The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Gavin on 07.11. 2009 13:10

Title: Brake lever
Post by: Gavin on 07.11. 2009 13:10
I am getting pretty close to finally getting my 51 A10 plunger on the road.... but stopping it would also seem like a good thing.... when I drop the lever from the brake housing down a notch i can't get enogh length to connect the cable. when i bring the lever up a notch i have a cable that is now too long. since i can't find the middle ground, as it were, i am wondering if i am missing an adjuster on the brake lever on the handlebars? Can anyone supply me with a photo of their brake lever please? and or let me know if 51 Plungers had the adjuster.... or if there is another way to resolve this challenge. i have included a photo of the current lever. hope it helps. Thanks.
Title: Re: Brake lever
Post by: bsa-bill on 07.11. 2009 13:21
Hi Gavin
I'm not familiar with the plunger brake so this might be rubbish, - some levers on brake plates can give a setting half way if they are turned.
Maybe not describing this very well but the square hole in the lever is offset compared to the hole in the end for the clevis pin.
Probably way off the mark here but you never know.

All the best - Bill
Title: Re: Brake lever
Post by: Rusty nuts on 07.11. 2009 14:33
Have you tried fitting a ferrule between lever & cable? This will take up some slack.
To give some extra length you could detach brake cable & remove locknut from the bottom thumbwheel adjuster.
The problem with this is you end up having to adjust the brake all the time as the locknut ain't there & the adjuster moves a fair bit from pressure/vibration etc.
If you forget to check regularly it is possible to discover no front brake when you need it most!
Once linings have worn/cable stretched you can re fit locknut.

Rusty
Title: Re: Brake lever
Post by: a10gf on 07.11. 2009 15:17
(If I did get the question right...) You can't get any correct cable length using the cable adjuster? or is the adjuster missing ? The standard adjuster fitted on the brake plate provides substantial adjustment of cable length.

If the cable is too short, move the operating arm on the brake plate up a notch, if too long, move it down, and do any finetuning with the cable adjuster. If totally out of spec, get a new cable of a more appropriate length.
Title: Re: Brake lever
Post by: Rusty nuts on 07.11. 2009 16:02
There should not be an adjuster on the lever on the handlebar. There should be an adjuster on the brake plate, as in E's pic
Is that what you have?

when fitting dont try to force nipple over operating toggle end in situ, remove clevis pin/screw whichever you have & fit nipple & replace.

You could fit a different h/bar lever with an adjuster but there should be no need to have adjusters both ends unless something is wrong with the cable/drum/linings.
The most usual cause is knackered linings or drum has been skimmed without fitting o/s linings.
Title: Re: Brake lever
Post by: MikeN on 07.11. 2009 22:53
For best efficiency (assuming new linings) and maximum brake shoe life.You want to obtain an angle of about 70-80 degrees between your brake lever and the cable.
If you cant do this with what you have then you need to obtain or make a new cable.
  When applied the lever should pull up to nearly 90 deg.After this point braking efficiency will fall off.
Mike
Title: Re: Brake lever
Post by: Gavin on 09.11. 2009 14:33
Thanks for helping me re think the issue. I decided to use part of an old cable (Throttle I suspect) and made up an adjuster at the lever end. As the brake pads were new 20 years ago and probably swollen a little with time i thought this would give me a safe enough option to at least test the bike with. (as I haven't had it running for over 30 years.) If this is not satisfactory i think I"ll go for a different cable. here's 2 more pix to show the end result.
Title: Re: Brake lever
Post by: groily on 09.11. 2009 16:51
I'd get another cable, as with the obtuse angle at the bottom, it'll never be as good as you want. I had exactly the same problem with my s/arm bike when I got it, and in the end there was nowt for it but to get the right bit. Difference in operation was well worth it.
A better temporary bodge would be to make an extension clevis link to go from the lower lever to the bottom of the cable. Maintains the straight line of the Pull, allows the bottom lever to be put back to the correct acute angle to the cable line and saves having to use cheesy distance pieces.
But probably easier to get a new one to complete what looks like a very pretty beast.
Title: Re: Brake lever
Post by: beezalex on 09.11. 2009 19:05
Did you try flipping the lever over to obtain the same angle that's shown in the pic above.  With the lever in the position you are showing, an already marginal brake will probably be horrid.
Title: Re: Brake lever
Post by: a10gf on 09.11. 2009 19:28
Indeed, beezalex.

Gavin, as mentioned above, get the lever one notch or more down at the drum plate side to get the angle within a decent spec., then get rid of the adjuster at the brake lever, adjust the cable at the drum side. On your pic the lever is far past what should already be absolute max possible braking, and as beezalex points out, the loss in braking power will be substantial.

And check the shoe cam action, should not move to a too steep angle (against it's brake shoe contact surfaces) before max braking occurs.
Title: Re: Brake lever
Post by: Rocket Racer on 10.11. 2009 08:53
Not that it affects the brake, but the bolt on the brake plate to the brake stay usually sits behind the front mudguard stay, where as your brake plate seems to be rotated anti clockwise about 10 degrees -Its as if your brake stay is too short. This certainly makes your brake lever and cable angles all look a bit odd. unlike the other image shown that is correct but doesnt show the brake stay relative to the mudguard stay. Persevere!
Title: Re: Brake lever
Post by: Brian on 10.11. 2009 09:24
I reckon Rocket Racer has hit on the problem Gavin, you need the correct brake stay and then start again with cables etc.
Title: Re: Brake lever
Post by: Gavin on 10.11. 2009 15:08
Yep I think Rocker racer and Brian have given me something fresh to think about after taking on baord the other helpful comments and concerns. can somone with a plunger frame measure the length of their brake stay and let me know what that is please? as I've been rebuilding the bike I keep coming accorss swinging arm bits that have been there since I took it on..... as I am not aware of how many more parts are swining arm, this may be another one of the several I have discovered so far. MAybe i have a Swinging arm cable as well??

but for now if i could have the measurement of the stay on another plunger frame that would help me heaps. Thanks.
Title: Re: Brake lever
Post by: bsa-bill on 10.11. 2009 15:52
I'm not sure rotating the brake plate in relation to the fork is going to alter anything.
Gavin could you say if you have flipped the lever (turn it inside out) as suggested by myself and Beezalex ?

