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#11
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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 |
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#12
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Shorter cranks on Double Vision
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 |
#13
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Shorter cranks on Double Vision
"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 |
#14
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Shorter cranks on Double Vision
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 |
#15
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Shorter cranks on Double Vision
"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. |
#16
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Shorter cranks on Double Vision
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#17
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Shorter cranks on Double Vision
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 |
#18
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Shorter cranks on Double Vision
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) |
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