Spot on and I am about to fit my Schmitz brake BUT..... the last softer fabric style linings with brass bits in etc I was supplied are actually a big improvement on the standard
H: Hubs, Wheels and Tyres Trevor Southwell re brakes
- Thread starter fogrider
- Start date
The story about milk float brakes (and remember floats=very high loads, steep hills and no engine braking) was related to me as AM4 now AM4 was`responsible for most racing brakes in the 60's and later I have seen Ron Kemp's flash Bramptons bent (the two tubes nearest to the lower axel casting) after a Silversone meeting and following that event he added a cross bracing. Personally I had a spring shatter in the brake from squeel (luckily Ron got me to copper wire the centre up). Now banned because of asbestos Safetec supply a 'replacement' which I have used since but with a new ROAD bike on the cards i am wondering what to use.
If I was to go away from 7" drum (and even a non rivet counter like me would hesitate) its an obvious choice to add a disc (or two) cheap and effective, Of course back in the day we tried other options.... (thats a BSA 190mm)
If I was to go away from 7" drum (and even a non rivet counter like me would hesitate) its an obvious choice to add a disc (or two) cheap and effective, Of course back in the day we tried other options.... (thats a BSA 190mm)
1mm towards centre I did put in article.
If that is done after removing shims shoe at cam end will touch drum long after pivot end has.
As regards stiffening brake plate, why ? that simply proves the load is being applied at the wrong place.
Why do aluminium brake plates (preceded by magnesium) perform better than the steel ones, I always assumed it was because they were stiffer in use.
Clevtrev, maybe I did'nt explain my idea too well, the theory was that turning the shoes , without, say, the H48 caps, and turning the pivot end of the lining somewhat under drum size, operating the cam with the H48's shims back IN ,would put the cam end in contact first, even out wear and give full contact sooner. It would have to be a small difference though and linings chamfered for the bedding in miles. The pivot's the pivot so the end result after use could be just the same ! Just a theory.
Vibrac, I'm absolutely certain that all the work involved in moving the pivots 1mm would have no change in brake performance what so-ever !
I rather think that turning oversize linings to drum size and removing any flex/sponge/etc is going to be as good as it gets. The big issue remains - what linings to select ? Sure, the woven stuff with brass wire in has lots of bite but as far as I know woven can't be turned without the weave being damaged. They don't give any real fade resistance, apparently, more suitable for lighter bikes. I enquired about that stuff, its' origin is for winch drum brakes which require lots of bite and holding power but don't need much anti-fade.
I found the Questmead receipt for the Mintex M24 equivalent - they called it 242. Expensive, but my sons' touring twin will chirp its front tyre with modern Bridgestones on it. ( If need be ). I think my B twin will be wearing it next year.
Vibrac, I'm absolutely certain that all the work involved in moving the pivots 1mm would have no change in brake performance what so-ever !
I rather think that turning oversize linings to drum size and removing any flex/sponge/etc is going to be as good as it gets. The big issue remains - what linings to select ? Sure, the woven stuff with brass wire in has lots of bite but as far as I know woven can't be turned without the weave being damaged. They don't give any real fade resistance, apparently, more suitable for lighter bikes. I enquired about that stuff, its' origin is for winch drum brakes which require lots of bite and holding power but don't need much anti-fade.
I found the Questmead receipt for the Mintex M24 equivalent - they called it 242. Expensive, but my sons' touring twin will chirp its front tyre with modern Bridgestones on it. ( If need be ). I think my B twin will be wearing it next year.
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yes fogrider that all makes sense perhaps the last comment I would make is the H48 are flimsy I have very few in my collection that are not partially buckled perhaps I should look at emulating an AMC type big headed "toadstool" insert at the end of the shoe
Use a thicker sheet steel and make your own.......On well used brake plates the cam bores wear quite badly.......this will give very poor braking as too much lost travel as the cam rotates......don't use soft modern linings, these don't really work well enough, and don't give much bite.......when arcing the oversized linings in a lathe.......actual best method is to assemble up the shoes, cam, serrated washer, brake lever, nut and washer.......then wire tie the end of the arm in the correct direction as if the brake cable was pulling on the brake lever.......this by not more than 10 mm of travel.....cut the shoe lining down till the same size as the ID of each drum.......This coupled with good linings will give a good result with near nil bed in time.......The course woven linings work well as do some of the specialised hard linings with metal impregnated through the material......with a good sharp lathe tool they will trim down to size with several cuts, not more than 8 to 10 thou per cut and not more as the material is too hard.......I always straighten the pivot pins first as these are often bent inward.......I also use the nilos bearing seals as well......the smallest ingress of grease from the bearings will render the small brake linings useless.......same, same for the speedo drive if it is pumped too full of grease. I have re done my brakes several times to get a good result not simply settling for something that seems ok, but was better before.........Only trouble with hard linings is they can tend to get noisy/squeeling after some time.......The right material and machined to suit each drum is the best way.
Two good posts above, the H48's really do seem to wear easily. I made some in a thicker stainless steel, they take some shaping and remaining dead flat, but seem worth the extra effort. One pair of shoes I purchased S/H had the feet of the shoes bare and with lots of ally seemingly filed off the feet. In the end, I worked out how thick the feet should be (with H48's on ) then tapped threads and screwed 1/8" thick caps on with csk screws. It saved the shoes and is working fine, much firmer surface.
