Anyone using the HANS device part 2

[logician]

OK, I'm starting a new thread, as the old one got really long. Here's a link to the old thread that has lots of good information in it:

Anyone using the HANS device?

Here is some new information to report:

Has anyone else read the two SAE papers, 2002-01-3304 and
2002-01-3306, cited by Isaac as proof of the performance of their
device? I have just finished reading them. Executive summary:
a) the Isaac paper shows the device to be at a very early stage in its
development, b) the data presented for Isaac is minimal, and not on
par with the throughness of the data presented for HANS, Hutchins, and
D-Cel, and c) the data presented for Isaac does not appear to support
their marketing pitch.

Here are links to the SAE page from which you can download copies of the
reports yourself:

http://www.sae.org/servlets/productDetail?PROD_TYP=PAPER&PROD_CD=2002-01-3304
http://www.sae.org/servlets/productDetail?PROD_TYP=PAPER&PROD_CD=2002-01-3306

The first paper (2002-01-3004) is by John Melvin, et al, and it
presents 11 data sets, 3 for each of Hutchens, D-Cel, and HANS
devices, and 2 for the baseline without any device. The report
presents neck tension/compression and bending moment (both polarities)
in two dimensions for each of the data sets, and also head excursion
for a 30 degree angle 50G impact. The data sets include measurements
for both new and used HANS and Hutchens devices. The HANS device that
was tested was the 20RE model, the one that I have, and the one
appropriate for production car seating.

The figures reported in the paper for neck load are indeed exactly the
numbers presented in the HANS glossy -- 5100, 868, 4000, 3971, for
baseline, HANS, Hutchens, and D-Cel devices. As you might expect,
there is a variation in the measurements, and these figures are
averages of the three data sets for each case. I tried to correlate
these numbers with the marketing data for Hutchins and D-Cel, but
their marketing material doesn't actually quote any numbers -- only
uncalibrated graphs of Hutchens against "other device".

The second paper (2002-01-3306) is by Greg Baker, and it reports on
the development of Isaac. It explains the theory behind Isaac, the
results of three tests, and the refinement of the Isaac design after
each of the first two tests.

The first Isaac test measured a tensile neck load of +2500N/-3500N
(compare to 868N for HANS). However, the mount on the helmet broke.
The Isaac design was modified (read the paper for details), and a
second test was run that generated neck load of +1400N/-2200N. Again
the Isaac device broke. Again the design was refined, and the third
test measured +1330N/-1250N, this time without mechanical failure.

Unlike the Paper by Melvin, the Isaac paper does not report on the
rearward neck shear force -Fx (whiplash?), the bending moments, or the
head excursion. The Hutchins and D-Cel devices exhibit relatively
high -Fx measurements around 2000N compared to HANS value of 237. The
injury threshold for -Fx is 3100N, so this is an important measurement
in addition to neck tension, Fz. It is notable that only one
measurement was reported for Isaac in its final configuration,
compared to the three data sets for each device that the Melvin report
contained.

I compared the numbers in the Isaac paper against their marketing
material. The Isaac glossy chart shows a Neck load for their device
of 200 lbs, or 890N. This is much lower than the 1330N value reported
in the SAE paper. I am curious why there is a difference.

As an engineer, I am concerned about the maturity of the Isaac,
considering that the design and its parameters were just being
developed circa 2002. The refinement done during testing included
adjusting the damping factor in addition to fixing the strength of the
components. Too high a damping factor, and your neck gets crushed
instead of stretched.

So what are the characteristics of the version of Isaac that is being
sold to club racers? Are they the same as what was tested? What
about the other test data: neck shear forces, bending moments, or head
excursion? How does Isaac rate for these important measurements?

I will be the first to say that I am not an expert on head and neck
restraints. I have only been researching the subject for six months.
Perhaps there are subtleties in the papers that are not evident to an
engineer outside the field. If so, I hope that someone with greater
knowledge will explain. Also, my report is not to say that Isaac may
not be a good product on par with others, but only to say that the
evidence cited for its performance is minimal, and further that it
does not actually support the marketing pitch. If there is better
evidence available, I would like to get about it. Finally, as an
engineer, I am painfully aware of how the best designs in theory often
fall short of their promise upon testing. So I value test results
and, better yet, product maturity highly.

If you have problems obtaining those SAE reports, PM me and I'll see
what I can do to help.

-Juan

[addictionMS]

Juan,

Just a quick note to tell you I am a keen lurker on this thread and really value the effort and time you are putting in on this. I am learning a lot due to you efforts.

thanks again

Keep up the fight

Jim

[gbaker]

Juan,

You once posted, “Engineers with partial knowledge scare me. I should know, I'm an engineer…” So far you have only partial knowledge.

When I get a chance I will fill in some of the blanks on the original thread—I won’t post here. In the meantime, this is still correct: http://www.isaacdirect.com/html/chart. I’ll explain later.