Con rod breakages and oil pressure

Previously Gordon Johnston wrote:

An interesting snippet from Chares Udall's memoirs. Charles was a designer for Velocette who jumped ship to work for AMC.

"We encountered a problem with the Norton twins which were sold in America where they were used at high speed for longer periods and some were raced. The alloy rods were breaking under the small ends. Samples were sent to High Duty Alloys at Reddich. They found that the rough boring of the small ends had not been cleaned up leaving roughness, leading to fatigue breaks. The rough boring had been done at a slight angle causing continual flexing. Plumstead had not picked up on either of these things.

There was trouble with lubrication on the Dominators. At 6,000rpm oil pressure fell to zero. I increased the capacity and speed of the pump and the problem vanished."

Interesting and it does explain why conrods didn't like the awful thrashing I gave them in the days of my feckless youth. It also shows that not everything produced at Bracebridge Street was perfect.

Well I will defend this, firstly its all down the how much oil is being returned back to the oil tank if there is very little oil in the sump then the oil pump cannot pick up the oil and return it back , and secondly if the oil fillter gorse is block up with gunge, so you do not get a good oil follow back to the oil pump so then the peressure releeve valve shuts down as the is no pressure .then there is little of the oil been Back compressed to feed the small end, so it then runs hot, So then you have the contents of the metalligy of the alloy componants, And the small end has a bronze bush, there was no mention of this! , so you cannot say that is rough boring, so you cannot real blame the workforce of Bracebridge street, as the same things happed to Triumph as well, And the 650 manxman motors were bench tested to run for 12 hours at 6500 rpm and were calamed safe to 9000rpm by Doug Hele, Test engineer, of the time, and they were raced at Thuxton 24 hour race on three years running and won every race and beat Triumph 650 by 1 min and 20 seconds so there you are,

yours Anna J

Previously anna jeannette Dixon wrote:

Previously Gordon Johnston wrote:

An interesting snippet from Chares Udall's memoirs. Charles was a designer for Velocette who jumped ship to work for AMC.

"We encountered a problem with the Norton twins which were sold in America where they were used at high speed for longer periods and some were raced. The alloy rods were breaking under the small ends. Samples were sent to High Duty Alloys at Reddich. They found that the rough boring of the small ends had not been cleaned up leaving roughness, leading to fatigue breaks. The rough boring had been done at a slight angle causing continual flexing. Plumstead had not picked up on either of these things.

There was trouble with lubrication on the Dominators. At 6,000rpm oil pressure fell to zero. I increased the capacity and speed of the pump and the problem vanished."

Interesting and it does explain why conrods didn't like the awful thrashing I gave them in the days of my feckless youth. It also shows that not everything produced at Bracebridge Street was perfect.

Well I will defend this, firstly its all down the how much oil is being returned back to the oil tank if there is very little oil in the sump then the oil pump cannot pick up the oil and return it back , and secondly if the oil fillter gorse is block up with gunge, so you do not get a good oil follow back to the oil pump so then the peressure releeve valve shuts down as the is no pressure .then there is little of the oil been Back compressed to feed the small end, so it then runs hot, So then you have the contents of the metalligy of the alloy componants, And the small end has a bronze bush, there was no mention of this! , so you cannot say that is rough boring, so you cannot real blame the workforce of Bracebridge street, as the same things happed to Triumph as well, And the 650 manxman motors were bench tested to run for 12 hours at 6500 rpm and were calamed safe to 9000rpm by Doug Hele, Test engineer, of the time, and they were raced at Thuxton 24 hour race on three years running and won every race and beat Triumph 650 by 1 min and 20 seconds so there you are,

yours Anna J

I did read that large quantities of engine parts were scrapped by AMC once they realised they could not repeat the accuracy obtained at Bracebridge ST with the Machinery brought accross and the loss of the workforce. The loss of oil pressure is thought to be down to the centrifuge action of the crank. Although I do wonder if crank flexure allowed oil loss at the flywheel joint .This may cause an intermittent supply.I ran my 88 at 7000 rpm without a worry and never suffered rod damage.Siezure was an issue.

