14 replies to this topic

[Jim Boemler]

Would this be legal in place of a true master switch?

http://www.ironcanyo...y-isolator.html

[DES4]

I'd guess it'd be legal as an addition to, but not in place of, the mechanical cutoff... the fact that most course workers would be unfamilar with operating it would likely be one reason it couldn't be the sole disconnect, not to mention that a mechanical switch is a reasurringly certain thing; no one likes relying on a complicated ECU to perform tasks in less than perfect situations.

A complicated/expensive solution to a simple problem, however; I do see how it can be useful for automatic cutoff when the mechanical switch might not be accessable (for instance; when the switch side of the car is buried in the tire barrier).

I need to be reminded; why have auto manufacturers replaced $0.98 1157 incandescent taillamp bulbs with $1200 LED arrays on modern cars...?

[KentCarter]

No! The way they show it wired and being used would NOT meet the GCR requirements for a kill switch. It doesn't kill the starter connection nor make the entire car electrically 'cold'.

GCR:
Master Switch – A safety switch which can be actuated by the driver or
other to disable all operating electrical functions, without disconnecting
the electrical supply to any fire system present.

Also, note that it's rated at only 30A. You can kill a running motor with that capacity, but not the majority of the electrical system.

I am considering a latching relay like this:
http://intellitec.co...tery_web/bd.htm
http://www.intellite...5300066.100.pdf
These clever relays require no current to keep them in their current state (on or off), only during transition.

The catch: the control circuit (5A fuse) remains hot all the time. I'm not sure this meets the 'letter of the law' but I don't feel it's terribly unsafe. Thoughts?

[KentCarter]

No! As they show it wired, it wouldn't meet the GCR. It doesn't cut power to the starter or the entire electrical system. Capacity is 30A, enough (barely) to kill the ECU/Inj/Pump, but not the entire car as required. GCR:

9.3.34. MASTER SWITCH
All cars, except Showroom Stock and Touring shall be equipped with a
master switch easily accessible from outside the car. Spec Racer Fords
shall be wired per RFSRII. The master switch shall be installed directly in
either battery cable and shall cut all electrical circuits but not an on-board
fire system.

I'm considering using this latching relay in my upcoming build:
http://www.intellite...5300066.100.pdf
These clever relays only require power to change the state from on to off. The catch: the relay control circuit (5A fuse) must always remain live. Not sure this meets the GCR requirements completely. I don't think a single 5A circuit presents much danger, however. Thoughts?

[Jim Boemler]

I'd like the idea if only there was a mechanical actuation available as well. It bothers me that I have to connect a battery in order to disconnect the battery, although it might not be an issue during a race. As for the hot circuit for actuation, you could wire a single pushbutton "on" switch near the relay, so power would go any further than a normal master switch. Then power the "off" pushbuttons from the switched side of the relay, so that once the relay shut off, those switches were also un-powered.

[Randy Thieme]

'DES4', on 24 Mar 2012 - 10:52 AM, said:

the fact that most course workers would be unfamilar with operating it would likely be one reason it couldn't be the sole disconnect,

As a driver who also corner-works I have to agree. Never thought of if before. (Apart from how effective it might be) I don't think how it works internally is the issue. But anything other than a 1/4 turn handle would be confusing. In an emergency you don't want workers scratching their heads for even just a few seconds.

[Mark]

We looked at several kinds of solid state battery disconnect solutions including some that we built with off the shelf components before selecting the CARTEK. Some of the problems for the 'home grown' designs we looked were that the relays were all electro-mechanical latching relays meaning that there were moving parts inside the relay and all were 2 post vs 4 post which limited the options for alternator isolation. These devices also acted as a switch instead of a circuit breaker which is important.

