Bicycle Mechanics - Quad Chain-ring Setup
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05-29-07, 02:47 PM
Has anyone attempted to replace a triple front chain-ring setup with a
Quad Chain-ring setup? Or maybe you have some information or advice to
offer. Im looking to do something like a 30-40-53-65 Quad setup on my recumbent lowracer for a TT latter this year.
05-29-07, 03:54 PM
Cool, that's totally insane! Why are you doing it - have you already switched to a wide-range rear cassette (12-30 or something)? If so, do you really need gear ratios from approximately 1.0 to 5.5? That highest gear would have you pedaling between 7 and 65 mph at an RPM range of 60-100 (by my calculations which I haven't checked, could be wrong). I can't imagine that combination being necessary unless 1) you're riding in the Himalayas, and 2) have an absolute death wish (that 65mph sounds a tad dangerous).
Assuming you're *not* riding in the Himalayas, I can't see the need for anything you can't do on a triple with a wide-range rear cassette.
05-29-07, 04:02 PM
Another BF member, Michel Gagnon, did this. Here's a link (http://www.mgagnon.net/velo/pedalier4.en.shtml) to his website with info about converting to a quad.
05-29-07, 05:06 PM
Thank you for the link. http://mgagnon.net/velo/pedalier4.en.shtml
It provides some usfull information. I made the following observatios:
A standard front derailleur with 22t range can accommodate a 30T to 32T range. But Im willing to try and do surgery on a derailleur to make the cage longer.
The smallest chain-ring at 30t would only be useful on the lowest speeds (larges cogs) because the rear derailleur wouldn’t be able to take up the extra chain slack.
I will need a friction shifter, but a twist shifter might work. So I will try it.
To answer MR U’s questions, Remember that a recumbent racing bike has a different riding profile then something like a Trek Madone diamond frame bike. Were the recumbent rider is not able to stand on the pedals and push hard for extra uphill power. But at speeds over 15mph there is a significant aerodynamic advantage that compensates for this climbing loss. The course I will be pedaling is the Texas Time Trials see http://www.tt24tt.com. It has some rolling hills that I need to compensate for. I did a practice run of 3 laps (60 miles) and I can get up all of the hills in the middle chain-ring, but I need to spin more to pace myself, and I fear that latter laps will require me to drop down into the granny gear because of fatigue. To take advantage of the aerodynamic feature of the recumbent, I want to push the down hills speeds a as higher then I can get with a 54T ring. Yes its insane, like being on a broken roller-coaster. But the high speeds help eat-up the accents.
FYI I have an Optima Baron with triple QRings 30-40-54 (Aero ring) mounted on a custom 200mm (not a misprint) Velokraft.com carbon cranks. This drive-train powers a 650C tire with a Michilan Pro2 23mm tire. I currently have a custom 9speed 11-28 cassette with cogs of 11-12-13-14-15-17-19-24-30. The extra long 200mm crank makes it difficult for me to spin a higher 120rpm Lance Armstrong cadence so Im planning on a 100rpm. According to my calculations, In the 54/11 gears a cadence of 100rpm will yield over 35.7 miles per hour. If I run a 65t chain-ring with the 11t cog at a 100rpm cadence then I will be rolling at 43mph. This parameters will change as my skills and power output increases. I attached a few eye-candy photos. My low racer is the one with the dual 650C wheels. the other photos are the 200mm Cranks with Q-rings and a gold KMC X9SL hollow pin chain. :) For your viewing enjoyment here is a video of us riding around White Rock Lake in Dallas http://video.google.com/videoplay?docid=-913188020251904140&pr=goog-sl It was shot with a helment cam, I had to mute my speakers due to Gregs poor choice in background music. :)
05-29-07, 05:49 PM
Why not do a triple up front with a sram 3x7 or 3x8 in the rear give you even more of a range than a quad set up would.
05-29-07, 06:53 PM
That sounds awesome. Sorry, I did botch my earlier back-o-the-envelope calculations, 43 mph isn't that crazy. Think I did my m/s to mph conversion backwards. Ah well.
Have fun with your quad! Nice rig you have there, too.
Sheldon Brown has done all kinds of setups with an internally geared rear hub added to standard derailleur systems. Check out the 63 speed @ http://sheldonbrown.org/bicycle.html#otb
05-30-07, 04:14 AM
Thanks for the suggestion, I like the internally-geared hubs and
cranks. I want to build an Electric-Bike with one next winter. They
can shift while standing still. BUT they are reported to have a 10%
power loss. Not good in a performance situation.
05-30-07, 08:32 PM
DaVinci Tandems have an unusual setup using two cassettes/freehubs that allow independent pedaling by each rider. The gear combinations are basically set up as a 4x8 so you get the equivalent of 4 chainrings and they claim a gear range of 18 to 140 gear inches. That should cover most needs.
Details at: http://www.davincitandems.com/dv2.html
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