Question about mechanics in Ms

[Blaidd_Drwgg]

As a first poster, hello to everybody!

I thought this would be the best forum for this, as Toms experience in winders is probably unsurpassed:

I am currently trying to build something like a MOOLY for M Leicas.
Do you (or anyone else) have a dataset of the accepted (maximum) and needed (minimum) torque and speed of the two-slotted winder coupling wheel? Is that different over different M models?
And does it always stop in the same position (camera or model-specific)?
Maybe there are even official specifications I could not find?

Also, the coupling on M4-2 (and later?) does 360°. How about the M2 spool?

I would like to try to make it universally compatible from the beginning.

With greetings, David

 

[Tom A]

David, both the M2 and M4-2 and later needs 360 degree "turn" to fully advance the film. I give my rapdiwnder about 370-375 degrees as a "just in case" setting. A worn camera usually requires a couple of degrees extra.
As for torque, I never bothered to measure it - but again it is also depending on the type of film used. Some manufacturers "crimp" the felt trap more than others - though the difference is not huge.
Reworking a MOOLY is possible, though quite complex - you need to make a housing that will fit and then make a spring assembly that will drive the whole thing. The original used a very long primary spring as well as a shorter secondary spring for this (and a counter weighed assembly ).
The double slot take up on a M2 indicate a M2M/Mot - same on the M4M/Mot. You can add the second slot of course - but it is not needed. You will also need a one-way clutch, otherwise you have to align the drive every time you load the camera. On the M4-2 and later you need the two prong coupling to engage the drive in the camera base. On both the M2 and the M4's - the coupling has to be spring loaded ( about 1.5 - 1.7 mm movement).
For years I had a MOOLY drive unit, serving as a paper weight, that I intended to make into a M2 MOOLY, but in the end I used it to fix a friends MOOLY instead. It is a fiercely complex piece and weighs almost as much as a M2 body!
Good luck with your project and let me know if I can be of any help.

 

[Blaidd_Drwgg]

Hey!
Thanks for all the tips! Some things I did not even think to think about yet. Two different springs, now that is interesting!
I guess i will try to get measurements from my body and hope they apply universally. They did establish tolerances and standards for some reason, right?

I am not sure if a clutch is necessary, if i use a ratchet (less than) the first half turn of spring movement is sacrified for settling the coupling. Or do I not see something here?

What I thought of was using mininum torque of the winding mechanism + smallest film tensile strength i can find * angular movement of sprocket drive[1] as maximum torque in my construction. Or am I forgetting something here (aside of a safety margin) ?

There is a pin near to the coupler in my M4-2. I have not seen that in photos of other models. Do they not have it? Is it of any use to a winder?

Also, what do you think about using brass vs. steel gears in a winder? Is brass really smoother? Every difference I felt in different (camera) bodies was probably skewed by age and used-ness[1].

That was a lot of questions, I hope have not pushed your helpfulness, and I am again very thankful for all the help I got!

[1] Maybe noone even noticed, but English is not my first language and that may lead to misunderstandings (not only, but especially) with technical terms. I want to apologize about that.

 

[Tom A]

It is a bit complicated to make a "body" for the winder as Leica used a fair bit if radi's in the M-body - it is which works fine. The is by no means straight forward. I recommend that you get a top -plate from on of the old M4-2 power winder and use that, rather than try to replicate a shell in metal.
The clutch is quite simple - Timken makes a one way clutch - smallest one is called a RC-02 (the height is 6,15mm and the bore 3,18mm. Works well to and far less complex tan having to make a ratchet mechanism.
The torque is not critical ( unless excessive) as the camera has a built in stop at the end of each frame.
The pin on the M4-2 was a control for the power winder and it is really not necessary and it was removed from subsequent models.
Brass or steel gears, either is fine, but brass tends to be smoother initially, steel gears takes quite a while to "settle in". Brass also has a built in safety factor - the gear gives out before the camera internal drive!