In my humble opinion, most of the "Norton" problems that AMC had to solve were actually AMC introduced . The Dommy when used within its design parameters was a very reliable unit .It was designed well before motorways and was never intended to be a racer.If AMC had not sucked all the cash out of the then profitable Norton and overstretched the design who knows what they would have developed.I once went on a train journey with JH and was "enlightened" by his revelations. He was pretty scathing with his opinion of the AMC operation.

Previously anna jeannette Dixon wrote:

Previously Gordon Johnston wrote:

An interesting snippet from Chares Udall's memoirs. Charles was a designer for Velocette who jumped ship to work for AMC.

"We encountered a problem with the Norton twins which were sold in America where they were used at high speed for longer periods and some were raced. The alloy rods were breaking under the small ends. Samples were sent to High Duty Alloys at Reddich. They found that the rough boring of the small ends had not been cleaned up leaving roughness, leading to fatigue breaks. The rough boring had been done at a slight angle causing continual flexing. Plumstead had not picked up on either of these things.

There was trouble with lubrication on the Dominators. At 6,000rpm oil pressure fell to zero. I increased the capacity and speed of the pump and the problem vanished."

Interesting and it does explain why conrods didn't like the awful thrashing I gave them in the days of my feckless youth. It also shows that not everything produced at Bracebridge Street was perfect.

Well I will defend this, firstly its all down the how much oil is being returned back to the oil tank if there is very little oil in the sump then the oil pump cannot pick up the oil and return it back , and secondly if the oil fillter gorse is block up with gunge, so you do not get a good oil follow back to the oil pump so then the peressure releeve valve shuts down as the is no pressure .then there is little of the oil been Back compressed to feed the small end, so it then runs hot, So then you have the contents of the metalligy of the alloy componants, And the small end has a bronze bush, there was no mention of this! , so you cannot say that is rough boring, so you cannot real blame the workforce of Bracebridge street, as the same things happed to Triumph as well, And the 650 manxman motors were bench tested to run for 12 hours at 6500 rpm and were calamed safe to 9000rpm by Doug Hele, Test engineer, of the time, and they were raced at Thuxton 24 hour race on three years running and won every race and beat Triumph 650 by 1 min and 20 seconds so there you are,

yours Anna J

Anna, the whole point of a dry sump lubrication system is that the capacity of the scavenge side is greater than that of the feed side. Thus you are normally returning an air/ oil mixture to the tank. Oil remaining in the sump depends on the location of the pick-up point.

My correspondence with John H contains quite a few snippets of information about the problems with the first 650 and Atlas engines. He is quite scathing that Norton followed the AMC 650 path in bascially using adapted engine partsdesigned for a smaller, less powerful motor. Some of his comments about Charles U and his engineering talents are very interesting.

The 650 already had its share of production problems.......crankshaft failures, pistons breaking and barrels distorting....... and consequently its original launch date was seriously delayed by nearly a year. Fixing these initial problems cost the Norton factory dearly and it is amazing that the engine even got into production let alone achieve success on the race track. In a way, these track successes went some way to prove that quality control, at the factory, was very poor and needed to improve ........fast!

Reports soon began to filter back, from the USA, regarding crankshaft failures. Some caused by poorly drilled crankshaft oil-ways and others due to the ignition timing changing itself to over-advanced and triggering full self-destruct mode of the bottom end bearings.

The move to Plumstead, after December 1962, did not help as many of the re-used, ex-Bracebridge machining tools, were poorly mounted on uneven bases and consequently numerous mistakes then crept into the manufacturing processes of crankcases, conrods and camshafts.

Not many people realize that, in the first fews years of manufacture, both the 650 and 750 engines had the 3 start oil pump drive gears, non-drilled conrods and a low pressure feed to the rockers. In the end the conrods andpiston rings bothwent through 3 changes in order to achieve better reliability.

My correspondence with John H contains quite a few snippets of information about the problems with the first 650 and Atlas engines. He is quite scathing that Norton followed the AMC 650 path in bascially using adapted engine partsdesigned for a smaller, less powerful motor. Some of his comments about Charles U and his engineering talents are very interesting.

