A company called  XXXXXXXXX currently produces a scale brass headgear kit based on   XXXXXX colliery in the Rhondda, but the headgear is very different in structure and height to that of Ogilvie  and thus the sheave diameter is smaller. However, they put me in touch with the company that produced the etched brass components comprising their kit and this company agreed to manufacture sheaves to my required dimensions, that is 7.5 cms diameter which equated to approximately 18 feet, the diameter of the Ogilvie sheaves with 40 spokes.

The kit sheaves are made in two parts each of the same diameter and 20 spokes. The intention being to place the two halves together and interpose the spokes thus giving the appearance of a total of 40 spokes. However, this method does not allow  for  the spokes to taper from the hub to the rim  of the sheave as shown in the following picture.

Should a distance piece representing the hub shaft be introduced between the two parallel sheave pieces and the rims joined and soldered, because of the small decrease in the rim diameter, the whole assembly will buckle. Therefore, in order to prevent this occurring I made a cut in the rim between two spokes thus, on joining the two sheave halves, a slight overlap of the rims to occurs. The excess is then cut off and the two halves soldered together.

This sounds uncomplicated but great care must be exercised to ensure that each rim is soldered in the mid-point position of the hub, otherwise the completed sheave will rotate with an unsightly wobble. To make this task easier, I made a wooden jig, details of which are provided in the photograph opposite

Another “problem” with the use of polystyrene is that it is glued with polystyrene glue which is a solvent, so care has to be exercised to ensure that the items to be joined are rigidly clamped  since some movement can be expected in the curing process which can take up to half an hour before it is safe to handle.