CNW Clutch slave.

Thanks for the replies guys.

Nigel, I don't have a problem setting up a cable clutch for light operation. I've been at it a few years now! The Ajay's and Matchboxes had the same clutch actuator in the AMC 'box, so on familiar ground.

I must admit that I didn't know there where different profiles available for the actuator arm, which I learned from the Atlantic Green article. Also where I got the 0.1" lift from... I had seen it, but thanks for flagging it up anyway.

Not a 961 question John. I'm just chewing over some thoughts about comparisons of mechanical advantage and clutch lift on cable and hydraulic systems.

Hydraulic doesn't always come out with the best Mech adv to lift ratio, but cables are notorious for drag and poor maintenance, so get bad press.

Still interested to find out what piston size the CNW slave has... Seems to be a well guarded secret!

So... Can anyone tell me the piston diameter of the Colorado Norton Works Clutch slave?

Or any other Norton Hydraulic conversion for that matter.

It's often debated how good Hydraulic systems are, compared to a well set up cable clutch.

I'm trying to compile a set of figures for mechanical advantage, clutch lift and cost, to compare the various set upsand post up as a sort of "What Clutch" article.

Any contributions welcome.

Thanks for the info Katherine, and well done for having a go.

When you first posted a 7/8" slave piston I was surprised, as that would not produce a very good mechanical advantage, but you have edited that to 1" and it makes more sense.

I have gotten very bogged down with long calculations and measuring various leverage moments in the system. When suddenly I had an epiphany, you might say.

Of course mechanical advantage is only part of the equation. At the end of the day it's the overall mech adv from handlebar lever travel to clutch diaphragm liftthat should be counted, and this doesn't vary significantlywith whatever means are employed to transmit the handlebar lever force to the clutch, as it's more or less governed by the lever itself.

What varies is the effort needed at the lever to produce a given lift. It's fairly common knowledge that finding the sweet spot on the diaphragm via stack height is important to get the right feel to the lever, but that is the same for cable and hydraulic systems.

I have concluded that the advantage that hydraulic systems have over a cable is the lack of resistance and drag that the mechanical system can sufferand possibly the reduced maintenance.

I haven't counted the clutch cables that I have used over the years, but by and large they are no bother if lubed at least annually and routed sensibly. Every now and then though , one will be impossible to get sweet with routing or lubing, or at least will not stay sweet very long.

In recent years I have used one or two hydraulic clutches and have had no bother whatsoever except a weeping slave that I inherited from a previous owner and quickly fixed.

So I went round in a bit of a circle with the maths and came to a conclusion by looking at the question from a slightly different angle. I'm now happy to regard both systems as different, but not necessarilybetter or worse than each other..... Must get out more..!

Previously iain_brown wrote:

"I too would get out more - but i'm still working on my Norton."

Thanks for the info Iian, I will try Jim Comstock, But I imagine the piston size will be a fairly guarded trade secret!

Still working on my Commando too! I collected it a year ago in many boxes.

It had been in bits since 1979. So I have managed to loose assemble the grubby parts into something resembling a bike, just to see where everything goes and work out what upgrades to go for.

Obviously I'm listening to lots of Commando owners for advice, it being my first Norton after many Triumphs and AMC twins.

There seem to be two equally enthusiastic, separate camps, favouring cablesor pipes. So I seem to have been embroiled in a little bit of over thinking with that particular issue!

About a year ago I went on a little ride out with a couple of mates on Triumph and Commando. we were all comparing clutch pull, my mates were in awe of my featherlite Ducati Monster's clutch (and the rattle!).

It just so happened that the Commando cable snapped during the ride. Although repaired with a spare in under 20 minutes, I decided there and then, that I would be fitting a hydraulic clutch to my Commando. Now it seems I have a foot in both camps??

Previously neill_watkins wrote:

A bit of a late reply.

Quite well timed as it happens Neill.

Yesterday I went to see how a prototype was getting on with an engineer chappie I met this Summer. We got chatting about the idea and the next thing you know, there is metal cut! I won't reveal his name just yet, but he knows Peter Williams and has worked on projects with him in the past... So no fool!

I decided on the Brembo 13mm master as used by CNW, I am familiar with the Brembo stuff from serial Ducati ownership anyway.

The prototype has a 28mm slave piston, which is the maximum that will fit in clutch actuator hole and be retained by the original threaded ring, whilst retaining a 3mm cylinder wall ( I doubt the CNW piston is much bigger unless the wall thickness is less)

Early results indicate an unbelievably light clutch pull,(estimated less than 10lbs)but insufficient lift.. Or probably just sufficient lift actually, but we are going to try a 26mm piston to try and get 2mm+ lift and hope the mech adv is not knocked too hard.

