Mayday! Mayday!!!

[Thomas]

Hi Raj,

I used WM2d to simulate your design as I understand it. The large wheel, arms, and hub are simulated as plastic parts. The eight weights are simulated as having the properties of steel (heavier). Because everything is suspended from the hub, which is fixed to a center of rotation point, everything will fall to the lowest hanging point. The lowest hanging point is when two of the weighted rods are fully extended and equally spaced from the center. If the wheel is to rotate, then everything (except for the hub) would have to be lifted up on a continuous basis every 45 degrees, as the wheel rotated. The weights do not produce enough torque to lift themselves, much less the remaining wheel components. This is the main reason this particular design fails to continuously spin.

There is also another reason this type of design won’t work. In the past, I have simulated versions similar to this design. The main difference being the hub and large wheel having independent fixed centers of rotation. In that case, the wheel would be balanced in all positions. Although there will always be more weights on one side of the wheel, the torque required to do the lifting on the side with fewer weights is the same. The reason is that there is a wider gap between the weights which means they travel further, using the same amount of energy produced on the other side of the wheel. In my opinion, this is the typical result when using only gravity to try and make a wheel rotate on its own.

I have included a picture of your wheel design at its lowest balancing point. I have also included the WM2d model of your wheel design just in case anyone is interested in playing with it. Although I don’t think this design will work, I really admire your contributions to this site and you willingness to share your ideas with everyone. Keep up the good work


Tom
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[raj]

edited: resubmitted below

[raj]

Dear Tom,

I thank you for your valuable input.

I am still working on this new design.

And I believe, as Path_Finder has pointed out, that there is some part missing to allow only ONE spoke to stretch out at any time.

Raj

[Thomas]

Hi Raj,

One way to make only one spoke stretch out at a time in the six-o-clock (hour hand) position is to raise and support the larger wheel with a fixed pin, just like the smaller hub. Raise it enough so that when one of the spokes is at the very bottom (six-o-clock position), it is fully extended. If the larger wheel is pinned as I mentioned, this will be the only place (the bottom) any of the spokes can extend, one at a time, to their fullest. Then perhaps if you find that missing element, you'll have a good chance of making this baby spin endlessly.


Good Luck,
Tom

[raj]

Thanks again Tom.

This is exactly what I have been thinking lately during my model building attempt.

It is a question of finding the best way of achieving this fix vertical height of the rim, while everything else in the design stay the same.

Raj

[raj]

This is what, I think, will do the job:

Two small rollers on fix axles, one on either side of the vertical line through the hub:
See the two small red circles in the drawing.

This should allow the rim ( larger wheel) to fall furthest downwards and come into contact with the rollers, allowing spokes to fully outstretch at the 6 o'clock position, one at a time every 45 degrees turn.

Raj

[raj]

Ideally the outer wheel/rim should be on fix axle so that elbowed spokes and weights could follow the path as per design.

The central idea in this design is to have a wheel with an OFFSET hub, in order to manipulate distance between the hub and the rim at different positions of the wheel.

But it is difficult to stabilize a wheel with the offset hub eccentric on the axle.

In the absence of stabilization, the outer wheel in the design will move slightly up and down between one and two straightened spokes at the lowest position as shown by TOM's drawing above. And it will move slightly horizontally on the ascending side because the weights on the upwards flexed spokes will tend to press downwards forcing the spokes to straighten and thus pushing the outerwheel horizontally, which is contrary to design.

The drawing below shows a method of stabilizing the outer wheel/rim and still have the hub offset on a fix axle. Using rollers (small red circles in the drawing) on fix axles to constrain wheel to rotate in a fix position, without the need of a fix axle.

Any comments?

Raj

[raj]

The circle in red is a drum wheel.
The circle in green is a smaller wheel with circle in black as its hub on horizontal axle inside drum.

Can the wheel in red and the wheel in green rotate at the same speed?

I say a big ''YES''

Anybody disagrees with me?

Raj

[rlortie]

Raj,

Surface to surface without slippage they are bound to travel at the same circumference speed or velocity. The green simply travels (rotates) more than one RPM to the reds one RPM.

Ralph

[path_finder]

Dear raj,
Whatever the position of the axle, the contact between the red and green drums drives to a difference in the speed rotation with a ratio depending of the two radius.
But my question is first: how to oblige the black axle to remain at the same position?

[raj]

Ralph, Thanks.

I am concentrating on designs of wheel with offset hub, to force overbalance.

The drawing above is an example.
The red circle is using the green circle as its hub. I have, now found a way to make the wheels, one inside the other, as in the drawing, rotate without slippage at the same speed.

I think I have made an important find.

[raj]

Dear Path_Finder,

Following yours and Tom's input on my last auto wheel design where I have used wheel with swinging weights on offset hub, I have considered seriously both your comments.

That has led me to find what I said to Ralph above.

NOW, I am almost 100 % sure that my wheel with swinging weights will be continuously overbalance on the same side.

Raj

[rlortie]

Dear raj,
Whatever the position of the axle, the contact between the red and green drums drives to a difference in the speed rotation with a ratio depending of the two radius.
But my question is first: how to oblige the black axle to remain at the same position?

path,

I believe you are getting circumference (linear speed) confused with gear ratio RPM. How can a spur gear drive to a difference in speed rotation, it can't without stripping teeth off of the gears.

Ratio has nothing to do with speed, ratio only changes the time traveled to make a revolution, both driver and driven are traveling at the same speed. If they don't something bad is going to happen!

In speed (not rotation) their is no ratio depending on two radius. A belt drive is traveling around a large pulley at the same speed it turns a smaller pulley.

Ralph

[rlortie]

Raj,

An old example used many years ago involves an automobile tire. It is rotating, but that part which makes contact with the road is not moving! If it moves, then you are spinning your tires and are stuck!

The auto is moving forward picking up and laying down the tire at the same speed the car is moving forward. Using the forward motion of the auto as reference the tire is moving twice the speed of the auto,making up for that portion in contact with the pavement that is not moving.

Your circles are the road and the tire, where they contact they are both traveling at the same speed, in finite, where they touch there is no movement between them. Hence, the old term;"slipping a cog" comes into play!

Ralph

[triplock]

I have previously tried the offset circles like Raj's green and red ones above but I did it with the whole lot turn 90 degrees.

Ralph is quite right to differentiate between RPM and relative speed at the point of contact, but I admit that I hadn't thought of it that way . Although there is that distinction, clearly IMO it is the relative RPM that matters in this instance.

Chris