heavy clutch

[chris wastell]

There must be quite a few Flying Squirrel owners with the Pierce-type clutch plates which make a thicker pack than the original. When I fitted mine I ground a bit off the back of the g/box sprocket for clearance and fitted new springs from the spares scheme. I have a feeling that these may be stronger than the ones they replaced but the clutch, although working fine, is very heavy. Any ideas please anyone?

[Martin Heckscher]

Hi Chris,
I’m using Ian’s clutch plates & my clutch is OK. As the friction area is considerably larger with the bonded plates, you could try using just three springs……. I haven’t tried this, but it might work.
Best wishes
Martin

[chris wastell]

Thats an interesting idea. Surely the unequal tension will give unreliable disengaging? Where did your srings come from, out of interest?

[chris wastell]

Just thought, are you using his plain plates as well? as they are thicker than the originals.

[Deleted User]

Stating the obvious I ‘spose but the first thing to explore is the clutch cable run for the straightest possible route and smoothest bends to allow the inner cable an easy life.
Once upon a time there were on the market simple little plastic oiling point mouldings that clipped around the outer sheath of the Bowden cable after a small patch of the plastic cover had been removed, they were held in place with a couple of “U” shaped wire clips. These worked a treat if placed in the centre of the cable run as when the fresh oil started showing at each end there was every hope that it had displaced any muck that had found its way in.

Followed that up with a critical inspection of the whole clutch assembly, if the slots are at all fretted the new driving dogs may not be sharing the load equally and could be hanging up a bit.

It is possible to have a heavy clutch if the springs are too strong but would seem unlikely if they come from the spares scheme. However if the stack is thicker than before could they be close to becoming coil bound by any chance? Certainly try springs of a lower rate, after all their only function is to create enough pressure to transmit the power without slip. Any more and you’re just wasting the strength of you beer arm if you happen to be a sinister!

[Martin Heckscher]

Chris,

Ian supplied a complete set of clutch plates about 4 years ago, after I was having slippage problems at Dijon. When I first got the Sprint, about 15 years ago, the clutch was so heavy it was virtually unusable. This was caused only by massively heavy springs. I think the replacements may have come from Ken, and whilst perhaps very slightly heavy, the otherwise identical clutch was perfectly acceptable.

These same springs were re-installed when I fitted Ian’s bonded plates about 11 years later. I didn’t have any problems at all with the new plates, and there have been no further clutch problems of any sort since they went in.

The idea of using just 3 springs was suggested to me quite recently by Ken. He reckoned that with the additional friction area yielded by bonded plates, it should be possible to use six lighter springs, or perhaps even just 3 standard springs instead of the original 6. It made sense to me, though I haven’t put it to the test. There is surely no reason why the tension should be unequal provided they are properly adjusted.

Good luck!
Martin

[chris wastell]

Thanks for the answers chaps. The cable is as near perfect as can be achieved. I suppose my main concern with the heavy clutch is the strain on the actuating thread assembly and the fear of either it or the cable breaking. I will try three springs and see how it goes.

[Deleted User]

Chris Try slacking off springs untill clutch starts to slip (when opperating the kick start.) Then tighten springs just enough to stop the slipping.Make shore

the spring
plate lifts evenly when opperating the cable. I use an extra long clutch cable witch comes in from the back of the gear box. This makes a softer (bigger radius)bend than the normal cable run at the front end of the box.

[Deleted User]

Geoff points to the rather sharp bend required where the clutch cable inserts into its anchorage at the gearbox lug. On the ex-Lofty Avis FS the lug has been re-drilled at a point about 3/8″ further down, and angled towards the clutch operating lever. This has the effect of allowing a more gradual terminal bend of the cable, and an angled approach, which easily clears the flywheel. This seems to be a useful and simple modification.

Lofty’s cable also has a grease nipple in the mid-point, as suggested in efr215’s post.

[Deleted User]

Let’s step back a moment.

Counterintuitive it may be but the efficacy of any device depending on friction to operate is, in a narrow sense at least, independent of area, it is a function of the applied pressure and coefficient of friction ONLY.

