OwlMtModels Mini-Kit Conversions for Accurail 40ft Boxcars

Time to upgrade my Accurail SP single-sheathed boxcar fleet

This post is to finally show the new conversion ends from OwlMtModels to make the basic Accurail 40ft Single Sheath USRA clones more like the SP B-50-8,10,11, and -13/14-class cars.  Accurail has offered these kits with either a 1920s "7-8" pressed steel end or a 4-vertical post wood-sheathed end.  Unfortunately, neither is right for SP's ~8000 single sheath boxcars of this rough design.

The stock wood ends of Accurail boxcars are nice, but the details on the ends aren't correct for the SP's boxcars.

Over the years I've built over 20 of the Accurail cars for my fleet during the late 1990s and early 2000s.  While resin models of these cars are available, I don't really want to build a new fleet of resin kits when I have so many Accurail cars already in my fleet.  Now that I'm building the Jawbone Branch layout, these converted Accurail cars will become the backbone of my SP wood-sheathed boxcar fleet.

The answer in the form of OwlMtModels' newly designed 3d printed ends.

The ends are 3d printed and include a large flange on the interior side to bond to the interior of the injection molded roof and sides of the Accurail body.

Multiple versions are in the works at OwlMtModels:

* OMM 4072 B-50-8/10/11 wood ends (with option for either plain end or lumber-door end.)

* OMM 4073 B-50-13/14 rebuilt steel Dreadnought Ends, vertical staff hand brake. (Almost all B-50-14s and many B-50-13s fitted during the 1930s.

* OMM 4074 B-50-13 As-built wood ends (with option for either plain end or lumber-door end.)

* OMM 4075 B-50-13/14 rebuilt steel Dreadnought Ends, with lower platform for power-brake refit.

In this post, I'm only working with pre-production samples of OMM 4073 and OMM 4074, which will be made available for sales at the SPH&TS 2024 Convention in Sparks, NV in mid-October.

The ends are designed to use Carmer cut bars, and so a pivot is provided for such, but not included.  Yarmouth Model Works makes several photo-etched Carmer levers, which should work on these parts.  Grab iron holes are printed into the ends, but probably have back-filled with resin before the processing was completed, so those will need to be drilled out.  The brake staff holes will probably need to be cleared too.  Then a suitable staff (wire) and wheel (probably Cal-Scale) will be installed.  The retaining valve has been printed in-place, but a 0.009" wire retainer pipe should be fitted on the Dreadnaught End version of these parts.  The wood ends have the retainer pipe printed-in-place.

Bonding flange which will allow the glue to form a tight grip between the body shell and the new ends.

Pre-assembly prep on the ends is minimal, but important none the less.  I carefully make a few light passes with my mill file to remove any remains of the support contact points from the bonding areas outside of the rib.  This will insure that the part fits smoothly against the end of the chopped Accurail car body.

Chopping the Body

Two long cuts are made in the ends of the body, just inboard of the sides.

The first step is to chop into the injection molded ends, along the inside edge of the sides.  Once the cuts are made, the end is popped out.  Note: I usually only do one end of the car at a time, this allows the other end to provide good rigidity and support to the sides and help keep everything square throughout the process.

I just bend the end of the car back and forth until it fatigues and breaks loose.

Step two is to trim back the sides to remove the original corner posts.  I did part of this with the razor saw in the past, as I got a little impatient on the second end (A-end), I went ahead and chomped through the last 1/16" of sides with my sprue-cutters.  I marked the parts to discard with a black Sharpie marker, stopping just at the edge of the wood boards.  It did require some careful alignment to be sure I wasn't going to bite too much off.  

Dry fitting the A-end for B-50-13/14 'as-built' wood end.

Side view of A-end after filing is complete on 1st prototype print.

In Step three, the last 0.015-0.025" of the sides are filed or sanded down to the ends of the wooden boards.  On the roof, the lateral 'running board' support should be as far back as I trim that section.  File everything smooth and even across the whole end.  I check the progress on keeping it square and even with a regular dry test fitting of the part.

Finished prep work sanding and filing car-end.

I should note at this stage I also am sure to clean the remains of the ends down to the inside shape of the body.  The new ends are designed to match the shape of the body's natural interior.  If I cut deeply into it, or make a chamfer around the end, it shouldn't be a problem.  However, I do like to keep the structure as clean as possible.  A few scratches or even rough sand paper marks could help with the bonding, but I don't want anything that will prevent the ribs on the new end from fitting down tightly when fitted.

Inside view of bonding flange with a bit of extra ACC flowed in after primary glue pass was made.

When satisfied that the dry fitting is good, as in the ends fit tightly against the body all the way around the joined edge with the Accurail body.  I remove the end and carefully put a small amount of thickened ACC/CA type glue along the inside corner of the end and the exterior side of the bonding rib.  I extend the glue application down the ends to the bottom, past the rib, where the end will still be in contact with the car-side.

I found often it is helpful at this point to have the frame of the car in-place inside the body.

Showing how I pivoted the end into place.  This is a little trickier with the larger flanged end.

The end is then slipped into place from above, allowing the notch in the end to wrap around the coupler box, but not bond to it.  In the past I've used a couple rubber bands to hold the end in place, however if any ACC/CA glue squeezes out, then it's very easy to end up with parts of a rubber band glued to the exterior of the car!  When I built this pre-production test conversion, I just held it with my fingers on the end, avoiding the sides of the end until the glue was cured.  This took only about two minutes before I could let go and it was well bonded.  (Production 3d prints have a checker pattern on the exterior of the flange, which should allow for an even stronger bond to form.

3d printed end and rubber bands to hold them in place while the glue dries.

Another option on the bonding process, is to use larger rubber bands (I used ones from larger broccoli bundles from the grocery store), and the carefully stretch these around the car body with the underframe in place.  I usually like to add a bit of shim to the car-side over the non-ladder area, so the rubber band can't get down against the joint where any ACC could come out, bonding the rubber band to the model!

In Closing

That pretty well wraps up the list of how to do the conversion of the basic Accurail car.  This should be applicable to even factory painted models.  Pre-painting the end should be possible, although I would avoid getting paint on the area which will be the bonding surfaces of the 3d print.  

Pacific Electric B-50-13 with B-50-13/14 Dreadnought End installed, before detailing.

A few details still need to be installed; wire grabs, roof walk end supports, and brake wheel/staff.  Also on most of my conversions, it's easier to just remove the plastic stirrup steps on the model.  I'll be replacing them with standard U-shape A-Line stirrups installed.  The PE car will be getting the 45ft radii curve brake rigging modification to match detail photos in a separate blog post.

T&NO B-50-13 with original Wood Ends.

New end reporting mark decals will be needed to finish the car after the conversion is complete.  Remember that the SP standard in the 1910s-1931 were to have the ends and roof painted black or have black car-cement (aka tar) applied.  After 1931 the SP started shifting to overall Freight Car Red, and Anthony Thompson suggests that the last black roof/end cars were so painted around 1942.  So paint your models accordingly.

Jason Hill

Related Articles:

Previous modeling posts on these classes, before these ends are available.

Modeling B-50-Series Boxcars (Part 3) - Plastic Options for B-50-8, -10, & -11 class cars

Plastic Options for B-50-12, B-50-13, B-50-14 class cars - Accurail & Tichy models

SP 24864 (Part 1) - Kitbashing B-50-10 from Accurail 40ft Boxcar - Not including these parts, I'm waiting for the earlier B-50-8/10/11 ends to be produced.