Torque setting method

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Originally Posted by JDNSW

I remember many years ago a friend (mechanic) in Roma telling me that when he was an apprentice the garage he worked for got the job of doing an engine overhaul on a 1930s Rolls-Royce V12. The factory would not supply parts until the got copies of the mechanic's qualifications. The con-rods had to be sent to England to be remetalled, with the bearings reamed to fit the supplied journal measurements. He remembered that the engine would not turn until the bearing caps were torqued to exactly the specified figures (individual figures for each separate bolt!). It then turned easily.

The days when not only could graziers afford to keep and run this sort of car, but when rural garages would take on anything. (Probably talking about the early fifties)

John

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That would be the Phantom III V12 from the late thirties. A very complex and troublesome engine.

Rolls Royce chronicler, Peter Pugh, described it as "too large and heavy to be popular as an owner-drivers car", and "with no major component common to any other car, the Phantom III stood no chance of being profitable. On the quality front it was clear that the Phantom III had been launched too early in its development".

Sir Arthur Sidgreaves, Managing Director, reported after a tour of the USA "Not only are we not progressing, but we are definitely going back. In other words we are being surpassed by the Americans in particular respect to those features on which our name and reputation have been built up".

Lord Hives was also alarmed: "In spite of charging fabulous prices there remains very little profit". Hives wrote "The company has dropped so far behind with major components such as frames,springing, engines, steering, brakes, etc. that where we can get help outside we have got to take advantage of it".

Every manufacturer will have specifications for both tensioning sequencing and staging.
Some will be in steps with torque ratings, some will be steps with an initial torque and an angular rating or otherwise known as Torque To Yield (TTY)
DO AS THE MANUFACTURER STATES!!!!!
Any specs stating a TTY must be adhered to as the bolts are a stretch type bolt and they MUST be replaced every time they are removed.
Incorrect tensioning can result in such things as blown head gaskets, cracked heads and stripped threads or snapped bolts in the block.

Dont listen to heresay as you have buckleys of getting them to coff up when something goes wrong!!

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Originally Posted by Zute

Still would like to know what "angle setting, is. Have never come across this before.

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An angle setting is degrees of a turn or Torque To Yield. For example:
STEP 1: 25Nm
STEP 2: 65Nm
STEP 3: +125degrees

After tensioning to step 2 in the correct sequence, an additional 125 degrees on each or the indicated bolts needs to be added.
You need to be accurate with these angles. Reason being is the bolts will add a specific torque based on how far they are turned, the diameter of the bolt and the thread pitch.
Not enough and it will not compress the head gasket enough, too much and you can snap the bolt.

Like everyone else has said most are different.with the LR 2.25 with it's copper headgasket you torque it down,run the engine up to temp and do it again.The bolts could be turned by hand after it was run.Almost all Cat gear is angle set after torque up. Pat

CAT gear uses torque turn method on all large fasteners. This method is to set torque to lower setting as per manual. Then turn number of degrees. This is to eliminate friction between parts varying the actual torque value. Is also used on larger bolts that would require a very big torque wrench. Tighten to set torque then turn 180 degrees

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Originally Posted by big harold

CAT gear uses torque turn method on all large fasteners. This method is to set torque to lower setting as per manual. Then turn number of degrees. This is to eliminate friction between parts varying the actual torque value. Is also used on larger bolts that would require a very big torque wrench. Tighten to set torque then turn 180 degrees

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Exactly.

What the manufacturer wants is for the bolt in question to be applying pressure at the desired force. From this and the known dimensions and elastic modulus of the bolt, you can calculate the required torque. But the actual torque to get this tension will differ from the calculated one by the friction both on the thread and under the head, which is difficult to predict accurately, especially if the tension requires enough load on these surfaces to break down the oil film. So the answer in these cases is to tighten it to a measured torque that is not going to involve friction problems, and then add the calculated amount of tension by measuring the extra turn angle. And as you say, it also has the advantage you don't need an inconveniently large (and expensive) torque wrench.

John

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Originally Posted by Brian Hjelm

That would be the Phantom III V12 from the late thirties. A very complex and troublesome engine.

