Shimano FF system freewheel question

Hi.
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).
Harris Cycle has thread-on freewheels to change/add gearing that will fit
my rear wheel.
My question is: does a Shimano freewheel have the ratchety stuff in it or
is the ratchety stuff in a regular hub that the freewheel threads on to?
I ask because it seems to me I could build a multi-speed 'fixed-gear' by
replacing the Shimano FF front BB and/or cranks with regular BB and/or
cranks, but only if the rear freewheel remains fixed as it is now.
Am I making any sense?
Hello, is this thing on?

Thanks.

On Sun, 24 Jul 2005 11:34:37 -0400, "tzed250"
wrote:

Hi.
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).

I have long believed that this "feature" had to have been devised by
someone who wanted to try to make a der system act more like a
gearhub. There's no good reason for it in my estimation.

Harris Cycle has thread-on freewheels to change/add gearing that will fit
my rear wheel.

So does your local bike shop, for that matter.

My question is: does a Shimano freewheel have the ratchety stuff in it

Okay, I think there's some basic background info that needs to be
covered. Your bike doesn't have a freewheel on the rear. Freewheels
get their name from the fact that they have the "ratchety stuff" in
them, allowing them to freewheel when the rider stops pedalling. Your
bike's freewheeling is done in the front sprockets instead. Yes, the
regular freewheels will fit on your bike's rear hub, defeating the
purpose of the front freewheel in the process. If you want to make a
non-freewheel out of a current freewheel, take it apart, clean out the
grease, fill it with epoxy and reassemble...or have a welder run a
bead on the back to lock the inner and out halves together.

or
is the ratchety stuff in a regular hub that the freewheel threads on to?
I ask because it seems to me I could build a multi-speed 'fixed-gear' by
replacing the Shimano FF front BB and/or cranks with regular BB and/or
cranks, but only if the rear freewheel remains fixed as it is now.
Am I making any sense?
Hello, is this thing on?

(sigh) Okay, first, a fixie done this way may have problems with the
rear cluster unscrewing; I'd advise against it unless you plan to
install and use hand brakes. Second, you'd have to carry a bunch of
individual links to add or subtact length from the chain when
(messily) swapping to a different gear ratio. You can't use a
derailleur with a fixie because the excess chain length will droop
from the top run when not applying forward power, possibly causing
chain jamming in the rear. Third, the dropout isn't anywhere near
horizontal enough to allow proper chain tension adjustment on that
frame in every gear combination. And fourth, only one or two of the
sprockets on the rear will line up with the sprocket(s) on the front
anyway.

In other words, it'll only sort of work. If you want a real fixie,
use the stuff that's designed for the purpose.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Comments interspersed...

Werehatrack wrote:
On Sun, 24 Jul 2005 11:34:37 -0400, "tzed250"
wrote:

Hi.
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).

I have long believed that this "feature" had to have been devised by
someone who wanted to try to make a der system act more like a
gearhub. There's no good reason for it in my estimation.

Harris Cycle has thread-on freewheels to change/add gearing that will fit
my rear wheel.

So does your local bike shop, for that matter.

My question is: does a Shimano freewheel have the ratchety stuff in it

Okay, I think there's some basic background info that needs to be
covered. Your bike doesn't have a freewheel on the rear. Freewheels
get their name from the fact that they have the "ratchety stuff" in
them, allowing them to freewheel when the rider stops pedalling. Your
bike's freewheeling is done in the front sprockets instead. Yes, the
regular freewheels will fit on your bike's rear hub, defeating the
purpose of the front freewheel in the process. If you want to make a
non-freewheel out of a current freewheel, take it apart, clean out the
grease, fill it with epoxy and reassemble...or have a welder run a
bead on the back to lock the inner and out halves together.


Kind of wrong, Were-

The FF rear cog set (I hesitate to call it a "freewheel") has a clutch
mechanism. This allows the wheel to continue turning if something (a
stick or pants cuff) gets caught in the chain or derailleur. It's a
safety system, and a smart one.

