Re: Rotary gap
----- Original Message -----
From: Tesla List <tesla-at-pupman-dot-com>
Sent: Monday, January 31, 2000 3:06 PM
Subject: Rotary gap
> Original Poster: Jon Rosenstiel <jonr-at-pacbell-dot-net>
> This weekend I finished building a rotary gap and I need someone to share
> the excitement with, you guys!
> My research gave me the impression that 240bps would work well with my
> but right now 120bps seems best. Maybe I missed the "sweet spot" in the
> firing angle with the 8 electrode setup. I probably need to try the 240bps
> setup again, but my gut feeling is that firing near the peak at 120bps,
> 100bps for you 50Hz guys), would work best. (Although it is hard to argue
> with many other coilers successes with high break rates!)
> Feel free to comment and throw darts!
I too have read a lot about SRSGs with lots of electrodes, and always
thought that alignment (firing) should take place only twice per mains
cycle, basically the same as an ideal static gap would. This meant that the
other electrodes were redundant.
I've been led to believe that the problem with a SRSG/NST setup with only
enough electrodes for two firings per cycle is that the phase angle
(rotational position of motor body with respect to the stationary
electrodes) must be correct or dammage may occur to the cap and NST, due to
high voltages (resonant rise).
Now, with your setup you had an electrode presentation every 45 degrees (360
divide 8) which meant that you just could not go completely out of turn and
into a potentially dammaging zone. The design has safety built in.
Leading on from this, you have found a great way of setting up the motor for
correct phasing. You look for the active electrodes (the burnt ones) and
work from there for fine tuning. Without the added expense of machining 6
more electrodes than are required, the use of a temporary stationary
electrode strip or ring (maybe in a comb-like form, i.e. lots of small
points) could be used to allow firing at all angles. This should them
function like a static gap but could give a burn mark pattern from which to
set the correct phase angle.
Just a thought ( one I will test once I build my own SRSG).
Steve Bell (UK)