What I Do In My Spare Time

Over two and a half years, my son and I built a kit car called a Dax Rush.

We travelled in a rented van to Dax's premises, owned by D. J. Sportscars, in Harlow, north of London (unfortunately, the company is no more). Luckily we had picked the correct size van to take the myriad of parts for our future car. We travelled back to Oxford and laid out all the components of the Dax Rush on our garage floor. We stepped back and tried to imagine bolting, glueing, welding, sawing and screwing all the components together into what was to be a car that we could legally drive on roads!

We began the Dax's construction by upturning the chassis and pop-riveting/glueing the bottom aluminium floor panels to it, using an amazing German structural adhesive called Wurth Bond + Seal Power NSF.

Having killed our right and left hands using a manual pop-rivet gun (thinks...?I must install air tools), we flipped the chassis over...

and installed the De Dion rear suspension, with adjustable shocks, fuel tank, Ford differential and rear driveshafts and wheel hubs (from a Sierra donor car - after being cleaned, the parts looked brand new). Also, you can see the Ford steering column, together with a yellow, glass-fibre central gearbox cover and rear internal bodywork below the roll-over bar (I wish all the glass-fibre components had been in carbon-fibre. They would have weighed a quarter of the weight we bolted on to the chassis).

Here are some of the instruction drawings we were working from.

When the yellow glass-fibre side panels had been attached, we began fitting the front suspension and wheel hubs. Having seen other similar car designs to the Dax, such as the Caterham and original Lotus 7, we decided that Peter, the brilliant engineer who designed our car, had produced a much cleaner, simpler and elegant solution for the front suspension. He had also patented a camber compensation system - unfortunately, that added too much to our budget to afford it.

The front nearside suspension.

On the left is a U-shaped, chromed shape which eventually had the front mudguard/wing glued to it... yes, glued to it using the Wurth adhesive. We were assured by Peter, the engineer, the glass-fibre mudguards, as long as their inside and the chrome surfaces were prepared correctly, the Wurth junction would be strong and wouldn't need bolts to keep them on - 11,000 miles later, the mudguards are still attached to Mr Dax! A magnificent glue... It is quite expensive, but... wurth every penny.

Perhaps I could build a plane with it!

Looking down the chassis from the engine bay

A rather confusing view, but it showns the newly installed engine supports to the circle of the front end of the Ford differential. This is a bit of a step backwards in the build sequence since the steering column isn't shown - attached to the two short, diagonal supports - outlined against the yellow inside body component.

Next, we installed a Ford 2-litre Pinto engine.

Yes, I know, it was ancient... but when my son was 17, I didn't want him to kill himself. I designed and fabricated the air filter box from sheet aluminium. There are two air filters because the inside surface of the bonnet scoop is low, and its air inlet had to be in line with them; plus, they gave me the correct air volume for the engine.

Many moons forward and having that cast iron weight at the front of the Dax, and the Pinto possessing a somewhat low-performance character (no exaggeration) - even though Robby had rebuilt it with a racing cam - it strained to accelerate and get up to speed. So... recently, I replaced it with a 2-litre Honda VTEC unit - an?absolutely?superb engine. It has turned the Dax into Mad Dax!

Crane out...

Pinto and gearbox out...

Honda V-Tec in... well, sort of...

So... having spent aeons of time cutting out the old Pinto engine and Ford T9 gearbox supports from the existing chassis, replacing one chassis member that was in the way of the Honda gearbox, then designing, fabricating and welding together a replacement structure to compensate for the cut-out steel tube, then designing, fabricating and welding together two new supports for the Honda engine and its gearbox, then welding them to the chassis... Phew... we were ready to install the engine and gearbox.

But what is VTEC and why have we fallen in love with this amazing system?

VTEC stands for Variable Valve Timing and Lift Electronic Control. This is how it works (courtesy of https://www.honda.co.nz/technology/engine/VTEC/):

Optimising engine breathing: how VTEC works

?An elegant, simple mechanism switching between high and low valve lift- using two cam profiles and two rocker arms per cylinder.

The switch uses hydraulic pressure to push/release the sliding pin, locking/unlocking the middle rocker arm and the other rocker arm. At low engine speeds, the pin is retracted, disengaging the middle rocker arm. The two outside, low-profile cams operate the valves for a low valve lift. Increased hydraulic pressure pushes the pin at higher engine speeds, engaging the middle rocker arm. The valves are operated by the middle, high-profile cam for high valve lift.??

Here is an exploded view of the inlet manifold.

Next came the wiring... if you like spaghetti, you'll love car wiring. What I couldn't understand was that once we had removed the old wiring loom from the donor Ford Sierra, expecting to use it in the Dax, and laid it out on our patio, it looked like the entrails of a large dinosaur. Robby and I stared at it, then went back to the garage... and stared at Mr Dax, then we went back to the Ford loom. We quickly decided that the huge quantity of wiring and associated gubbins in front of us could not fit in the Dax... No way!

