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+--- Thread: BRAKES WHAT'S NORMAL (/showthread.php?tid=2267)
RE: BRAKES WHAT'S NORMAL - Dave Mann - 05-03-2019
Hedd just check the radius arm nuts are tight and nothing has moved. Some years ago going to Woolaton Park Sue did and emergency stop after which the brakes weren't so good and pulled to the nearside. It took a bit of head scratching before I realised the nearside radius arm had moved in the axle beam.
While today I popped into town and thought I should give the brakes a quick check, that was before someone pulled out in front of me and promptly stopped to turn right. The Seven surprised me and stopped dead in it's own length from 20mph accompanied by the squeal of tyres behind me.
RE: BRAKES WHAT'S NORMAL - JonE - 05-03-2019
sorry, Bill, I'm going to add my next update without being able to address yours, other than to say that in some of the old threads I've found (Bob questioning I think), there seems to be a lot on whether the brakes go back to their cam plates, or whether they remain 'on cam' i.e. are still under tension at pedal. I'm not sure what is actually advised now but that must affect available travel.
I've just been faffing with (rear, uncoupled, standard) brakes to address the levers and I am now unsure, having come away from the car concluding:
1. In order for cotter nuts to face to the back, I'm presuming that makes the levers handed.
2. And that that is the only thing that makes them handed?
3. I can't work out how which way the cotter goes in can get an extra 5 degrees of adjustability, when the angles of the cotter surface is 90 degrees to the lever.
4. there doesn't seem to be much ability to have a "down and in" short lever sitting further back from the vertically down position, as the axle case gets in the way within an 1" of movement?
5. And with two different cams in hand to try, I couldn't do anything better than get the lever pointing absolutely vertically down when the shoes are wholly back in their cams, whereas I really wanted it right back on the axle to allow take up of slack on actuation.
Have I overlooked something really major? As it is, I'm now thinking that the shoes need to be absolutely finely adjusted in order to make use of the vertical downward lever position... but I can't imagine how that could be maintained as they wear without reshimming?
RE: BRAKES WHAT'S NORMAL - Bob Culver - 05-03-2019
Hi Jon and others
The flat on the cotter aligns with the flat on the cam spindle. The hole in the lever aligns with the body of the cotter, which is at an angle to the flat.The holes on the levers are square to the body of the lever so not handed, although the twist at the front introduces l and r. Depending on which way cotter inserted, the shank of the lever is less or more than square to the cam flat
The best advice is to select for optimum lever positon operated. (With Girling this does not change much, and should be close to right angle.)
The experts will be able to confirm if they so deign, but I suspect the rear levers are further forward on pre Girling Rubys to accommodate longer levers without the axle housing getting in way. (a slightly shorter cable is listed). It is presumably why many cars are seen with long levers fitted pointing up (when the cable angle is all wrong and levers liable to strike the body and be damaged)
Very early cars had very short levers. I wondered if this was to allow cams to be fully off for all states of wear. It was generally recognised that unreasonable later, esp with the long Ruby arms.
With absolutely unkinked cables, bedded shoes, uncoupled rears, cable length adjusted equally, would be intersting just how much pedal give after shoes contact.
Although disconcerting, esp to modern drivers, a long pedal travel ensures brakes do not rub, esp with varying axle ride positons; need every mousepower with Sevens
Cams are easliy made and may not have been readily avialable in the past. May explain some of the odd angles..
RE: BRAKES WHAT'S NORMAL - AustinWood - 05-03-2019
The brake levers are not handed, the cotter hole goes straight through. The flat on the cam is at the angle suitable for the side of the car to which it is fitted which means they are handed. This is because the rear brake pivot is at an angle to the vertical line through the hub centre, clearly seen on your picture.
However the flat face on the cotter pin IS angled. When it's inserted it makes the lever 'lean' by that angle. If put in from the other side the lever will 'lean' the same amount but the other way. Very simple to check out on the car or on a cam and lever off the car, just try it!
The effect of the cotter is very small compared with the angle of the cam.
Your brake cams are on the wrong side and need to be swapped round before you do anything else.
With new linings, unworn cams, unworn heels on the shoes, unworn drums and the cotter the right way the lever will be at the correct angle. As things wear the lever angle will change. Eventually needing new parts, probably linings, or shimming of the cam.
Front brakes are different because the brake cams are directly on the axle vertical centre line. Thus the front cams are not handed and the cotter pin direction has more importance.
This applies to Austin brakes. Girling are different.
