1934 Model Z oil feed and return pipe sizes

[saluki42]

Hi I've finally reached the point where I can think about sorting out oil pipes for my project bike, however I'm a bit confused about the diameters I should use. The oil pump feed and return couplings, as far as I know original, have a bore diameter of approximately 7/32" (5.55mm) which seems very small to take cold viscous oil down to the pump and provide adequate scavenging for the return. Does anybody know what sizes I should expect to use for the pipes or is this 7/32" about right/

Any advice on this rather crucial matter would be gratefully appreciated.

Regards
Chris

[Doug]

My 1934 & '35 OW1s would be a contemporary to the Wessex/Z-ed models, and use a 5/16 inch copper tube that is probably 1/4 inch inner diameter (they are a fairly long run from the petrol tank to the base of the engine). Where it passes through the oil fittings the passage is only 3/6 inch diameter in the banjo fittings and even smaller through the union fittings at 5/32 inch.

In 1936-38 the Aero models were using a 1/4 inch copper tube of 20 SWG wall, for and inner diameter of 0.178 inch. Factory drawings show union fittings with the 7/32 inch through hole, so - yes - that is what they were using.

You were expected to run different viscosity oil in summer vs. winter.

-Doug

[saluki42]

Thanks for that Doug, that has confirmed my first thoughts. I'll bear the oil swap in mind when I finally try to get her running.

Whilst you are on a quick question, have you got anything on the dynamo drive 'adaptor' that was used to connect the tapered shaft of the Lucas dynamo to the slotted output shaft from the gear train. So far my research hasn't turned up anything and my attempts at machining something to try have not been successful.

Regards
Chris

[Doug]

Chris,

Not sure I follow your question. The Lucas magdyno was an integrated unit. the dynamo pinion was affixed directly to the dynamo shaft and driven by a fiber gear, via a slip clutch, off the magneto armature shaft.



-Doug

[saluki42]

Sorry Doug that was me being rather stupid. The slotted drive from the engine gear train connects via some drive adaptor to the tapered input shaft of the magneto which extends beyond end plate as shown in the attachment. Its details of this drive adaptor I need so that I can machine.

Chris


[reformat picture. 15Nov23. Doug, admin]

[Doug]

Chris,

I have not seen that part specifically for the Z-ed models. I know it changed from that used on the S6 from which it derived, but I have only seen a good picture of the socket it plugs into in the back of the magneto drive gear. Not the coupling or hub on the magneto shaft when separated. I presume it is a double tang version of the S6. What - if any - provision is made to prevent assembling with the timing 180 degrees out of position, I do not know.

-Doug

[saluki42]

Hi gain Doug, as far as I can't see from this how this problem with the timing could be avoided so was assuming it was like a lot of early BSAs and Triumphs where they spark on each stroke compression and exhaust.
Chris

[eddie]

I have (in the dim, distant past) seen one of these couplings. As Doug says - the S6 version was much smaller, and only had the one tang to drive it. The later version was of heavier construction, and had the 2 tangs - probably because it now also had to drive a dynamo. The easiest way of preventing the timing from being assembled ½ a turn out would be to make the 2 tangs (along with the slots they fit in) of differing widths. On the S6, the drive tang had a spring loaded ball in one of the faces - to eliminate any backlash (and, presumably, subsequent rattle).

  Hope this helps,
                          Regards,
                                        Eddie.

[saluki42]

Thanks Eddie, good idea regarding tang and slot sizes although a previous owner has already widened the slots for some reason, ill have to have a look and see what I can do. Other than than it look like time in the machine shop and some experimentation coming up.

Thanks again
Chris

[yosemite]

Dont know how relevant or even if it is relevant ,but. Panthers had a magneto drive with two tangs to connect to engine, could one of these be modified, may save a lot of time trying to get taper machined accurately,

[saluki42]

Thanks Yosemite I'll definitely follow that up and let you know how I got on.
Chris

[eddie]

Chris,
          Referring back to the photo you posted of your magdyno - that is a magdyno for the later mark series machines. The original magdyno for the prewar machines had a thinner front cover and no side lugs for bolting up to the timing chest. There doesn't seem to be many detailed photos of prewar Douglas magdynos, but I would assume they were basically the same for 'Blue Chief', 'Wessex', 'Powerflow', 'Speed Special' and 'Endeavour' models - just the 'Powerflow' and 'Wessex' models were listed as having a 'quickly removable' magdyno - so the drive is probably peculiar to those 2 models! I have, however, managed to find an illustration of the magdyno on an 'Endeavour' and it shows a very thin front cover with a deep extension to house the drive. I remember a few years back, an LDMCC member had the same problem with a mag for a 'Speed Special' - he turned up the extension and had it laser welded to a standard Lucas MO1 magneto front cover - that turned out very successful, as the laser welding didn't cause any distortion.

