Vintage thing No.149 - Perkins powered Trojans

This is just like the model I had but with more paint remaining. 

Many years ago, at a secondhand toy sale at school, I bought two Dinky Toy model vans. One was a rather sorry looking Morris Commercial J type van in the livery of the GPO and the other was a cheeky Trojan 15cwt Dunlop van. They got played to pieces. The Morris Commercial looked thin and underfed. The Trojan looked much more robust.

In the undergrowth at Tinker's Park

I was reminded of these two model vans when I stumbled across a scanned image the other day of the remains of a Trojan van. I had found this relic in the bushes at a show at Tinker's Park, near Hadlow Down in East Sussex, in or around 1990. There were many other interesting things in the undergrowth and the only means of identifying it was by the maker's plate on the bulkhead. Only once I'd found that, did I know what it was and that a model of it had brought me so much pleasure as a child. I photographed it as a memorial. It was beyond redemption so it was a melancholic meeting, like seeing an old friend with a terminal disease, but it was comforting to think that the great god Dinky had immortalised it already.

The Trojan and Morris-Commercial vans were rivals. 

The Morris Commercial J type van had a sad face

The Morris-Commercial J van had a sidevalve engine of an entirely conventional design borrowed from the Morris Oxford. With a bore and stroke of 73.5 x 87mm to give 1476cc, it was a bit of a doorstop compared with the glamorous supercharged Trojan and only had a three speed gearbox. It was rated at 10cwt payload and looked sad to the boyish me because of the shape of the grille. It's only claim to fame was that one was blown up by the daleks in a Dr Who feature film starring Peter Cushing as the good Doctor, before he went over to The Dark Side.

The Trojan 15 cwt started out in 1947 with the kind of weirdly wonderful two-stroke engines for which the marque was already infamous. Technically a pair of split singles, many people referred to them as having four cylinders because they have four pistons. Actually, they have six pistons, because two other pots are used to supercharge the two split single cylinders. 

The original unblown engines without the extra pumping cylinders powered the Trojan cars and the utility vans favoured by Brooke Bond tea. Subsequent, forward control vans, christened the Trojan Senior (VT No.97), used the same engine until World War 2.

A Trojan 15cwt wearing spats. This is the early type of snout.

Of course, I didn't know that the Trojan 15cwt was supercharged back then, as I clocked up all those miles with it in the sandpit. If I had known, I would have liked it even more. Some 40 years later, I found a sectional drawing of the blown two-stroke engine and, having learnt more about it as VT No.4, I am still quite impressed but not for reasons of speed or power.

 With a bore and stroke of 65.5 x 88mm, the capacity of the power cylinders was a nominal 1186cc, since the offset cylinder axes vary the strokes slightly.

Nominal is a posh word for roughly. Traction engines were often rated in nominal horsepower, such as 8 nhp, but by present day standards that is a meaningless term. An 8 nhp engine was more powerful than 6 nhp design but not as beefy as a 12 nhp.

I was sold on the Trojan van when I had my Dinky Toy

So what sort of nominal output did a blown Trojan put out?

Like to hazard a guess? Need more technical info about the blower?

The two compressor cylinders measured 92.6 mm and, again, had an 88 mm stroke, giving a swept volume of 1293cc and 9% displacement margin over the cylinders they fed. All the conrods were the same length and interchangeable and the two pumping cylinders were air-cooled, while the – for want of a better description – combustion cylinders were water-cooled. Also, the pumping pistons were cast iron while the combustion cylinders were aluminium alloy.

There was a single transfer pipe and twinned inlet ports for each set of pumping and burning cylinders. Number 1 charging cylinder supplied the number 2 pair of power cylinders.  Automatic cage valves, which operated a bit like reed valves on yer two-stroke Yamahas and Suzukis in the seventies, fed the compressor cylinders through either an an SU 2H or a Zenith 30VEH carburettor.

It all sounds impressive to me so imagine my surprise when I saw a power curve with no more than 24 bhp at about 2,200rpm. That’s less than the sickly-looking Morris-Commercial J sidevalve mill, which pumped out a heady 40.5 bhp at 4,200rpm.

The Trojan’s torque curve is commendably flat, though peaking at 70 lb ft at 1,200rpm.

According to my Ian Allan book of Preserved Buses by Keith A Jenkinson, a 1955 Trojan DT Public Service Coach of this type has been preserved. The 13 seta Strachans coachwork looks a little overwhelming for the chassis but I'm glad it survives. They only made 3.