So... we took the easy route and paid up for a D J Sportcars Dax loom, which, when we unpacked it, was a third of the size of the Ford Sierra's... but it was going to do the same job!

Anyway, we had fun and games with the wiring, but eventually, everything behaved and worked... even the instruments.

You can see in this photo our posh leather-covered dashboard, even with a glove compartment! I also haven't mentioned that if you have long fingernails, you can file them down on the road/pavement, or motorway/freeway, as you are driving along since the car is so low...

Okay... I'm jumping forward to where we thought the car was finished and ready to be tested, including setting up the biased braking system (I'll explain that later).

We rented a trailer and persuaded the Dax to drive up on to the bed.

You have to realise, we?could not?test the car on public roads - we had no registration document, no MOT (Ministry of Transport Test), no insurance, no vehicle tax, and we were missing the vital piece of signed paper from a government SVA - Single Vehicle Approval test centre, saying we could apply for all of those missing documents.

We had to think sideways - very sideways, about where we could take the Dax and subject him to every test under the sun... and at all speeds...

The thinking caps went on...

The eventual test track surprised even us.

We made a list of possible test tracks, which was very short since we decided it had to be a race track. Unfortunately, having the nearest at the famous Silverstone race track would cost an arm and a leg. So we went back to the drawing board.

I don’t know why I suggested it to Rob, but I put forward phoning up the local British Army base at Abingdon, near Oxford, and asking if we could use their runways as our test tracks! We laughed at the idea, but I thought I would give it a go.

I had the phone in my hand... I was about to phone up the British Army! I punched in the number and held my breath. I explained my case to an army receptionist; he listened politely to my bizarre request and then said, ‘Just a moment, I’m putting you on hold.’ Well, my enthusiasm dropped like a stone, not expecting to get any further, then he came back on the line and declared he was putting me through to the colonel that controlled the base!

The colonel came on the line, and I repeated exactly what I’d explained to his receptionist. Expecting to be quickly shown the door, he asked, ‘... so you want to use our runways to test the kit car you’ve built?’

I simply said, ‘Precisely... if we may?’ He then came back with an enthusiastic, ‘I’m just looking in my diary, and I’ve just remembered it’s a Bank Holiday (a British national holiday) on Monday, so I’m quite willing for you to use the base's taxi ways as much as you want - all day if necessary, but not the runways... they will still be active.’

I sat in my office, sideswiped by the colonel’s agreement to our request and his enormous generosity. I accepted his invitation - We were on!

Before I show you a video of one of our testing sessions with Rob driving the Dax, I want to explain the brake biasing system, which you can see below.

The front and rear brakes are separated, with one hydraulic copper brake pipe connected to a piston, and the other, connected to a second. You will see a threaded rod connecting both pistons. Each end of the pistons has a swivel joint, which is threaded onto the bar. The bar passes through a ball joint in a circular sleeve. By changing the threaded rod's position (L to R) connecting the two pistons, you change the percentage of total pedal force going to the front or back brakes (the lever arm length). Our bias system has to be adjusted via testing on the track; if you are racing, you can adjust it whilst driving, from the cockpit, with a back-and-forth screw system.

The above drawing, courtesy of https://www.stoptech.com/technical-support/technical-white-papers/proportioning-valves, shows the forces from the brake pedal to each front and rear brakes - it is equal with this setup.

Right... Testing!

We arrived with the car covered with a tarpaulin at the main army base gates; four soldiers were on guard, each carrying a fully loaded SA 80 rifle. I explained who we were, and low and behold, we were expected. We went through the gates without the car being searched and directed to the taxi-ways. It was all very simple and efficiently handled. It was a piping hot summer's day, and we cooked beautifully as Robby and I took turns to try and make the Dax take off.

It was a wonderful testing day - one never to be forgotten.

I needed to thank the colonel who had allowed us free rein of the base taxiways for our testing session. What wondered what we could you give a colonel? We plumped for a bottle of good Scotch whisky. There it was on the table... How do I wrap it? We weren't sure if the colonel would appreciate a flowery or cheerful wrapping paper, so we decided on brown paper - very army...

I was with my Rob when we arrived at the army base. I exited my car with my brown-paper-covered parcel and approached four fully-armed soldiers with SA 80 automatic weapons. It passed through my slow brain that I shouldn't be approaching an army base and soldiers with an unidentified brown parcel. I decided to stop and shout to the now slightly agitated servicemen and informed them who I was and what I had in my hand.

I was ordered (in, I must say, a very friendly tone, since they realised who I was, after my shouted explanation) to approach the gates, fully covered by the four soldiers pointing their weapons at me. I reached (slightly reluctantly) the gates and was asked to, as they put it, relinquish the package, which they would take from me and pull apart in the guardroom.

