## The Center of Gravity

**Determining the Center of Gravity**

Is as simple as nailing a 6 or 8 penny finishing nail to a wall and affixing a string to the nail with a weight at the bottom of the string. You need to drive the nail deeply enough to hold the weight of the weighted string and a dangling horseshoe, making sure you’ve left enough room between the wall and the head of the nail to allow a dangling horseshoe to find it’s alignment without touching the wall.

Next, affix a piece of clear wrapping tape from one shank to the other about halfway between top and bottom of the shoe. I also wrap more tape on the opposite side to add strength for a further test. Simply hang the shoe from the tip of the nail from any point along the inside perimeter of the shoe. Pick a spot that will not slip along the perimeter. Draw a line that follows the underlying string on the clear plastic tape. It’s a bit easier to mark two points that can be connected after removing the horseshoe. Select two or three additional points and draw the appropriate line on the clear tape. Where all lines intersect is the “Center of Gravity.”

The image below shows the string attached to the nail and the horseshoe hanging from it’s first chosen position. Note the clear packing tape from shank to shank. Please ignore shadows caused by the flash. I have deliberately chosen this horseshoe because I know that it is perfectly balanced. I have placed a notch on the inside of each shank, to define the halfway point from top to bottom. If the center of gravity is perfectly centered and is directly opposite the halfway point (as on this shoe), the shoe is perfectly balanced.

**NOTE: **Most horseshoes are not perfectly balanced. Many horseshoes are tip heavy. This places the center of gravity closer to the tips. In 1998, Johnny Davenport filed a patent for his Mr. D shoes. He recorded the center of gravity for 16 horseshoe models, none of which, had the center of gravity centered.

Click on any image to provide a closer look.

Below is the third position chosen. The second position is already marked.

Below shows all lines connected. The point of intersection is the “Center of Gravity.”

To prove that the intersection point is the center of gravity, I have balanced the shoe on the tip of a nail. A weight as slight as a nickel placed anywhere on the perimeter of the shoe would upset the balance.

**Designing a Perfectly Balanced Horseshoe**

A bit of mathematics is in order here. Horseshoes are generally cast or forged. Developing prototypes is much cheaper when cast from the original. All of my shoes are cast from ductile iron. The generally accepted measure of volume for ductile iron is .28 pounds per cubic inch. That means that in order to create a horseshoe that weighs 2 pounds 8 ounces, the total volume of the horseshoe must equal 8.9285714 cubic inches. In order to insure that your horseshoe is perfectly balanced I divide the horseshoe into 4 equal quadrants. Each quadrant has to occupy a volume of 2.2321428 cubic inches.

**NOTE: Information changed — **I had to make a change in the calculation of weight based on a different volume requirement for ductile iron. When trying to calculate the volume requirement for 2 pounds 8 ounces I was given erroneous information indicating that ductile iron weighed .28 pounds per cubic inch. Actually, that was the weight for steel and not ductile iron. The actual weight per cubic inch of ductile iron is .245 pounds. I kept receiving prototype castings weighing 2 pounds 5 ounces. The new figure of .245 means I have 9.8 cubic inches of volume to work with. This permitted me to add addition design features in the final casting. The prototypes are now being received weighing in at 2 pounds 8 ounces.

The image below shows how this assignment of volume is accomplished. This precision is virtually impossible with prototypes designed in wood. It is only when using 3D computer software that it is possible to make the very fine adjustments to equal this precision. It is very easy to add a little or take a little away. The image below is a representation of the design by quadrants. You will note that the left and right side are identical. Therefore, I only need to design one side. I only need to design the bottom half and the top half of one side. The bottom left occupies 2.2321428 cubic inches and the same for the top left. I join the two halves to form the left shank. I mirror the left shank to create the right shank and join these two halves. Voila! shoe done. Of course, it’s not quite that simple, but it describes the process. The only thing left is adding the company name “Hilfling” on the left calk and the unique name on the right. I print the output in a format acceptable by a 3D printer and the printer output goes directly to the foundry for casting.

**Perfect Balance — A New Area of Interest**

When I was deciding whether to go into production on the 4 prototypes I had initially designed, I had a number of NHPA pitchers test all 4 shoes. Without fail, every female pitcher preferred the FlipOn. Why? I asked. “It just feels perfect in my hand”, was the usual response. I wasn’t really certain why that was the case. It was not until sometime later, when I was checking the center of gravity that I realized that the FlipOn was almost perfectly balanced. I noticed that even though the shoe weighed 2 pounds 8 ounces, it felt light in my hands. With the introduction of 3D software I was able to concentrate on perfect balance. The horseshoe that you’ve been viewing on this page was the result. When I received it back from the foundry, I wanted to check the various flips and turns. The single flip worked perfectly. Very smooth, almost slow motion without any wobble or shank drop. I don’t throw a turn from 30 feet, but, thought I’d try the flip-turn. I took the 3/4 turn grip with my index finger in the shank notch. Perfect! A slight arm rotation and slight flip and a beautiful flip-turn. Finally, I tried the 1/3 turn holding the shoe at the right hook calk described in one of my earlier Parts. Again, perfect. The shoe flew flat and true without wobble. I was so excited about the results I’ve designed two additional shoes, both perfectly balanced, 3D printed and off to the foundry. The two on the way back are part of my “Tribute” shoes previously mentioned.

**Why is Perfect Balance Important?**

When the center of gravity is precisely centered, the shoe will rotate like a frisbee without any discernible wobble during rotation and the center of gravity will not deviate from its track to the target. Placing a small weight on the outside of a frisbee would demonstrate visually the impact of an unbalanced object. A balanced flipping shoe would emulate a rod attached from one shank to the other and the shoe rotating around that rod. Again, the center of gravity would track perfectly to the target without deviation.

The following is a list of the most obvious advantages of proper balance.

1. It provides a much smoother flip or turn.

2. It makes the shoe feel lighter.

3. It eliminates the shoe dip from centrifugal force on the forward swing caused by a weighted tip.

4. It eliminates the need to add additional flip effort.

5. It eliminates any unusual unbalanced rotation.

6. It eliminates any sloppy rotation due to heavy or light spots.