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Old 07-14-07, 12:11 PM   #1
bboysubhuman
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dual drivetrain?

Would any spindle allow for a dual drivetrain? I wanna put drive side cranks on both sides--I'm thinking BMX cranks since they have left side drive bikes. And then I would have a flip flop hub on the back with two freewheels which would make it a pseudo fixed gear. So could I just use a regular spindle and have really tight clearance on one side? I could try road cranks and put the chainring on the outside maybe.
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Old 07-14-07, 12:51 PM   #2
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sounds like a cool project, i have no positive input, but please post pics when your done!
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Old 07-14-07, 04:04 PM   #3
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Quote:
Originally Posted by bboysubhuman
Would any spindle allow for a dual drivetrain? I wanna put drive side cranks on both sides--I'm thinking BMX cranks since they have left side drive bikes. And then I would have a flip flop hub on the back with two freewheels which would make it a pseudo fixed gear. So could I just use a regular spindle and have really tight clearance on one side? I could try road cranks and put the chainring on the outside maybe.
I think people have done it before, even though I haven't been able to find any articles detailing it.
Also look into tandem parts, because on some they have two chainrings on one crank in the back.

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Old 07-14-07, 07:01 PM   #4
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That sounds really cool. Make sure you get a hub that allows for a lock ring on both sides.
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Old 07-14-07, 07:16 PM   #5
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well if I go with two freewheels, I won't need lockrings...I think.
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Old 07-15-07, 12:32 AM   #6
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If you went with 2 freewheels, you wouldn't really NEED lockrings...
but there might be a slack point because of the way a free wheel works. I think it would cooler with two fixed gear cogs and forget the freewheel al together. Maybe try and find a steel flip-flop hub and tack weld the cog onto the side that doesn't have the lock ring threads? Sorry, I don't know a real lot about flip-flop hubs. Good plan, it's going to take some expirimentation.
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Old 07-15-07, 07:28 AM   #7
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^^ Yeah, it would seem pointless to have the freewheels, just go for the cogs and lockrings.
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Old 07-15-07, 07:41 PM   #8
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At least you could coast using two freewheels though.

You can purchase a track wheel with fixed/fixed threading on a flip/flop hub. Try bicyclewheels.com if you want to keep the project super-budgeted.

To be honest, I was actually thinking about this the other day! I'm just going to heli-coil a drive-side road crank rather than use BMX cranks.
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Old 07-15-07, 08:01 PM   #9
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Originally Posted by hockeyteeth
At least you could coast using two freewheels though.

No you can't coast I never done it but that why the op said it's a pseudo fixed. If you take a freewheel bike (or any multi-gear cassette for that matter) and push the bike backward you'll see that wheel turn the pedal

Since the 2nd freewheel is on the left hand side. Think about when you flip a wheel. Rotate 180 on the vertical plane. Front become back and right become left. So the left handside freewheel think your going backward and will push the pedal forward.


EDIT: (More thought on fixed gear) The problem with fixed gear lock ring is flip flop hub on only have one side with a smaller inversed tread for lock ring.

So one side would have a proper fixed lock ring. The other side need to be suicide or freewheel

If it's a freewheel on the other side it does not do anything. It will not put any force going forward.

It can input force when your resisting the rotation but the fixed gear has no moving mechanism so I believe most if not all of the pedal rotation force will come from the fixed gear making the second freewheel completely useless.

With 2 freewheel the left hand side freewheel will push the pedal when going forward, when you resist motion, when you try to slow down or brake. The right hand side will provide forward motion when you pedal.

You create a pseudo fixed gear with an alternative system

I hope I haven't confuse everyone with my rambling

Last edited by DanPT; 07-15-07 at 08:13 PM.
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Old 07-15-07, 09:12 PM   #10
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There've been several threads in the ss/fg forum about dual and left side drive conversions addressing all these issues. Mostly they recommend using a fixed/fixed flip flop hub (in order to have lockrings on both sides) and tandem cranks/chainring.
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Old 07-15-07, 10:00 PM   #11
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I forgot that you can't coast backwards with a SS freewheel. I guess you could put a freecoaster on one the left, haha.
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Old 07-15-07, 11:22 PM   #12
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Here something I found browsing around

http://www.fixedgeargallery.com/2005...eBikeCo-op.htm

(Reference from this thread Dual freewheel system?)
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Old 07-16-07, 01:55 AM   #13
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If his drive side chain snaps, he can still skip.

edit: heavier and more complex than a brake.
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Old 07-16-07, 06:31 PM   #14
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Quote:
Originally Posted by DanPT
Here something I found browsing around

http://www.fixedgeargallery.com/2005...eBikeCo-op.htm

(Reference from this thread Dual freewheel system?)

Damn, that's exactly what I want to make. Thought I'd be the first. Oh well...it'll still be fun.
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Old 12-09-07, 12:09 PM   #15
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there was a bmx race bike with twin chains
seen chopper motorbikes with it to

yeah I would use Tandem cranks or even 2 normal cranks may have to threadlok the pedals in.
Maybe force apart 2 cheap steel hubs then press together the threaded hub ends have to get an engineering shop to do it in a hydraulic press. Then use a BMX left side sprocket if it fits on.....oh wait a minute......

That might not work...doh

Might machine an old alloy hub for threads on the left side. But getting that done will be difficult. Engineering shop again.

Some freewheels can be built the wrong way round but might unscrew them selves

The normal 34mm freewheels are the same thread form as English bottom brackets So it may be possible to use BB lock rings to hold them on.

Ive seen a bike with 2 speed drive pedal backwards for another gear....think it was on Sheldon brown.
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Old 12-10-07, 02:44 PM   #16
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Originally Posted by alecw35 View Post
there was a bmx race bike with twin chains
seen chopper motorbikes with it to
.
More info on the bmx cranks and hub. http://bmxmuseum.com/forums/viewtopic.php?pid=96795
http://www.bmxmuseum.com/forums/viewtopic.php?id=13453

Here is one that just sold http://tinyurl.com/2j47mn
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Old 12-12-07, 06:38 AM   #17
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Just get a fixed/fixed flipflop hub, a tandem crank and be done with it. All problems solved without redneck engineering. Not that I'm not a fan of redneck engineering, I just don't like to mickey-mouse my drivetrain too much.

EDIT: Chain-line might be an issue. Unless your hub is the exact width to space both rear cogs perfectly inline with the cranks, you could run into some issues. Once you start buggering the chainline, you run the risk of throwing the chain which can be a big deal with a fixed gear. You don't want to end up locking up the rear wheel at a high speed. It might be ok to have them a little off but I'd take the extra time to find a hub that matches the crank and both match the frame.

Last edited by Blais; 12-12-07 at 06:44 AM.
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