A Mechanical High Voltage Rectifier!
 

Considering the expense of buying High-Voltage rectifiers, either discreet or integrated as a bridge unit, and the likelihood of blowing them out either because of a misadjusted spark gap or arc-over caused me to consider alternatives. Most coilers don't use rectifiers as they use AC to power the tank circuit capacitor. I, on the other hand, chose to power mine with DC for considerations already discussed.

Since, in my design, I will use a synchronous motor to drive the spark gap, why not use the same motor and put a mechanical commutator on the same shaft and use it to rectify the AC (actually, it is a modified rectification) as you will see.

As far as I know, this idea is mine. I have seen nothing similar in any research I have done. If you see it elsewhere, please let me know. If you use it, give me credit.

The Commutator (Fig. 1)

The commutator is assembled from Plexiglass or similar insulator with conductors either inlaid or glued on as above. A, B, C, & D are brushes, probably rescued from old motors.

Single Cycle AC 
(Fig. 2)

Commutated (Modified Rectified) AC 
(Fig. 3)

Circuit (Fig. 5)

Assume the commutator (Fig. 1) to be synchronized such that the 0 degree point is on the top when the output of  L1 A wire   (Fig. 5) is at it's 0 voltage point, ready to start it's positive voltage swing (Fig. 2). Also assume the commutator is rotating in a clockwise direction when view as above (Fig. 1) 

At 0 degrees brush A is connected to C and B is connected to D. At this point AC is starting to swing positive while BD is starting it's negative swing. This continues until we reach the maximum voltage point at 90 degrees. At this point brushes C & D open and the transformer is totally disconnected from the primary tank circuit whereas diodes would still be connected. This normally wouldn't cause any problems as the diodes become reverse biased............ unless the spark gap fires! This would cause the entire output of the transformer to to be shorted through the diode(s). You see my concern about blowing diodes.

Using a commutator gives us the entire time between 90 and 180 degrees to fire the spark gap and allow ringing while the transformer is totally disconnected. This is also an effective way to stop the RF from getting back to the transformer.

At 180 degrees brush A is connected to D and B is connected to C which actually reverses the output wires on the transformer (L1). and continues until 270 degrees where the transformer is disconnected again and we can fire the gap again. This is graphically illustrated in Fig. 3.