Two Piece Frame

“One of the best and (apparently) simplest features of the Tomcat is its frame separation system, better known at Tomcat HQ as the Quick Release.”

“It’s one of my very oldest features, first appearing on trike No 3 for Kevin White. Kev was a wheelchair user with Williams Syndrome and was getting overweight, so my newly invented Carer Control system seemed just the answer to his mum and dad. Needless to say they wanted a transportable trike, so some kind of dismantling system was going to be required.

I didn’t want a folding frame, because even when folded – trikes are big, clumsy and no lighter to handle. Nor did I want people struggling with spanners to take a Tomcat apart, so a frame latching system of some kind was required and to make it user friendly I wanted it to be quick – very quick.

As an engineer, I always maintain it’s simple to design something complicated, and very complicated to design something simple, and never was that truer than the Tomcat Quick Release Frame.

Here were the requirements at the start of the project.

> It must be childproof
> It must be accidental operation proof
> It must have no wobble at all when assembled
> It must use no tools
> It must be very quick to operate
> It must be impossible to assemble incorrectly
> It must be collision proof
> It must not damage surrounding paintwork during assembly
> It must be utterly reliable
> It must be quick and easy to operate
> Nothing must topple over or injure during assembly.

It was a tall order at that time, because I was still marine engineering and this special needs trike lark, was just a hobby, so everything had to be handmade and I couldn’t design for industrial processes that would have made life easier. I soon began to realise I had a really tricky problem on my hands.

I sketched about 50 different design ideas, drew up about 10 of them in CAD which I was fortunately quite competent with, and prototyped seven systems in my workshop. Bear in mind that the design of the quick release was dictating the frame design to a degree, so this had to be done in tandem. Looking back it was a nightmare but an intriguing, fascinating, frustrating nightmare.

All the while Anita, Graham and Kevin waited patiently just to get a Carer Controlled trike like Tom’s. It turned up 10 months later and Kevin used his own legs to propel himself along for the first time. Their new trike came apart in seconds thanks to its quick release and I was very pleased with myself for the engineering, but I could see the trike meant far, far more to Anita and Graham. It was quite an emotional event and I will never forget it.

I realised that what I’d conquered as an engineering challenge, had touched and changed their lives and it dawned upon me that if I took this hobby any further, I must do so with honesty and integrity, because here were people entrusting me with the most precious thing in their lives.

I only built one trike to Kevin’s design, but it was a start. The system that replaced it was still handmade but when we moved to Gloucester with much higher overheads it was too slow to build and we were losing £70 on each trike. Something radical had to be done and so I designed the system we use today. You can see it on the accompanying video.

It is a far better system because the component parts are precise and identical, mostly using laser technology in their manufacture. It has a lot of parts, but it is utterly reliable.

It looks easy on screen – and it is easy when you get used to it – but it takes a strictly ordered procedure to take it apart for safety reasons. It takes two hands, which do two different jobs in a set sequence, otherwise it will not operate. In effect it takes the deliberate intervention of an adult to separate a Tomcat and that is just as it should be when you are dealing with child safety.

When we did the redesign I realised the precision and robustness of the new system would have another bonus. As all systems are identical, any upper frame will assemble with any lower frame and that happy fact allowed me to create the trailer trike which relies upon the precision interchangeability of Quick Releasing assembly’s to work. You can also watch the trailer trike conversion on video.

I’m proud of the Quick Release system, not just for its speed and user friendliness, but because it has been utterly reliable over that last seven years and that gives families the confidence to put it in the car and get kids out in the countryside for a bit of fun in the open air.”

Bob Griffin