Author: Jamie Cook
Date: 05 June 2019
Over the past six years I’ve crash tested hundreds of helmets. Not the most glamorous statement, I’ll admit. But anyone who knows me will tell you that I’ve thought and talked about practically nothing else than the design of bike helmets for the past 6 years. Testing, iterating, and reinventing the bicycle helmet became a total obsession for me, my professors – and now, for my team.
Unlike typical helmet manufacturers we are going to share our test results in detail. Most companies give the bare minimum, stating they are certified under the basic government requirements; yet not releasing the actual test results. This is only serving the helmet manufacturers, not consumers. In terms of safety, bike helmets are not all equal. It suits manufacturers to withhold detailed information. At HEXR, we are going to be transparent, and you’ll see a lot more detail on our test results because as cyclists, and engineers we believe the industry should change.
Most helmets are made from expanded polystyrene foam (EPS) to absorb energy and protect the head. This material was originally designed as packaging material in the 1950s. It isn’t a bad material for shock absorption, but it’s limited to only 30% effectiveness as proven in a published paper here.
We don’t see all-honeycomb helmets on the market because traditionally they have been very expensive to make. However, honeycombs have the highest crush strength to weight ratio, meaning they are excellent at shock absorption.
Now we have game changing technologies, such as 3D printing, we are able to create these honeycombs, using advanced materials that have the ideal softening response on impact. I will go into more detail on honeycombs in the next blog post.
Danger of current safety standards:
All helmets are required to meet safety standards that are set by various governing bodies. These standards have remained the same for around 20 years and have not evolved with new research. The automotive industry has continuously evolved its safety testing, yet the helmet market has not been as progressive.
The safety standards are designed to mimic actual head impacts by dropping a head-form with a helmet with a certain velocity onto an anvil. The maximum deceleration is measured and must be below the standard’s limit, which is typically between 250 and 300 G (1 G being equal to the force of gravity).
This safety limit would leave you with a critical brain injury and doesn’t test for oblique impacts that cause twisting of the head and severe head injury. Within the scientific community, it is widely recognised that head rotational acceleration is a critical head loading which can lead to brain injury. Despite this understanding, no standards test for it. That is why we engaged with leading researcher in helmet safety and brain injury, Professor Remy Willinger at the University of Strasbourg, to carry out independent oblique impact testing. Below I outline the results from both.
HEXR safety tests:
1. EN-1078: Linear impacts
All independent tests conducted at the British Standards Institute.
EN-1078 testing involves impact testing with eight different head forms, sized according to the size range of the helmet, and with different anvils (flat and curb shaped for EN-1078). This includes hot (+50ºC, 4-6 h), cold (-20ºC, 4-6 h) and wet conditioning, artificial ageing (spraying ambient tempered water 4-6 h at the rate of 1 l/min + ‘ultraviolet irradiation by a 125 W xenon-filled quartz lamp for 48h at a range of 250 mm’).
In addition, roll off testing and retention testing is carried out to make sure that a helmet does not slide off the head easily and that the strap and buckles will not fail under load.
HEXR performed excellently in the mandatory CE certification with an average linear force of 144 G, compared with the 250 G threshold.
2. University of Strasbourg: Oblique impact
The HEXR helmet was compared independently to the largest available data of tested bicycle helmets. Leading technologies, such as MIPS and Wavecel, used in helmets to reduce the likelihood of head injury, are also compared with HEXR.
The testing method is the state of the art: simulating real life accidents at 22 km/h. It is used by MIPS to validate their helmets and was developed by Professor Remy Willinger who has over 100 peer review papers to his name.
Over 27 tests are performed on each helmet to calculate the average value of linear deceleration, rotational acceleration and rotational velocity across three different impact angles.
In two of the three impact orientations (X and Z), HEXR performed the best that has been recorded for a road helmet. The full testing report published by Professor Remy Willinger, from the University of Strasbourg can be found here.
On average HEXR proved to be the safest helmet, shown as the red line in the chart below when compared with the 41 helmets. The chart displays % improvement or worsen to the average of all helmets tested.
The 41 helmets were tested by the independent Swedish Insurance company, Folksam, using an identical test method.
Due to the number of helmets tested, the data has been gathered over several years, the source of the data is here, here and here. In particular, it is the oblique test data that is compared with HEXR.
The average performance of HEXR was compared with 15 helmets that use MIPS technology and 1 Bontrager Wavecell helmet.
On average the HEXR helmet was in another league in terms of performance. The next best helmet was Bell Super 3 MIPS.