Motorcycle armor

Motorcycle armor comes in a variety of forms, from traditional yellow foam to high-tech compounds capable of absorbing large amounts of energy. In its basic form an armored jacket will include shoulder and elbow armor, and many jackets can have an optional back protector added too. Trousers should include hip and knee protection, and sometimes a coccyx protector too.

Types of motorcycle armor

Foam

This armour is either closed cell or open-cell foam and in various densities all the way up to a fairly hard foam used in helmets. Hard foams absorb impact/shock by destructive decomposition so they can only be used to protect for one incident and must be replaced. Soft foams offer little protection with close-cell foams providing a bit more protection than open-cell foams.

Memory foam

Of foam type armors, memory-foam armor achieves a higher level of impact absorption compared to open/closed-cell types above. Memory-foam rebounds slowly after compression. It is a very dense foam.

Silicone

These are gel type impact/shock absorbers. They are produced in various densities and generally used close to the body for comfort.

Hard plastic

Hard armour usually consists of a hard plastic and is designed to resist abrasive and puncture injuries. Hard armour generally is used in conjunction with some impact absorbing foam or other material on the inner surfaces facing the body. This is because hard armour by itself does not provide impact/shock absorption qualities.

Viscoelastic

The use of viscoelastic materials in motorcycle armor has allowed for hand (glove) elbow, knee, shoulder, tail-bone, and back armor to be manufactured in a soft and pliable state at rest. Upon the introduction of shock the armor adopts extremely rigid and protective properties. Examples of this armor are SAS-TEC, SW, D3O, Knox MicroLock, EXO-TEC and TF armor. They are currently being used in jackets, trousers and suits by manufacturers such as KOMINE, REV'IT!, Firstgear, BMW Apparel, Fieldsheer, Scorpion, Rukka, Klim, Aerostich, Worse for Wear, and Hideout Leather.

Viscoelastic armor is soft and body-forming until it is impacted. At impact it reacts quickly to form a rigid mass. D3O armor hardens edge-to-edge. Sas-Tec armor is considered to be a progressive reactive armor in that it hardens to a degree sufficient to counter the force. The material prevents trauma to the human body by three methods:

  1. Shock Absorption: Material absorbs impact energy through phase change (hardening).
  2. Shock Delay: Material delays the transmittance of some shock to the human body over a longer period of time.
  3. Dissipation: Impacts are dissipated over larger areas of the body.

Viscoelastic armor is able to achieve a higher level of shock/impact reducing benefits with more comfort and less bulk than traditional hard armor - foam laminate solutions. Hybrid armor is layered with hard shell outer materials. European standard EN-1621 is used to rate the effectiveness of armor. In this standard, a 5 kg flat impactor impacts the armor at a speed of 4.47 m/s (energy 5x4,47x4,47/2=50 J "Joules"). 50 J of energy is roughly equivalent to dropping a 1 kg mass from a height of 5m (E=mGH). Sensors measure how much force is transmitted through the armor, its peak force in kilo-newtons (kN), and its period (how long it took the force to be transmitted). If the force transmitted through the armor is less than 35 kN then the armor (all armor except back) can attain an EN-1621-1 rating.[1] Standard also includes other factors such as temperature stability and coverage area. The back protection standard is EN-1621-2. That standard rating is based on that energy being less than 18 kN (EN-1621-2 Level 1) or less than 9 kN (EN-1621-2 Level 2).[2]

EN1621-1 Armor for All Body Parts (Except Back/Spine)

There are two European standards covering "motorcyclists' protective clothing against mechanical impact": EN1621-1 and EN1621-2. EN1621-1 covers any body part protection except back/spine. EN1621-2 covers back/spine. There are updates to the standards from time to time and so the year the update comes out is added as a suffix to the standard such as EN1621-1:1997[1] and EN 1621-2:2003.[2] Both standards assess the performance of protective devices by measuring the force transmitted through it when impacted by a falling mass.

EN1621-1 assesses armor designed to protect the shoulder, elbow and forearm, hip, tail-bone, knee and lower leg regions. The test apparatus consists of a mass of 5 kg with a 40 mm x 30 mm striking face, dropped onto the sample mounted on top of a 50 mm radius hemispherical dome. The anvil is further mounted onto a load cell, allowing a measurement to be made of the force transmitted through the protector. The kinetic energy of the falling mass at impact must not exceed 50 J.

A protector subjected to this test method is deemed to conform to this standard if the average transmitted force of nine tests is:

  • less than 35 kN (EN1621-1 CE Level 1), with no single test result exceeding 50 kN, and
  • less than 20 kN (EN1621-1 CE Level 2)

As well as the two levels of protection, armor may optionally be certified to work in extreme heat (above 40 °C) or extreme cold. Armor that passes these test will have a T+ or T- marking respectively.

EN1621-2 assesses armor designed to protect the back/spine. It is a more stringent standard allowing no more than 18 kN of force to be transmitted to attain Level 1 protection (EN-1621-2 CE Level 1). Armor that allows less than 9 kN of force to be transmitted can attain a Level 2 protection (EN-1621-2 CE Level 2). See section below for more information.

Motorcycle airbags are covered by a different standard (EN 1621-4).

