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Bicycle Stirrups

More efficient than pedal-cranking
  (+8, -2)
(+8, -2)
  [vote for,

The purpose of stirrups in horseback riding is to help you stay in the saddle. But in overall shape, the stirrup is the thing most similar to the gadget being described here, so I decided to steal the name.

Any cyclist will tell you that when you apply force to the pedal/crank, that force is more effectivly applied in certain crank-positions (horzontal to ground) than in other crank-positions (vertical to ground). Some rather ingenious ways have been devised, like elliptical pedal/sprockets, to increase the efficiency of force-application, as the crank is turned.

This Idea allows maximum efficiency all the time. The crank is removed (but not the drive axle and the front sprockets on it), and the stirrups are installed. Just like saddle-stirrups, each D-shaped foot-holder is suspended and can move freely, but is attached to a steel cable and not a leather strip.

Starting above the right foot, this cable goes up to an angled pulley (located at the side of the bike frame, to keep the cable from being hit by the bent leg), and down toward the front sprocket. NEAR the sprocket the cable is attached to one end of a length of chain (maybe 3/4 meter of chain). The other end of the length of chain is attached to another steel cable that goes toward the front of the bike frame and around a pulley, but on the other side of this pulley, the cable is now on the left side of the bike. What previously was described for the right stirrup is now mirrorred/duplicated for the left stirrup, which leaves only the twin ratchet/sprockets to be described.

The ordinary main drive sprockets of a bicycle are left alone. Ordinary derailleur mechanisms can still allow gear-shifting. We have to ADD two new sprockets to the drive axle, one on each side of the bike frame. Each of THESE sprockets is ratcheted, just like the mess of gears at the rear-wheel-axle.

Ok, if you got the picture so far (I just know I'm probably going to have to draw something and link it :), then here is how this drive mechanism works, in action:

As you use your right leg to press down (ALL STRAIGHT down) with foot in the right stirrup, you are pulling on the attached cable. Since the far end of this cable (despite the intermediary segments of bike chain) is the left stirrup, your left foot must go up as the right one goes down. Both chain segments are causing the two ratcheted sprockets to rotate (in opposite directions). Since you are applying a strong downward force on the right side, we want the right-side ratchet to engage, and the left-side ratchet to slip. Mechanical drive force is transmitted through the axle to the main (ordinary) front derailleur drive sprockets, and thence via the usual chain to the rear sprockets and to the back wheel.

When you have pushed your right leg down as far as you like (you can CHOOSE how far!), you then start applying vertical force with the left leg. Due to the same connected cabling as before, the right stirrup will now be pulled upward, and mechanical force will be applied through the engaged left ratchet/sprocket to the drive axle, while the right ratchet/sprocket slips.

That's all...

Vernon, Sep 19 2005

Kick-n-go http://users.pandora.be/dax/kickgomanual/
not exactly the same idea, but conceptually similar enough that [Vernon] might find it interesting [half, Sep 19 2005]

Of course, you may occasionally want to use them for standing in... http://www.kimmerst...h-galloping-250.jpg
...but this is mostly just another way of showing off your spurs. [normzone, Sep 19 2005]

Toe clips http://www.nashbar....estoreid=&pagename=
[half, Sep 19 2005]

Footloose Pedaling vs. Clips and Clipless http://gorp.away.co...xpert/needclips.htm
[half, Sep 19 2005]

Candadian patent 2120535 http://patents1.ic....2120535&language=EN
...the bicycle is driven by pushing the pedals almost vertically down. This allows better utilization of the driver's power... [xaviergisz, Sep 19 2005]

From Oda Nuryuki http://www.freepate...ne.com/6540244.html
Odd because a similar invention is from Garry Rumbough, I cannot seem to find the real bike I saw baked. [pashute, Jul 06 2006]

And another one from Robert Moore http://www.1000inve...detail2.php?id=1081
I saw this for real, but cannot find it now... [pashute, Jul 06 2006]


       Most interesting thought I've think you've posted here.
DrCurry, Sep 19 2005

       Heh, we all know there's no accounting for tastes/interests....   