I have had to re-align a few pivot pins, 2 were even loose, and the 2mm stiffening plate , again csk screwed on, ( 1" centres ) helps keep them in line and really does seem to help reducing sponge, needs doing before turning the linings to drum size.
In looking into the issue of pivots moving 1mm, I drew the assy up , actual size. I could see that moving the pivots 5mm (ish ) towards the hub centre would make a difference but only in self servo effect. Always a danger of grab though. What did come to light, in basic design, the centre of the linings should preferably be at 90 deg from a line between the shoe pivot and the centre of the cam. To meet that, it seems the linings would need to be nearer the cam by around 18mm. I might draw it up at a larger scale to check that, but it's very visible.
A local friend is an ally welder, I'll ask him to weld the top end "dips" up and have some linings bonded further up. A job for the spring, the result should be interesting !
I have had to re-align a few pivot pins, 2 were even loose, and the 2mm stiffening plate , again csk screwed on, ( 1" centres ) helps keep them in line and really does seem to help reducing sponge, needs doing before turning the linings to drum size.
In looking into the issue of pivots moving 1mm, I drew the assy up , actual size. I could see that moving the pivots 5mm (ish ) towards the hub centre would make a difference but only in self servo effect. Always a danger of grab though. What did come to light, in basic design, the centre of the linings should preferably be at 90 deg from a line between the shoe pivot and the centre of the cam. To meet that, it seems the linings would need to be nearer the cam by around 18mm. I might draw it up at a larger scale to check that, but it's very visible.
A local friend is an ally welder, I'll ask him to weld the top end "dips" up and have some linings bonded further up. A job for the spring, the result should be interesting !
I would guess that moving the pivots would simply allow the linings to stay thicker as you arc the linings near the pivot. Carleton Palmer had this problem where he found that after he arced his linings most of the thickness near the pivot was gone, meaning that the linings looked "worn". I did not have this problem, so I assumed there was some variation due to the manufacturing tolerances. I do not know if the difference in the pivot position would affect the performance of the brake in terms of the difference in the shoe geometry. In general, I have assumed that the pivot position only made a difference in replacement and maintenance rather than performance.
The Vincent shoes have "dips" to create a 90-degree arc of shoe lining to make contact with the drum. Theoretically, these contact angles determine the performance of the brake. Theoretically, they make the performance better, but considering how poorly the brakes function, I can understand why experimenting is appealing.
The "extended lining" lads seem to fall into two camps. Some love it and have been using extended linings for years. Some, who tried it, like Carleton Palmer said the brakes became unresponsive and sluggish. The Ferodo engineers are in the latter camp. They say that as the lining is extended to the pivots and cams you end up using the lining in the least useful place. That place is where there is the least amount of force of the shoe on the drum. The highest force of the shoe on the drum is close to the center of the lining and the force tapers off to zero as you near the pivots or the cam.
They also mention that the extended linings near the cam work with so little force on the drum that you get a "wooden" feeling when you first engage the linings. This means you have to thin the lining near the cam so the extended lining does not touch the drum first and prevent that part of the lining in the center of the shoe from touching first. One Vincent owner reported that he had to slack off his cable adjustment so much that he felt the hand lever had to move too close to the handlebar before the serious braking started.
I think the group that likes the extended linings is happy grinding the linings to make the brakes perform the way they want them to perform. This is how most racers do their shoes, by getting the whole shoe lined and then adjusting the lining by grinding.
I think Trevor's greatest contribution to the discussion of Vincent brakes was to demonstrate that the brake shoes were not designed well enough to perform properly. We have seen lots of mods through the decades. The shoes are too weak, the H48 is too soft, the brake cables are too flexible, the balance beam mount is too flexible, the brake plates are too flexible, and the front forks seize when the front brake is applied. Other than that, they are pretty good.
David
The Vincent shoes have "dips" to create a 90-degree arc of shoe lining to make contact with the drum. Theoretically, these contact angles determine the performance of the brake. Theoretically, they make the performance better, but considering how poorly the brakes function, I can understand why experimenting is appealing.
The "extended lining" lads seem to fall into two camps. Some love it and have been using extended linings for years. Some, who tried it, like Carleton Palmer said the brakes became unresponsive and sluggish. The Ferodo engineers are in the latter camp. They say that as the lining is extended to the pivots and cams you end up using the lining in the least useful place. That place is where there is the least amount of force of the shoe on the drum. The highest force of the shoe on the drum is close to the center of the lining and the force tapers off to zero as you near the pivots or the cam.
They also mention that the extended linings near the cam work with so little force on the drum that you get a "wooden" feeling when you first engage the linings. This means you have to thin the lining near the cam so the extended lining does not touch the drum first and prevent that part of the lining in the center of the shoe from touching first. One Vincent owner reported that he had to slack off his cable adjustment so much that he felt the hand lever had to move too close to the handlebar before the serious braking started.
I think the group that likes the extended linings is happy grinding the linings to make the brakes perform the way they want them to perform. This is how most racers do their shoes, by getting the whole shoe lined and then adjusting the lining by grinding.
I think Trevor's greatest contribution to the discussion of Vincent brakes was to demonstrate that the brake shoes were not designed well enough to perform properly. We have seen lots of mods through the decades. The shoes are too weak, the H48 is too soft, the brake cables are too flexible, the balance beam mount is too flexible, the brake plates are too flexible, and the front forks seize when the front brake is applied. Other than that, they are pretty good.
David