Week 9 - Prototyping Meeting (Lever Mechanism Testing)

Today we met as a team to explore the possibilities for igniting and extinguishing the gas flame. We thought it would be beneficial for all members to be present for this experimentation as this forms a large part of the product output interface and all needed to understand the mechanism and be happy with the output produced. So we met at John's house and began the process of mocking up the mechanism.

So leading on from my last post, the next step in prototyping was to test the initial gas ignition/release concept that I had sketched on the run. As you can see in this sketch it involves a pivoting wedge that is controlled via a single rotary arm fitted with a sprung wheel. As the wheel travels past the pivoting wedge it moves the wedge in such a way that depresses the gas release lever. This mechanism is repeated for each gas outlet around the flame dial. An electronic igniter controlled via the circuit ignites the gas which enables the rest of the flame dial to be ignited sequentially. This is crucial to the interface that needs to display the percentage of the group that is working on the project. 

Initial diagramatic sketch of the gas release mechanism

This diagram only shows the top view of the mechanism so a number of elements needed to be constructed to control the depth of elements within the mechanism. These elements include the pivoting wedge, the supporting frame and the rotary arm that supports the wheel (the aim is to control this with a single 360 degree servo motor).

The first part constructed was the wedge as the combined height of the lighter and the wedge determined the height of the frame and rotary arm.

A balsa wedge was used to achieve the correct shape for the wedge

Next element to construct was the frame. Using some salvaged meccano parts the frame was constructed to support the wedge and the lighter. Here you can see the wedge rotates with the screw a a pivot point. The lighter is in position with the gas lever ready to be depressed.

Lastly, rotary arm with the sprung wheel was fabricated. Again, more meccano parts were used along with a spring from a retractable pen. This actually provided too much pressure so the flex in the frame ended up providing the pressure required.

Side view of rotary arm

Here you can see the wheel retracting and returning to full length under the springs pressure.

The last thing that we needed to test was the length of time that the lighter can remain lit for. The packaging warns against the lighter being lit for longer than 30 seconds however we needed to test to see what would happen over an extended use. After a few minutes the  surrounds of the lighter top began to melt and catch fire so we decided that the duration of the prototype demonstration needed to be kept to a minimum while still proving the concept. 

This raised concerns about the materials that would be used in the final product however John will address this later in the design of the final object.

Today was a very productive session as we finalised the flame dial mechanism and allowed both the Object and Behaviour sides of the project to continue to move forwards knowing that the design was possible with the use of a single electronically controlled part, the servo motor. Unfortunately the prototype was not recorded in action so I will be posting up a record of its operation over the next few days. Again... watch this space!