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Old 12-17-07, 07:03 PM   #1
stevegor
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Front derailiuer for R-20?

Ok gentlemen put on your bike mechanic thinking caps to answer this question for me.
As most will know, I have a 48t chainring on the Wasp and an 8 spd SA hub, but I would like another ring as well , say a 42t or 44t for climbing mountains and keeping the 48t for fast road riding. Now I could manually change it over for the ascents then change back for the descents, but I was wondering if I could try a front derailiuer, and would I need a chain tensioner or rear derailieur to keep things running smoothly?
I checked the height of the 48t ring and there seems to be room on the frame to make it work, does anyone know of a clamp-on deR..... that will fit R-20 tubing?

I humbly wait for your knowledgeable replies in hopeful anticipation


PS: Jur mentioned that he has 2 chainrings on SWMBO's Yeah bike, I wonder if he has found a solution for that?
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Old 12-17-07, 09:37 PM   #2
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Can a braze on part like this solve the problem?

http://aebike.com/page.cfm?PageID=30...ils&sku=FS1053
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Old 12-17-07, 09:50 PM   #3
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Hi,

I'll try and take a look at my Twenty tommorrow, 'cause I currently have a front derailler on it. It's a standard derrailler clamp. It technically measures slightly smaller than the Twenty's seat tube diameter, but it fits and works perfectly well,

Juan
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Old 12-18-07, 11:02 AM   #4
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Originally Posted by stevegor View Post
Ok gentlemen put on your bike mechanic thinking caps to answer this question for me.
As most will know, I have a 48t chainring on the Wasp and an 8 spd SA hub, but I would like another ring as well , say a 42t or 44t for climbing mountains and keeping the 48t for fast road riding. Now I could manually change it over for the ascents then change back for the descents, but I was wondering if I could try a front derailiuer, and would I need a chain tensioner or rear derailieur to keep things running smoothly?
I checked the height of the 48t ring and there seems to be room on the frame to make it work, does anyone know of a clamp-on deR..... that will fit R-20 tubing?

I humbly wait for your knowledgeable replies in hopeful anticipation


PS: Jur mentioned that he has 2 chainrings on SWMBO's Yeah bike, I wonder if he has found a solution for that?
Check this link. http://home.comcast.net/~cheg01/r20.html Lots of Twenty modifications there including mounting a front mech.

Jim
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Old 12-18-07, 01:56 PM   #5
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The size of the seat tube on a R20 frame is 31.8mm
Standard size is 28.6mm which happens to be the seat post diameter of the R20

A lot of modern front mechs come in a bigger size, 34mm or 31.8mm. They have plastic and steel shims that clip inside the deraileur clamp. These allow it to mount on the different diameter seat tubes.

Some mechs are rated to fit the specific chainring size. Might be marked 42 tooth. I geuss you can mount these higher. So the end of the cage doesnt hit the chain ring. If front mechs are mounted too high. Its difficult to change gear.

Raleigh used simmilar frame design on the Chopper. There was a 10 speed version of that, in the 70s
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Old 12-18-07, 02:15 PM   #6
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I think that the cable routing would be an issue here.
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Old 12-21-07, 09:29 AM   #7
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All I can add is to say you'd definitely need a rear derailleur or tensioner as the chain would be slack when on the small chainring. With that in mind it'd probably be a more elegant idea to lose the planetary hub and go for full rear derailleur as the chainline will be an issue going from front derailleur to fixed-position rear sprocket and may be droppy. Also - a tensioner will add weight so might as well keep it all to one system.

From what I've read about other twentys with rear cassettes, it's hard to get clearance for the smallest sprocket though and you may have to forfeit the highest speedy gear, though my hunch is with the right parts, a dished wheel and the optimum spacing along the axle and this may be preventable.

Third thought if you like routing cables is to pick up a SRAM dual drive - hub and derailleur and front double = 2.43 trillion usable gears.
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Old 12-22-07, 10:42 AM   #8
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I understand that there is a chain tensioner available that will bolt under one of the rear wheel axle bolts that may work here. I found this out when I was enquiring about adding a 2nd ring to the front of my own R20.

However, I have since decided that I will be getting the wide range version of the Schlumpf drive instead. By doing so, I will keep within my own guidelines of not having to have a rear deraileur\tensioner hanging down, and will also keep to a single ring up front. However, I understand that the Schlumpf will accept a 2nd ring which, as I see it, may be somewhat similar to having 4 front rings.
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Old 12-22-07, 02:30 PM   #9
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I'd have to sell my wife and children...and maybe my dog to afford a Schlumph
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Old 12-23-07, 12:00 AM   #10
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Dont forget you'll also have to sell your left NUT Too! that thing is a bit on the exspensive side! That which we fancy, we must make sacrafices ... Sucks to be poor...


Check out the site, and see what's new...
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Old 12-23-07, 02:37 AM   #11
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But I need that to hold the wheel on....????
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Old 12-23-07, 02:54 AM   #12
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HA! Wrong nut, but still important!

Phatatude - "It's fast, and it folds... Watch out ladies "

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Old 12-23-07, 11:20 AM   #13
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They'll forgive you.

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Originally Posted by stevegor View Post
I'd have to sell my wife and children...and maybe my dog to afford a Schlumph
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Old 12-23-07, 02:33 PM   #14
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They'll forgive you.

Hmm, if that's true...I'll go on eBay and order a Rohloff speed hub with disc brake, a Schlumpf mountain or speed drive, c/f seat post, bars, bidon cages, cranks, rims, front disc hub, spokes..and...and, no wait ...if I did that, I'd really be walking lopsided, hey Phatatude??
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