David,
I got a free treadmill and this monster was the treasure inside! Overkill?
Sure, but I won't complain about it though!
Ideally any gap would achieve first notch quenching. The actual time
involved would depending on the resonant frequency and the coefficient of
coupling (which determines energy transfer).I don't have fancy lab
equipment, but ideally I would be able to ascertain if I am hitting first,
second, third, etc notch quenching. Until then, it may come down to
experimenting by adding more and more gaps to see if performance increases
or not.
I am sure many would agree what I am aiming for with the gap is not
necessary, but then again, Tesla Coil construction in the year 2020 would
also broadly into that category too.
Maybe I will use acrylic instead of PVC...
~Dan
Kansas city area
On Wed, Jan 29, 2020 at 5:32 PM David Rieben <drieben@xxxxxxx> wrote:
> 3.5 hp DC motor? Unless you already have this motor in your possession,
> that seems rather large for turning the rotary gap assembly of a <10 kVA SG
> coil. I believe my DC treadmill duty motor is rated up to 2.5 hp and it is
> PLENTY of motor for turning my 12” x 1/2” G-10 rotor with its (8) 3/8” dia.
> X 2” long tungsten flying electrodes. Each of the tungsten flying
> electrodes also have a 3/8” aluminum shaft collar on each side of the disc,
> so there is a total of 16 of those shaft collars that are being flung
> around, too. They help to secure the flying electrodes in place on the disc
> as well as assist in their cooling. I control the motor’s speed via a small
> panel mounted variac and a FWB rectifier to give infinite speed control of
> the ASYNCHRONOUS spark gap assembly.
>
> My stationary electrodes are (2) ea. 1/2” dia. X 3” long solid tungsten
> rods that are each simply mounted in 1 1/4” brass square stock that is
> about 2” long, and is also mounted against a 1/8” thick x 4” diameter brass
> disc, to help dissipate the heat, and is mounted against a lexan frame
> housing.
>
> I have found that this provides all of the quenching that I need and I run
> my coil at power levels that often exceed 15 kVA and can approach 20 kVA!
> From my experience, it seems that you can get to a point where you may
> actually over quench the gap when you start stacking multiple series spark
> gaps. I think someone has pointed out that each spark gap typically drops
> several hundred volts, so if you have a whole bunch of seriesed gaps,
> you’re gonna be losing some significant power in your gaps, too.
>
> Finally, Gary is correct about the PVC deteriorating in the presence of
> the strong UV that is given off by the spark gap. It will turn a dingy
> yellowish-brown and loose it’s mechanical integrity and also become
> somewhat conductive. I ended up having to wrap the 2” PVC support pillars
> of my primary circuit assembly with aluminum duct tape to reflect away and
> protect their surfaces from the intense UV of the spark gap.
>
> Hope this helps,
> David
>
> Sent from my iPhone
>
> > On Jan 29, 2020, at 12:03 PM, Daniel Kunkel <dankunkel@xxxxxxxxx> wrote:
> >
> > Hello Tesla List!
> > I am starting to work on my next spark gap for a 6-10 KVA magnifier. It
> > seems the definitive spark gap design is that from Richard Hull/TCBOR
> using
> > a rotary gap (to control timing only) combined with a multiple break
> series
> > gap (to control quench only). Is there a better approach for gap design
> and
> > construction?
> >
> > Currently my plan is to use a 3.5 HP DC motor to spin a G10 disk with
> > tungsten electrodes and combine it with the PVC + copper tubes + fan
> series
> > gap.
> >
> > Thanks,
> > ~Dan
> > Kansas City area
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