 830. With this arrangement I looked to see that the couplers' horizontal casting seams lined up. If the couplers don't line up, check to see if the rear screw has a snug fit and use a different thickness rear washer as required. (Note, since the washer is against the sloped floor area, sometimes you can do leveling by just pushing it toward the end of the car or the center of the car - remembering to re-tightening the screw.)

The completed car is shown below at the brake wheel end with Kadee gauge.

Shown below is a factory Rock Island covered hopper car on the left and the lowered Rock Island car on the right.

Shown below is the factory car. It measures about 5.75 inches above the rail head to the top of the roof walk.

Shown below is the lowered car. It measured about 5.50 inches above the rail head.
So the car was lowered close to a quarter of an inch.

USAT brand metal wheels intended for use in their Bettendorf trucks are about 0.040 inch smaller in tread diameter as compared to Aristo's ART-29111 type metal wheels.

Using the USAT wheels as I did, therefore, contributed to half that amount (0.020 inch) toward lowering the car that when combined with the modifications made to a USAT truck resulted in an overall lowering of about a quarter inch (0.25 inch).  That quarter inch lowering amount may not seem like much, but as can be seen in the pictures it is profoundly better (virtually prototypical) whilst at the same time accommodates the Kadee coupler installation.


Appendix B - Lowered Truck with Tang Mounted Couplers

For using the lowered Aristo Covered Hopper as transition car, its lowered USAT trucks can accept a tang mount Aristo (or Kadee) knuckle coupler - albeit with a weakened tang.

Instead of completely cutting off the tang to clear the front axle as previously described when body mounting couplers, the underside of the tang can be rounded out to clear the axle shaft.

To a minimize the amount of material removed, use of the USAT brand wheels is preferred in this application since its axle shaft is smaller in diameter than Aristo's ART-29111 axle.
As illustrated below, the USAT lowered truck with Aristo ART-29111B wheels (I painted them black) is out of level (slightly taller) than the USAT lowered truck on the right with its USAT metal wheels.

A round rat tail file can be used to remove material from truck tang.


When the truck parts are assembled and the axle is installed, ensure it turns freely when the truck is place on a track and rolled. Otherwise more material must be removed.

For mounting an Aristo Knuckle coupler to the USAT truck tang, I used a coupler assembly salvaged from an Aristo GP40. Note the nub end of the tang must be removed. If a bit too much of the tang's nub is removed, a spacer can be glued at the butt end of the coupler housing - as I did with the green pad as shown below.

I improvised a bushing made from the plastic part of an electrical crimp to fill in the GP40 coupler hole in order to mount it.
Shown below on the left side is the USAT lowered truck with Aristo GP40 knuckle coupler mounted, and shown on the right side is an Aristo Bettendorf truck assembly coupled to it.

For mounting a Kadee 789 or 907 center set coupler assembly - albeit with coupler installed upside down - to the USAT truck tang I fabricated a shim as shown below:

Note the nub end of the tang must be removed. Also, an extra hole was drilled near the tip of the coupler tang.

As shown below, a Kadee supplied shim can be tucked under the coupler assembly for leveling purposes.

As shown below, the lowered USAT truck assembly mounted and shimmed Kadee 789 coupler aligns with the Kadee 880 coupler height gauge.

Shown below is a comparison with the lowered USAT truck at the top with a Kadee 789, at the middle with the Aristo GP40 coupler, and at the bottom is the Aristo truck assembly with its Aristo knuckle coupler.




Appendix C - Lowering Car Using Nico Corbo's 3-D Print Bolsters

Replacement bolsters to lower the Aristo covered hopper car are obtainable by This email address is being protected from spambots. You need JavaScript enabled to view it.. (To accommodate, the chassis is to have its factory bolster ends cut off.)

The lowering bolsters include a pad for body mounting a Kadee box having centerset couplers and are to replace the factory bolsters which are to be cut off from the chassis.

Described will be two possible configurations for the Aristo-Craft covered hopper car which utilize Nico's lowering bolsters - illustrated below.

First, a comparison is to be made of the lowering bolsters and factory bolsters. Both ends of the car are the same except the brake end has more holes for attaching the brake components.

From my measurements, the difference in bolster heights is about 0.170 inch, which is about the same difference for Aristo-Craft's lowered floor made as a replacement for their 40 foot type cars.


Attributes of the lowering bolster are further illustrated below.

The bolster includes hooks for attaching it to the car's end sill.  Loose fit taken out and leveling is done with installer's inserted shims.


The pad on the lowering bolster is shown below.

