Help me decode Weinmann Brakes. Now with Pics!

[foaf]

Looks to me like you're trying to fit a calliper brake to the rear triangle of a Moulton Mk3. You've set yourself up for few complications...
The Mk3 was not originally fitted with a calliper brake. It had a Sturmey Archer S3B rear hub as OEM. This was a Sturmey Archer AW 3-speed hub combined with a cable-operated drum brake. The drum brake was very poor when new and became considerably worse with use, due to the inadequate seal between the geared part and the drum brake part allowing oil from the epicyclic gears to leak onto the drum brake shoes. Not one of Sturmey's finest offerings.
The rear triangle of a Mk3 has shaped plates welded to both the chainstays and seatstays which look like they are for fitting calliper brakes. They even have the correct size holes drilled in them. However, these plates are made of thin sheet metal and were only originally meant for attaching mudguards. You can fit brake callipers to them but the plate will flex alarmingly under heavy braking with a well-designed calliper. The callipers also need to be very long reach to make the distance to the 16 x 1 3/8 (37 - 349) rims. Neither of these facts is conducive to having a reassuringly good rear brake.
Having spelled out the doom and gloom, are there any solutions? Well, the original chromed-steel Phillips brake callipers as fitted to the rest of the F-frame Moulton range work very well, even if they are a bit heavy and perhaps rather unglamorous. They also have the necessary reach and are stiff enough, being made from steel. Add in decent modern brake pads and they're pretty good. I haven't yet found a period alloy calliper that will reach to 16" rims and is substantial enough to give good braking. Modern Alhonga/Tektro deep-drop dual-pivot alloy callipers work very well and might just reach far enough but I can't confirm - I use these on my Mk3 but I have 17" wheels (32 - 369) fitted which are a little larger.
One further point to remember is that the brake cable to the rear calliper is very long and also follows a fairly tortuous route. This really doesn't help the braking action either. So, all things considered, don't expect to obtain brilliant braking from a rear calliper bake on a Mk3.

 

[Iwasgoodonce]

Thanks again foaf. You do seem to know these curious machines very well. The picture below is the one shot I have of it before it came apart. There is another strange point in as much as the remains of the kick stand is fitted to the rear triangle. Others far mor knowledgable than me have said it should be on the bottom bracket?

Could it be another case of a Friday afternoon job in the Midlands? Maybe the strong unions and bad attitude that killed the midlands car industry had reached Nottingham? For the record, the rear hub is a three speed Sturmey Archer inside a five speed shell.

Thankfully, the Moulton's new life will consist on going along Totnes cycle path (if it hasn't washed away!) being ridden by my Mum to collect shopping etc. It won't have to be capable of stopping quickly from high speeds!

Perhaps if I slide the wheel forwards in the dropouts and perform a little file action, the "original" steel brake might reach? It didn't look likely but it must have performed some function?

 

[Iwasgoodonce]

Foaf, Right I have mad a decision! I'm going to either extend the existing hole or drill a new one and just use the existing chrome steel brake.

Taking what you said about the metal plate on the rear triangle on board, I'll add another piece of metal to the top of it. Initially it'll just be loose and held in by the brake bolt and maybe a couple of self tappers. If I cut it so that it exactly the same length as the width of the rear triangle, it will add ample strength. If it works well, I will think about welding it on to the existing plate with some low power MIG.

What do you think?

 

[foaf]