In theory at least it would be possible for a clutch or brake for that matter to have the contact area of a pinhead and still work as long as enough pressure was applied. Naturally in the real world they ‘aint made that way ‘cos there are other not insignificant factors to take into account.

The point is that all that is needed is enough area to stop the device from self-immolation coupled with a just sufficient spring load to prevent slip at full power. More plates, stronger springs or anything else for that matter are just complication.

[Deleted User]

The Scott system does work but has a fairly large contact area and the lever is brass that does tend to allow fine grit to bed in a bit.
When it is getting worn, it does take more effort to move it against a given load. The other design difficulty is the sharp bend in the cable.
You have all gone through most of the options to allieviate a heavy clutch.
Cable. Lubricate well and minimise the bend as far as possible. Some years back I had Johnsons make me up a clutch cable with a nylon liner and this helped. I had used this years before on my Laverda production racer.
As regards spring setting, these things are a personal choice, so I certainly do not want to preach, just to record my preference. I set the clutch as light as possible so that it slips, then progressively tighten the springs till it just drives reliably. The logic is that not only do you have the minimum system load and thus rate of wear, but if you make a bad gear change, the clutch can slip a bit and act as an “Effort Limiter” to avoid damage.
I admit that I gave up on the Scott clutch release years ago in favour of a system that had been known of for years. Derek Whittle made one for Titch Allen and he loved it. It gets rid of the bad cable bend and reduces whatever load you have arranged with your own plate / spring setup by about 40%. As my Scott special racer has performed the duty of test bed for various ideas over the last 40 years, the clutch has been well looked into. With over 40bhp on tap, I need quite a strong clutch and the alternative clutch release copes with it well. The design was refined by my colleage Ted Hills and is now made to this design by Eddie Shermer.
If you have gone as far as you can with the traditional system but are finding the lever pressure difficult to cope with, then this is just to point out that there is another proven option. Kindest Regards to all. Roger

[Deleted User]

Roger mentions the Derick Whittle clutch lifting device.My version of this has been fitted to my Brum for 20 years and has had needed no attention at all,execpt for the occasional squirt of grease. It works a treat,and is much lighter to use than the normal Scott part. The basic bits to make mine were a lump of alluminium roughly 5×3 by5/8″, two 1/2″(hard) stai nles steel rods,and a pair of levers about 1″long (to twist the rods). Making and fitting to the gear box is quite a feat as there is very little room between the box and the clutch chainwheel.

[Deleted User]

Just rememberd something very funny(for me)when my mate Graham made a copy of my( Derick Whittle type) clutch release mechanism for his 29TT rep. After weeks of hard graft ,drilling,turning,filing,and fitting the new release was finished. The box ,release, and clutch were replaced in the bike and a new cable made up. Time to test how it feels. LOVELY, light as a feather. At this point I left Grayham to finish off. An hour or so later my phone rings. It”s Grayham. DISASTER, The last job is to refit the magnito chain,and it runs right through one of the opperating levers!!!. Had to see the funny side. Major mods fixedit (eventually) I sugested converting the bike to coil ignition. Can”t print his reply!

[Deleted User]

You are quite correct that there is not a lot of room, but we found that we could reduce the lifting pins to 10mm as this still gave exactly the same lift with the same cable movement as the Scott quick worm system. Naturally, reducing the pin size further reduced effort needed at the lever and enabled us to condense the assembly. Some efforts were made to be sure everything clears the gearchange lever and anything else, plus to avoid needing to machine the case. I think the odd minor bit of attention with a file is all that is necessary. It is quite easy to fit yourself and Eddie supplies it with all the cables ready to go. The release comes with an oil seal and quality INA thrust bearing. Eddie also can recondition high gear bushes and convert the high gear bearing to needle roller to reduce drag and wear here.
I am sure you all know by now that I can never leave anything alone if I think it can be improved. Don’t ask me why, it must be some form of insanity! Roger

[chris wastell]

All very informative. I think a call to Eddie is on the cards. I cannot slacken the springs any further. I have turned the heads of the adjusters down until almost non-existant but they are still only just clearing the g/box sprocket by a fag paper. Many thanks for all the comments.

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