-6

I was wondering if they make a 2 speed bike with a design having 2 front sprockets (one on each side of the bottom bracket) and 2 rear sprockets such that there is some mechanism that can switch between them. It would be a nice bike for a casual rider that lives in a flat area. They could use for example a 1.5:1 (42/28) lower gear for starting off, headwind... and a 2.5:1 (40/16) higher gear for higher speed, tailwind... I like the idea of sprockets on both sides since they can be customized to the riders needs and they are always perfectly aligned and don't require an inefficient internal hub and if a chain breaks, they can just use the other remaining gear. Also for people that like symmetry this would look cool with 2 front and 2 rear sprockets. The 2 teeth difference in the front would be hard to notice or they can have 2 identical sized chainrings in front.

Edit in comment from below: I am not a Mechanical Engineer so my drawing skills would not be good enough so I choose to use words instead. I just have some "out of the box" ideas I like to throw out to inquire. If such a 2 speed bike existed I would likely get one for playing around with. Mechanically it seems it could work and like any other design, it has advantages and disadvantages. For a training bike it might even be better than a 1 speed since 2 very close ratios can be used to assist with fatigue, uphill...

David
  • 818
  • 1
  • 7
  • 23
  • 4
    You make be interested in http://sheldonbrown.com/bichain-fixed-free.html – mattnz Feb 02 '16 at 02:13
  • 1
    As a practical matter you get most of the same advantages from a bike with a regular multi-speed hub, so there's no (selling) point in making one. But you can certainly make one for yourself if you wish. – Daniel R Hicks Feb 02 '16 at 03:34
  • 1
    @mattnz - Particularly observe the warning about losing fingers. – Daniel R Hicks Feb 02 '16 at 03:34
  • I figure 1 speed bikes are liked for their simplicity so why not extend that and make a 2 speed with some clutch mechanism in the bottom bracket perhaps that determines which side will freewheel. Advantage here is the person can choose and 2 gear ratios whereas an internal hub has limitations and is not as efficient as far as power transfer. Someone could dress up their bike with 2 different color front chainrings for example. Also perhaps there would be a 2nd version of this design for especially strong riders. It would engage both sides and they could run identical gearing for load sharing. – David Feb 02 '16 at 07:26
  • 7
    I'm voting to close this question as off-topic because it's not a practical problem that the asker is actually having, he has no intention of doing anything with the answers, and these sort of abstract, theoretical questions detract from the "practical answers to actual problems" nature of the site. – Móż Feb 02 '16 at 08:05
  • 2
    @Mσᶎ I agree this should be closed based on user history of abstract proposals. But a question of a gold bike was not closed - this is more practical than that http://bicycles.stackexchange.com/questions/23632/could-you-make-a-bike-frame-out-of-24kt-gold/23660#23660 – paparazzo Feb 02 '16 at 08:16
  • Also duplicate of http://bicycles.stackexchange.com/questions/36671/left-side-isolated-granny-gear-right-side-all-other-gears-possible-and-practic – paparazzo Feb 02 '16 at 08:18
  • It is not a duplicate cuz I didn't mention any granny gear here but I did mention close ratio perhaps for training. No intention of doing anything with the answers? How could you possibly know that? I said if someone made this bike I would want one so that is a hint I am looking for someone with machine shop skills that I can team up with to tinker. Some bad assumptions and accusations going on here. – David Feb 02 '16 at 08:30
  • @David Really not a granny makes it different. You have a strange sense of logic and semantics. And I have votes. – paparazzo Feb 02 '16 at 08:44
  • How is a 2 speed bike "bizarre" when they are already on the market. Some of the "logic" here is questionable! This site has too many stupid rules. It is not very useful to me. – David Feb 02 '16 at 15:52
  • @david - I think you're used to SE stacks that are more theoretical and "what-if" oriented. Bicycles are practical - you get on them and ride. As such, questions and answers here are far more practical and hands-on. What actually works/doesn't instead of "could I do this?" Enough talking, start doing. – Criggie Feb 02 '16 at 23:46
  • 2
    @david and I'm amused that you've stated a 2 speed bike "might even be better than a 1 speed since 2 very close ratios can be used to assist with fatigue, uphill" You've just reinvented the multi-geared bike. – Criggie Feb 02 '16 at 23:48
  • 2
    @Criggie You are only encouraging by answering the question.. – paparazzo Feb 03 '16 at 03:11
  • I can't answer the question anymore because it is closed, but the system exists (using one chain): Surly Dingle Cog. I can't find it on the Surly site anymore, but here is a blog post about it: https://bikecarson.com/2012/03/12/surly-dingle-speed/ – StefanS May 15 '19 at 14:26

2 Answers2

4

I have never seen such a design. As others have mentioned, the described design would be difficult to make work as you would need to switch the gears and if you didn't want it fixed you'd need a freewheel that engages backwards.

However, you may be interested in the retro-direct (https://en.wikipedia.org/wiki/Retro-direct). The retro-direct has two different-sized freewheel sprockets on the same-side of the bike and the chain is wrapped around them and the single front chainring such that pedaling forward moves forward in one gear, pedaling backward moves forward in the other gear, and not pedaling allows you to coast. You cannot, however, roll the bicycle backwards with this setup.

itfuwub
  • 374
  • 1
  • 6
  • It doesn't seem to me to be difficult to get to work. I think you would need 3 freewheels and a lock for the high gear. That is, the low gear would always try to deliver power to the rear wheel. When the high gear is in lockout the low gear will function normally. When the high gear is allowed to deliver power, since it is a higher gear, it will force the rider to pedal too slowly to engage the pawls on the lower gear. The 3rd freewheel in the back is so the chain can be held steady but a moving chain design can also work but there is no need for that. – David Feb 03 '16 at 04:17
3

Answer: No.

But you could make design and make one. You'd have to have some creative way to safely disengage one of the chains, and let the higher gear click away on its freewheel.

Try sketching up a drawing and posting it for feedback. Not just a description in words, an initial diagram.

Criggie
  • 124,066
  • 14
  • 180
  • 423
  • I am not a Mechanical Engineer so my drawing skills would not be good enough so I choose to use words instead. I just have some "out of the box" ideas I like to throw out to inquire. If such a 2 speed bike existed I would likely get one for playing around with. Mechanically it seems it could work and like any other design, it has advantages and disadvantages. For a training bike it might even be better than a 1 speed since 2 very close ratios can be used to assist with fatigue, uphill... – David Feb 02 '16 at 07:39
  • @david - fair enough. Sometimes an idea communicates better with a sketch. I do like your idea of two, to give increased options.....a downhill and a flat/uphill/headwind gear. Would be nice if there was an "uphill" gear as well. – Criggie Feb 02 '16 at 08:02
  • 2 is the next step in simplicity next to 1. If you go to 3 you get more gears but lose some simplicity. My idea of quad sprocket 2 speed bike is a compromise between those but with some added features such as a backup drivetrain. You wont have to worry if you break a chain cuz you have 2. Question is will this idea work and what problems might creep up. I think it is a good concept bike with 2 gears that doesn't require any shifting and no derailleurs, just 2 (maybe 3) freewheels and a special device to select which gear, either high or low. The 2 gears can be anything the rider wants. – David Feb 02 '16 at 16:00
  • @david That is how the multi-geared bike progressed from a single-speed bike. One year the TDF riders threatened a sit-down strike in the race so the UCI would allow them use of multiple gears. Too few gears is sub-optimal, too many gears is pointless. Find the happy medium and ride it. – Criggie Feb 02 '16 at 23:51