If the rear cog set were replaced with a modified freewheel as Were
suggests, a jammed chain will result in a locked-up wheel and/or a bent
derailleur. Bad things, all. See Were's comments below.


or
is the ratchety stuff in a regular hub that the freewheel threads on to?
I ask because it seems to me I could build a multi-speed 'fixed-gear' by
replacing the Shimano FF front BB and/or cranks with regular BB and/or
cranks, but only if the rear freewheel remains fixed as it is now.
Am I making any sense?
Hello, is this thing on?

On, off, on and on...



(sigh) Okay, first, a fixie done this way may have problems with the
rear cluster unscrewing; I'd advise against it unless you plan to
install and use hand brakes. Second, you'd have to carry a bunch of
individual links to add or subtact length from the chain when
(messily) swapping to a different gear ratio. You can't use a
derailleur with a fixie because the excess chain length will droop
from the top run when not applying forward power, possibly causing
chain jamming in the rear. Third, the dropout isn't anywhere near
horizontal enough to allow proper chain tension adjustment on that
frame in every gear combination. And fourth, only one or two of the
sprockets on the rear will line up with the sprocket(s) on the front
anyway.

In other words, it'll only sort of work. If you want a real fixie,
use the stuff that's designed for the purpose.

I agree with Mr. Were. A multi-speed fixie is only really possible with
a Sturmey-Archer ASC hub: http://www.sheldonbrown.com/asc.html .

Jeff

On 24 Jul 2005 13:55:32 -0700, "JeffWills"
wrote:

Werehatrack wrote:
Okay, I think there's some basic background info that needs to be
covered. Your bike doesn't have a freewheel on the rear. Freewheels
get their name from the fact that they have the "ratchety stuff" in
them, allowing them to freewheel when the rider stops pedalling. Your
bike's freewheeling is done in the front sprockets instead. Yes, the
regular freewheels will fit on your bike's rear hub, defeating the
purpose of the front freewheel in the process. If you want to make a
non-freewheel out of a current freewheel, take it apart, clean out the
grease, fill it with epoxy and reassemble...or have a welder run a
bead on the back to lock the inner and out halves together.


Kind of wrong, Were-

The FF rear cog set (I hesitate to call it a "freewheel") has a clutch
mechanism. This allows the wheel to continue turning if something (a
stick or pants cuff) gets caught in the chain or derailleur. It's a
safety system, and a smart one.

While that's what is supposed to be the way it works, the two I've had
(one a trash pile recovery, the other a $10 Goodwill unit) both had
rear clusters that were effectively rotted in place. While it's
*supposed* to be able to slip if the chain tension goes above a
certain point, it appears that a general lack of maintenance can
stiffen that slip clutch to the point that it doesn't work as
intended.

If the rear cog set were replaced with a modified freewheel as Were
suggests, a jammed chain will result in a locked-up wheel and/or a bent
derailleur. Bad things, all. See Were's comments below.

Yup, and I should have noted that if the original cluster wears out,
locking a freewheel to keep the shift-while-not-pedalling feature
alive is a Really Bad Idea. Once the original cluster goes south, the
only practical choice is to toss a regular freewheel on there and do
without the wierd chain-always-moves bit. (For a while, a replacement
could be had from the people who were disposing of the remaining
spares of the clusters from the ill-fated Autobike, but the last time
I looked, it appeared that those were all gone.)


--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Werehatrack wrote:

While that's what is supposed to be the way it works, the two I've had
(one a trash pile recovery, the other a $10 Goodwill unit) both had
rear clusters that were effectively rotted in place. While it's
*supposed* to be able to slip if the chain tension goes above a
certain point, it appears that a general lack of maintenance can
stiffen that slip clutch to the point that it doesn't work as
intended.

Okley-dokley... I think we're on the same page. Age, dried grease, and
general decrepitude would lock up a FF cog set real good.

