Wheels (301 - 307) for the full-size engine were made from wood with an iron tyre in the old tradition of coach making. Personally, I prefer to do it in a similar manner, but with some exceptions due to scale limitations. This work is somewhat outside the normal run of model engineering operations but will give great satisfaction when finished. The main components of the wheel are the rim, spokes and hub. I have made all these parts of wood as per the original. However, readers may decide to make all the components from aluminum alloy or even brass. After all, upon completion when the model is fully painted nobody will see the difference. 
In normal wooden wheel construction the components are the hub, also known as the nave, individually formed spokes, and felloes, or circumferential segments. The parts are fitted together by mortise and tenon joints. The full-size assembly is held together by a shrunk-on iron or steel tyre. 
One can build the wheels in the same way as the original or, as I have decided, make it somewhat lighter, because the model version is not planned for hard street application, therefore the construction can be simplified.

Nave (307) is made from well-dried hardwood and may be a small section of mahogany from any old piece of furniture that can be found. First of all drill the hole, turn to length and fix to a suitable mandrel. Now turn the outside contour carefully according to the drawing. Make sure that the portions where the spokes will be installed are slightly tapered. The naves for the forward wheels need 12 mortises, or dowel holes, while in the nave for the rear wheels 14 are needed. Use some sort of dividing attachment on the lathe setting this to 87deg. out of centre. The holes can now be easily drilled with a 3mm bit as shown in the drawing and the photo below. 

The rims can be reproduced from multi-layered plywood. This mostly water-resistant glued plywood is typically very fine grained and can be turned on the lathe rather well. The rings should be sawn out roughly and glued on a circular carrier of waste plywood or similar. A layer of paper, e.g. from a newspaper, in the glue joint makes later removal much easier. 

The circular carrier is fastened with screws to the faceplate of the lathe. With high speed and a sharp lathe tool the rim can be turned to size (see photo above). Please notice the slightly tapered shape. At the same setting a centre hole of 30mm dia. should be turned in the carrier plate. The hub will be inserted into this hole later for assembly of the wheel; this will help with exact centreing. 
The spokes are slightly stronger than they would be with a correct scale reduction. This additional strength is strongly recommended and will not destroy the overall model's effect. The spokes are cut precisely to length from a strip of fine-grained hardwood with a 6 x 8mm cross section. Each spoke has a 3mm dia. dowel hole on both sides. 

To provide a realistic appearance for the spokes, they must be profiled. The middle area of the spokes should have a lozenge shaped cross section that changes over at the ends to a square cross section. This work can be carried out, either laboriously by hand with a file and emery, or with a profile cutter in the lathe. In the latter case a simple device is needed to hold the spoke temporarily to the milling device on the lathe. The middle area is removed with a flycutter, or any other sort of form cutter, by moving the cross slide (see photo above). 
Stops should be installed to limit the cross slide travel. This will generate equal spokes with smooth arched shaped run outs at the spoke ends. 
To prepare the wheel assembly insert a 3mm hardwood dowel at one end of each spoke with a drop of glue. It should stick out approx. 4 millimetres. This end will be glued into the holes of the hub like a star. If everything is precisely made the rim will fit exactly over the spokes. Other hardwood dowels are now fitted with a drop of glue from outside of the rim through the spokes and the excess ends sawn off. 
If the outside diameter of the rim was made slightly oversized it can now be machined down to final diameter, though it is wise to produce the tyre first as described next. With the tyres in hand one is able to make the wheels to a really good fit. Carefully remove the wheel from the support board using a sharp knife to split the bond line where the paper layer was inserted. 
Tyres (302 and 303) Some 1.6mm thick stainless steel sheet metal is specified for these and I asked a small local company to cut 10mm wide strips on their guillotine for me. The length of the strips can be determined from the formula 'diameter multiplied by pi'. (From memory: the number 'pi' corresponds to about 3.14.) The strip should be somewhat longer because this can be helpful with the bending and forming process. 
The tyres are best formed in a 3-roll bending machine. However, they can also be bent with a mallet or plastic hammer on a piece of round steel material. The formed strip must be cut to precise length and accurately squared at the end faces using a file. Either welding or brazing the joints is suitable. 
The tyre should fit the rims as close as possible without forcing them on. In this case it is permissible to make the rims slightly tapered to make fitting easier. 
Bush (305) and Hubcaps (306) 
Finally, the nave receives a bush and a hubcap, which are made out of gunmetal, bronze or from brass. They should be installed with a small amount of 2-part epoxy resin adhesive. It is recommended you install the hubcaps after painting the wheels. 

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part eight part nine part ten
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