Worty's front brake

[Worty]

Adjusted primary and final drive chains on GF and Kwaka.  Good clean all round for both.  Found out that the exhaust recirc ports on the Kwaka had not been blanked off, so grommeted them.

I think I've actually managed to get the brakes on the GF sorted for the first time since I've had the bike.  Moved the crossover lever forward for the rear brake to get some decent adjustment AND, did a bit of a mod on the front (see pics) which has cured the problem of having the brake arm at a ridiculous angle on the brake plate and having two lots of adjusters at the handlebar to take up slack.  I'm guessing that it doesn't really matter which way round the front brake is actuated, it stops the bike, and I've got loads of adjustment potential (shoot me down if you've any concerns).

Very satisfying day overall.  Just need to check carb sync on Kwaka and both are ready to hit the road (when weather shows up, of course).

[limeyrob]

I think it does make a difference which way round the lever is, and if I could remember I'd tell you
I seem to recall its about the leading shoe contacting the drum first and so the leading shoe should be on the inner edge of the cam, but I'm happy to be corrected, especially if there's an explanation!  Which ever way it is it makes enough of a difference that BSA changed the levers round.
If the cable isn't quite right I use the Triumph clutch cable spacers - 57-2062 and 57-2063, these are quite hefty and stay in place.

[muskrat]

G'day Worty.
With the lever in that position it's more prone to be struck by road debris and force the brake on 
I tried it on one of my dirt bikes once. Did the superman over the bars.
I too think Rob is correct about the cam and as the cam is worn the "new" side will be a bit more "savage" giving the feeling of better brakes.
Cheers

[Worty]

Cheers guys.  Musky, surely it'd take something pretty hefty on the road to bash the brake on??  Also, I'm sure there are other models that have the lever in that position.  What I do know is that the brake is now the best it's ever been.  If there is another issue with this setup, I'd be glad to hear it.  Can't get my head around how leading edges would come into play.  The brake shoes are exactly the same and are opening at the same point.  As this system is pretty basic, I'm not sure what issues could arise.

[limeyrob]

Its to do with the cam on the lever, the inner one is nearer the pivot of the shoe so its moves that shoe just a little bit more than the other shoe so its touches the drum first.  The theory is you want the leading shoe to touch first.  I'll try to find the link rather than remember it poorly.

[Swarfcut]

 You folks are all correct, its a "reverse lever" and for the reasons cited, a leading/trailing shoe set up works better if the lever rotates against the rotation of the wheel, typically plunger and early S/A bikes have a good rear brake with the lever pointing down on the left side. Later S/A bikes have it pointing down on the right, so again, against the direction of rotation.

 Some AJS and Matchless bikes have the lever on the front hub on the left, pointing forward, so again a reverse lever.

 If I could find  fork sliders with fore and aft lower mudguard stay mounts and Y bracket bridge, the whole front end could be reversed to give a left side forward pointing lever, in the AJS style. Reckon this would transform the full width iron hub brake mediocre performance to something a good deal better.

 Once a shoe contacts the drum, further movement of the cam is stalled, with the normal full width front hub assembly, it's the trailing shoe that is getting the first touch, so servo action from the leading shoe is minimal. Trick removal of lining thickness to the trailing shoe was done in the past to effectively run on just one leading shoe.

 Swarfy.

[Worty]

Thanks guys, comments much appreciated.

Bottom line is 'is it safe' and could I experience any major problems?  What I can say is that the brake is far better at the moment, has plenty of adjustment, and fits together really well. 

The only other thing I could do is get a longer cable and move the lever to the original position but further back on the cam.  Unfortunately that'd leave it too far forward and would be sticking out beyond the brake plate.

Apart from fiddling around with cams and spacers, the current set up seems like the best solution all round.

[RogerSB]

Can't get my head around how leading edges would come into play.

Just in case it's any help here are the notes I made for myself on the subject.
Rog.

[Worty]

Cheers Rog, but what does this mean for my 'adapted' set up.  Both shoes are exactly the same as are the springs and linings.  Does my set up simply mean that the trailing shoe is reversed?

[RogerSB]

Both shoes are exactly the same as are the springs and linings.  Does my set up simply mean that the trailing shoe is reversed?

Worty, Looking at the drawing (and thinking out of the box) and imagining the lever reversed from the one in the drawing and pointing upwards (like yours) the pull of the cable will turn the cam the other way (clockwise instead of anti-clockwise . . . in the drawing). How that will affect the force applied to both the shoes I'm not sure.  If it's applied to the trailing shoe slightly earlier than to the leading shoe I think it would. If the force is equal I don't think it would. Maybe someone with an engineering diploma can tell us?
Rog.

[Worty]

Both shoes are exactly the same as are the springs and linings.  Does my set up simply mean that the trailing shoe is reversed?

Worty, Looking at the drawing (and thinking out of the box) and imagining the lever reversed from the one in the drawing and pointing upwards (like yours) the pull of the cable will turn the cam the other way (clockwise instead of anti-clockwise . . . in the drawing). How that will affect the force applied to both the shoes I'm not sure.  If it's applied to the trailing shoe slightly earlier than to the leading shoe I think it would. If the force is equal I don't think it would. Maybe someone with an engineering diploma can tell us?
Rog.

This is it Rog.  As both shoes and springs are identical, as is the cam, then I can't see what difference it would make except for reversing which is the 'leading shoe' (or the first shoe to make contact with the drum).  I've tested it and it stops at least as well as it did before, if not better.

[RogerSB]

Here's another description which I pinched from somewhere, which explains it further.
Rog.

Edit: Rob's thoughts seem to suggest that the cam applies the force slightly more one end of it than the other.

[berger]

nice one rog, hence my mates rear brake drum with a broken spring and when he touched the back brake lever the brake kept snatching and locking the wheel.

[Worty]

Given that the leading shoe and trailing shoe are reversed when going backwards, wouldn't this simply be the case with my set up?

[limeyrob]

I think its movement of the shoe not force, so the inner end of the cam is nearer the shoe pivot so its less force but more distance so it contacts first. I'll admit to finding this confusing but those who have set all this up right say it really makes a difference.  I also drive an old Land Rover with twin leading shoe brakes and they are pretty good, they have a strong self servo effect as the drum rotation pulls the shoe in but this means they are very poor in reverse and sensitive to changes in friction, for example when its damp.