The 24 Hours of Lemons Forums → Lemons Tech → Master Elec. Switch
Our Master Switch is Chumps legal. We're not sure about Lemons. It's on the right front upright of the cage. You can find the picture of the switch over on Facebook.
http://www.facebook.com/photo.php?pid=7 … =584635399
Richard Newton
Intervention Motorsports
http://www.racecars360.com/Intervention … _Page.html
I think you'll be fine.
Our Master Switch is Chumps legal. We're not sure about Lemons. It's on the right front upright of the cage.
Just two days ago, I discussed this with the Cal Club (SCCA) tech inspector who will be helping with Lemons tech at Buttonwillow in December. He said that the physical location doesn't matter as long as it is easy to see, easy to use by a rescue worker, and CLEARLY marked. It's your life at stake.
I also asked him to clarify where (electrically) it had to be. He said that it must disconnect ALL electrical power to the car, including the starter, engine computer, and everything else. There should be a single cable from the battery to the switch, with all other connections downstream from the switch. Additional switch poles may be needed to kill the output from the alternator.
He went on to say that the 50 amp switches commonly found are not sufficient, and that you should pay the extra bucks for a race-quality 200 amp switch. The cheap switches will not stand up to typical starter current.
All that said, it should be noted that he was speaking from the perspective of the SCCA rules, and that other groups may or may not allow deviations from it.
Just one personal note: My one pit crew experience was on a practice day at Willow Springs. My friend was driving a rented formula car and had come into the pit to check tire temperatures. Without warning, the fuel banjo connector broke and fuel started spraying all over the car and driver. Because the master switch was not obvious, we lost valuable seconds before we got it shut off. Fortunately everything ended well, but those few seconds delay could easily have resulted in a much less happy outcome.
I run a cheapie $6 Harbor Freight switch and change it every race. I have a 100ohm 10W resistor with a 50A relay to shunt current off the alternator.
I bought an 200A battery cut off switch at autozone for 14 bucks, works like a charm.
In Lemons the general rule is if the switch kills the engine and power to the accessories, you're okay.
Our starter is on the battery side of the kill switch but the source for the solenoid is on the other side. This reduces the power running through the switch.
We have never had a problem in tech with our kill switch wiring.
Most electrical mis-wires come from trying to wire the alternator to cut off via the switch. If you run the field wire to the switch it will allow the alternator to "age out" and not blow the alternator's votage regulator. In simple speak - the voltage has to bleed down, if it can't do that into the battery (not present when you throw the switch) it will be dissipated via heat in the voltage regulator. I've heard of a few teams doing this actually demonstrating the kill switch at Tech. You can get away with it a few times... but the regulator can only handle it a few times.
All you have to do is cut the "Field" wire and run that to the switch. That in turn will allow the alternator to age out into the battery and not develop a nasty voltage surge into the regulator...
The ignition circuit I built for the caddy was downstream of the cut off switch, just like Troy mentioned above. I used a "secondary" master (30 amp single-pole/singel throw) from Napa and a momentary push button switch... worked like a charm!
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