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An Inventor's Quest for the NHL Pt. 2
The Warm and Fuzzies
This series follows my attempt to develop an idea for a piece of hockey equipment into a product worn by an NHL goalie. Previously on the Quest: Part 1
So far, my experience with inventing has been a series of wild swings between “This is the greatest idea ever” and “This is the worst idea ever”. As time goes along and I learn more, the swings have gotten less wild, and have settled somewhere in the “This is a pretty good idea” range.
At first, I tried taming the uncertainty with back of the envelope calculations. I’ll spare you the details, but my first few attempts were pitiful. The answers made no sense.
I kept searching for the right set of equations, but eventually realized that the search was completely pointless. The truth was that no answer would change my mind. I would believe in my concept right up until a puck physically tore through it.
I was doing that thing that engineers do when they have an idea they really love — searching for evidence proving it’s right.
If I was just looking for something to make me feel warm and fuzzy, why trouble myself with complicated derivations? I could do that with a couple basic insights instead..
Warm and fuzzy thing #1: current cages are made of stainless steel or titanium. Kevlar is about 5 times stronger than stainless and about 3 times stronger than titanium.
But “strength” in the engineering sense doesn’t even best describe how Kevlar would behave in my cage. A more appropriate property is “toughness”, which is a combination of strength and flexibility and describes how much energy a material can absorb before it breaks.
A brittle material, like glass, is strong but not flexible (i.e., not tough). Something like taffy, which is not strong but is very flexible, requires a lot of energy to break (i.e., it’s pretty tough). Kevlar has a great mix of both and, as a result, is extremely tough. It’s 500 times tougher than stainless and 20 times tougher than titanium.*
*This is the modulus of resilience for the metals and modulus of toughness for the Kevlar. It is apples to apples in that this is the energy they can absorb and still be reused. To me, a bent cage is a broken cage.
It takes a huge amount of energy to break Kevlar - which is why it makes sense in high energy applications like stopping bullets, or stopping pucks going 100mph.
A stronger/tougher material means I can use less of it, which means that my cage will have better visibility.
Warm and fuzzy thing #2: in my net-like cage, the strings will be loaded in tension (they’ll be pulled). In current cages, the bars are loaded in compression (they’re pushed on) or in bending (a combination of pushed and pulled).
Whenever something is loaded in compression, it has to carry extra material for stability.
A rope can easily hold your bodyweight. But try to stand up the rope and it collapses under its own weight. Clearly it’s not lacking strength - just stability.
So if my cage is loaded in tension, it doesn’t have to carry that dead weight for stability. Less material, better visibility. Pretty simple!
I felt as good as I could on the technical side of things without having built a functional prototype; there was a winning solution somewhere in the general area of my idea. The question of viability as a business remained open though. Next time, I’ll get into how I tried to answer that.
Thanks as always for reading.
PS - I’m on Twitter now. Still figuring things out, but looking forward to more two-way conversations.