Piston rings and things

As Allan Henshaw-Allcock restores a 1961 Fordson Dexta we took a closer look at the piston rings and crankshaft bearings.

This particular tractor (sn 957E 83479, family-owned from new) had been stood for an amazing 40 years and luckily most of this time was indoors. Most of the nuts and bolts had rust visible so the good old WD-40 was brought out, liberally sprayed and allowed to soak in overnight.

Before stripping, the first thing Allan did was to get the tractor to run. With the injectors and starter motor removed the engine was turned over via the crankshaft, tightening up as one of the pistons came to the top of its stroke.

More 'loosening fluid' was poured into the indirect injector ports and by using a crowbar on the flywheel teeth through the starter motor hole, the engine was turned back and forth. Allan marked the tight spot position with chalk on the flywheel before turning in the opposite direction. Persistence pays off and within 30 minutes the engine could be rotated by the crankshaft pulley (by hand) with relative ease.

The wiring was checked, the injectors replaced, a battery fitted and with enough diesel in the tank for a start-up it soon fired into life. Although it ran smoothly the blue smoke indicated the piston rings were probably stuck and would be replaced (along with a standard set of bearings to the big-ends of the con rods).

I'm not dwelling too much on the engine in this article, just the removal and refitting of the piston rings, bearings and refitting of the complete pistons/rods into the cylinders, which only needed a light hone to polish up, the bores being parallel. One thing I will mention though, the diesel tank! On the engine's initial start-up, no problem, until later on in the restoration when the tank was sandblasted and it was discovered the bottom of the tank resembled a colander, with several holes large enough to stick a pencil through (Fig A) - Fordson spray painting had held fuel all this time!

Piston rings

Along with cylinder head and bottom gasket sets, new standard size piston ring sets (the pistons were in good condition) and big-end bearings were ordered from a company called Agriline Products Ltd (01527 579111) or visit their website on www.agrilineproducts.com. Not wanting to preach too much free publicity but all the ordered parts were on the doorstep early the following morning and all fitted perfectly!

Bearing Big End Early Porsche

A The perforated underside of the diesel tank after sand blasting!

B With the cylinder head removed.

C Definitely a case of new shell bearings for the big end.

D Look carefully and you can see a blocked oil hole in No.5 bottom oil control ring.

E All three piston assemblies ready for a strip down, clean and inspection.

F The honing stones used to 'glaze bust' the cylinders.

G The bottom oil control ring is now in place.

Honing Stones For Cylinder

A The perforated underside of the diesel tank after sand blasting!

B With the cylinder head removed.

C Definitely a case of new shell bearings for the big end.

D Look carefully and you can see a blocked oil hole in No.5 bottom oil control ring.

E All three piston assemblies ready for a strip down, clean and inspection.

F The honing stones used to 'glaze bust' the cylinders.

G The bottom oil control ring is now in place.

With the engine removed, drained of oil and on the bench both the cylinder head (Fig B) and sump were removed to allow piston and con rod removal.

Each piston was marked with a small indent stamped on the crown *, ** and *** relating to the numbers already stamped on the bottom of the con rod caps. Allan stamped them facing the front of the engine (radiator end).

The big-end locknuts were removed followed by the end caps. Using the wooden shaft end of a 21b hammer the con rods were in turn tapped up into the cylinders until the pistons could be gripped and pulled out from the top. With the engine laid on its side rotate the crank until the piston to be removed was at the top of its stroke, keeping hammer tapping to a minimum!

The crank was in good order and measuring with a micrometer showed no ovality or scoring here, so no need to remove and grind. There was no play in the gudgeon pin and the circlips were in good order so these were left in place.

The Dexta uses a 3-144 Perkins three-cylinder engine, each flat-topped piston having five ring grooves.

Counting Nol as the top ring and No5 as the bottom:

Nol Single compression ring No2 Single compression ring No3 Four laminate compression rings No4 Top oil control ring (above gudgeon pin) No5 Bottom oil control ring (below gudgeon pin) As predicted the rings were tight and a piston ring extractor was used to remove them. This tool prises open each ring allowing it to be safely removed without damage to the piston or ring, and without the ring flying off. The rings in No3 and No4 grooves can be removed with a small screwdriver.

Once the rings and big-end bearing shells (Fig C) were removed the task of cleaning the carbon deposits from the piston ring grooves can begin. If you don't have a proper tool break one of the old rings in two, using the unbroken end as the scraper BUT NOT A SCREWDRIVER! Do make sure all the carbon is removed.

With the compression rings finished, next come the oil scraper (control) ring grooves, which sit either side of the gudgeon pin. Clean out in the same way with an old broken ring BUT do check the oil drain holes (Fig D) around the circumference of the piston in the scraper ring grooves. These can become blocked up with sludge and carbon. If still blocked after the grooves and piston has been cleaned, use a small twist drill (by hand) and turn in each of the holes until clean.

