DrIsotope

It's best not to make disparaging remarks about Randy.

Tape2012

Randy runs in your rear tube (doh! That's the gerbil again) , no Randy runs in your front tire and give you 2 extra mph.

DrIsotope

Randy doesn't run anywhere, ever. That is beneath him. He operates a small apparatus connected to the crank spindle, like a Vivax motor. But he works cheaper.

Stormy Archer

Some serious advice:

• Yes, the thing about putting less pressure on the bars. Think about where your weight is on your bike - if you like a longer reach then yes it makes sense that you might put more weight on the bars. No hands, almost all your weight must be firmly planted on the saddle...
• However, pedaling and cadence do come into play. Sometimes, it helps me to grind harder and go for a slower cadence, because the leverage of your legs will help push your upper body into an upright position. And it just seems to help me feel more balanced on the saddle. Pedaling will help you stay upright and give you a sense of balance, because in some ways it's actually the most symmetrical thing your legs can be doing. Definitely don't go too grindy but a cadence where you're actually pushing helps.
• Another simpler thing about riding without hands that you might not realize without doing it is: unless your bars are super upright already, your saddle is probably going to feel kind of uncomfortable or at least pretty different. Your saddle is just not set up for it, you're used to having you back arched all the way down all the time. Speaking of which, stop that. Maybe hold onto a wall and try sitting straight up in your saddle to see what it's like.

About geometry... I don't really get what everyones on about. I have a pretty darn steep head tube angle and i love the way my bike rides without hands, it feels pretty easy. I think the cockpit matters though, just my opinion but wide bars with a short stem seem way easier to me than a 120mm stem and 38cm bars with heavy shifters on the end and all. I run a 60mm stem and 42cm bars.

Stormy Archer

Oh hey, does anyone else find that you can really pull up hard on your clipless pedals when riding without hands?? It's such a funny feeling, like, yeah this riskiness really does make me go fast huh...

Stadjer

Science still can't explain why a bicycle can stay upright by itself. Nontheless I'm pretty sure gravity is a force for stability through trail/caster/fork off set allthoug I do not fully grasp which parts of the geometry have which effect and how. I usually ride bikes with a laze geometry and sometimes I have to lift them, and I've been hit in the head by a handlebar more than once, because off the ground the front end suddenly moves very freely and that will keep surprising me every now and then. I will check it as soon as I got the wheels back into my roadster, but as I remember it you can clearly see the head tube moving up and down and the angle of the top tube with the floor change with swinging the front wheel. With a more agressive geometry it will be lot harder to see of course.

Tape2012

Um.....actually yes it can. The principle involved is called the conservation of angular momentum, or gyroscopic effect. This principle states that a spinning object will resist changes to it's axis of rotation. This effect of this principle is that if a bike's tires are spinning fast enough the bike will stay upright on its own. This principle was well understood long before the bicycle was invented.

That's how toy tops work. Also how airplanes navigated before GPS. There's even a solid state version of it (it uses the coriolis effect) in your smart phone and video game controllers to measure acceleration and movement.

Gravity does come in handy so your bike doesn't go floating off into space like ET. But in general when your on your bike gravity is not your friend and can occasionally be a *****.

A good way to demonstrate it is to take the front wheel off your bike, hold both ends of the axle in your hands with the wheel upright and spin the wheel. Once you have the wheel spinning at a decent rate, let go of one end of the axle. The wheel will not fall, it will remain upright, spinning in place supported only by one end of the axle. Once you've done this it becomes obvious how it is easy to ride with no hands.

Stadjer

Only recently it appears.

The land is pretty flat around here and I consider gravity and bike weight my friend. The stability of a heavy bike with lots of trail/ offset makes it efficient, the heavy wheels rotating add to the gyroscopic stabilizing effect and work as flywheels helping to keep momentum. If I had to react to other cyclists making jumps and trying to escape the peleton it would be an entirely different story of course, especially in the hills, but that's not the case.

The gyroscopic effect keeps amazing me, but it doesn't seem be the explanation. A link to the study is in the text below the video.

Deal4Fuji

I think that song went right over your head if you think it's about bragging or riding with no hands.

Homebrew01

Yes, I think we can create a formula that accounts for duration.

DrIsotope

Tape2012

to its axis of rotation

I watched the video, it was interesting. But I think the video is overlooking a few important things.


First in theory if you could build a bike that had no gyroscopic effect (I don't think that is what they did but just for arguments sake) that would still travel for a significant distance, that doesn't 'prove' that the gyroscopic effect is the primary mechanism at work in bicycles that you & I would ride. There are almost always more than one way to perform a task.


