Hello from New Scott owner in Nottingham

[gammakeith]

I have what I assume is the Birmingham type ‘twin’ lever as mentioned. The following picture indicates what I did to effectively double the leverage. It obviously costs nothing and only took me 10 minutes to do with the pillar drill. I can easily swap back to the original leverage but at the rather obvious cost of an extra hole in the brake lever. This converted a very hard and ‘dead’ feeling lever to one that was very spongy. In hindsight a 1.5x increase in leverage would probably have been best. When my linings gets back from Saftek I’ll road test and see how both settings feel on the road.

My SOC membership pack came in the post but my first Yowl will be the December one. Thus, it appears I’m going to miss whatever comments are in the October Yowl.

Keith

[Deleted User]

It will be interesting to hear how your road testing goes when the new brake linings are fitted. Your mod is the simplest way to up the leverage and with good linings it should equal the stopping power of the Vincent balance arm.

With a doubling of force every part of the system can be expected to flex more and contribute to the spongy feel. My guess is the long twin cables particularly will experience stretching of the inners and compression of the outers. This could be reduced by fitting heavier cables. I would also look at the brake lever mounting on the bars which can often be seen to flex. Not so easy to fix that other than making sure it’s tight and fitting closely to the handlebar. The worst part of all this is that it may be possible to pull the lever right back to the bar – an MOT problem, as well as a limit on the maximum braking effect. Careful attention to the adjustments will be necessary.

[Anonymous]

There are a couple of other ways to help braking. The first is to modify or recut the cam that rotates between the two shoes to give more mechanical advantage, ie less jacking apart per degree rotation of the cam lever. As with other fixes it does increase lever travel though. The other is to dress the brake shoes as described by Roger Moss about a year ago in Yowl if my memory serves me. This when done at the correct edge will cause the shoes to self energise but of course go too far and it will be grabby. Another tip is to ensure the shoes are actually centred in the drum by holding the brake on whilst tightening the backing plate lock nuts otherwise everything else you do is a waste of time.

There is never a substitute for thinking ahead though as any two speeder owner will tell you….

Cheers,
Richard

[Deleted User]

OK get the slings and arrows ready. The chap that i worked for in the late 1950s chucked the complete shooting match under the bench [ forks wheel brakes ] and made a pair of leading link forks fitted a Velo wheel and brake bingo steered and stoped. have no recall of reg no be nice if it was still around.Regards D F .

[BRIAN MARSHALL]

Amazing how the initial post by Keith Dickinson has started this flow of responses that have gone away from the original theme!
I’ve been thinking that as Keith’s bike is far from original, with its chrome mudguards, etc., that another ‘deviation’ would be of no consequence, and the offending front brake could be kept with the machine to be recommissioned by a future owner who may wish to restore the bike to original spec., and in the meantime replace the front wheel with one that will drop straight into the Dowty forks, namely a Birmingham Scott wheel, with its much bigger and more effective brake(s)…. (later Brum forks were coil sprung, and not Oleo action, but they were based on Dowty tubes, yokes, etc.)
There are other wheels that will drop straight in, because of course other makers used Dowty forks, including Velocette, Panther, Sarolea, AJW, EMC, etc.. With a custom-made spindle, there must be lots of other brakes that could also be used.
Brian

[gammakeith]

He he, I certainly don’t mind the thread diverging at tangents! Its all great stuff to me and helps getting to know you all.

I am torn re the issue of the front brake. I am certainly aware my bike is currently not particularly stock and I am used to more modern bikes so I have come to value a good front brake on the road. Thus, knowing I have options to replace the current brake with something from a later bike is something I will certainly consider if my current efforts come to naught. Thanks Brian!

However, I do want to give the current brake a fair chance before I consign it to the ‘spares’ pile and am encouraged that not everyone finds the brake poor. My wheel bearings are modern sealed ones so I can clean up all the excessive grease every where in the backplates and restrict it to a smear on the pivots. That way my newly relined shoes should stay clean. I have rigged up a method of spinning my backplates in the lathe so I can wind the brake out (after centralisation) and turn the linings to the appropriate 6″ drum diameter. That should maximise resistance! I am intrigued at the comment from Richard regarding shaping the leading? edges to encourage self energisation. Can someone elaborate further as I cannot access that article? I could cope OK with a ‘grabby’ brake………..

Thanks,

Keith

[Eddie Shermer]

Hi Keith

I have tried contacting you re addres for Yowl back copies but bounced back.

Please could you let me know correct address

Eddie

[gammakeith]

Hi Eddie,

That would be brilliant thanks!

Email is nearly right 🙂 No ‘e’ in my email address.
Keith

[Deleted User]

Richard raises the issue of shortening the trailing shoe lining to increase brake efficiency, and quotes Roger Moss. You can find the relevant topic by searching Forum for “Single leading shoe brake” a thread started by daveherbet May 18 2009. It’s an interesting discussion and worth looking up.

