Wheel acceleration...

[bluesgtr44]

Tried to find a place to put this without starting a new topic and didn't know where to put it! Sooooo, I started a new topic for this.

I tried some experiments using WM2D..I only have the demo version. What I was looking into...The statement that it only took about 2 to 3 turns for the wheel to reach full speed. Now, that is pretty quick! Even though it is only 50 rpm's...I use the 50 for the first couple of one direction wheels. I wanted to find an appropriate weight distribution for achieving this.

I set up my wheel dividing it into 4 quadrants and by removing or adjusting the weights (position/mass) in the accending quadrants, tried to figure out what this distribution would be to reach full speed within the 2 to 3 rotations.

Me and ol' Ralph probably got our math degrees from the same place (Drunken State University) So, I will probably need some assistance with some of the mathmatical understanding of this. Jonathan, Ken, Bill...just to name a few will probably be better equipped to lay that aspect of it out.

First off...why am I doing this? I believe that the mechanism inside the wheel does basically one of two things. It either shifts the weight within the wheel or removes it totally. This difference can really have an impact on the physical structure of the wheel. When I build it...I want it to be versatile so I can make changes, this would be a big change in my opinion to have to plan for.

What I did....I was only able to get about a half to 3/4 of a rotation, I timed that acceration and just did the basic math (probably not correctly). I was not able to really calculate all the probables. But, even with just this, it was very difficult to adjust the accending weights (position/mass) to a point where I could see reaching the desired rate of speed. Now, I used several designs basically similiar to some of the M.T. drawings and got the same result everytime...it just didn't add up by shifting the weights to the center on the accending side, it would not, by my calculations (remember, I'm a D.S.U. grad) attain that speed within the 2 to 3 revolutions. Now, by removing the weight in the 6:00 to 9:00 quadrant..turning the wheel clockwise...this can be accomplished. I mean it is one heck of a difference!

Sooo, how far off am I on this one? Ken?....Jonathan?...Bill?....Read your guys stuff and the math you do and am really impressed. Like I said before, more of a hands on engineer than a mathmatician. Thanks for putting up with me.

Steve

[jim_mich]

If you were to wrap a string around a 5 foot diameter weightless wheel (just guessing where the weight is located inside the wheel) and then let it drop...

50 RPM * 6 = 300 degrees per second

30 inch radius * 2 * pi = 188.496 inch circumference

188.496 inch / 360 = 0.5236 inch per degree

0.5236 inch per degree * 300 = 157.080 inches of fall to reach 50 RPM

157.080 / 12 = 13.090 feet

157.080 / 386.0886 accel. of gravity inches per second = 0.407 seconds free fall to obtain desired speed.

Trouble is that darn weight just dropped out though the side of your outer 6 foot wheel! And a real wheel would have some mass to turn. And there would be other weights also.

If the single weight were 1/8 of the whole wheel including other weights then it would take 8 times as long to reach speed.

0.407 seconds * 8 = 3.25 seconds

[ovyyus]

I think mass imbalance is only part of the story. IMO, mass might also be accelerated backwards within the wheel in order to develop an additional reaction force. Rather than weights falling on the decending side, they might be accelerated upwards.

[bluesgtr44]

OK Jim...am I to understand that a "balanced" wheel would, generally speaking be a "weightless" wheel. If so, that is what I am trying to work with. I understand it would have mass...but it would all equal out. I understand the breakdown, what I was trying to acheive is the weight distribution it would take to accomplish 50 rpm's within 2 to 3 turns. For this to happen, the weight distribution would have to be VERY disproportionate...I think, anyway. Doing the tests with any kind of weight on the accending side seemed to come up very short of reaching the speed within the required rotations. but removing one of the weights from the accending sides really made a difference...especially the lower left quadrant on a C/W rotating wheel. I only divided the wheel into 4 quadrants as I was only after the acceleration information.

Do you understand what I am after here, Jim and why? And if you do...is it in your opinion relevant? Thanks Amigo!

[jim_mich]

A weightless wheel is only imaginary.

What I attempted to do was break the problem down to bare bones minimum. What I've shown is if you have a wheel and weights that together weigh 8 pounds and only a single one pound falling weight is driving the wheel at any given time, then it would bring the wheel up to speed in 3.25 seconds.

But then you have the problem of lifting the weights back up. Solve that and you have a working wheel.

[bluesgtr44]

Bill,

IMO, mass might also be accelerated backwards within the wheel in order to develop an additional reaction force.

I have been looking at this aspect also...The "grindstone" inside the wheel, hmmmm....

Jim,

So you do believe that the weights are lifting and not just shifting. Lifting could put the weight on the grindstone, thus removing it from the ascending side of the wheel. Shifting...the grindstone just forces it towards the axle leaving some weight to deal with on the ascending side. From the WM2D demo, and by the way thanks for introducing me to this program, I noticed a very big difference in acceleration by shiting/lifting. Shifting was much slower to accelerate than lifting, MUCH slower. It seemed as if there would be no way of reaching speed in 2 to 3 rotations would be possible. Am I wrong on this?

Steve

[rlortie]

steve,

I like your reference to D.S.U. When was the last class reunion? :)

You got me thinking about removal of the 6 to 9 weight. This the is is the only quadrant on the wheel that the weight plus the outer radius will cause a compound reaction with centrifugal force.

