Sorry; multiple Steve s. That question was for Steve B, about the combo switch/breakers.

I liked the looks of the fuse block you picked, but couldn't get Bussmann to send me enough info on terminals, etc, so I used their other design, with 1/4" blade terminations.

Charlie

On 7/17/2014 7:47 PM, steve Izett wrote:

Hi Charlie

"How did I protect the wires going to the circuit breakers?”

I’m not sure I understand your question (sorry if I’m being slow)

I have a 10 guage feed from battery through key switch to the engine critical blade fuse buss which is built into the Bussmann fuse block (see photo).

I have seperate fuses for Pri and Sec Injectors. From these two fuses electrons go to separate Pri & Sec 4 pole switches (one pole used to activate cold start, the other three poles parraleled to meet current requirements of two injectors, these are mounted with the coil test switch) [I may remove these switched in the future as my own weighing of risk is currently on the side of the switches presenting higher risk and complexity than chances of actual injector failure] 

From these switches current flows to the Pri & Sec injector pairs. Then the individual injectors feed back to the EC2 FETS which then return to one of my earth busses.

I used the Bussmann fuse block as it enabled high density power distribution while enabling me to access each circuit easily for testing. This fuse block sits at the bottom centre of my panel in front of a console mounted throttle quadrant making it easily accessible and central for distribution throughout aircraft. 

Cheers

Steve Izett

On 18 Jul 2014, at 4:24 am, Charlie England <flyrotary@lancaironline.net> wrote:

Thanks, Steve.

Guess I should have known even more options would turn up. :-)

I like the idea, but how did you protect the wires going *to* the switch-breakers? Are they just on a high current bus with the rest of your breakers? If so, it might not work for me, since I'm using automotive fuse panels. Right now, I've planned for multi-pole injector switches wired as shown in the manual (but with a separate pole for each injector), mounted next to Tracy's engine control panel (the coil test switch is there, too).

Charlie

On Thu, Jul 17, 2014 at 2:08 PM, Steven W. Boese <flyrotary@lancaironline.net> wrote:

---

From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Charlie England <flyrotary@lancaironline.net>
Sent: Thursday, July 17, 2014 12:14 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] power circuit design, was: actual current use by a rotary?

 Charlie,

 

I chose to install switch type circuit breakers, one for the primary injectors and one for the secondary injectors.  I did this because if one injector fails, the backup function requires the corresponding injector of the other rotor to be shut off and then the cold function to be activated.  If there were a power draw that tripped the breaker, the result would already take care of that first step.  The down side is that the cold switch needs to be used for the backup function instead of being taken care of by the second pole of the recommended DPDT injector switch.  This required no additional space on the panel.

 

I did the same thing for the leading and trailing coils but for testing purposes rather than risk mitigation.

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

 

 

 

Well, time for some followup.

My 1st draft for circuit protection looked a lot like what Steve describes (thanks, Steve), with individual fuses for virtually everything, including an individual fuse for each injector and each ignition coil. After ruminating over the actual loads for the injectors & coils, I'm having second thoughts. The GM coil harness I have in hand has a single DC power wire for all four coils that it feeds (obviously isn't a part intended for flight, but included in Tracy's installation manual).

The obvious concern is whether an individual coil or injector failure has a statistically significant risk of taking out the power supply that's fused for the total load. If there's no statistically significant danger, weight & complexity could be reduced by feeding the coils and injectors as groups.

So, is there any consensus on how to handle injector & coil wiring? IIRC, there have been some coil failures in flight; were those planes wired with a single fuse/breaker protecting all the coils, or with individual fuses/breakers for each coil? What about the injectors?

Any failure modes I'm missing? (other than a dead short on a supply wire, of course)

Thanks,

Charlie