Snell Memorial Foundation has one of the most
advanced and busiest helmet testing facilities in the world. Snell's California helmet
testing laboratory is the one of the few in the United States accredited to ISO
17025 by the
American Association for Laboratory Accreditation (A2LA).
Before a helmet can be Snell-certified, it is tested in Snell's state-of-the-art
test facility. Snell technicians conduct a variety of tests to determine the
helmet's performance and ability to stay on the head in different environmental
conditions -- wet, heat, cold. Depending on the application and the standard,
each helmet
must pass all or some of the following tests:
Impact Test
This test involves a series of controlled impacts where a helmet is positioned
on a metal head form and then dropped in a guided fall onto various steel test anvils
(Flat, Hemisphere, Kurbstone, Roll bar, edge or a horseshoe type) which simulate different impact
surfaces. (See below for the picture). The head forms are instrumented with an
accelerometer to measure peak G force or acceleration which is measured in
"G"ravitational units. The impact energy (drop height and mass), or
how hard the helmets are impacted is unique to each standard. However, if in any valid test the peak acceleration
imparted to the head form exceeds 300 G's, the helmet is rejected.
Positional Stability (Roll-Off) Test
A head form is mounted on a stand so that it points face downward at an angle of
135 degrees. The helmet is placed on the head form and the straps and buckles
adjusted to obtain a "best fit". A wire rope is hooked to the rear
edge of the helmet and brought forward so that its free end runs across the
helmet and downward towards the floor. The free end of the rope has a mechanical
stop with a 4 kg weight resting on the stop. The weight is raised to a
prescribed height and dropped onto the stop. The resulting shock places a rotational load on
the helmet. The helmet may be shifted, but must not roll off the head form. Next
the head form is rotated 180 degrees, the helmet adjusted, and tested with the
wire rope hooked to the front edge of the helmet and the test is repeated. As in the first case, the
helmet may be shifted but must not roll off the head form.
Dynamic Retention Test
The
helmet is placed on a head form and the chin strap fastened under a device
approximating the contour of the jaw. The jaw piece is loaded with a 23 kg
weight for approximately one minute. The retention system is tested by
simultaneously removing the 23 kg weight and applying a 38 kg mass in an abrupt
guided fall. The retention system fails if it cannot support the mechanical
loads or if the maximum instantaneous deflection (stretch) of the retention
system exceeds 30 mm. Drop heights for the 38 kg mass are different for each
standard, however the mechanism and failure criteria are similar for other types
of headgear.
Chin Bar Test
The chin bar test applies to full face motorcycle, special application racing
and kart racing helmets. The helmet is affixed to a rigid base with the chin bar facing
upward. A 5 kg weight is dropped through a guided fall to strike the central
portion of the chin bar. Maximum downward deflection of the chin bar must not
exceed the stated distance.
Shell Penetration Test
The shell penetration test applies to motorcycle, special
application racing, kart racing, skiing and equestrian helmets. The helmet is affixed to a rigid base. A 3 kg
sharply pointed striker is dropped in a guided fall onto the helmet from a
prescribed height. The test striker must not penetrate the helmet or even
achieve momentary contact with the head form.
Faceshield Penetration Test
The face shield penetration test applies to full face motorcycle, special
application racing and kart racing helmets. The face shield is affixed to the helmet and
shot along the center line in three separate places with an air rifle using a
sharp soft lead pellet. Pellet speed will be approximately 500 kph. For the both
types of shield the pellet must not penetrate, and for the racing helmet any
resulting "bump" on the inside of the shield must not exceed 2.5 mm.
Flame Resistance Test
The flame resistance test applies to special application racing helmets only.
The test is conducted using a propane flame of approximately 790 degrees
centigrade. The flame is applied to the shell, trim, chin strap and face shield
for a specified number of seconds, and any resulting fire must self extinguish
within a specified time after flame removal. During the whole process the
temperature of the interior lining of the helmet must not exceed 70 degrees
centigrade.
Philosophy and Concepts of Helmet Testing
It is important to realize that a lot of product type testing like helmet
testing does not seek to precisely reproduce real life situations, rather it
attempts to define a set of requirements that is analogous to the types of
situations that might be encountered while engaged in a prescribed activity.
Helmet tests are designed to be repeatable, measurable and include a fixed range
of situations a helmet might reasonably encounter. At this point the
concerns of helmet testing does not include responses of the neck or body as
they react with the head during a crash. It is strictly a measurement of
how a helmet reacts during an event to protect the wearers brain. At Snell
we believe that as technology continues to evolve, so should helmet design and
manufacturing techniques.
Three Basic Types of Testing Programs
- Certification Test
- Official pre-market evaluation for admission to the Foundation's Certification
programs. The manufacturer submits a number of helmet samples, depending on
the helmet type and Snell standard to the Foundation for testing. Snell
technicians at Snell laboratories subject these samples to the most rigorous
testing permitted by the Standard. Any failure on any sample is a cause for
rejection.
Random Sample Test (RST)
- Required testing and evaluation for all certified helmets. The
Foundation acquires helmet test samples directly from stocks of helmets that are meant
for sale or distribution to the general
public, or specific groups of users, usually from retail or distribution sources. The
number of samples we will buy is based on the number of Snell certified helmets the
manufacturer has produced. Snell technicians in Snell laboratories inspect and test each
sample to check that the helmets used by the public
continue to meet the Foundation's high standards. If it is found that
these RST helmets fail to meet the testing criteria, three more samples are
obtained and tested to confirm the findings of the first tests. If any
of these three follow up tests result in failure, the Foundation
first demands that the manufacturer discontinue production of these helmets as
Snell certified products. The Foundation will then continue to investigate
the matter and determine a suitable course of action. These actions
can range from requiring the manufacturer fix the problem and recertify the
helmet, to a complete decertification of the manufacturer's certified product
line. In some cases Snell will require that all Snell decals
distributed to that manufacturer be returned.. This basically
amounts to a full scale recall. Gratefully, this rarely occurs because
of the procedures taken during the certification and Random Sample
Testing.
- More on RST
Prototype Test
- Unofficial evaluation. Manufacturers may submit one or more helmet
samples and request specific tests and test configurations. The Foundation
will not consider prototype test data in evaluation for Certification.
However, manufacturers may find prototype testing useful in product
development.
-
The Foundation has published "The
Implications of M2000 Testing Policy". This document clarifies
the why and what action we take when a helmet fails in the random testing
program. The file is in Adobe TM pdf format, and about 190 KB.
Information for Manufacturers That Wish to Obtain Snell Certification
How to Apply for Certification Testing
- Contact Snell To arrange a test date.
- Complete Pre-testing Information Sheet.
- Request 'Payment Advisory Form' to arrange the payment.
- Send the helmets with Pre-Test Information Sheet to Snell's lab for
testing.
(Forms
and Instructions required for testing - Adobe tm pdf format)
Testing Fee Schedules: Click here or (Current
Price List - Adobe tm pdf format)
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