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
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[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.