Dorsal ~~^~~
Series 7 - Tri-Gear
912 ULS Warp Drive
John P - Regarding the photos of the burned contacts
Were you able to determine exactly what kind of metal the contacts are made of? Almost looks like aluminum??? I know photos often don't show the colors well; but, on the photos of the contacts they certainly don't look like copper, brass or gold to me.
Also - was there any type of lubricant on the contacts when it was originally opened up?
Thanks,
Dave S
The contacts in the ACS switch appear to be silver plated brass. The switch shown is notable in that it is one of the later manufacture dates with the identifying red paint in the screw heads. It is not subject to the AD for periodic lubrication but it did have lube inside.
I have the same switch in my Cessna. It too is a later model and I have a diode in the start circuit. The AD requires that I check the switch is functional in the OFF position. I may open the Cessna switch on the next annual just to have a peek at the contacts.
John Pitkin
A recent series of conversations with a friend & fellow builder, have brought this issue to mind again. I'm probably just beating a dead horse at this point, but I have a couple of thoughts/theories on this subject that I'd like to share with the group.
Regarding the possibility of these ACS keyed switches somehow causing the failure of a sensitive ignition module - since these switching contacts are located in the same enclosure & relatively close to each other, I wonder if there is a possibility of the high voltage back emf, produced when a non-diode protected starter solenoid coil is de-energized, "jumping" the gap or perhaps following a slightly conductive "trace" (caused by previous arcing) from the starter coil contact to one of the ignition contacts, effectively "zapping" an ignition module.
The second thing I'd like to present is that having a switch with a high enough current & voltage rating does not always make it an ideal choice for a low voltage, low current application (such as, perhaps, an ignition grounding switch). It is fairly common to have cadmium-silver plated contacts on high quality switches, and these contacts are sometimes not recommended for use with low voltage &/or current. The reason is because there is not enough (or any) arcing that occurs during use, and some arcing has been found to be desirable or necessary to keep these contacts from slightly oxidizing & creating an abnormal amount of resistance when "closed". This is probably not the case with the ACS switches, since they have a sliding contact action... I don't know.
I'm using a small key switch for start, & 2 toggle switches for ignition (similar to the way that Van's does it with the RV-12) on my Kitfox.
John Evens
Arvada, CO
Kitfox SS7 N27JE
EAA Lifetime
Chap. 43 honorary Lifetime
I wish to second Jim's request!
It would be awesome for us NON-ELECTRICAL TYPES to have a diagram showing how to incorporate the two toggle switches into the Kitfox factory diagram using the ACS switch!
I am particularly interested in how and where the shields of the two ignition wires are grounded in such an installation.
HUGE THANK YOU!
Grover
Grover Wright
Flying a KF IV-1200
ROTAX 912UL
I'm a little confused by the shielding part of your question.
The brown wire from each module is what is switched (to ground) to turn off the ignition module. From what I can see in the books, these are not shielded wires.
Hi Grover,
I think you'd find a lot of useful information about this in the "AeroElectric Connection" by Bob Nuckolls, if you haven't already looked at that. I'll try to explain how he has suggested wiring that circuit. It's probably the simplest circuit on the airplane, so my long explanation will probably be over-kill. You can use single-conductor shielded wire for each ignition module. 16 or 18 gauge would be fine. I used 18 gauge. While shielding isn't necessary on these circuits, and even 18 gauge is bigger than it needs to be, that type/size of wire was suggested for robustness, as well as being able to cleverly use the shielding as the ground conductor. So, a pigtail is attached to the shield on each wire, and each pigtail goes to it's respective common terminal on an ignition switch (toggle, rocker or whatever). Each center conductor attaches to the N.C. terminal of it's switch. At the ignition module on the engine, the center conductors of those 2 shielded wires each goes to it's respective pin on the module connectors (the brown wire mentioned by Larry - refer to Rotax manual). The shields from your 2 wires are then connected to a grounding point ON THE ENGINE, again with pigtails. So, when a switch is "off", contact is made between the common and N.C. terminals, which connects the ignition module pin, through the center conductor to the switch and from there through the shield back to ground at the engine. When a switch is "on", that pin is disconnected from ground as the N.C. contact becomes "open". Again, you don't have to use a single conductor shielded cable - you could use a 2-conductor un-shielded cable for each module (or other combinations of conductors with or without shielding if you wanted to), but the shielded cable is generally a little tougher and more resistant to intolerable damage. It's a nice, clean way to do it, and you've also got shielding, whether it's needed or not.
Last edited by jrevens; 12-01-2017 at 08:57 PM.
John Evens
Arvada, CO
Kitfox SS7 N27JE
EAA Lifetime
Chap. 43 honorary Lifetime
You can run a very simple on-off-start ignition switch when using toggles for the ignition boxes.