Hi Iwasgoodonce,

Nice find! It's almost exactly the same as my first Moulton which I fished out of a pile of garden rubbish that had been dumped in the lane behind my Mum's house. My Mk3 was red too, but it was totally original and complete (it even had the optional rear bag fitted), just unloved, unused and discarded. It took a long time to completely strip down, clean, polish, lubricate and reassemble, but it was worth it in the end.
I have never seen a Mk3 with the prop stand fitted to the rear triangle. My guess is that someone wasn't paying attention on a Friday afternoon, or maybe thought it might be a good idea. Whatever, it makes it a bit different and adds interest.
Please don't do any drilling or filing just yet. I'll dig out my Mk3 tomorrow afternoon and swap in a spare 16" (32 -349) rear wheel to see whether the brakes will reach. I seem to remember that the hole on the plate on the seatstays is a closer reach than the one on the plate on the chainstays. I'll measure them both for you. You might want to check them on your bike too. Quality control wasn't great at Raleigh and it wouldn't surprise me if your are different to mine. I can also try out a few different alloy brake callipers too. I unearthed a few from the man cave this afternnon so I'll see how they measure up.
Your idea of reinforcing the plate is a good one and has been successfully done before, pretty much in the way that you suggest. Welding the reinforcement to the stays and the plate will provide improved strength too. However, bear in mind that:
1. the long rear cable reduces brake efficiency,
2. the awkward cable routing adds friction and reduces braking 'feel',
and 3. the rear brake doesn't actually do much in reality even when it does work properly.
You might put in a lot of effort for very little additional reward.

Stay tuned for some feedback from man cave fiddlings tomorrow...

 

[Iwasgoodonce]

Cheers foaf! I didn't drill anything today, I went cycling instead. I'm thinking the lower plate has a better cable run than the top. The metal looks more substantial as well!

It will be interesting to compare the two bikes. How do they ride?

 

[foaf]

Sorry for the delay. I haven't forgotten, but just have had no time to get to the relevant bike and bits. Hope to have a few spare seconds tomorrow afternoon...

 

[Iwasgoodonce]

Sorry for the delay. I haven't forgotten, but just have had no time to get to the relevant bike and bits. Hope to have a few spare seconds tomorrow afternoon...

Cool, no rush. I won't be drilling/altering anything until the weekend.

 

[foaf]

Have enjoyed frittering away a pleasant couple of hours playing bikes in the sun this afternoon.
Took some comparative measurements from the 'brake' plates to the axle, and of which alloy callipers will reach 16" (32 -349) rims.
First off, as I suspected, the hole for the brake calliper pivot on the seatstay is considerably closer to the rim than the one on the chainstay (by about 10mm). Remember that this is my frame, and your frame might be different so it's worth measuring yours, just to be safe.
On my frame I was not able to get any alloy callipers to reach a 16" rim from the plate on the chainstays. I tried Alhonga deep-drop dual pivots and Weinmann 810 side-pulls which are the two furthest reach callipers I have in stock. Original Moulton fitment chromed-steel Phillips side-pulls will just reach.
On the seatstays, Alhonga deep-drop dual pivots don't quite reach 16" rims, although they're very close. Perhaps with a little judicious filing of the brake pad slots on the callipers they would work, but it really is pushing the limit. Weinmann 810 side-pulls reach OK and work quite well bearing in mind they're rather flimsy and made of cheese. Weinmann 730 side-pulls fall short and won't work.
On my Mk3 I have Alhonga deep-drop dual-pivot callipers fitted to the seatstay plate to reach 17" (28 - 369) rims. I have not really noticed any problems with the plate flexing, the braking power is adequate but the modulation is woolly.
Hope this is helpful. I've kept the bike and spare wheel handy if you need any more information.

 

[Iwasgoodonce]

Cheers foaf! On mine, the seat stay plate is closer too. However, for some reason the plate just feels more tinny.

I have cut a cardboard template for the chainstay plate and will recreate it in metal. I will use the old brake hole to help bolt the metal plate into place.

Do you have a photo of your MK3?

 

[foaf]

This is my Mk3, pictured at the Moulton Bicycle Club meet at Bradford-on-Avon in September 2010.

http://tinyurl.com/o7fqy9a

It is still a work in (slow) progress. Since this picture was taken I have added a small rear rack and day bag. I intend to get the main frame powder-coated white and have the front forks and rear triangle powder-coated chrome. All that remains will be to give the components a clean and polish and it should look quite nice.

Also, in answer to your earlier question about what are MK3s like to ride; once all the cheap and heavy original Raleigh components have been replaced with better quality alloy parts and the gearing improved with superior hub units or derailleur gears then they ride very nicely. Some taller riders find them a bit 'cramped' but I have not suffered this even though I'm 6'2". They'll never be a racing thoroughbred but for long comfortable days out with a modest load there probably isn't much to better a modified Mk3, apart from an AM.