Super 7 clutch not working

Steve,

You probably need to tell us which model Super 7 you have and a picture of the clutch lever would probably help. If it is the Mk 1 with the one bearing inside the long lever and two screws which bear onto that bearing then you might well have to take the whole clutch assembly out and take it apart. When mine slips, it tends to not drive, rather than engage the drive permanently.

If you look carefully at the largest pulley there is a hole in it (in the valley where the belt sits) around 8mm dia. You need to turn it by hand (with the power off and disconnected) and find the corresponding hole in the boss beneath. This allows access to the screw which adjusts the clutch. There may be 2 screws in the hole, one to lock the deepest one in. You'll have to fiddle to find whether that gets you any adjustment of the clutch. In the Mk1, the clutch is like a 2" diameter circlip, about an inch thick, and moving the lever forces the legs of the circlip apart so that it engages with the inner bore of the pulley.

The whole thing is relatively simple and comes apart with some persuasion. There are no nasty great springs inside it. HOWEVER, be aware that the later models do have a ruddy great spring inside and shouldn't be taken apart without appropriate precautions.

Make sure you read up (online) on what to do for your particular model of clutch.

Regards Tom

Edited By Tomfilery on 22/11/2017 17:00:46

The ball may be missing if it is the Mk2 clutch. There should be a ball bearing between the push rod and the shaft, also a small anti rattle ball in the end of the pushrod. The drawings of both types are easy to find with a Google search.

Mike

It's an early one by the sound of it. I'll send some pics tomorrow.

Steve

If you think it's a Mk1, I've put these on for info:

Steve, as Tom states they are fairly straightforward devices but I will admit to being puzzled that your drive is permanently 'engaged' - I'd kind of expect most problems to result in non-engagement. So I think you will have to dissemble the clutch.

The main reason I'm posting is to warn you that the clutch shaft only comes out in one direction and that you will damage the bearings if you try to force it the other way. Sorry a long time since I've done this - so I am not going to state which way that is, just I case my memory is not so good - you need to read the manual (used to be available on the Yahoo Myfords site). I don't have my copy to hand I'm afraid but I'm sure someone else here can be more definitive.

Regards,

IanT

Ensure the adjusting the screw is properly set and locked, locking was hit and miss on mine, I ended up cleaning it out with solvent and applying thread lock.

Also if you feel a notch, check the actuating shaft for damage, the ramp on mine was damaged, a thin layer of hard face weld, dressed with an angle grinder and polished with a stone provides a lasting solution without having to remake the shaft. It's a tricky weld as you don't want too much heat in the small shaft, but too low a voltage will give an undesired convex bead, making dressing it back harder, but it's not beyond the amateur. I'd practice on a piece of round bar first. I never fixed mine in the end, it was still usable but force required was becoming (very) excessive. I planned to use a dremel tool to make a vee notch up the centre of the ramp, on the actuating shaft, 1/2 to 2/3 the total width, and then use the remaining edges right and left as a reference to dress the hard face flat with diamond stones.

Thanks for the diagram. I've stripped it down, and not quite sure how it was successfully 'locked-up', but the basic problem is that the clutch ring has broken. It looks as though someones had a go at gluing, but obviously a non-starter. Is welding a possibility? I understand that spares are no longer obtainable..

Hello Steve,

I found your PM thank you, but my spare part went a long time ago

I have replied with some suggestions, but to answer your question on heat repair; I don't think it would be satisfactory at all and there would also be distortion to add to your woes.

Regards Brian

I have an early S7 but have had no trouble with the clutch.If the time comes when this happens and I can't fix it I will make the countershaft drive fixed and buy an inverter drive as you can turn these of without shutting off the moter ,might even work out better as you don't have to change the belt for speed changes.

Frank

I've got an early S7, with this same clutch. The horseshoe shaped friction part is expanded by the wedge, so as the clearance between the shoe and the bore of the pulley gets larger, the wedge has to distort the shoe further. Since the shoe is cast iron there's only one result. Ping.

I've looked at this on mine, and bought some tufnol sheet to make a replacement horse shoe. But I haven't tried making one yet, as the original is still in one piece. To reduce the amount the shoe has to expand I sleeved the inside of the pulley bore.

If I had a broken horseshoe I'd probably carve one out of plywood to get the lathe usable, then use the broken bits as a pattern for a replacement of more robust material. If the horse shoe is made out of a more elastic material than the original cast iron the internal shape of it probably doesn't matter too much, it's just the OD which needs to be round and a close clearance in the bore of the pulley.

