Drum Brakes

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hartleymartin
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Drum Brakes

Postby hartleymartin » Sun Jul 12, 2009 12:18 am

I've been looking around on Sturmey-Archer's website and I see that there are two main sizes of drum-brake viz: 70mm and 90mm. Is there any difference in their performance? Does a different size last longer? I know that drum brakes are inferior in performance to rim brakes, but I figure that since I typically use chromed steel rims which are almost useless in the wet, that drum brakes might be good on one of my roadsters.
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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Tue Jul 14, 2009 3:49 pm

It seems that with the lack of responses so far that not many people here have expertise or experience with drum brakes.
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zozza
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Re: Drum Brakes

Postby zozza » Tue Jul 14, 2009 4:27 pm

I think I saw some at the Powerhouse once :roll:

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leximack
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Re: Drum Brakes

Postby leximack » Tue Jul 14, 2009 4:34 pm

zozza wrote:I think I saw some at the Powerhouse once :roll:

:lol: :lol:

LittleWheelsandBig
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Re: Drum Brakes

Postby LittleWheelsandBig » Tue Jul 14, 2009 5:46 pm

The larger the diameter, the more powerful the drum brake, also heavier and with more total heat capacity (better for long descents). Obsolete tandem-specific drum brakes (e.g. British Hub Co) work very well. The Arai drum is for drag brake use only. It doesn't stop very well but can absorb a huge amount of heat. Drum brakes are slowly making a comeback. For a long time they were only championed by Mike Burrows (excessively so).

F&S used to make rounder drums than English SA, which often used to judder a little. I haven't used the larger SA drums but the Sunrace-made 70 mm drums are pretty good.
Last edited by LittleWheelsandBig on Wed Jul 15, 2009 5:11 am, edited 1 time in total.

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Re: Drum Brakes

Postby Low Racer » Tue Jul 14, 2009 6:40 pm

hartleymartin wrote:I know that drum brakes are inferior in performance to rim brakes, but I figure that since I typically use chromed steel rims which are almost useless in the wet, that drum brakes might be good on one of my roadsters.
I have SA drum brakes on my Greenspeed GT3II trike and it is far superior to rim brakes on my recumbent bike. Drum brakes needed to be bedded in and once you have achieved that, they are really good brakes for dry and wet conditions. You do pay the weight penalty though.
Last edited by Low Racer on Tue Jul 14, 2009 7:07 pm, edited 1 time in total.

LittleWheelsandBig
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Re: Drum Brakes

Postby LittleWheelsandBig » Tue Jul 14, 2009 7:05 pm

Low Racer wrote: I have SA drum brakes on my Greenspeed GT3II trike and it is far superior to rim brakes on my recumbent bike.
Little wheels help drum brakes perform much better.

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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Tue Jul 14, 2009 10:03 pm

In my mind I had reasoned that larger drum brakes would be more powerful, but I thought I had better ask around to see if anyone could confirm it.

I was looking at purchasing a sturmey-archer front dynohub, but they don't make a plain dynohub any more. They all come with drum brakes on them. I've thought of the possibility of using cable-operated drum brakes both front and rear on a newer utility bicycle to ensure better all-weather performance.
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Re: Drum Brakes

Postby Chaderotti » Tue Jul 14, 2009 11:30 pm

hartleymartin wrote:In my mind I had reasoned that larger drum brakes would be more powerful, but I thought I had better ask around to see if anyone could confirm it.
I guess it's the same as different rotor diameter in disc brakes. A smaller diameter will virtually have the same stopping power as a larger roter, but heat up and wear out faster.
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Zynster
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Re: Drum Brakes

Postby Zynster » Wed Jul 15, 2009 9:53 am

I still have the scars from when I was 14 and my drum brake failed at the bottom of a large hill, briefly turning my bike into a fixie and thus launching me several feet into the air. :shock:
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Re: Drum Brakes

Postby rkelsen » Wed Jul 15, 2009 10:53 am

Chaderotti wrote:I guess it's the same as different rotor diameter in disc brakes. A smaller diameter will virtually have the same stopping power as a larger roter, but heat up and wear out faster.
And begin to fade quicker.

