THE FRAMES
THE SUSPENSION & WHEELS
THE CYLINDERS
THE VALVE GEAR
THE COUPLING RODS
MOTION ASSEMBLY
BRAKES
AXLE PUMPS and ASHPAN
FOOTPLATES,DRAINCOCKS & BUFFERS
SMOKEBOX
ODD JOBS & TANKS
FITTINGS
THE BOILER
ASSEMBLY
THE LAST LAP
AFTERTHOUGHTS
I've been looking for my next engine to build and as I wanted to stick to narrow gauge, several locos were possibles.
However, as I wanted to make one with Walschaerts valve gear, the choice was reduced considerably. A friend produced
a 1982 copy of 'Model Engineer' with a 3-1/2" gauge Hunslet and suggested doubling it up to 7-1/4". Sounded like a
good idea but there are problems.
The engine in question was called the 'Spencer' after one which was used in Harrowgate Gas Works. I've since
discovered this version was changed so that it would pass through a low tunnel. So it had a lowered chimney and a
very low rounded cab!. These engines were the ones
supplied by Hunslet for the transportation of munitions etc. behind the lines in the first World War.
This photo shows the layout of the Hunslet 4-6-0. The problem comes in choosing the scale. The war time track was 60 cm. but on returning to the UK they were converted to 2 feet, 2 feet 6 inches and for some reason, one metre. I got this information from the ME article. The 3-1/2 scale was based on the one metre track. By scaling this up to 7-1/4 I got a rather small engine, somewhere around 3 ft 6 ins. Using 2 foot as the gauge gave me an engine over 5-1/2 feet long, which is just a bit too big for me to transport. So I'm going for the 2 ft 6 ins. which will give me an engine about 4 ft 6 ins.
I'll be doing all the drawings this time, so I expect it will take longer to build. I shall also be working in metric as I find it so much easier than imperial although I still find it hard to visualize sizes in metric. Working in CAD I'll be able to superimpose drawings to ensure accuracy.
Here is a list of the relevant measurements with mine subject to alterations.
Gauge .....................................2'6"................7-1/4"............184 mm
Length OA ...............................18'5-1/2".....4'5-1/2"..........1360 mm.
Height from rail to chimney .....8'11-1/2"......2'2"............660 mm.
Max Width ................................6'3-1/2"......1'6-1/4"...........463 (465) mm.
Fixed wheelbase......................5'6"...........1'4"...............405 mm.
Total wheelbase .....................13'..............3'1-3/4"...........958 mm.
Driving wheels ........................2'................5.8"...............147 (145) mm.
Bogies ................................1'6-!/2"...........4.47".............114 (115) mm.
Some are rounded up for simplicity.
So to the first stage which will be the drawings for the frames and buffer beams which I will have laser cut.
At the moment, I'm waiting to hear from the Leeds Industrial Museum Curator who is looking into whether they have
the original drawings.
I'm afraid very little is being done in the workshop at the moment. I'm spending a fair amount of time on the
computer doing drawings. However, I have managed to get the frames drawn up and laser cut along with the bogie
frames and buffer beams. I've included me in the picture to give an idea as to the size.As can be seen, the
frames are quite complicated but almost identical to full size. The only difference is with the axle box cutouts
because full size has a large part which bolts on to the bottom of the axle box, which is not really practical
for me to do.
I have been lucky, in that the Leeds museum did have the drawings of the Hunslet and its subsequent alterations.
The GA drawing is excellent and drawn in 1.5 scale. The museum only charged me £8.46 which included postage,
packing and VAT.; really excellent service. All I have to do is measure the subject on the drawing and
double the dimension. Just about everything so far has scaled perfectly. The design of the boiler has taken me
a long time as I had to visit the boiler maker and discuss it with him as he has to submit the drawings to Lloyds
before he can begin work on it even though this won't be for about 18 months if I'm lucky.
One thing I have included
in my design is twin water pumps driven off the rear axle. Having used both pumps and injectors on a loco, I
much prefer the simplicity of the pumps. I will also have an injector. I have discovered that if too much
additive is put in the water of a steel boiler, then the injectors and ejectors get bunged up and won't work,
and it is quite a job to get them clean again!
The club exhibition is coming up on the 19 August and I'm supposed to be in the workshop doing some CNC stuff, so I'll have to spend a bit of time on that. I also have visitors staying so little is being done!!