What am I doing?

Since no one is really following this blog I have gotten rather lazy about it. I guess that's okay but I think I will take a different direction and be a little more casual about my entries. There is a new topic that I find interesting.

There is quite a following of a certain man that has "developed" a motor that allegedly produced more energy than it consumes. If this proves to be true then I can see a lot of people making these devices and selling power back to their power company. He has even received a patent related to this or a similar device. I will take a look at some the things I see in his device (or the devices made by his followers) and see if I can figure out what is behind the operation of this motor.

Later,

Irasohn.

Ballistics? What forces act on a bullet?

I have an interest in Target Shooting. It is a challenge that I enjoy to try to hit a small target at ever increasing distances. I like a bit of competition also so I want to improve my skills in marksmanship. I am not sure if studying the motion of a bullet will make me a better marksman but I will explore.

Here is a diagram showing the basics of gun sighting and the bullet trajectory. The path of the bullet will generally cross the "Line-Of-Sight" in two places. Although, there is the possibility that, even with a properly set up rifle, the bullet trajectory will not cross the LOS at all. Also, the velocity will decrease from Vi to Vf.

Immediately after exiting the gun barrel the speed of the bullet begins to decrease. The ability of a bullet to retain its speed is expressed by a Ballistic Coefficient. Another way to look at it is that the kinetic energy of the bullet will decrease as the aerodynamic drag of the bullet integrated over the distance travelled. I will explore how this correlates to the ballistic coefficient used in marksmanship.

Maple Seed will go to the Back Burner

I am still stumped. I have an idea of how this may be solved but I am not quite there. It will have to simmer some more.

I am going to consider some other topics now.

Maple Seed Gyroscopic Stability?

This has me stumped a bit. I don't want to use stability as it related to a spinning top. With the maple seed the torque or moment tilting the seed off axis spins with the seed at the same rotational speed. The spinning top models always show the top's rotational speed is greater than the precession or tilting of the axis.

I believe that I will have to develop a relationship of the moment tilting the seed off-axis and the moments caused by each of the finite elements of the model.

There are actually two different moments causing the seed to tilt off-axis. There is the tilt of the seed giving it what I call a dihedral angle. I flew model airplanes years ago and the dihedral angle is what gave trainer planes better stability. Looking at the front of the plane the main wing has a "V" shape. The dihedral angle is that angle that each wing is tilted up from straight horizontal. So this is one way the maple seed tilts. The other tilt to be considered is the moment that the air flowing over the wing will cause a moment tending to effect the pitch of the wing.

Putting more thought into how to solve the problem,

Irasohn.

Maple Seed Dynamics

I am starting on the Maple Seed Helicopter problem.

I want to begin by studying the mass and geometric properties of the seed. After something is known about these properties I will set out to study the dynamic motion.

In this figure I have sketched out a maple seed and broken it into discrete "squares". Each of the squares is assigned a relative mass number such as 1, 3, 5 and 10. The squares also represent discrete areas of the geometry (DeltaX by DeltaY if you will). The discrete columns and rows are identified by "n". A-n represents the area of any given strip in the subject column or row. These areas A-n are multiplied by the values of "n" which also represents the distance of the respective areas from a set zero datum. Summations are made of the area moments (A-n*n) and the mass moments (m*n). Approximate mass and area centroids are calculated and marked on the sketch. The black/white target marks the mass centroid and the dot down and to the right marks the geometric centroid.

We know that the seed will spin about some axis passing through the mass centroid. The angle of the axis, the rotational speed, pitch, falling velocity, etc.. will be part of the solution to be sought.

The geometric centroid seems to be an important quantity. I feel that the air resistance acting on the plan view area will be centered at this geometric centroid. The force will create a moment causing the seed to pitch downward. This will be part of the investigation to be completed in the coming days.

Irasohn.

Ideas for the Blog.

Some ideas that I am considering for investigation are:
- Bowling Balls? What is happening when they travel down the alley?
- Boomerangs? Why do they return?
- Maple Seed "Helicopters"?
- Coriolis Force? Is it real or is it just a name for some other force and frame of reference?
- Ballistics? What forces act on a bullet?
- Anamorphosis? What is it?

Initial Die Calculation Results.

The calculation of the Mass Properties would be very cumbersome and lengthy to perform by hand so I resorted to using a 3D Solid Modeling Application. The results show that the center-of-mass is slightly off-center. My die was modeled to be 50[in] on each side and made of polycarbonate. I used the large size in order to obtain results that made sense (the results using 0.5[in] die were not meaningful). By increasing the size by 100x I achieved readable results. Of course I made corrections in the results to bring it back to the scale of 0.5[in]. The mass was reduced by 10^6, linear values reduced by 10^2 and Mass Moments of Inertia by 10^10.



The die center-of-mass is:
- shifted 0.00065[in] away from the "six" and toward the "one",
- shifted 0.00039[in] away from the "five" and toward the "two" and
- shifted 0.00013[in] away from the "four" and toward the "three".

The greater the difference in the number of dots, the greater the shift was away from the face with the greater number.

The spinning axis would be determined by using the directions and magnitudes on the Mass-Moments-of-Inertia. I will have to determine how to read the results but I suspect the following:

- The axis will extend from the "four" face near the corner by "five" and "six" to - The "one" face near the corner by "two" and "three".

This would possibly result in a greater probability of a spinning die to come to rest on one of the two faces that the axis intersects. Pending a clear interpretation of the calculations, I believe these faces are the "one" and the "four". Furthermore, since the greatest shift in the center of mass was toward the "one" face I predict the greater probability of rolling a "six" than any other number. Note: The "six" face is opposite the "one" face which is also the "heaviest".

If you can help in the interpretation then we can make a more refined prediction.

Based on my assessment so far, there is ever so slightly greater chance of rolling a "six" than any other number.

But, Hey! Does it really matter?

I will be making a list of ideas to pursue. Comments or suggestions are welcome.

Irasohn