Glaze busting

Once all the pistons (and con rods) were scraped and washed clean they were laid out and stored ready for re-assembly (Fig E). Because we were only fitting new rings we gave each of the cylinders a good 'glaze busting' (Fig F). This, as it says, busts the glazing on the cylinder bores and will allow the new rings to 'bed in' much quicker.

Now to start fitting the new rings to the pistons; start with No5 (the bottom oil control ring (Fig G) and work upwards, but do check all rings as we did for any marked "TOP" and this is the way it should be positioned on the piston, facing the top! Z)

Piston Oil Control Rings

Workshop

H The bottom ring sits snugly in the expander ready for fitting.

I Easing a new ring Into position using the Piston Ring Expander.

J Fitting one of the four laminates into No.3

compression ring groove. Note the spring expander and two lower laminate rings already in place.

K All done! Check the ring gaps are all opposite each other.

L With the piston ring compression tool fitted, this piston assembly is ready to go into the cylinder.

M Tap the piston into the cylinder with the wooden end of a hammer.

H The bottom ring sits snugly in the expander ready for fitting.

I Easing a new ring Into position using the Piston Ring Expander.

J Fitting one of the four laminates into No.3

compression ring groove. Note the spring expander and two lower laminate rings already in place.

K All done! Check the ring gaps are all opposite each other.

L With the piston ring compression tool fitted, this piston assembly is ready to go into the cylinder.

M Tap the piston into the cylinder with the wooden end of a hammer.

This is often the case with the top compression ring (which can be a chrome ring). Fitting these 'marked' rings upside-down can result in the rings becoming an oil pump.

Also, to make sure, we tried the new rings into the cylinder bores to check they were the correct size and there was a gap of around 18 to 20 thousandths of an inch (0.018in -0.020in). I have heard of this important check being ignored at great expense. Another point, worth spending a 'few bob' on are the big end locking nuts. As the saying goes, the life of a self-locking nut is like a split-pin; Use only once and replace with new!

With engine oil squirted and rubbed into the grooves fit the ring into the tool (Fig H), open and slide into position over the piston (Fig I). Same with No4. The middle groove (No3) is also a compression ring comprising of four fine laminations and the spring expander ring (Fig J).

Hold each ring with thumbs and fingertips until the open ends meet. This will make the ring either face up or down slightly (concave or convex). The rings should be fitted concave face up, convex up, concave up, convex up.

Oil Expander Ring DownOil Expander Ring DownClassic Tractor Fever

No2 and Nol rings are single cast-iron rings, completing the set. The original workshop manual states Nol (top) piston ring is chrome! Cast iron is brittle and if no tool is available and you are using nimble fingers to open the rings before fitting don't get 'too macho' or they'll break!

Using a small screwdriver turn the rings so that the gap on No2 ring is 180 degrees (opposite) the gap on Nol ring. Do the same with the oil control rings (Nos 4 and 5). With the four l/32in thick rings that make up No3 (compression) ring just adjust the gap so that no two are the same (eg with spring expander ring at an imaginary 12-o-clock, twist the rings to two, four, eight and 10 o'clock) Fig K.

Piston ring clamp

Another tool is now used, the piston ring clamp, resembling a baked bean tin with a clamp around it. Slide the clamp over the piston to cover all the rings and tighten up with the screw (Fig L).

Squirt more oil into the cylinder and locate the con rod in the correct cylinder (see indent on top of piston) and turn into position. Using the wooden end of a two-pound hammer tap lightly, watching the piston slide through the clamp and into the cylinder (Fig M). Stop to check the con rod is coming towards the crank and squirt a bit more oil onto the shell bearing before tapping the piston again (Fig N).

Now for the con rod bearing, which comes in two halves (or shells). The groove in the con rod is machined so that the tab of the shell will sit inside without the need for force, lightly pressing with the finger will do.

Counterweights

Nol & No3 journals of the crankshaft have counterweights bolted in position (Fig 0) and we had a bit of 'manoeuvring' of the big ends into position. Once the piston was tapped fully in and the shell bearing was touching the big-end bearing on the crank, the lower shell-bearing half was fitted into its cap and slid into place along the two retainer bolts (Fig P). Once happy the big-end self-lock nuts (use new ones) were tightened to a torque of 65-70 Ib-ft (unplated) or 55-60 Ib-ft (cadmium plated nuts).

Once all three piston assemblies were fitted into place (Fig Q) and torqued up, the engine (still on its side) was rotated by hand and no tight spots were encountered. Once Allan was happy, a clean cloth was placed on the bench and the block was placed upside-down, the oil pump/pipes and filter gauze to be fitted next, before the crankshaft and sump gaskets (Fig R) followed by the sump.

