Sturmey Archer X-FDD hub

[Joel Mayes]

Does anyone here have experience with the S-A X-FDD dynohub with drum
brake? I'm considering of a new wheel for my commuter/tourer. I'm
particularly wondering about the effectiveness of the brake for fully
loaded touring.

My main experience with drum brakes is with my old Australia post
utility bike is geared down to about 30 gear inches and the Sachs drum
brake pulls it up well, but it rarely goes above 15km/h...

One reason I'm considering this but is that Shimano, in all their wisdom,
has decreed that only the 32 hole nexus dynamo hub shall be sold down
under. (and I can't afford a SON)

Cheers

Joel
--
Human Powered Cycles | High quality servicing and repairs
[email protected] | Affordable second hand bikes
(03) 9029 6504 | Bicycle reuse centre
www.humanpowered.com.au | Mechanical and on-road training and instruction

 

[Chalo]

On Jul 29, 2:48 am, Joel Mayes <[email protected]> wrote:
> Does anyone here have experience with the S-A X-FDD dynohub with drum
> brake? I'm considering of a new wheel for my commuter/tourer. I'm
> particularly wondering about the effectiveness of the brake for fully
> loaded touring.

To put the rest of what I have to say into context, I probably weigh
more than you, your bike, and all the touring gear you can possibly
stand to carry, combined. I have shed over 50 lbs. during the last
year, which leaves my body weight at just under 350 lbs. Nonetheless
I am an active rider, and at a sturdy 6'8" tall, I can carry all my
weight without debilitating effects.

I have a touring bike equipped with Sachs drum brakes, which are the
next closest thing to Sturmey Archer drums. At first, the stopping
power I got from these brakes was highly disappointing. I switched to
longer brake levers that pulled more cable, and the brakes'
performance improved noticeably. They were still pretty weak,
though.

As I have used them, the stopping power I get from my drum brakes has
kept getting better and better. The drum brakes have now surpassed
the caliper brakes on some of my other bikes. I like them a lot,
especially since they don't require anything of me as they continue
improving.

One thing to consider with drums is that they can be finicky about how
well they play with different brake levers; if you are committed to a
particular pair of levers, you may not get all the braking power of
which the brakes are capable.

I wonder whether the waste heat developed by the brake might have a
negative effect on the performance or the longevity of the hub
dynamo. It's probably not a big issue if your local area does not
have long continuous grades with hundreds of feet of elevation
change.

Chalo

 

[=?ISO-8859-1?Q?G=FCnther?= Schwarz]

Chalo wrote:

> On Jul 29, 2:48 am, Joel Mayes <[email protected]> wrote:
>> Does anyone here have experience with the S-A X-FDD dynohub with drum
>> brake?

I'm using this hub on my commuter bike. I like the looks and it was
pretty cheap. Be aware that the dynamo does not comply to German
standards. It less powerful at low speeds than other makes, but then at
higher speed it exceeds the standards and might fry a halogen lamp if
one is not using a well working overvoltage protection in the light:
<http://www.enhydralutris.de/Fahrrad/Beleuchtung/node50.html>
(red curve in 'Bild 2.21')
For comparision the Shimano DH3-N70:
<http://www.enhydralutris.de/Fahrrad/Beleuchtung/node77.html>
So with a load of 12 Ohm the Sturmey Archer reaches 7.5V at 30km/h while
the Shimano stays at about 7V. At 10km/h the figures are 5V and 5.2V.

>> I'm considering of a new wheel for my commuter/tourer. I'm
>> particularly wondering about the effectiveness of the brake for fully
>> loaded touring.

IME the brake is not so impressive when used on a standard bike with
normal wheels. The X-FD version without dynamo works very nicely on my
tadpole trike which I use occasionally for touring in the Alpes. But
there are two of them on the two front wheels. Also the wheels are
406/20" which means that the leverage is much better for a hub brake
than with big wheels. And I'm a light rider also.

> I wonder whether the waste heat developed by the brake might have a
> negative effect on the performance or the longevity of the hub
> dynamo.

That is not likely as the generator does not contain many parts made of
plastic. The thing to worry about are the plastic parts in the brake
lever fitting. That said the X-FDD will probably heat up more than the
X-FD. It is basically a non-issue for riding in flat areas.

> It's probably not a big issue if your local area does not
> have long continuous grades with hundreds of feet of elevation
> change.

That's the main point to consider. If it's available in Australia a SRAM
iBrake together with their hub dynamo or the nice Schmidt SON XS100
might be worth giving a thought. The brake has a larger diameter drum
as compared to the X-FD or the old Sachs ones, and it has a cooling
disk also. I do not have experiences with this brake, but reliable
sources say that it works well, at least on a touring or commuter bike
without excessive loads.