All the best - Bill
Title: Re: Brake lever
Post by: Gavin on 10.11. 2009 17:07
Bill I must admit i have thunked about it, and you will imagine that I am so dense that light has to bend around me, but I can't figure how to flip the lever. Can you explain how to achieve this? After reading your first post here, I did take another look at the lever and found that I could gain about 1/16inch by aligning both sides, one edge of the split in the lever was not quite in line with the other. Now both "Faces" of the lever sit flush on the stop where the lever rests against the handle bar arm.
Title: Re: Brake lever
Post by: muskrat on 10.11. 2009 18:30
G'day Gavin,
                 they mean the lever on the brake plate.
Cheers
Title: Re: Brake lever
Post by: bsa-bill on 10.11. 2009 18:35
Ah sorry Gavin, my fault, for lever read brake arm.

All the best - Bill
Title: Re: Brake lever
Post by: Brian on 10.11. 2009 22:08
Gavin, here is a drawing of the correct brake stay strap. I'm no draftsman but hopefully you can make sense of it. If you dont want to make one I am sure C@D's or one of the parts suppliers would have one.

Dont alter any brake arms or anything until you get the correct one of these fitted. Once you have this sorted put the brake arm on so that it is at about 225 degrees (half way between pointing straight down and level). You will probably need to adjust the point that the adjuster goes through so it points directly at the end of the brake lever (loosen the nut and turn it). You only need the adjuster at the bottom, none at the top.

Brian.
Title: Re: Brake lever
Post by: Rocket Racer on 11.11. 2009 06:29
as per A10GF's image but taken to show the brake stay better. These are actually on a plunger B series, but the same...
Title: Re: Brake lever
Post by: Gavin on 11.11. 2009 06:46
Thanks for all the info so far. I have fallen about the floor laughing at myself. Once I get over that I'll try fliping the brake arm Bill. Thanks for the dimensions Brian. The strut on my brake is an inch shorter than your measurments. So I am Guessing that I might once again have found another part that was on the bike when i originally got it, and am now finding it's not a plunger part, but could well be from a swinging arm. Thanks for the eagle eyes that can spot that sort of detail.
Title: Re: Brake lever
Post by: Gavin on 12.11. 2009 14:50
Bill, the flip certainly helps. But I am sure my braking will be marginal at best till I give it a chance to bed in. I have been able to remove the extra adjuster on the lever, and some time soon I'll set about getting a proper length brace for the brake. but i cannot see how that will improve anything much, other than the 2 bolts taking the brake load to the front fork, wher mine has only one at present. yes i can see that all the angles will change in appearance, but as the brake adjustment and the brake lever base are in exactly the same relative location to each other, it won't matter what place they line up on the "Clock" as it were... well that's how i see it. now to see if i need an award for bravery for daring to think this way... hear from you soon. thanks.
Title: Re: Brake lever
Post by: bsa-bill on 12.11. 2009 16:48
Good, I'm having a few front brake problems myself so have been through some of these moves including cutting a inch of an expensive cable ( a65 cable with brake   incorporated) only to find once everything has settled I need the inch of cable back -  *red*

All the best - Bill
Title: Re: Brake lever
Post by: MikeN on 12.11. 2009 21:51
yes i can see that all the angles will change in appearance, but as the brake adjustment and the brake lever base are in exactly the same relative location to each other, it won't matter what place they line up on the "Clock" as it were... well that's how i see it.

Gavin,
 By changing the length of the torque arm (brace)the brake plate will revolve one way or the other. As you say this will not change the relative location of anything attatched to the brake plate.But it definately WILL change the angle that your brake cable meets the operating lever (which was way out in your photo to begin with).This is most important to get the best from your brake.
However , in your case fitting the correct longer torque arm wont benefit you (it might make it worse)unless you have the correct length cable . As I said earlier you need to obtain an angle of about 80 degrees between cable and operating lever to get the maximum mechanical advantage.
Mike
Title: Re: Brake lever
Post by: Brian on 13.11. 2009 10:39
Here is the bit you need plus some extras if your interested Gavin.

http://cgi.ebay.com.au/BSA-PLUNGER-A10-FRONT-BRAKE-PARTS_W0QQitemZ400083587545QQcmdZViewItemQQptZUK_Motorcycle_Parts?hash=item5d26d711d9
Title: Re: Brake lever
Post by: Gavin on 13.11. 2009 14:14
Thanks Brian. after a very slow start on the net tonight i have finally tracked a cheaper new one down from Dragnfly.

Mike, don't stress too much. I Have had the bike apart for about 30 years, and just rode it for the first time ever tonight, round the back yard. there's no way I'm going to need huge braking power before the correct part arrives and in the meanwhile i'll get a chance to let things bed in a bit. i suspect the brake pads have swollen a bit, if that's possible. had them relined 20 odd years back, and they have been sitting in the shed since. so i'm not going to go a breakneck speed till i feel confident on the old girl, and have had a chance to get it sorted. but this is the long awaited starting point for the road testing aspects. so your comments are all good grist for a very slow working novice here.