So, having done a little research, I’m starting to come up with some criteria about desirable features.
I had contacted the Bicycle Helmet Safety Institute , Randy Swart was able to provide some guidance on this. Specifically, he pointed to some research they did on the slip resistance of the helmet against various surfaces . Apparently this is a contributor to angular rotation inside the skull.
I’m not sure what the exact contribution is here, whether it’s torque applied to the skull and brain (which bigger diameters will also have an impact on) or something else at play.
He also pointed me to Smith Optics and 6D Helmets . The latter link, describes a system very similar to what I saw in the Vicis Zero1. That is, they’re relying on a filament that’s bonded at both ends, one end to the inner liner, the other to the outer shell, that’s permitted to deform and shear to absorb force.
I wonder if 6D Helmets is licensing Vicis’ patent.
The search query, ” coup contrecoup injury helmet ” yielded some interesting articles. Among them, was this article by Dewsnup, King & Olsen. Interestingly, when I try to access that article directly, I get an “IP Address Blocked” message, however, it can be accessed via Google’s cache .
Now, they’re in the business of accident litigation, and here they’re suggesting people take action against the helmet manufacturers. Ignoring that aspect, they link to some intriguing research. One such article being ” A New Biomechanical Predictor for Mild Traumatic Brain Injury “. There, they discuss angular acceleration as being of particular interest and the one that seems to be the least addressed in current designs.
MIPS is focussed on preventing that angular rotation. The Dewsnup, King & Olsen article also makes reference to another system, Angular Impact Mitigation (AIM) , which uses a honeycomb of aluminium that deforms. It’d be more like a heatsink and less an insulator too. Bike Magazine Australia mention some test results in their article ” Lifting the Lid “.
Based on the above, I’m starting to formulate some further ideas.
I had thought of a honeycomb of silicone rubber as an alternative to anything that looked like filaments. The fact that the AIM system uses a honeycomb structure, with a different material, is encouraging.
Either way, there would still need to be some sort of low-resistance shell. A lot of bicycle helmets have a very flimsy, similar to mylar, shell that if removed from the helmet, can be bent with finger-pressure. The purpose is to reduce friction with the road surface when sliding. This only needs hard-bonding at the edge — one of my old helmets uses electrical-style tape to achieve this.
An alternative might be a cloth with perforations, so that it tears away.
Under this, my initial idea of spines might work. The spines would deform on a direct impact and work to slow-down deceleration of the head. In a sliding type accident, when covered with a cloth cover, the cover would get stripped away to reveal the spines, which would then start to bend over, hopefully slowing down the angular deceleration in the process.
Then a traditional foam liner (or maybe an AIM-style one) can do its job.
This will need some analysis, I’m not sure how exactly to go about modelling this, finite element analysis seems the obvious tool and there are a few to choose from. I guess now is time to start reading up on how this stuff works.