Posts
213
Joined
12/9/2018
Location
Prior Lake, MN, USA
Edited Date/Time
4/10/2020 3:13am
I have been a long time Arai user but with the newest rotational prevention technologies, see the potential value those technologies can bring for rider safety. Coming from an engineering background and reviewing the Formula Benchmark results, I have quite a few questions that might be of interest to the broader group. First, the ICORBI papers that Fly references are pretty interesting. Just Google ICORBI from 2016 through 2019 and then find papers referring to helmets. Tons of research out there, here is an example: http://www.ircobi.org/wordpress/downloads/irc18/default.htm
Fly Results:
http://www.wpsstatic.com/miscimages/info/Formula-Benchmark-Data-Testing…
Looking at rotational results:
1) Why were the two speeds chosen...4.2 and 7.1 m/s correspond to 9.3 and 15.8 mph respectively. Seems relatively low when considering typical riding speeds?
2) Looking at the rotational data closer, at 4.2, the Formula was ~ 2nd or 3rd, but then was approximately somewhere around 4th or 5th at 7.1 m/s with not much differentiation between the top 7. With just two data points: 4.2 and 7.1 m/s, seems like the Rheon advantage diminishes/goes away with increased speeds?
3) Given the relatively low and medium low speeds tested, it would be better to characterize how Rheon performs over a more representative speed spectrum. Curious if Rheon is a better technology at lower speeds but then another technology becomes superior as speeds are increased
4) There is more and more research coming up assigning probability of a traumatic brain injury to the magnitude of rotational acceleration. Potentially when evaluating other sports such as the NFL where the problem is more often repetitive brain impacts vs. mx where it may be a smaller number of impacts but bigger hits, curious to understand what is the preferred technology to prevent rotational acceleration. For example, if in mx, the key is to dissipate big hits that occur infrequently, that might be a different technology choice than the NFL where the problem is to dissipate many smaller hits.
Curious if Fly or Rheon would chime in or other technical people have additional feedback. I am excited to see these technologies develop, but just trying to apply a bit more analytical thought into which technology is best.
Fly Results:
http://www.wpsstatic.com/miscimages/info/Formula-Benchmark-Data-Testing…
Looking at rotational results:
1) Why were the two speeds chosen...4.2 and 7.1 m/s correspond to 9.3 and 15.8 mph respectively. Seems relatively low when considering typical riding speeds?
2) Looking at the rotational data closer, at 4.2, the Formula was ~ 2nd or 3rd, but then was approximately somewhere around 4th or 5th at 7.1 m/s with not much differentiation between the top 7. With just two data points: 4.2 and 7.1 m/s, seems like the Rheon advantage diminishes/goes away with increased speeds?
3) Given the relatively low and medium low speeds tested, it would be better to characterize how Rheon performs over a more representative speed spectrum. Curious if Rheon is a better technology at lower speeds but then another technology becomes superior as speeds are increased
4) There is more and more research coming up assigning probability of a traumatic brain injury to the magnitude of rotational acceleration. Potentially when evaluating other sports such as the NFL where the problem is more often repetitive brain impacts vs. mx where it may be a smaller number of impacts but bigger hits, curious to understand what is the preferred technology to prevent rotational acceleration. For example, if in mx, the key is to dissipate big hits that occur infrequently, that might be a different technology choice than the NFL where the problem is to dissipate many smaller hits.
Curious if Fly or Rheon would chime in or other technical people have additional feedback. I am excited to see these technologies develop, but just trying to apply a bit more analytical thought into which technology is best.
The speeds used to show data are comical
This tells me that helmet companies are designing things that help at little to no speed - but past X m/s there is nominal difference between different offerings.
(3) Agreed. There is a balance between making sure soft hits don't cause concussions and saving your life in the event of a big hit. We should know where the trade-off is for each helmet.
(4) I agree we deal with a totally different pattern of brain trauma, and obviously should design helmets accordingly.
I think the Shoei rotational system is pretty great. The Bell one seemed a little rudimentary to me. Fox and Fly seem to have technology but I haven't seen it in person yet.
Thread: https://www.vitalmx.com/forums/Moto-Related,20/MTB-Helmet-Crash-Test-Wh…
Helmet rankings: https://www.helmet.beam.vt.edu/bicycle-helmet-ratings.html
Test method: https://vtechworks.lib.vt.edu/bitstream/handle/10919/83760/Bicycle%20ST…
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http://www.ircobi.org/wordpress/downloads/irc18/pdf-files/75.pdf
Also remember its not about how fast your going when you crash, its more about how fast you stop, that is what drives high G loads. My point here is even if you are going 40 if you skid and slowly come to a stop the test speed is actually low for this event as well, however if your going 40, swap up and crash into the face of a jump that stops you in an instant your in for a world of hurt and yeah these test speeds are to low. We unfortunately have seen events like this but they are a bit more rare based on my anecdotal evidence.
