Saturday, May 1, 2021

New Drawbar Mount for Athearn-Genesis 120-C-6 Tender

In this quick blog I'll be looking into the process of converting Athearn-Genesis 120-C-6 tender for use with standard brass steam engines.

Balboa Models, SP 3266 mocked-up with Athearn-Genesis 120-C-6 class tender.

The Prototype

A quick side note on this prototype, the 3266 was the only Mk-5/6 rated to Owenyo on the Jawbone Branch, which makes it very unique.  Usually 3-4 Mk-2/4s were rated at any point from 1950-1954 specifically by number for operations.  The Mk-5/6s from Balboa are quite common brass models to be had over the last 10+ years.  So this is a fairly easy prototype engine model to make.

SP 3266 near Olancha with excursion to Owenyo in 1952 - Phil Serpico photo - - southern_pacific012_t

I don't want to go too far down the prototype rabbit hole here, but the SP 3266 was used in the 1952 fan excursion trip run to Owenyo with the 3237.  It seems from a couple of the photos, such as the one above, the SP 3237 was only needed for the eastward (north compass) trip to Owenyo.  The 3237, may have departed and returned to Mojave, while the 3266 remained in Owenyo with the fan special for two more days.

The 3266 probably was a regular Mojave based engine during that time, normally working the KI (Tehachapi) local and the "Blitz" (Palmdale) local.

The Problem

The SP 3266 Balboa model came with a standard (but incorrect) 100-C-1/2 tender.

Balboa 100-C-1/2 class tender with weird UP-style high-speed trucks.

As far as I can tell the SP swapped all of these smaller tenders to other smaller types of engines.  The SP 3266 during the post-war years was upgraded to 120-C-3/6 class tender, along with most of her sisters also receiving 120-C-series tenders.

However, the brass 120-C-3/6 class tenders are hard to come by... and when they're found, they often command similar prices to that as the Mk-5/6 engine itself!

SP 3266 laying on her side - showing the problem with the tender.

The Solution

Athearn-Genesis unlettered 120-C-6 Tender.

Athearn-Genesis came out with the 120-C-6 tender with their 4-8-2 MT-4 class engines.  They were also made available separately both painted and lettered and undecorated, but painted.

The Catch

The Athearn-Genesis model has a unique drawbar arrangement.

Unfortunately, the Athearn-Genesis model comes with a rather goofy drawbar design... a similar concept to the BLI's articulated cars, which has an open 'claw' on the engine, which snaps around a post inside of the tender, above the frame.  I don't trust this design to handle heavy draft loads, plus the brass engines are equipped with a standard metal drawbar with two holes on the tender side to fit around a pin or screw.

Time to Disassemble!

Due to the large number of plastic parts around the upper shell of the tender, and the front deck plate is fairly fragile plastic, I needed to disassemble the tender with two screws.  One screw is in the middle next to the brake cylinders and one between the rear two axles of the rear truck.

Interior of the SP 120-C-6 class tender.

The interior of the Athearn-Genesis tender is... interesting.  The brass-style drawbar will make things a little tight to have a larger group of wires running between the engine and the tender under the frame.  I'll only be wanting two pairs of wires going to the engine where the decoder is to be located.  Each side of the tender wheels pick up power, and the two wires to the rear headlight on the tender.

New hole drilled with No.50 drill bit, tap for 2-56 screw.

I used a power drill motor with the No.50 drill bit pressing against the tender frame, which I was holding against a piece of 3/4" plywood.  The plywood was needed to keep the fine details, such as the vertical grab bars and ladders at the tender's rear.  A 2-56 tap is then used to cut the threads in the new drawbar hole.

I'll be removing the jumper connection between the engine and the tender.  This requires removing the screws at the front of the large weight stack, and lifting the weights off for now.  The front screw in the PC board is removed and the PC board is lifted up.  Allowing the wire jumper to be unplugged and removed.

Tapped 2-56 hole ready for 3/8" x 2-56 screw.

The 120-C-6 tender is reassembled, ready for 3/8" x 2-56 screw.  I cleared the forward drawbar hole with a No.42 drill bit (clearance drill for 2-56 screw).

SP 3266 with new drawbar screw in place.

In Closing

SP 3266 with completed tender drawbar conversion.

This is not the last time I'll be going into the tender to rewire it and probably adjust the weight balance over the front truck.  The DCC sound decoder in this engine will be in the lower front of the boiler, between the smokebox and the forward of the gear box.  The speaker will be in the smokebox.  This is my preferred method of installing DCC decoders in steam engines, as it keeps the majority of the wiring in the engine and the runs very short.

I'm planning to do a blog post specifically on the DCC installations in brass steam engines, so this post will be kept to just what is unique about the Athearn-Genesis 120-C-6 class tenders.

Jason Hill

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1 comment:

  1. Thanks for digging into this Jason. Those Athearn tenders have multiple uses behind other brass locomotives.

    --Bill Decker


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