Switching primary drives.

I'm familiar enough with multiplate, multi-spring clutches , in fact I have been dealing with them for 50 years as of yesterday ( bought my first bike, a Norton ES2 50 years ago)
I thought the Newby clutch with modern linings and a totally dry environment would operate with much less spring pressure than the clutches of old, some of them being cork insert and generally not great clutches.
I hoped it might be at least close in lightness of operation to the Commando with oily Barnetts, given that the friction levels on a good dry clutch are generally higher for a given pressure than with an oil clutch.


Glen

worntorn said:

I'm familiar enough with multiplate, multi-spring clutches , in fact I have been dealing with them for 50 years as of yesterday ( bought my first bike, a Norton ES2 50 years ago)
I thought the Newby clutch with modern linings and a totally dry environment would operate with much less spring pressure than the clutches of old, some of them being cork insert and generally not great clutches.
I hoped it might be at least close in lightness of operation to the Commando with oily Barnetts, given that the friction levels on a good dry clutch are generally higher for a given pressure than with an oil clutch.


Glen

Click to expand...

I suspect clamping force has more to do with the friction level. I wonder if the friction surfaces play to the engagement as opposed to the clutch holding.

1up3down said:

I gotta ask because I don't get it...

someone explain why the clutch plates are easier to separate, why the lever pull would be different, depending upon if one happens to be running a dry belt of oiled primary chain?

having had a chain for 30 year and now the last 15 with a dry belt I honestly can say I can tell no difference at all

Click to expand...

Simply changing to dry operation doesn't make for a lighter clutch. You have to increase the stack height to do that. You COULD do that with a wet clutch, but it would be much more likely to slip than with a dry one.
The magic lies in the way diaphragm springs work as opposed to coils. As the spring deflects, as in when disengaging the clutch for example, the load on the actuating mechanism - ie the clutch lever & cable - becomes less. I guess that is why diaphragms superseded coils for automotive clutches.

Increasing the stack height mimics a partial disengagement scenario for the spring, and the load on the actuating mechanism drops a little. The clamping force on the plates also drops.

I recall reading some info that Dyno Dave published where he plotted load vs deflection data.

MFB said:

1up3down said:

I gotta ask because I don't get it...

someone explain why the clutch plates are easier to separate, why the lever pull would be different, depending upon if one happens to be running a dry belt of oiled primary chain?

having had a chain for 30 year and now the last 15 with a dry belt I honestly can say I can tell no difference at all

Click to expand...

Simply changing to dry operation doesn't make for a lighter clutch. You have to increase the stack height to do that. You COULD do that with a wet clutch, but it would be much more likely to slip than with a dry one.
The magic lies in the way diaphragm springs work as opposed to coils. As the spring deflects, as in when disengaging the clutch for example, the load on the actuating mechanism - ie the clutch lever & cable - becomes less. I guess that is why diaphragms superseded coils for automotive clutches.

Increasing the stack height mimics a partial disengagement scenario for the spring, and the load on the actuating mechanism drops a little. The clamping force on the plates also drops.

I recall reading some info that Dyno Dave published where he plotted load vs deflection data.

Click to expand...

Yes, I went thru that info on the Atlantic Green site before setting up my Commando clutch. I'm not sure if that page is still on the website.
Dave explained it all very well and also pointed out that setting up the diaphram for a super light pull also meant reduced clamping pressure ( no magic there) and that you might have clutch slip.
When I first set things up so that one finger on the lever was enough to disengage the clutch, I remembered the mention of possible slippage. 850s do make a lot of torque and clutches only care about torque, so it was a pleasant surprise when it held anything thrown at it.

Clutches are a funny thing, some work great, some not so well. For example, the six spring BSA and the 3 spring Triumph. The six spring BSA is so hopeless that most use a conversion kit from SRM to mount the 3 spring which, spring number aside, is almost the same clutch. And shouldn't six be better than 3? Dan Smith and I had a good chat about this the other day.
He's a guy who when he needs a clutch , goes down in the basement, designs it then builds it and it generally works.
But he also cannot figure out why some work so well and others so poorly. I was relieved to hear that

Beltdriveman has explained to us about 100 times using a great many calculations that our Commando clutches don't work.
But we know that with a bit of of adjustment now and then, the stock Commando clutch works very well , as does the rest of the primary.
So for the OP, the stock setup is very easy to live with, no need to change it out unless you just like the idea of a beltdrive.
11 bikes here and the Commando has the 2 nd easiest clutch. Almost as nice is the multi-spring run in oil Vee two clutch on one of the Vincents. Go figure.

Glen

swooshdave said:

I suspect clamping force has more to do with the friction level.

Click to expand...

Don't forget the 2nd part of the 2-part equation, the coefficient of friction.
And I suspect that the coefficient of friction would be substantially higher with dry plates than with oily ones.

Has anyone answered the OP's question in the affirmative yet?

ON my Atlas I went to a Heyward belt drive just to stop the unstoppable oil leaks from the tin primary covers. Also, no matter what I did I could not ease the clutch pull. So I fitted a Magura Hymec hydraulic clutch (which uses mineral oil) and it became a two finger clutch and I became a much happier Norton owner. The Magura system required some fiddling but it works well and is not really obvious on the handlebars.

After 35 years of riding my Norton with the stock set up I decided to set up a belt drive primary as so many went that way, I went for the RGM beltdrive, once set up with double adjusters on the gearbox, It worked very well for a few years and over 10k on it, but when I first set it up it didn't to me really make any diffrents to the performance of the bike or clutch had about the same running vibrations, but having a dry clutch seemed to work a bit better but found the clutch sometimes ingaged to quickly but once I got use to that was good.
After a few years use I started to have a few problems with the belt trying to run off even after readjustments, I never broke a belt but because of this problem I was having the belt was wearing on the front pully plate and and tearing the side of the belt then after replacing the belt with a new one it wasn't long when the pully plate shatted in 3 pieces, so aftermany attempts to fix the problem I decicded to go back to a chain drive and I will use the belt drive on my project bike, I never had any problems with chain drive in all the years I ran it.
The biggest problem with wet clutch is finding a light oil to run in the primary so the clutch didn't slip, I am still running my orginal clutch plates even after over 140k and over 40 years of hard riding and its always been a one finger operation if you only want to use one finger of course, but of corse the triplex chains today are crap and my next chain will be one of Andy's who is a very good person to deal with.
I have never had a problem with gear oil migrating into the primary as I meause the mount of oil that is recomanded in the manual, most people that do have that problem are over filling the gearbox maybe, who knows, but I am happy with running my primary in oil, so to me running a belt drive verse chain drive seems to make no diffrents to me but of course a chain doesn't need to be so finely adjusted as a belt needs to be to make them run true.

Ashley