[T3] relays and delays...

[Jim Adney]

On 12 Mar 2011 at 20:59, Frank Meek wrote:

> In response to several of the statements made, I will first say that the
> "weight distribution" was only one of the reasons for forward battery
> placement, (Porsche was incredibly "systemic" in their designs), in addition
> to cutting in half the route from battery to starter...a real reliability
> boost for these cars. 

I only see a downside to the wiring here. The medium current solenoid 
wire length stays about the same, while the larger starter current 
wire run more than doubles in length.

> Additionally the wire gauges of the Porsches are significantly heavier than
> VW's, heavier even than my '65 T-2, which, until I converted it to 12v,
> installed a self-supported starter and a relay, had its share of starting
> "idiosyncratic moments."  I still find myself unconsciously looking for
> slopes when I park.  Of course, all the 6v originals had much heavier wire
> gauges than the 12v vehicles to reduce resistance.

In general, 6 V cars need about 4x the copper cross section to get 
the same performance. You need 2x because the current tends to be 
double, and another 2x because you can only afford half the voltage 
drop. Most cars didn't actually get this much, so 6 V cars tend to 
have more trouble with voltage drop. All of this, plus the weight and 
money saved on copper make up the lion's share of the reason 12 V 
systems were introduced.

BTW, I reconnected with an old friend last fall and asked him about 
what happened to the proposed 42 V automotive systems that I thought 
were just around the corner. It turns out that they've been dropped 
for a number of reasons, but one of the interesting ones is that if 
they made 42 V headlights, the filaments would have to be so thin 
that they would be too fragile for use in a car.  

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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