PS: It is a good idea to use fork made specifically for hub brakes. On
standard forks for side pull brakes or with Cantilever mounts the
blades are often not strong enough for the forces that come with hub
brakes:
<http://www.nabendynamo.de/bilder/vollbrems2.jpg>
Note that this is not a fork with straight blades. At least it used to
have curved ones not only on the right side

Günther

 

[[email protected]]

Hi Günther,

I have a question about leverage on a 406 wheel. I have been using an
Avid 160mm mechanical disk brake on my 700c touring bike and found
panic stops on mountain grades at speed inadequate (not that I have
ever had enough brakes). I'm building up a 406 touring bike and
purchased a 185mm disk based on that experience. However, I've been
wondering if that is not excessive and if the dynamics do change on
smaller wheels. Certainly the leverage is higher but I have no idea
what that really means in stopping power. The usual catch phrase with
braking is swept area. Even there, it would seem that is higher on a
small wheel as the disk is turning at a higher rpm for a given forward
speed.

Can you shed any light on this for me?

Thanks!

 

[A Muzi]

>> Joel Mayes <[email protected]> wrote:
>>> Does anyone here have experience with the S-A X-FDD dynohub with drum
>>> brake?
-snip-

> Chalo wrote:
>> I wonder whether the waste heat developed by the brake might have a
>> negative effect on the performance or the longevity of the hub
>> dynamo.

Günther Schwarz wrote:
> That is not likely as the generator does not contain many parts made of
> plastic. The thing to worry about are the plastic parts in the brake
> lever fitting. That said the X-FDD will probably heat up more than the
> X-FD. It is basically a non-issue for riding in flat areas.
-snip-

I thought Chalo was referring to brake heat possibly demagnetizing the
dynamo.
??
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[=?ISO-8859-1?Q?G=FCnther?= Schwarz]

A Muzi wrote:

>>> Joel Mayes <[email protected]> wrote:
>>>> Does anyone here have experience with the S-A X-FDD dynohub with
>>>> drum brake?
> -snip-
>
>> Chalo wrote:
>>> I wonder whether the waste heat developed by the brake might have a
>>> negative effect on the performance or the longevity of the hub
>>> dynamo.
>
> Günther Schwarz wrote:
>> That is not likely as the generator does not contain many parts made
>> of plastic. The thing to worry about are the plastic parts in the
>> brake lever fitting. That said the X-FDD will probably heat up more
>> than the X-FD. It is basically a non-issue for riding in flat areas.
> -snip-
>
> I thought Chalo was referring to brake heat possibly demagnetizing the
> dynamo.
> ??

Some figures quickly taken from Wikipedia:

Co 1394 K (1121°C)
Fe 1041 K (768°C)
Fe3O4 Magnetite TN=850K
Ni 633 K (360°C)
NdFeB TC = 585 K
SmCo 770 °C (Google result)

Now I don't know what they use as magnets in the this hub. But the
figures indicate that one will have to heat up the hub to the point
were all the lubrication drips out the bearings. Be also aware of the
low melting temperature of the hub shell, 933,47 K (660,32 °C) for pure
aluminum.

The brake might also show heavy fading before the generator part reaches
such a high temperature. Actually it is easy to get temper colors on
the steel brake drum without heating up the hub shell excessively,
BTDTNT.

Günther

 

[=?ISO-8859-1?Q?G=FCnther?= Schwarz]

[email protected] wrote:

> I have a question about leverage on a 406 wheel. I have been using an
> Avid 160mm mechanical disk brake on my 700c touring bike and found
> panic stops on mountain grades at speed inadequate (not that I have
> ever had enough brakes). I'm building up a 406 touring bike and
> purchased a 185mm disk based on that experience. However, I've been
> wondering if that is not excessive and if the dynamics do change on
> smaller wheels. Certainly the leverage is higher but I have no idea
> what that really means in stopping power. The usual catch phrase with
> braking is swept area. Even there, it would seem that is higher on a
> small wheel as the disk is turning at a higher rpm for a given forward
> speed.
>
> Can you shed any light on this for me?

I have no experience with disk brake on small wheels. But the relevant
figure here is the disk or drum diameter as compared to the wheel
diameter. So with your touring bike this is 160/622=0.26 as compard to
160/406=0.39 or 185/406=0.46 with small wheels (the actual number is
slightly different as one has to measure the real diameter of the wheel
including the tire, and the effective diameter of the disk determined
by size and position of the brake pads). Like the length of a wrench
used to tighten a bolt the ratio determines how hard one has to squeeze
the brake lever in order to lock the disk. So everything being equal,
with the large wheel and the small disk you will have to press about
twice as hard as with the small wheel and the big disk. Actually all
small wheeled bicycles I'm aware of use 160mm disks. To as far as
mechanical advantage is concerned this seems to be sufficient.

In theory one could build a tiny 100mm disk for small wheels with would
result in the same forces at the lever as a standard disk in a big
wheel. But then another point to consider is heat dissipation: Larger
disks can take longer descents with heavier loads. But unlike with rim
brakes where large wheels are better in this discipline with hub brakes
that does not depend on wheel size, but just on the diameter of the
disk or drum: the larger, the better.

