Steve's Workshop


 

 

I first saw this engine on Mike Boucher's website. I liked the simple design and Mike kindly sent me the plans so I could make one for myself. The design was by a model engineer called Dr. James R. Senft and the construction was detailed in 'Live Steam Magazine' in 1976.

0 Gauge Locomotive 'Dickins'

 

The best description of the design, is given by the article itself :

"Dickins was inspired by a photograph of a British toy locomotive dating back to 1890. Although differing in mechanical detail, Dickins shares the general appearance of its larger antique toy prototype and consequently shares its quaint charm.................Dickins was designed to run on standard O-gauge toy track - the kind supplied with clockwork train sets - or on Lionel 027 track. The locomotive has ample power and speed for its class. It carries enough fuel and water for a 20minute run pulling 2 tinplate cars around a 2ft-diameter circle of track, at a rate in excess of 2.5 feet per second."

 

 

 

The Frames

The plans specified steel for the frames but I followed Mike's example and made them from brass, for easier working and so the model could be left unpainted.

This photograph shows all the frame components in a partly assembled state.

 

A combination of 8BA and 10BA hex head screws were used for the assembly. At this stage in production the rear wheel bushes had been located and a test with the rear axle showed that the frames were quite square and that the rear wheels could spin freely.

 

 

 

 

The Wheels

The wheels were made from Aluminium bar. They were made with 5 spoke holes instead of the 4 shown by the planes because my ML7 lathe could index 5 holes more accurately.

The rear (driving) wheels had one hole left out to allow room for the crank pin

 

The Boiler

The boiler was constructed from brass. Although not a recommended material for a boiler, brass was adequate with this kind of low pressure boiler, on a small model such as this.

The main body was a piece of 1.25" brass tube cut to length and squared off in the lathe

Then the 2 end plates were formed from circles of brass cut from a sheet. The flanging process is shown in the steps below.

 

The tools used were a small brass headed hammer and a former turned from aluminium. The former had a slightly rounded edge and was the same diameter as the outside of the brass boiler tube.

The brass disc had been cut from sheet brass of the correct thickness

 

This sequence of photographs shows the 4 forming operations used to get the final shape.

Each operation was preceded by an annealing step, including the first one.

Initially the hardest thing was locating the blank disc centrally on the former. This was done by eye.

 

 

 

But once an initial shape had been formed, repeated location on the former was easy.

 

 

The main objective was to avoid buckling the rim by not rushing the process and using regular annealing.

To anneal the disc, it was heated to red hot and left to cool slowly in the hearth.

 

 

This photo shows the finished shape.

These steps were then repeated on the second end cap.

In total it took about 1.5 hours to make the former and fabricate both end plates.

 

Here are the finished end caps after cleaning and assembly to the boiler shell.

The brass hammer had marked the end caps in some places, a copper or plastic hammer may have been better.

To finish - The caps were placed in the lathe and the tool marks were polished out. The end results were satisfactory.

 

 

Once the bushes and mounting pin had been made the whole boiler was brazed.

This image shows the boiler under a hydraulic check at 30psi (twice the working pressure). The tissue paper was used to pin point any leaks, but none were found.

 

Cylinders and valve gear

The valve gear was of the oscillating type, the components are shown below. All port drillings were made using the jig detailed in the plans, which gave working results first time.

Valve Gear Components

 

The Burner

The burner was a simple 2-wick alcohol fuelled design, fabricated from bits of brass and copper. The hole through the side of the tank was to house the rear axle, which also acted as the support for the burner itself.

 

 

Initially the flame from the wick farthest from the supply tank was very low. So string from the wick was removed to allow it to siphon more easily and this seem to help. The flames were still not quite balanced as shown in the photo, but good enough.

 

 

 

 

The supply lines to the wick had been made slightly too long and the front wick was rubbing on the front axle. So the supply pipes were bent into an 'S' shape to shorten the overall length without reworking all the pipe-work.

 

 

Assembly

Here is an image of the Loco fully assembled (without burner).

 

 

 

The engine ran at 900rpm off load, on 5psi of air pressure

Testing

The engine was tested on compressed air to check the valve timing. The air hose was connected to the smokestack, in place of the safety valve and the compressor set to 10psi.

Initially there was a tight spot at one of the con-rod ends and so the hole was enlarged slightly to make the engine more free running. Then, after adding some light oil and a few turns of the wheel, it was off.

 

 

 

Steam Test

Here is the engine on it's first steam test.

It ran well - but not for long. Even with the water level quite low (allowing for more steam volume in the boiler) the engine would only run for about 15 seconds before slowing and stopping.

 

 

 

 

A new burner was made with lager wicks and larger bore fuel lines.

The larger burner would obviously reduce running time but should provide more heat to prevent steam exhaustion.

 

 

 

The Second Steam Test

The new burner made for continuous running for 7 minutes before the fuel was exhausted.

 

Finally here is Dickins running on the garden track. Click the image for a short video. Warning 1.8Mbytes

 

 

Click to play Video

Warning.

Having built and run this locomotive I think a warning should be issued, as it does pose a certain fire risk.

Numerous times the little locomotive has come off the rails at the corners and erupted into flames due to the spilt mentholated spirits. This is OK outside but I would warn against using the loco indoors for safety's sake.

 

 

View from the foot-plate

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