Rolls Royce chronicler, Peter Pugh, described it as "too large and heavy to be popular as an owner-drivers car", and "with no major component common to any other car, the Phantom III stood no chance of being profitable. On the quality front it was clear that the Phantom III had been launched too early in its development".

Sir Arthur Sidgreaves, Managing Director, reported after a tour of the USA "Not only are we not progressing, but we are definitely going back. In other words we are being surpassed by the Americans in particular respect to those features on which our name and reputation have been built up".

Lord Hives was also alarmed: "In spite of charging fabulous prices there remains very little profit". Hives wrote "The company has dropped so far behind with major components such as frames,springing, engines, steering, brakes, etc. that where we can get help outside we have got to take advantage of it".

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Rolls Royce seem to have had problems with a lot of their designs in the early stages. I don't know if you are familiar with the history of the Merlin. It was developed from the 'R' engine, which for the 1931 Schneider trophy race developed 2350hp - but they had a great deal of difficulty getting the oil consumption below 20 gallons/hr. It is worth noting that when the Merlin went into service five years later it was only producing 800hp. But this increased throughout the war until by 1945 some models were over 2000hp, overtaking the larger Griffon that was supposed to replace it, showing their ability to improve a design rather than their ability to get it right in the first place. I have seen their products described as "a triumph of workmanship over design".

John

The materials and method of gasket construction has improved over time to a point that in some applications retensioning is no longer required.

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Originally Posted by JDNSW

Rolls Royce seem to have had problems with a lot of their designs in the early stages. I don't know if you are familiar with the history of the Merlin. It was developed from the 'R' engine, which for the 1931 Schneider trophy race developed 2350hp - but they had a great deal of difficulty getting the oil consumption below 20 gallons/hr. It is worth noting that when the Merlin went into service five years later it was only producing 800hp. But this increased throughout the war until by 1945 some models were over 2000hp, overtaking the larger Griffon that was supposed to replace it, showing their ability to improve a design rather than their ability to get it right in the first place. I have seen their products described as "a triumph of workmanship over design".

John

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Actually, the "H" engine became the Buzzard, also known as the "R" engine, for racing, because of its use in the Schneider Trophy. The Merlin was developed from the PV12. PV for private venture, authorised by Royce in 1932, with instructions to use as much "R" design features as practicable. It was the "H"-Buzzard-"R" series that became the Griffon. The last Griffons were three speed two stage supercharged engines with 2500 take-off horsepower and a life of 2000 hours. From the very first experimental intallation, the Griffon engined Spitfires out-performed Merlin engined ones. Interestingly, the Griffon turned in the opposite direction to the Merlin which pilots needed to keep themselves aware of.

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Originally Posted by Brian Hjelm

Actually, the "H" engine became the Buzzard, also known as the "R" engine, for racing, because of its use in the Schneider Trophy. The Merlin was developed from the PV12. PV for private venture, authorised by Royce in 1932, with instructions to use as much "R" design features as practicable. It was the "H"-Buzzard-"R" series that became the Griffon. The last Griffons were three speed two stage supercharged engines with 2500 take-off horsepower and a life of 2000 hours. From the very first experimental intallation, the Griffon engined Spitfires out-performed Merlin engined ones. Interestingly, the Griffon turned in the opposite direction to the Merlin which pilots needed to keep themselves aware of.

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Of course the first Griffon engined Spitfires outperformed the Merlin engined ones - the Griffon was not fitted until it outperformed the Merlin, which was later than planned (perhaps helped by the fact that the Merlin was already in production not only in the UK but by Packard in USA and tooling up for production in Sydney).

On the direction of rotation, do you know whether the engine turned in the opposite direction or the gear box was different? The Griffon, being intended to replace the Merlin was designed to fit a larger capacity in the same space, so a complete gearbox redesign was needed and may have involved an arrangement that changed the output rotation.

Most single engine Griffon installations, including Spitfires, used contrarotating propellers. Over 2000hp on a small single propeller aircraft causes real handling problems on takeoff and particularly for a plane like the Spitfire with a very narrow main gear track. (the rotating slipstream causes the rudder to be far more effective in one direction, the torque reaction causes a higher load on one wheel than the other, and when the tail is lifted or the prop speed increases gyroscopic effects try to turn the aircraft; unfortunately all these effects operate in the same direction)

John