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Push Starter and R Mag question

WingnutWick

WingnutWick

Well Known Member
Hello!

As I wrap up my panel conversion and various other mods, I have a starter question. I had previously made a push to start system where the starter wouldn't engage with the right mag on due to no impulse coupling. I'd start with the R mag off and once the motor started just turn it on.

My question is...can I just connect the R mag to the two starter switch connections so when I depress the starter button it also closes the R mag loop (grounds the mag i.e. turning it off)?

Thank you!

Wingnut
 
Without seeing your schematic: would your proposal connect the P lead to 12 volts? And, when the starter is off, is the mag always 'hot'? This could be dangerous to anyone working on the engine and turning the prop.
 
It'll be hot but I also have two magneto switches to control that. Basically I took the wires fro your standard key starter. I'm thinking that it would connect the P lead and the power that runs to the starter relay?? Would this do anything?
 
you could do this with a double pole single or double pole switch that would ground the P-lead whenever you push the button. You would still want a switch that connected to the P-lead wire that would ground it in the off position. You definitely can NOT use a single pole switch for the start button or, like others said, you would be sending voltage to the P-lead.

Again, your P-lead would need to go to both the R mag switch and to the starter switch, so either switch could ground it.
 
That's what I figured. Unfortunately the switch only has a normally open circuit and a normally closed circuit. I would need the normally open one for both the starter and mag, so I think I have to stick with my original method of having the R mag switch off for starting.

Out of curiosity, any idea as to what would happen sending that 12V to the P lead?
 
Some (well, me, anyway) would say that all that extra stuff is unnecessarily complex & adds failure points.

But if you want to do it, just add an automotive 12V relay (<$5 from multiple sources) to the circuit. Pushing the start button would apply 12V to the starter contactor, and also to the coil of the extra relay. The relay's normally open contacts would be wired across the mag switch terminals, so that when the relay is activated, the p-lead wire pair are shorted whether the mag switch is on or off.

Charlie
 
rv7charlie said:
Some (well, me, anyway) would say that all that extra stuff is unnecessarily complex & adds failure points.
Charlie
Click to expand...

I will heartily second this statement. Ignition is one of those things over which I want absolute positive control - that's why I went with toggle switches for the P-leads. Having flown a Grumman Cheetah for a number of years, with its "Off_R-L-Both" key switch and pushbutton starter switch, I grew accustomed to placing the key in the "L" position for starting and immediately switching to "BOTH" once the fire was lit. Doing the same thing with toggle switches is very easy since they give such positive indication of their switching status. And they tend to be quite reliable if one chooses to use the MS-type switches available from Spruce and other suppliers.

Having had a left mag fail, I can assure you that I wouldn't want anything to get in the way of the right mag working. Adding complexity would seem to defeat this goal.
 
Great feedback guys, thank you! I think I will just KISS. I was more trying to be fancy than anything else as I am perfectly capable of remembering to have the R mag off during start. I like the thinking of not wanting anything to get in the way of the R mag firing in case of a L mag fail.

Thanks guys, as always I can come here for insights and technical knowledge as I continue my learning.
 
I have precisely that setup...two switches for the mags, a master switch, and a push-to-start. The push-to-start grounds out the right (non-impulse-couple mag). Works like a champ.

I also have a keyswitch safety interlock...no matter what position any of the switches are in, the engine can't start without the key being in and ON (either by using the starter or moving the prop by hand).

I'd be happy to send you the schematic for this if you'd like.
 
Sending the 12V to the P-lead would, at best, pop the breaker or blow the fuse. The mag points are grounded at some point in the rotation.
 
THIS thread contains a circuit that I drew for another builder. It uses two toggle switches for the mags with absolutely no chance of forgetting to shut off the right mag during engine cranking. The two toggle switches also function as a momentary start button. A key switch could be added in series for security.
 
Let me add....

This is a YOUR ignition you are talking about.

If you don't get it "right" it could be the cause of a serious injury on the ground and should it fail in flight, it could cause a serious injury when you hit the ground.

It is best to keep it as simple as you can!

(The same goes for your fuel system.)
 
WHen I had two mags, I used a DPDT switch for the right mag. One pole was used to traditionally switch the P lead to ground. THe other pole was used to feed 12 volts to the starter switch. You could not activate the starter unless the switch was in the off position. This approach insures positive control of the mag and doesn't introduce a new failure point for mag control.

Larry
 
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