The 650 already had its share of production problems.......crankshaft failures, pistons breaking and barrels distorting....... and consequently its original launch date was seriously delayed by nearly a year. Fixing these initial problems cost the Norton factory dearly and it is amazing that the engine even got into production let alone achieve success on the race track. In a way, these track successes went some way to prove that quality control, at the factory, was very poor and needed to improve ........fast!

Reports soon began to filter back, from the USA, regarding crankshaft failures. Some caused by poorly drilled crankshaft oil-ways and others due to the ignition timing changing itself to over-advanced and triggering full self-destruct mode of the bottom end bearings.

The move to Plumstead, after December 1962, did not help as many of the re-used, ex-Bracebridge machining tools, were poorly mounted on uneven bases and consequently numerous mistakes then crept into the manufacturing processes of crankcases, conrods and camshafts.

Not many people realize that, in the first fews years of manufacture, both the 650 and 750 engines had the 3 start oil pump drive gears, non-drilled conrods and a low pressure feed to the rockers. In the end the conrods andpiston rings bothwent through 3 changes in order to achieve better reliability.

Well I was a marine engineer, and every engine I rebuilt as never had any trouble , as I pay attention to oil ways and large and small ends , and pressure releaf valve and oil pump and oil tank , the Norton engine has only two points thats under Pressure that being the large ends and rocker motion , the rest is Slash feed , so its all down to the quialty of the oil , and its Viscoity and the fitteness of the oil pump for pressure , and the control of pressure from the pressure releaf valve and keeping the oil clean you can tell if things are a miss by checking the filler in the sump plug, there micro paticals in there, so this is a tale tail sign of wear and tear,

so thats why we do winter strip downs to see the problem and check for wear, and replace parts as needed, and check your oil to see how clean it says is another tell tail sign if it get black with in a month or so, then there is something not right somewhere, My freind in Sweden as never had any of his Bracebidge made Norton's fail, but he has had one of his Commando's let go and not long after a major rebuild, that was carried out by a well knowen Norton engine builder in the UK, but this was tracked down to the automatic anti-wet sumping valve, that was fitted,

yours Anna J

The winter strip down - not every winter surely? If you are doing a few thousand miles a year - and in some cases spread over a number of bikes - anything more than routine servicing would seem unnecessary.

Back to the small ends. If you rough bore the small ends and then press in the bushes, the micro-cracks in the small end are still there waiting for cyclical stresses to propogate the cracks.

Even ships steel plates need to have punched holes reamed before rivetting to eliminate micro cracks which would otherwise propogate leading to eventual failure.

The small end bushies are a Interference fit so they have to be heated to fit the bush , and the rods were milled under size with milling you take two cut first cut is the pilot cut next cut is mill drill will a pilot next there reamed to a unsize, next there heated so the bronze bush can be fitted, if there is failure with the small ends is all down to the lack of lubrication ,or None at all,

Yours Anna J

All very interesting. There were problems in the early 60's with the rods snapping. The best thing to do on 50 years old engines is to fit new or known Commando rods to the 650 motors if your going to make them work hard. Please fit the shells upside down to block the hole off on the con rod, you don't need to oil the bores. Just think of the amount of oil spraying out of the bike ends up the bores and everywhere else in the motor.

This is what I did when I raced a 650 Norton on Vintage racing in the 80's. I used a 3 start gear on the pump and fed the rockers from the return as on my 1962 650ss road bike as I found the 6 start pump fed to much oil at the 5000 - 7200 rpm the motor constantly lived at.

As for stripping the motor every year to replace or check things please take no notice of this unless you have a problem or you need to.

I won the VMCC unlimited champion ship on the Norton 4 times. All I did was replace the valve springs and check rings etc because I thought I should after a full racing season. I never did strip the bottom end as it was fine. fresh oil every 4 meetings, the cheapest 20/50 I could find. No cam, followers or bore wear. I also only ran a pair of ball bearings in the mains, no rollers, I just let the 3 piece crank flex, again no problems.You would never on the road use a motor like on a race circuit. You would have no licence or would meet a sad end.