I wish I could find an exploded view of the FF "freewheel". They were
actually pretty neat inside. Here's some external views:
http://www.sheldonbrown.com/shimano1982/pages/35.html
Apparently there were some 32 tooth large cogs available, but I *think*
they were used on the 5-speed Schwinns. The 10-speeds came with 14-28
sets.

Jeff

tzed250 wrote:

Hi.
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).
Harris Cycle has thread-on freewheels to change/add gearing that will fit
my rear wheel.
My question is: does a Shimano freewheel have the ratchety stuff in it or
is the ratchety stuff in a regular hub that the freewheel threads on to?
I ask because it seems to me I could build a multi-speed 'fixed-gear' by
replacing the Shimano FF front BB and/or cranks with regular BB and/or
cranks, but only if the rear freewheel remains fixed as it is now.
Am I making any sense?
Hello, is this thing on?

Your rear hub has normal freewheel threads. If your FFS
freewheel is six speed you can replace it with a six speed
'normal' freewheel as long as you also install a 'normal'
crank. Your FFS freewheel isn't fixed - each cog
individually has a ratchet assembly, albeit much stiffer
than a 'regular' freewheel. Try pushing one cog and see!

Your BB has normal threads. After removing the 'Selecta"
splined cranks and spindle, your cups unscrew with a Shimano
early model spline freewheel remover. "Normal" BB cups or a
cartridge ( whatever is suitable to your replacement crank)
will install without any odd measures.

So, yes you can change it over but you'll need to do both
freewheel and crank together.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

On Sun, 24 Jul 2005 11:34:37 -0400, "tzed250"
wrote:
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).
-snip-

Werehatrack wrote:
-snip-
Third, the dropout isn't anywhere near
horizontal enough to allow proper chain tension adjustment on that
frame in every gear combination. And fourth, only one or two of the
sprockets on the rear will line up with the sprocket(s) on the front
anyway.
In other words, it'll only sort of work. If you want a real fixie,
use the stuff that's designed for the purpose.

Good generally but his frame will easily allow use of a
single gear - there is plenty of adjustment at the frame end.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

tzed250 wrote:
Hi.
My Schwinn has the Shimano FF system (drive train continues to spin while
coasting so gears could be changed without pedaling).
Harris Cycle has thread-on freewheels to change/add gearing that will fit
my rear wheel.
My question is: does a Shimano freewheel have the ratchety stuff in it or
is the ratchety stuff in a regular hub that the freewheel threads on to?
I ask because it seems to me I could build a multi-speed 'fixed-gear' by
replacing the Shimano FF front BB and/or cranks with regular BB and/or
cranks, but only if the rear freewheel remains fixed as it is now.
Am I making any sense?
Hello, is this thing on?

Thanks.

others have answered your questions about FF. I can tell you that
multi-speed fixed gear does work and you don't have to dig garbage
out of a junkyard.

I JBWelded a NOS freewheel's guts and threadlocked it onto the hub.
I removed the bearings and didn't align the parts' rotational
axes as well as I would have liked. This has not been any problem.
I moved the 52t chainring onto the inside of a (conventional) crank.
This was my sole concession to chainline.

I only put a few hundred miles on it before I swiped the brakes for
a more conventional project. I did hilly runs to stores but mostly
training out on the flats where shifting was handy if I turned and
discovered wind.

I only used two of the cogs, one more (with that chainring) should
provide at least as good of a chainline. The horiz dropouts provide
plenty of adjust for two cogs, installing a second quick link had
been suggested as a way to "reach" one or two more cogs. I haven't
done that.

Despite a dozen quick field "settings" of the rear wheel (during
which sloppiness would have been expected due to haste) I have not
dechained. Since the chainline looks pretty good but not great
I have to guess that the large gears get the credit. The people
running smaller chainrings seem to be sensitive to the chainline
issue.

Before I did this I had calculated about a two to one margin
on threadlocker strength based on my full weight on the pedal,
conservative area (ignored increased area due to threads) and
zero torque transfer through friction.

Ed