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Discussion Starter · #1 ·
Caspar Lumber had two Mallet engines purchased 20 years apart. The later one was Samson which had the build log posted previously. The Trojan was the first one and differed from The Samson having slide valves and saturated steam.
Here is a photo of it working
Motor vehicle Vehicle Wheel Rolling stock Mode of transport

And here is a drawing showing most of the detail which I have produced in 1/20.3 scale.
This was a very small Mallet and doing it in 1/32 would in my opinion make it look too toy look.
Rectangle Font Parallel Schematic Engineering

I start by making the cylinders in similar fashion to prior builds. Rather than using a cross port plate I made a similar plate with machining on both sides but with straight porting as shown in the upper plate.
Rectangle Font Gas Screw Metal

i must run now and will post more later.

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Discussion Starter · #3 ·
Thanks Russell
I was a little rushed on my last post and should have given a little more info on the Caspar Lumber operation.
The Caspar Lumber Company operated its own private railway which extended east from the Pacific 26 miles into the lush redwood forest area,125 miles north of San Francisco. It ran a vast array of locomotives but was best known for its two Mallets. It was also known for its massive timber trestles. The railway moved giant redwood logs as photographed bellow.
Art Slope Drawing Rock Illustration

Back to the build. My cylinders were bored out from square stock which was rounded over with 1/4 round roundover router bits. I use my router but these bits can be also used in a mill. The high pressure cylinder is bored out to 5/8" and the front low pressure one is 13/16". The boring is done on the lathe with a self centering four jaw chuck.
The valve plate is cut at 30 degrees to mate with the valve body which extends out from the side of the cylinders.
Wood Rectangle Metal Household hardware Aluminium

The valve body has rounded edges. I use a 3/16" roundover bit mounted in the mill to do this.
Drill Milling Drill presses Jig grinder Drilling

Here you can see the cylinder on the right has had the roundover treatment.
Wood Gas Art Cylinder Cork

And here are the four cylinders so far. I still have some work to do to them but the rough shape is done
Wood Rectangle Gas Household hardware Cylinder

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Discussion Starter · #6 ·
I was wrong about running out of Ft. Bragg. It was the California Western RR that ran out of that area. See the map bellow
World Map Rectangle Font Atlas

Back to the build
Dennis cut out the frame rails from my CAD drawing and I made the crossmembers and assembled them
Wood Flooring Hardwood Plywood Art

The cylinder heads are turned from brass bar stick and the covers are turned from aluminum bar stock
Font Silver Art Circle Jewellery

Wood Gas Metal Auto part Plywood

The valve bodys bolt on to the cylinders with four flat head stainless screws and the covers cover them up and are held on by the snifter which is threaded to 2-56. Below you can see the underside on the left
Wood Gas Electronic device Metal Circle

The LP cylinder has a strange (to me) setup which I have tried to duplicate.
Gas Auto part Metal Fastener Wood


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1,564 Posts
Discussion Starter · #8 ·
Thanks Simon
Here is a few photos of the side rods drive rods and axle blocks
The drive rods and axle blocks are fitted with M5 x 10 ball bearings and the side rods have a pinned slot and tongue connection
Tool Wood Kitchen utensil Metalworking hand tool Hand tool

The side rods are cut on the CNC mill by Dennis to my CAD drawings, On the mill, I cut the slot and tongue wit a 1/16" slitting saw. Note how two pieces of 1/8" material are used to clamp ihe rod between the ends
Gas Milling Machine Machine tool Composite material

1/4" 303 stainless is turned down to 1/8". The side rod is slipped on so that the E clip retainer will be flush with the rod.
The groove cutting tool is at the bottom of the photo.
Wood Gas Tints and shades Metal Auto part

The end is then trimmed to leave about .020 past the groove with the cutoff tool

Gas Rectangle Automotive tire Metal Engineering

The pin is then parted off
Gas Wood Tool Metal Household hardware

Bicycle part Rim Metal Circle Gas
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