Hi, I have finally got my six inch coil working pretty well now , many thanks to you. I am getting a steady three foot of streamers and I still have to tune it some more. I had to add another turn to the primary and probably still need one more. I built another rolled cap and after burning up two motors on the rotary gap I finally did it right and ground the four flats in the armature. My question is , what exactly is happening when you grind the flats to make it synchronus? Is it breaking up the field so that it isn't at the same frequency as the primary circuit or what is it actually making it synchronus to? Also is there anything that will make the arcs fatter as they seem to be thinner than they were on my four inch coil? Thanks Mario