EN1621-2 Back/Spine Protective Armor
Backpack for motorcyclists of the soft type ("CB" Central Back Protector) and approved level 2

European Standard EN 1621-2:2003[2] defines two levels of performance for CE approved back protectors. The test apparatus and procedure is similar to that of EN 1621-1:1997,[1] but with a different impactor and anvil configuration. The impactor is a rounded triangular faced prism, of length 160 mm, base 50 mm, height 30.8 mm and radius 12.5 mm. The anvil is a radiused cylinder, with its axis orientated to the direction of impact, of height 190 mm, diameter 100 mm and rounded end radius 150 mm. When tested to the procedure defined in the standard, the two levels of performance are:

  • Level 1 protectors: The average peak force recorded below the anvil in the tests shall be below 18 kN, and no single value shall exceed 24 kN.
  • Level 2 protectors: The average peak force recorded below the anvil in the tests shall be below 9 kN, and no single value shall exceed 12 kN.[2]

Back protectors are often not included in the standard complement of armor although many jackets allow a back protector to be installed.

Because of the more delicate nature of the spinal column, back protectors require that lower levels of force be transmitted. The introduction to EN 1621-2 states that approximately 13% of motorcyclists injured in road accidents have an injury to this back region. However, only 0.8% of the injured riders suffer a fracture of the spine and less than 0.2% of injured riders have a serious back injury resulting in neurological damage. This is supported by evidence from the MAIDS Report (2004), the most comprehensive in-depth data currently available for Powered Two-Wheelers (PTWs) accidents in Europe.

A systematic review – by Ekmejian et al in 2016 – found that motorcycle back protectors were ineffective.[3] Further work (by Afquir et al in 2019) agreed, and found that “the design of back protectors should be reconsidered to better protect riders from what is referred to as compression fractures (craniocaudal force), which remain the primary form of fracture regardless of the rider’s characteristics, based on the data analysed.”[4]

Specifications
Standard Transmitted force Level Body Parts
EN1621-1 < 35 Kn Level 1 All Body Parts (Except Back/Spine)
EN1621-1 < 20 Kn Level 2 All Body Parts (Except Back/Spine)
EN1621-2 < 18 Kn Level 1 Back/Spine
EN1621-2 < 9 Kn Level 2 Back/Spine

Limitations of current standards

Research has revealed limitations of the current standard of motorcycle armour. De Rome et al (2011) found that motorcycle armour was not associated with less risk of fractures.[5] Work by Albanese et al (2017) could explain why: “The allowable transmitted force of EN 1621-1 may be too high to effectively reduce the probability of impact injury. This is not surprising, given human tolerance levels that are reported in the literature […] A reduction in the maximum force limit would improve rider protection and appears feasible”. [6] Additionally, Meredeth et al (2019) found that shoulder and knee armour need different levels of impact protection. And the CE standard for armour only reduced transmitted force to the shoulder by around 8% (± 5%). They concluded that: “distinct differences in injury protection performance observed between knee and shoulder impact protection indicate that there may be a need for different performance criteria for impact protection designated to protect different body regions.”[7]


Main benefit of armor

Liz de Rome et al undertook a cross-sectional study of motorcycle protective clothing and armor. They found there was no association between wearing armor and fracture risk. However, wearing armor was associated with reduced injury for another reason: it provided additional abrasion resistance, which was significant because of the high rate of failure of the clothing itself. The report found that: "A substantial proportion of motorcycle designed gloves (25.7%), jackets (29.7%) and pants (28.1%) were assessed to have failed due to material damage in the crash."[8]

See also

References
  1. EN Standards 1621-1:1997
  2. EN Standards 1621-2:2003
  3. Afquir S, Melot A, Ndiaye A, Hammad E, Martin JL, Arnoux PJ. Descriptive analysis of the effect of back protector on the prevention of vertebral and thoracolumbar injuries in serious motorcycle accident. Accid Anal Prev. 2020 Feb;135:105331. doi: 10.1016/j.aap.2019.105331. Epub 2019 Nov 18.
  4. A systematic review on the effectiveness of back protectors for motorcyclists. Ekmejian R, Sarrami P, Naylor JM, Harris IA. Scand J Trauma Resusc Emerg Med. 2016 Oct 4;24(1):115. doi: 10.1186/s13049-016-0307-3.
  5. Liz de Rome et al. Motorcycle protective clothing: Protection from injury or just the weather? Accident Analysis & Prevention. Volume 43, Issue 6, November 2011, Pages 1893-1900.
  6. Bianca Albanese et al. Energy Attenuation Performance of Impact Protection Worn by Motorcyclists in Real-World Crashes. Traffic Inj Prev. 2017 May 29;18(sup1):S116-S121. doi: 0.1080/15389588.2017.1311014.
  7. L Meredith et al. Assessing the Performance of Motorcyclists’ Impact Protectors in Simulated ATD Knee and Shoulder Impacts. Traffic Inj Prev. 2019;20(2):169-173. doi: 10.1080/15389588.2018.1540867.
  8. de Rome L, Ivers R, Fitzharris M, Du W, Haworth N, Heritier S, Richardson D. Motorcycle protective clothing: protection from injury or just the weather? Accid Anal Prev. 2011 Nov;43(6):1893-1900. doi: 10.1016/j.aap.2011.04.027. Epub 2011 May 28.
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