Mountain bike design question.

Quoted post said:

Originally posted by Chris Zacho "Th
I was at my LBS looking at some of the elaborate methods of
attaching rear shocks to frames, and thought: "Why doesn't
somebody just turn the _frame_ into a shock?" Use a
wishbone seat stay attached to a plunger that fits into the
top tube, the body of which makes up the rest of the Shock
Absorber? Sort of like Cannondale's HeadShok. Pivots at the
dropouts and at the top of the wishbone would compesate for
changing angles.

This seens to be such a simple and relatively
lightweight solution. SOMEbody must have tried it, so
why didn't it work?

"May you have the wind at your back. And a really low gear
for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner geocities.comczcornerOpen ↗

The newer Fuji Dynamic comfort bikes have a similar style suspension. Pivots at the back of the BB instead of dropouts. Wishbone forks into a short stem plunger at the back of the seat tube. It’s a really neat way to put in a lightweight low travel suspension without sacrificing much torsional rigidity, great for road use.

http://www.bikesdirect.com/products/02fuji/fuji_dynamic.htm

The Huffy Luna comfort bike (Actually more like a heavy full suspension 6 speed cruiser) has this same suspension. There is another bike out there that last summer/fall was sold through Target (I think they no longer carry it) that a neighbor has, I’ll check back on the brand.

http://www.thesportsauthority.com/product/index.jsp?productId=979082&cp&searchId=10351634240&keywords=luna+bike&y=13&x=10&parentPage=search

I’ve been considering modifying a bike rear for a suspension like the Fuji. Cut the chain stays add a hinge joint there, cut the seat stay add elastomer or coil spring. My concern is making/acquiring a retrofitably hinge with enough torsional rigidity on the bike’s roll axis that’s not gigantic.

Don’t think on a retrofit placing the pivot at the dropout would work since the arc the new pivot would make would not be traveling on the axis of the spring/damper without major rework of the rear geometry. But that could be designed into an initial build.

In <[email hidden]>,
[email hidden] (Chris Zacho "The Wheelman"😉 opined:

Quoted message said:

"Why doesn't somebody just turn the _frame_ into a shock?"

Lots have, with the result being called a "softail" frame.
Most of 'em have short travel and firm rides, which is quite
different from what you get in a full suspension frame.

--
Dave Salovesh [email hidden] (REPLACE example WITH
mindspring TO EMAIL ME)

[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

I was at my LBS looking at some of the elaborate methods
of attaching rear shocks to frames, and thought: "Why
doesn't somebody just turn the _frame_ into a shock?" Use
a wishbone seat stay attached to a plunger that fits into
the top tube, the body of which makes up the rest of the
Shock Absorber? Sort of like Cannondale's HeadShok. Pivots
at the dropouts and at the top of the wishbone would
compesate for changing angles.

This seens to be such a simple and relatively
lightweight solution. SOMEbody must have tried it, so
why didn't it work?

Moots did: (from moots.comhistory2.phpOpen ↗ )

"Nineteen eighty-seven marked a huge turning point for
Moots: the company built its first YBB. The YBB ("Why Be
Beat?"😉 was the industry's first "soft-tail" design; its
rear triangle incorporated an elastomer suspension system
that provided one-inch of travel. There were no maintenance-
intensive pivot points or complicated shocks; there wasn't
even a front suspension fork. "We were playing with the YBB
before Rock Shox were available," says Eriksen. "We used to
ride rigid front ends with the soft-tail in back. And we
knew we were onto something."

"Indeed, they were: the soft-tail design went on to become
perhaps the most copied suspension frame design in the
history of cycling and the YBB quickly became Moots's
signature bike."

Jeff

Quoted post said:

Originally posted by Jeff Wills
[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

I was at my LBS looking at some of the elaborate methods
of attaching rear shocks to frames, and thought: "Why
doesn't somebody just turn the _frame_ into a shock?" Use
a wishbone seat stay attached to a plunger that fits into
the top tube, the body of which makes up the rest of the
Shock Absorber? Sort of like Cannondale's HeadShok. Pivots
at the dropouts and at the top of the wishbone would
compesate for changing angles.

This seens to be such a simple and relatively
lightweight solution. SOMEbody must have tried it, so
why didn't it work?

Moots did: (from moots.comhistory2.phpOpen ↗ )

"Nineteen eighty-seven marked a huge turning point for
Moots: the company built its first YBB. The YBB ("Why Be
Beat?"😉 was the industry's first "soft-tail" design; its
rear triangle incorporated an elastomer suspension system
that provided one-inch of travel. There were no maintenance-
intensive pivot points or complicated shocks; there wasn't
even a front suspension fork. "We were playing with the YBB
before Rock Shox were available," says Eriksen. "We used to
ride rigid front ends with the soft-tail in back. And we
knew we were onto something."

"Indeed, they were: the soft-tail design went on to become
perhaps the most copied suspension frame design in the
history of cycling and the YBB quickly became Moots's
signature bike."

Jeff

How did Moots avoid metal fatique on the chainstays with no pivots?

Quoted message said:

Quoted message said:

[email hidden] (Chris Zacho "The Wheelman"😉
wrote in message news:<24560-4054894C-180@storefull-
3172.bay.webtv.net>...

Quoted message said:

I was at my LBS looking at some of the elaborate
methods of attaching rear shocks to frames, and
thought: "Why doesn't somebody just turn the _frame_
into a shock?"

-snip-

Quoted message said:

Jeff Wills said:

Moots did: (from moots.comhistory2.phphttOpen ↗
p://www.moots.com/history2.php ) "Nineteen eighty-
seven marked a huge turning point for Moots: the
company built its first YBB. The YBB ("Why Be Beat?"😉
was the industry's first "soft-tail" design; its rear
triangle incorporated an elastomer suspension system
that provided one-inch of travel. There were no maintenance-
intensive pivot points or complicated shocks

-snip-

meb said:

How did Moots avoid metal fatique on the chainstays with
no pivots?

Merlin had a similar design which relied on stay flex. Never
saw one break, and they were popular for a while.

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

meb said:

How did Moots avoid metal fatique on the chainstays with
no pivots?

The chainstay is like a big spring, which can safely be bent
that far without problems. Also, the YBB's travel is pretty
short. Because titanium is springier than steel, the Moots
can have longer travel than steel bikes of this type, such
as Ritchey's. Note how titanium eyeglass frames can be bent
and twisted, compared to steel ones.

Both Ibis and Merlin have built conventional, longer-travel
bikes without pivots, using flexible stays.

Some race cars actually use a flexible titanium plate, in
place of a suspension ball joint. No slop, theoretically
lasts forever, and cheap to replace anyway if you don't want
to take chances!

Matt O.

[email hidden] (Chris Zacho "The Wheelman"😉 wrote in message news:<[email hidden]>...

Quoted message said:

I was at my LBS looking at some of the elaborate methods
of attaching rear shocks to frames, and thought: "Why
doesn't somebody just turn the _frame_ into a shock?" Use
a wishbone seat stay attached to a plunger that fits into
the top tube, the body of which makes up the rest of the
Shock Absorber? Sort of like Cannondale's HeadShok. Pivots
at the dropouts and at the top of the wishbone would
compesate for changing angles.

This seens to be such a simple and relatively
lightweight solution. SOMEbody must have tried it, so
why didn't it work?

John Castellano will provide you with info...

www.castellanodesigns.com
--
Jonesy