colchester student clutch

Hi all,

I have a square top Mk2, 6" student, 3phase UK machine......

there is no clutch fitted, the manual say's that those machines fitted with a spindle brake are not fitted with Matrix clutch from the factory and mine has the brake....dohhhhhh......

Had the top off to be sure.......

what I'd like to know is, has anybody fitted a clutch to a machine of this type....?

Initialy, I thought perhaps I could fit a clutch from a small car (with a lightened flywheel) but there's not a lot of room in the cabinet......whilst I don't mind some modifications to the panelwork I really don't fancy a full cut and shut job...any idea's please......thought that I'd go mechanical for clutch operation but don't mind air operation..........

the machine had burnt electric's when I got it, so binned the knee high rotary switch and fitted a push button on/off switch.....just replaced the contactor (after 5 years of on/off use) think it's time for a clutch........!!!!!!!!!!!!!!

thanks Clogs

Simple expanding shoe in drum clutches were used on many machines of the immediate post war era. For example I've seen all metal versions fitted to a large Victoria milling machine and an early 15" (ish) swing Harrison. Don't recall the exact details but I think both had a simple drum with a single split as the clutch "plate" with an expander operating in the split to bring it into engagement. Disengagement by natural spring. I think. Helped install the Harrison and recall that it took a while for us to figure out that the thing was a clutch, not a brake. Ex friend concerned got the machine on free if you move it terms as it had lost drive.

Might be room to re-work the pulley, or make a new one, with a drum both sides so a clutch of this style could be installed. Maybe use small motorcycle / moped brake shoes rather than try for a springy drum with split. Can see weight and balance being a potential issue.

Clive.

Initialy, I thought perhaps I could fit a clutch from a small car (with a lightened flywheel)

There are other alternatives to car parts. Ride on mowers, motorbikes as a couple of examples.

The Mk1 Myford Super 7 clutch is that format. It relies on the spring in the iron to release the "brake show" from the drum.

Hi an easy way to check if a student/master has a clutch fitted is to look at the rear of the headstock,there is a plate with instructions on how to adjust the clutches,there are two one forward,the other reverse. I agree there is not much room to fit an external clutch,could try a cone clutch on the motor shaft there is some room or the cover plate could be removed for more space,or try the the method of engaging the cutter deck on ride on mowers,i.e. a slack v belt from motor to the headstock pulley with an over centre jockey pulley,to tighten the belt. simple & reliable and an old cutter deck could be sourced from a mower agent. For safety when the belt is loose and there is the possibility it could just about drive the spindle ,a simple wedge brake block could engage one v pulley to stop spindle rotation and connected to the clutch linkage, go and have look at a cutter deck just to get some more ideas.

Worst part of a conventional in-line clutch add on is finding room to get all the parts concentric

Lateral thinking time.

I've seen reports that cable operated disk brakes using bicycle components are compact, effective and relatively easy to fit to lathes. So, given the limited space available under the covers, maybe consider re-purposing the existing brake components into a drum type clutch with an externally fitted brake using the aforementioned bicycle components. Single lever brake one way, clutch t'other spindle free in the middle would be nice.

Slack belt - tight belt jockey pulley clutches work well with single belts but use on a multiple belt drive doesn't feel quite right. Can't see any objective reason why not but ...

If you do decide to go for a conventional inline clutch, hydraulic operation using an in-line "round the drive shaft" slave cylinder is probably easiest to engineer in. If its a small one the brake master cylinder assembly of a big motorcycle should shift enough fluid to operate it. Just need to sort out a lever. Way back I drew out a system of this style for a friend based on a SAAB 900 clutch cylinder and BMW R 50-60-75 motorcycle cable operated "under the tank" master cylinder. Never proceeded with the project as his plans changed. As we had the parts to hand I presume we did some preliminary tests to verify that the hydraulic side was workable before I started drawing.

Clive.

Thanks, so far...........

I actually fix ride on mowers all the time........

A slipping belt drive is not safe, especially with hands around the chuck, just can't trust it......

as I understand it, the brake shoe type clutch used on old mowers and the like required centrifugal forces to operate the shoes hence giving drive but don't quite understand how the shoes can be operated simply, going from stationary (clutch disengaged) to rotary when clutch is engaged......it would be nice as the shoes and drum are already there but the linkage etc would be horrendous.......?????

There is a very nice 3 ball bearing clutch fitted to Husqvaner mowers, this operate with the balls getting pushed into tapering slots, hence giving drive BUT it only works in the Horizontal plane...of course there are the elelctric clutches which are actually Auto air con pump drives but I'm always replacing them, so they are out........

I also have a clutch from an industrial sewing machine but it's not strong enough........

the multi plate clutch from a motorcycle is ideal except there is no thru shaft, like a car..... actually the clutch basket/case rotates on a bearing with the driven/friction plates driving the gearbox imput shaft thru the lot......

To keep it simple and reliable I was kinda thinking of mounting a lightened flywheel on the end of the motor via an adaptor flange with a clutch fitted as normal but making my own splined jockey shaft for the clutch to drive....this shaft supported/mounted on 2 flanged self centering bearings with the double belt pulley inbetween the bearings......

this would entail that the motor and clutch is mounted outside the lathe, which would drive an idler/slave shaft and pulley to drive the headstock, mounted where the motor used to be.....

so to be clear, the motor/clutch assy would be mouted outside the lathe on an adjustable plate with short belts driving the idler shaft, which will in turn drive the headstock using the original belts.....operating linkage, hydraulic/air/mechanical is the easy bit....hahaha....

Awaiting a better solution.......thank u all........clogs........

How about the electromagnetic clutch and pulley assembly off a car air conditioning pump? Said to be around 3 to 5 HP continuous rating which ought to be enough. They seem pretty reliable. Well I've never met anyone who had the clutch fail, plenty of other stuff yes but not the clutch itself.

The drum clutch expander mechanisms on the Victoria and Harrison were very simple. Don't recall details tho' and the Victoria parts book I still have (why?) is for a later one which didn't have a clutch.

Another simple mechanism for an in-line clutch is the ball and dimple system used by Triumph. Two plates with matching sets of part hemispherical holes on a common central shaft. Bit under 1/3rd nominal hemisphere deep I think. One plate can be rotated by a cable or lever, the other is keyed against rotation. Balls of same nominal diameter as the part hemispheres sit in the holes between the plates. Turning one plate misaligns the balls relative to the holes pushing the the non rotating plate along the support shaft. Maximum shift is around 1/4 to 1/3rd ball diameter.

Clive.

I have a student round head with a flat belt drive & no clutch, so I mounted the motor on a hinged platform & a balanced lever mechanism [like a traction engine valve gear lever] & it lifts & locks & drops & locks & has worked for me for the last 30 odd yrs, & as for not being safe well I just move the high & low ratio gear lever to the middle so it can never drive or be unsafe whilst making measurements etc, my edgewick lathe was made to work like that with a flat leather belt, a friend converted his vee belt colchester to flat belt to do the same, a big let down on colchesters not having a clutch.