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Friday, 4 October 2019

0 Gauge Class 33 Scratch Build - Part 2

The chassis floor was made in two halves due to the limited size of my 3D printer bed. The halves were butt glued together and a strengthening bridge glued across the join, perhaps not long enough as there is minor bowing. When a body is fitted it should pull it straight into line.

The chassis design turned out to be just as complex as the bogies! Below the floor in the centre is an early period fuel tank and battery box. The battery box spans full width but in the prototype there are two separate boxes with some other mechanical gubbins in between that would not be seen on the model. There are other small fittings to the chassis sides faithfully reproduced from photographs but I don't have a clue what their function is!
The next photo shows the speedo cable. that connects between chassis and bogie axle box. The axle box speedo connector is removable so that bogie and chassis can be separated for maintenance purposes. The cable run is a little lower than it should be.

Note the green chassis side indicating the finished model will be a Class 33/0 in green livery.

I assumed the buffer beam was a simple rectangular block with buffers and coupling. On closer inspection it is far from it. The ends are angled and  there is a mass of fitted pipework and ports, about half of which are hidden by the buffers in the photo below.

I looked at the intricate screw link coupling and decided it would be too difficult to make (or was I getting bogged down with the model and wanted a quick way out). So, I purchased the Dapol Terrier spare (shown in the photo below). Unfortunately I misunderstood the suppliers product description thinking the 'set' on offer was a pair for each end of the loco. In fact the 'set' was one hook and one link array, except they failed to supply the hook! I needed a second 'set' but, this would become a very expensive solution for what are very small parts. I had a think about it, had a eureka moment and devised a simple, Dapol look alike, yet fiddly method of making a link array from wire. It was so successful I should have taken photos and write a tutorial. Maybe later.

Sprung buffers use an adaptation of the innovative Peco method, the method is shown in the photo below. The springy wire is cut from square section 4mm scale point roding steel wire that I had in stock The buffer shank is a nail with a plastic disk stuck on the head.
The question is, will it traverse a curve without impediment. I don't yet have track so I tested it satisfactorily on a Peco turnout paper template. If problems arise in practice I'll need to rework the chassis side fittings that hang down to increase bogie swivel.

To Part 1 of this series.

Monday, 30 September 2019

October Website Cover

Promotes the next outing for our Thornycroft Sidings N gauge layout.

View the cover here.

Friday, 27 September 2019

0 Gauge Class 33 - Scratch Built

Class 33 33202
I tried to recall how I came to scratch build a Crompton Class 33 diesel locomotive. It is probably the most complex and time consuming modelling project I have undertaken to date.

Without doubt the styling proportions of the 33 make it a pleasing sight to my eye, compared to other Southern diesels. I was also attracted to the r.t.r. Lima 0 gauge offering, which is remarkably inexpensive to buy off eBay - around the £50 mark. But, the reviews I read revealed it to be woefully inaccurate dimensionally, so bad that some serious 'cut and shut' work would be necessary to bring it into line with the prototype.

With a 3D printer to hand I decided to design and make one. First point of reference are a drawing and photographs. There is a partially dimensioned drawing in a book that I own -  Diesel and  Electric locomotives of the Southern Region by N. Pallant & D. Bird. I copied this and enlarged it to 7mm scale and from this most dimensions could be measured. There are also drawings available from the web. Despite this some fine details are missing or obscure in the drawings so, recourse to the web for photographs was in order. Most are distant profile views like in the example above. It required much time to find suitable close up and side views to work from.

The bogie's were tackled first as I considered these to be the most difficult items to design and make, firstly because of the large number of details on them and secondly the precision fitting of motor and gears, particularly optimum gear meshing. Before starting the design I had to source wheels and motor & gears. All were eventually found on ebay. The wheel sets are Peartree Engineering 3' 7" finescale diesel wheels. These do not have locating spigots but use bushes mounted on the axles and fixed to the bogie frame. The motor and gear set are by an unknown manufacturer. There is a risk the motor would not be adequate and even having made the bogie and run successfully there is still uncertainty over whether it will pull the body weight and train.

The bogie is essentially two separate parts screwed together. An inner part is the motor frame containing motor, gears, wheels and pickups. If there are issues with the motor/gears performance needing change then only the motor frame would need to be redesigned for a different motor (in theory). The outer part of the bogie is the decorative part.

The parts were printed in black, which had an undesirable effect of hiding the details from sight. Weathering was applied with brown and beige pastel scrapes to highlight the details. Some mechanics of the bogie were omitted from the design either because they were too fine to be printed, could not be easily discerned from drawing or photo or, would not be seen from normal viewing angles.I think most details are included though.

In the above photo we can see the motor mechanics, noise suppression capacitor and electrical pickup, which rubs on the axles. One of the wheels on each axles is insulated. The metal can of the motor connects to the one side of the armature coil and the pickup for the power return. The power feed is collected from the other bogie.
The other bogie with its power pickup is shown above. The design and build is identical to the motorised bogie without motor/gears fitted.
And here are the two bogies alongside a scale drawing. Not yet obtained track so am using two lengths of Hornby 00 gauge Super 4 track for now

At the end of the day the cost will be about the same as a second hand Lima 0 gauge model. At least mine will be more accurate and making it from scratch fulfils my creative need.

To Part 2.

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