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The PedSALi Project

Article summary
The aim of the PedSALi project was to develop a prototype vehicle bumper, to meet EU requirements, for new vehicles to be pedestrian friendly.
Our project partners were Dow Chemicals, Automotive Division and the University of Manchester. Unfortunately, the University research was mismanaged and the project was wound up without producing any meaningful results.
The legislation should have been effective from 2005 onwards. However, apart from PedSALi there was no obvious solution "the conflict of stiffness problem" (described below), so the EU requirements were withdrawn in 2003.

1 The historical description of PedSALi, before the project was
wound up

A bumper which meets the EU test requirements could be made by filling a traditional plastic bumper facia or shell with soft foam. However, designing a bumper to pass a single type of laboratory test, using a dummy leg, is not the same as designing a bumper which will give a high degree of impact protection, for a wide range of pedestrian sizes, in real life accidents. One of the big advantages that SALi offers, compared with existing soft foams is that, it is a so-called "smart" material, which can change its impact energy absorbing properties, depending on the type of impact it is cushioning.

A successful PedSALi project bumper will pass the EU tests, and also offer a higher degree of accident protection, for a range of pedestrian sizes, from small children to large adults. A correctly designed SALi filled bumper, will also be more effective in protecting the vehicle in low speed impacts with other vehicles and street furniture, such as concrete posts. As a bonus, it will offer improved protection in high speed vehicle accidents.

The cost of injuries: The financial cost of pedestrian/cyclist injuries in the UK alone, in 2003, is estimated to be £3,045 million by the Department for Transport.

The cost of the PedSALi project to the British taxpayer: The PedSALi project has received £256k UK government funding under the Foresight Vehicle programme. This is less than one percent of the annual UK cost of pedestrian & cyclist accidents.

The bulk of the funding, £212k, pays for university research, to help us design the most effective type of bumper, taking into account size, weight, recycling and cost considerations.

The cost of SALi filled bumpers Due to their relative complexity, SALi filled bumpers are likely to be more expensive than soft foam filled bumpers, for small production runs. However, if we can develop our product ahead of the competition and create demand for the improved benefits of SALi filled bumpers, we should be able to move into mass production, driving the price difference down.

A brief explanation of how a SALi filled package can vary its stiffness, to cater for different types of impact

Fig. 1 A 13.4 kg mass, impacting at 40 km/h, as specified for the EU dummy leg impact tests would "see" the SALi filled package as a wide, soft cushion, with SALi to the sides of the impact zone absorbing impact energy. At higher impact velocities, energy absorption by viscous damping would increase, effectively, stiffening the SALi.

This would provide "smart" pedestrian protection at velocities in excess of the EU requirements.

Fig. 2. A more massive object, representing another vehicle bumper, or item of street furniture, such as a concrete bollard, would "see" the SALi filled package as a narrow, stiff cushion. The rate at which the SALi material is crushed will be higher than for the dummy leg impact opposite. So although the impact velocity is lower in this second example, the contribution of viscous damping, and effective bumper stiffness, will be higher. The SALi would stiffen as velocity increased, providing "smart" passenger protection.

Incorporating this variable stiffness concept into a pedestrian friendly car bumper.

There are several design possibilities for doing this. Figures 3 and 4 below illustrate one approach we will be exploring.

Fig. 3. The SALi filled bumper acts in a similar manner to soft foam filled bumper, during a lower leg impact. However, compared with a foam filling, it offers a significant injury reduction advantage; the bumper is softer for a small child's leg impact, compared with the stiffness offered during a large adult's leg impact.

Fig. 4. The same SALi filled bumper acts in a similar manner to a bumper filled with a very stiff foam, during impacts with objects that are wider than the bone tissue in a human leg. This will reduce vehicle damage in low speed impacts and keep insurance claim costs down.

2 After the project was wound up

Auto Express article on the collapse of the PedSALi project

Max Glaskin, Auto Express, 7 September 2005, pages 44-48

A PEDESTRIAN-friendly bumper which can also improve occupant safety may sound too good to be true - but for retired physics teacher Bill Courtney from Altrincham, Cheshire, it has been a Holy Grail for 19 long, hard years. He's invested £140,000 over 19 years and needs to spend more, although development has come to a halt. Bill invented a bumper which is filled with a thick Shock Absorbing Liquid (SALi). He claims that at low speeds it would be soft enough not to hurt legs, yet provides sufficient protection to cope with bigger accidents. Back when pedestrian protection legislation for vehicles was first being considered, international firm Dow Chemicals was interested in selling SALi to car manufacturers. "I applied for funding to prove the material would do the job," Bill said. He and the project won government grants worth more than £300,000, and scientists at Manchester University started testing it. He even patented his invention, but gradually lost faith in the way the research was going. In the end, Dow went off the idea, which meant Bill missed the window of opportunity for selling it. And as he's now fallen out with the research team, too, it looks as though his bumpers may never see the light of day. "It's quite sad, and the whole experience has had a bad effect on my health," he explained. "I'm mentally and physically worn-out, and need to get the project off the ground in the next year or will have to abandon it altogether. I just can't afford to keep renewing the international patents."

