BC12D Cowling Fairings for Screened Plugs.

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

Here are pictures of the mag switch cover, you will note there is a spot for a wire inside the cover that you ground to the frame of the aircraft. The mag wires are shielded wires which you also ground to the cover's ground screw, which then gets grounded to the aircraft. The other pictures are showing it installed on the mag switch and the mag wires going to the two mounting points on the mag.

I found the mag switch cover on Ebay.

[Mick W]

Re: BC12D Cowling Fairings for Screened Plugs.

I met with the OP today, and showed him my Ercoupe cups (as yet uninstalled) but he appears convinced on going for the ugly cowl bumps.

I also tried to persuade him to keep the Bendix mags, much better IMHO than the cheap-and-cheerful Slicks.

I don't think I managed to change his mind.

Rob

Tell you what Rob , don't we only need the Cups on the front Plugs , so you keep 2 & I'll take the other 2 off your hands , job sorted !!.

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

Though that is what some people can do, I found I needed all four on the top. For some unknown reason my cowl seems to be tight for space. Just a heads-up on that.

[Mick W]

Re: BC12D Cowling Fairings for Screened Plugs.

Thanks , I'll double check !!.

[Hank Jarrett]

Re: BC12D Cowling Fairings for Screened Plugs.

Mine was too tight for only front cups too. There is something someplace that says your mags should match too (I can't find it right now) but my plane has UNSHIELDED mags top and bottom with shielded wires on the bottom to shielded plugs and unshielded plugs on top. Seems to work just fine with very little to no radio noise.

Hank

[Hank Jarrett]

Re: BC12D Cowling Fairings for Screened Plugs.

Mine was too tight for only front cups too. There is something someplace that says your mags should match too (I can't find it right now) but my plane has UNSHIELDED mags top and bottom with shielded wires on the bottom to shielded plugs and unshielded plugs on top. Seems to work just fine with very little to no radio noise.

Hank

[astjp2]

Re: BC12D Cowling Fairings for Screened Plugs.

It has to do with plug wear, when you rotate your plugs, some are neg to pos firing then the magnet is pos to neg as it rotates, that is why you do top to bottom rotation on plugs.

Mine was too tight for only front cups too. There is something someplace that says your mags should match too (I can't find it right now) but my plane has UNSHIELDED mags top and bottom with shielded wires on the bottom to shielded plugs and unshielded plugs on top. Seems to work just fine with very little to no radio noise.

Hank

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

It has to do with plug wear, when you rotate your plugs, some are neg to pos firing then the magnet is pos to neg as it rotates, that is why you do top to bottom rotation on plugs.

Which I cannot do as I am running shielded plugs on bottom and unshielded on top.

Tim, you taught me something just now. Is it worthwhile to move the top plugs around on top and bottom around on the bottom or just leave them where they are at if it isn't accomplishing anything?

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

deleted - had errors in it

[Guest]

Re: BC12D Cowling Fairings for Screened Plugs.

Which I cannot do as I am running shielded plugs on bottom and unshielded on top.

Tim, you taught me something just now. Is it worthwhile to move the top plugs around on top and bottom around on the bottom or just leave them where they are at if it isn't accomplishing anything?

My gut tells me that if you shift each plug to the next position in the firing order you will change its "polarity". Shifting them all ahead one or all behind one will have the effect you are looking for.

Caveat-its late I am tired and this is a shot from the hip reaction with little detailed analysis but I think it is correct. However I noticed that I always think I am correct when just before I find out I am wrong.

Dave

p.s. I was wrong, you don't have to shift them all in the same "direction" in the firing order but merely swap a plug with the a cylinder that it adjacent to it in the firing order as Gary's post (below) with TCM .pdf shows.

Firing order is 1-3-2-4.

Moving plug from 1 to either 3 or 4 will change it's polarity.
Moving plug from 2 to either 3 or 4 will change it's polarity.
Moving plug from 3 to either 1 or 2 will change it's polarity.
Moving plug from 4 to either 1 or 2 will change it's polarity.
Top or bottom will not make any diff to polarity if LH and RH mags are the same part number.

[PA1195]

Re: BC12D Cowling Fairings for Screened Plugs.

Here's what I've done for spark plug rotation in 4-cyl Continentals: http://www.tcmlink.com/pdf2/sil03-2c.pdf

Gary

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

I have seen the TCM bulletin before. Maybe I was not clear enough, all of my unshielded plugs are on top in Ercoupe cups, I cannot rotate them to the bottom. All of my shielded plugs are on the bottom, I cannot rotate them to the top.

I usually rotate the plugs around after I clean and gap them, top plugs stay on top just moved to another cylinder, bottom plugs same thing. Is this beneficial or should I just leave each plug in its respective location? Maybe I am missing something in the explanation you are giving. Thanks!

[N96337]

Re: BC12D Cowling Fairings for Screened Plugs.

It has to do with plug wear, when you rotate your plugs, some are neg to pos firing then the magnet is pos to neg as it rotates, that is why you do top to bottom rotation on plugs.

Exactly! A magneto is actually an AC generator in a sense...

[3Dreaming]

Re: BC12D Cowling Fairings for Screened Plugs.

Marty, one mag fires the tops and the other fires the bottoms. Since this is the case changing position in the cylinders for the top and bottom should work out OK. Just make sure to move them in a specific pattern like #1 to #2, #2 to #3, ect., and follow the same pattern everytime.

[M Towsley]

Re: BC12D Cowling Fairings for Screened Plugs.

Thanks, Tom. I understand which mags fire which set, just wasn't sure if I was accomplishing anything by rotating plugs the way I was doing it. I have a specific pattern I do each time. Thanks for the info!