component idea: clutched freecrank
 

Not really clutched I guess, more bearing-latch.

Think about the crank connecting to a rotating bearing connected to the chain rings. The crank also connects directly to the chain rings, but through a springed locking mechanism on alignment. If it is unaligned, it doesn't lock; rotate it and it will latch into place when aligned.

So, overall, when unaligned, the crank arms and chainrings spin independantly. Upon alignment, the crank latches to the chainrings, so pedaling will turn them. You put a brake lever on the left handlebar (as the clutch is on a motorcycle), and when the rider grabs it he unlocks the crank so it freespins.

Thoughts?

1) Is there any benefit at all to this?
2) Is it a benefit that Shimano didn't cover decades ago with their front freewheeling system?

What's a front freewheel?

There is a use in any system where other things make the crank turn when the rider wants to coast, like a fixed gear where the rider wants to be able to pedal backwards but wants to take a sharp turn without heelstrike, or a tandem out of phase where the stoker wants to not heelstrike... basically anything that involves the crank doing funny things when you want it not to, but can't fix it without doing funny things elsewhere.

Obviously no normal mortal needs this.

http://lmgtfy.com/?q=Shimano+front+freewheel

Being creative and thinking is never a bad thing, and I'll paraphrase Sheldon, like Shimano's front freewheel this is a solution looking for a problem.

This does sound like the front freewheel system. It also sounds heavy, complicated and redundant. I guess I wonder "Why"?

If I read the OP's later comments correctly, his idea is very different from front freewheel. It seems he want's the ability to engage/disengage/ a fixed gear arrangement at will.

A basic overrunning clutch such as Shimano's old front freewheel system won't do the trick, and as others point out has no advantage over a rear freewheel.

But it's an interesting idea for fixed gear riders.

I have a vintage Sturmey Archer 2-speed fixed hub that I've arranged to do exactly what the OP desires. Using a 3-speed control, I have it set up with normal and low using the 1st & 3rd gear positions and have a dead spot or neutral in 2nd. It's nice for long descents, and I've used the feature in emergencies where cars have squeezed me to the curb and I couldn't have the right pedal come around to 6 o'clock.

To the OP, from a technical standpoint you're approaching this the hard way. You'd be better off putting your clutch into the rear hub, where for example you could route the control cable without dealing with clearing the rotating cranks.

Except fair warning. There's a rumor SA Taiwan is bringing back the TF hub, or maybe a 3s fixed, which would probably eliminate the need for your device. (maybe it's happened already, I don't follow all new items)

FBinNY,

On the Classic & Vintage board there's a picture of a shifter, or link to it on Ebay, posted that had something like Normal-Neutral-High, or Low-Neutral-High.


Bob

the 3 speed fixed hub is out on the market now.

A neutral gear would be slow, requiring shifting. It would solve slow problems like fixed gear coasting, but what about fast problems like heel strike in a sudden sharp maneuver? You're slightly above bdc on that pedal, if you pedal forward you strike, don't and you strike, backwards and you brake.

Plus, how would this solve other odd problems at all, like out of phase tandems where the captain is horizontal and the stoker is vertical, such that the stoker heel strikes in a turn? Or if the stoker wants to coast and the captain doesn't... but eh, less important. The advantages to OOP tandeming come with costs, although nothing says you can't use dual stops to do 90 OOP and IP with a lever to switch...

Indeed. I've had one for quite some time.

The purpose of my prior post was to clarify the difference berween the rider controlled clutch you were proposing and the front freewheel (overrunning clutch in the cranks) of prior years.

I wasn't suggesting that the 2 and 3 speed fixed hubs would address all your scenarios, but simply that it'd easier to engineer a clutch into the hub vs. the crank. You could easily have a brake lever as the actuator and the rest of the engineering would be very simple.

Building a cable activated clutch into the crank poses more challenges, the first of which being how to route the control cable. It's not insurmountable, just more complicated. If variable tandem phasing is desired, that's easily solvable with a overrunning clutch in either crankset, allowing for example the stoker to pause then start pedaling at any point in the cycle.

Schlumpf 2 speed planetary geared cranksets have a toothed clutch between the
right arm and the gears in the spider,
so when engaged the crank rotates at a different rate than the chainring
The Swiss Machine Shop makes 2 over drive and 1 reduction gear set in these cranks..

[I have one on my folding bike ]

Davinci Tandems already makes an independent coasting system for bikes. http://www.teamspirit.net/dv2.html
On a 90* oop tandem you can still make both cranks point up. The worst is 180*oop, and then you can still get them both horizontal, which clears just fine on a turn.
If you don't have time to hit a lever to throw your hub in to neutral, how are you supposed to have time to throw your crank in to neutral?

I think you confused us when you called it a "freecrank". More accurately you're talking about simply a clutched crank. "Freecrank" implies the forward freewheel such as the old Shimano setup.

YOu're also talking about aligning the setup in some way. Keep in mind that many clutching system designs that have to align to engage involve mechanical load to disengage as well. And if this is to be used as an emergency disengagement device you'll want to ensure that it is easy and fast to use even to the point that if a pedal strike is in the process of occuring and has loaded the system that the clutch would still disengage easily.

Another aspect is the acceptance of the product within the intended market. I can see this being something that the tandem crowd would like for your reasons stated. But I can also see the problem with the tandems being easily cured with a freewheel at the stoker's or captain's bottom bracket. But that would mean that the stoker and captain would spend a lot of the time out of synch. But is such a thing really an issue on a tandem? I don't ride one but it seems to me that heeling over into a turn where an out of synch heel strike could occur isn't all that good an idea on a tandem.

I'm not sure the fixie gang would take to it either. You're suggesting adding another part onto bikes who's owners pride themselves on basic simplicity. Or, I suppose in some cases, being different by being the same as eash other. You may want to try a thread in the fixie forum and see what sort of reaction you get.