PLEASE humor me? Still looking for a manual clutch.

[svejkovat]

I posed a part of this question a while back in a thread about gearboxes. I've been searching high and low for a simple manual clutch that would be suitable for the power and torque ranges that we're working with on bicycles. This is for a gasoline powered bicycle, but I'm posting here because the motorbicycle forums have very little interest in this. Input is an unmodified 35cc honda four stroke. About the torque and hp of a well conditioned cyclist.

I've been to all of the industrial, sports, and lawn/garden clutch manufacturers pages and even telephoned some of them. There does not seem to exist a compact lightweight method of manually engaging and disengaging a low speed low torque drivetrain!!! Amazing.

For the sake of illustration, the ideal would be what is pictured below, but instead of freewheel cogs there would be a torque arm an an actuating lever with internal clutch plates.

What I'm aiming for is the elimination of the centrifugal clutch at the motor and placing the clutch at the crankset. I need a manually engageable sprocket on the crank. If it is impossible to source or design (i have all winter with a mill, tig welder, etc) such an item, then the next option would be to use a clutch/jackshaft at one stage removed from the crankset.

I looked at the internals of a coaster brake

and was beginning to think it might be possible to adapt a coaster brake hub to a jackshaft/clutch. Sprockets could be welded to the hub, inner race of the freewheel, or to the stationary collar of that the torque arm is attached to (now it would be rotating instead of stationary) but I just can't seem to wrap my head around how to accomplish this. Actuating arm would be welded to the original input sprocket (i think). There would need to still be some application of a torque arm, but where to put it? I need to get an old coaster brake and take it apart on my workbench.

Please Please PLEASE!!! You guys have to help me. If I can overcome this little obstacle I can really get moving on this project. Without some method of engaging the transmission at the crankset the design turns into a rat's nest of extra freewheels, belts, tensioners, etc, in order to put this together. The clutch simplifies everything.

 

[JEB]

The only clutches that I have used are electrical 12volt magnetic disk type, along the same line that was used or still used on a auto air conditioner pump. I guess one could put a set of springs, bearing, and a lever, the clutch could transfer more torque with more pressure

 

[TylerDurden]

It might be possible to use a coaster-hub to stall a segment of a planetary gearset; where the gearset passes no power until one portion is fixed in place.

I can't visualize a pretty way to do it, but it might work. You could work the reduction into the gearset, if you are driving the cranks.

 

[liveforphysics]

You require the clutch to have progressive engagement and control over slip via a hand control? Or are you looking for something like a dog hub set to just engage 1:1 immediately?

 

[spinningmagnets]

The lowest-power Kart clutches are centrifugal shoes (shaped like a drum brake), but some of the higher power clutches (though centrifugally engaged) use friction plates. It was the only way to add more friction area within the small diameter allowed. They can be found with 2,3, and 4 plates.

I seem to remember these plates are about 3"/4" in diameter, and one of them would be more than strong enough. Assuming the motor cog will be small and the axle gear will be large diameter, the axle gear can be the pressure plate. Theres a dozen ways to configure it.

 

[12p3phPMDC]

A mini bike clutch?

http://www.faster-minis.com/clutch-manual-trail-bikes-kit-z-honda-50-vintage.html

You might be able to use the housing.....?

 

[lawsonuw]

Simple manual clutch? A loose V-belt or multi-rib serpentine belt and an tensioner pulley with an overcenter spring to tighten the belt up on demand. Otherwise a "dog clutch" is the next simplest. There's half a zillon variations on a dog clutch. Do some searching and make a few.

Lawson

 

[amberwolf]

You could try what I'm planning, which is to use the electric clutch off an A/C compressor from a car. It ought to work if it's at the high-speed motor end of the drivetrain. Mine will go on the treadmill motor shaft, with the pulley I'll attach to that going to whatever reduction system I end up using.

On mine, it will be to allow me to use regen only for braking, then to let the system freewheel with the motor shut off for coasting. So the clutch would only engage when I pull the brake lever or activate the throttle. At all other times it will disconnect the motor from the drivetrain.

At least, that's the theory.

 

[svejkovat]

Incidentally, I found another interesting gearbox for electric/gas bicycles.

Webpage only mentions left hand output shaft (viewed from the motor side) but the print catalog page indicates availability of right hand output shafts as well.

In some applications it might be preferred to mount the motor lengthwise. I understand that for battery/electric applications efficiency is much more critical and angle drives are not valued very highly. But this gearbox looks like it's right in the range of usefullness for powered bicycle apps. An email to Magnetek would confirm much of this, but it appears that it's a hypoid drive judging by the intersection of the drive gears. Also looks like a good bet that the pinion gear is self supported (instead of simply an extensionn of the motor shaft). If so it would be an excellent little gearbox to use with any variety of motors. Paring away a lot of the bulk would probably remove 5lbs. Using it with a gas engine (which weighs 3.6lbs pared down) I'm guessing that I could get it down to about ten to twelve lbs combined weight.