Fig. 5. In spite of warnings from Cheshire Innovation, the published results were limited to tests using high stretch packaging. Comparable results using low stretch packaging were withheld from publication.

Cheshire Innovation Comment: It is important to emphasise that the problems were caused by a tiny number of researchers at the former University of Manchester, prior to its amalgamation with UMIST. These researchers did not appear to recognise the serious implications of publishing fake research, relating to incorrectly packaged SALi. In contrast, there are many excellent engineering researchers at the new University of Manchester. Bill would be happy to work with the new University, developing SALi Technology. This technology has the potential to save lives and reduce brain injuries caused by violent impacts. It would be a humanitarian tragedy if a historical legacy prevented SALi being developed in Manchester.

For further details of the PedSALi problems please contact us. Enquiries from anyone with an interest in an amicable resolution are especially welcome.

Some good news

The PedSALi work is now being done correctly at Cardiff University. Progress is slow, because the work is being done on a shoestring budget, in the form of undergraduate projects. But the quality is excellent. The following paper was presented at an international auto engineering conference in Stuttgart, June 2009.

Other SALi projects: Sassy Hats CrashSALi

For notes on Research, Education and Ethics click

Appendix

The UK Department for Transport description of the PedSALi project appears to have been removed from the Foresight web page. A bitmapped copy of the original page is reproduced below.

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Home > Science and Research > RD > Programmes > DfT - Vehicle Standards and Engineering > (G) Foresight Vehicle > PEDestrian protection using Shock Absorbing LIquid technology (PEDSALI)

DfT Research Database

Project: PEDestrian protection using Shock Absorbing LIquid technology (PEDSALI)

Reference: C3/P35

Last update: 13/10/2003 09:58:29

Objectives

At the end of the project it is anticipated that, using Finite Element techniques, it will be possible to predict the performance characteristics of a SALi based shock-absorbing component. Physical testing be will used to confirm the predicted results and validate the model. The chosen materials will be assessed using FMEA techniques to ensure that any adverse effects, such as toxicity and corrosive properties, are recognised and evaluated.

Description

This highly innovative project is researching a new composite, impact energy absorbing material that can in effect, automatically alter its stiffness, to cope with different types of impact. At present it is being evaluated with respect to the reduction of serious and fatal pedestrian casualties as the result of road accidents, in line with DTLR targets.

The patented material being investigated is a Shock Absorbing Liquid (SALi) which consists of lots of small resilient elastomeric capsules immersed in a matrix liquid and stored in a strong flexible package. Upon impact, all of the capsules are compressed by the matrix liquid and the front face of the package deforms to the shape of the applied load. The compressive stiffness of SALi filled packages increases as the area of applied load is increased. Consequently, a suitable sized package would be soft for a small child’s head impact, but stiff for an adult head impact. If SALi filled packages are integrated into car bumper systems, then the bumpers will be soft for lower leg impacts, but stiff for low speed bumper-to-bumper impacts. This will help to make vehicles safer for pedestrian accidents, while keeping vehicle repair costs low.

The unusual cushioning properties of SALi can be illustrated by comparing its impact absorbing performance with that of a block of elastomeric closed cell foam.

The project is investigating the three parameters that influence the physical characteristics of a SALi filled impact absorber: the matrix liquid, the size and nature of the elastomeric capsules and packaging design.

The matrix liquid acts as a lubricant to facilitate the movement of the capsules and to transmit the hydraulic pressure changes when a load is applied. Additionally the liquid provides viscous damping when the steady state condition is disturbed due to its shear viscosity and bulk viscosity properties.

The capsules can vary from expanded polystyrene beads to bubble packing. The size distribution of the capsules need to be optimised in order minimise the total weight of the impact absorber, without compromising on impact absorbing performance.

The packaging provides a flexible leak-proof envelope to contain the liquid and capsules but, importantly, it must not stretch significantly during load application. Also, the package must not burst open and eject its contents during a violent impact. The size and shape of the package will affect impact energy absorbing performance.

Contractor(s)

University of Manchester
Oxford Road, Manchester, M13 9PL

Cheshire Innovation
17 Vale Road, Timperley, Altrincham, Cheshire, WA15 7TQ
0161 980 5191

Contract details

Cost to the Department: £44,200.00

Actual start date: 01 March 2001

Expected completion date: 30 September 2004

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