Many wheelchair users employ their hands and wrists as the power sources to propel their chairs. But, over time, the motion causes repetitive strain injuries and can also result in compression of internal organs. This means users generally avoid any travel of significant distance in their wheelchairs. Now, Northampton-based Willgo Wheelchairs has developed a system that allows the users to venture further from home by drawing on a novel transmission system, as company owner, Andy Brown explains.
"The chair can be used as normal around the home or the office, but then in seconds the transmission can be engaged and this allows the chair to be powered for longer journeys."
Switching to the transmission system causes the handles to rise automatically to the correct position to enable the drive to be engaged. Braking and steering is carried out by action on the Hope hydraulic disc brakes - the controls for which are also located at the handles. In addition, by utilising a one-way clutch, the transmission has an automatic anti-roll-back feature - a very useful safety characteristic.
"The ergonomics are such that wheelchair users of all ages find the system particularly easy to use and there is now an enjoyment factor," says Mr Brown. "Users are now able to go to the shops, travel off road and engage in activities that have previously been difficult or impossible in their normal chairs. Willgo has developed this concept in association with leading companies in the field of transmissions and race wheelchairs. Our design offers a realistic alternative to electric assist wheelchairs and provides the user with the opportunity to further improve independence."
The lightweight design means that, wherever possible, adhesives are preferred over mechanical fixing methods. With the assistance of specialists from Henkel (makers of Loctite products), Willgo has developed a technique for gluing the lightweight clutch into the nylon pulley wheels. This not only produces a lightweight design, but also generates great strength.
The method involves the use of Emery cloth on the contact surfaces of the clutch and wheel, then degreasing with acetone. The nylon contact surface is treated with Loctite 770 primer before two beads of Loctite 480 adhesive are applied to the pulley wheel and one bead to the clutch. This cyanoacrylate instant adhesive is a black, rubber-toughened grade that is especially suitable for applications where high peel strength is required and/or shock loads are present.
The clutch is pressed into the pulley wheel and excess adhesive wiped away with acetone. Within seconds the bond is curing and inside a few minutes the transmission can be operated. If the clutch ever needs to be removed this is easily achieved by steaming the joint to over 80°C, and pressing out the component. Where nuts and bolts are used on the wheelchair, a Loctite threadlocker is applied to ensure vibration does not cause them to work loose.
"With a user in a chair for upwards of fourteen hours a day - and with the ability for the off-road use - there can be quite a lot of stress on the threaded fasteners,' explains Mr Brown. 'But by using a threadlocker, we can be sure vital parts will not come apart.'
Loctite 248 semi-solid 'stick' anaerobic adhesive is used for this threadlocking operation. This is a medium strength anaerobic that is effective on all types of metal threaded fasteners - and is recommended for use where disassembly with hand tools is required for servicing. Another Loctite adhesive is used to secure the aluminium handle tube to the stainless steel handle tang. This is achieved by means of a secure press fit and an application of Loctite 9461 Hysol resin - a toughened, two part adhesive, suitable for applications requiring gap filling and high peel strength. It is suitable for bonding dissimilar substrates like GRP, SMC and composites.
"Not only do all these adhesives work - and work well," continues Mr Brown, "but the service I get from the sales engineer has been extremely helpful. We are a small team and assistance like that is invaluable.'
But Willgo has not found that kind of help forthcoming from other sources.
Mr Brown knew his ideas for this form of personal transport were good, but getting others to see the potential didn't prove easy. After a two-year period of knocking on doors and filing paperwork for grants and awards, he decided that the only way to proceed was to find the money himself.
He learned of the government DTI Small Firms Loan Guarantee Scheme that backs bank loans up to 75% and with this, together with funds from two small investors, he managed to raise the initial £35,000 that enabled the project to start.
"Needing to keep costs down, I decided to work from home and turned a back room into an office, and a small lock up garage into a workshop, and it was there that the first prototypes were built," Mr Brown recalls. He developed contacts with businesses involved with subcontracting engineering work and eventually found a small group of interested companies that helped make the Willgo Wheelchair a reality.
"One of the problems was that some companies saw the idea and tried to get their hands on it. It seems that if you have a bright idea it can produce the best in some people, while in others it brings out the worst."
Mr Brown was able to raise further funds along the way, and over £100,000 has now gone into the project. He is planning a move into business premises in Northampton - but just as significant - to start manufacturing in Canada and Poland. He is now not only developing the latest version of Willgo, but also further transmission developments, which will be incorporated into bicycles and tricycles for both wheelchair users and able persons.
"The project is unstoppable now," he says. "And it all started from a back room office and a lock up garage".