First of all let me say that the following observations are in no way critical of Hugh Piggott. I merely state what is written in his 2005 book.
In Hugh's book he makes it quite clear that the constructor should choose either Imperial or Metric - I chose Metric.
Taking the coil wider first, the recommendation is a spacer width of 13mm and a length of 46mm and a breadth of 30mm. I followed exactly and wound ten coils as required. Page 25.
Next is the stator casting for which all the dimensions are given including the thickness which is specified as 13 mm. Page 29 Col midway down.
After all the resin was poured and dried I unveiled my stator and was very interested to see that most (not all) of the `start' wires on the coils showed a white glistening line where they passed over the coil turns.
Photo below.
My thought are:- the coil winding is 13mm thick, but the start wire which runs over the over coils is 1.6mm thick plus microns for insulation which makes the overall stator thickness 14.6mm plus a fraction. The fibreglass chopped strand mat also has thickness, but this no doubt varies when it is wet or dry.
So I am left wondering how good the copper wire insulation is when the `start' wire passes over 6, 7 or 8 wires forming the coils.
When I cast my second stator I deliberately slipped some heat-shrink tube over the start wire where it crosses the coils and have not had a similar repeat of the top fibreglass mat showing glistening lines.
Flux, Hugh, and many more experienced minds will no doubt be able to offer more expert advice, but could this be a possible source of coil failure?
It seems as if I am being pedantic, but I merely raise the observation for opinion and comment.
David HK
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