Author Topic: Rear Brake Operating Arm - 1961 Swinging Arm  (Read 704 times)

Offline PatM20

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Rear Brake Operating Arm - 1961 Swinging Arm
« on: 22.03. 2018 10:23 »
Hi

Should the brake operating arm point upwards i.e. the cable running above the swinging arm, or downwards with the cable running below.

I have seen pictures with either routing and was wondering which was best.

Regards

Pat

Online Angus

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #1 on: 22.03. 2018 10:31 »
Hi

They are different Hubs. So it depends on what you have. I would like an upwards one as I think they look better.
1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Offline PatM20

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #2 on: 22.03. 2018 11:45 »
Thanks for this.

I will try and upload a picture.

Regards

Pat

Offline ellis

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #3 on: 22.03. 2018 14:37 »
Hi patM20.  Mine runs below the swing arm. That was how it was fitted when I bought it.  ( 1960 A10 )

ELLIS

Offline RogerSB

  • 1960 Golden Flash, Plymouth, Devon, England
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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #4 on: 22.03. 2018 22:04 »
Here's a pic of mine. Jan 1960 unrestored Golden Flash. I believe BSA changed it on earlier models from up to down - whichever, the run of the cable needs to line up nicely with the cable lug welded on the frame.

1960 Golden Flash

Offline PatM20

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #5 on: 23.03. 2018 08:19 »
Thanks for all your responses.

I have worked out that it only fits one way and that is down.

Regards

Pat

Offline RoyC

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #6 on: 23.03. 2018 08:37 »
Thanks for all your responses.

I have worked out that it only fits one way and that is down.

Regards

Pat
Here's a pic when mine was cable operated.
My bike is a 1958 A7SS
Staffordshire UK

Offline PatM20

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #7 on: 23.03. 2018 08:45 »
Hi Roy

I couldn't see on the picture where the torque arm is fitted.

I thought that the torque arm was fitted to the cable adjuster mounting.

Regards

Pat

Offline RoyC

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #8 on: 23.03. 2018 09:00 »
Hi Roy

I couldn't see on the picture where the torque arm is fitted.

I thought that the torque arm was fitted to the cable adjuster mounting.

Regards

Pat

Torque arm marked in red.
My bike is a 1958 A7SS
Staffordshire UK

Offline duTch

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #9 on: 23.03. 2018 09:06 »
  For what it's worth (and out of my realm), I was led to believe that the Rigid models had the rod on the upside and it worked better than the subsequent under-slung rod brakes...due to the way the cams activate the leading/trailing shoes.  *dunno*

 I tried it on my Plunger Flacket (Flash-Rocket), but the way the suspension operates it rendered it insane, as I expect would happen with a rod operated Swing-arm brake. A cable operated brake *may* work better on the top... more*dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline PatM20

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #10 on: 23.03. 2018 09:57 »
My brake plate only has three machined holes: one for the cam/brake arm, second for the pin at the other side of the shoes, third for the cable adjustment housing.

Looks like I can only fit it down, with the torque arm attached to the cable adjustment housing.

Regards

Pat

Offline duTch

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #11 on: 23.03. 2018 10:04 »

 Yeah- just sayin',  it's waaay outta my league
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #12 on: 23.03. 2018 10:15 »
As I said there are two different rear full width hubs. The bottom pull has three holes lever, pin and adjuster torque arm in one at the bottom. The top pull has an extra hole at the top for the adjuster. I think it was only about for one year. See pic below of a top puller
1961 A7 since 1976
1960 A10 Gold Flash Super Profile Bike
1958 Matchless G80 Project
1952 Norton Model 7 Plunger
1950 T100

Offline KiwiGF

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #13 on: 23.03. 2018 11:28 »
  For what it's worth (and out of my realm), I was led to believe that the Rigid models had the rod on the upside and it worked better than the subsequent under-slung rod brakes...due to the way the cams activate the leading/trailing shoes.  *dunno*

 I tried it on my Plunger Flacket (Flash-Rocket), but the way the suspension operates it rendered it insane, as I expect would happen with a rod operated Swing-arm brake. A cable operated brake *may* work better on the top... more*dunno*

Like you Dutch I really struggled that with a SLS type brake there is the “leading shoe should contact first theory” and diagrams on the net of this theory did not help me. I eventually figured it out (I think).

What bugged me most was reading that BSA racers commonly “reversed” brake levers to improve braking, which seems such a simple mod it makes you wonder why BSA did not get it right as standard!

This probably won’t make sense but I’ll give it a go!

it’s a fact that the cam contact point with each shoe happens such that one shoe contact point is further away from the spindle than the other. Ideally the setup of the brake lever should result in the leading shoe being contacted by the part of the cam that is nearest the spindle.

The reason for this is that the shoe with the cam contact point nearest the spindle moves outwards more than the other shoe, and you want the leading shoe to move more, and so contact first.

If the trailing shoe moves out further than the leading shoe then it will contact the drum first and potentially stop the cam moving, and hence stop the leading shoe even touching the drum.

It is generally understood that the leading shoe provides (say) 75% of the braking force, the trailing shoe only 25%, so if the trailing shoe contacts first then you are missing out on up to 75% of your braking power.

I did an experiment where (on a pretty poor 8” front brake) I built up the leading shoe flat cam bearing face by about 1mm with some weld, this meant the leading shoe HAD to contact the drum first even though the brake arm was the wrong way round on this particular brake set up. The result was a brake that really worked well. So my next job is to reverse the brake arm because I now know from my experiment that doing that will make the brake work better and stay working better, whereas with the experimental shoe mod the leading shoe will wear and the brake return to being rubbish.

My apologies if anyone reads this and it still does not help. I tried!

New Zealand

1956 A10 Golden Flash  (1st finished project)
1949 B31 rigid “400cc”  (2nd finished project)
1968 B44 Victor Special (3rd finished project)
2001 GL1800 Goldwing, well, the wife likes it
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Offline PatM20

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Re: Rear Brake Operating Arm - 1961 Swinging Arm
« Reply #14 on: 24.03. 2018 09:04 »
Sorry to keep this thread running, but I expected the lining on my brake shoes to be "offset" i.e. the gaps from the end of the lining to the pivot points of the shoe to be longer one end when compared to the other end of the shoe.

However, they seem to be of equal distance. Which in my mind (small and getting smaller) means that the leading shoe wont really bite.