Charnwood Healthcare Ltd manufacture wheelchair seat cushions, mattresses for beds, hospital trolleys and operation tables and high seat armchairs or nursing chairs

Technical Information

Our Managing Director, Bob McLintic, who also rides a Honda Super Blackbird, decided to investigate the requirement for lightweight motorcyclists' clothing that was not leather based.

On looking closely at other products on the market, it was found that "fully lined jeans" are not actually fully lined. Jeans are typically lined with a pair of shorts with flaps down over the knees. Some are simply patches of aramid sewn into hip and knees areas. These linings are usually stitched to the denim and it has already been agreed that denim will tear open typically with two seconds of impact. So why sew partial linings to denim?

We decided that it was essential that the para-aramid fabric should stay in position during and after the impact and it was necessary to cover all areas not just areas that may be at most risk . We also decided to use Kevlar - the Du-Pont trade marked para-aramid. Kevlar provides excellent resistance to abrasion and is essential equipment for leisure motorcyclists and scooter riders who do not wish to wear leather. The Kevlar we use is woven fabric and breathes and looks rather like cotton fabric.It is five times stronger than steel, weight for weight.. The big advantage of a separate under garment is that it is not restricting your choice of clothing. It is also possible to choose a shirt or long under pants and even a top to bottom one piece garment. K-liners are made to measure. K-liners are special and are manufactured in Britain, at Poole in Dorset.

Testing

We tested the concept by making up a sack from a single layer of our Kevlar fabric and filling it with 20 kilos (44lbs) of sand. This was attached to a tow rope and thrown out of a vehicle at 60 miles per hour. After towing for two hundred yards the sack was unscathed - so we did it again. After this second attempt the test rig was still intact so we decided to test to destruction. After throwing out of a vehicle for the third time, at 60mph, we dragged the test rig the length of the available road. After two thirds of a mile we ran out of safe road and stopped the test. This assembly is still intact!

Our competitors also tested their product. One drags a man along on the seat of his pants at high speed. This is impressive but the most serious aspect of any accident - the impact - is avoided. Another has recognised the need to test for impact but only tested with a sack filled with fabric off-cuts. There is insufficient weight for a "true" test. Our test involves using an equivalent to the weight of a man's lower body.

Design

We looked at the "competition" who all advertise "fully lined" jeans. In fact we found none that are fully lined. Most consist of a pair of shorts with a flap that comes down over the knees. They also sew the lining into the jeans using conventional threads. If the original jeans are likely to split open within seconds of hitting the road, why rely on the jeans to keep the lining in place? We decided not to skimp on the Kevlar and make a full liner that will "stand alone" as a garment in its own right. This inner garment is assembled using Kevlar thread. This liner is then available for use under jeans or any other garments you choose to wear. As fabric alone does not provide impact protection we have incorporated fixings within the liner to carry our CE approved hip, knee and body armour. It is essential the motor cycle or other venture sports clothing provides both abrasion resistance and impact protection. An important aspect of the K-liners design is to provide accurate and firm fixings for the impact protectors. Other products are relying on pouches that maybe position wrongly or are too large thus allowing the impact protector to move away from the high risk area it was designed to protect. Some have no pouch but rely on things like self adhesive hook and loop fastenings that are also inappropriate.

K-liners fabric

Before deciding to use our Kevlar fabric we also looked at other manufacturers' aramid or para-aramid fabrics. Some manufacturers apparently use aramid i.e. a type of Nylon not para-aramid at all! We found that some are knitted others are woven and some are non-wovens with a scrim base. Knitted fabrics are a looser fitting material and also capable of stretching. It is also important to understand the end use. There are many uses including bullet proof vests, chain saw protection and protection against knife attack in prisons. Some para-aramid works by breaking up and clogging up the teeth of the saw or cutter likely to cause injury. Our application is completely different - we do not want the para-aramid to break up and it is essential it stays in place. Para-aramid fabrics that are working by breaking up and clogging the cutter are usually heavier and more bulky for that reason. We needed a fabric that was lightweight, low in bulk but still five times stronger than steel.

Disadvantages?

To get the best from your K-liners you need to know the downside of para-aramid fabrics. These are not usually detailed in most sales brochures or anywhere else for that matter! Maybe the most important point is that aramids lose their strength in ultra violet light. Yes sunlight! Typical figures are a fifty per cent strength loss after exposure to three months of sunshine. Potentially a problem, that is why we use the Kevlar as a liner. When you wash your K-liners ideally dry indoors. Used in this application the potential problem is easily avoided. Other interesting facts: para-aramid cannot be dyed, it cannot therefore leach dyes. Cutting and sewing is obviously a problem without specialised tools.