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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 08-24-05, 09:33 PM   #1
honduraz10
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double freewheel double drive fixed

alright, heres my crazy bike idea that ive been pondering for a while: i wanna get track wheel with a freewheel on each side and set it up double drive, with an easy gear on the left and a hard gear on the right. that way, you could pedal forward on a really high gearing and skid on a super low easy gearing, because the right side freewheel would engage when pedaling forward and the left side freewheel would engage when pedaling backward.. plus it'd look sweet. would it work?
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Old 08-24-05, 10:12 PM   #2
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there is a bike like that on fgg
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Old 08-24-05, 10:26 PM   #3
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you so cray-zy
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Old 08-24-05, 11:13 PM   #4
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It might actually work... only way to find out is to do it.
Problems you may encounter: finding a BB spindle that will work and give proper chainline on both sides (at least on the first try). Finding a pedal to use on the left side, where you will be running a left crank (unless you use a tandem crankset). Of course, this could be solved by using a clipless pedal such as the eggbeater (but i suppose you would need 2 pairs), or by using flat pedals where you could attach a clip and strap to the "wrong" sides, or by using whatever pedal you want for clips and straps and rebuild the left with the spindle from a right pedal.
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Old 08-24-05, 11:17 PM   #5
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I think the dude on fgg used a tandem crankset.
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Old 08-24-05, 11:33 PM   #6
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Isn't that what Sheldon just used for his insanity? Tandem cranksets seem to be the way to go for reverse side drive trains...

I have no idea why though... Maybe I should look into tandems, but I almost always ride solo, so other than the reverse drive train, it seems... frivolous.
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Old 08-25-05, 12:12 AM   #7
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that won't work - it'd only work if the "reverse" gear was a higher gear ratio than the "forward" gear. Otherwise, it would bind up.

Think about it: if your reverse side is half the gear ratio of your front, and you're going 10mph, pedaling at 40 rpm (cuz thats the gearing you have on the forward side) the the "reverse" side is going to forcing the left side crank to pedal at 80rpm. No workie.
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Old 08-25-05, 02:48 AM   #8
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Quote:
Originally Posted by HereNT
Isn't that what Sheldon just used for his insanity? Tandem cranksets seem to be the way to go for reverse side drive trains...
Not at all. If you just want left side drive and have eggbeaters (fixie with track hub, of course), you just whip out the crank puller and change the cranks. It will work.

Here, the trouble is that he wants a chainring on the left and right side, so either a tandem crankset or two right side pedals are needed.



The idea is great, but it wouldn't work with different gear ratios on the two sides. I you put a bigger tooth count freewheel on the left side, it will try to force the left crank turn faster than the right, as it moves more chain per wheel rotation than the smaller, right side freewheel. The very same bike could be ridden backwards without a problem, though. Then the right side would be freewheeling, spinning faster than the left, driving sprocket.

(Am I right about this??? It's really confusing)

Edit: same as the previous poster said.

Edit2: Don't build a bike with a higher ratio on the left side, either. It would go forward without a problem, clicking but something disastrous would happen if you tried to backpedal... Though I have no idea what. Chain breaks? Or am I wrong about it all?

The bike on FGG must have been one with the same ratio on both sides... which begs sombody (Sheldon, do you hear me?) to build a bike with two freewheels that has different sized cogs and rings. For example 16/48 and 18/54. It would look completely alien.
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Old 08-25-05, 07:19 AM   #9
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Quote:
Originally Posted by LóFarkas
The idea is great, but it wouldn't work with different gear ratios on the two sides. I you put a bigger tooth count freewheel on the left side, it will try to force the left crank turn faster than the right, as it moves more chain per wheel rotation than the smaller, right side freewheel. The very same bike could be ridden backwards without a problem, though. Then the right side would be freewheeling, spinning faster than the left, driving sprocket.
.
Surely when you go forwards the left hand freewheel would be free wheeling and the right hand side would be driven, when you skid or pedal backwards the rh freewheel would be free wheeling and the lh one would driven "backwards". So it could work.

The difficulty could be that unless you are lucky with rations you would need a tensioner on one side (although that shouldn't matter since that side wouldn't be fixed gear). You could even put a multi speed cluster plus derailleur on the rh side and a single speed freewheel on the other. Then you would have a multi speed "fixed gear".

The other difficulty is that the thing is gonna sound like an angry swarm of bees since it will be freewheeling all the time.
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Old 08-25-05, 07:26 AM   #10
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The problem is this: the rear wheel is rolling. As we all know, a traditional freewheel, when the wheel rolls backwards, will engage the pawls and rotate the cranks backwards.

If you pedal the cranks backwards faster than the freewheel takes up the chain, then you continue to freewheel.

However, if you use mismatched freewheels for different gear ratios, one of them will effectively cause the other to be rotating backwards faster than the chain allows and will bind up the drivetrain as it tries to pull the cranks along with it.
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Old 08-25-05, 10:31 AM   #11
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you could use a southpaw on the left side and a regular freewheel, using the same ratio of course,
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Old 08-25-05, 10:41 AM   #12
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Quote:
Originally Posted by Momentum
Surely when you go forwards the left hand freewheel would be free wheeling and the right hand side would be driven, when you skid or pedal backwards the rh freewheel would be free wheeling and the lh one would driven "backwards". So it could work.
Not at all. I know it's confusing, but bear with me, or try it out if you have a freewheel lying around like I do.

