Lever pivot effect on clutch action

Information relating to the Matchless G11 or AJS Model 30 600cc twin
Posts: 15
Joined: Sun Feb 22, 2009 3:16 pm
Location: UK

Lever pivot effect on clutch action

Postby silverspur » Mon Nov 07, 2016 2:10 pm

I've recently bought a '56 M30 which came with an AMC gearbox and, it appears, a Burman five-spring clutch. I have no idea if this is a good or bad combination but I do know that the resulting clutch action is very heavy. I checked everything on this site about correcting it and have carried out them all with but minor improvement.

This post is about levers. Mine, I know are incorrect - they are 11/8" pivot centres whereas the original should be 7/8". I haven't changed them because, I thought, 'longer leverage, lighter action'. But someone mentioned in passing the other day that, in fact, a shorter the pivot centre gives better leverage and hence a lighter action.

Can anyone confirm that this is/is not the case? Thanks.

Member
Posts: 1310
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Lever pivot effect on clutch action

Postby Mick D » Mon Nov 07, 2016 2:27 pm

Hi

The 7/8" fulcrum will give a lighter action but less cable movement is the pay back.

Regards Mick

Member
User avatar
Posts: 9837
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Lever pivot effect on clutch action

Postby Rob Harknett » Mon Nov 07, 2016 2:53 pm

I was told the opposite, which works with other tools, crow bars whatever. The longer the leverage the lighter the action. Do the see saw test. A child at the end can balance an adult close to the centre, That's proof that cannot be denied. Less strength required with a bigger pivot centre.

Member
Posts: 609
Joined: Thu Feb 27, 2014 9:27 am
Location: Kent, England

Re: Lever pivot effect on clutch action

Postby JimFitz » Mon Nov 07, 2016 3:21 pm

silverspur wrote:I've recently bought a '56 M30 which came with an AMC gearbox and, it appears, a Burman five-spring clutch. I have no idea if this is a good or bad combination but I do know that the resulting clutch action is very heavy. I checked everything on this site about correcting it and have carried out them all with but minor improvement.

This post is about levers. Mine, I know are incorrect - they are 11/8" pivot centres whereas the original should be 7/8". I haven't changed them because, I thought, 'longer leverage, lighter action'. But someone mentioned in passing the other day that, in fact, a shorter the pivot centre gives better leverage and hence a lighter action.

Can anyone confirm that this is/is not the case? Thanks.


7/8" pivot centres mean that the lever has to move further to give the same cable movement as 1 1/8" pivot centres giving more mechanical advantage hence less effort (but more travel) on the lever making the clutch feel lighter.
One of my bikes came with 7/8" lever mounts and 1 1/8" blades giving a heavy clutch and a misalignment of the cable at the lever making things even worse!

Jim
Too old to Rock and Roll but too young to die.

1952 G80 rigid, 1960 G12 DL / Watsonian Monza, 1954 G80S.

Member
Posts: 1310
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Lever pivot effect on clutch action

Postby Mick D » Mon Nov 07, 2016 3:22 pm

Hi Rob

I think you're wrong - to use your analogy the 1 1/8" lever moves the adult further from the fulcrum and now the child can no longer balance him.

Regards Mick

Member
User avatar
Posts: 9837
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Lever pivot effect on clutch action

Postby Rob Harknett » Mon Nov 07, 2016 4:01 pm

I have never tried the two Mick, a mate of mine searched ages for 1" pivot I believe, He claimed they needed far less strength to operate. If I have ever come across a " heavy clutch " it is usually found to be a combination of, lubrication of the cable AND thrust rod, thrust rod as they do tend to seize. Also no sharp bends in cables. A spray inside the gearbox on the clutch moving parts, with WD40 can also work wonders. Also for people with small hands. Put a chain split link on the handle bar lever bracket. This acts as a stop, so the lever is closer to the handlebars. This can also make a heavy clutch feel light, the person with small hands not having to use finger tips to pull with.

Member
User avatar
Posts: 9837
Joined: Mon Jan 01, 1990 12:00 am
Location: ESSEX UK

Re: Lever pivot effect on clutch action

Postby Rob Harknett » Mon Nov 07, 2016 4:05 pm

On my front brake I tend to have that adjusted up with more slack than advised. So I get a better grip with my small hands. The brake seems very heavy if I try to pull it in with my finger tips.

Member
Posts: 433
Joined: Fri Jan 03, 2003 12:00 am
Location: POWYS UK

Re: Lever pivot effect on clutch action

Postby petert120r » Mon Nov 07, 2016 4:19 pm

7/8" centres is correct

Member
User avatar
Posts: 2190
Joined: Mon Oct 05, 2009 12:00 am
Location: ESSEX UK

Re: Lever pivot effect on clutch action

Postby 1608 » Mon Nov 07, 2016 4:26 pm

7/8" pivot to nipple is easier than 1" or 1-1/8". A simple analogy being thus:-
Try pulling a stubborn nail out of wood using a claw hammer and then do the same with a small piece of wood etc under the claw. Far less force is needed when the the pivot or axis is closer to the resistance. I'm sure this could be explained far better mathmatically or with a diagram, I'm not smart enough to try either.

Member
User avatar
Posts: 1365
Joined: Thu Jul 10, 2003 12:00 am
Location: HAMPSHIRE UK

Re: Lever pivot effect on clutch action

Postby Duncan » Mon Nov 07, 2016 4:52 pm

Does the same apply when removing nails from children* or have I lost the plot along the way?

*Hypothetically speaking that is.

Next

Return to G11 / AJS Model 30

Who is online

Users browsing this forum: No registered users and 4 guests