Personally I'd bronze weld your broken bits back together, and take my chance that I could true it up enough afterwards, maybe turning the outer diameter true then adding a sleeve into the mating bore. But you need a lathe to mend a lathe...

So starting from here, I'd make a plywood "horse shoe", noting that the inner shape doesn't matter too much, it's just the OD which needs to be approximately round and a sensible fit in the pulley bore. I'd glue the plywood into the bore of the pulley with super glue, as you know you can cook this later and get the glue to part. Put the (now solid) clutch back together and reassemble the lathe drive. Now make a new horseshoe out of a suitable material. You are back to where you started, with using the lathe no clutch i.e. stop start. Nothing wrong with that! I'd still go with my lump of tufnol as first choice for making a horse shoe, but bronze would likely be second choice. Epoxy bonded plywood ( e.g. marine plywood) might be worth a try.

With a "new" horse shoe in your hand, strip the drive, cook the clutch to get the glue to give way, and re-assemble.

Plan B alternative approach has already been suggested, and is what I've done with mine. Fit a three phase motor and a VSD, jam the clutch up solid and take the operating handle off. Now use the VSD controls to stop and start the lathe. You can also have a "jog" function if you want it, easy peasy speed control and soft start as a bonus. I'm cautious about using DC braking as this slows the spindle and the inertia of the chuck might unscrew it. Maybe!

Plan C, I notice, is an advert in the "Wanted" section. Hope you are lucky!

Best rgds Simon

Simon

The inside of the ring, at least the three "feet" on the inside, need to be carefully machined to be a good fit on the clutch hub. See this pic. I wondered if the break in the ring could be pinned across the break.

Good luck with the spare, but do be careful assembling it. If the bore of the pulley is well worn that'll be why it broke in the first place. Be a shame to wreck the last remaining spare in the western world.

As for reinforcing the centre of the existing one, sounds like a good plan if you can make the bits you need. Fiddly sort of a job, I'd have thought, but worth it if you can do it.

Good luck, maybe post us a picture of the broken bits so we can see what you're facing?

How about this for a plan:

Find a bit of spun cast iron - meehanite preferably, or something that isn't going to break as soon as it flexes. (Still like my tufnol!) Turn the OD to size for the actual bore of the pulley less say 5 thou clearance. Face to length.

Mark out two holes at 5 o'clock and 7 o'clock, drill say 8 mm to give the radius. Ignore the rest of the annular slot.

Bore out the centre inner dia, as Robbo says it needs to be a good fit on the centre hub. As you approach finished dia you break into the two 8 mm holes and get an interrupted cut.

Now cut the wedge slot the old fashioned way with the Armstrong Planer.

At this point you've got a horseshoe shaped copy of the basic shape, The two "necks" at 5 o'clock and 7 o' clock will control the elasticity of the disc, and make it feel like the original. It's not going to matter that the annular slot is only a 4 mm radius, that feature is made that way 'cause the original relief is cast in.

Fit and forget. Hopefully!

edited to correct the radius from 8 to 4 mm.  Oops!

Edited By Simon Williams 3 on 26/11/2017 22:34:36

Sounds like a good one for me when I've practised a bit. Thanks.

Somewhat surprised by the original spec really. I wonder at what point in the design meeting they thought it a good plan to repeatedly flex something nice and brittle?

Mine has been going for 60 years Steve I don't think one can complain at that .

Frank

Have just joined and this is my first post! I have a very early S7 which was bought as virtual scrap and have managed to get it working again fairly well, but the clutch has always caused headaches and it was whilst seeking answers that I discovered this place. My lathe previously had a very rough life and was horrendously abused. The cast iron plate with the two 1/4”BSF grubscrews at 90 degs. on the right hand side of the countershaft had been smashed with a hard hammer and broken and the grub screw clutch adjuster broken off inside. After considerable difficulty I managed to wiggle the broken screw out and managed to drift out the countershaft-which has been damaged. I have stoned off the swelled high spots from the shaft so that it is serviceable but amtrying to locate a new one. If anyone anywhere knows of anything remotely serviceable, I would be most grateful! I have now remade the lathe so that it is running again but off up to you some of the modifications I have done. Firstly, some of the needle rollers were missing from he right hand bearing. I have cut lengths of 3/32” silver steel as substitutes and spaced them between the genuine rollers. Secondly, I have made 0.752” bore spacers to fit the gaps each side of theconed clutch pulley cluster. The left side is 0.195”thick and the right-0.300” thick. This seemed to prevent heavy lubrication loss from the bearings. The last modification was to make a new clutch adjusting grubscrews but drill the end and press in a 5/32” ball bearingto improve smooth operation. Hope this meets with your approval..