1590 grams equals 3.505 pounds.

I cannot use a centrifugal clutch. I have to put the engagement at the crankset (insufficient RPM for centrifugal) in order to isolate the engine and drive gears/belts entirely from the pedals so that the bicycle can be used as a bicycle when not using the motor. Any design that requires the pedals to spin the motors gear reduction train is going to be practically useless as a pedal only proposition. That's what all mopeds do already so there would be no use at all in trying to accomplish my aims.

The clutch has to be manually operable using a hand lever on the bars. I need progressive engagement and control since this must function to both start the 35cc motor while pedalling and to disengage the motor/transmission when coming to a stop. It will not be used for accelerating from a stop, only to supplement leg power when moving or, once moving to use motor power only. I've seen estimates of peak hp and torque at the pedal crank from a professional racer generally in the 700watt/0.5hp/1000inch lbs range. The unmodified trimmer 35cc motor even when measured at the speed reduction point, is not going to be too far off of that. I'm not trying to make this into a motorcycle. I'm just trying to add a professional cyclist to the crank whenever I think he can help. Lance Armstrong can average 30.5 mph over an hour of riding! To be able to do that with a tiny motor assist while pedalling, or even a steady 20 to 25mph with motor alone is somewhat where I'm aiming. I could travel with or without breaking a sweat... entirely as I wish. Lance metabolizes over 30lbs of body weight in the course of the TF. I don't need that. I'm 48 years old fercrissakes.

A dog clutch MIGHT work. I'm still thinking this through. Since the clutch is not inteded to accelerate the bike from a stop (I'lll always be pedalling from a stop), and since the crank and the rear sprocket cluster will be freewheeling (the front to keep the pedals from windmilling when using engine power) it is concievable that I can engage the dog clutch when the crank is not rotating and then pedal to a start. Progressive control would be nice, but if a dog clutch turns out to be a far simpler proposition I can live with it.

A tension idler with belt would not be a workable solution. Only works with v or serpentine belts. V belts are horrifically inefficient and intolerant of grease and rain and produce drag when not engaged. It's just an awful solution.

So a well made mountain bike crank, chain, and transmission must be engineered to handle more or less 1000inch lb or 83ft lbs peak. A 12vdc clutch, the ones I've looked at, range from 25 to 100 ft lbs torque rating. They weigh from 9 to 15 lbs. About half that might be eliminated with a lot of drilling and paring. I don't know how difficult is would be to adapt a cable/lever actuator to the mechanism. I still find it hard to believe that I cannot find this animal already manufactured. A manual stop/start clutch for a conveyor for instance. I can't locate one.

 

[spinningmagnets]

There's a device called a "slipper clutch". It is "connected" all the time, but its tension is settable. I can envision one coupled to a dog-clutch. The dog grabs instantly, but the slipper "slips" a little to ease the engagement until the RPM's of the engine/motor bogs a little and the wheel catches up a little. here's a simple farm-supply sawtooth dog-clutch. It could be held back by a spring, and engaged by repelling ring magnets?...

 

[amberwolf]

Not that it matters anyway, but in case this guy comes back, you might see how he treats people trying to help him:
http://www.diyelectriccar.com/forums/showthread.php/must-search-manual-clutch-really-quixotici-36016.html
Unfortunately he's deleted his own posts there, or you could see all of how he feels about people's attempts to help him here, so the only parts left are the parts I quoted of his posts when I replied.

 

[svejkovat]

Jeez, this amberwolf guy is a real terrier on my pantleg. I've actually become someone else's "cause". Like world hunger, or reducing drug crime. Wow! Thanks. I guess. I asked him (ok, maybe a little rudely) to just leave me alone and keep his wrist slapping nonsense out of my posts. Now he's followed me to another board?

Amberwolf was frankly acting the very irritating school marm and shoving less than useless moralizing down my throat. I did ask amberwolf to stop responding. He kept on. I asked that my membership be cancelled. When I returned to the thread (why are we always so damn curious?) there was another windy, withering, excoriating post from Miss Amberwolf that, uh, once again... had nothing at all to do with a clutch. I'd had enough and just deleted all of my posts myself. What gives?



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Oh hell with it. He's probably right anyway. This whole enterprise has just got me rattled. It finally took an anal retentive hall monitor to mince right up and tell me I"m loosing control of my temper. But I don't, after all, seem to be advancing this stuff at all through any of these posts. Perhaps it is true that a lightweight means of manually engaging a lightweight chain or belt is a mechanical impossibility. I'll drop it for now and let it gestate in the shop over the winter.


Thanks very much everyone for your input. We'll let this thread (and scattered others on the same topic elsewhere) mercifully (for everyone, especially amberwolf in his arm-waving anguish) sink into oblivion.

Bye

 

[etard]

HAHA!!! That last post was hilarious to say the least. Amberwolf really fired that guy up!!