Wednesday, March 22, 2017

SP 2424 (Part 1) - Truck Conversion

This is a post about one of those models we've all had for years and it's a very nice model.  Then over the years more research has come out about the prototype and the issues start to bug you more and more, until you finally do something about it.  Well, that's pretty much the story of my model of SP 2424.

Where The Car Started

It started as one of the three road numbers offered for the yellow and gray SP "City" scheme in Athearn-Genesis's first run of 77-C-3 chair cars.  Several prototype cars of this class were painted into this scheme over the years.  Not knowing much about which number to choose at the time I picked up a SP 2424.  I probably should have chosen another number which was painted into the scheme earlier, but I didn't.

Roughly Out-Of-Box Athearn-Genesis 77-C-3 model of SP 2424.  I added some window shades and light weathering.

The model comes with the "triple-bolster" style trucks typical of the 1937-1941 Pullman built Daylight cars.  The SP 2424 was first painted into the COSF (City of San Fransisco/Overland) scheme in June 1955 and was one of the cars heavily reconditioned for the assignment.  Earlier 77-C-3s assigned to City service were not upgraded as the 1955 group were.

The Historical Upgrades

The upgrades consisted of changing the seating from the (normal) 48-seat Chair Car configuration to the 40-seat deluxe "Leg Rest" configuration for cross country travel between San Fransisco and Chicago.  Mechancially the car was also refitted with new GSC 41-NDO trucks with Budd disc brakes for higher speed running.  These trucks were also more common on the newer City consists, so the UP and CNW carmen could inspect and repair the cars easily while on the eastern end of the run in Chicago.

Here's the model laid over the SPHTS Vol.1 photo and the new Walthers trucks laid under the Athearn trucks.

The Model Upgrades

Weathering The Diaphragms

I decided to take a few minutes and weather the striker plates of the diaphragms with a few different techniques.

Striker Weathering

The end of the car doesn't usually get cleaned very well by the car washers between trips, so I weathered it a bit heavily.  The strikers are usually bare steel, which will be any variety of rusty on cars that don't get used much, to fairly shiny and polished on cars that are in regular service and are always rubbing on the striker of the next car in the train.

The strikers were also greased, so often I will use black and dark gray colors to simulate the slobbers of grease that coat the strikers of well maintained cars. - think of the look of a 18-wheeler's 5th wheel hitch - that level of grease!

Prismacolor Pencils, this set was about $15.  Additional color pencils can be had for $1-2 in a multitude of colors!

I used silver Sharpie for the basic bare metal striker, with black Sharpie and Prisma pencil for the rubber gasket which keeps water and such from dripping on the passengers.  Additional sienna brown and dark brown color pencils are used to get the shades of rust on various parts of the striker which aren't being rubbed clean.

Walthers GSC 41-NDO Trucks

The Athearn-Genesis underframe and trucks use pins and very small springs to conduct power from the track up to the lighting system in the car.  The replacement Walthers GSC trucks (920-2200 blk & 920-2201 silver) don't lend themselves to this style of power transfer easily.  Instead I'll be using my standard methods of power pickup which I will cover in a later post.

The trucks were painted a dark gray-black and then airbrushed with Harbor Mist Gray at angles to keep the shadows.

The trucks were painted a gray-black and then sprayed from above and below with Harbor Mist Gray (standard underframe color for COSF cars).  This way the black colors stayed in the spring and other deep recessed details of the trucks.  I also painted the wheel faces, as the truck are roller bearing, which do not leak oil the same way that plain bearings do.  A light wash of black over the springs and the bearings brings out the depth.  This was needed since the coat of gray did a little too well covering some of those areas.

Painted and modified bolster on the Walthers 920-2200 GSC 41-NDO trucks.

This pair of trucks' wheel treads cleaned with thinner and a bit of paper towel.  This is a good habit to get into because most metal wheels are not cleaned after being manufactured these days.  There's often a coating of machine oil on them which also doesn't do any good for the cleanliness of a model railroad.  Letting the wheels run themselves clean on a layout is a good way to make everyone's engines dirty and operate poorly!  Not to mention make the other operators mad at you!

Also be sure the wheels roll freely in the sideframes.  Lubricating the trucks with a small drop of light oil on the bearings helps reduce friction and also improve conductivity for the lighting system.  Also remember to check the gauge of the wheelsets.

New Bolster Arrangement

The main change with converting the model to the new trucks is changing the bolster arrangement on the Walthers trucks.  I start by measuring and cutting a pair of small pieces of 0.020" styrene sheet to fit on the bearing surface of the Walthers truck bolster.  I drill a clearance hole for a 2-56 screw through the center of this plate, this will reduce the oversized hole that comes with the Walthers trucks down to my preferred mounting screw size of 2-56.

The car already has body mounted couplers adjusted to the correct length for close mating of the diaphragms, as seen in the photo below.

In this photo the new spacing bolster block is to the right of the body bolster pad.

I had already made some modifications to the Athearn-Genesis body bolsters to lower the car slightly before I started on this truck conversion project.  After modifying the truck bolster, I estimated that the body bolster was about 0.080" too short.  I cut a pair of blocks from 0.080" sheet styrene to about 0.125" square.  This doesn't need to be too accurate, as it need to clear the inside stepped edges of the top of the styrene truck bolster pad I added to the trucks.  The blocks are drilled with a clearance hole for 2-56 thread as well.

The body bolster block is placed on the bolster and a 2-56 screw is ready to go in the truck bolster.

While I glue the bolster block to the body on most of the cars that I use this style of conversion, on this car I have decided not to at this time.  I chose to do this partly because I already had lubricated the body bolster with graphite and I doubt that gluing will be very effective.  Also with it lubricated already, the truck should be more free than if I tried to glue it and force all the movement to be made at the lower bearing.  This is also why I chose to drill the spacer block with a clearance hole instead of a tapped hole, which I would do if I was going to glue it to the underframe as part of the body bolster.


Here's the car reassembled with the new trucks and car adjusted to ride at the right height.  Currently the lighting systems in the car are disabled because I've not reconnected the trucks to the interior lighting system.  That will be completed later.

Left side of SP 2424 with new trucks.

Right Side of SP 2424 with new trucks

That will do it for this post about the SP 2424 (Part 1).  In SP 2424 (Part 2) I cover installation of an OwlMtModels Roof A/C Hatch.  In other future posts about this car I will work on rebuilding the underbody details, as well as rearranging the seating inside for the correct 40-seat configuration.  While this car is historically a few years too new for my main era of modeling (1948-1953) because of the paint scheme, I might as well upgrade the details to make it correct for its era.

Jason Hill

Related Links:

Mt.Nebo (Part 1) 10-Section-Obs-Lounge - Shows how to tune Walthers Trucks

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