Shorter cranks on Double Vision

"Perry" wrote in message ...
There is positively NO WAY I will ever give up IPS. Not until they pry my
cold dead toes from my Frogs. With a big battleship hulking bike like the
Double Vision, there are just too many needs for the IPS.
Perry

:-))

If you're not going to give up IPS, then drilling and tapping the
cranks is just about your only choice. It'll still require a good
machinist to do the deed, but it's not terrible complex.

They'll need to be shortened quite a bit, though, since enough
material needs to be left on the outside of the pedal eye to keep them
from cracking. You'll probably end up with 145mm or 150mm cranks,
kind of like these cranks from DaVinci Designs:
http://www.davincitandems.com/images/xt3.jpg

Mark Stonich has shortened cranks from a variety of sources: here's a
little reading material:
http://mnhpva.org/meetings/July_03/Crank.html
http://bikesmithdesign.com/Short_Cranks/Dotek.html


Jeff

Perry, how about a set of crank shorteners from the Hostel shoppe? they
would make the "Q" a little wider, but all in all, a less complicated
and hassle free modification


Perry wrote:

Hi Earl,
I do have IPS. (and I believe they're tapered) Why does that make a
difference?
Perry

"Guess Who I Am" wrote in message
...

Hello:
if you donot have IPS or splined crank i know of a machine shop that will

drill

and tap them out for you.
if intrested please e-mail me back.
Thank you Earl
GRR,RANS V2
Ti Rush,Ti Pursuit

"Jeff Wills" wrote in message
om...
"Perry" wrote in message
...
There is positively NO WAY I will ever give up IPS. Not until they pry
my
cold dead toes from my Frogs. With a big battleship hulking bike like
the
Double Vision, there are just too many needs for the IPS.
Perry

:-))

If you're not going to give up IPS, then drilling and tapping the
cranks is just about your only choice. It'll still require a good
machinist to do the deed, but it's not terrible complex.

They'll need to be shortened quite a bit, though, since enough
material needs to be left on the outside of the pedal eye to keep them
from cracking. You'll probably end up with 145mm or 150mm cranks,
kind of like these cranks from DaVinci Designs:
http://www.davincitandems.com/images/xt3.jpg

Mark Stonich has shortened cranks from a variety of sources: here's a
little reading material:
http://mnhpva.org/meetings/July_03/Crank.html
http://bikesmithdesign.com/Short_Cranks/Dotek.html


I'm using a set of Mark's 155s drilled and tapped for triople rings. The
crank and matching rings were about $150. He did a great job.

I've never even seen an IPS-equipped bike, so I can't tell you if these
cranks could be modified to work. I'm sure Mark knows, and could probably to
the machining for you.

Tom Thompson

Just trying to learn something here. Is the IPS integral to the
crank? Meaning you buy it all together and have limited choice on
crank length. Don

"Tom Thompson" wrote in message ...
"Jeff Wills" wrote in message
om...
"Perry" wrote in message
...
There is positively NO WAY I will ever give up IPS. Not until they pry
my
cold dead toes from my Frogs. With a big battleship hulking bike like
the
Double Vision, there are just too many needs for the IPS.
Perry

:-))

If you're not going to give up IPS, then drilling and tapping the
cranks is just about your only choice. It'll still require a good
machinist to do the deed, but it's not terrible complex.

They'll need to be shortened quite a bit, though, since enough
material needs to be left on the outside of the pedal eye to keep them
from cracking. You'll probably end up with 145mm or 150mm cranks,
kind of like these cranks from DaVinci Designs:
http://www.davincitandems.com/images/xt3.jpg

Mark Stonich has shortened cranks from a variety of sources: here's a
little reading material:
http://mnhpva.org/meetings/July_03/Crank.html
http://bikesmithdesign.com/Short_Cranks/Dotek.html


I'm using a set of Mark's 155s drilled and tapped for triople rings. The
crank and matching rings were about $150. He did a great job.

I've never even seen an IPS-equipped bike, so I can't tell you if these
cranks could be modified to work. I'm sure Mark knows, and could probably to
the machining for you.

Tom Thompson

Some 175s can be retapped to 152s if there is enough material around
the new hole. Usually there is not. I wouldn't use IPS if it was
free, had no extra parts to fail, and didn't add weight. Especially
if the alternative was an end to knee pain.

(Don) wrote in message . com...
Just trying to learn something here. Is the IPS integral to the
crank? Meaning you buy it all together and have limited choice on
crank length. Don

Yes. Vision's Independent Pedaling System inserts a freewheel
mechanism between the crankarms and the chainrings on both the
captain's and the stoker's cranksets. That way either rider can pedal
or coast at their pleasure.

Jeff

Jeff Wills wrote:
Yes. Vision's Independent Pedaling System inserts a freewheel
mechanism between the crankarms and the chainrings on both the
captain's and the stoker's cranksets. That way either rider can pedal
or coast at their pleasure.

Shades of the Shimano FF (Front Freewheel) system of the '70s. However,
the only FF bike I ever rode, a 1977 Schwinn Caliente that I used to
use, had permanently integrated chainrings and Ashtabula-style crankarms
and BB. It was basically a Varsity with a fancy drivetrain; it also had
the Positron rear mech, Shimano's first attempt at indexed shifting.

FF also had an oddball cluster with a one-way slip clutch on each
sprocket, in case the chain jammed. A flange on the cluster had a
stamped warning that it was for use only with FF.

With FF+Positron, you could shift at any time, but starting off was
awkward if you downshifted while stopped. The Positron also used a
solid shift cable, which tended to break from fatigue, either at the
shifter or at the derailleur. One of today's 7- or 8-speed gearhubs
with a conventional crank would be much better from a shift-at-any-time
standpoint. I'm surprised, though, that Shimano never thought of using
the FF cranks for tandem IPS, whether or not the funky cluster was used.

I still have the old Schwinn, but damage/rust on a seat stay and
worn-out teeth on the big ring have made it unsafe to ride.
--
Russ --kill the wabbit to despam
"No, see, it's not something you 'experience' - it's something that you
posess. You know, that fine 'recumbent butt' - a distinguishing
characterisitic of a recumbent cyclist." -Geoff Adams, on 'BROL

Russ Price wrote in message news:pzkob.65809$Tr4.183512@attbi_s03...
Jeff Wills wrote:
Yes. Vision's Independent Pedaling System inserts a freewheel
mechanism between the crankarms and the chainrings on both the
captain's and the stoker's cranksets. That way either rider can pedal
or coast at their pleasure.

Shades of the Shimano FF (Front Freewheel) system of the '70s. However,
the only FF bike I ever rode, a 1977 Schwinn Caliente that I used to
use, had permanently integrated chainrings and Ashtabula-style crankarms
and BB. It was basically a Varsity with a fancy drivetrain; it also had
the Positron rear mech, Shimano's first attempt at indexed shifting.


Not quite- the Calientes of that era had "Positron II". The original
Positron (that was never used on Schwinns, AFAIK) used a dual-cable
system with indexing at the derailleur.

You're right about the IPS being similar to the Front Freewheel
system- almost exactly the same, in fact.

snip
I still have the old Schwinn, but damage/rust on a seat stay and
worn-out teeth on the big ring have made it unsafe to ride.

So go buy an old Varsity and swap out the drivetrain. It all
interchanges. Old Schwinns never die- they're tougher than
cockroaches.

Jeff Wills (Schwinn mechanic 1979-1984)