Sliding feed clutch and jamming gearbox....

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YouraT
Posts: 34
Joined: Sun 22 Apr , 2012 19:38 pm

Sliding feed clutch and jamming gearbox....

Post by YouraT » Wed 21 Sep , 2016 22:48 pm

Hi all.

Quick question / brain picking about the dog clutch on the sliding feed shaft.

I've been using my (metric) 250 for a bit now, and it's been behaving well, especially once I got the belt tensions set up properly.

After the sliding feed and the dog clutch working fine for a while, it has suddenly developed an irritating fault - when the clutch re-engages after automatically dis-engaging, the gearbox jams solid.....

If I re-engage the lead screw and turn by hand for a bit, all is again well.

Having opened it up, everything I can see appears in good order, no excessive wear (or indeed any at all) on the visible gears - the oil drained out quite clear (although a little dark from being I suspect many years old), but the auto-disengage dog clutch is behind all the other shafts, and I can't see it. Fiddling with all the other gear combinations persuades me that's it's something to do with the rear-most shaft where the sliding drive shaft comes in.

I've found the gearbox drawings in the stickies at the top of the forum (section D-D is the area of interest), but nothing obvious springs to mind as to what might have gone wrong - I'm planning now on a complete tear-down to get at the offending area and see what's what, but wondered if this is a fault anyone else has seen on their gearbox, and if any pointers could be had?

Thanks,

Youra.

YouraT
Posts: 34
Joined: Sun 22 Apr , 2012 19:38 pm

Re: Sliding feed clutch and jamming gearbox....

Post by YouraT » Fri 23 Sep , 2016 22:47 pm

OK - so some progress - what's happened is now clear, although why is perhaps less so...

The circlip (see picture) just to the right of the dog-sooth clutch gear has come out of its groove, allowing the gear to move to the right, and thus the mating teeth of the gear directly above it to fall into the hole and jam the whole thing up.

The circlip when pushed back into its groove is rather slack, and will fall out again. No idea how it came to be like this.

Ideally, I'd take the whole shaft out, replace the circlip (type called up on the gearbox GA drawing) and that would be that.

Unfortunately I cant do that without removing the taper pin that holds the other half of the dog clutch onto the shaft, and I don't think I can do that without taking the gearbox off the machine - I'd *very* much rather not do that.

So - I'm thinking that instead of a circlip I could perhaps use an appropriately sized (3/4" or 19.1mm) E-Clip, which can be pushed onto the shaft from the side without taking the shaft out, and either leave the old circlip out of the way on the shaft (it will do no harm) or break it off.

Or is there a way to remove the shaft without taking out that taper pin? Conversation here:

viewtopic.php?f=50&t=5152

suggests perhaps not...

Any reason not to use an E-Clip rather than the specified Standard external circlip ?

Thanks,

Youra.
Attachments
Circlip out.jpg
Circlip out.jpg (861.08 KiB) Viewed 4905 times

Pete.
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Posts: 283
Joined: Wed 07 Jan , 2009 9:46 am
Location: Kent, U.K.

Re: Sliding feed clutch and jamming gearbox....

Post by Pete. » Sat 24 Sep , 2016 12:03 pm

You can't remove the shaft without drifting out the taper pin but you CAN get the pin out in place. You do have to be a bit careful with it though.

Turn the shaft until you are viewing the narrow end of the pin. Drift it a tiny bit with a pin punch, you might want to bend a bit of metal and put it behind to stop you drifting it too far so that it binds on the casting. Once you have it moving turn the shaft so the pin is vertical then use a bent bit of rod as a drift to tap it out the rest of the way upwards. If you get it very loose you might be able to turn the shaft and pull it out with pliers.

Before you re-assemble the shaft, fit it up on the bench and mark the collar and shaft with permanent marker so it's easy to align the tapered hole once it's in place so you don't try to drift the pin in with the shaft 180 out.

YouraT
Posts: 34
Joined: Sun 22 Apr , 2012 19:38 pm

Re: Sliding feed clutch and jamming gearbox....

Post by YouraT » Sun 25 Sep , 2016 23:17 pm

So.

Emboldened by Pete's comments (thanks!) I can report complete success :D

The taper pin came out very easily - it's barely worth marking it up for replacement - on this shaft at least it's way off centre and can really only go in one way.

New circlip purchased and fitted, and all back together easily - I can see why it's been designed this way rather than using a shoulder - you can't get the clip ring on the other side without moving the geared half of the dog clutch a little further up the shaft.

Cleaning out the bottom of the gearbox also revealed the roller section and one of the thrust washers of the thrust bearing that's meant to sit between the other half of the clutch and the spring - this machine I think has clearly been messed with previously....

Back in its correct location after a little solvent bath.
Back_together.jpg
Back_together.jpg (535.2 KiB) Viewed 4893 times
Getting the gear selection lever back on the correct location I found easier than others have suggested - on this machine at least, the quadrant doesn't fall down low enought to come out of mesh, and there is an assembly alignment mark on the pinion and quadrant gear to show how to align those before closing the front of the box up again.
Marked gears.jpg
Marked gears.jpg (621.9 KiB) Viewed 4893 times
It was then a simple(ish) matter of ensuring that I didn't move the gear knob away from the '1' position so I couldn't push the pinion back into the gearbox, and getting the mesh right there, and then tightening the whole thing back up.

Gearbox now sealed and full of ISO32 oil, and having tried every ratio, including a few auto-knock-offs of the clutch, it's all working just fine.

All in all, rather satisfied with the outcome :-)

Pete.
CNC Expert
CNC Expert
Posts: 283
Joined: Wed 07 Jan , 2009 9:46 am
Location: Kent, U.K.

Re: Sliding feed clutch and jamming gearbox....

Post by Pete. » Mon 26 Sep , 2016 0:00 am

Good news!

Thanks for posting the follow-up, it might help someone in the future.

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