Seggybop

I got this idea, and remembered reading something vaguely similar. Nothing on search though.

Flip-flop hub, singlespeed freewheel on each side.
Chainring on both crank arms. Smaller chainring on left side.
Pedal forward and you go forward, left freewheel coasts.
Pedal backward and you slow down, right freewheel coasts.
Don't pedal and both freewheels coast (normal coasting).

Anyone tried this? Any info on it? Would it even work?

baxtefer

there's a schwinn on FGG like that

alcahueteria

I don't think both freewheels would cost if you didn't pedal, because if you roll a reguarl singlespeed backwards the pedals roll like a fixed, so by coasting you would esentially be rolling the left side freewheel "backwards" and thus it would catch and make you pedal. So it would just be some crazy ass fixed.

votedean

I think I concur.

Cynikal 

Wasn't there some discusion about the ability to use different gear ratios for forward and backpedaling? Did anyone try it?

MattP.

I remember seeing this about a month ago, so I dug it back up. Not sure if it is exactly like what you meant, but its almost the same concept.

https://www.bikeforums.net/showthread...ckward+forward

humancongereel

i agree about the coasting...that shouldn't work.

wouldn't the pedaling with different gear ratios just take some wack-ass adjustment on the part of the rider?

LóFarkas

Here is the thread that explains how it is impossible to get that to work usefully, with a smaller backwards gear.

The Schwinn on FGG has identical ratios on the two sides, so it's fixed. It has two never-coasting freewheels.

queerpunk

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

pedaling forward, R freewheel engages. pedaling backward or resisting, the L freewheel engages (reverstically), effectively being fixed.

i don't think it would be possible to have two different gear ratios. both are going around and around all the time at the same rate--b/c they're connected at the cranks--but they're each trying to turn the wheel a different amount each time.

nope.

nicomachus

My brain's hurting trying to think this one through. Especially the peculiarities of having a mix of different sized gears... I mean, if the backwards pedaling (left side) freewheel is a different size, then you got to be ready for a whole different pedal cadence.

Yeah, I'm not sure it would coast, unless you found some sweet spot for both freewheels. But is seems like if you pedaled backwards just a tad, then you're engaging the "fixed" feeling of the rear wheel.

Whoah... I gotta stop thinking about this and come back to it.

Cynikal 

In theory one freewheel is always spinning so the would be a constant clicking of a freewheel.

alcahueteria

I still don't understand why it wouldn't work with different gearings. Seems to me like when your pedaling forward the other freewheel is just spinning, so I don't see how chain slack or whatever would come into play. but whatever, I guess I'll read that other post again. I think the harder part would be finding a magic matching gear to keep tension and your wheel straight.

queerpunk

nope, not so sure about this. i think the inactive-drive-freewheel (L-side under Forward Pressure/R-side engaged) is static, but not freewheeling.

when something is freewheeling, it means that the cog (and therefore the chain) is static, but the wheel is going. However, on this dual-freewheel-dealie, both of the chains are always both moving.

no freewheeling, but as one side is engaged, the other is static--cog moving along with the wheel and freewheel body.

i think. it makes sense to me but i'm just trying to see it all in my head.

orange

yeah, queerpunk, you're right, the non-active freewheel would not be ratcheting since it's not rotating w/r/t the hub. (Even though it *is* rotating w/r/t the ground!) You might hear some clicks as you switch from pedaling forward to resisting, as the FGG post said, the pawls are not quite "in phase".

So, what would happen with two different size freewheels? Suppose the bigger gear (smaller fw) is on the drive side... as you pedal forward, the non-drive fw clicks, because the non-drive-side chain has to move faster, thus rotating the NDS FW w/r/t the hub. (Enough abbreviations??)

Now you switch to resisting. The NDS pawls lock up, and now the DS FW starts clicking, but not as fast as the NDS was clicking, because you're not fully coasting on that side--the higher gear is giving you some rotation of that cog w/r/t the hub.

At least, that's how I think it would work. Maybe someone else can correct me?

queerpunk

orange, what you said makes sense to me but i still don't think it can work. i'm awfully confused and wrote this:

"orange, it can not work with two different gear ratios! no matter the issue with freewheels or two chains or whatever, what we have is one wheel and one crankset. in order for these two things to move, two different drivetrains need to synch up. two different gear ratios would mean two different MPH's in a constant RPM. or two different RPM's in a constant speed. which can't happen when you can only have one RPM, one speed, when you have one wheel and one crankset in the system."

which makes sense to me. but i'm not sure about it, anymore, because i'm not sure how the freewheels will behave. more thinking about this on my lunch break.

trackandtrials

it's pretty simple - you can have matching gear ratios (virtual fixed, but will feel like a really slack chain due to freewheel engagement), or a taller (smaller fw) gear on the left side. Here's why:

If the rear wheel is going at a constant 120 rpm, and your forward drive gear ratio is 2:1, you've gotta pedal at 60 rpm to engage the right-side freewheel. If your reverse-drive (left side) ratio is 3:1, you have to slow your pedaling cadence to 40 rpm to engage it.

*That gives you a 20 rpm window in which you're not engaging either freewheel.*

As the two ratios get closer, that window get's smaller until you're virtually fixed. If you were to go beyond equal ratios, the freewheels would lock against each other and the wheel wouldn't move.

orange

track&trials, thank you!

note it would go backward OK. This illuminates what would happen if you tried to ride backward on a "normal" different-double-FW setup.

honduraz10

yeah i totally already suggested this and it got shot down. check it- https://www.bikeforums.net/singlespeed-fixed-gear/133215-double-freewheel-double-drive-fixed.html

asterisk

I work in the shop that put that bad boy together. It is real and worked. Look for more to come soon.

chzman

will this be NJS certified?