A simple cam

[nicbordeaux]

So, what's the take on a single weight wheel with a cam on the hub (eg, the revolving part, not the axle) ?

Cam so shaped that slack string and elastic band comes under tension (accumates F) from say 4 to 6, the releases immediately from 6 to 8 ?

The elastic band would have to "made" over the hub to avoid winding problems.

Path_finder was kind enough to point me to topic http://www.besslerwheel.com/forum/viewt ... 6439#56439
but I don't think this is pertaining to the same system.

"Logic" says result will be efficiency of wheel without band less (at least) inefficiency" of elastic band, or spring. But logic isn't always 100% right.

So basically, the question is : who has tried this one, and what were the results ?

[Bill_Mothershead]

The universal language is....a picture.


Please.

[nicbordeaux]

Indeed 'tis, but I have nothing to pic, and can't draw. Here's a feeble attempt, hope it conveys the idea ...

[triplock]

Nice idea, and don't worry about the pictures. Mine aren't much better.

I accept that the bungee will tension as the fall of the rim weight rotates the main wheel, thus rotating the elliptical cam to the vertical elongated position. I assume that there is gearage to allow the main wheel to travel thru 1/2 turn and the cam 1/4 turn.

At the bottom of outer rim weight travel, the bungee is pulling equally up both sides of the cam, therefore there is no inclination for the wheel to turn one way or another as a result of this stored elastic force. :-(

If you detached the wheel from the back support and it will make a nice pendant/chain combo to give to some young lady :-)

Regards, Chris

[Bill_Mothershead]

OK. My interpretation....

The weight falls.
Since it is attached to the wheel's rim, it falls in a circle.
It transforms Potential Energy into Kinetic Energy.

As it falls, the bungee cord [spring] is stretched.
It is capturing the Kinetic Energy and stores it as Potential Energy.

Ideally, the weight does NOT accelerate much and as it
reaches 6 o'clock it has NO momentum, NO Kinetic Energy.

As the weight passes 6 o'clock the bungee cord springs back.
It transfers its stored Potential Energy to the weight
which moves (thus Kinetic Energy) but since the weight is
going up, it is really gaining Potential Energy.

Finally, as the weight reaches 12 o'clock, all the Potential
energy of the bungee has been transferred back to the
weight.

Reminds me of the concept of a heavy weight dangling down
from a long spring, gently oscillating up and down.

Is this anything like what you are trying to describe?

[triplock]

I'll respectfully disagree with your analysis Bill.

The pendulum is not swinging down in an arc in the more normal unhindered manner. The bungee, as it stretches, is drawing the life blood out of it as it falls. Depending on the strength of the bungee, it will either cause the rim weight to stop short of 6 o'clock, lock on at BDC, or rise thru to an elevation far less than if the wheel was unpeded.

The bungee will not efficently pulse back a force to the rising weight, via the cam. In any event, the energy out of the stretched bungee is only equal to the energy put into thru stretching on the down stroke.

Final 12 o'clock position doesn't even come into it. It'll be lucky to be in time for supper at 7 oclock. Sorry :-(

kind regards, Chris

[path_finder]

Dear nicbordeaux,
Hereafter is the original drawing with the additional springs (according with my idea).
The springs are in violet.

[Denker]

I read in picture legsQ_000.png grounded.
I think this is hard or not possible. The axle are turning with the wheel !
where we can fix anything ?

And Bessler wrote:
everything in the wheel is turning around...

[path_finder]

Dear Denker,

I apologize do not be explicite enough.

The cam is fixed at it's stable position by a shaft centered on the main axis and inside another hollow shaft, like explained in this old drawing:
http://www.besslerwheel.com/forum/download.php?id=6185.
On the other hand the main wheel's shaft is hollow and rotates around the first small shaft thanks a rollers bearing.
Therefore the both shafts do have the same axis but are independent.
This design is very close from what you can see on the Merseburg wheel, where the power is collected on the hollow tube thanks the rope.

