psycholist Posted March 8, 2008 Report Share Posted March 8, 2008 Have a look at this: http://en.wikipedia.org/wiki/Retro-DirectI'm seeing about converting a singlespeed bike I use for commuting to this system. The plan is to use an old DCD or a Tension Seeker or something similar to supply the idler gear - no significant chain tension is carried in the chain on the idler, so it doesn't need to be strong.The problem is getting a hub with enough threading to allow two freewheels to sit side by side. I'm considering threading the outside of a freehub body (Need to check the dimensions to confirm that this can be done 1.37 or 1.375" diameter by 24TPI seems to be the thread - there are ISO and English freewheels around and I've no idea what the difference is).Something like a Surly fixxer with extra threading would be a good plan, but I'd rather do this very cheaply and the Fixxer is silly money for what it is (Given how much a freehub sells for by comparison) .Anyone tried this? I plan to set the bike up with the forward gear as the high cruising gear, while the backwards gear is for grinding up the hills - it'll wreck people's heads watching the gear change . Quote Link to comment Share on other sites More sharing options...
NVWOCI WVS Posted March 8, 2008 Report Share Posted March 8, 2008 That won't work? the chain will be travelling the same rate around two different diameter chainrings so it will be travelling at two different speeds! Quote Link to comment Share on other sites More sharing options...
Revolver Posted March 8, 2008 Report Share Posted March 8, 2008 get a rohloff or a nc17 stinger and use two chainrings Quote Link to comment Share on other sites More sharing options...
Mike Poyzer @ Onza Posted March 8, 2008 Report Share Posted March 8, 2008 This does work. It is a very old but tried and tested system. We made one many years ago and you need a special extra long threaded hub and through screwing freewheels like the Dicta style.You cannot use a cassette hub with two sprockets on, because both freewheels need independent ratchets. We have also designed but not yet made a two speed unicycle using the same system. It is best to use the backward pedaling gear as your low gear to get going and then into your forward pedaling high gear once you are moving. You are definitely going to need some engineering facilities because I do not think you can do it with standard components. Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted March 8, 2008 Report Share Posted March 8, 2008 won't the chain line be all like...well...not a line anymore?! Quote Link to comment Share on other sites More sharing options...
Fish-Finger-er Posted March 8, 2008 Report Share Posted March 8, 2008 That won't work? the chain will be travelling the same rate around two different diameter chainrings so it will be travelling at two different speeds!theres only one chain, travelling at one speed, but its around 2 different sized sprockets, going in different directions around each sprocket, so one is in effect constantly freewheeling when pedalling forwards, and the other constantly freewheeling when pedalling backwards. Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted March 8, 2008 Report Share Posted March 8, 2008 http://users.skynet.be/ppc/retrodirect_drive/videos....! Quote Link to comment Share on other sites More sharing options...
Christophe' Posted March 8, 2008 Report Share Posted March 8, 2008 thats amazing.er ,can you actualy freewheel? Quote Link to comment Share on other sites More sharing options...
Mike Poyzer @ Onza Posted March 9, 2008 Report Share Posted March 9, 2008 Yes, it freewheels normally. You just can't pedal backwards and freewheel as in a normal cycle. Quote Link to comment Share on other sites More sharing options...
PaRtZ Posted March 9, 2008 Report Share Posted March 9, 2008 That is really amazing. Awesome idea Quote Link to comment Share on other sites More sharing options...
Fish-Finger-er Posted March 9, 2008 Report Share Posted March 9, 2008 Yes, it freewheels normally. You just can't pedal backwards and freewheel as in a normal cycle.Yea, the pedalling backwards thing isnt really an issue, if youve got it as your low gear, as youll normally be going faster than needed to drive it. so youll still backpedal normally.only issue is when your stopped though, as at that point it basically becomes a fixie that goes forward both ways.if that makes any sense. Quote Link to comment Share on other sites More sharing options...
trialmil Posted March 9, 2008 Report Share Posted March 9, 2008 That won't work? the chain will be travelling the same rate around two different diameter chainrings so it will be travelling at two different speeds!Analize the drawing again... I think that's brilliant, but maybe not to be used in BikeTrials Quote Link to comment Share on other sites More sharing options...
2sixstreet Posted March 9, 2008 Report Share Posted March 9, 2008 My only question is WHY? I appreciate the engineering but I cant see any advantage over a system with a derailleur. One of the articles mentions its good if you want a single speed setup. Last time I checked, 2 gears isn't a single speed. Yeah it would look cool to passers by but imagine what weirdos are actually going to stop and ask questions. We attract enough imbeciles when riding trials! Quote Link to comment Share on other sites More sharing options...
psycholist Posted March 10, 2008 Author Report Share Posted March 10, 2008 The idea with the freehub was to cut threads for two freewheels into the freehub body and have three freewheels (Crappy pick up) but much better durability in the back hub - Axles tend to fail all the time when used with screw on multi sprocket hubs because there's too much unsupported axle at the drive side. Another interesting feature of the drivetrain is that the bike can't be rolled backwards, handy when locking it leaning against things. The idler wheel will allow the chain to be tensioned as it wears without having to move the wheel forwards and backwards as in the singlespeed I'm thinking of modifying for this. I'm definitely not building this as a trials bike - it will remain my commuter... Quote Link to comment Share on other sites More sharing options...
