Tractor heritage, news and features

Articulate individual

“It is a bit of a cleft stick, every year people expect me to roll something new out for Newark... and each one takes me at least a thousand hours.” John Hayward’s sentiments are understandable; he is the vintage tractor world’s equivalent of an Olympic athlete, every time he succeeds in attaining a new personal best he’s expected to set the bar just a little higher.

It is clear that John enjoys taking the Doe Triple D concept a little further each year. This time he’s built a Triple D based on the Power Major, deleting the complicated hydraulic controls for relaying movement to the front skid unit. “This year though, I had a bit of a head start as the rear section of this machine is the trailed part of the three-engine Doe I built in 2007,” he adds modestly.  Mind you he hasn’t had a year off; far from it, the front unit was what he terms a hedgerow tractor, dragged into the workshop and rebuilt and restored to match its rear half.

Start from scratch

Why not buy a restored Power Major and start with that, it would help the build enormously? Don’t think he hasn’t thought of that option. The trouble is that like most engineers John doesn’t really trust what the last man did. He says that even if he started with a restored machine he’d probably take it all apart again to check the work was to his standard. Better to start from scratch and then he knows what has been done. The rebuild is rigorous; he starts with the block and has it bored for new pistons, drop in a reconditioned crank and rods then make sure that the cylinder head is OK. Essentially by the time the tractor rolls out of the workshop it has a pair of new engines, he’s been right the way through the transmissions too... and the brakes... and invariably they are sitting on new tyres, and, and, and... Restored? New is probably nearer the mark.

As mentioned before the most obvious difference between this and a standard Doe is the gear mechanism, gone are the difficult to bleed master and slave cylinders and the plethora of pipes, instead there is a rod type arrangement.

New controls

At first glance the new controls look very simple in execution but the planning that has gone into them is detailed and clever. Start with the three ‘gear’ levers; each has a different-sized knob, not because these were the only ones in the spares box but to allow the driver to identify each lever by feel in the dark. Then move forward to the slides that allow the length of the rods to change as the front unit rises and falls over uneven ground, each has a slightly different profile so that each male will only slide into its corresponding female and mistakes can’t be made during hurried assembly (not that John ever assembles anything in a hurry).

Next come the universal joints that allow the front skid to pivot. Logic dictates that a single UJ on the centre line would suffice, and indeed it would. However, John doesn’t like the fact that on full lock the joint is almost bound solid, such is the angle it attains. Net, you can’t change gear with any amount of steering lock on. The solution to eliminate this situation is to use a pair of joints placed away from the centre line, these coupled with the sliding joints allow the gear levers to be used no matter what position the machine is in.

Steering hydraulics

The next area to be dealt with was the steering itself. John has been hard at work in two areas here. If you watch a Doe at work, especially with an inexperienced driver at the helm, you will notice that there is a tendency for the operator to over-steer, this is because the hydraulic steer system is very fast and overly sensitive. John figures that there is no need for the steering hydraulics to be this fast acting so he has replaced them with a different type which are not only more modern but also geared to make the Doe less twitchy.

The second modification concerns the steering hydraulics power source. When the Does were first built the regulations dictated that all the systems had to be ‘in control of the driver’ this was interpreted as all the powered systems needing to be from the tractor the driver sat upon, ie the rear one. This meant that when the Does were working, the rear unit’s hydraulics were heavily drawn upon whereas the front unit did nothing to contribute. Considering that weight transfer means that the rear unit always does more than its fair share of work when a Doe is working hard it would make sense that the steering power should be drawn from the more lightly-loaded unit at the front. Today this Doe draws the hydraulic power for its steering from that front unit, which gives an unexpected bonus when all you want to do is move the tractor from one place to another. Merely firing the front unit up is all that is necessary to shuttle from A to B. Of course previously you only had to fire the rear unit up which amounts to the same thing really except that as John points out it is slightly easier on the mechanical components, it being “far easier to pull a piece of string along than push it” as John puts it.

A starting handle clipped to the frame rail of the front unit gives another clue to the wisdom of making the front unit the ‘master’. Previously you were reliant on getting the rear unit fired up to be able to drive the Doe. If the rear battery or starter motor failed, the front unit had to be started and then provided the tractor was in a position where it could be safely driven (don’t forget the steering was reliant on having the rear motor running) the rear unit could theoretically be pull started. With the new
system things are different as John demonstrated. A couple of quick pulls with the starting handle and the front four-cylinder diesel bursts into life. Now the Doe has steering and can be moved safely.

Spoof details

The other refinement is attached to the frame on the opposite side to the starting handle; tanks previously used for hydraulic fluid are now redundant. Instead of removing them, which would have looked wrong, they have been discreetly plumbed into the fuel system to give a little more diesel capacity, a neat and above all practical use of the capacity.

It would take ages to examine every detail change between a period Triple D and this representation of the model; some of them are so clever and subtle that you have to look twice before you realise that they aren’t original, the badge proclaiming Power Major Dual drive is a spoof, but looks dead right doesn’t it?

Detail aside as a whole, how successful has this year’s machine been? Well, it was out at a recent ploughing match and easily coped with a four-furrow reversible plough (thanks to an extra spool valve on the hydraulics) so it obviously performs as it should do. John proclaims himself pleased with what he has achieved and there is no sterner critic of his work, so it must be darned good. You can judge for yourself, as this one is going to be on display at the Newark show so you can pore over it there.

Unwilling or unable to rest on his laurels John is at it again and next year’s project is already lurking in the works. Another Doe-styled tractor, it is going to represent what Doe might have built had their concept continued into the 1980s. Construction of the rear unit is already under way, it’s got a six-cylinder turbocharged and intercooled motor in it and is going to produce around 160hp, add to this the front unit (the specification of which is as yet undecided but it will probably be a circa 100hp four) and we are looking at perhaps the ultimate Doe design. Imagine 260hp and articulated four-wheel drive. I don’t want to go into too much detail and spoil the unveiling next year, but suffice to say that things like the intercoolers will be cleverly incorporated into the overall Doe shape and design so it’s going to look just like it came out of the works in Essex.

As for the rest of it, you will just have to wait until next year.