In another post (http://www.besslerwheel.com/forum/download.php?id=6520 I expressed another way this design (the hollow tube) can be used.
But there is still an important question: why these two bearings are so much allongated?. A proposition is given in this old post (and the followers):
http://www.besslerwheel.com/forum/viewt ... 1553#61553

This forum is full of some important data (I don't speak specially for me, there are a lot of competent contributors).
I just regret that a big amount of useful data apparently are lost or forgotten, and few years after we are obliged to give again the same answer.
A good source of abundant data is the link 'Albums' in the index page (or here: http://www.besslerwheel.com/forum/download.php?m=1103), then select by name or date in the rolling list.

[nicbordeaux]

OK. My interpretation....

The weight falls.
Since it is attached to the wheel's rim, it falls in a circle.
It transforms Potential Energy into Kinetic Energy.

As it falls, the bungee cord [spring] is stretched.
It is capturing the Kinetic Energy and stores it as Potential Energy.

Ideally, the weight does NOT accelerate much and as it
reaches 6 o'clock it has NO momentum, NO Kinetic Energy.

As the weight passes 6 o'clock the bungee cord springs back.
It transfers its stored Potential Energy to the weight
which moves (thus Kinetic Energy) but since the weight is
going up, it is really gaining Potential Energy.

Finally, as the weight reaches 12 o'clock, all the Potential
energy of the bungee has been transferred back to the
weight.

Reminds me of the concept of a heavy weight dangling down
from a long spring, gently oscillating up and down.

Is this anything like what you are trying to describe?

Thx Bill, I've highlighted in red the parts which I intended to convey. In the "mind scenario" the wheel with weight (attached to rim, not a movable weight) isn't stopped. It is slowed. The spring or bungee is suspended from a slack at 12 tether so that it gets stretched at about 4 to 6, then on passing 6 immediatedly restores energy. say from 6 to 8. From 8 thru 4 it is no longer under tension or acting in any way on wheel.

You could simplify even further and do away with the cam, just have an off-round wheel with the requisite shape to induce the above behavior.

Likely, as said, won't work. But can't be sure until it's tried. In fact, it's a cert it won't work on it's own, but when using OOB with gizmos trundling all over the wheel and arms flailing about, suitable profiling of the cam/wheel would remove from less needed area and restore to the critical point.

Acceleration in "freefall" is utterly necessary to gain speed through most of the downstroke (12 to 4) to gain momentum/velocity/acceleration.

Sorry to path_finder and other cleverer blokes than me, more than one weight on a wheel and it's not screwed down hard, my eyes glaze over and mind goes blank .

[Tarsier79]

Hey Pathfinder

Regarding your above design, you may have an issue with the weight at 12:00 and its path to the weight at 2:30(providing it is meant to turn clockwise). Perhaps instead of the horizontal (straight) parts of the cam you could shape the cam more like an egg on its side.

[triplock]

Although your above design of moving orbitting weights oob, by use of an offset fixed faceway, is along a well trodden concept path, and will not work by the way, it has been noted in my short time on this forum what a selfless contribution you make.

You are by far the most open and prolific contributor, and whilst others just lurk in the back ground offering a few bread crumbs of retoric, you tip in a whole loaf.

You should be applauded for this.

This weeks green dot goes to path_finder.

Chris

[nicbordeaux]

Hey Pathfinder
you could shape the cam more like an egg on its side.

Yeah, but which side of the egg ? Like, which corner of the egg should be where ?

[triplock]

The elongated part of the egg would be horisontally to the right, thus offsetting the pendulum weight further outboard on the downstroke.

Chris

[triplock]

Also as well, although the snap shot of weights in this position shown look pleasing, what must be considered is a proportion of the pendulum bob weight is transfered back to the outer frame, via the rigid rods.

I once had a rather nice looking elyptical bearing raceway mill out of 30mm clear perspex, which formed the back plate of numerous experiment.Each and every time, the paired weights, although initially preload in an advantageous position just bound up after about 45degrees of rotation.

Chris