Restoration of a Bosch ZEV magneto

[BoschZEV]

I have been following one or two of your other posts about magneto's with interest...

Thank you very much for your reply. Although I know the threads get a lot of hits, it takes quite a while to write those posts so it's always gratifying to hear from people who find them useful.

p.s. FYI, the Magdyno I refurbished is for a friend's BSA ZB34 500cc single. It's a bitza, with a late 1940s ZB34 engine in a War Department M20 frame.

[BoschZEV]

Interest in magnetos is heating up as the start of the Cannonball looms just a month from now. I hope it doesn't portend bad things to come but I was contacted by three entrants over the past week hoping for help/advice on their magnetos. I suppose something has to be left until the last minute, but the magneto is a pretty critical item to put off until now. Unfortunately, although these three are in panic mode, and much as I would like to help them, I'm dealing with deadlines of my own so I can't drop everything at the moment to address their problems. In contrast, Shaky Jake first contacted me a year ago for help with an appropriate condenser, and again three months ago to test his coils, so I hope his foresight means everything will go well for him. Like most of you I'll be closely following the daily Cannonball updates.

[T. Cotten]

Interest in magnetos is heating up as the start of the Cannonball looms just a month from now. I hope it doesn't portend bad things to come but I was contacted by three entrants over the past week hoping for help/advice on their magnetos. I suppose something has to be left until the last minute, but the magneto is a pretty critical item to put off until now. Unfortunately, although these three are in panic mode, and much as I would like to help them, I'm dealing with deadlines of my own so I can't drop everything at the moment to address their problems. In contrast, Shaky Jake first contacted me a year ago for help with an appropriate condenser, and again three months ago to test his coils, so I hope his foresight means everything will go well for him. Like most of you I'll be closely following the daily Cannonball updates.

That's exactly why I stopped taking in C-ball request HX Scheblers after Davenport last year.

Damn glad I did.

....Cotten

[BoschZEV]

Earlier this spring I stress-tested coils (http://www.antiquemotorcycle.org/bbo...585#post155585) for a Dixie magneto and a spare as a favor for Kevin Naser (Shaky Jake) who was rebuilding a 1916 Indian to ride in the next Cannonball cross-country rally. As well as testing his coils I also gave him two pairs of "my" condensers (http://www.britbike.com/forums/ubbth...762#Post508762) to use in these magnetos.

The 2016 Cannonball is now finished and Kevin was one of only 16 riders out of a starting field of 92 who achieved a perfect score in the 3306-mile, 16-day rally. He covered every mile, and did so within the allotted time every day. He even rode an additional half-day in pouring rain that the organizers allowed participants to skip without penalty. As Kevin's experience shows, a magneto -- even one 100 years old -- that is rebuilt using the proper components will take a licking and keep on ticking.

[BoschZEV]

Update: I just learned that Kevin never finished restoring the Dixie magnetos and instead used a restored Bosch ZEV to complete all the miles. However, irrespective of which magneto he used, the lesson is that a properly rebuilt century-old magneto has all the reliability anyone could wish for.

[exeric]

BoschZEV; can a Dixie be (reasonably) rebuilt into a trustworthy magneto? I guess what I'm asking is; are there inherent design problems with a Dixie, compared to a Bosch?

[BoschZEV]

are there inherent design problems with a Dixie, compared to a Bosch?

Instead of spinning a coil of wire in a stationary magnetic field the Dixie basically spins the magnetic field in a stationary coil of wire. I don't have one to measure but I believe the rotating part of a Dixie is heavier than the rotating armature of a Bosch. Irrespective of its total weight, since that rotating part is asymmetric it is more likely not to be perfectly balanced. That will result in vibration which will be hard on the bearings. However, it would be straightforward to balance the armature to eliminate this as a problem. Other than that one issue to pay attention to, there's no reason a Dixie shouldn't be as reliable as a Bosch ZEV.

[exeric]

Thanks, BoschZEV. I'm a bit surprised that American magneto manufacturers didn't just rip-off the Bosch design during WW1; but I guess everyone saw the handwriting on the wall that generators, circuit breakers, and distributors would be the coming thing, and magnetos would be taking a back seat. Most every motorcycle magneto I've looked at, looks very well built, with precision made parts, and beautifully finished. But, I guess Bosch was the cream that rose to the top.

