How To Invent (Almost) Anything : 5.4.3. TRIZ Thinking: Plane Hatch

5.4.3. TRIZ Thinking: Plane Hatch

Here is an example of a problem we solved using TRIZ when building a large (six-foot wingspan) radio controlled model plane.

We had a fuel tank which had to sit at the front of the plane. It had three pipes to be connected to it. We could only place the pipes onto the fuel tank if they were long enough to extend into the middle of the plane where we had access from the top. But if they were this long we knew that they would risk being crushed as we pushed the fuel tank into the front of the plane.

This is a contradiction between the parameters of Length of moving object and Reliability. According to the Contradiction Matrix it can be solved by Principles 10, 14, 29 or 40, that is: Prior action, Spheroidality, Use pneumatic or hydraulic systems or Composite materials.

The last two give us ideas but involve changing the pipe more than we want to. Spheroidality is interesting in that we could think or how we might get the pipes to be rolled into a ball as they are placed inside the front of the plane.

We chose Prior action: we would build a hatch which means we can get to where we want to fit the pipes. But we then had a problem of how to secure the hatch without ugly and complex devices. We saw this as a Reliability vs. Waste of time contradiction. TRIZ suggests Principles 10, 30 and 4 (Prior action, Flexibility and Asymmetry).

We had thought of a hatch with simple straight sides across the nose of the plane. Asymmetry made us think of cuts at an angle in the thick balsa wood. This also fitted with the Principle of Self-service, how to get the plane to hold the hatch down. The hatch would now only slide across and could not pull out vertically.

But we had another contradiction. If we made the hatch so well that there was not an ugly gap it might bind to the plane through too much friction (Accuracy of manufacturing vs. Harmful side effects). Again TRIZ suggests Asymmetry and New dimension. So we extended our asymmetry so that the cuts across the balsa were such that we had a wedge-shaped hatch, as in Figure 5.3. Now the hatch binds only when it buts up against the body. We had one final problem to solve. How to stop the hatch sliding out? (as it is wedge shaped it has no friction once slightly away from the body). We felt we needed a 90 HOW TO INVENT (ALMOST) ANYTHING Mediator, something between the body and the hatch. We did not want it on the outside so we chose New Dimension (on the inside of the plane body).

Fig. 5.3 Plane hatch example

How were we to fit a rod through the body into the hatch so the body and the hatch would be held together? We did not have a drill long enough for such a small hole, however. So we chose another TRIZ Principle: Self-service..

We made the end of our rod slightly flat and put it into the drill and used the rod to drill its own and perfect hole!

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5.4.3. TRIZ Thinking: Plane Hatch

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