Re: triggered gap idea

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Clearspring1-at-aol-dot-com>

Jim,

Your idea of using the magnetically-triggered OEM circuits used on car 
engines to drive the HEI coil on a TSG has the fine advantage of engineering 
backed by millions of units in service.  It seems to me it just begs to be 
taken one step further by triggering the circuit by a simple rotor with 
(choose your own break-rate) tiny magnets mounted on a cheap, low-power 
synchronous motor such as the teletype motors that are still showing up as 
surplus.  With no heat as a concern, quarter-inch lexan instead of tough and 
pricey G-10 would simplify the rotor-building process a lot.  A very small 
variac would then suffice for John F.'s phase-control spark timing technique. 
 

Michael Tandy

> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
<jimlux-at-
> earthlink-dot-net>
>  
>  There has been much discussion on various and sundry triggering circuits
>  for a triggered gap.  Since most of us are using auto ignition coils,
>  rather than cobbling up something from dimmers, etc., why not just use the
>  electronic ignition amplifier that typically accompanies that HEI coil.
>  
>  In several systems I've built, I've used various MSD ignitions to fire an
>  auto coil from a TTL timing source.
>  
>  Wretchedly expensive if bought new, but, if you're scrounging coils at the
>  junk yard, you might be able to grab the solid state driver as well, since
>  it's all encapsulated in the distributor.  Maybe a good source would be the
>  ones that Ford is replacing in the big recall?  They don't meet car spec
>  (temperature related failures, I believe), but they'd be more than good
>  enough for triggered gap use.
>  
>  These amplifiers typically trigger of a very small pulse from a magnetic
>  pickup, and should be readily adaptable to being triggered of an
>  optoisolator or 555 or something sync'd to the power line.  Modern
>  ignitions need to time the spark to better than 1 degree of crank rotation
>  at 6000 RPM (= 100 RPS = 10 mSec/360 = 27 microseconds) to meet emissions
>  requirements.  All you'd need is a beefy(probably 5A minimum...)12V supply
>  to run them.
>  
>