       The biggest problem I see is keeping your right leg from hitting the ordinary drive sprockets, since there is so much freedom of motion. A GOOD chain guard design is likely required. The second-biggest problem is keeping the cables from falling off the pulleys, but I suppose if a pair of pulleys is used at each location, and the pair have their outer rims butted against each other, then the cable going through, in between the pulleys, cannot escape.
Vernon, Sep 19 2005

       One thought about efficiency of the traditional pedal crank system: I had a college roommate who was an avid road cyclist. He explained to me that toe clips allow more of a full cycle power input as the rider can pull the pedal up and increase the amount the pedal can be pushed forward prior to the beginning of the down stroke. The proposed system would eliminate that advantage and should maybe take that in to account when determining overall efficiency improvement.
half, Sep 19 2005

       [half], for bidirectional power input, the stirrup would first have to fit snugly around the shoe/sandal/foot/whatever, and then you add an extra cable to the underside of both D-shapes, connecting them fairly directly (whatever pulleys needed to do the job). Then the overall cable makes a loop, with no dangling ends (the stirrups) and is taut all the time. Yes, some freedom of motion is lost. Tradeoffs happen.
Vernon, Sep 19 2005

       The great part about circular pedals is that you can smoothly pedal all the way around, especially with toe clips.   

       Let go of the hadlebars, and if your balance is good you can keep going just fine.   

       Try that putting all your weight on one side, all your weight on the other side, etc. I t won't work.   

       This would give that "standing on the pedals and holding hard to handlebars to climb a hill" feeling all the time.   

       But on the other hand, why not synchronize them? Push both feet down at the same time, and get a big scoot forward? Just a thought.
GutPunchLullabies, Sep 19 2005

       [GutPunchLullabies], without having such a bicycle available, I wouldn't want to say that it is impossible for a good rider to maintain balance without holding handlebars. You can still sit as you power the stirrups. You do not have to stand. Also a major reason for standing is that very inefficiency at which force is applied to ordinary pedals, when the pedals are oriented nearly vertically to the ground. That is, you stand to apply more force to overcome the inefficiency. This Idea lets force be applied with high efficiency all the time, so the need to stand should be seldom.   

       Regarding applying force with both legs at the same time, this could be done by NOT connecting the stirrups to each other in an overall cabling arrangement. Each stirrup would have to be in its own independent cabling loop, one on each side of the bike, and you might have to add springs or something to help bring the stirrup back up after pressing down. Then you could apply force from both legs in any timing sequence you can imagine -- but note you have to put out some extra force to tension those pull-back springs, or else always use your legs to pull the stirrups back up (ratchet slipping) to prepare for the next power stroke.
Vernon, Sep 19 2005

       Thought this was going to be an idea for bicycling gravidas (gravidae?).
AbsintheWithoutLeave, Sep 19 2005

       As an experienced and thoroughly mediocre horseman, I can tell you that the best riders stay on the horse through balance, and the ability to grip the horse's back with their thighs and knees.   

       The sole purpose of stirrups is to complement your spurs and make you look even sexier than you already do.
normzone, Sep 19 2005

       Not to pedal the horse to make it go?! Dang, where were you thirty years ago when I was trying to ride our horses? Horseback riding might be much more fun than I thought.
half, Sep 19 2005

       I went from being a motorcyclist to being an equestrian. My previous training did me no good at all...my attempts to steer my horse through leaning did not contribute anything positive to the relationship.
normzone, Sep 19 2005

       Make fun of stirrups if you like. They actually have the purpose of helping warriors stay in the saddle when they are doing things like shooting arrows or slashing at each other, or impacting a lance into an opponent (ESPECIALLY that last item). Action leads to reaction, and stirrups let that reaction be transmitted to the saddle (and the straps that hold the saddle onto the horse).
Vernon, Sep 19 2005

       And, it's a lot easier than dragging around that step ladder for mounting and dismounting in a full suit of armor.   

       Don't forget standing up so you look cooler while parading the flag around the arena.
half, Sep 19 2005

       + I've off & on over the years daydreamed about how to accomplish exactly what you described. (I may be one of those who need a picture, though.)   

