Secondary Coil Winding Jig

After reading lots of tesla build diaries and after visiting many HV websites I have realised the only way to create a nice secondary coil is by winding it on some kind of jig. One of the favourite ways is to use a lathe and if the lathe is not long enough to create an "extended" tailstock. Unfortunately my lathe is nowhere near big enough as the chuck is only around 80cm and there's just not enough clearance to spin a length of 110mm (4") pipe. So I have decided to build a jig, but to keep it simple, it will be human powered (son Damien to be exact) and will be big enough to wind up to 6" diameter coils, just in case I want to upgrade from 4" in the future.

   One visit to B+Q later. I have

Pack of 2 lengths of 1800mm by 144mm by 20.5mm planed pine.
1 metre length of 10mm threaded bar.
1 metre length of 12mm OD 10mm ID steel tube.
Small bag of 40mm wood screws.
4 10mm plain nuts.
Wood glue.

While at B+Q I got the wood cut to the lengths needed for construction. The cutting service was free and meant all cuts where perfectly square.

The above pic shows the finished article. The base and the backboard are both 900mm long and are glued and screwed along the adjoining edge. The end plates are made by gluing and screwing 2 pieces of 144mm by 144mm by 20.5mm together. The end plates can then be stacked together and drilled at the same time. The hole needs to be 12mm. I then cut 2 40mm lengths of 12mm tube and hammered one into each hole in the end plates. This creates a neat metal bush in each of the wooden end plates. The two end plates were then screwed to the back and base board. I didn't glue them so they can be repositioned if needed.

Here's a closer view of one of the end plates. Doubling up and using 2 pieces of wood provides a bigger bearing for the shaft and also adds extra strength. The 12mm holes are offset to front and top of the end plates. This provides clearance from the base and back board to accomodate a 6" diameter pipe.

Not easy to see, but there is a neat little bush in there which should stop the threads chomping away at the hole.