Re: async rotory gap?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi David,

As you know, with a sync gap we have the ability to fire the gap at
concentric points along the AC
cycle. The async of course cannot sync and therefore will fire at good and
not so good points along
the AC cycle. There are a couple basic async gaps. One is an AC motor. This
will run at something
like 1750 or 3450 rpm's. The other would be a DC motor. The DC motor has
the ability to run at
variable speeds as a function of input voltage. With DC, you get to play
around with the break rates
and can find break rates which please spark growth. With the AC motor, you
would need to build a
circuit to perform this function.

I've run all three types. The AC induction motor is the worst of the three.
The break rate is slower
than the AC charging cycle at the cap, and therefore fires the cap all
along the AC cycle including
points at which the current and votlage nears and crosses zero. At these
points, the gap may not
fire. When firing is skipped, the energy in the cap remains and the next AC
1/2 cycle continues to
charge the cap to a higher voltage. When the electrodes align, the gap
fires. As you can see, the
cap voltage is firing at several levels of potential and the arcs are
spuradic as well as the
charging and gap firing system.

The variable DC motor is really fun. You can speed up the motor vary the
break rate. Although you
can near the AC charging cycle, you cannot lock onto it. On my coil, I
found a break rate around 280
(if memory serves) as a point the coil liked. I did get some pretty good
sparks varying the gap,
however, the electrodes were crap on that system. I haven't run this async
motor on my g10/tungsten
rotor, but I know the sparks would be much better.

I personally like a sync gap mainly because I can control the charging
system in more ways than just
the break rate. One can play with break rates with a sync gap, but it goes
in steps (120, 240, 480,
etc.). This can be modified with odd numbered electrodes as well as
electrode to electrode offsets.
However, you can't play with break rates in fine detail as with the
variable async gap.

I wouldn't say that a variable async is better or worse than a sync gap.
But I would say a
non-variable async gap is not good and can cause problems in the charging
system components
including the tranny because you have no control over it.

Bart A.

Tesla list wrote:

> Original poster: "David Knaack by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dknaack-at-rdtech-dot-com>
>
> I see plenty of info on synchronous rotory gaps, but
> I haven't seen much about async gaps.  What are
> the advantages and disadvantages of using such a
> beast?
>
> It seems that it would have a definate price advantage,
> and also make the step to a syncronous setup shorter.
> How does it compare to a multiple static gap?
>
> DK