Weird reflection

A few days ago on the Bacon Slicer, I was riding along the tarmac road that passes the front of the football stadium (City Ground, Nottingham Forest).

The offices and reception suite etc. all face the river, and this part of the building has glass all the way down to the ground. It is dark in the building, so the windows act as a giant mirror. The building is to my right, and the sun is low to my left.

My wheel is throwing an elongated shadow, and the “top” of the shadow almost exactly reaches the bottom of the window.

The shadow is spinning. The reflection is spinning in the opposite direction.

“Beyond” that is the reflection of my actual wheel which is spinning in the “right direction”.

The combined effect is that I can see three things spinning: the shadow, the reflection of the shadow and the reflection of the wheel. Each appears to be touching the next one in the sequence, and the middle one (the reflection of the shadow) is spinning the “wrong way”. It looks a bit like I’m riding a three wheel stack. (Triverticycle?)

Above the reflection of my own wheel, of course, is a reflection of me. Handsome brute.:wink:

I love things like this! They remind me how delightful the universe can be. Life is full of such beauty, all we need to do is get out of our heads long enough to notice. :smiley:

someone should make a 3 wheeled 36’er giraffe that would be so amazing!

I’ve always imagined a giraffe-coker… but three wheels… good luck to whoever rides it!

how about a coker wheel on top and then two 20" wheels?

Hmmm… that would get pretty tricky to balance I’d think… maybe two 20" wheels on top of a 36" but the other way around would be wierd…

either way it would be a wierd ratio and be kinda funky to ride.
that sounds really cool… you shoud get a video camera and fim it then put it on this thread.

so does tha mean you still go the same speed as if you were on a 20"?

Yeah, the 36" on top would be fast because it would be the one you’d be pedalling. With the 20" wheels on top, you’d pedal the 20" wheel, so it wouldn’t be fast like a coker.

Never mind the combination of wheel sizes, the only one that matters is the actual wheel you are pedaling. That action translates the movement of your feet into movement of the tyre.

Every contact between there and the ground - whether it is 3 wheels or 20 wheels, all the same size or every one different - simply transmits the movement of the tyre on a 1:1 basis. That is nothing lost, nothing gained. Wheels of different sizes will spin at different rpm, but the distance travelled and speed of travel are unrelated to how many rpm the wheel is doing. They are solely related to how many inches of tarmac the tyre covers. A small wheel spinning fast, or a large wheel spinning slowly, same result.

same result in distance covered, but not really same result…
try riding a geared 24" uni then a coker, THEN tell everyone thats its the same:p

what i would like to see is a coker wheel over a 20" wheel(two wheels)

Fundamentally different principle. The thing with a “stack” of wheels is that all of the transmission of movement is by tyre to tyre contact. This can never result in one tyre moving further than another in the same stack. Put a bigger wheel in the stack and it turns more slowly; put a smaller wheel in the stack and it turns more quickly. But in both cases, the “tread distance” covered is identical. The same amount of tyre tread is put on the road in a given time, and the distance civered isa the same.

With a hub geared uni, the sun and planet gears convert a given number of revolutions at the centre to a different number of revolutions of the wheel.

Similarly, with a chain driven bicycle or giraffe, the gearing acts at the hub. The same number of links of chain passes the big cog and the little cog, so the same “chain distance” is covered. However, by affecting the number of rpm at the hub, the speed of the vehicle is affected because the speed of the vehicle is the rpm multiplied by the circumference of the wheel.

what im saying is that pedaling at the same rate on a coker or a geared 24" you go the same speed(or the stupid idea of a stack of wheels). the large/small wheels act as gears to speed/slow the RPM of the wheels rotating below,with a 36"wheel on top and a 24"wheel on bottom it is geared to 36" with a ratio of 1:1.5.
(notice that the numbers i used are the same as a standard GUni)
the stack of wheels act as gears.

Is it not harder to ride the 24" GUni than the 36" standard coker?

You are apparently missing the point. You are confusing an increase in the speed of rotation with an increase in the speed of movement.

The stack of wheeels idea is not stupid. There are plenty of people who ride them. One wheel above another is sometimes referred to as a diverticycle. You pedal backwards to go forwards. On a three stack, you pedal forwards to go forwards, but the middle wheel contrarotates.

It is possible to use different sized wheels in a stack. If you pedal a big wheel and it turns a small wheel, then the small wheel will turn faster. In this limited sense, it is “gearing”. If you pedal a small wheel and it turns a big one, the big one will turn more slowly. Again, in a limited sense, it is gearing.

There would of course be handling and balance issues, as well as weight and extra friction, but they are not relevant to the point in question.

The important point is that in a stack of wheels, the movement is transmitted from one wheel to another by direct contact between the tyre treads. There is no magnification of the movement of the tyre treads. Ultimately, it is the movement of the tyre tread that dictates your road speed.

Let’s take a simple 1:2 ratio. Let’s say an 18" wheel stacked with a 36 inch wheel. (Both sizes are available, so it’s not a daft example.)

The 18" wheel has a circumference of 2 x Pi x radius, or Pi x diameter.

Diameter = 18 inches. Circumference is 18 x Pi = 56.52 inches (treating Pi as 3.14.)

So, in one revolution of the 18 inch wheel, a point on the tyre (or the contact patch with the road/the next wheel) moves 56.52 inches.

The 36" wheel has a circumference of 36 x Pi inches = 113.04 inches.

A moment’s reflection will show you that 113.04 is twice as much as 56.52. So in one revolution, the 36" wheel travels twice as far as the 18" wheel.

However, if the wheels are stacked, the number of rpm is “geared”. Pedal the 18 inch wheel and the 36 will turn half as fast. Pedal the 36 inch wheel and the 18 will turn twice as fast.

So, pedal the 18" wheel and in one revolution the tread turns 56.52 inches. It turns the 36" wheel half a revolution. The tread moves half of 113.04" = 56.52 inches.

Conversely, if you pedal the 36" wheel, in one revolution, the tread turns 113.04". The 18" wheel turns twice as fast, and the tread moves 2 x 56.52" which is exactly the same.

So in the sense of translating movement of your feet into movement along the road, the stack makes no difference to your speed. In a complex stack, you could have several different sized wheels all spinning at different rpm, but the net effect would be completely neutral, and you would be travelling at the same speed as if the wheel you were pedalling were in direct contact with the road. (Ignoring friction, weight and balance issues.)

Now, considering the geared uni, what happens is that you turn the pedals one revolution, and the wheel turns more than one revolution. For simplicity, call it 1.5, but other ratios are technically feasible. Something fundamentally different is happening here.

You could only achieve this effect with a “stack” by having side by side wheels with different diameters on a common axle somewhere in the stack. Now that would be silly.

Here is a link to a photo of a three-stack unicycle.

Silly? Awesome!

Someone out there must have made one, surely?


actually, no, im not.

you go the same speed as you would with a 36" uni with the weird stack, but it is the 24" wheel that is actually touching the ground, rotating 1.5 revs for every pedal rotation.
im just saying that the stack of wheels works exactly the same as a gear system.(not the one used in a GUni, but it has the same result)

and, no, i am not saying a stack is a stupid idea, ive even successfully ridden a 2 wheel uni(have to pedal backwards, haha)just that a multi-wheel coker is overkill…

EDIT:i just fully read your last post, and it is completely pointless in my openion, and not at all relevant to what i was saying. A 2 year old could have figured that stuff out.(in their sleep, i saw a 3 year old solve a rubiks cube in under a minute once.)
this isn’t even an arguement, just miscommunication…