Günther

 

[Chalo]

A Muzi wrote:
>
> > Chalo wrote:
> >>
> >> I wonder whether the waste heat developed by the brake might have a
> >> negative effect on the performance or the longevity of the hub
> >> dynamo.
>
> Günther Schwarz wrote:
> >
> > That is not likely as the generator does not contain many parts made of
> > plastic. The thing to worry about are the plastic parts in the brake
> > lever fitting. That said the X-FDD will probably heat up more than the
> > X-FD. It is basically a non-issue for riding in flat areas.
>
> -snip-
>
> I thought Chalo was referring to brake heat possibly demagnetizing the
> dynamo.
> ??

That's right. I am also concerned about the endurance of the
insulation on the magnet wire, the longevity of any internal diodes,
etc. The temperatures generated by braking don't have to be damaging
by themselves; they could do harm merely by diminishing the gradient
through which waste heat can escape the electronics. In the likely
air flow conditions under which the brake could do heavy work, it's
probably not of much concern.

Chalo

 

[=?ISO-8859-1?Q?G=FCnther?= Schwarz]

Chalo wrote:

> A Muzi wrote:
>>
>> > Chalo wrote:
>> >>
>> >> I wonder whether the waste heat developed by the brake might have
>> >> a negative effect on the performance or the longevity of the hub
>> >> dynamo.
>>
>> Günther Schwarz wrote:
>> >
>> > That is not likely as the generator does not contain many parts
>> > made of plastic. The thing to worry about are the plastic parts in
>> > the brake lever fitting. That said the X-FDD will probably heat up
>> > more than the X-FD. It is basically a non-issue for riding in flat
>> > areas.
>>
>> -snip-
>>
>> I thought Chalo was referring to brake heat possibly demagnetizing
>> the dynamo.
>> ??
>
> That's right. I am also concerned about the endurance of the
> insulation on the magnet wire, the longevity of any internal diodes,
> etc. The temperatures generated by braking don't have to be damaging
> by themselves; they could do harm merely by diminishing the gradient
> through which waste heat can escape the electronics.

Actually there is no electronics in such hubs typically. Just coils and
magnets. But you're right that the wire insulations might suffer from
heat. But then I'm not aware of a report of such a failure. The hubs
will typically die from shot bearings which are not trivial to replace.

Günther

 

[Dan Burkhart]

On Jul 29, 2:48 am, Joel Mayes <[email protected]> wrote:
> Does anyone here have experience with the S-A X-FDD dynohub with drum
> brake? I'm considering of a new wheel for my commuter/tourer. I'm
> particularly wondering about the effectiveness of the brake for fully
> loaded touring.

To put the rest of what I have to say into context, I probably weigh
more than you, your bike, and all the touring gear you can possibly
stand to carry, combined. I have shed over 50 lbs. during the last
year, which leaves my body weight at just under 350 lbs. Nonetheless
I am an active rider, and at a sturdy 6'8" tall, I can carry all my
weight without debilitating effects.

I have a touring bike equipped with Sachs drum brakes, which are the
next closest thing to Sturmey Archer drums. At first, the stopping
power I got from these brakes was highly disappointing. I switched to
longer brake levers that pulled more cable, and the brakes'
performance improved noticeably. They were still pretty weak,
though.

As I have used them, the stopping power I get from my drum brakes has
kept getting better and better. The drum brakes have now surpassed
the caliper brakes on some of my other bikes. I like them a lot,
especially since they don't require anything of me as they continue
improving.

One thing to consider with drums is that they can be finicky about how
well they play with different brake levers; if you are committed to a
particular pair of levers, you may not get all the braking power of
which the brakes are capable.

I wonder whether the waste heat developed by the brake might have a
negative effect on the performance or the longevity of the hub
dynamo. It's probably not a big issue if your local area does not
have long continuous grades with hundreds of feet of elevation
change.

Chalo

I found the Sachs drum brake to be pretty weak too. I never did try a long travel lever on it although I did consider it. These days, I'm mostly riding my Nexus 8, and contrary to Shimano's instructions, I set the lever to long travel mode, and I find the brakes work much better. If I ever get around to reviving my Sachs hub, I think I'll put Avid Speed Dial levers on it. That way, I can set whatever amount of travel I want.

 

[Michael Press]

In article
<[email protected]>
,
[email protected] wrote:

> Hi G?nther,
>
> I have a question about leverage on a 406 wheel. I have been using an
> Avid 160mm mechanical disk brake on my 700c touring bike and found
> panic stops on mountain grades at speed inadequate (not that I have
> ever had enough brakes). I'm building up a 406 touring bike and
> purchased a 185mm disk based on that experience. However, I've been
> wondering if that is not excessive and if the dynamics do change on
> smaller wheels. Certainly the leverage is higher but I have no idea
> what that really means in stopping power. The usual catch phrase with
> braking is swept area. Even there, it would seem that is higher on a
> small wheel as the disk is turning at a higher rpm for a given forward
> speed.
>
> Can you shed any light on this for me?

How many panic stops are you doing?

--
Michael Press