But wait – there was a big block, supercharged Trojan that came along in 1953. This had a bore of 68.55mm for a heady nominal (that word again) capacity of 1297cc and a slightly redesigned snout as immortalised in the Dinky Toy. Compression ratio was up from 5.2:1 to 5.8:1 so how many horsepower would Dunlop delivery drivers have had to play with?

I don’t think anybody noticed much difference, nominally. I haven’t been able to find out and initially had a sneaking suspicion this modification was done in the name of economy but apparently they were quite thirsty! Gutless and thirsty – maybe they were durable. Let’s be nice. Unfortunately, they were unpleasant to drive, by some accounts, with beam axles, semi-elliptic springs and a 3 speed box. 

Quoting from The Commercial Vehicle User's Journal of October 1946, "The backbone form of the box-section pressed-steel chassis frame ha striangulated bracing to give torsional rigidity." The magazine appluaded the "excellence of the progressive springing" and said that it held the road well. "The whole chassis is of robust build and it is quite evident that is has not been built down to a price, which, however, will be competitive."

I strongly suspect that the controls "fell easily to hand." Can you hear me rolling my eyes?

The Morris J-type became the JB-type in 1957 when it received the 1489cc B series engine and four speed box. 

I really like the clean no nonsense lines of the Trojan 25 cwt van and the attractive graphic design of the adverts are so much of their time, too.

Trojan, though, had already gone one better. The new 1953 snout could also accommodate a Perkins P3 diesel and more often than not proudly displayed the Perkins badge on the front. Perkins engines were classics of their time, what Mr J.L.B. Matekoni, proprietor of Tlokweng Road Speedy Motors, would call “good loyal diesels”. With a no nonsense 3” bore and a 5” stroke, they nominally sound like a steam locomotive. In metric they would measure 88.9 x 127mm for 2365cc.

In 1958 a bigger and heavier chassis rated at 20 or 25cwt came along with the Perkins P4, 41 bhp and a 4 speed box. Same bore and stroke but the extra pot takes them out to 3153cc. Still not a fireball but they would run for ever.

Rural bus or luxury coach? Judging by the seats, this is a rural bus. Let's go on a mystery tour in the country. Or, dare I say it, convert it into a camper

By now known as the Trojan DT and with forward control an option, they were not popular and production ceased in 1959. The blown two stroke had bowed out two years earlier.

The Marley tile company were one of the few firms to favour them and Trojan offered their own bodywork for vans and buses alike. The passenger vehicles were often described as personnel carriers, which sounds somewhere more down market than a bus. Strachans built 3 coaches on the DT chassis but they didn’t have such good proportions as the in house Trojan coachwork. 

The Marley Tiles Trojans remind me of Kryten from Red Dwarf (Photo : Pinterest)

So you might expect me to be somewhat disillusioned by the supercharged Trojan. Upstaged by the worried looking Morris-Commercial J-type van and blown into the weeds by the Perkins P3 – an engine quite at home in a grey Fergie tractor – I still find them technically interesting. I can’t help but wonder what sort of performance a four cylinder or (twin split single!) two stroke engine with a pair of pumping cylinders might produce if designed for power and not economy.

I reckon the development story of these engines would make an interesting tale but all the protagonists are probably long gone now. Trojan’s original designer, Leslie Hounsfield, left trojan in 1933 and sunsequently made a name for himself before the war as the designer of folding camp beds for the army. He died in 1957 at the age of 80 so who was behind the supercharged Trojan engine?

A throw away remark on the website of the Trojan Trust says that this was the first installation of a Perkins P3 engine in a light commercial vehicle and that Perkins needed some persuading by Trojan. I’d like to know more about this pioneering move. Why did Perkins need persuading and how were they talked round?

This 1961 Perkins powered Trojan bodied 13 seater coach ferried passengers between the Assembly Rooms and the Pump Room in Bath. Photo C L Caddy

I also find the designs of the later forward control models very attractive. The hot rodder in me – the one drawn to supercharged engines – likes the idea of a performance version, maybe a camper van based on one of the 25 cwt DT types. Or the Trojan bodied bus body like Baa-Baa, the late model version that plied between the Assembly and Pump Rooms in Bath.

I have heard of a Commer PB motor caravan being fitted with Porcshe 928 running gear. Probably it was a case of fitting the Commer to the Porsche drivetrain, so why not a Trojan?