  Regards,
                Eddie.

[saluki42]

Hi again Eddie and again thanks for the details. The problem I now face is getting hold of one of these un name mag dyno units. The bike I am modelling my project on was one sold at auction a number of years ago which I am really having to use as a pattern. As you can see from the attached picture it is fitted with either a MN2 or ML2 Lucas unit. I will keep looking for the correct one but until then I think I am best to go along with my original plan which is to use my magneto and manufacture a drive couple the fit both mag shaft and engine output shaft.

Wish me luck

Chris

[EW-Ron]

What - if any - provision is made to prevent assembling with the timing 180 degrees out of position, I do not know.

In that case, all you need to do is swap the plug leads over, and all will be good again.
Same as for a K2F on yer average triumph norton bsa amc parallel twin.

The magneto spins at half engine speed, so 2 sparks (per magneto rev) is about all it can produce.
And all it needs.

A Scott, with 2 sparks per engine rev is stretching it, electrically.... ?
(magneto runs at engine speed)

[saluki42]

Good idea, and if swapping the leads proves the point then being a quick detach magneto slide it back, rotate the magneto 180 degrees, slide it back and clamp it and the leads can be put back to normal.

[Doug]

This is the magdyno for an Endeavour. Or at least what came with my Endeavour project. Presumably the 1035 code on the base means Oct-1935.







Interestingly, there are two different end covers. Slightly different in style, but functionally interchangeable. The housing for the modern lip seal is an addition by the previous owner.





I can confirm that the Endeavour (and by association Blue Chief) and the OW/OW1/Speed Specials crankcases do not have provision for the magneto quick-coupling. The Wessex/Powerflow/Z/Z1 were the last crankcase iteration of the S6, and presuambly keep that feature as a legacy. For the Endeavour/Blue Chief and the Speed Specials there were new crankcase designs and they chose to forgo the quick coupling.

Unfortunately this is the only period correct magdyno I have. The 1934 OW1 has a later prewar magdyno and the 1935 OW1 has a seldom seen (but incorrect) BTH dyno-mag. The second Endovour project is sans-magdyno.

-Doug

[cardan]

No idea if this is relevant, but here's a pic of a 1931 BTH magneto driven by a 2-prong drive dog. Pretty sure the whole setup (height boost from mounting plate + drive dog) is Panther, as mentioned above.

Leon

[Ian Hand]

I have posted a couple of photographs that might help you with the Magneto drive.  The rectangular drive piece is quite a loose fit in the slot. There is a ball bearing with a spring in a hole on opposite sides of the block to absorb the shock.  The balls protrude about 2mm and when the block is fitted into the slot you can feel the balls being press against the springs.  It's an interference fit. It's hard to describe without a picture. I made a temporary drive block which fitted a little more snugly into the slot just to use on the test bench. I fitted the original on when I assembled the bike.  I will see if I can locate any other photographs.
The ring shown in one photo is an aluminium ring with an O ring groove on each face to seal between the engine casing and the magneto.

  I hope this helps.






Aspect ratio fixed and attachments converted to linked files - Dave, 14April2024

[saluki42]

Thanks for that, every little piece of information I get is a help. I've machined a rectangular block with tapered bore and keyway and just fine tuning it now hopefully this will come to something.

Regards
Chris

[saluki42]

Just fitted and tried the latest version of the steel block drive and am pleased to say, with the mag clamped down it rotated freely and in the right direction A/C. now I know it works its time to repeat it with a high grade bronze replacement and fit the ball and spring shock absorber.

Chris

[cardan]

The rectangular drive piece is quite a loose fit in the slot. There is a ball bearing with a spring in a hole on opposite sides of the block to absorb the shock.  The balls protrude about 2mm and when the block is fitted into the slot you can feel the balls being press against the springs.

Hi Ian and Chris,

Before Chris makes his final version of the the drive block, it might be good to clarify the role of the balls and springs.

My best guess is that they go on the non-drive-side of the block, and that their role is not so much as a shock absorber, but just to keep things quiet on the overrun. That way when the mag is being drive the timing is what it is, and on the overrun when the backlash is taken up by the ball and spring the small change in the timing doesn't have any effect. If the balls were on the drive side the timing could vary a bit.

Anyway, worth being sure before the final version is made.

Cheers

Leon

[eddie]

That is certainly the case with the S6 - the ball and spring are on the non-drive side of the  block.

  Eddie.

[saluki42]

Hi Eddie, sorry about the delay in replying but life went on hold for a bit. Now recovering from open heart surgery, all seems to have gone well but because of what with what they had to do to gain access to the heart lifting a pint of beer will be my limit for a few months. Hopefully I'll be at the UK owners club rally but all of the keys to my garage have been locked away from me.
Anyway thanks for the info on this infernal drive unit.

Chris