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"Precursor" -- scratchbuilt by Larry Herget and named Carol Ann.

Larry Herget's "Precursor"

by Larry Herget
DeSoto Missouri
Photos by the author

November, 2010

Several years ago I received a video called Day Trip to Duck End from Marc Horovitz. This is a very nice video of a British gauge-one trains operating in a garden railway. One particular loco caught my peepers as looking nicely proportioned so I placed it in a remote section of my mental hard drive.

At Diamondhead in 2009 I bought several GardenRail magazines in the flea market. Later, sitting in a lounge chair by the pool, I was looking through them and came upon an article called "Confessions of a Garden Railway Camerman" (issue No. 32 on page 44). Then I turned to the next page and what should appear but a tiny "Precursor" loco photo with the engine all encased in steam. I found out that the prototype "Precursor" was a design by George Whale of Britain in the early part of the 20th Century.

I took a digital photo of the photo of a photo and moved it to the Hewlett Packard for a bit of cleaning up. The resulting picture is what I worked from. I developed a ratio by measuring the photo dimensions with a dial caliper, then converting them to Herget scale.

With nothing to do one day, I laid several surplus parts out and imagineered what would be possible with what I had laying around the shop.
The wheels are McCoy (old) Lionel Reproduction wheels. The first order of construction was to modify the wheels to the proper specs to operate on gauge-one track. Well, over the next day or two of messing with it, one thing led to another and I soon had a basic chassis.
From that point I was hooked. I then moved on to doing a mock-up of the body shape, making a cardboard cab and tanks and a plastic-pipe boiler.
The tanks and cab are made out of a piece of steel from an air-conditioner housing. The boiler and smokebox are of .032" copper, rolled, riveted, and silver soldered. 
So far it was nothing but a static model. I had to have a way to propel it. I decided on an oscillator, geared to the front driver axle, with the side rods driving the rear axle. The cylinder bore is .375" with a .660" stroke, one direction only (no reverse). The gears are from Small Parts Inc and are made by Boston Gear. They are a 3.8 to 1 ratio.
The Butane fired boiler is very spartan, having only a regulator, water glass, safety valve, and Goodall-type filler valve. The dome is a cut down Mamod part. Copper-to-copper components are Fos-copper brazed; all bronze and brass components are silver soldered to the copper shell with 45% silver solder. The finished boiler was hydro tested to 100 psi. The safety is set for 35 psi.
The lubricator lies up front between the frames, just under the smokebox. The smokebox door opens by lifting the latch at the left so I can look in and see the poker’s fire output. The smoke stack is an accumulation of several parts, silver soldered together.
After running the engine on blocks several times (as it was to cold outside), we loaded up to go to Diamondhead, "Precursor" included. It got its first run there on the medium track. The first run was a bit sluggish, requiring full throttle. By the third run, the throttle was just cracked open, with the engine pulling several cars very fast. 
Builder Larry Herget
Date built 2009 (construction took six weeks)
Gauge 45 mm (gauge 1)
Scale None in particular
Boiler Single flue
Fittings Safety valve, water glass, throttle, Goodall-type valve
Fuel Butane
Blow-off pressure 35 psi.
Cylinders One double-acting oscillator, geared 3.8:1 to the axle
Reversing gear None
Lubricator Displacement
Dimensions Length, buffer to buffer, 14-3/4"; width, 3-1/2"; height 5-3/16"
Weight 6 pounds, 3-1/2 oz.
Here's a movie of the locomotive in action. If, for some reason, it doesn't work, click here.
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