       I've also often wondered if you could teach yourself to run at an angle while sprinting for the same reason. (I think you would have to practise quickly snapping your trailing leg forward in plane and to not fully extend/leave bent when it makes contact/ the leading leg).
Zimmy, Sep 19 2005

       //down as far as you like (you can CHOOSE how far!)// +   

       Also, I don't believe toe clips do anything for power. Most riders I know who use them do so only to prevent slippage.
Shz, Sep 19 2005

       I never used the clips, but the straps that you slip your foot into allowed me to use muscles that I couldn't use without them. (During the upstroke).
Zimmy, Sep 19 2005

       Define "toe clips". I wasn't sure that was the exact, clear term. The term seems to apply to all manner of straps and such that are designed to keep the foot on the pedal. Even clip in shoes/pedals that hold until you pull your foot out to the side (or turn it at some angle I think) provide the ability to power the upstroke. (I dislike them all equally though I know the right ones are useful on technical trails.)   

       Maybe "traps" is the term I should have used.
half, Sep 19 2005

       That definition works for me, [half].   

       They are useful on technical trails (to prevent slippage). Here’s a question: How long can you use those upstroke muscles to add power? They’re nothing compared to quads for strength or endurance. Save ‘em for the running stage of the triathalon. Cycling performance is limited by your cardiovascular system, not your leg muscle power.
Shz, Sep 19 2005

       Dunno. I just brought it up because some cyclists do find them to be advantageous for power.   

       It might be a better question to ask how long I need to use them.(Say, in a short sprint to pull ahead of the guy I ride with who's ten years younger than me.)   

       Ha, triathalon, me. Good one!   

       I've had my legs burn out before my heart and lungs called it quits.   

       If you're ever in my neighborhood, bring your bike. We'll hit some desert trails. I'm always open to tutelage under people with superior knowledge, conditioning and skills. In exchange, I can supply the water. :)
half, Sep 19 2005

       <not looking> is this anything to do with childbirth?
po, Sep 19 2005

       Cycling with an epidural could increase endurance.   

       //It might be a better question to ask how long I need to use them//   

       That was the question. I think of it this way: Say you can pedal 800 watts max. How long can you do this? Not more than a few minutes. Why? You’re out of breath. Now say you have toe clips and can pedal 850 watts. You’re out of breath faster and can’t sprint for as long. I don’t see the advantage, but it seems a matter of opinion.   

       //I've had my legs burn out before my heart and lungs called it quits//   

       I hate it when my heart quits. :) Burning out your legs (lactate buildup) is a normal endurance thing, not a short-term power output thing.   

       //superior knowledge, conditioning and skills//   

       Way too much credit there. Love to go for a ride, though. There’s water where you live?
Shz, Sep 19 2005

       Only in the bottles we'd be carrying...and I've heard you can wring some out of a saguaro cactus...and maybe the horse trough if we ride by the stables near the Pointe Tapatio.   

       As I see it, the toe clip advantage for me would be just a little bit of extra reserve. Why not have the extra 50 watts available for a short sprint?
half, Sep 19 2005

       [po], rest assured, this Idea is safe to study. Enjoy!
Vernon, Sep 20 2005

       To clarify a seven year old question, toe clips refer to the straps that hold the foot on the pedal. In the racing implementation these were combined with a wedge on the bottom of the shoe that braces in the pedal, requiring the strap to be loosened to dismount.   

       To improve this obviously suicidal design, someone came up with "clipless" pedals, which involve a cleat on the bottom of the shoe that actually clips into the pedal, and can be dismounted with a twisting motion.   

       As a rule, clipping in (either way) does improve the ability of the rider to deliver power during more of the down stroke and some of the upstroke (pedaling circles), although this is going to be most pronounced for professional cyclists who do a lot to develop these muscles.   

       For the average cyclist the major advantage of clipping in is different. Without the clips, you need to maintain some down pressure on the opposite leg to keep it from slipping off the pedal. With the clips, you no longer need to do so, so you can stop fighting yourself while pedaling. That being said, for endurance rides (not sprints) the ability to bring some non-glycogen depleted muscles into play for a while can be a benefit, as it allows you to keep moving while the primary muscles recover, without exceeding your cardiovascular limit.   

       As to the actual idea, the major concerns I have would be the increased risk of "pedal strike" on pavement, the results of the harsher pedal strok on the knees, and the difficulty of dismounting from free-hanging stirrups (horses can balance themselves while you do so, bikes not so much).
MechE, Apr 05 2012


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