Singlespeed/fixed gear question

Paul wrote:
So why do all fixed hubs come with solid axles and nuts? (I'm not trying to
be snarky - i'm pleased to be better informed and corrected if I'm wrong)

It might see higher peak loads with the double, but those times are very
rare.

When riding with a multi geared bike, one typically starts in a lower gear.
The highest forces do come from the highest gears, but the rider rarely
starts off in a high gear.

The axles come nutted mainly for tradition/style reasons. Proper track
bikes are not allowed to have QR axles for claimed reasons that they
represent an impalement risk in a crash, but really because track folks
are pretty retro-grouch. (nothing wrong with that mind you) While
it's true that a nutted axle can clamp tighter than a QR, a QR clamps
tight enough that it doesn't matter. I suspect a side benefit with a
nutted axle is that it is easier to respace for different rear spacings
which is a common issue on fixed-gear conversions.

And the force generated at the axle is indeed highest in a low gear,
not a high one. Imagine a simplified drive-train, you have a single
lever attached to the rear hub. A longer lever (bigger and thus lower
gear) will allow you to put more torque on the hub, a shorter lever
will limit the torque. If you extend this model and add a second
lever and a connecting rod (bb, chainring, and chain) you will see that
the relative sizes of teh levers determines the torque (and thus chain
tension which is the real thing we are looking at).

Even if you do not accecpt the above reasoning, most bicycle have
gears that are both higher and lower than a fixed gear, so explain how
a QR would work there and not for a fixed?

Fixed gears have the added force of being able to back-pedal for
braking, but the amount of force that can be applied while back
pedaling is smaller than can be applied forward and so is of no concern
for this model. Furthur, the force is significantly less than can be
seen on bicycles with disc brakes, which also work fine with QRs.

-Tim

Paul R wrote:
"Paul Hobson"

I had a master plan:


The C. Itoh would need a new saddle, probably new wheels/hubs, and I'd
like a new headset/stem/bars/etc if I were to ride it consistently. The
frame seems to be in decent shape though.

Here are some photos:
http://www.prism.gatech.edu/~gtg611a/drop_out.JPG
http://www.prism.gatech.edu/~gtg611a/bike_CItoh.JPG


Hi Paul,

I don't think those dropouts are strong enough for a fixed gear hub - the
forces on the frame are much higher than for a geared bike.

You might want to take the frame to a good bike store - where there's
someone who knows about street riding on a fixie.

Cheers,
paul





Paul (you),

Thanks so much for the valuable input. I'll definitely check that out.
I ordered a new threaded stem from my LBS today along and picked up
some new brake pads/cables. I think I might buy a nicer saddle and put
that on my nice (relatively) bike and put it's on the beater.

I'm not sold on the fixie idea yet, but I definitely want a single speed
set-up. It would seem that the dropouts' strength would still be any
issue. Right?

Also, I only weigh 58 kg (128 lbs). I haven't done a fully
dynamics/mechanics of materials analysis of the system yet, but it would
seem that my relatively light weight would help the situation some.

thanks again,

\\paul (me)

--
Paul M. Hobson
Georgia Institute of Technology
http://www.underthecouch.org
..:you may want to fix my email
address before you send anything:.

Fixed gear riding sounds scarier on paper than in real life. I ride
fixed almost exclusively now in pittsburgh which is about as hilly as
cities come. There are a handful of hills (15% for more than a few
hundred yards) that I basically can't ride up, but honestly they are
rare and easily avoided. Going down is not as hard as people claim,
provided that you have brakes and are not relying on back pressure. It
takes a bit of effort to prevent yourself from being tossed off the
saddle, but give it 3 rides and it'll seem totally natural.

I run 42x16 which is a reasonable balance. I'd like to get strong
enough that I can push 44x16 uphill because it would be nicer on the
flats, but there is this one last hill up to work that is a complete
bear.

check www.fixedgeargallery.com for inspiration

Cheers

-Tim

buckyllama wrote:
Fixed gear riding sounds scarier on paper than in real life. I ride
fixed almost exclusively now in pittsburgh which is about as hilly as
cities come. There are a handful of hills (15% for more than a few
hundred yards) that I basically can't ride up, but honestly they are
rare and easily avoided. Going down is not as hard as people claim,
provided that you have brakes and are not relying on back pressure. It
takes a bit of effort to prevent yourself from being tossed off the
saddle, but give it 3 rides and it'll seem totally natural.

I run 42x16 which is a reasonable balance. I'd like to get strong
enough that I can push 44x16 uphill because it would be nicer on the
flats, but there is this one last hill up to work that is a complete
bear.

check www.fixedgeargallery.com for inspiration

Cheers

-Tim


Tim,

Thanks for the response/general info. Right now, I looking to simply
get the bike working again (it did until I took the whole thing apart).
I trying to get the cottered (sp??) cranks off right now with no luck.
Once I get all the general stuff done (new saddle, stem/bars, brakes,
etc) then I'll decide if I want to go fixed gear or not.

Now, I don't know what's worse: me riding a fixed gear b/c it's "cool"
in Atlanta right now, or me /not/ riding a fixed gear because I don't
want the "cool" kids to think I'm trying to be like them. Oh my...such
first world problems I have...

--
Paul M. Hobson
Georgia Institute of Technology
http://www.underthecouch.org
..:you may want to fix my email
address before you send anything:.