With a spring balance on my Ducati clutch lever I am getting 10lbs pull... That's light! When I tried this on the Commando with a jury rigged cable, looping out in one smooth arc (no twists and turns under the tank ect.). I measured a 22lb pull and to be honest that didn't feel extra heavy compared to other cable clutches I have fingered in the past.

Just pulling the cable in, to slightly deform the perfect arc, increased the effort at the lever considerably. I didn't "weigh" this but it does imply that the cable routing has a very large effect on the clutch pull. (like we didn't know that!)

This morning I was examining a slave made by the late Malcom Saggers, an old friend of mine whom you may remember from the Roadholder article on the AMC Unified Twin project... He built the first engine.

That uses a 31.75mm piston, but sadly we couldn't measure the master bore so the maths is big guess, but the action is smooth, light and trouble free after many miles with Malcom and quite a few more in an Ajay with Colin.

Niell, your slave looks very nice and I like the bearing a lot. I will be very interested to see how you manage to mount it in the gearbox. Using the standard ring might be tricky as I suspect there is not room for it over the slave body (even with the lugs machined off). Perhaps you are thinking of tapping holes in the case to screw it on with the three lugs?

Also very interested to see how you have modified, presumably, a brake master? To fit the left handlebar? All I will say is, check the lift you can achieve with that particular ratio before you modify anything irreversibly... 2mm is desirable.

â? To be continued..

An interesting project Neill. I hope you can keep us up to date on here, as it develops.

I like the way you are solving problems with what resources you have and I love how you have reversed the Master. Ingenious.

It seems difficult to establish how much lift is required.. Especially without a running bike.

The Atlantic Green article states that the clutch is virtually disengaged at 1.27mm lift (Sorry to convert to mmbut I find metric fractions of inches to be infuriating!) Also that the Commando actuating arm gives more than double the required lift, which I think I measured at about 3mm, but like yourself have forgotten!

I think I will be happy with a minimum of 2mm lift, anythingmore will be an insurance against dragging, but probably a waste of effort?.. We will see.

The master that Colin was using with the "Saggers" slave really did look and feel like a 13mm jobbie, but would have been producing very little lift at that ratio. However it was lifting the coil spring Ajay clutch perfectly, so maybe those don't need very much lift?

It's frustrating not having all the pieces of any particular jig-saw here, but the mist is clearing and do seem to have become hooked on the idea of having a hydraulic system on the Commando... Very keen to ride it but loving the build anyway.. Thank goodness I have a Ducati to ride in the meantime..

Previously Katherine Scott wrote:

However both the bore and the stroke of the cylinder must be taken in to consideration.

Absolutely so Katherine. The master-slave ratio is not the whole equation.

The distance between the lever pivot and the piston rod is what governs the stroke of the piston. Longermaster stroke = more lift.

How much you can move the lever with your hand, depends upon the size of your hands and how much adjustment, if any, there is in the span of the lever. However the clutch should still work properly with the minimum span adjusted in.

Fancy modern levers have lots ofspan adjustment..Good for those with little hands.

Some of the latest radial lever sets also have adjustable stroke on the piston side of the pivot. This is done either with an eccentric pivot or by altering the angle of the piston rod to rest in differing positions on the lever

All very clever and perhaps a bit too much unless you really know what you're doing. Probably at least 60% gimmick in most cases!Besides which, a radial lever on a Commando would look a mite out of place!!

For the moment all that is adjustable on my project is the slave diameter, but it doesn't matter which element of the equation is manipulated. It's the overall ratio of lever movement to clutch lift that matters.

Neill, you will probably get away with the standard pushrod, as the adjuster is quite long. There's plenty of stroke available in your slave, but the biggest problem is going to be to get the piston "started" far enough up the bore to avoid bottoming on that circlip when the clutch is operated.

With a hydraulic slave, the adjuster is only used to position the piston in the bore with sufficient travel to work properly. once bled it stays in that parked position. The adjuster stays put, as no free play can be achieved, the piston always catches up with the rod and removes free play... Much as brake pistons move out to take up pad wear. (or rather, return less each time the brake is used.)

If we have the same handlebar lever moments, then I doubt that a 13mm master will move the 32mm slave very much. It moves my 28mm piston about 1.7mm or something.. 16mm should be much better.

With twin discs a 16mm master is ideal and a 13mm for a single disc, but don't be too quick to compare clutch operation with brakes. Brakes move very little, butuse lots of pressure. High mechanical advantage is used to achieve high pressures on the pads.

The clutch only has to overcome the spring pressure but flow enough fluid to move the piston far enough to disengage the plates.

Loving this project...