Better hub brakes (floating trailing shoe?)

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Brucey
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Re: Better hub brakes (floating trailing shoe?)

Postby Brucey » 17 Oct 2013, 4:11pm

[quote="Swizz69"]I have drums on my Dutchbike that are suffering from poor performance due to leading shoe wear. They are rod operated and despite being Sturmey hub geared, the brakes & hub shells appear to be of Gazelles own manufacture.
Image
[quote]

I have always supposed that these brakes are SA brakes, just branded Gazelle. 'KB' used to be a SA hub designation BTW. If the shoes are SA shoes, they should be marked up appropriately internally.

BTW with a linked brake system, something which limits the rear force is a good idea; perhaps you can install a stack of belleville washers in the linkage somewhere, and experiment with the rear brake force?

cheers
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Swizz69
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Re: Better hub brakes (floating trailing shoe?)

Postby Swizz69 » 20 Oct 2013, 3:32am

Brucey wrote: I have always supposed that these brakes are SA brakes, just branded Gazelle. 'KB' used to be a SA hub designation BTW. If the shoes are SA shoes, they should be marked up appropriately internally.


They could well be - makes more sense I suppose than reinventing the wheel.

BTW with a linked brake system, something which limits the rear force is a good idea; perhaps you can install a stack of belleville washers in the linkage somewhere, and experiment with the rear brake force?


I'd be happier with a stronger back brake! Much of the weight is over the back wheel when loaded & a fair bit when not. The mishaps have always been due to the lightly loaded front wheel locking up on wet grass. Try and imagine riding a ton of bicycle down a wet grass slope knowing that despite needing to stop, applying the brakes will lead to a worse outcome than just clinging on and hoping for the best :shock: :shock: :shock:

Brucey
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Re: Better hub brakes (floating trailing shoe?)

Postby Brucey » 20 Oct 2013, 5:02am

if you are in the habit of riding on wet grass, I reckon you would most likely be much better off without linked brakes.

In the circumstances you describe, it takes an unusual degree of commitment to lean forwards enough to be able to use the front brake enough to be worthwhile, even if it is possible.

BTW I had a look inside such a brake in the last few days, and they were indeed SA brake shoes within.

cheers
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xcalibur
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Re: Better hub brakes (floating trailing shoe?)

Postby xcalibur » 20 Oct 2013, 5:28pm

I am in Norway and DBS used to make their own hubs and hub brakes named "Gigiant". They where pretty much the same as SA and Sachs, but they often worked a bit better. This was the case with old bikes from the 50s and closer to 1990s. I don't think they are made anymore though, and the design changed a bit over the years. They varied from 90 mm to 50mm I think. I have tried to figure out why the old DBS Gigant brand worked better, the brake compound from different makers like SA and Sach were much the same over the years (the later red brick coloured ones are good). The brake shoes in these are two separat pieces, joined together with two springs and move somewhat freely from each other (SA often just one spring on the non hinged side). After reading this thread I have been wondering if this might be the reason why these old hub brakes have been easier to adjust and to make them work well. They might press more evenly on the drum sides? I have never had drum brakes work as precies and firm as disks when they work well, but I have never had more costly, fuzzy and often in need of repair than disk brakes either. For a few years I had completely converted to disk brakes, and put any other type on the shelf, but the last year or so I have changed my mind. My old 1980s 5 speed were given a fix up, and it still works fine and much more reliable than disk brakes. I'm thinking of having 28" wheels built with hub brakes, maybe alfine hub gear with coaster brake. Are there any good hubbrakes available? My aim is to have as durable and long lasting wear parts as possible.

Brucey
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Re: Better hub brakes (floating trailing shoe?)

Postby Brucey » 20 Oct 2013, 6:38pm

of those commonly available, I think the nicest looking hub brakes are the SA XL ones with the 90mm drums. I guess the other obvious route is to use Shimano roller brakes. I don't think that either type of brake has the same combination of power and modulation as a really good disc brake, but they do need much less maintenance.

A hub with a good combination of reliability, gear ratios, and sensible braking is the shimano nexus 7 with coaster brake. You can also get the Nexus 8 with a coaster brake on it too.