One tip here, remove the sump cover plate before fitting the sump (Fig S), as the oil pump suction pipe may need 'tweaking' into centre before this cover (with a new gasket) can be fitted!

In writing this article I am indebted to Allan Henshaw-Allcock and Malcolm Rainthorpe for their contributions. ■

Tractor CounterweightsFordson Major Bigend Stuck

N As the piston is lightly tapped into the cylinder, guide the big end of the piston rod onto the crankshaft big end journal.

0 One of the crankshaft counterweights.

P Fitting the big end cap.

Q One of the big end caps, fitted and tightened with the torque spanner.

R Sump gasket in position, Allan fits one of the big end cork gasket seals.

S Remove the sump cover plate before refitting the sump.

N As the piston is lightly tapped into the cylinder, guide the big end of the piston rod onto the crankshaft big end journal.

0 One of the crankshaft counterweights.

P Fitting the big end cap.

Q One of the big end caps, fitted and tightened with the torque spanner.

R Sump gasket in position, Allan fits one of the big end cork gasket seals.

S Remove the sump cover plate before refitting the sump.

Jo Roberts

Words & Pictures Jo Roberts

Now residing near Llanrwst, with Bob Roberts, who bought it in 2010, this crawler has been in North Wales for at least the last 35 years.

There she blows! Firing up the Bristol.

Have tracks will travel

Jo Roberts finds a vintage tractor that laughs in the face of snow and ice.

There she blows! Firing up the Bristol.

As we all know, little vintage tractors are generally no better at performing in the snow and ice than your granny's Mini Metro. However there's one type of vintage machine that laughs in the face of sheets of ice and kicks the pants off the packed down snow, and that machine is, of course, the crawler. Having metal tracks is like owning the ultimate set of snow chains, and suddenly when you are axle deep in snow, a top speed of walking pace doesn't seem quite so agonisingly slow after all!

To me, the first flush of snow is always something of a novelty, but after a week it starts to become tedious. De-frosting pipes, carrying water out to animals and trying to keep the fire plied with logs is the down side. Plus, having two small children who are tired of the freezing hands and feet that you get from being out in the snow means that I'm somewhat trapped in the house. Cabin fever sets in, and I start to understand why people who live in snowy countries tend to drink lashings of hard liquor on a daily basis. Because there really is nothing else to do.

But I'm pleased to report that, with two small children in tow, I decided it would be much better option to persuade their Uncle Bob to get his crawler out for a bit of fun, rather than to crack open the Christmas liquor at 11.30 of a morning. Bob tried to put me off by saying that the crawler was under a big tarpaulin and that it would be a

Curious crawler facts

Down in the cockpit of the Bristol it's a bit of a tight squeeze.

• It is not clear who invented the first bulldozer, but we do know that the bulldozer blade was being used long before tractors of any kind were invented. A pair of mules would be harnessed into a frame, and at the front of the frame was a blade. The mules would push the blade into a pile of material, in order to spread it out, and then would have to back up to repeat the performance.

• Tracks were also used before tractors - in 1825 a British Government patent was awarded to an early 'crawler'. This implement had tracks which replaced the wheels on an ordinary horse drawn cart, enabling it to move over soft ground without sinking in.

• Apparently the largest self propelled tracked vehicle in the world is the Crawler Transporter that is used by NASA to transport their spacecraft from the assembly building to the launch areas. Think your crawler is heavy on fuel? This Crawler Transporter uses 150 gallons of diesel per mile! With a mass of almost 3000 tonnes this might be the largest self propelled crawler, but it is not the largest crawler in the world either. The German 'Bagger (Excavator) 288' is larger, at 13,500 tonnes. However, the Bagger 288 requires electricity to run, so can't be described as self propelled. This monster is used for excavating coal, and is like a factory in itself.

Perkins 144

This Bristol PD has a Perkins P3 (144) diesel engine, a three-speed gearbox, and a top speed of around 5mph.

Power Fordson Major 1961

Pete's County Crawler, and in the rear, its cousin the Fordson Major.

bit of a hassle to get it out, and brrr wasn't it cold... But I wasn't going to be deterred that easily, and after a bit more persuasion it wasn't long before our peaceful, snowy little hamlet was shaken into life with a mighty roar and a blast of diesel fumes from the little dozer.

Blade

We decided to do a bit of unofficial snow-ploughing with the blade of the Bristol crawler. I doubt that this was in any way helpful to anyone, but it certainly kept us occupied on an otherwise uneventful day. I also got to have a go on Bob's crawler, and unlike the only other crawler I've ever driven this one would actually turn right as well as left, which was handy on a narrow lane. I like the feeling you get from being on a crawler, the feeling that it really is well and truly stuck to the ground. I can understand how people who have ploughed huge steep slopes with these machines would far rather be on a hillside with a crawler than with a four-wheel drive tractor. That low centre of gravity really helps, as does the feeling of weight that goes with even a relatively small crawler like Bob's Bristol. So yes, I do like tracks. I like the substantial, invincible feeling that they give, and the way they travel, clickety-clack, centipede-like, over the ground. What I don't much like is the way that all turns are made in series of straight lines, rather than a gently arc of a steering wheel. Z)

This Bristol PD has a Perkins P3 (144) diesel engine, a three-speed gearbox, and a top speed of around 5mph.

