8mm Forum: Drive discs, 800 series.

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Posted by Martin Jones (Member # 1163) on November 19, 2009, 08:26 AM:

Anyone have any information on removing he drive discs from the rear half of the main drive shaft of 800 series Eumig machines?
While it is easy to remove the shaft assembly itself, I'm stuck after removing , in turn (starting at the rear end of the shaft) a cir-clip, plastic shim,bronze bearing, plastic shim, metal shim and take-up worm gear.
Careful inspection shows that the (apparently) 3-part disc drive assembly is held on by a thin plastic bush driven in flush with the rear end of this assembly, but there is no evidence of either any other fixing or of any locating stop which would prevent it moving forward along the shaft.
So can anyone confirm how it's fixed on...or how to get it off?

Martin.

Posted by John Pechulis (Member # 620) on November 19, 2009, 09:00 AM:

Hi Martin,

I think you'll find that the cast drive discs are pressed onto the bronze "boss" containing the grub screws. It would take considerable force (and a proper machine to avoid damage) to separate these as the the same type of force was used when pressing them together.

From experience, we've found you need to cut off what you don't want, leaving the bronze boss intact, or turn yourself a complete new drive wheel on a lathe. I chose the latter since I had trouble removing the whole assembly and butchered the original drive assembly.

John

Posted by Martin Jones (Member # 1163) on November 19, 2009, 09:17 AM:

So what you are saying, John, is that the brass piece in the centre is fixed to the shaft in the correct position with grub screws in the smaller diameter ends, and the discs are then pressed onto those ends, thus covering the fixing screws? Neat, but certainly providing a considerable removal problem! Would the brass boss then be removable?

While I'm, the subject of this machine, the other dis-assembly problem is related to the top sprocket. When removing the shutter/cam assembly in one piece from the machine, as far as I can see it is necessary to disconnect the top sprocket from the mechanism in some way. Any clues, anyone?

Martin

Posted by John Pechulis (Member # 620) on November 19, 2009, 09:43 AM:

quote:
So what you are saying, John, is that the brass piece in the centre is fixed to the shaft in the correct position with grub screws in the smaller diameter ends, and the discs are then pressed onto those ends, thus covering the fixing screws? Neat, but certainly providing a considerable removal problem! Would the brass boss then be removable?

No, what I'm saying is the cast drive wheels are a friction fit onto the brass boss. They are forcefully pressed together. There is no affixing hardware between the discs and boss. Only friction holds the three pieces together. And with dissimilar metals, you'll find many times these pieces seize together. The brass boss then anchors the assembly onto the shaft using the grub screws machined into the boss.

quote:
While I'm, the subject of this machine, the other dis-assembly problem is related to the top sprocket. When removing the shutter/cam assembly in one piece from the machine, as far as I can see it is necessary to disconnect the top sprocket from the mechanism in some way. Any clues, anyone?

Not sure what you're trying to accomplish with removing the entire shutter/cam assembly. Though I have experience with only the Mark 8, I would think the mechanisms between machines would be somewhat similar. When I removed the shutter blades, I simply loosened the affixing grub screws on the shutter blade boss and slid it off the shaft (obviously sfter removing the drive wheels, drive shaft and connecting plastic drive connection joint). I then cut all the blades off.

If you have something different in mind, let me know.

John

Posted by Martin Jones (Member # 1163) on November 19, 2009, 10:09 AM:

Thanks, John.
I'll keep it on this Forum as it is of interest to all seeking to effect repairs generally on this machine.
It would appear that the Mark 8, which was earlier, is different to the 800 series, since on the 800 series there are no grub screws visible at all, so they must be hidden under the aluminium bosses of the drive wheels that are force fitted over the brass.
On the other thing, I was wary of moving the shutter on the shaft to gain access to the claw mechanism cam, etc.for cleaning and re-lubrication, since I read somewhere that the shutter was an integral part of the cam mechanism, and I didn't want to cause any problems with springs, followers etc.! But if the shutter can be safely slid along the shaft and removed without problems (I can mark the boss and shaft to restore the correct rotational re-alignment if required), then great! Unless someone knows any different on the 8XX series!.
I don't want to dis-assemble more than is necessary, since the machine is in surprisingly good condition for its age, with most of the mechanism very free-running.

Thanks for the input, John. More on this later.

Martin

Posted by John Pechulis (Member # 620) on November 19, 2009, 11:17 AM:

I'd have to see a photo to be able understand what you're describing, since I'm only familiar with the Mark 8.

What is your intention with this machine? Are you just servicing the unit or modifying it?

John

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