The CARTEK works on the ground side of the circuit so it is inherently safer than breaking the positive side of the circuit and being solid state there are no moving parts to corrode or fail. We've started replacing mechanical kill switches on a regular basis after noticing voltage drop across the terminals on switches that had been in use a while even though in some cases they had not yet failed completely.The CARTEK disconnect is a circuit breaker design meaning that if any portion of the circuit is compromised the circuit breaker is actuated and disconnects the electrical system until the master reset switch is activated in order to reset the circuit breaker. Once the circuit breaker is actuated all power to car is stopped at the circuit breaker which is typically located near the battery. Being credit card sized, it does not take up much real estate. It is really nice to have multiple kill switch locations on the car without having to run heavy #4 gauge wiring or relying upon a mechanical linkage. I typically have one switch by the fire system pull inside the car and the other switch on the roll bar in the 'usual' location. You could add more if you wanted. The only battery connection necessary for a Miata install is a 18" or 24" negative battery cable, the stock positive battery connection remains in place.

Solid state disconnects are used quite heavily in Paris/Dakar cars, Australian V8 Super Cars, BTC, Porsche Cup, and many other FIA classes so their safety, reliability, and effectiveness has been well proven. Like several other battery disconnect solutions that are available a push button switch is used for the 'corner worker' switch though a three quarter turn switch could be substituted if necessary I suppose.The tech staff here has no issues with the installation or operation and they were very complimentary regarding the design and installation.


Mods - Not meaning to advertise but wanted to address some of the questions and concerns. Please delete this post if you see fit to do so.

[Jim Boemler]

Thanks for jumping in, mark. I'm not sure that having moving parts should be a deal-breaker, since the car has moving parts all over it, but I understand the quest for fewer of them. It looks like the system still doesn't kill the alternator, though. If I'm missing something, can you explain?

[Mark]

'Jim Boemler', on 26 Mar 2012 - 9:35 PM, said:

Thanks for jumping in, mark. I'm not sure that having moving parts should be a deal-breaker, since the car has moving parts all over it, but I understand the quest for fewer of them. It looks like the system still doesn't kill the alternator, though. If I'm missing something, can you explain?

Less moving parts == better. At the last event we had a car that had a kill switch (the usual metal 4 post switch) that was dropping almost 2V due to a bad internal connection. We replaced the kill switch only to find that the alternator (new!!) got killed due to seeing the low voltage and trying to overcharge the battery. More track time lost .

There are two isolation circuits in the system. The circuit connecting the battery breaks the connection on the negative side of the battery from the chassis. The second circuit cuts the power to the engine electrical system. The second circuit is a switched 30A circuit for controlling things such as ignition, ecu, or fuel pump power. This 30A value should not be confused with the switching capacity of the isolator itself which is a stout 200-250A for the STD model. The GT model can handle 450A-600A. A diagram will probably help clarify things.Take a look at this document:

http://cartek.biz/Ba...ataSheet-GB.pdf

Mark

[Jim Boemler]

Thanks Mark -- that schematic clarifies the intent, which wasn't so clear from the schematic on your web page. You should provide a link to that page from your site.

I'm still curious about the SCCA legality, though. The rules specify a "switch", and I'm guessing an argument could be made either way. Is there any history of approval for SCCA use?

[Mark]

Jim, you always ask good questions. LOL. Other than my cars and the other individuals who have purchased from me I have no 'documented' proof of SCCA approval. Obviously my sample size is relatively small. I am not aware of any situations where the CARTEK solution has not been approved with the SCCA. BMWCCA, POC, and PCA organizations have had no issues with this solution as far as I know and many of the cars that run with these orgs use the CARTEK solution. FIA acceptance also counts for something as well.

Mark

[Jim Boemler]

In my eyes the FIA acceptance counts for a lot. Sadly, it doesn't make it legal for SM racing. You'd probably sell more of them if you could get SCCA to actually approve it. There's a risk, of course, but it's probably a good bet.

[Sean - MiataCage]

Well.... I know this might be hard to believe, but the GCR contradicts itself.... See below. B Spec is also going to throw a huge curve ball at this whole topic since World Challenge and Grand-Am require electrical not mechanical kill switches. You have already seen either Chump Car or Lemons move to requiring (2) kill switches and I would be everything I own that SCCA will be moving in this direction at some point soon.