From nine to twelve the weight is still the same but the centrifugal force is decreasing in reference to weight inertia, as gravity is pulling it down and negating the centrifugal point of origin. Therefore the weights at nine to three are the same but the nine two twelve is loosing inertial mass as
twelve to three is increasing. There is a variable positive gradient potential from nine to three. Three to six and nine to twelve are not equal as three to six is gaining inertial and centrifugal mass while nine to twelve is loosing inertial leverage as it approaches vertical referrence with gravity and axis.

I guess you could call this "vectoring" as I am considering the inertial mass in vertical relation to axis. Gravity remaining constant and also stationary in a fixed vertical plane. In a circle all weights and inertial mass is changing axis torque with six to nine being a cumulative negative value.

I will quit rambling now and consider that DSU reunion.

Ralph

[jim_mich]

I have been looking at this aspect also...The "grindstone" inside the wheel, hmmmm....

I've never subscribed to the idea of a grindstone inside the wheel. I think the grindstone shape IS the whole wheel.

I don't see much difference between 'lifting' and 'shifting'. In most cases weights are moved in multiple directions. For instance a pendulum moves both sideways and up & down near the end of its swing.

[bluesgtr44]

Hey Ralph...Hoped you would get a little laugh out of that. Class reunions? We have those?

You're right about the 6 to 9 position and that is why I used that one for removal. I was able to start my WM2D designs in various different positions to see how that momentum force affected the acceleration and it does make a difference. It seems that to have the ability to reach the 50 rpm's in just 2 to 3 turns, that weight is removed...not just shifted towards the axle.

Guys...the way I work is, I try to gather as much information as possible and then disseminate the information into sections as they apply to certain questions. My main question that started this was "How would he have attached this device"...this trickled down from that question. Given the information the acceleration approach seemed to be a good way to find out how the weights might have been apportioned. Yeah, a little different approach maybe. Did I mention I went to D.S.U.?

I think trying to analyze "shifting" vs. "lifting" can have an appreciable impact on solving this and acceleration could help provide an answer.

Steve

[bluesgtr44]

Jim,

This from John Collins' translation:

Around the firmly placed horizontal axis is a rotating disc (or lower cylinder) which resembles a grindstone. This disc can be called the principle piece of my machine. Accordingly, this wheel consists of an external wheel (or drum) for raising weights which is covered with stretched linen.

The grindstone is what is hidden inside the wheel, is it not? The external drum has the cloth over it.

Steve

[rlortie]

The grind stone in the wheel.
A heavy wheel will build and store a quantity force of inertial energy, in exchange it takes longer with more force to accelerate. This can be utilized in a productive way to keep a wheel turning while the driving mechanism is shifting.

One examples can be seen in dragster cars where the fly wheel is shaved to lighten it, allowing quicker acceleration response. The opposite is found on old steam locomotives with very heavy drive wheels.

Regarding steam engines, the larger the wheel diameter, faster speeds could be obtained but with a loss of power. Smaller diameter wheels developed more torque at less speed and were designed to haul freight where speed was not critical. The demise of the steam engine was partially due to the desire for more power and speed. Drive wheels became so heavy and large that the tracks were unable to maintain the reciprocating jarring. Thence the diesel-electric became the choice of use.

There are two types of motive power that produce maximum torque at 0 RPM, they are a steam engine and an electric motor.

Ralph

[Jonathan]

I agree with Jim, the wheel is the grindstone. The wheel is an obvious choice for the shape of PM, but I'm sure Bessler wouldn't have been any less happy to have found one of any other shape. So the first thing he has to convey is the basics. Cylinder and disc are both correct descriptions, though most think disc is better. But grindstone is even better than both, because they are always the same shape (substantially wider than thick). I think the following emboldened terms are refering to the same thing. Both start with "this", indicating a reference to the previous use of a similar term: "this wheel" refers back to the second usage of "disc", which also has a "this" which refers back to the first "disc" usage.

Around the firmly placed horizontal axis is a rotating disc (or lower cylinder) which resembles a grindstone. This disc can be called the principle piece of my machine. Accordingly, this wheel consists of an external wheel (or drum) for raising weights which is covered with stretched linen.

I didn't understand what math you wanted done, is what Jim did all of it?

[Oystein]

I guess a constant torque in his biggest wheel would be about 30-60 Nm
to achieve full speed in 2 - 3 revolutions....

Depending on the total mass of the wheel..including air resistance etc..

It would equal about 3,5kg constant falling weight at the rim in a 100kg wheel + weight of weights....

That would be a pretty crazy unbalance from 4 pound weights...?
( 1 pound lifting 4 pounds could do it though :-)
(Several of them systems in side...for example 8 )


Oystein

[Michael]

bluesgtr44,

Did you throw the idea that using just two weights worked but it ran quite slowly, a statement made by Bessler, into the equation?

Mike

[Michael]

Jim, Jonathan,

Do you subscribe to the hammer mill grindstone image? This was talked about before a long time ago but dropped as peoples attentions wandered to other things. If not what are your thoughts on the form of the grindstone?

Mike