Vintage Thing No.41 - the Cattley 7

One of my fellow marshals on the Launceston Trial turned up in this delightful little car. Warin Kelly has owned it for years and say the best thing about owning a special is that you can add to its specialness. This car is one of those that invite closer inspection. And the more I looked the more I saw that I liked about it.

In recognition of its original builder, Warin calls it the Cattley 7 and, although he's owned it for some time now, it was originally built in the mid-fifties. Mr Cattley made the body himself out of aluminium on an ash frame and when Warin first got it the powerplant was the usual 747cc sidevalve Austin motor.

Curious, isn't it, that sometimes the numbers 747 make you think of jumbo jets and at other times of tiny willing 4 pot motors, revving far higher than their designer ever intended, thanks to ingenious backyard tuning by an enthusiastic but knowledgeable amateur?

However, just like anyone else, Warin wanted more power and found a 598cc overhead valve Reliant engine that had been used in 750 Motor Club racing.

There is a link between Austin 7 engines and Reliant's own design of powerplant. In 1938, Reliant renounced the JAP V-twins they were using in their girder forked 3-wheeler vans and adopted the Austin 7 engine. I don't know if the end of production was foreseen by Reliant or not but when Austin 7 production finished in 1939, Reliant began production of something very much like it in their own factory. Some say there was total parts interchangeability between the two brands of engine.

Reliant later moved the valves upstairs for greater efficiency and changed to aluminium instead of cast iron in the interests of weight saving - always a matter of concern when you have to meet an 8cwt weight limit to qualify for the cheaper road tax that a 3-wheeler enjoys in Britain.

The 598cc engine that Warin originally got hold off sounds to me like quite a motor. With a bore and stroke of 56mm x 61mm, it would rev to 8,500 rpm. 750 Motor Club racers could wring over 50bhp from these all alloy engines in full race form. (Well, obviously they weren't all aluminium but the head and block were and that's what makes them so appealing - "they don't weigh hardly anything" as we say round these parts.)

The only trouble was, all that power was delivered in the wrong place. Fortunately the Reliant motor grew by degrees to 848cc – 60.5mm x 61mm (sometimes quoted as 60.96mm but that’s the more exact metric equivalent of 2.4 inches) gave 701cc, an extra 2mm on the bore gave 748cc (compare this to 56mm x 76mm for the Austin 7) and then a longer stroke finally evolved into the 62.5mm x 69.1mm 848cc big daddy engine. Compression ratios also increased from 8.5:1 to 9.5:1 and power as standard ended up at 40 bhp (29kW) with 46 lf ft (62Nm) of torque.

These days Warin uses an 848cc version on a single SU carb and a tubular exhaust manifold complete with a reliant gearbox. It’s an interesting alternative to souping up the original Austin 7 engine, which often involves supercharging for a really good output. I mentioned some blown examples I’d seen before and he grinned and said one gearbox he had in the Cattley 7 was so worn everyone thought the whining noise was a blower. Naturally aspirated Austin 7s often use Phoenix cranks these days but they’re quite expensive. They can’t arf rev, though.

I like the colour of this engine, too. It reminds me of the egg shell blue I used to paint my Airfix kits and looks sort of aeronautically technical.

Warin said there are four bolts that mount the engine in the frame but the chassis flexes so much the fourth one is never done up tight – it’s there more as a helpful guide, really, politely suggesting where the engine should be but not getting too wound up if it wanders around a bit in the engine bay. Do them all up tight and you run the risk of breaking the ally mounting points on the block.

To make the Cattley 7 even more suitable for its intended purpose of trialling, he fitted the lowest back axle A7 ratio he could find, namely that from one those little vans they used to do with an 8/45 crown wheel and pinion (5.625 final drive ratio). An 850 Reliant Kitten used a 3.23 back axle and boasted a top speed of 80 mph. Warin reckons anything over 50 mph is a bit cruel on the Cattley 7.

It’s had an illustrious trialling history, though, beating works Morgans and many other more powerful machinery. It doesn’t get out so much these days because of the roughness of modern classic trials sections. Warin had to re-shape his rear mudguards the last time he entered.

He gave me a lift in it after we’d finished marshalling and it was great fun blasting through the mud in Lew Wood. Because of the narrow track, the Cattley 7 is always sliding into and out of one set of wheel ruts, which can slow you down but makes for more of a challenge. Leg room for me as a 6’ 1” passenger was okay but my knees were wedged up against the dashboard so a long journey would probably have been out of the question.

Warin has been in touch with Mr Cattley’s son who remembers his father bending sheets of ally round drainpipes and banisters when he built the car. He also said that his dad had no time at all for Lockheed brakes but thought the world of Girling, the other big name in brakes in the British motor industry. He asked for their advice in designing the hydraulic braking system – essentially using parts from an Austin Big 7.

Girling sent an engineer rep who stayed with the Cattley family while he worked on the car. He’d brought a pair of master cylinders with him, expecting Mr Cattley to opt for a hydraulic clutch, but he was quite happy with a cable arrangement. So, instead of taking the surplus master cylinder back with him, he fitted a dual circuit system. If you look closely in this picture you can see their fluid reservoirs snuggling up to each othe rin teh engine bay. I’ve no idea when this was all fitted but it seems that the Cattley 7 was highly advanced in the braking department for its day.