Second Round of Testing

After our first tests yielded such large forces we realized we needed more testing to see how different sizes would affect our results. We did more cans of each size, and crushed the cans to our minimum requirement of 1.5" x 1.5" x 1.5". This gave us the minimum forces that we would have to meet to crush the cans.

Forces are an average of three cans

As expected the force required to crush the can is 1700 lbs. Far more manageable than 8000 lbs. However, this is the minimum. So we did some further testing by taking some cans crushed to 1.5" x 1.5" and tested the forces to crush them to three different sizes on the final crush.

Click to enlarge

After these tests, we decided to go with the final crush size of 1.5" x 1.5" x 1". This brings our final required force to 3200 lbs, and brings us under the minimum crush size. And since more power means more money, this compromise will also reduce the cost of the machine.

While we aren't shooting for 8000 lbs anymore, our initial design is still going to need some reworking to provide more torque. So back to the drawing board.

First Testing Results

Before we could move any further we had to do some crush tests to determine the forces our machine will need to produce. We used a Tinius-Olsen materials testing machine here at VTC. This machine is normally used to determine the forces required to destroy a material in shear, stress, or strain. Here are a few pictures of the machine:

The Tinius-Olsen machine

The middle plate can be set at any height, and the bottom plate is lifted using hydraulics

Our first round of tests was for a target 1" cube. We used various forms that we created to crush the cans similar to the way we would on our crusher. For the first crush we jumped right to the 24oz. cans, since we knew that would provide the most resistance, and therefore require more force to crush. The final crush came in at a whopping 8,000 lbs of force! This was far more than either of us expected, and brought into question whether or not we could feasibly crush down to this size. Either way, we knew we would have to test other sizes as well. Here is our first set of results.

We started with the 24oz can but tested all three sizes for more complete test results

Feasibility Tests

One of the first things we needed to do was test the feasibility of our constraints. Mostly we just needed to prove that it is possible to crush a can down to the required size. While we will have to do the math for this and do more formal machine testing later, for this early step I just grabbed a can and smashed it with a hammer and a vise. 

We used a hammer and a vise to crush the cans

A crushed 12oz. can next to an uncrushed can

While this wasn't very scientific, it did allow us to determine that it was feasible to meet our size requirement. As I said, we will be doing formal materials testing so we can find out the actual forces involved, and compare them to solid aluminum.