Suppose you put same size chainrings on both sides, a 16T freewheel on the right, and a 20T on the left side. When you pedal forwad, crank turns right freewheel turns wheel. Simultaneously, the left crank's chainwheel is turning, trying to feed exactly the same amount of chain through the freewheel as the right side one. As this cog is larger, it will be forced to turn slower than the right side one. While both chains travel 80 links, the right freewheel will have to turn 5 rotations, the left side one 4 rotations.
Now, given the structure of the freewheel, when it's mounted on the left side, it can turn forwards as fast as the wheel, or faster, but not slower. When the wheel is stationary, the left-side-mounted freewheel can turn freely forwards, but not backwards. (<--Backwards, it drives the wheel, obviously).
So, you couldn't go forward at all with this setup.


Conversely, if you put the larger freewheel on the right side, the left, smaller freewheel will be turning faster than the right side one when you go forwards, freewheeling away happily, and you can ride the damn thing. (This bike obviously couldn't be ridden backwards.) What I don't know for sure is what happens if you try to backpedal. Supposedly, you get a larger gear ratio (not much fun at all, BTW), with the right cog freewheeling... This, though impractical, should work, shouldn't it? Skidding definitely would be ok as long as you can skid the larger gear.



Now, what if you use a trials setup: fixed cogs, freewheels at the cranks? I'm lazy to think it over.

But...

Somebody, please build a frankenbike with two different-sized freewheels and cogs. Say, 44/16 and 55/20
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Old 08-25-05, 02:51 PM   #13
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Think about it this way: if you had the same ratios, it'd pretty much be a fixed gear. If you had a taller gear for the "reverse" you could keep the pedal rpm's between the two different gears and slow down the pedals to engage the "reverse" freewheel.

However, with this setup there will always be noise coming from one of the freewheels. Imagine always hearing a freewheel clicking, even when cruising along pedaling perfect circles......kinda interesting though.....
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Old 08-25-05, 07:48 PM   #14
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Quote:
Originally Posted by LóFarkas
Now, what if you use a trials setup: fixed cogs, freewheels at the cranks? I'm lazy to think it over.
i think it would work if you took my original idea but instead of having a standard crank on the left use your great idea of freewheeling crank, because as memory serves they dont engage when moving backwards. still with a freewheel on both sides, though you could have a fixed cog on the left side but i don wanna
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Old 08-25-05, 08:36 PM   #15
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my brain hurts.
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Old 08-26-05, 09:12 AM   #16
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wait... if you had a freewheel crank on the left side, wouldn't that cause at some point the cranks to get out of sequence, if that phrasing makes sense... i mean if you coasted on one side the cranks would no longer be 180 degrees apart... and you would feeling like you were spinning on wet noodles.... forgive me if if someone already addressed this... i'm doing all i can just to almost comprehend this thread
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Old 08-26-05, 09:58 AM   #17
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Freewheel cranks never get out of phase (not 180 degrees apart), the freewheel is attached to the spindle part. PowerCranks, however, can. And that adds a whole new dimension to the thread...

A PowerCrank with chainrings on each side, freewheels, on each side. What would happen? Explain your answer, and prove the contrapositive.
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Old 08-26-05, 11:44 AM   #18
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ive got a better idea... how about one drivetrain and a fixed gear! itd be perfect.. lighter, less to go wrong.. the same amount of drive...and you can carry your bike on the left side without getting grease on your shirt! its brilliant if i do say so myself.
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Old 08-26-05, 12:57 PM   #19
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but then you cant ride forward on a 90-11 gear ration and stop on a 20-20 gear ratio
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Old 08-26-05, 01:01 PM   #20
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i guess i fail to see the fun of that... youre talking about getting rid of what makes a fixed gear a fixed gear, in my mind. Don't try and complicate your simplicity.
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Old 08-26-05, 01:25 PM   #21
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your not stopping on a different gear because the cranks are part of the same shaft. If the 90-11 stops moving then the 20-20 also does. It would be the
(90-11 + 20-20) /2 ....I'm guessing, but it definatly would not be different for one side of the crank than the other.

[edit] I'm trying to think free wheel but keep thinking dual fixed. Maybe you are right but the momentum on the 90-11 is far greater than a momentum on the 20-20
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Old 08-26-05, 01:36 PM   #22
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The question is:
stopping at 20mph using 20-20 gearing any different from -
stopping at 20mph using 90-11 gearing?

I'm not into skidding so I would not have the experience but momentum is momentum and gearing doesn't matter. It is just when getting started that it make a difference.
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Old 08-26-05, 03:37 PM   #23
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yeah an easier gearing makes a big difference
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Old 08-26-05, 03:56 PM   #24
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Just build it. Even if you rig it up ghetto style, you'll be able to tell if it works. If it doesn't work, oh well, at least you tried something out. Stop the thinking and start the doing.
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Old 08-26-05, 04:13 PM   #25
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Quote:
Originally Posted by trackandtrials
…snip
Imagine always hearing a freewheel clicking, even when cruising along pedaling perfect circles......kinda interesting though.....
That's exactly what you hear with the old Sturmey-Archer 3-speed hub-gears† when in the higher gear. From what I remember, direct-drive is the 2nd gear of the 3 and when you're in the 3rd (high) gear, the planet-gear carrier is being driven by the input cog (the one the chain is on), the sun-gear is fixed (to the axle/frame), and the annular-gear (connected to the hub/wheel) is being driven at a higher angular rate than that of the input cog, and the clicking you're hearing is in fact the free-wheel…

(God, I haven't seen the inside of an SA hub since I took one apart about 40 years ago - all the above is from memory…)

- Wil

† hub-gears - such wonderful devices, beautiful, elegant, no external bits to break off - just make sure you add a few drops of sewing-machine-oil (3-in-1) to the little oiler cap (remember those?) regularly…
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