H: Hubs, Wheels and Tyres Eight inch brake ?

[greg brillus]

The steel plates do bend, mostly at the anchor pins, and probably more on the rear than the front. But there are so many small items that can lessen the performance, especially grease and oil on the rear brakes. When all is well the standard brakes do actually work quite well, but having shoes that can move on their pins and the two pins anchored together would go a long way toward helping, this should be done on the 8 inch brakes from new.

 

[davidd]

It seems that the 8" brake is stuck with fixed pivots and the poor braking associated with the uneven wear between the leading and trailing shoes. Cheers, Stu.

Stu,

You are probably half right. The fixed anchors were Mike's choice, but not mandatory. I installed the 8" brakes on my racer in 2009 using the balance beam as it was intended and those brakes have been going strong with no adjustments like shimming out the leading shoe. I would expect that they are more prone to the "equal work condition" but they have not seemed to demonstrate it yet.

Of course, there is often a battle between two factions regarding SLS brakes: The "opposers" those who want the front brake lever to rotate in the opposite direction of the wheel and the "clockwise" guys who want the brake lever to rotate in the same direction of the wheel. Because the brake cam is flat, the shoe lifted by the inside edge of the cam (the lobe closest to the axle) will get lifted higher, but with less force because it is nearer the pivot ( "opposers"). The shoe lifted by the outside cam (furthest from the axle) will have less lift, but it will exert higher force on the drum. It is possible that one or the other might have a different impact on braking and lining wear or they could both be bad.

The Phil's were opposers, which is why the front brake arms point forward. The clockwise guys, the Gold Star racers like Dick Klamfoth and Mann found better braking by pointing the arms rearward. I have no idea.

David

 

[davidd]

The steel plates do bend, mostly at the anchor pins, and probably more on the rear than the front. But there are so many small items that can lessen the performance, especially grease and oil on the rear brakes. When all is well the standard brakes do actually work quite well, but having shoes that can move on their pins and the two pins anchored together would go a long way toward helping, this should be done on the 8 inch brakes from new.

Greg,

It does seem that there a too many variables.

I was wondering about Tevor's comment and trying to decide if he is telling us that we are confusing effect with cause. If the shoes clamp themselves into the drum at maximum pressure it seems likely that they would be an incredibly powerful clamp that is fiercely holding the brake plate from moving and flexing, assuming correct machining. If this is true, it might be that the brake plate would flex because the shoes were flexing. Then the shoes would be the cause of the flexing and the brake plate flex would be the effect.

I had planned to do the Burt Weisz mod which floats the shoe posts. I got scared off when I read that it was not wise to float a leading shoe (I think). I remember I looked at just floating the trailing post, but without a substantial modification to the brake plate it was difficult to do.

Finally, there has been a long tradition in the Club of running a softer brake lining on the trailing shoe so it will wear at an equal rate (assuming that soft lining wears faster). That is a solution also.

David

 

[Bill Thomas]

Greg,

It does seem that there a too many variables.

I was wondering about Tevor's comment and trying to decide if he is telling us that we are confusing effect with cause. If the shoes clamp themselves into the drum at maximum pressure it seems likely that they would be an incredibly powerful clamp that is fiercely holding the brake plate from moving and flexing, assuming correct machining. If this is true, it might be that the brake plate would flex because the shoes were flexing. Then the shoes would be the cause of the flexing and the brake plate flex would be the effect.

I had planned to do the Burt Weisz mod which floats the shoe posts. I got scared off when I read that it was not wise to float a leading shoe (I think). I remember I looked at just floating the trailing post, but without a substantial modification to the brake plate it was difficult to do.

Finally, there has been a long tradition in the Club of running a softer brake lining on the trailing shoe so it will wear at an equal rate (assuming that soft lining wears faster). That is a solution also.

David

Dear old Bill Hancock, If you had problem, He was the Man to ask, He sent me 2 A4 papers once, On where to put the oil feed hole in the barrel.
Very much a Standard Man !, But someone told me he had a Norton clutch on his outfit !. Cheers Bill.

 

[stu spalding]

Greg,

It does seem that there a too many variables.

I was wondering about Tevor's comment and trying to decide if he is telling us that we are confusing effect with cause. If the shoes clamp themselves into the drum at maximum pressure it seems likely that they would be an incredibly powerful clamp that is fiercely holding the brake plate from moving and flexing, assuming correct machining. If this is true, it might be that the brake plate would flex because the shoes were flexing. Then the shoes would be the cause of the flexing and the brake plate flex would be the effect.

I had planned to do the Burt Weisz mod which floats the shoe posts. I got scared off when I read that it was not wise to float a leading shoe (I think). I remember I looked at just floating the trailing post, but without a substantial modification to the brake plate it was difficult to do.

Finally, there has been a long tradition in the Club of running a softer brake lining on the trailing shoe so it will wear at an equal rate (assuming that soft lining wears faster). That is a solution also.

David

Hi David, I've had no problems at all with the floating leading shoe on the Bert Weisz mod, indeed, nothing but praise. I'm not to well up on all the theories being put forward on the matter, I'm a "try it and see" man. It definitely works in practise. Merry Christmas, Stu.

 

[bmetcalf]

FWIW, the Triumph 2LS brakes in the late '60's had sliding shoe 'anchors'for both leading shoes.

 

[john998]

Hello Bill, dear Bill Hancock did not have standard cluches in any of his many post war twin bikes. Now and again I could not
Resist reminding of this. Still miss his amazing span of knowledge of the Vincent.
Happy Christmas to one and all. John.

 

[Bill Thomas]

Hello Bill, dear Bill Hancock did not have standard cluches in any of his many post war twin bikes. Now and again I could not
Resist reminding of this. Still miss his amazing span of knowledge of the Vincent.
Happy Christmas to one and all. John.

You should know !, Your ear was near the clutch, Racing his outfit.
Just been looking at some silent film we took in 70s, Ron has just put on a dvd, Shame no sound.
All The Best, Bill.

 

[aluminiumbronze]

You can make the 8” drums a lot lighter using an alloy back plate as per prevwar TTR, saves around 900 grams per brake drum

 

[hadronuk]

100% of the flex in the system is the shoe bending.
Why should a steel plate flex when the load is applied at one edge ?

Because it isn't applied at one edge?
My statement was admittedly rather dogmatic. The finned 8" drum probably distorts appreciably less than my Rapide drums did, so that also reduces lost motion.
But if "100% of the flex in the system is the shoe bending", why is the standard shoe super flexible and the 8" shoe highly rigid when they have such a similar design?