To add to that, I believe 6D explained their ideology is to combat low speed impacts that "add up" over time and result in the equivalence of a concussion
In the auto industry crash testing they have a thing called the HIC (Head Injury Criterion) which is the integral of the acceleration over the time of the crash event. The math is a touch more involved than that but in simple terms a long event at low acceleration could be measured just as bad as a very short event at high acceleration. Now this is all measured in 1 event, not consecutively over time in a bunch of crashes.
Brain injurys are a fickle thing and regardless of all this the testing displayed by fly is at least all comparative, meaning at least the same test was ran across the board showing how each stacks up against one another. The key items you want to look at on their plots are both the peak resultant head accelerations and area under the curve. The area under the curve is a simple way to visualize the HIC I mentioned above.
Arguing the test is always valid and honestly is a big part of how the science system works. Just don't throw out the baby with the bathwater.
I ask this after actually looking at the fly report now, wow I should have read that before replying, they actually talk about the HIC, haha. Anyways I ask for whats the proper speed because saying you crashed going 40, 60, or 80mph doesn't mean this impact test is ran at that speed of the bike. The test speed needs to align with the impact speed of your helmet to whatever it impacts. To understand this truly and do it right you'd have to collect data across multiple forms of racing, at multiple skill levels, all the while just waiting for crashes to build a database. Or you setup a crash test dummy like the auto world does and send the bike into crash scenarios.
The point here is to do that is crazy expensive and crazy time consuming. Far more than Fly as a company would be willing to spend. I applaud them for the info they have released but would look to test standard industries to fill in the gap you are asking for. Just the same way the auto world doesn't do their crash testing, it is all done independent. Snell or the DOT could/should be leading this charge and make all the data you are asking for extremely transparent. With them having separation from the manufacture they could show real data across all brands, good and bad, and be somewhat protected from litigation from the company's themselves but also from someone who does crash and hurts themselves.
I think it is fair to highlight their speeds are not representative and to be critical for calling that out doesn't add much value to the conversation. A logical discussion at planning the test matrix should have brought that point up. Given that the rotational tests were performed by Rheon and it is their technology, it is hard not to be a bit skeptical. Given VTech's test rig is essentially the same, I would be curious how their data compares. Also, Rheon's data states that the data presented is the "best" result from each helmet. No mention of variation sample to sample?
For example, medical studies have long shown that death occurs from brain accelerations around 400 G. This has always been the DOT helmet test threshold. ECE and Snell use 275 G as their threshold limit to be more conservative. The engineering question then becomes, at what speed impact can a helmet prevent death? The current answer for motorcycle helmets is around 17 mph. (This is a free-fall drop test, where a dummy torso and head is dropped from a height to impact at this speed, with the helmet slamming into steel head first. 17 mph is reached from a fall of about 10 feet.) Larger, heavier FIA car helmets are slightly better, preventing death (275 G) at 21 mph. The physical limitation is: how large and heavy can the helmet be?
Concussions and traumatic brain injuries- the medical community has not given a clear answer for a threshold when this occurs. What should the acceleration threshold be? I have not seen evidence that any helmet manufacturers agree on this. There have been numerous medical studies suggesting numerous answers. 6D apparently designs to maximize speed impact for 60 G; Leatt for 120 G. Obviously the design impact speed varies with these different thresholds. The new ECE 22.06 standard establishes a "low energy" impact threshold of 180 G acceleration (same for the FIA car helmet standard).
Rotational acceleration is another design challenge.
Clearly, lower acceleration is always better. But engineering a solution to maximize speed at one acceleration threshold will produce a different helmet than maximizing impact at another acceleration threshold. Different helmet designs will be better at different impact speeds. Furthermore, different size/weight heads and different sized helmets will produce different results.
Marketing data doesn't reveal how complicated it really is. How does the helmet perform at different speeds? How many different impact points were tested? Which size/weight head was used?
Leatt publishes their moto helmet tests as well, you could probably cross refence those with the Fly to see how similar their data is.
Pit Row
I see the subject of testing and test numbers come up over and over again. I think what would be of huge benefit is a VA Tech type of star rating system. I've spoken with them about including motorcycle helmets in their testing but got nowhere.
That would leave it to an independent non profit entity to test and rank available helmets. I'ts kinda spendy to buy helmets off the shelf and whack them on the rig, but I think that's what people have been asking for.
The results of testing like that would piss off a lot of manufacturers, but we would all be better informed. It would also push the development of helmets forward as nobody could hide behind charts that came from the marketing department.
Secondly, could not agree more about the value of a VTech star system. Any helmet manufacturer that gets pissed when their helmets performance is publicly disclosed should reflect on why they are protecting that data in the first place.
Interesting that you have some first hand knowledge about the manufacturing side. Like many industries, you get one manufacturer setup with the capability to produce helmets with anti-rotation features and they leave the design details up to the brand but as long as the mfg technology can be leveraged, minimizes investment by the brands to tool a complete helmet up.
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