Final Project Report

The final project of which I have decided to work on consisted of redesigning a piece of exercise equipment called the "air glider". The idea came about one Saturday morning when I was having coffee and thinking about what I was going to do for this project. I was enjoying my coffee and flipping channels when I ran across a channel whose programming consisted of nothing but infomercials. The informercial for the air glider came on and immediately I thought of my kinematics project. The equipment looks fine however I do not think it would be very difficult to operate. In other words it looked too simple. I have created a Working Model simulation of this piece of equipment and as you can see, the machine gives no relavence to the leg of the human body. What I am getting at is the fact that they did not put a joint in for the knee or ankle. The fact that these joints were not added to the equipment made it look quite simple to operate which in my opinion made the person doing the informercial look quite silly. At that point I decided that this might make a good project for kinematics.

The first step was to sketch some initial ideas. (Sketches)

The second step was to get some information about basic human dimensions such as waist height and knee height. This was accomplished by using the internet. I entered a search string into one of the search engines and ran across an OSHA Ergonomics Standard. The standard conatined tabular dimensional data ranked by percentages of male and female contained in a specified group. Ranking the information this way is helpful because it allows the designer to design a product marketed toward a specific group of individuals. I choose to use the dimensions for an adult male in the 95-th percentile column because that is the group that I belong to. I figured that if I am going to build a prototype, I will want to test it so it has to be built to my body's specifications. The dimensions I ended up using are tabulated below.

Description: Dimension:

Stature 73.0 inches

Forward Functional Reach 35.6 inches

Elbow Height 46.5 inches

Waist Height 45.4 inches

Knee Height 23.1 inches

Upper Leg Length 25.2 inches

Leg Length 44.5 inches

Shoulder Breadth 19.2 inches

Hip Breadth 15.5 inches

Body Weight 238.0 lbs

Next, using a CAD package called Vellum, I started some detailed drawings of components dimensioning them to 1/5-th size. I did not bother dimensioning the width and thickness of each component as I had access to some 1.0 x 0.25 inch aluminum bar stock that was going to be used for the prototype. Once the linkages in the leg portion of the prototype were drawn up, I assembled them in an assembly drawing to help determine other dimensions such as the length and width of the machines frame members. The prototype's overall height dimension was determined by extending the legs straight down and allowing .4 inches (2 inch full size dimension) for clearance. This method of swinging the legs of the prototype served useful in determining the length of the diagonal members as well.

Click here for a picture of the prototype design. (prototype design)

The next step was to create a Working Model simulation of my design. (simulation).

The final step was to actually build the 1/5-th size prototype. Using the machining equipment on the 7th floor of the Eberhard center I began building the prototype. I cut the aluminum bar stock on the band saw and rounded the ends on the belt sander. Once all the links of the legs and frame were cut and deburred, I began drilling and tapping holes for the assembly of the prototype. I found some 1/8 inch bar stock that I used for the pin joints of the ankle, knee and hip. To make the pin joints, I cut a small length of the 1/8 inch stock and fed it through the holes in the respective members. At this point I smashed the 1/8 inch stock in a vise and then again with a hammer. This allowed me to create the pin joint by flaring the ends of the pin out over the hole in the links. Other links and frame members were attached either with pins or with screws, nuts and angle brackets or screws and tapped holes.

Click here for a picture of the final prototype. (Prototype).