Make:

• Pedal powered tank
• Escape from Berkeley
• Making Austin Weird: Viking Road Boat
• Bike tool roll
• Wacky Handcar Regatta Debuts in Santa Rosa, Calif.
• Handcar Regatta, this Sunday in Santa Rosa, CA

The taller a bike is, the more stable it is. They have a much larger moment of inertial so they react to rotational forces more slowly. Tall unicycles for example are easier to ride than short ones. Tall devices are much harder to mount and dismount of course. But once you are going, the ride is easy.

However, tall vehicles are more prone to chucking you over the handlebars if you hit a pothole.

Also large bikes are more stable this definetly seems like a Darwin Award candidate.

This bike even has a stability advantage over an ordinary tall bike; the extra spinning wheels increase the net angular momentum of the bike, which adds to the gyroscopic stability effect seen in all bikes.

I want that.

Imagine you see one the street (I doubt anyone of you saw anything like that) and what do you do?
If it was me, I would stop my bike and say "WTF?" But those other people in the picture don't even look back.
Photoshop? :)

In the two cities I have lived, portland, oregon and brooklyn, tall bikes like this are a fairly common sight. I don't get what the big deal is. This one doesn't even look that tall.

I agree with grobbins, tall bikes are fairly common. The only thing unusual is he added extra wheels that spin when he rides, which incidentally only add to the coolness factor, and not to his stability.

Don't believe it? Next time you're on your bike, consciously shift your weight such that you crash your bike. It's easier than you think, but it seems difficult because of your inherent self-preservation and aversion to injury.

sfazzio said:the extra spinning wheels increase the net angular momentum of the bike, which adds to the gyroscopic stability effect seen in all bikes.
I don't buy it. Adjacent wheels will spin in opposite directions, so wouldn't the angular momentum cancel out?

Yes, the angular momentum cancels out. If all 8 wheels were the same size, he would fall over instantly. This is a classic physics demonstration; you mount 2 extra wheels (free spinning, not touching the ground) on a bicycle and spin them. If the extra wheels spin in the same direction as the main wheels, then the bike is incredibly stable, but if you spin them in the opposite direction, the bike is totally unstable (like a unicycle).

Imagine balancing a 5 foot stick on the palm of your hand compared to a 2 inch stick, which would be easier to keep up?

Imagine balancing a 5 foot stick on the palm of your hand compared to a 2 inch stick, which would be easier to keep up?

I want to see him pop a wheelie!

All this talk of angular momentum and "centrifugal force" making the bikes more stable is rubbish.

Try this experiment: prop up your bike so the front wheel can spin freely, and set it spinning as fast as you can. Now turn the handlebars - it turns easily, right? I know mine does.

If the spinning wheel was a strong enough gyroscope to stop you from falling over, there's no way that turing the wheel to steer would be that easy.

Stability on a bike is easier when moving because you're able to constantly use small steering adjustments (whether by using the handlebars or by shifting your weight slightly) to bring the bike and your centre of gravity back into vertical alignment. The effect of the wheel as a gyroscope is negligable, especially on a good bike where they're engineered to be as light as possible.

The stability advantage of a tall bike (or unicycle, stilts, etc) is simply because when you start to fall, you're pivoting around a larger arc. Falling through 5 degrees from vertical might carry you 10 inches sideways instead of 2. The fall starts slower, takes longer and is more obvious. You have much more time to correct it.

Bugs -
The example about turning your wheel is false. Now, I could be wrong as Freshmen physics was quite a while ago, but turning the wheel involves applying a force perpindicular to the angular momentum of the vehicle, and since this would involve applying a cross-product of the two force vectors (which is a cosine of the angles between them), the cos(90) is 0 so you wouldn't feel the force of the momentum in trying to turn the wheel via handlebars.
In falling over, the force is being applied along the lines of the angular momentum.

I possibly flipped the angles. My understanding of the right-hand rule is distant and mediocre, at best. Someone with more mechanical physics experience can clear this up, but the basic point that you are bringing up is fundamentally flawed.

There is no reason for the six wheels that are not on the ground...

I've been using Photoshop for over 14 years now and I'm pretty sure this is a "fake". Cool concept though.928

I wonder how hard it would be to change one of those tires. It seems like a little extra work.

The stability of a bicycle has nothing to gyroscopic action of the wheels. Instead it is due to the angle of inclination of the headtube and headset to the horizontal. The more straight up and down it is the less stable; the further it is inclined the more stable the bike is, though after a certain point the bike becomes hard to steer. It's a trade off between nimbleness and stability.

What does he do when he has to stop at the lights?

I'm glad most people commenting understand that bike stability has almost nothing to do with gyroscopic effects and everything to do with the bike's forks!

IT WAS A SOUND STAGE ON MARS

Bugs,

The comments about angular momentum are dead on, this is basic high school physics. Most physics labs have a wheelchair wheel with and heavy tire and handles handles mounted on the axle. Spin it fast and it is amazingly difficult to turn.

In the real world I owned an old bike with steel wheels. I could ride it anywhere without hands, as it was very easy to balance. My modern bike has light alloy wheels and light tires, and I can only let go for very brief periods.

I am still surprised why people are so amazed at this. I've seen two of these in Nashville. Nashville!

Both gyroscopic effect and fork design (head tube angle and "trail") as well as wheelbase all figure in to bike stability. IIRC Captain Dan Henry built the unridable bike with opposing angular momenta from opposite-spinning parallel wheels. Go as fast as you want, it won't stay up like a regular bike. And if your head tube is straight up and down with no trail you will lose directionality. And steering does betray the gyroscopic effect, your bike at speed has to lean and turn simultaneously or you have to fight the lean and turn which scrubs speed. TANSTAAFL rules! You can see excruciating detail on all of theses in David Gordon Wilson's book which I believe is now at the MIT Press.

sunflower,
Ah so desu ka? It's the decreased rotating mass with my spiffier bikes, and here I thought I was just getting too old to ride no-hands! Have to go back to my steel beater and impress the neighbor kids! Whoohoo! Thanks!

Im pretty sure that if he had that many bike his CoG would be higher, resulting in being less stable about the lateral axis

the bike dosent appear to be moving

How do you mount/dismount one of these? This is what amazes me about them. Do you prop it up against something stable and climb? Do you need a couple of friends to spot for you?

When I had a tall bike (only two bikes high) I would get a running start and climb it once it was moving. I have seen several others do this as well. They really are pretty stable once they are moving...the bigger issue I found is that the center of gravity can easily move behind the axle of the rear wheel, causing immediate (and surprising) rotation. I would stop myself at stop signs and hold onto the sign post, then push off to gain momentum, In one situation this flipped the bike in the middle of the street, ouch!

Yeah, I smashed both my elbows popin a wheelie on my first & last tall bike. Wheel base was too short and my center of gravity went behind the rear axle and back I went. Seat was too wide to jump off so I went splat on my elbows. Guess that was better than letting my helmetless head hit. A properly built tall bike has an extended wheelbase to prevent this. This featured bike has an extra rear triangle added plus all that extra weight helps.

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