born2pdl
03-25-09, 07:30 PM
60T?
http://www.ksl.com/index.php?nid=218&ad=5964206&cat=409&lpid=
http://www.ksl.com/index.php?nid=218&ad=5964206&cat=409&lpid=
Tandem Cycling - Holy Classic Chainring!
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SDS
03-26-09, 08:30 AM
At that point in time it may not have been possible to get 11T and 12T rear cogs. The other route to high gearing was large chainrings. Given that FD capacity is relatively fixed, this meant giving up a wide range of ratios on the front. Large front rings are not as advantageous as small rear cogs.
The T.A. Cyclotouriste crankset was light, came in a wide range of sizes (150 to 185mm crankarms), and was not FD friendly. The chainrings were too close together, and the ultra-small bolt pattern combined with the flexible chainrings, meant that the rings flexed a lot when shifts were attempted, and without diligent power reductions combined with cautious shifting, an overshift was likely. The 144mm bolt circle Campy SR copy five arm T.A. cranksets were a better choice. I know those were available in the early eighties, but I don't know about before that.
You can probably still get Cyclotouriste parts from places like Mel Pinto Imports, and Peter White Cycles, though it is likely to be special order.
Incidentally, seat-tube water bottle boss locations are typically only just above the FD clamp location. Larger chainrings sizes quickly run the FD clamp into the water bottle boss.
Modern T.A. equipment is much nicer, STI compatible, and still comes in a wide range of crankarm lengths. Along the way, though, the ultra-low Q (pedal hole spacing width) had to be given up--STI requires a certain ring spacing, and a larger space between the outside ring and the inside edge of the crankarm.
The T.A. Cyclotouriste crankset was light, came in a wide range of sizes (150 to 185mm crankarms), and was not FD friendly. The chainrings were too close together, and the ultra-small bolt pattern combined with the flexible chainrings, meant that the rings flexed a lot when shifts were attempted, and without diligent power reductions combined with cautious shifting, an overshift was likely. The 144mm bolt circle Campy SR copy five arm T.A. cranksets were a better choice. I know those were available in the early eighties, but I don't know about before that.
You can probably still get Cyclotouriste parts from places like Mel Pinto Imports, and Peter White Cycles, though it is likely to be special order.
Incidentally, seat-tube water bottle boss locations are typically only just above the FD clamp location. Larger chainrings sizes quickly run the FD clamp into the water bottle boss.
Modern T.A. equipment is much nicer, STI compatible, and still comes in a wide range of crankarm lengths. Along the way, though, the ultra-low Q (pedal hole spacing width) had to be given up--STI requires a certain ring spacing, and a larger space between the outside ring and the inside edge of the crankarm.
zonatandem
03-26-09, 12:59 PM
Believe TA actually had even larger chainrings
We used TA 56T chainring back in the mid-70s. As stated small rear cogs were then 14T.
To get around lack of extra long-cage front der., we had a steel Suntour front der. on which we had an extension welded on to the cage. Worked fine for us.
We used TA 56T chainring back in the mid-70s. As stated small rear cogs were then 14T.
To get around lack of extra long-cage front der., we had a steel Suntour front der. on which we had an extension welded on to the cage. Worked fine for us.
Onegun
03-26-09, 02:27 PM
Believe TA actually had even larger chainrings
We used TA 56T chainring back in the mid-70s. As stated small rear cogs were then 14T.
To get around lack of extra long-cage front der., we had a steel Suntour front der. on which we had an extension welded on to the cage. Worked fine for us.
Kee-rect you are. Here's a pic of a fellow's 72T chainring that posts occasionally on the tandem@hobbes list. He lives and rides around a lot of mountains, many times with a double-male team. He's clocked over 70mph on his tandems many times, and is equipped to climb back up the mountain as well. Note the quad chainring setup, with a front derailleur he made in his machine shop to handle the throw.
http://www.tandemrides.com/images/72T.jpg
We used TA 56T chainring back in the mid-70s. As stated small rear cogs were then 14T.
To get around lack of extra long-cage front der., we had a steel Suntour front der. on which we had an extension welded on to the cage. Worked fine for us.
Kee-rect you are. Here's a pic of a fellow's 72T chainring that posts occasionally on the tandem@hobbes list. He lives and rides around a lot of mountains, many times with a double-male team. He's clocked over 70mph on his tandems many times, and is equipped to climb back up the mountain as well. Note the quad chainring setup, with a front derailleur he made in his machine shop to handle the throw.
http://www.tandemrides.com/images/72T.jpg
rodar y rodar
03-27-09, 10:38 AM
Wow, that`s pretty impressive. It looks like he built the whole FD, not just the cage.
Onegun
03-27-09, 04:28 PM
Wow, that`s pretty impressive. It looks like he built the whole FD, not just the cage.
He did. It's a dual cable design that does not rely on a spring to make it shift either way. He operates it from a bar-end that he machined with a cable going either direction to achieve the push-me/pull-you design.
He did. It's a dual cable design that does not rely on a spring to make it shift either way. He operates it from a bar-end that he machined with a cable going either direction to achieve the push-me/pull-you design.