Hub brake snatches

Daniel Towner said:

Hi all,

I have hub-brakes on my two front wheels (Windcheetah!) and one of
them has developed an annoying habit of snatching. If I brake fairly
gently, both wheels will slow down equally and I'll come to a smooth
stop. If I brake harder, one wheel will lock up completely, which then
tries to spin the trike. This behaviour is worse in damp weather. If I
loosen the faulty brake I can stop it from snatching, but then its so
loose that under gentle braking it does nothing. I can't see any
obvious damage to the braking surface inside the hub, but the edges of
the brake shoes look ragged - not squared off as on the good brake.

Any ideas how I can cure this?

thanks,

dan.

if the brakearm returns normally it could be caused by wear changing the
geometry of the brake. Drumbrakes are fairly sensitive to changes in
geometry causing it to self-energize. New and thicker shoes should cure it.
/MArten

Daniel Towner said:

I have hub-brakes on my two front wheels (Windcheetah!) and one of
them has developed an annoying habit of snatching. If I brake fairly
gently, both wheels will slow down equally and I'll come to a smooth
stop. If I brake harder, one wheel will lock up completely, which then
tries to spin the trike. This behaviour is worse in damp weather. If I
loosen the faulty brake I can stop it from snatching, but then its so
loose that under gentle braking it does nothing. I can't see any
obvious damage to the braking surface inside the hub, but the edges of
the brake shoes look ragged - not squared off as on the good brake.

Any ideas how I can cure this?

I don't know the details of the cable routing on the Windcheetah, but
this sounds as if the brake mechanism plate is not properly secured, and
is being rotated in such a way as to increase pull on the cable.

I would suggest careful examination of this, but without seeing it I
can't get more specific.

There are right-hand and left-hand drum brake units available, and you
should have a mirror image pair on your trike...do you?

Sheldon "Symmetry" Brown
+-------------------------------------------+
| Good judgment comes from experience, |
| and experience comes from bad judgment. |
| --Fred Brook |
+-------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

[email hidden] (Daniel Towner) wrote in message news:<[email hidden]>...

Quoted message said:

Hi all,

I have hub-brakes on my two front wheels (Windcheetah!) and one of
them has developed an annoying habit of snatching. If I brake fairly
gently, both wheels will slow down equally and I'll come to a smooth
stop. If I brake harder, one wheel will lock up completely, which then
tries to spin the trike. This behaviour is worse in damp weather. If I
loosen the faulty brake I can stop it from snatching, but then its so
loose that under gentle braking it does nothing. I can't see any
obvious damage to the braking surface inside the hub, but the edges of
the brake shoes look ragged - not squared off as on the good brake.

Any ideas how I can cure this?

thanks,

Hmmm... sounds like a question for Bob Dixon, but I'd start by
thoroughly cleaning the inside the drum with an evaporating solvent
(alcohol or acetone) and dressing the brake shoes with light
sandpaper.

jeff

On 22 Apr 2004 02:49:19 -0700, [email hidden] (Daniel Towner)

may have said:

Any ideas how I can cure this?

In powered vehicle applications, this is usually a sign of
contamination of the friction material. Unfortunately, it is usually
futile to try to remove the contamination. I'd replace the brake
shoes and throughly clean the inside surface of the drums.

If you want to try something short of that, use emery cloth to deglaze
the inside of the drum, use sandpaper to scuff the surface of the
shoes, and try to clean the friction material's surface with a
degreaser that will not leave a residue. In my opinion, it probably
won't work, but you might get lucky.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

Quoted message said:

I have hub-brakes on my two front wheels (Windcheetah!) and one of
them has developed an annoying habit of snatching. If I brake fairly
gently, both wheels will slow down equally and I'll come to a smooth
stop. If I brake harder, one wheel will lock up completely, which then
tries to spin the trike. This behaviour is worse in damp weather. If I
loosen the faulty brake I can stop it from snatching, but then its so
loose that under gentle braking it does nothing. I can't see any
obvious damage to the braking surface inside the hub, but the edges of
the brake shoes look ragged - not squared off as on the good brake.

In the end I used emery paper to aggressively rub down the braking
surfaces, and then cleaned the inside of the hubs with acetone. The
brakes no longer [censored], and they perform better than they have done
in ages.

Thanks for you help.

dan.