Ben Cox Posted March 10, 2008 Report Share Posted March 10, 2008 sod that lol, who here ups to a wall or something then cocks the pedals back for a gap??? insta death lol Quote Link to comment Share on other sites More sharing options...
DrDoom Posted July 19, 2008 Report Share Posted July 19, 2008 http://jforjustice.co.uk/banksters Quote Link to comment Share on other sites More sharing options...
grant_hundley Posted July 19, 2008 Report Share Posted July 19, 2008 he hasnt said he wants to use it for trials.... Quote Link to comment Share on other sites More sharing options...
ogre Posted July 19, 2008 Report Share Posted July 19, 2008 What happens if you want to do pedal hops where you need to keep the brake on during your air, and ratchet backward? Or how do you ratchet your pedals back to put your choco foot forwards?IMO i don't think this is a good idea!why the hell did you bump this thread? Quote Link to comment Share on other sites More sharing options...
spode@thinkbikes Posted July 20, 2008 Report Share Posted July 20, 2008 These are good fun to ride actually. Uses different muscles too Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 20, 2008 Author Report Share Posted July 20, 2008 Only potential problem long term is that if you sped a lot of time in the back pedaling gear the pedals/BB will unscrew... Quote Link to comment Share on other sites More sharing options...
ben_travis Posted July 21, 2008 Report Share Posted July 21, 2008 i think this might be the stupidest idea ever.what a god awful contraption Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 21, 2008 Author Report Share Posted July 21, 2008 For trials, unquestionably it's totally useless, for my commute to work which is downhill in the morning, uphill in the evening and crosses a few busy roads where quick acceleration is a must for crossing, it may be very useful indeed - still haven't put one together though - looking for a screw on hub with lots of thread as I don't trust the setup with one freewheel screwed half onto the hub with the other half screwed onto a steel BB cup already holding the second freewheel to last (Not to mind the rear axle strength issue - the compelling reason why geared bikes went to freehub style hubs). It's why I'd love to see freewheels that fit shimano freehub splines (It'd be very useful as a fitting standard for trials cranks and rear hubs too - much less chance of a nasty accident trying to remove them for one)... Quote Link to comment Share on other sites More sharing options...
ben_travis Posted July 21, 2008 Report Share Posted July 21, 2008 with all the difficulties / cost this is causing...surely it would be more appropriate to just purchase a standard modern gear system.or if you really wanted, keep it fixie / freewheel on the back, and just find a cheap crank set with multiple cogs on, and a mech.this system is seriously just a silly one!? wouldnt you agree!? Quote Link to comment Share on other sites More sharing options...
RobinJI Posted July 21, 2008 Report Share Posted July 21, 2008 (edited) Would the easy'st method not be to use a flip flop hub, 2 right hand crank arms and 2 separate chains, one run normally, and one crossed on its journey from the cranks to the freewheel?Edit: (obviously with a left hand drive BMX freewheel on the left chain.)Or slightly less simple but still possible you could even run a front freewheel with a large fixed screw on sprocket sandwiched behind it and one behind the rear sprocket? Edited July 21, 2008 by RobinJI Quote Link to comment Share on other sites More sharing options...
psycholist Posted July 21, 2008 Author Report Share Posted July 21, 2008 Running 2 RH crank arms means you're guaranteed to have one pedal come loose whichever way you prefer to pedal - setting the high gear, the one you're likely to use the most as the pedaling forward gear keeps the pedals on. Crossing over a chain where both ends are run to the same sprocket leads to the two lengths of chain meeting in the middle and a pretty unpleasant crunching noise as well as issues with keeping the chain on. Tensioning two chains using horizontal dropouts would also be a problem. This is more an investigation to see if it can be done on standard bikes with existing parts than the pursuit of an improvement over existing designs. The bike I'm thinking of modifying is currently ghetto singlespeed (Rearranged cassette on a freehub with a big sprocket each side of the sprocket I'm using to keep the chain on even while slack to avoid having to retension the chain all the time). It's a 48:15 gear though, so a tad high for pulling away quickly, but ideal for cruising... In terms of cost it would cost be two cheap freewheels (I have a screw on hub around the garage somewhere and a steel BB cup might cost me up to 2 or 3 Euro) and require as little maintenance as the current setup - possibly less if I use a DCD (Also around my garage somewhere) as a chain tensioner and move that along the chainstay to tension the chain rather than having to move the back wheel and readjust the brakes each time... Quote Link to comment Share on other sites More sharing options...
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