Singlespeed to TWOSpeed conversion

4kicks
4kicks Posts: 549
edited April 2008 in Road general
Is it possible to convert a single speed bike to a "twospeed" by having two chainrings, an FD and a chain tensioner at the back?

Ive got a nice singlespeed road frame, but find running a 44-16 round here a bit tough on the knees on some of the climbs, wheras I like the ratio for most situations. Im wondering if a chain tensioner can take up the slack associated with say a 36/38t inner ring...Guess the chain line would be "suboptimal" but dont see why this shoudl be more so than any normal geared bike..would it need to be a singlespeed with a ratchet hub, or could this also work for a fixie?

Any ideas?
Fitter....healthier....more productive.....

Comments

  • meagain
    meagain Posts: 2,331
    Hmmm! Can't see any reason in principle why a 2 speed freewheeler as you describe would not be possible. I've tried a couple of chain tensioners in the past but I really can't recall whether either would have had sufficient "spring" for your purpose. A rear mech locked via adjusters into one plane presumably would be fine. As you say, a compromise chain line should not be a problem (tho' might run a bit rough through either a mech or a tensioner?

    Fixed a different matter. Conventional (and I guess correct) wisdom is that NO tensioner strong enough to take reverse thrust!

    There IS a system whereby with a double fixed sprocket and carefully matched double up front can give two ratios with same chain length and hance axle placement. Manual operation however.

    Rivendell did a very nice 2 (possibly 4?) ratio "single speeder" a couple of years ago - can't recall its name. If you can find pics might throw up some ideas?
    d.j.
    "Cancel my subscription to the resurrection."
  • MrHulot
    MrHulot Posts: 173
    I don't reckon a tensioner would take up enough slack for you. Also to allow you to change the front clanger the chain would have to be too loose to use as a fixed. What you have described is just a geared bike when you change with the front mech in that the rear mech takes up the chain slack. So if you ran a singlespeed - with freewheel - and fit a rear mech adjusted and fixed to give a good chain line - no cable/gear change - then you could just select with the front mech as usual.
  • mrushton
    mrushton Posts: 5,182
    You need to go to www.paulcomp.com and then the single speed section and look at the Melvin which is a tensioner that will let you do this. I think. HOWEVER, Paul components are crafted bits of kit so poss. expensive.
    M.Rushton
  • meagain
    meagain Posts: 2,331
    so poss. expensive

    $75 stateside - don't think I've ever seen one for less than that in gbp here.
    d.j.
    "Cancel my subscription to the resurrection."
  • Pirahna
    Pirahna Posts: 1,315
    Get an old Sturmey 2 speed fixed hub.
  • bracestower
    bracestower Posts: 113
    Good luck with finding a Sturmey 2 or 3 speed fixed hub - those things rarely come up and go for £££.

    I agree that a conventional chain tensioner probably will not work.

    Not really sure what the point is though? Sounds like you're after a geared bike but don't want to admit it.
  • 4kicks
    4kicks Posts: 549
    Agree once you get to a full RD with stops it would be a "geared but dont want to admit it", but I just want something a bit less faff than I have with my 20 speed...willll look at the Paulcomp, thanks..
    Fitter....healthier....more productive.....
  • Hubstripping.com are selling NOS F&S Duomatic and Automatic 2-speed hubs for 100 Euro each - I haven't a clue what they're like but they look interesting.

    If you just want less faff than a 20 speed then there are other hub gears to consider - the general consensus seems to be that Sturmey-Archer make the best 3-speed hub, SRAM the best 5 or 7-speed plus Shimano Alfine/'red band' premium version Nexus for 8 speed hubs, though some of these options might be too expensive for you.
  • GaryGkn
    GaryGkn Posts: 1,199
    Have a look at the Quickbeam. I am sure that is the Rivendell bike with the attributes that you are after.

    http://www.63xc.com/george/qb.htm

    http://home.earthlink.net/~rivromulus/quickbeam.html
  • meagain
    meagain Posts: 2,331
    "the Quickbeam"

    That's the one! I enquired about buying one a few years ago: P&P price they quoted rather implied they didn't want to ship one!
    d.j.
    "Cancel my subscription to the resurrection."
  • GaryGkn
    GaryGkn Posts: 1,199
    Get Mercian to build you a better version they can angle the fork ends but I don't think they do cantis on there frames as a rule and you would want them.
  • meagain
    meagain Posts: 2,331
    Not as well off now as when I seriously contemplated the Quickbeam - a custom built Mercian way out of my spending power! And given likely economic climate that is fast approaching it's time to batten down the cash hatches I reckon!

    That's why there are four hundred quid bikes in the "shed" - doubt I can lose more than a twenty on each of them!
    d.j.
    "Cancel my subscription to the resurrection."
  • GaryGkn
    GaryGkn Posts: 1,199
    See what you mean the credit crunch may hit the bike world especially as most people will think £79 in a Halfords sale is the most they want to pay for a new bike with out the credit crunch.
  • meagain
    meagain Posts: 2,331
    Never mind the credit crunch (selfishly, it won't really impact on me), it's inflation (especially on non-discretionary spend) that is going to hurt those on (relatively) fixed incomes. It will almost certainly cost (sic) Labour (for want of a better term) the next election.
    d.j.
    "Cancel my subscription to the resurrection."