Master Switch Location

I am at the point of installing the master switch in my car. I know there are a lot of posts about it on this forum, but I thought I would get folks most current views. I've read the GCR in regards to switch location, but I've also owned several cars that other people have built and they all had the Master Switch in different locations.

I can think of various advantages and disadvantages for each location, so I thought I'd see what everyone else's opinions are.

So, where do YOU think the Master switch should be located (hard topped coupe)? And why?

Rory

Someplace the corner workers can get to it easily, especially if you're upside down and unconscious. Or sideways up against a tire wall.

For obvious reasons.

Thanks again for the quick reply Greg. So, on the bottom of the car? Just kidding. My thought is just inside the window since that makes it easily accessible, unless that is the side wedged into the tire wall. Hmmmmm.

Where do you put yours Greg?

Mine is just inside the passenger window, mounted to the A-pillar front cage leg. I'm pretty screwed if I end up on my right side against a wall...

Yup. There doesn't seem to be PERFECT location. The passenger side window also means you can't turn it on after you are all strapped in and realize the car won't start because it is off. The driver's side window, however, potentially blocks egress. One in each location in series would solve most of the problems, but adds another failure point.

Oh well.

Any other thoughts?

Lots of SM guys and my RX7 has it mounted on the right side of the main hoop just inside the window.

A Miata is small enough that most people can reach it in that location while belted in.

I can't reach it in my RX while belted in, but it's easy to see and access by corner workers-- assuming you're not on your side against a tire wall. I plan to relocate mine to a more easily reachable location- maybe just farther inside the cage- because this car is wired such that gauges and some 'other stuff' are active as soon as the switch is turned on. Maybe I should just fix that part.. lots of little things on this new car that I'd do differently.

Driver's side to the left of the dash mounted to the upper door bar. Easily accessible through the window, even with the net up. I wouldn't feel safe if I couldn't reach the switch while belted in.

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Originally Posted by Eagle7

Driver's side to the left of the dash mounted to the upper door bar. Easily accessible through the window, even with the net up. I wouldn't feel safe if I couldn't reach the switch while belted in.

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+1 that is what I did the second time.

Put it here:

http://www.gt40s.com/images/Mustang/LeChump/n5.JPG

Stephen - mind posting what you guys did on the RX-8s? Thought that was excellent!!

Don't they use a solenoid-actuated kill switch? I think those are latching solenoids with a shunt-to-ground so you can mount multiple drop switches for them.

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Originally Posted by dickita15

+1 that is what I did the second time.

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I also moved mine from next to the rain tray outside the cockpit to inside to the left of the dash, much more convenient.

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Originally Posted by Greg Amy

Don't they use a solenoid-actuated kill switch? I think those are latching solenoids with a shunt-to-ground so you can mount multiple drop switches for them.

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Yes, that is what we used... Multiple switches, one inside the car for the driver and one outside for corner workers/crew. Not necessarily loved by workers because it is not "commonly" recognized (or traditional) but it is clearly marked with the traditional "off" sticker.

Strphen can you post pics/product info?

Only problem I have with those is that, technically, they may not be compliant to the GCR, which states "shall cut all electrical circuits but not an on-board fire system" (my emphasis). As I understand it, the latching circuit on those is always hot. Thus, you must ensure the latching-relay circuit is properly fused at the battery. Without that, in a crash if one of those wires is grounded it could cause sparks/fire and potentially not drop the master circuit. Can you post a circuit diagram of it?

Regardless, they're good systems if installed correctly, and I don't think anyone will give you any grief over it at all.

I will get a picture and post up a link to the solenoid if I get home before dark tonight. I like it because it uses a very low amp momentary switch that can be remotely located in series, so you can have as many as you want without huge wires running all over the place. The actual solenoid goes near battery. The traditional switches have always worried me because the bigger the wire the hotter it is when it grounds out... if it does.

I mounted momentary switch on the outside on drivers side since corner workers usually go to assist driver first thing and most likely will be in the drivers side if the car if they can be. The one in the inside of the car is on the center dash reachable by drive out corner worker that may reach in from passenger side in the event I am unconscious and the drivers side of the car is not reachable.

Stephen

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Originally Posted by Greg Amy

Only problem I have with those is that, technically, they may not be compliant to the GCR, which states "shall cut all electrical circuits but not an on-board fire system" (my emphasis). As I understand it, the latching circuit on those is always hot. Thus, you must ensure the latching-relay circuit is properly fused at the battery. Without that, in a crash if one of those wires is grounded it could cause sparks/fire and potentially not drop the master circuit. Can you post a circuit diagram of it?

Regardless, they're good systems if installed correctly, and I don't think anyone will give you any grief over it at all.

