Tractor heritage, news and features

Big-hearted David

Steve Coombs likes David Browns, and regular readers of Tractor will have seen his very nice 770 we featured last year. He also likes big engines and in fact works with them day to day for his job at Ham Hill Quarries in south Somerset. I should mention that he’s fond of the odd engineering challenge as well. So given all of that, is it any surprise that this modest man from Somerset should shoehorn a 19-litre V12 engine into a DB 1690?

Project

Like many such projects, this one came about almost by accident, or at least, that’s the way Steve tells it now. A friend of his had bought a massive 125 Kva generator set based around a Deutz V12 in a farm sale, and asked Steve to give him a hand, as he couldn’t get it running. Its history was obscure, but Steve thinks the gen set was ex-military and spent some time at the Westland helicopter factory in Yeovil, possibly used to start jet engines.

Whatever it was used for, the Deutz is a big old beast, measuring not much under 20 litres and pumping out 265hp when rated at 2300rpm. As so often with Deutz diesels, it’s air-cooled, and though this one had been built to run a big generator, the basic engine was apparently also used in plant and trucks. What we do know is that this one had hardly been used, made in 1965-66 and being run for only 200 hours since (and they wonder why Britain spends so much on defence). Deutz UK man Jonathan Blades tells me that this is quite common with these standby gen sets, which might only be started every now and then to check that they’re working.

This lack of use explains why the V12 was seized up, which was where Steve came into the story. Fortunately, the trouble was nothing more serious than gunged-up piston rings stuck in the bore, rather than rusted-solid mains or big-ends. Again, according to Jonathan, it’s not uncommon on standby gen set engines, run for short periods without load. “It was quite simple to take apart and put right,” says Steve, thanks largely to the fact that each cylinder has an individual head and barrel – just as well, because the weight of an entire block of six cast-iron cylinders doesn’t bear thinking about.

So the engine was running, but sadly the generator refused to wake up, and eventually the whole lot was offered to Steve. “To cut a long story short,” he says, “I decided to put it in a tractor.” Steven had already been impressed by an International powered by a VM V12, but being a David Brown man, wanted to do the same with a DB. At least getting the gen set back to the workshop was no problem – it was mounted on its own trailer, complete with air brakes, so for anyone with access to an HGV tractor unit, it was just a case of hooking it up and hauling it home.

Cutting & drilling

Then the hard work really began. Fortunately, Steve has an understanding boss who allows him to use the quarry workshop out of hours, so he’d often be in early or working late, with lots of evenings and lunchtimes (‘sandwich in one hand, spanner in the other’). Ham Hill Quarries, incidentally, extract the beautiful golden limestone which gives some villages of south Somerset and north Dorset (not to mention bigger constructions like Sherborne Abbey) a lovely sunset glow, even when there’s no sunset.

By now, Steve had a suitable tractor, in the form of a 1980-ish David Brown 1690, usually powered by a puny (it’s all relative) 103hp 6.2-litre six. What he didn’t want was an immaculate, well cared for machine with one farmer owner from new. The 1690 fitted the bill, because it had been a carnival tractor. In Somerset, carnival tractors don’t just pull the float, they often have the cab and tinwork torn off so that they can be dressed up to match the display, whether it’s a set from Star Trek or Mamma Mia (and I’m only making part of this up).

All very entertaining, but it doesn’t half make a mess of the tractor. To make things worse in this case, the previous owner had blown the engine and a con rod was sticking out of the block. For Steve, of course, this wasn’t a problem, as he wouldn’t be using the original power unit and he did know that the transmission and rear end were in good condition.

The first job with both engine and tractor in the quarry workshop was to make up a bellhousing plate so the engine would bolt directly to the David Brown transmission instead of the generator it was built for.

“The main problem was finding a lathe with a big enough chuck to hold the baseplate,” says Steve. “My nephew works at MetalTech in Chard, and they had a lathe that could carry a 400mm baseplate.” So that was used to turn down the baseplate on the dynamo armature, using a dummy shaft so that it would mate with the David Brown flywheel, allowing Steve to use the original clutch and transmission from there backwards. Lining all of that up was really the crucial stage of the whole project.

Side rails

Once it was clear exactly where the engine needed to be positioned, Steve could make up new side rails and front frame to support it. He points out that David Browns have what amounts to a chassis, the engine supported by thick steel side rails, though these still had to be substantially lengthened and strengthened to contain the big V12. With the engine in place, he made template rails of 3mm steel to bolt in place and check that everything lined up. When it was clear that everything did, the actual rails could be made up of 20mm sheet.