It is also possible to get the SA brakes in hubs for an 8/9/10s cassette or a screw-on freewheel, too.

cheers
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MikeF
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Re: Better hub brakes (floating trailing shoe?)

Postby MikeF » 23 Oct 2013, 10:46pm

pete75 wrote:Now then Brucey this is what a really effective front drum looks like :) Made by Fontana I think.


Image
This appears to be a double leading shoe brake (on a large drum as well). A better cycle hub brake, at least on the front, would have 2 leading shoes - not difficult to implement in an initial design, but harder to modify an existing leading/trailing shoe brake.
"It takes a genius to spot the obvious" - my old physics master

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NATURAL ANKLING
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Re: Better hub brakes (floating trailing shoe?)

Postby NATURAL ANKLING » 23 Oct 2013, 11:36pm

Hi,
Yes double leading brakes are superiour, some of the racers did have four shoes two a side by memory.
Road bikes even
http://www.realclassic.co.uk/benellitornado650.html
http://www.engineeringinspiration.co.uk/drumbrakes.html
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Brucey
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Re: Better hub brakes (floating trailing shoe?)

Postby Brucey » 24 Oct 2013, 11:52am

IIRC when TLS brakes have been tried on bicycles, they have usually proven somewhat grabby. IIRC David Wrath Sharman has mentioned this in an earlier posting (in this thread?).

Leading shoes work more powerfully in part because they have a self-servoing action; this can however make the brake modulation (at low forces, like you might need on slippy surfaces) a bit grabby and unpredictable. Maybe twin trailing shoes, but with more MA, might be worth a try?

Also, IME something happens with some drum brakes when you really need more power; you can be tugging away like billy-o on the lever (or pushing on the pedal) and you just don't get any more braking power. I don't know why this might be; shoe flex, brake lining properties, heat build up....maybe it varies.

However, my 70mm SA brakes do this to some extent from cold on first application, so I don't think it is heat build up causing 'fade' in that case; a single hard stop barely makes the brake warm to the touch overall, so it is hard to see how the temperatures could be that extreme, even locally.

The only thing I've experienced that is similar is trying to re-use disc pads which have been contaminated with oil; even after degreasing many times over, a little oil residue in friction material bleeds out as soon as it gets even slightly warm. The result is that the brake goes away quickly even on modest applications, where by contrast on light/brief applications it can feel OK.

I did wonder if my SA brake linings were similarly contaminated, but brand-new linings do the same thing, even after they are bedded in.

cheers
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NATURAL ANKLING
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Re: Better hub brakes (floating trailing shoe?)

Postby NATURAL ANKLING » 24 Oct 2013, 7:22pm

Hi,
I have found my canti setups on my MTB and Tourer with OEM shoes more than man enough for to drag my all up weight of 96 + kgs to a halt on any hill. OK so I have large strong hands too :)

But my first outing on my latest skip project complete with V brakes (first ever experience :shock: ) had me nearly off on the first downhill corner, and I spent the rest of ride ( 2hrs on off road in a storm up to my knees in water ) gently applying brakes, even though I had silly dog leg levers and was only useing three fingers.
Mind you brake shoes were doing mm's an hour and I will need a shed for the skip wheels an another for spares :(
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Swizz69
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Re: Better hub brakes (floating trailing shoe?)

Postby Swizz69 » 29 Oct 2013, 9:59am

Cantis vs V Brakes - couldn't agree more. Love the former...not at all struck on the latter!

Anyway, re modifying drum brakes...I've had a play with mine over the last few lunch breaks. You were spot on Brucey - they are Sturmey Archer. However unlike the alloy shelled ones Rob modified, these are all steel and a bit trickier to do the same with.

I almost attempted a full rollercam arrangement until stripping down & realising how wafer thin the backplate is - the load being carried by the thicker plate that's part of the reaction arm.

Image

In the end, having to improve them somehow I went for something along the lines of the Leleu drums but not quite so rough (unless you count getting carried away with a drillsaw bit as opposed to carefully filing)

I welded a washer around the cam bush flange to increase the surface area of its face for friction, and slotted the hole where it passes through the reaction arm, to allow the bush to be supported by the reaction arm but also move independently from it.