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Hmmmm.... good question. Not sure how to draw it up but your probably right. I know it passes SCCA pro rules as well as grand-am, but this is club racing not pro...

I well ask jim to make up a diagram to post

I have 2, and did so for 2 reasons:
1 - my preferred mounting in the car wound up being roughly in the middle of the cockpit on the petty bar (diagonal from the main hoop to passenger floor downbar of front hoop) as I couldn't reach the area to the left of the wheel due to seating position. the wheel is extened a good amount and I lowered the column as far as I could. I'm really far back and down in the car.
2 - by the left rear main hoop support in the trim panel beside the engine lid. it's an MR2 and the battery is right there, so this gave me an ooportunity to have an external switch accessible by safety workers and a convenient place to attach the wire harness without modifing it substantially from stock where it tied to the + post of the battery.

the interior switch also interupts ignition, while the exterior swictch interupts injector power. no alternator lines, shunts to ground, etc... either aswitch kills the engine and all electricals with it. main run of cable is batt + -> interior switch -> exterior switch -> starter and power distribution

I wouldn't go with two because they are not a 100% reliable bit if kit. Kill switches do fail and it has happened to me twice. I would not like to double the chances of a failure. When they do break, it can drive you crazy and/or ruin a session.

Agreed, I did mine that way because of access. Single switch installations are preferred.

I installed a latching main cut off switch with multiple on/off buttons in my recently completed & log booked STL Civic. One on/off button for the driver and one on each side of the car for corner workers. It is wired very similar to a standard cut off switch with regard to what happens if one end of it shorts out in a crash. A further advantage to these is that they can be mounted right next to the battery so the wire from the battery to the switch is very short which minimizes the chance that the cable will get cut & short out in a crash. I wasn't sure if this would l pass tech. I had the tech guy with the toughest reputation here in SEDiv issue the log book and he commented that he really liked this setup.

Edit: I think I know what you mean about the hot wire of the button circuit shorting out. I suppose it could happen.

Edited Edit: I want the driver AND the corner workers to have access to a master kill switch.

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Originally Posted by Greg Amy

Only problem I have with those is that, technically, they may not be compliant to the GCR, which states "shall cut all electrical circuits but not an on-board fire system" (my emphasis). As I understand it, the latching circuit on those is always hot. Thus, you must ensure the latching-relay circuit is properly fused at the battery. Without that, in a crash if one of those wires is grounded it could cause sparks/fire and potentially not drop the master circuit. Can you post a circuit diagram of it?

Regardless, they're good systems if installed correctly, and I don't think anyone will give you any grief over it at all.

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This is a good discussion. It addresses several good issues. One of the small concerns I've had with the switch on the driver's side is that, on my car, the battery is on the PAX firewall. This means a 4-5 foot run of large wire that goes all the way across the car and is not isolated by the master switch. That is a potentially large area for a short in the event of an accident. I can convince myself it is the lesser of the available evils since I can have almost the entire length of the cable run under the dash, attached to the dash bar, and inside the confines of the cage and therefore, hopefully outside of the "crush zone".

I had contemplated the idea of using a relay and switch or switches but wasn't sure if it would pass tech. As stated earlier, the switches would be low voltage/amperage and could be fused next to the battery although they would never technically be isolated.

Ultimately, it's all a collection of compromises.

With the first car I built, I had the switch mounted on outside of the car with the thought process that the corner worker could easily reach it if need be.

I got into an accident at Lime Rock, and found myself perpendicular to traffic a little ways after the crest of the downhill where cars couldn't see me until the last second. There was steam (hard to tell at the time and circumstances if it was smoke). The corner workers could not get near me for what felt like a long time do to where I was positioned. The whole time I kept thinking about how I couldn't reach the kill switch.

For me, first priority is that I can get to the switch and turn it off. I've been in enough incidents to know (at least for me), this is the most likely situation. If I were only to do one switch, it would be on the drivers side roll bar where I could reach it as well as a corner worker.

For the kill switch itself, if you don't use Stephen's method, get the heavy duty metal kill switch instead of the crappy plastic one. I've had those fail too often.

I agree with Greg that it is important that the driver be able to kill all power. I had this discussion with the tech guy that issued my log book. I mentioned that the GCR does not state that the driver needs to be able to reach the kill switch. He agreed that this should be in the GCR but for some reason is not. It is far more likely that the driver will be in a more favorable position to kill the power than a corner worker.

For folks doing a new install and not wanting to run welding wire into the cockpit, take a look at http://www.cartekmotorsport.com/tech-info.html

I helped a friend put it into his Miata. The device sits between the battery ground and frame, and has a 2nd circuit to kill the fuel pump or ECU.

The trigger wires are small and you can run multiple. We put one near the driver and one outside for cornerworkers.