Not Just for Wine Bottles and Birkenstocks
I had been really excited about finding something “special” for the helmet liners. Working on developing the wood shells, different as they are, affected the sentiment of the approach. It is an infectious interest in doing something different.
While researching the kinds of foams used in bicycle helmets (mostly EPS with some EPP) a link to an interesting study turned up on the pages of the Bicycle Helmet Safety Institute (http://www.grantadesign.com/resources/materials/casestudies/helmet.htm) that demonstrated why EPS is, comparatively, a very effective material for basing a bike helmet around. There are lots of materials it was compared with and, it claimed, only two of the other tested materials had similar (but somewhat inferior) performance characteristics, Cork and Balsa wood.
Intrigued that two organic materials were, maybe, “in the ballpark” of what could work I looked a little more. It seemed a bit 'pipe dreamish' that we could hope to improve on our theme by wedding a wood shell to cork impact protection. “How gimmicky is that?!” seemed a more likely result than “Wow, that's pretty legit” but starting a business shouldn't be all work and no fun so....
We made some contacts in the world that manufactures and develops cork products, flooring, shoes, duck hunting decoys. After learning where cork comes from, how it is made into the various things it is made into and what is known and still not known about it we were sent some free samples to do testing with by the Amorim Corporation (thanks Kim!).
Then we set about getting some testing done. Turns out that we couldn't find any of the kind of destructive impact testing done with cork that was unique to the type of impacts helmets are tested for. So, good news, it hadn't been shown to NOT work yet. We fabricated several samples to test that varied in their composition and structure and took them to the impact tower.
Along with samples of high density EPS and other commonly used commercial foams such as EVA we saw the data curves line up so that Cork and EPS were sharing a common ground. The cork seemed to be working, so far. After this we built some prototypes with wood and plastic shells containing cork instead of EPS as the impact cushioning system. We didn't really know just how best to assemble the cork, how much to use, how dense it should be etc. but we brought them down to the helmet tower in LA with fingers crossed. Could we learn enough about cork in this application to make it function as well as EPS? Without any significant engineering we had gotten pretty positive results with our samples.
Wood and ABS Plastic Shells with Cork liner during testing
The technicians at the lab were skeptical. First the wood shells and now this cork. Really? Well, they were excited too. Maybe it could work? So we loaded up the tower with a wood shell and then a plastic shell helmet that both were lined with cork.
After a short pause the tower released the helmet and it “WHOMPED!” on the anvil waiting for it. I felt my insides soften and let out a vicarious grunt. Another short pause and the computer registered a number that elicited an “that was fantastic!” from the senior technician. The wood and cork unit did more than pass, it really impressed. It kept g forces down to less than half the accepted value used to define passing. Part of me has been in a good mood ever since then!
That was just the first try. There were, from the testing, so many lessons on how to improve this first experiment and yet already we had succeeded. Onwards and upwards.