On the rear of the reaction arm there were two lugs that pinned it to the thin backplate - these were ground off to allow the backplate to rotate around the axle with the cam bush.

The hole in the backplate where the fulcrum passes through was slotted. I should have also slotted the holes in the black plate (see pic) which keeps oil leaks off the brakes but ran out of time. These holes were slightly oversize though in any case so for the time being aren't a problem.

The difference is pretty positive if a little sharp but will give it a few weeks for a better idea. I chamfered the leading shoe to try & prevent grabbing. Only the rear brake was modified.

Image

Using a Tapley Meter strapped to the pannier rack I could even measure the difference, albeit on a concrete floor.

Before:
Both brakes pulled an average of 29.6% g
Disconnecting each gave...
Front only 28.6% g
Rear only 23.1% g

After modification & the front still disconnected, the rear pulled an average of 32.5% g, and the wheel locked so on dry tar mack would have been better!

Again, time was short so didn't get chance to reconnect the front & get a full reading, but I'm happy with an almost 30% improvement on the rear.

Improved modulation would be nice but with the brakes being linked, how it will perform in various conditions only time will tell.

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breakwellmz
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Re: Better hub brakes (floating trailing shoe?)

Postby breakwellmz » 19 Dec 2013, 5:03pm

xcalibur wrote:I am in Norway and DBS used to make their own hubs and hub brakes named "Gigiant". They where pretty much the same as SA and Sachs, but they often worked a bit better. This was the case with old bikes from the 50s and closer to 1990s. I don't think they are made anymore though, and the design changed a bit over the years. They varied from 90 mm to 50mm I think. I have tried to figure out why the old DBS Gigant brand worked better, the brake compound from different makers like SA and Sach were much the same over the years (the later red brick coloured ones are good). The brake shoes in these are two separat pieces, joined together with two springs and move somewhat freely from each other (SA often just one spring on the non hinged side). After reading this thread I have been wondering if this might be the reason why these old hub brakes have been easier to adjust and to make them work well. They might press more evenly on the drum sides? I have never had drum brakes work as precies and firm as disks when they work well, but I have never had more costly, fuzzy and often in need of repair than disk brakes either. For a few years I had completely converted to disk brakes, and put any other type on the shelf, but the last year or so I have changed my mind. My old 1980s 5 speed were given a fix up, and it still works fine and much more reliable than disk brakes. I'm thinking of having 28" wheels built with hub brakes, maybe alfine hub gear with coaster brake. Are there any good hubbrakes available? My aim is to have as durable and long lasting wear parts as possible.


I`ve dug one of these out of the garage(90mm GIGANT) which i intend to put on the winter hack,the sound of wet grit on alloy rims via a`V`brake upsets my mechanical sympathies!
There is no obvious(To me)anti-rotation for the brake back-plate,any thoughts?
Would my current`V`brake lever be suitable,or is it a case of`suck it and see`?

Cheers
Image Attachments
Hub brake 002 (Small).jpg
Hub brake 001 (Small).jpg

Brucey
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Re: Better hub brakes (floating trailing shoe?)

Postby Brucey » 19 Dec 2013, 5:15pm

I think you are meant to put a clip around the fork leg to pick up on the reaction arm. I think it would be incredibly dangerous to run this brake without one!

cheers
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robc02
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Re: Better hub brakes (floating trailing shoe?)

Postby robc02 » 19 Dec 2013, 7:24pm

Would my current`V`brake lever be suitable,or is it a case of`suck it and see`?


I run my SA drums with the type of Tektro drop bar levers that are meant for V-brakes and they work well. My first attempt - using ordinary drop bar levers - resulted in a spongy feel and using up all, or very nearly all, of the lever travel. I would give your V-brake levers a try.

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breakwellmz
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Re: Better hub brakes (floating trailing shoe?)

Postby breakwellmz » 19 Dec 2013, 7:33pm

Cheers Brucey.

I suppose i was expecting to find a fork attachment fitting to be incorporated,i`m sure a way of making something suitable will become obvious when i drop it in the forks.

I`m hoping it will be a better brake than the Nexus hub brake(the one you grease throughout :roll: )i used for short while.

I doubt whether i would be able to find spares for this hub if i should need them.