Author Topic: Eisemann mag info  (Read 614 times)

Bill Poynter

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Eisemann mag info
« on: September 01, 2016, 10:40:12 AM »
I found the following on the National Aeronca Association Bulletin Board:

I finally got around to rebuilding a few Eisemann mags after many years not flying. Here's some tips for those folks looking at rebuilding or just getting a used mag installed - I luckily found an A&P willing to advise me after he stopped doing Eisemann rebuilds.

Changing mag rotation: If you have a mag for a C85 or so counter-clockwise that has all the same parts as the clockwise version (H27-709 (C85) and H27-711 (A65) for example), you can change the rotation easily. Here's how: open up the mag (5 screws - 3 in the case, 2 on the top plate where the wiring harness attaches). Take off the next mid-section plate you expose after pulling off the outer case (5 screws I believe). Take off the small pinion gear that attaches to the distributor (larger) gear. Slide off the Woodruff key that holds the cam and pinion / rotor together, and take the oval-shaped cam off. Flip the cam upside down (there will be slots facing toward you now that were hidden in counter-clockwise mode). Now rotate the distributor gear until you have the furthest left timing mark (there are 2 timing marks in the plastic gear about an inch apart, they look something like this -C and another mark is the reverse of that). You have to now align the little drilled (1/8"?) hole on the outside of the pinion gear with this mark. Now just put it back together and you'll be running clockwise (likewise, if you were converting an A65 mag to run on an C85 you just reverse these directions). Can't believe no one has ever posted this...

Winding an impulse spring: okay there are not Eisemann tools for this available anywhere, so you have to be a little creative here. I made a tool using a 6" 1/2" galvanized pipe fitting, a 1/2" T fitting for leverage, and a jigsaw. All you do is screw the 2 pipes together, then on the 6" piece, cut a notch with a metal jigsaw blade about 1/8"-1/4" wide so that the impulse spring center coil can slide in. Once it fits, push the outer part of the spring into the cup spring slot, then take the tool and rotate the inner spring coil until you can squeeze it into the starter cup. The direction to wind is opposite the mag rotation desired (i.e. A65 wind counter-clockwise). If it keeps slipping out, either use your hand to hold the spring end in the starter cup slot or put vice grips over it with a protective piece of copper or lead to avoid damaging the cup - be sure this piece of metal doesn't extend into the cup though otherwise you'll have to wind it even tighter to fit the spring in. Once you get the spring in the starter cup you can just align it with the flange (keep the paws inside) and wiggle it down into place on the rotor shaft. FYI new impulse springs are only $6 at Fresno Airparts.

And to convert an AM4 to an LA4 isn't very hard (i.e. unshielded to shielded mag conversion for radio interference)- you just need a few parts from a used LA4. Just swap the distributor cap, the rear case with cover, the small middle section with ground plug, and finally the "high tension terminal plate" H27-675 and you're good to go. Of course you'll need a shielded wiring harness as well (~$140 from Fresno Airparts built to your specs, unless you have a spare harness you want to convert over).

Another FYI most of the Eisemann parts in the AM4 and LA4 and even LA6 mags are the same... so if you're trying to get a mag working again you can basically buy any of them used and swap parts out. The parts manual I have saved to my computer I have no idea where I found it but if you email me I can send your way. The only thing that really changes between mags is the rotor size, impulse mag coupling assembly, and the distributor cap.

All I can say is that if you have Eisemann mags or want them, you CAN get them operational for not much $$$ knowing the above. I BTW have tons of spare parts for anyone looking to rebuild I can sell them much cheaper than what you'll find online since I don't actually need most of them... yet... -Matt


Bill Poynter

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Re: Eisemann mag info
« Reply #1 on: September 02, 2016, 09:00:27 PM »
I think the Franklin engines use Eisemann mags with right-hand rotation.  This should be the same as A65 Continentals.  That would mean an Eisemann mag from a C85-12 would need it's rotation reversed to install it on a Franklin.

The previous posting doesn't mention that the impulse coupling assemblies can't be reversed.