3600 RPM, 240 BPS
Synchronous Rotary Spark Gap
(SRSG)
Timing Considerations
(04/22/03)
3600 RPM 240 BPS Synchronous Rotary Spark Gap
Here are some photos of where a rotary spark gap actually fires at different power levels.
When the power is low, the gap fires at a close spacing.
But when the power is high, the gap fires when the total gap distance is about 3/4",
which is well in advance of the closest spacing.
So even when you adjust your synchronous rotary spark gap at low power, it may still be off at high power.
This is one reason why it can be desirable to use an electronic phase adjuster.
John Freau has a design for just such a thing.
Here is the SRSG at full speed. A flash photo at low power.
Here is full power (14.4 KV and 20 A). Note how the spark is above, not on the side.
Zoom in at low power. Spark is at close gap spacing (side), about 1/16" on this side.
Zoom in at high power. Spark is at far gap spacing (top), about 3/8" on this side.
Zoom in at high power. Spark is at far gap spacing (top), about 3/8" on this side.