Pre-1964 Dominator (Atlas) clutch ?

APRRSV · Dec 19, 2016

My understanding is that pre-1964 clutches had 9 plates; 4 steel, 4 double sided friction and 1 single sided friction. From 1964 onward this was changed to an 11 plate clutch; 5 steel, 5 double sided friction and 1 single sided friction.

My question is for any of you that may have had experience with both types and whether you noticed any significant advantage/improvement in the later, 11 plate version.

I have a 9 plate version and am wondering whether it is worthwhile to purchase the deeper clutch basket and a couple more plates. I will be using this clutch with a motor with considerably more power than a stock Atlas.

Thanks,
Ed

frankdamp · Dec 19, 2016

I've been away from direct involvement with the various Norton bikes sinceI emigrated to the US in 1968. After riding my company-provided 650SS (a 1962 model, I was told), I don't think I'd want any higher clutch lever loads than the original. If the Commando dciaphragm-spring clutch will fit, that would be the way to go. At my current age (75+), plus arthritis, I don't think I could even manage to old 650SS clutch any more

texasSlick · Dec 19, 2016

I am not familiar with an 11 plate Atlas clutch .... did not know such existed.

More plates have the advantage the clutch can transmit more torque, or conversely, deliver the same torque as a clutch of lessor plates, but with less clamp force.

In theory, should you obtain a deeper basket and fit more plates, you should be able to back off the spring pressure and enjoy lighter clutch pull with no slipping. OTOH, if you have a hot engine, more plates will harness the torque with no more clutch pull than the 9 plate clutch.

I have never had a problem with slip (9 plate clutch), but have struggled with a heavy clutch pull. Using a Venhill Featherlite Teflon lined clutch cable has reduced the pull by about 25%, and the pull is now manageable, but still a four finger affair.

Slick

dynodave · Dec 19, 2016

:!: watching with interest. :roll:

APRRSV · Dec 20, 2016

Thank you Frank and Slick for the comments. I welcome additional comments from others.

Ed

APRRSV · Dec 20, 2016

Slick, do you know whether your clutch basket/chainwheel has friction material bonded to the inner back surface?

Ed

texasSlick · Dec 20, 2016

APRRSV said:
Slick, do you know whether your clutch basket/chainwheel has friction material bonded to the inner back surface?

Ed

Here is a link to the Atlas/Dommie clutch

https://andover-norton.co.uk/en/shop-dr ... odels-manx

Item (1) is the innermost friction surface. As you can see from the drawing, it is not part of the chainwheel. The chainwheel is Item (13) and DOES NOT have friction material bonded to either side of the rear surface.

Slick

Rohan · Dec 21, 2016

The 1962 Parts Book lists 3 versions of AMC clutch - 3 plate 4 plate and 5 plate versions.
3 plate is for the Model 50, 4 plate is ES2 and dommie, and 5 plate is 650.

The design seems to have revised along the way too, so may be a few versions of each.
FYI...

Bernhard · Dec 31, 2016

According to the Mick Walker Book of the Norton Dominator in 1962 an extra clutch plate was fitted to the Atlas (page 74).
Also on page 143 he states that “well before he left Norton Doug Hele rectified the Atlas problem except the clutch, which was to remain something of a weakness.”

It all depends on how much you abuse the clutch, if you are hauling a double Adult sidecar or making quick getaways from the traffic light grand prix then you may need to pay more attention to the clutch.
You could always apply the Heinz Kegler clutch mod.
I have seen on various Norton’s the normal 4 spring, but also 5,6,and 7 spring clutchs which mainly came off a English speedway bike shop.

Rohan · Dec 31, 2016

Bernhard said:
I have seen on various Norton’s the normal 4 spring,

All the Norton clutches I've seen have been 3 spring ??

dynodave · Dec 31, 2016

5 spring clutches from my featherbed's
http://atlanticgreen.com/images/5spring.jpg
sorry for big file

Rohan · Dec 31, 2016

Heh heh.

You ever heard of a screenprint, and save it to a (much reduced in size) file.
This one is nearly a hundred times smaller, took 20 secs to do, if that.
https://s27.postimg.org/ht2s8w5kj/5springs2.jpg

dynodave · Jan 1, 2017

So far within my 5 spring clutches the biggest variances I find:
clutch plates 4 different thickness' .070-.086-.090-.096
friction plates 2 types and 2 thickness'
3 different diameter & length springs
2 different thickness aluminum pressure plates (thick one from Dunstall built 68)
easy to make up the 5/5 stack using the thin components
The 5/5 stack using the thick components will not fit.
All my chain wheels/basket are the same depth... these are from 68, 66, and 63 + flea market
HTH

APRRSV · Jan 1, 2017

Thank you Bernhard and Dave.

Dave, I assume by "my 5 spring clutches" you mean your 5 clutches with 3 springs?

Ed

Pre-1964 Dominator (Atlas) clutch ?

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