Bigger surface/contact area is always better with any kind of brake, if only for heat dissipation & therefore fade resistance. Excess heat in brakes is always bad.

You know, you could avoid all this simply by using aluminium rims, HM... :lol: What with all the talk of a drop handlebarred, derailleur geared bike, your integrity has come into question anyways... :P

LittleWheelsandBig
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Re: Drum Brakes

Postby LittleWheelsandBig » Wed Jul 15, 2009 12:31 pm

Chaderotti wrote: I guess it's the same as different rotor diameter in disc brakes. A smaller diameter will virtually have the same stopping power as a larger roter, but heat up and wear out faster.
Most of the disc and drum brakes I've used have increased power as the size increases (for the same design).

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WyvernRH
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Re: Drum Brakes

Postby WyvernRH » Wed Jul 15, 2009 4:52 pm

LittleWheelsandBig wrote:
Chaderotti wrote: I guess it's the same as different rotor diameter in disc brakes. A smaller diameter will virtually have the same stopping power as a larger roter, but heat up and wear out faster.
Most of the disc and drum brakes I've used have increased power as the size increases (for the same design).
Also, depends if they are leading or trailing shoe activated or twin leading shoe activated (assuming we don't go into the exotica of more than two brake shoes)
The twin leading shoe design is more complex/expensive but works considerably better than the simple leading shoe design.
Trailing shoe activation sucks. :wink:
Most bicycle brakes are leading shoe activated with only one pivoting cam pushing one end of the two shoes apart and into the brake drum. The twin leading shoe activated brake was standard on British motorbikes before disc brakes became popular and has two pivoting cams linked by a rod so the two shoes are pushed evenly apart into the brake drum. As a motorbike brake it was very effective when properly adjusted.
As a young engineer new to bicycles, I modified and old Sturmey front to be twin leading shoe using my BSA Rocket's front brake as a model and found several problems.
(1) Way too powerful for a solo bicycle on the front, very easy to put yourself over the bars. Maybe better on a tandem, or the rear wheel
(2) Not a lot of 'feel' (see point one :) ), it came on really quickly (maybe my design needed tuning a bit, less leverage perhaps)
(3) The amount of force you could generate pushing the pad onto the drum caused the brake hub to heat up very quickly (and excessively) if used on long hills, or with hard repeated braking, causing the hub to get REALLY hot so the grease melted out the bearings and the rivets holding the hub together eventually came loose.
(4)The reverse load on the spokes seemed to cause a lot of spoke breakages but again it could have been my dodgy wheel building at the time.

Maybe someone would like to try a modern conversion? I have a suspicion that most modern aluminium hub brakes would just not be up to the stress.

cheers
Richard

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Re: Drum Brakes

Postby trailgumby » Wed Jul 15, 2009 7:12 pm

Chaderotti wrote:I guess it's the same as different rotor diameter in disc brakes. A smaller diameter will virtually have the same stopping power as a larger roter, but heat up and wear out faster.
No. Definitely not. Larger diameter rotors are definitely more powerful.

I had a 7" disc on the front wheel of my original commuter. It was a lot more sudden and had to be used with a lot of care in the wet, especially with skinny commuter tyres. I have since gone back to 6" discs all round. 7" was a lot more brake than I needed.

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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Wed Jul 15, 2009 8:46 pm

Just throwing around some ideas with bicycle brakes:

I've just had a crazy thought with a bicycle which has 4 brakes. Now hear me out:

Front Brake 1: Rim operated by right brake lever
Front Brake 2: Hub operated by lever mounted near stem
Rear Brake 1: Rim operated by left brake lever
Rear Brake 2: Coaster

This gives me rim brakes for normal riding conditions, but also gives me a back-up braking system for wet conditions. Having a coaster brake would limit me to a 3-speed hub, as no 5 or 8 speed hubs are currently made with a coaster option, although Shimano did make a 7-speed hub with coaster brake, it is now out of production.

An alternative 3-brake design (again for drop handle-bars) would have:

Front Brake 1: Rim operated by right brake lever
Front Brake 2: Hub operated by lever mounted near stem.
Rear Brake: Hub operated by left brake lever

This would allow me to use a 5 or 8-speed hub which has a drum brake.