Luckily, Steve has a friend in the steel business who could not only supply the steel but help to drill it to suit. This chap had a big drill with a magnetic base that could be fixed to any surface, enabling holes to be drilled sideways or upside down if necessary, with the drill fixed firmly in place. “With that and special drill tips, he can drill holes anywhere!” Any welding was done by Steve.

What with all the evening and weekend work, plus this specialist help, the tractor was actually running within a few months of starting work in October last year, in time for its first public outing at the Abbey Hill fair in Yeovil in late April. What took time, according to Steve, wasn’t the major engineering job of lining up engine and transmission and getting the V12 bolted in place, but all the detail work that followed. A longer bonnet had to be made up to cover that lengthy engine, a different cab had to be found and refurbished, and the whole lot had to be painted up.

This of course was in standard David Brown colours, the intention being to make the ensemble look as close to factory spec as possible. That is, as close as a V12-engined tractor can look to standard. In fact, if you squint a bit, the 1690 V12 really does look as if it had rolled out of the Meltham Mills works, maybe a circa 1972 prototype to tackle the big John Deeres and Steigers in North America. One thing that helps is the front wheels – with the standard fronts, the tractor would have had a real nose-down attitude, like a dragster, which wasn’t what Steve wanted at all. He found a couple of Massey combine wheels of about the right size.

Fire it up

So does it work? Well the V12 fires up fine from cold, using its own 24-volt system. The starter motor is a massive thing, about the size of a catering tub of marg, if that’s any help in visualising it, and doesn’t appear to have any trouble in turning over 19 litres of Deutz diesel. Despite its size, being air-cooled and having straight-through exhaust pipes, the V12 isn’t that noisy, though certainly very beefy, and you’re left in no doubt that a big machine is grumbling away inside all that red metalwork. The vertical pipes, incidentally, are stainless steel (‘a man in a dairy owed me a favour’) and very nice they look too.

The other surprise is that despite having to cope with more than twice the power they were designed for, the standard transmission and clutch haven’t given a hint of trouble. Probably because the tractor hasn’t been asked to deliver all of that 265hp yet, if it ever is. Steve has no plans to work it hard in the field, or go tractor pulling, which from the point of view of keeping the transmission in one piece, is probably very wise!

In fact, any teething troubles have come from the Deutz heart of this tractor. One of the head gaskets is leaking, though it seals as the engine warms up. At least, with individual heads, changing the gasket won’t be too difficult. The other problem has stemmed from the unit’s previous life as a stationary engine running at constant revs, and the fact that it was left unused for long periods. The rack on the governor is sticky in one position, so at low speed the engine tends to hunt up and down rather than idle evenly. “Sometimes it’s quite smooth,” says Steve, “get it up to 1200rpm and it's fine.”

That’s the sort of thing that should ease up with use, but something that needs more serious attention is the gearing. Steve has fitted bigger 18-4/38 rear tyres to raise it a little, but the tractor is still limited to 15-16mph on the road, and he would really like a genuine 20mph. That means finding a gear specialist who can make up a higher top for the DB’s main gearbox, and Steve has found a couple of candidates, both reasonably local, who could do it.

Of course, there is another way. As mentioned earlier, the Deutz was used in vehicle applications as well as in a stationary role, in which case a different governor upped the max revs from 1800 to 2300rpm. Combine those higher revs with taller gearing, and we could be looking at a 30mph tractor, though this is now a big, heavy machine, which would take some controlling at high speeds. Not to mention the arm and leg it would cost in diesel.

Steve drove the David Brown to its first public outing near Yeovil, a round trip of 12 miles. During that little jaunt, the V12 guzzled 30 litres of fuel, so I don’t think it’ll be tackling any long distance road runs – at least, not unless its owner takes out a second mortgage first.

In fact, the man’s ambitions for his creation are quite modest. This big-hearted DB won’t be going tractor pulling, or hauling a 10-furrow plough. “I might do the jobs I would have done with it as a standard 100hp tractor,” he says, “towing a silage trailer or something, but not anything else. And with the three-point linkage, there’s no reason why it shouldn’t go out and do a day’s work as it would have done originally.”

In the meantime, he’ll be attending local shows in the south-west, where the V12 (if Abbey Hill and the West Bay rally are any guide) will attract a great deal of interest. Which should give its owner a great deal of satisfaction. “Really,” he says, “I just wanted to show that it could be done.”

Words & Pictures Pete Henshaw