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Discussion in 'The light stuff area' started by MadRocketScientist, Jun 19, 2009.
Hi there, single engine is approx 75 mph with flaps retracted.
Thanks for this!
I translated another article I had from French, This one was a bit of a pain to get right. I hope it is somewhat close to the intent of the original article!
A question for anyone willing to chime in,
I have been pondering my wiring layout and started working on the diagrams and I am considering having the mag switches for each engine on their respective sides of the panel. Mainly under the assumption that it would be less confusing as to which engines ignitions were being switched during mag checks etc. I was thinking of locating the two switches for each engines ignitions, to each side of the engine temperature gauges in the picture below (where the red switches I added in MSpaint are )
I haven't really seen any panel layouts from twins apart from the pictures of CriCri that I have downloaded. I haven't seen it done this way before and I am wondering if there is any reason not to do it this way?
I generally fly with one hand and flip switches with the other. Sheesh if the switches are side by side are you really going to mistake the left from the right?
Put switches on the side the throttles are. Unless you put right throttle on right and left on left. Then I want video.
I like it, I've flown all kinds of twins and they are next to each other but some of these are big cockpits. This panel is so little and you are centerline I think you should put them wherever you want and what makes sense for you. Looks to me like it would be easy to reach them with the same hand.
Thanks for the comments everyone, I will think about this some more. Current thought is to keep the switches on the opposite sides of the panel but at the bottom corners of the panel in line with the starter switches.
The whole panel is easy to reach with either hand, there definitely isn't room to swing a cat in this cockpit. A mouse? maybe?
Thinking out loud, here are a few other CriCri panel pictures found around the internet.
First is the super cricket from the 70's that had the two 30Hp rotax engines installed. The two ignition switches are directly in front of the throttles. This switch location seems to be used on around 50% of the CriCri builds. Interestingly even the ones with dual ignitions seem to only have two switches. When I get the chance I will have a closer look at ZK-LBW at the local airfield, it has the same setup but with dual ignitions on the engines.
This next image is the first CriCri ever built, the switches are up on the panel besides the ASI (in the shadow of the canopy frame). I have pictures of several different cockpits with this switch location.
Here is ZK-CRI, the switches for the four ignitions are down beside his left knee.
and finally this panel has the ignition switches about half way up the panel on the left (above the RPM guage).
I think it has to do with flow, when you do your checklist it should flow from one item to another.
I like the way you have it. The distances are not great so easy access, with either hand or same.
Yours makes it dead simple and hard to make a mistake. Very easy to scan and see whats happening and compare. I like it.
Don't over complicate, no need to follow tradition, it is not a complex big twin.
And here is the starter wiring diagram.
At this stage I am keeping this complete system separate from the others with its own higher voltage 18 volt battery. I haven't sorted out a way to switch the battery in and out of the circuit other than physically unplugging it. the system runs as a total loss battery, I should get possibly hundreds of starts from one charge but it will get charged more often than that. The battery is sized to supply the peak current draw when turning the engine over. The actual capacity needed for each start is very small.
I also intend to run all the electric systems as a total loss to make things simpler. Charging batteries is nothing new to me as I fly electric radio control aircraft almost every day the weather is suitable.
I have been doing some testing of the ignition modules and sorting out what DC-DC converters to use to supply the 6 volts to them from the (at this stage of planning) 12 volt aircraft supply.
I bent out ground strap on a pair of sparkplugs to test the ignitions under more realistic conditions to what the plug experience when the engine is running. I learned this trick from over at the FlyingGiants RC forum. The longer spark distance simulates the higher resistance of the fuel air mixture in the combustion chamber. It is also helpful for testing if the ignition will reach full voltage or if the spark leads need replacement due to internal arcing etc, as well as show up issues that might not appear when testing with the standard plug gap.
I have four of the older Rcexl A-01 ignitions and one of the newer A-02 ignition modules. The newer one is rated up to 12 volts, the old ones I have only accept from 4.8 to 6 volts. According to Rcexl, even the newer ignitions work best with around a 6 volt supply voltage. I think it keeps the amount of heat in the module low. Both of these modules are barely warm to the touch after running for an hour, the older one being ever so slightly warmer due to the higher energy consumption.
I tested the older ignition with the bent strap plugs installed. On 6 volts, the ignition draws 130mA at idle (no spark) and with a current draw of 560mA at 8000rpm. I changed the plugs to some with a 0.6mm plug gap to see if the current draw was any different, pretty much the same results. I used the Rcexl ignition tester and the ignition hooked up the tacho to set the rpm.
Interestingly the newer ignition uses a lot less with a idle current of 83mA and 350mA @ 8000rpm.
I have a few cheap DC-DC buck converters from Ebay that I have been using in my radio controlled planes and gliders. These are 5 volt but the voltage can easily be changed to 6 volts by swapping out an SMD resistor.
After downloading the datasheets for the IC, it appears the Chinese like to skimp on the inductor size, presumably to save cost. While this doesn't seem to affect the operation at all, since it works perfectly fine with my radio and receivers, the output ripple might be slightly higher than it could be. The inductors are sized according to the output voltage, the higher the output, the greater inductance needed. I can easily get the correct inductors to go with the voltage I use, whenever the nCOV pandemic situation clears up that is!!
The ignitions also run just fine on these cheap voltage converters just as they are.
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