ADVISORY: If electing to use the car with USA Trains Intermodal trucks & CamPac coupler boxes, the 2 inline holes are to be used to mount it. Because the CamPac BoxTM was designed to use the pad design with these holes based on the lowering bolster version received by me on Sept. 2, 2021, check with Nico Corbo if when obtaining one to determine if it's a different, changed, version as the box may not fit.




The new lowering bolster is illustrated below.


Car Chassis Removal

Lift out the chassis from the car body & remove parts - example method illustrated below.


Having removed the chassis, cut off its bolsters - example method illustrated below.

ADVISORY: Factory screws used to fasten the chassis to the body shell are very short. They are susceptible to strip out in the body post holes if not too careful when refastening. A remedy is Illustrated below.



Installation of Lowering Bolsters & Chassis

- including re-installation of brake components - example method illustrated below

ADVISORY: In the above example, the installed lowering bolsters had a very desirable snug fit between the car's end sill and chassis that had been cut. Using a thick saw blade to remove the factory bolsters from the chassis and / or not paying attention during the cutting process can result with loose fitting lowering bolsters. If this were to happen, fastening the bolsters at its lip (which would be under the chassis) to the chassis may need to be done, or visa versa, to prevent movement during car operation. To this end, testing the example car in a heavy train has determined that fastening the lip was not needed if the lower bolsters have a snug fit. Shim the bolster hooks - illustrated below (very important for consistency)

Shown below is what the hooks (having been shimmed) look like from the upper ends of the car. The hooks with shims serve to align / level it to the car's end sill.




Installation of Kadee 906 - large foot print box

This is the box intended to be used with Nico Corbo's lowered bolsters - shown below with screws that can be used. It's possible smaller diameter no. 2-56 machine screws could work, too, but I think the intention is to use screws from the Kadee 906 kit - which is exemplified.

ADVISORY: It can take a little force when first fastening the coarse pitch self threading screws into the bolster's holes, so go easy by turning the screwdriver back & forth some as the screw is progressively fastened.


Mount the Kadee 906 Box - example method illustrated below.

ADVISORY: It can take a little force when first threading in the truck fastening screw into the bolster post, so go easy by turning the screwdriver back & forth some as the screw is progressively fastened.


Mounting the Aristo Bettendorf Trucks - method illustrated below. (Note the Aristo metal wheels, ART-29111n, are fitted in the trucks.)



Results - with Kadee 906 Box

Car Height - shown below


Car Weight - shown below


Car Operation Example - illustrated below




Installation of USAT Intermodal Trucks & CamPac BoxesTM

The example CN car so equipped is shown below.


Replacement Trucks

The trucks to be installed on the Aristo hopper car in place of the Aristo ones are same as used on the USA Trains Intermodal car. They are plastic that include suspension springs and emulated roller bearings, however, the bearing caps don't turn because they are molded into the sideframes. That said, these trucks have a short wheel base so they fit well on the hopper car. The installer is to obtain these trucks and metal wheels - illustrated below.

When utilizing lowering bolsters, the Intermodal trucks also serve to lower the car more so (additional ~0.060 inch) when compared to the Aristo trucks (illustrated below), which is good because the 1/29 scaled car is very close to scaled prototype height from the railhead.

The CamPac coupler box is a special order item specific to this application obtainable from Colin Camarillo via his website.

It's a small foot print box to be fitted with Kadee centerset coupler from the Kadee 907 kit that the installer is to obtain separately.

The box which can be painted is shown below with screws that can be used to mount it. It's possible smaller diameter no. 2-56 machine screws could work to mount it, too.

ADVISORY: Before mounting the box, it can be beneficial to pre thread a screw that had not been cut off at its tip into the bolster post hole, then remove it. This will somewhat act as a tap to make it easier when finally mounting the box.



Mount the CamPac box assembly - illustrated below

ADVISORY: When mounting the box it can take a little force when first fastening the coarse pitch self threading screws into the bolster's holes, so go easy by turning the screwdriver back & forth some as the screw progressively fastens.


Mount the USA Trains Intermodal Trucks as illustrated below

ADVISORY: When mounting the USAT trucks it can take a little force when first fastening the Aristo factory self threading screws (that had been used to mount the Aristo trucks) into the bolster's post hole, so go easy by turning the screwdriver back & forth some as the screw progressively fastens.


Verify Coupler alignment with Kadee Gauge



Results - with Intermodal Trucks & CamPac BoxTM

Car Height - shown below


Car Weight - shown below


Car Operation Example - illustrations below



Torture Test on Underhouse Layout - shown below


The SD70 CamPac swinging box, no doubt, is a big improvement when compared to the swinging box Kadee 787 offset coupler arrangement that had been in the SD70 some years ago.



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