"It wasn't long before our peaceful, snowy little hamlet was shaken into life with a mighty roar and a blast of diesel fumes from the little dozer/'

Pete's County Crawler, and in the rear, its cousin the Fordson Major.

Bristol Crawler

This Bristol PD Angledozer is thought to date from 1962-63. Originally it would have been fitted with a cab, but that has long since rotted away.

Fordson Dexta CabAntique Fordson Tractors Snow
Making tracks; although the County Crawler didn't break up the ice completely, it did make some big cuts into It.

Certainly on a narrow lane, you have to keep using the clutch and brake to correct the vehicle, which seems fiddly somehow. With a wheel, steering is almost an unconscious action; you hardly know you are doing it. Yet on the crawler I found myself thinking, shall I bear left now, or can I get away with going straight for another couple of metres? I suspect though, that if you drove nothing else, then 'steering with sticks' would soon become second nature just like steering with a steering wheel is. One of my other brothers, Pete, also owns a crawler. His is a County, and because his is one of those crawlers which will, at the moment, only turn one way, I didn't ask for a go on it.

Call me a wimp but if I'm having a go on a machine for the first time and that 'go' is on a steep icy lane, where stopping might be difficult, then I always think it's nice to at least be able to steer, but maybe that's just me being fussy. The steering issue, or rather the lack of steering is only caused by a damaged brake-band. But of course if you can work around these problems, then why get around to mending them?

Uncomfortable

Another thing that Pete hasn't quite got around to sorting out is the seat. In short there isn't one. There is nothing between the driver's backside and the uncomfortable looking metalwork where the seat used to be, except for an old piece of damp, folded up rag. I'm sure there are people who would pay good money for such a tortuous experience on a cold day, but I'm not one of them. In any case, it was better that this County crawler was driven by someone who actually knew what they were doing (i.e not me), as it had some work to do. It had to tow a Land Rover and trailer up the steep icy lane, up to a flat place where it could gain some traction.

After much roaring and black smoke we were on our way, with the Land Rover tied on the rear. I got into position on the steepest part of the hill, with my camera at the ready, secretly hoping to see a bit of slipping, sliding and some more roaring, but no. The crawler kept a steady pull all the way up, without so much as a moment's hesitation. Pete managed to steer enough to keep it on the lane, and later, when unladen and on the way back down the steep icy hill to Pete's house, the crawler held its ground no messing.

No stranger

Pete's County crawler is no stranger to steep hills. The crawler's previous owner bought it in order to plough steep land. As we all know during the wartime years we needed to make good use of every acre of land, and many places that were previously thought to be too steep and inaccessible to cultivate did get cultivated by crawler tractors and trailer ploughs. Of course this all happened long before this tractor's time, but a couple of decades ago there was a spell of renewed interest in cultivating those hard to get to places. Farmers who had rough and unproductive land, like steep hillsides and high heaths, were awarded grants for cultivating these

Llanrwst Tractors
Smoky County! Some nice healthy diesel fumes as the tractor fires up.

"If you had a good crawler and nerves of steel, there was a fair bit of work to be had."

Bristol crawlers

Bristol crawlers were made from 1930 to 1970. During this time Bristol Tractors Ltd had several different owners and several different factory premises. By 1970 however, crawlers were becoming less popular, with contractors tending to prefer the wheeled JCBs and with farmers making use of the new four-wheel drive tractors. As a result of this decline in popularity, Bristol sold out to Marshall Fowler, and the Bristol Taurus (the last of the Bristol crawlers) was re-badged as the Track Marshall 1100. The Bristol Sough Bridge Works' factory, situated in Earby closed its doors in 1971.

areas. Suddenly crawlers, and those who could drive them, were in demand. If you had a good crawler and nerves of steel, there was a fair bit of work to be had. But the government changes its mind every so often, and these days many farmers are being paid not to cultivate their land. However, with both of these crawlers living in the foothills of Snowdonia there is certainly no shortage of steep slopes in this area, so it might be the case that before long one or both of these crawlers might be seen ploughing a place where no wheeled tractor would dare to tread... If so, I shall be there with my camera. ■

What was once fluffy white snow has become packed down into some seriously hard ice, so Pete helps a friend over the worst of It by towing his Land Rover and trailer out for him.

Foto Land Rover 5685696 Tractores

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