Restoration of a Bosch ZEV magneto

[BoschZEV]

have an open condition from both A and B to the slip ring. Between A and B I have .6 ohm.

If I understand your labeling correctly, A and B are on opposite sides of the condenser. If so, and if the condenser is good, the reading should be ~0.6 Ohms because you're making the measurement between the lead that comes from the coil and the housing, i.e. through the primary coil. So ~0.6 Ohms is what it should be.

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?

One side of the condenser is connected to the housing, while the other side connects through the primary back to the housing (~0.6 Ohms) as well as through the primary and the secondary to the slip ring (i.e. it's ~0.6 Ohms + ~4 KOhms = ~4 kOhms because the 0.6 Ohms is a negligible addition to the total resistance unless you're using a 6-digit ohmmeter).

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?

Yes, you have to un-solder the lead the connects the condenser to the coil. It's OK to unsolder the other lead as well.

How is the winding connected to the slip ring? If I were to pull the slip ring, will I find the wire soldered?

This wire is not soldered. The wire exiting the secondary is a slip fit in the slip ring. Since it will be at several kV when the coil "fires" the small gap is inconsequential. However, depending on how the wire is in that hole it may or may not be physically touching the metal of the slip ring (or it may be oxidized) so even with a good coil you still could get an infinite reading between the coil lead attached to the condenser and the outer surface of the slip ring. Once you remove the slip ring the wire will be exposed and you can make the necessary measurements. Once you have the end cap and the slip ring removed, and the coil is free standing, the resistance between the two wires at the condenser end of the coil will be ~0.6 Ohms, and between either of them and the exposed wire at the other end will be several kOhms.

Just to be clear, I've written 0.6 Ohms above but it might be anywhere within a factor of two of that depending on how Bosch made it back in the Dark Ages. Similarly, anything in the range ~3-8 kOhms is probably fine. However, coils that pass DC ohmmeter tests can still fail dynamic tests so your measurements can still give false positives for coils that will fail in operation.

[DanM]

Well, it took me a bit to get back. I made up this puller adapter to remove the inner bearing races, when the split washer is installed, and the slip ring when they are removed. I used a 2 jaw puller to remove the parts from the shaft.P1060395.jpgP1060397.jpgP1060398.jpgP1060399.jpg

[DanM]

Then I got the end cap off the armature assembly, and removed the part containing the capacitor. Now to remove the cap and replace with my Vishay caps. Questions- is that the cap, the silver area between the brass? Do I remove the rivets and pull off the brass to expose the original caps? And then fit the new caps in that space? I assume I need to retain as much material as possible and the stub that goes through the end cap and takes the screw for the points mechanism. Thanks again for all your support!
P1060390.jpgP1060391.jpgP1060392.jpgP1060393.jpgP1060394.jpg

[Shaky Jake]

Well, it took me a bit to get back. I made up this puller adapter to remove the inner bearing races, when the split washer is installed, and the slip ring when they are removed. I used a 2 jaw puller to remove the parts from the shaft.[ATTACH=CONFIG]19277[/ATTACH][ATTACH=CONFIG]19278[/ATTACH][ATTACH=CONFIG]19279[/ATTACH][ATTACH=CONFIG]19280[/ATTACH]

Nice job!

Kevin
.

[BoschZEV]

Questions- is that the cap, the silver area between the brass? Do I remove the rivets and pull off the brass to expose the original caps? And then fit the new caps in that space?

The entire assembly in your photos is the capacitor. A large number of thick mica plates are separated by very thin metal "plates," alternate ones electrically connected to one brass piece and the other set of alternate ones to the other. One brass piece (and half the metal plates) is connected to the threaded stub so you'll need to recycle that stub by connecting one electrode of the modern, replacement capacitor to it. The other electrode of the modern capacitor goes to the appropriate wire of the coil.

I hope the above is clear. I'm unbelievably jet-lagged at the moment so I wouldn't be surprised if I re-read it tomorrow and say "huh?" to my instructions. if it's not clear don't hesitate to say so.

[DanM]

It makes sense. Plus I went back to the brit bike article and found a couple of pictures of how you did this in another end cap. Thank you again.

[DanM]

Here's where I'm at. Joined the 2 caps in parallel with brass shim. One is formed into a foot to be soldered to the plate which is connected to the points mount screw. The other leg goes to the housing screw. I soldered two wires to come out of the potting to connect to the winding.20170318_111901.jpg5

[DanM]

20170320_205019.jpg
Added a pix with the wires.

[BoschZEV]

Dan,

I can't tell from the photos if you soldered the capacitor leads to the brass shims. If not, you need to do that and not rely on just having the brass wrapped around them to make reliable electrical contact. Also, I recommend you use magnet wire (i.e. copper with a very thin coating of insulation) rather than your present wires. The armature spins pretty fast so the centripetal force on the wires will be large. The more massive the wires are (and they're pretty massive now), the more force they will experience. Magnet wire of 20 or 22 AWG is what I suggest (I use 20 AWG).

[DanM]

The leads are soldered to the brass. I do have .028" or 21 gage solid varnished wire and will replace the stranded. Thanks again!

[BoschZEV]

Photobucket's change in policy last month has left my magneto thread (http://www.britbike.com/forums/ubbth...733#Post446733) without images. I had hoped they might reverse their policy, but when that didn't happen after a few weeks I started looking into other solutions. I have all the text and images organized on my computer, but simply relinking/reloading all those photos would take a lot of time. I don't want to just move to a different photo hosting site since the same thing easily might happen again.

Given the number of views it has received here and on the BritBike forum I can tell that people find this magneto information useful. However, I've been busy preparing my 1928 Ariel for next year's Cannonball so I haven't spent a great deal of time looking for a "permanent" solution to the problem of images. Once I do find a good solution I'll get the thread fleshed out with photographs again.

[T. Cotten]

BoschZEV!

Merely uploading them directly to this forum in the first place works, for free,... but indefinitely.

(Meaning: I can't kill a pic that should be.... so think twice before posting!)

....Cotten

[BoschZEV]

Merely uploading them directly to this forum in the first place works

Not in the way that works for me. The posts that have large images embedded where they should be in relation to the text that refers to them are on third-party hosting sites, like Photobucket used to be. Thumbnails lined up much less usefully across the bottom are ones that were uploaded directly to the forum.

[T. Cotten]

Not in the way that works for me. The posts that have large images embedded where they should be in relation to the text that refers to them are on third-party hosting sites, like Photobucket used to be. Thumbnails lined up much less usefully across the bottom are ones that were uploaded directly to the forum.

Got no third party here, BoschZEV!

Sounds like you have a headache for the moderator,

....Cotten
PS: I would certainly like to know how to insert the pics into the text in order, as well as edit old uploads.

[TechNoir]

Hello BoschZEV. I have exactly the same issue as yourself both on this forum and other forums. I have worked out where I am going to host my photos but I cant edit the links in old threads.

I have asked Admin a couple of times (in my thread here http://www.antiquemotorcycle.org/bbo...s-Alternatives) if there is any way I can edit the old posts but they have not responded.

I will be interested if you can get to the bottom of this one as I want to update my photo links too.

John