I believe the idea behind this is that the trailing shoe contributes much less braking effort than the (self-energising) leading shoe. As a result it wears more slowly and eventually causes reduced contact pressure on the leading shoe. Shortening the lining at the trailing edge (cam end) of the trailing shoe causes it wear faster so that the leading shoe retains it’s efficiency longer. I don’t think it will enable the trailing shoe to self-energise – my understanding is the trailing shoe is always being pushed away from the drum. That is why they are relatively ineffective.

Richard’s advice about centring the whole assembly by applying the brake hard before clamping the backplate(s) is mandatory when setting up – also I think whenever the brake is adjusted for lining wear.

The matter of cam design is important and a big subject, brought to my attention by Ken Mercer who used to work in the brake servicing industry. There is a lot of discussion about drum brakes and cams in Graham Blighe’s book “Improving Classic Motorcycles” ( pr@lulu.com ).

[gammakeith]

I got my relined shoes back from Saftek (the softest grade) on Friday so got to work. I wound the brakes out on each backplate so just over 6″ and then turned down the linings to the exact diameter of the drum. All then reasembled with care and a near absence of grease and set off for a test drive with the brake lever in the stock position. The improvment was great but thats only compared to the previous complete lack of brake performance. I then set the brake lever to the ‘increased leverage’ position and tried again. Well, it was certainly better as the forks sank sharply on braking. However, testing was somewhat curtailed as the sinking of the forks was accompanied by a loud ‘hiss’ followed by a clunk as the forks completely collapsed 😆 As can be imagined this somewhat curtailed further testing activity. Thus, I think a fork rebuild is advised sooner rather than later as its a tad impractical to have to pump the forks up after every hard stop 🙄

Keith

[Deleted User]

Have very sparse knowledge on Dowtys i think a spring conversion is possible. Regards D F.

[BRIAN MARSHALL]

Hi Keith,
It is nearly 30 years since I had to rebuild a set of Dowty forks, but at least sets of seals are more easily obtainable now than they were then. Of course the condition of the surfaces that the seals work on is critical, and my sliders were well worn, as were the phosphor-bronze bushes that they slide in. I took my sliders to Nottingham Hard Chrome Plating and Grinding to be built up back to standard size, and they did an excellent job, with motorbike forks and hydraulic rams being their main business.They take a bit of finding, being on the Industrial Estate at Boughton, near Ollerton, in Nissen huts that used to be a WW2 P.O.W. camp ! It’s a bit of a Hell’s Kitchen sort of place, but don’t let that put you off. Phosphor-bronze offcuts, to make new bushes from, can be picked up at the Newark Autojumbles, but is EXPENSIVE !! It just so happens that there is a jumble on Sunday Nov 18th. Do check the condition of the balance pipe connecting the two sides of the forks, hidden in the hollowed-out underside of the top yoke. The special Kilner inflation valves are long obsolete, but can be replaced with a high-pressure tyre valve.Check the valve before you tear the forks apart ! Whilst there are conversions to conventional coil springs around, I believe that they have no damping, and must be like having a pogo stick on the front of the bike ! Sammy Miller did a conversion in recent years, so it might be worth having a word with him before you make a decision… See you next Sunday.
Brian

[gammakeith]

Thanks Brain. That Company in Newark is the one that re-did my RG500 fork legs 10 years ago (and which are still perfect) so will certainly get my repeat custom if needed. As you say, its near impossible to find the right unit and also has a very grumpy owner but they do a great job. The leak isn’t at the valve but seems to be at the top of the left hand fork tube as you can clearly hear it hissing out when pumping the forks. Thanks for the tip about the bushes. I was planning on going to Newark soon as I need some bits and pieces for the latest project donated by my father (British Anzani lawnrider mower).

I like the idea of having a bike thats over 60 years oid that has air suspension. Thus, I will do my best to get it working as Dowty intended. A spring conversation will only be a last resort.

Look forward to meeting up on Sunday!

Keith

[Deleted User]

Every Brum Scott that I have seen that still the original brake cable “splitter” also had a really serious 6V horn as well so maybe this is the origin of the mechanics comment…..”I couldn’t fix your brakes so I’ve made your horn louder” 🙄

[Deleted User]

In 1960 a friend and I bought a pair of new scotts from Harry Langman and before leaving the shop I asked him about the front brake, i.e. was it as good as it looked. He had taken my 1947 F.S. in part exchange and I was hoping that the new bike had something a bit better than the old one. He told me that the one thing I wouldn’t have any trouble with was the brakes. If I remember correctly, the front brake was a twin 8″ and Harry said it had more lining area than a Manx Norton. He said it portraid great optimism so far as the engine was concerned. My current Scott, a 1947 F.S. has a twin pull handebar lever and we had trouble getting it through the test a couple of weeks ago. I’ve had it apart and there’s nothing obvious, but the cables seem a bit thin so I’m looking at trying to fit thicker/better cables to cut out some of the sponginess.
Tony Kitching

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