In an article about a Dominator Deluxe the Owner got the Single Leading Shoe unit it had converted to Twin Leading Shoe with a little engineering acumen. I think the article said the original Front Brake Plate post 1956 type had been used, whether strengthening ribs had been added inside of the plate I don't know, there was hint of a follow up article, but I never could find reference to it.
A British guy also converted a 7 1/2"/ 190 mm" BSA Gold Star brake from Single Leading Shoe to Twin Leading Shoe, tested examples of brake efficiency stated that in relatively front brake efficiency went up by about 27 % in effective stopping power.
Anyone out there modified their front drum brake?
Not I, but it might be worth considering that he big problem with drum brakes as opposed to discs is not how effective they are on first application, but how good they are at getting rid of heat. And for that a TLS and SLS are much the same as each other, and as a four leading shoe brake. My Dommie has TLS but many owners and old reports say the SLS is excellent anyway. I am quite convinced that our problem is with asbestos free linings. Are any of the ones supplied for drim brakes branded products with some kind of performance worth advertising and worth paying for? My 16H brakes (which are old and probably asbestos) are immeasurably better than those on my Inter, which are mechanically almost identical but use modern materials.
I have wondered about the new materials and how effective they are.
Improved cooling can be catered for quite easily, by hole drilling plus drainage facilitated. Gold plating intensifies heat transference! Plus ribbed drums helps too.
Remember, Bacon -slicer cooling discs, i was too young!
Maybe I should replace them...period pieces. These were on the Inter about 30 years ago when its PO acquired it. I have them in a box...
In response to your thread under Norton's general of the 23/11/2017 front brake SLS to TLS and beyond I converted a Norton SLS to TLS ( see my posts 19/8/2018 ) This is on page eight of Norton's general.
I have since become involved in other projects and my friends ES2 has been sold so testing has ceased. I did find that the Triumph brake shoes supplied brand new came from China ( not good ). I have since had them relined with quality material. I now have to get them sized to the drum as I ordered oversized linings. Once this is done I will have to source a test bike.At the moment I am involved with restoring a 1950 Model 7 plus many ongoing projects.
You probably failed to notice my posts as the thread was by then "stale".
Cheers Andrew i will look the reference up!
That was me too, when I rejoned they gave me a new number, I had left my Norton stuff @ Anna's and rescued it from there as Developers were looking at the building where it was stored, so even though my Workshop garage wasn't ready, I brought it all down to Kent and started working on it, 1st May.
I always slightly modified my British stuff, to me it made them more interesting and personal.
I have a Conical hub brake plate and shoes and I read somewhere someone had modified one to fit a Norton hub, it is as good as the twin-leading shoe BSA brake from 1968-1970, which was a much better brake than the Norton TLS fitted to earlier Commandos. The Conical hub brake can be made even more effective with longer activation levers, the central axle hole in the BSA unit seems to be 3/4 of an inch and the Norton 11/8 ths, the circular centre ribbing on the plate on the Norton 2" 3/8 the,BSA 2" 1/2, but the plates strengthening ribs are much more defined. The Norton brake plate & shoes depth are 1 11/16 ths, BSA 1" 3/4 so the Brake plate unit stands slightly proud Then of course the next job would be modifying the torque fixing and cable activation run.
Probably the easiest fix is to have a spacer fabricated to fit on the Norton hub rim to facilitate the increased depth of the BSA unit, but overall you would then have the best TLS ever made by an English factory!
The other way is to the Vincent way two independent SLS drums back to back mirroring each other!
They say the SLS Velocette 7 1/2 brake was a good unit too, but drum width makes it incompatible.
Norton should have had a TLS unit option by 1960 when the 650 Manxman appeared, followed shortly after by 650 SS and the mighty Atlas .I think it was remiss of them not to do so.
Good luck with your brake conversion John. I went down the Vincent path using two pre 1955 Norton SLS. If you are interested read my article " the guru and the grasshopper in RH 335 Nov. 2015 page 28.
Perhaps the solution for making Drum brakes work better it to have the drum lined with some sort of material, to help the modern material shoes grip more!
John; I came across this picture of the TLS brake on my plunger Norton of 1950 vintage. Externally it looked the same as a Magnesium plate SLS of the period but the added actuator plate and dual pivots added. Another Jo Craig experiment???
Maybe it will help with a new idea.
It makes me wonder if this is where Laverda got the idea for their brakes that didn't have cams, but cranks and plates to move the shoes? Note the bronze bushes where the shoes and links pivot!
The Laverda design allows the two levers to move in opposite directions. So the cable can pinch one against the other, and does not need a tie rod. BMW do the same thing. They both have to have the cam pivots at different radii from the wheel spindle. If you did it with the Norton brake, the cams would each be pushing at different radii from the spindle, so the self-servo action would be different on each shoe. The cranks will have less friction than cams, so that should put more force on the shoes.
There was a vogue for replacing the cams with hydraulic cylinders from BMC minis at one time. Are any of those still on the road? Again, less friction.
John & George thanks for the input, interesting ideas and mechanisms, I just parted with money, to a friend for a collection of fifteen old motorcycle books mainly 30s & 40s and up to the 60s, covering BSA Twins and the Gold Star, Triumph, Ariel and a Vincent Rider's Handbook and a 1930s Motorcycle manual and there are some pretty exotic looking stuff in there in brake designs and mechanisms, I reckon the 30s & 40 were possibly the most exciting decades for development and design change and introduction.
In a book on the BRM, Girling, featured a Three-shoe drum brake design, imagine that!
Apparently three shoes have a really good contact surface effect.
Also seen some drums I think Alfa Romeo automotive brakes, with intricate fin designs for cooling, before the ugly disc units crept in!
If you go back to Leslie Howard's thread of 2011 " 7 inch brake weakness, a fix " you will realize this has all been mulled over before. The Norton single leader front drum brake can be made to work effectively. It just needs careful setting up. This is covered in the above thread.
I built up a double sided S L S Norton front brake which was very good but I was disappointed in the lack of servo effect. I bit the bullet and removed about 3 inches of brake lining from each of the trailing shoes, working from the cam end back towards the pivot point. Wow, what a difference that made.
In drum brakes there are very strong forces which cause flexing of the brake shoes and pivot points. The removal of trailing shoe material causes the trailing shoe to flex even more allowing more pressure to be applied to the leading shoe. This also causes the trailing shoe wear to out pace the leading shoe wear rate.
At least S L S brakes don't lock up. If you are an ageing rider like me the last thing you want is a brake that locks up sending you sliding down the road. You just need brakes that are adequate for your style of riding. Like many of my generation I don't brake hard, I just want to keep moving forward.
Some engineered solutions
Alfa Romeo hub;
Norton or BSA hub;
TLS Nor-Jawa build, Feather-bed.
BSA Gold Star owners seem to be at the forefront of modifying their 190 mm (7 1/2 inch), SLS, brakes.
There is an Owner out there, that put 2 SLS brake hubs back-to back, like Vincent, definitely on their "V" twins, but not sure if they fitted it to the Comet). I will see if I can find anymore information about them. Anyway, he was very pleased with the end result and the brakes, were much improved on the standard SLS BSA fitment.
Yes, Andrew you are right, any improvement needs to be in a progressive braking way rather than grabby, making the bike skid prone!
A better photo of the modified Norton Dominator SLS to TLS.