Second, they state as if it fact that if you have two disks spinning in opposite directions then the 'gyroscopic effect' cancels out. I would say yes and no. Since angular momentum is a vector (magnitude and distance), then two disks on the same axis spinning in opposite directions would indeed cancel out the angular momentum vectors, which most everyone agrees would cancel out the precession forces of the two gyros. But if you hold a gyro or a spinning bike wheel in your hands you can feel that the wheel resists changes to its axis of rotation in any direction, implying that more than just vectors are involved in the gyroscopic effect.


Ask anyone who designs helicopters what the most stable rotor design is and they will say that a coaxial twin rotor counter rotating design. This is why you see this design on most radio control helicopters.Hold one of these R/C helicopters in your hand and rev up the motors and you will feel a definite resistance to changes to its axis of rotation. In fact, helicopters of all type depend on the gyroscopic effect for stability.


I will agree that a bike geometry and encourages a bike to turn into a lean helps as well, especially at low speeds where the gyroscopic effect is lower.


Plus I know for a fact that without the gyroscopic effect my 1976 Evil Knievel toy stunt cycle would never have been able to do any of the awesome jumps that we got it to do. Until it broke of course.

wphamilton

I think there are several factors involved, and practically any combination of them can explain the self-stability of bicycles. Chiefly, the bike turns into the lean, and centripetal force counters the lean in the other direction, causing it to lean that way, and turn that way, causing centripetal force in the other direction, and so on.

DanBraden

Hmmm... that may be, but it's really hard to find a song about riding without handlebars!

Just sayin'...

Deal4Fuji

true

Tape2012

Technically, centrifugal forces counter the lean. Centripetal forces are causing the lean and turn. Just saying.

wphamilton

You should probably say, "the force arising from the centripetal acceleration", but either way what is the significance to the discussion?

Gyroscopic effect, btw, is nowhere near enough by itself to keep a bike and rider upright.

Tape2012

To an engineer, details are important. No engineer wants their resume littered with things like the Space Shuttle Challenger, Titanic, Hindenburg, Chernobyl, Ford Pinto, etc. You get the picture.

wphamilton

No, I don't. Details would involve correcting your "correction" and that would be way down my todo list.

As relates to OP's question, depending on gyroscopic forces is exactly opposite of helpful. If it were true (it's not) then the advise would be to sit like a sack of potatoes and let the wheels hold you upright. OP needs to relax at the core and apply control inputs as necessary with his hips.

Kapusta

I think PART of the bike's stability when ghosting has to do with the fact that when it starts to lean to one side, the front wheel will start to flop over to that side, and thus corrects itself.

ThermionicScott 

MikeyMK

I've often got my phone in one hand and a beer in the other, i've ridden three miles across housing estates without touching the bars, in fact my handlebars are really only a part-time thing.

I have electric, so i can remain no-handed up hills, and i have regen so i get a bit of slow-down but admittedly it'd be useful to have a knee-operated button on the top tube as a bit more of a brake.

Modern bikes tend to have nice short stems, but the fork geometry is more upright than ever and such little castor is probably the biggest challenge to no-handed stability these days. Plus i have to keep my balloon tyres pumped up hard, else sidewall deflection causes my handlebars to go into a shake-attack that gets worse until i grab the top tube with my knees.

Deal4Fuji

my favs were the Def Leopard drummer and the Tony Blair

Stadjer

It's not just a video but a scientific study into physics, so I'm out of my league here. But I doubted the cancelling out of the gyroscopic effect too, as a layman I would at least put the counterrotating wheels at the same axis to cancel it out. I doubt the whole cancelling out too, would a much heavier wheel rotating in the opposite direction destablize the bike? Does it matter what direction the wheel rotates in for the stabilizing effect? If you balance a rotating bicycle wheel vertically on your finger does it matter does it matter for the balance what direction it turns in if you walk forward with it? Is this a matter of cancelling out or are you just adding another stabilizing factor by adding a counterrotating wheel?

Cancellng works for example with pre WWII rotary engine aeroplanes, the gyroscopic effect of the whole engine turning would destabilize the plane, but with an engine at each wing the problem was solved. That I understand But that was about a force perpendicular to the direction of the aeroplane.

But is that all about the gyroscopic effect? A helecopter engine bolted to the hull just makes the rotor and and hull rotate in different directions. If you put a RC helicopter upside down on the ground the engine will rotate the hull and not the rotors, in free air it will rotate both. Just like a motorcycle engine doesn't care whether it's the wheel rotating, or the whole motorcycle rotating around the wheel. Often is a bit of both like in a wheelie.

Intuitively I'd say a bike with zero trail/fork off set will keep turning into that lean until it falls over, and it's gravity together with the trail that straightens the wheel again. It's not going in circles after the first lean, but gets back on a straight line.


Yes, they tended to evolve into Super Dave toys by themselves.

308jerry

You can throw as much science as you can at this thread, but in the end you still have to let go of the bars and lean back in the saddle....At 63 and riding a bike only since January it's an absolute hoot to go a hundred yards to a quarter mile without any hands steering . LOL