[BoschZEV]

I'm a bit surprised that American magneto manufacturers didn't just rip-off the Bosch design during WW1;

Basically they did. Without taking time to remind myself of the details, the U.S. government seized the assets at the start of WWI and sold them to American insiders for pennies. Slowly over the 20 years after the war ended the German company bought back the assets, only to have them seized again when WWII started

[MMasa]

Eric
The Dixie design has some advantages over the Bosch design as well. These have to do with the advance/retard function.
In a magneto, there is an optimal moment for the points to open for maximum spark. This occurs at the time when the stator and armature poles are breaking their magnetic relation to each other and the magnetic field is about to collapse.
When you advance or retard a Bosch magneto, you are causing the points to open slightly before or after this optimal moment.
The Dixie is designed in a way that this pole relationship remains fixed as the magneto is advanced or retarded. The "guts" of the magneto actually rotate inside of the shell of the unit to effect the timing.
It seems to me that the weak link on a Dixie is the pot metal base.
Mark

[Shaky Jake]

Instead of spinning a coil of wire in a stationary magnetic field the Dixie basically spins the magnetic field in a stationary coil of wire. I don't have one to measure but I believe the rotating part of a Dixie is heavier than the rotating armature of a Bosch. Irrespective of its total weight, since that rotating part is asymmetric it is more likely not to be perfectly balanced. That will result in vibration which will be hard on the bearings. However, it would be straightforward to balance the armature to eliminate this as a problem. Other than that one issue to pay attention to, there's no reason a Dixie shouldn't be as reliable as a Bosch ZEV.

Based on my precise scientific method and ultra-sensitive measuring and test equipment (a.k.a. my fingers) the Dixie rotor does seem to have a bit of a dynamic imbalance. See the attached video. Of course, as long as the bearings and their support structure are designed to handle the resulting loads, this doesn't necessarily result in a reliability issue.






Kevin


.

[BoschZEV]

) the Dixie rotor does seem to have a bit of a dynamic imbalance. See the attached video.

Well, that video certainly explains your screen name. Either you had way too much coffee before making the video, or that magneto is a candidate for balancing. Just doing a simple static balance on a good set of rollers should make a big improvement, although the asymmetry means there will be a rocking couple that only could be dealt with by a dynamic balance. Still, that secondary source of vibration should be considerably less than the primary.

[whp]

BoschZEV.

From knowing nothing about Magnetos to buying a ZEV for my J and taking it apart to diagnose condition I must thank you on your write up! I'm sure you've heard it a thousand times but the technical information presented about the ZEV is unmatched! I've probably spent about 10 hours pouring over every detail of my magneto in order to bring it into proper working order. I did run into a little trouble with how the brass insert where the earth brush rides comes out of the plate. After some... mistakes were made... I realized that it is threaded in after the fact. The oiler on the plate has a brass piece that acts as a stake to keep everything aligned and I did not know this when trying to take the piece out. The reason for disassembly was the earth plate was pulling away from the aluminum plate, and was wearing on the earth brush quite bad. I did manage to wrangle to back in correctly and is now in working condition!

I didn't quite understand the importance of re-magnetization until I had it done, I used to turn my armature about to do points adjustments decently fast and now I shock the sense right out of me.

I'd like to find the proper equipment such as your testers, I quite like this stuff but it's real tough to acquire!

[BoschZEV]

...the technical information presented about the ZEV is unmatched!

Thanks very much for the kind words. I always like to hear when my efforts have helped someone with their magneto, although I do know the information is of interest from the number of views this thread gets. Thanks again.

[DanM]

Dear Mr. BoschZEV:

I am working on my first mag, a Bosch ZE1. ZE1 Armature A.jpgZE1 Armature B.jpg
I really appreciate your articles as guidance to the process of investigation and remediation.
My question is on measuring the coil in the armature. I have used an ohm meter between the solder joints in the capacitor end cap and the slip ring and have an open condition from both A and B to the slip ring. Between A and B I have .6 ohm.
It is not clear to me the winding connections and whether I should have resistance between A or B and the slip ring. I assume so.
Can you advise?
I also ask for clarification regarding removal of the end cap. Looks like I should un-solder the wires from the end cap connections prior to removing the end cap?
How is the winding connected to the slip ring? If I were to pull the slip ring, will I find the wire soldered?
Thanks in advance for your valuable time.
Dan