I've read some of Sheldon Brown's stuff on braking and he reckons that only a front brake should be used in dry conditions, but preference should be given to the use of rear brakes in wet weather conditions. Having a drum brake on the rear (which is not affected by the wet as much as rim brakes) would work well with this sort of braking technique.

I've got some new wheels on the way. The front wheel has a Shimano dynamo hub, and the rear wheel has a Sturmey-Archer SRC3 3-speed coaster braked hub. The bicycle they will be going on is going to have rim brakes front and rear anyway, as I feel as my left hand feels lonely for a brake lever.
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il padrone
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Re: Drum Brakes

Postby il padrone » Wed Jul 15, 2009 9:10 pm

hartleymartin wrote:Just throwing around some ideas with bicycle brakes:

I've just had a crazy thought with a bicycle which has 4 brakes. Now hear me out:

Front Brake 1: Rim operated by right brake lever
Front Brake 2: Hub operated by lever mounted near stem
Rear Brake 1: Rim operated by left brake lever
Rear Brake 2: Coaster

This gives me rim brakes for normal riding conditions, but also gives me a back-up braking system for wet conditions. Having a coaster brake would limit me to a 3-speed hub, as no 5 or 8 speed hubs are currently made with a coaster option, although Shimano did make a 7-speed hub with coaster brake, it is now out of production.
No, no!

Much beeter option is available:

Front Brake 1: Rim operated by right brake lever
Front Brake 2: Hub operated by lever mounted near stem
Rear Brake 1: Rim operated by left brake lever
Rear Brake 2: Disc operated by friction lever at stem, running on Rohloff 14 sp hub

:wink:
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bigfriendlyvegan
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Re: Drum Brakes

Postby bigfriendlyvegan » Wed Jul 15, 2009 10:00 pm

Or you could mount brakes on the rear of the fork and at the bottom of the seat tube as well.

And disk brakes on each wheel.

And a stick to put between the spokes if all else fails.

:D

If you're really keen you could adapt the technology from hybrid cars and use the friction from the braking to recharge a battery for your lights.

David

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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Wed Jul 15, 2009 10:11 pm

Regenerative braking from an electric hub motor has been considered, but at the moment I do not have the money for a hub motor kit, battery and the electrical gear required to do it. And of course, I've enrolled in an Arts degree, not Science. It would make a good thesis project for science.
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WyvernRH
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Re: Drum Brakes

Postby WyvernRH » Thu Jul 16, 2009 6:25 am

hartleymartin wrote:Regenerative braking from an electric hub motor has been considered, but at the moment I do not have the money for a hub motor kit, battery and the electrical gear required to do it. And of course, I've enrolled in an Arts degree, not Science. It would make a good thesis project for science.
Been done, many times with varying degrees of success. You would have to come up with a really radical improvement to get your Msc or PhD :) Unless you really want to home build you would probably just be re-inventing the wheel (no pun intended) but you could assemble a system from pre-made parts fairly easily.
Try http://www.atob.org.uk/questionselectric.htm for some basic info and pointers to more complex stuff.
Cheers
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Re: Drum Brakes

Postby kukamunga » Thu Jul 16, 2009 8:02 am

Running into solid objects is one of the most effective forms of breaking..... :roll:

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Re: Drum Brakes

Postby Chaderotti » Thu Jul 16, 2009 11:18 am

1. front wheel: rim brake operated by right brake lever
2. front wheel: disc brake operated by lever mounted on hoods
3. front wheel: hub operated by lever mounted on right side of stem
4. rear wheel: rim brake operated by left brake lever
5. rear wheel: disc brake operated by lever mounted on hoods
6. rear wheel: coaster brake
7. foot on rear wheel
8. stick
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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Thu Jul 16, 2009 5:58 pm

When I took the mudguards off one of my roadsters (they were not off for long) I did try braking by sticking my foot in between the front wheel and the down-tube. Quite effective actually!
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Re: Drum Brakes

Postby trailgumby » Sat Jul 18, 2009 11:52 am

So how many toes do you have now? :lol:

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hartleymartin
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Re: Drum Brakes

Postby hartleymartin » Sat Jul 18, 2009 5:32 pm

Obviously I was wearing shoes at the time.
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