SCCA GCR - April Edition

9.1.7.D.10 - in the Showroom Stock section of the GCR - " An Electrical Master Switch may be installed"

April edition of GCR - SpecMiata Section (SMCS) Section 9.A - "Safety - An electrical master ("kill") switch is required. See GCR Section 9.3 Master Switch.



9.3.34. MASTER SWITCH
All cars, except Showroom Stock and Touring shall be equipped with a master switch easily accessible from outside the car. Spec Racer Fords shall be wired per RFSRII. The master switch shall be installed directly in either battery cable and shall cut all electrical circuits but not an on-board fire system. All terminals of the master switch shall be insulated to prevent shorting out. It shall be clearly marked by the international marking of a spark in a blue triangle and mounted in a standard location. Off position shall be clearly indicated at the master switch location. The standard loca- tions shall be as follows:
A. Formula and Sports Racing Cars–In proximity to the right-hand member of the roll bar, but in a location so that it cannot be oper- ated accidentally. It can be mounted on a bracket welded to the inside of the upright member or mounted so that the operating lever or knob is outside of the body panel immediately in-board of the upright member. This is the standard location on Formula cars built to the Constructor’s Association requirements for Formula 1.
B. Closed Sports Racing Cars, Production Cars, Improved Touring and GT Cars–In front of the windshield on either the cowl or on top of the fender, but close enough to the windshield to be accessible if the car is overturned. Alternatively, it may be mounted below the center of the rear window or on a bracket welded, clamped or bolted to the roll cage or dash, easily accessible through the open window. (Drilling of holes in roll cage to attach the bracket is prohibited.)

Grand-Am
Grand-Am B-Spec - Article 3, Section 2.2 - "Electrical Switch. Electrical switches in accordance with GAR-4-2-1 are permitted."

Grand-Am - GAR 4.2.1 - "Electrical Switch. A master electrical disconnect switch is required within reach of the driver. All cars are required to have additional electrical and fire system switches located outside the car on the cowl at the base of Drivers Side A Pillar.

World Challenge
B.12 - Master electrical cut-off switch in conformance with Appendix D

Appendix D


D.1: The driver, when seated normally with the safety belts fastened, and the steering wheel in place, must be able to cut off all the electrical cir- cuits, except the circuit for the fire system, by means of a spark proof breaker switch. This switch must be located on the dashboard, or center console, and must be clearly marked by a symbol showing a red spark in a white edged blue triangle.
D.2: If the master electrical cut-off switch used by the driver is located within 12” of one of the front door window openings a second electri- cal cut-off switch is not necessary. Otherwise, a second cut-off switch must be fitted which must cut all electrical circuits (ignition, fuel pumps, alternator, lights, battery, etc., but not the fire extinguisher system). It also must be clearly marked by a spark symbol on a blue triangle. The approved locations for the second switch are; along the A-pillar, along the B-pillar, or on the windshield cowl. The second electrical cut-off switch shall be located in close proximity to the second switch/apparatus for the fire extinguishing system.
D.3: If the car is a formula car, or sports racer, the preferred location for a second cut-off switch is the right main roll bar tube at approximately driver’s shoulder height.
D.4: Any exposed electrical contacts on the switch(s) shall be covered.

[Jim Boemler]

Thanks for posting the various regs, Sean. I don't see anything in WC or GA that precludes mechanical switches, though -- are those changes pending now, or what?

From a practical standpoint, once the regs require more than one shutoff point, I think they should specifically allow remote-controlled systems like the Cartek. Otherwise we start wiring the car with significant lengths of hot primary cable, creating more problem than we solve.

[Randy Thieme]

Is there a semantics issue at play? The light switches in your home. Would you normally refer to them as "electrical switches" or "mechanical switches?" I think most people would refer to them as electrical switches. If a person went to a hardware store and asked for a mechanical switch to control a living room lamp they might get a puzzled look. Is more precise wording required? Mechanically operated electrical switch vs. solid-state electrical switch vs. <other>. When the GCR uses the term electrical switch the authors may have been thinking mechanically operated electrical switch.