RE: BRAKES WHAT'S NORMAL - JonE - 05-03-2019
(05-03-2019, 08:06 PM)Bob Culver Wrote: Depending on which way cotter inserted, the shank of the lever is less or more than square to the cam flat
bob - sorry, I've got to go right back to naive questions. Part of my problem may be non-standard parts so I can't interpret instructions.
The cotter would only go in from one side. So hence I thought I'd need to swap the lever from the other side to address "nuts to the back".
I noticed my cotter pins took a 10mm spanner. Is it possible that a cotter could be "wrong", if it fits and seems to work as per other cotters I have used on track rod arms and stuff?
[I remember looking through the lever cotter hole with cam in place and seeing it was completely clear through, so perhaps that's the problem if someone has altered the cam so a generic cotter is just a retainer]
This is the sight that linked to the lever being pictured in my earlier post sitting at about 4 o clock resting as looking at the rear of the backplate. With a turn of brass shim on the pivot, I am now at 5 o clock... which of course will be 4 o'c by the time the brakes apply so still rubbish.
and thanks Jim - will print this off for when next to car...
RE: BRAKES WHAT'S NORMAL - Ruairidh Dunford - 05-03-2019
(05-03-2019, 08:16 PM)AustinWood Wrote: Front brakes are different because the brake cams are directly on the axle vertical centre line. Thus the front cams are not handed and the cotter pin direction has more importance.
That's interesting, I had always been under the impression that Austin front cams are handed in exactly the same way that the rears are? Are the fronts distinct from the rears Jim?
RE: BRAKES WHAT'S NORMAL - AustinWood - 05-03-2019
Now you mention it I'm not so sure! However I'm a bit puzzled. Looking on A7Components catalogue only pairs are listed, not differentiated between front and back. So you must be right.
All four levers should be approximately vertical when the brakes are applied. To achieve this the front cams are probably set at a different angle side to side to bring them slightly forward of vertical at rest.
However the front cams are directly below the king pin while the rears are at an angle of about 45 degrees.
I would have thought that the front cams are at an angle close to 90 degrees and the rears close to 45 degrees.
I'm house sitting for a friend at the moment otherwise I'd go and have a look at it.
I seem to be confusing the issue!!
RE: BRAKES WHAT'S NORMAL - Tony Press - 06-03-2019
Jon,
With the brake cam set at the angle shown in your above picture you have already lost some of your best braking effort as with brake levers past vertical or right angles to the cable pull (the effective lever is shorter as discussed at some length in a rather boring earlier discussion).
The brake cams are handed offside to nearside (but not front to back as listed in the modern spare parts lists from suppliers) and must be fitted to produce the correct angle in the brake levers - rearward facing at the back forward facing at the front.
The cotter slope can contribute here but as I noted in an earlier post with my 'long' cotter and return spring the front cotter must be in 'backwards'.
Talking of cotters - I found that a recent batch of brake lever cotters (5/16" dia) in Club spares were wrongly made with the 1/4" BSW threaded portion central instead of offset- as all early bike users will know this is totally wrong and doesn't allow for the necessary cotter pin 'ramp'. Beware and check if buying new cotters.
The short brake levers are not shown as being handed in the Austin 7 Spares catalogues or modern spares lists but I am sure I have seen a nut flat machined on the side of some levers (none to hand to check) making them handed ?
RE: BRAKES WHAT'S NORMAL - Bob Culver - 06-03-2019
While we are all splitting hairs, the cam is most efffective just before it wedges open. A large angular movement then produces very small shoe movement so the leverage is great. But normally at that position the lever is at an inefficient angle which counters. (It is vital cams cannot reach the locked state. After braking all wheels release except the locked one and the result can be exciting. I have seen many primitive shimming arrangements which, if failed, would risk locking
RE: BRAKES WHAT'S NORMAL - JonE - 06-03-2019
Thanks Tony. I'm not going mad. I think I may have an unramped cotter and a (consequently) handed short lever!
What worries me is that I had a distinct pair of cams (one on car and one spare which happened to be different) and that I haven't yet managed to get them into a position which is essentially back against the axle tube case. I will return...
Bob - what would be useful is to hear what shimming is absolutely acceptable and what is not.
As I see it, the cam end of shoes can be amended only by solid metal which is screwed or bonded down onto the shoe, or thinner shim under that solid outer.
At the pivot end, is a length of brass shim wrapped around the pivot once, twice or thrice safe?