Author Topic: 1934 Model Z magneto drive.  (Read 1521 times)

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Offline Rispo

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1934 Model Z magneto drive.
« on: 23 Jan 2023 at 11:03 »
I am at present restoring a 1934 Douglas model Z 600. I am missing the magneto drive coupling piece. I would appreciate it if some one could send me a photo of what it looks like.
What I have made so far is very hard to get into correct alignment.
Regards John



Image converted to linked file to correct distorted display. Please see Taking photos with mobile/cell phone - Dave (Admin), 23Jan2023
« Last Edit: 23 Jan 2023 at 11:26 by Dave »

Offline Dave

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Re: 1934 Model Z magneto drive.
« Reply #1 on: 26 Jan 2023 at 02:13 »
Anyone able to help out here?

Offline eddie

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Re: 1934 Model Z magneto drive.
« Reply #2 on: 26 Jan 2023 at 09:13 »
I have never worked on a model Z engine but it is a development of the S/T6 engine, so I would expect most parts to be similar, if not the same.
   From your photo, the first thing that strikes me is that the spacers under the magneto look to be non standard. On the S6 they are headed pins with nothing protruding from the top (this makes it easier to align the magneto). Secondly, the drive from the stub shaft to the magneto is single sided on the S6 (having once got the timing correct, it is impossible to then time it up on the wrong cylinder). The drive dog that goes on the end of the magneto has just a single arm that locates in the slot in the stub shaft - the drive is taken on the solid side of the arm - the non-driving side is drilled for a ball and spring (which is trapped in the arm) - this prevents any backlash in the timing, and unnecessary rattles.
  If you have already assembled the engine without timing the magneto, you may need to remove the timing cover to re-mesh the gears to get the correct timing - this is simple - just slide out the idler between the mag and inlet cam, time the magneto and refit the idler. If you have to remove the timing cover, leave it loose until the engine is back in the frame with the primary chaincase fitted and the engine through studs fully tightened, then tighten the timing cover nuts. If the timing cover nuts are not left to last, you may end up with the valve gear not being correctly clamped in place, resulting in further engine damage.

  Hopefully, some of this will help,
                                                  Regards,
                                                                Eddie.

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #3 on: 27 Jan 2023 at 09:09 »
Thanks Dave and Eddie for your replies to my very first post.
I never new the magneto was mounted on stub shafts all I had was the imprints into the housing to go by. I have made a flat one piece mounting from 3mm aluminum for the magneto to sit on that shims can be added underneath. But the problem of miss alignment was still present when turning by hand. As yet i haven't assembled he engine or tried to time the magneto. I have discovered the taper on the magneto has .017thou wobble so this is going to be corrected before i attempt to check the alignment further. When i work out how to reduce photos i will post some more. Attached  is a photo of the drive dog i machined up to fit the slot in the drive.
Regards Rispo



Image converted to linked file to correct distorted display. Please see Taking photos with mobile/cell phone - Dave, 27Jan2023
« Last Edit: 27 Jan 2023 at 20:01 by Dave »

Offline Rispo

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1934 Model Z magneto drive.
« Reply #4 on: 27 Jan 2023 at 09:25 »
More photos

Offline eddie

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Re: 1934 Model Z magneto drive.
« Reply #5 on: 27 Jan 2023 at 11:39 »
Rispo,
          From your latest photo, I see your bike has a Lucas magdyno, whereas the S6 has a BTH magneto. However, this should not affect the way the unit is fitted. I have just taken the magneto off my S6, and got some photos of the drive (see attachments). The 4 headed pins that the mag sits on have a .750"dia head x .200" deep and a locating spigot .187"dia x .125" long. I guess the Z/Z1 models have the heavier duty drive because it is also driving the dynamo.
   Hope the photos are of some help,
                                                      Regards,
                                                                    Eddie.

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #6 on: 05 Feb 2023 at 11:52 »
Hi Eddie,
I have now found and corrected my alignment problem with magneto drive, my Magdyno had .020 thou bend in the front section of the armature. I gave my home made drive a little more clearance and now when tightened down can be turned freely by hand. My magneto housing is off an Enfield and has recesses underneath that have slight wear due to movement so making up mounting like your S6 was difficult to get the height correct on all four mounts so i made a plate and fitted shims underneath. I have attached photos of this.
Thanks for your help with this problem.
Rispo

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #7 on: 05 Feb 2023 at 12:04 »
Hopefully the photos.

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #8 on: 05 Feb 2023 at 12:12 »
Photos

Offline Dave

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Re: 1934 Model Z magneto drive.
« Reply #9 on: 06 Feb 2023 at 01:58 »
Rispo,

If the photos are proving hard to attach, please email them to the email address shown in "How to get in touch with Forum admin" and we will add them for you.

Dave
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Offline saluki42

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Re: 1934 Model Z magneto drive.
« Reply #10 on: 07 Feb 2023 at 11:01 »
I am so please to see all of this information, I'm also currently restoring a Model Z and have been trying to sort this for a couple of years now.
Which Lucas magneto are you using as my jigsaw kit of a Douglas came with an MN2 and I'm not sure if it is correct.

Regards
Chris

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #11 on: 07 Feb 2023 at 11:50 »
Hi Chris,
My magneto repair man looked it up and advised it was for an Enfield V Twin but would be suitable for use on the flat twin Douglas.  Numbers on the base are: MSH V -20  836   L2 * 464185. If a parts book had been made it would have helped me with my jigsaw.
Rispo

Online cardan

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Re: 1934 Model Z magneto drive.
« Reply #12 on: 08 Feb 2023 at 05:53 »
My magneto repair man looked it up and advised it was for an Enfield V Twin but would be suitable for use on the flat twin Douglas. 

Hi Rispo,

Your magneto man is probably right, but it might be worth double checking. Early V-twin magnetos did very fancy things with their armatures and pole pieces to get a roughly even intensity spark for each cylinder - it's tricky because for a 50-degree V-twin you need sparks every 155-205-155-205-... degrees rather than even firing for a single or flat/parallel twin. My magneto bible (Young & Griffiths, 5th edition 1955) has three pages of discussion about magnetos for V-twins, but makes the point that "higher grade magnet steels together with improvements in magnet designs have permitted the use of a less complex design..." Your mag-dyno is from 1936, nearly 20 years before the book was written, so I'm not sure what design has gone into it. It would be a pity to get the V-twin magneto all done up and converted to 180 degrees only to find one dodgy spark.

Cheers

Leon

Offline saluki42

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Re: 1934 Model Z magneto drive.
« Reply #13 on: 08 Feb 2023 at 11:15 »
Thanks Rispo, I was wondering if the Douglas ignition is like other old Brit Twins which fire both cylinder every stroke, both ignition and exhaust. If that is the case then you wouldn't need to worry about getting the magneto drive 180 degrees out hence the through slot and not the one sided one on earlier models.

Oh and as a Z owner I dream of parts manuals and anything other than snatched photos to work from, A Z was auctioned a number of years ago and I managed to download all of the presale pictures which are helping.

Chris

Offline Rispo

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Re: 1934 Model Z magneto drive.
« Reply #14 on: 09 Feb 2023 at 11:02 »
Hi Leon,
Thanks for your thoughts on my magneto but I have already had it fully overhauled with coil rewound and condenser replaced. I am aware internal adjustments have been done to the cam ring. New slip ring and bearings were also fitted then its been run on the test bench. As to spark quality I have left that up to the repair man. I will have to wait until I get it running in the coming months.
Rispo