I have to report that it all went well.

A few days later, I received a superb letter from the colonel, thanking me for the whisky; however, he wrote, 'The army does not accept gifts... I will put it in the Christmas raffle.'

So, there we are, one Dax fully tested, one colonel happy with his thank you gift and four soldiers who practised ensuring their base was safe from a brown parcel carrying member of the public.

The government SVA test enabling us to get our valuable Dax vehicle registration document, MOT, vehicle tax and insurance was next...

At an unearthly hour of the morning, we headed for the test centre to avoid rush hour traffic... and the police, since we were extremely nervous and feeling very uncomfortable, we did not have the usual obligatory registration document, MOT (Ministry of Transport Test), insurance, and vehicle tax (unbelievably, we were allowed to do this for the test!! It felt bizarre driving on public roads and naked of any documentation; we had to push this to the back of our minds and concentrate - we couldn't have an accident!!

We went in convoy with a late friend, who had also built another make of kit car at the same time as us, with its bodywork sporting a 'You're not going to miss me!' Kawasaki green.

We travelled without incident to just outside Leighton Buzzard. We arrived at the test centre, which comprised a long building, split into five tests, or as we renamed them... five torture chambers, that our poor Dax had to progress through, being scrutinised to the 'Nth' degree by the government inspectors.

We had been told that the inspectors failed most self-built cars since they had the responsibility to sign off a vehicle as being safe to be driven on public roads (even though we'd been allowed to drive to the test centre with our Dax unapproved!). This knowledge didn't help our conviction we would overcome the eagle 'I'm going to fail you' eyes of the test scrutineer, nor did it help our heart rates, nor our constitutions.

When we constructed the Dax, we had a very detailed SVA - Single Vehicle Approval - 'bible' manual, consisting of the most strict set of construction rules, we knew we had to adhere to, or our Dax would be failed; here are some of its pages:

To help the examiners check that a car had been built to the contents of the SVA bible, they had at their disposal various sizes of aluminium hemispheres and cones fixed to handles. These were brought into contact with the outside and inside of the car. If any Dax components prevented their movement into specific points of contact, these would fail a particular test. For example, these tools were used to check any component within striking distance of a driver or passenger. We even had to round off the right-angled moulding of the horn button on the steering wheel and apply rubber mouldings around the windscreen wipers and wing mirror hexagonal bolt heads and nuts. We had to design and construct covers for the bonnet catches so that anyone standing at the side of the car, between the front and rear wheels, with us travelling at 60 mph, wouldn't get injured...

There were a huge number of rules within the SVA manual that were sensible and ensured a self-built car was safe to be driven on public roads; however, there were crazy anomalies, such as being allowed to have nearly red-hot exhausts pipes emerging from the engine bay and joining on to an exposed exhaust system. It was a strange and conflicting set of strict rules to adhere to; however, we had to construct the car to these procedures to have it passed... which we did; however, it was a close call.

When the Dax emerged from the torture chamber building into the fresh and sunny day, our inspector circled the car like a preying hawk, with his clipboard firmly clamped to his fingertips. He asked with an 'I'm the one in charge of your destiny' smile, 'Now then, what can I fail this car on?' And he was serious... he seemed to want to find something wrong. He circled our Dax, and when he arrived at the back, he excitedly declared, 'Aah, you haven't removed the right-angled edges from the red reflective plates! That's a fail!'

There they were... two small, rectangular plastic reflectors, 3.5 mm in thickness, and yes, I had forgotten to round off the corners... but seriously, SERIOUSLY... he was going to fail the Dax because of that? Assessing his expression... Yes, he was! Luckily, he seemed to be an examiner with a strange sense of humour since as soon as he got his 'pound of flesh', by way of watching us with glee, sticking rubber mouldings around the offending reflectors, he seemed to enthusiastically pass our car, allowing us to obtain our 'pot of gold' - our registration document from the DVLA - the British Driver & Vehicle Licensing Agency.

After leaving the gates of the test centre, and continuing the sensible and logical English traditions, which are openly known to the SVA examiners, all the superfluous and useless rubber moulding additions attached to the Dax for the test, including the specially designed bonnet (hood) catch covers, were removed and never attached to the car again!

So... that's where we are now, 19 years later, and over 12,000 miles added to the clock, with the Dax still looking as good as new and making people smile and ask, 'Is this a Caterham or a Lotus?' We have to answer, with masses of pride, 'No, this is a Dax Rush - it is much better designed than a Caterham or Lotus'... and we believe this since our bright yellow Mr Dax always drives like a dream and brings out a huge smile on our faces and whoever sees it.

I hope you have enjoyed our Dax Rush journey.

Peter