Cheers Tony

I know small end bushes were used at Birmingham, Did AMC also fit bushes?.I don't think they did. Just when did the rash of rod breaking begin?.

Previously robert_tuck wrote:

I know small end bushes were used at Birmingham, Did AMC also fit bushes?.I don't think they did. Just when did the rash of rod breaking begin?.

Small end bushes were only fitted to the 500cc and 600cc conrods. All the bigger twins had plain small end eyes unless deliberately bushed to accomodate a different piston.

During the testing of early pre-production and first generation production 650 engines rods broke because they could not cope with the power produced by these motors. Lubrication problems of the piston and small end were the main cause plus some bad drillings of the crankshaft oilways leading to bearing seizures.

Previously robert_tuck wrote:

I know small end bushes were used at Birmingham, Did AMC also fit bushes?.I don't think they did. Just when did the rash of rod breaking begin?.

Small end bushes were only fitted to the 500cc and 600cc conrods. All the bigger twins had plain small end eyes unless deliberately bushed to accomodate a different piston.

During the testing of early pre-production and first generation production 650 engines rods broke because they could not cope with the power produced by these motors. Lubrication problems of the piston and small end were the main cause plus some bad drillings of the crankshaft oilways leading to bearing seizures.

What i would like to know were you get this information from Phil

Yours Anna J

What i would like to know were you get this information from Phil

Yours Anna J

My John Hudson Notes and letters. He did work as a tester and development engineer at Nortons for 1 or 2 years.

Its about time someone wrote an article on JH ,his career at Norton/AMC, his work abroad ,his efforts to help ordinary owners, his unreal memory for Norton facts,his interest in racing and Music. The man was legend.

Quite right Robert......some of us tried quite hard to get him some form of reward for his efforts while he was still alive. An MBE or whatever but the NOC EC, in command at the time, were not interested. Two of the glossy mags each wrote a series of articles about him in the late 80s. & 90s. British Bike Mechanics and Motorcyle Sport.

Previously Phil Hannam wrote:

Quite right Robert......some of us tried quite hard to get him some form of reward for his efforts while he was still alive. An MBE or whatever but the NOC EC, in command at the time, were not interested. Two of the glossy mags each wrote a series of articles about him in the late 80s. & 90s. British Bike Mechanics and Motorcyle Sport. Hi Phil. Perhaps the club could ask members to post any interesting stories on JH and any links so at least we could be a reservoir of information for a future article.

Quite right Robert......some of us tried quite hard to get him some form of reward for his efforts while he was still alive. An MBE or whatever but the NOC EC, in command at the time, were not interested. Two of the glossy mags each wrote a series of articles about him in the late 80s. & 90s. British Bike Mechanics and Motorcyle Sport.

Yes he is a honered man , but now is a woman that trying to do the same if you lot will let me, yours Anna J

Previously anna jeannette Dixon wrote:

Previously Gordon Johnston wrote:

An interesting snippet from Chares Udall's memoirs. Charles was a designer for Velocette who jumped ship to work for AMC.

"We encountered a problem with the Norton twins which were sold in America where they were used at high speed for longer periods and some were raced. The alloy rods were breaking under the small ends. Samples were sent to High Duty Alloys at Reddich. They found that the rough boring of the small ends had not been cleaned up leaving roughness, leading to fatigue breaks. The rough boring had been done at a slight angle causing continual flexing. Plumstead had not picked up on either of these things.

There was trouble with lubrication on the Dominators. At 6,000rpm oil pressure fell to zero. I increased the capacity and speed of the pump and the problem vanished."

Interesting and it does explain why conrods didn't like the awful thrashing I gave them in the days of my feckless youth. It also shows that not everything produced at Bracebridge Street was perfect.

Well I will defend this, firstly its all down the how much oil is being returned back to the oil tank if there is very little oil in the sump then the oil pump cannot pick up the oil and return it back , and secondly if the oil fillter gorse is block up with gunge, so you do not get a good oil follow back to the oil pump so then the peressure releeve valve shuts down as the is no pressure .then there is little of the oil been Back compressed to feed the small end, so it then runs hot, So then you have the contents of the metalligy of the alloy componants, And the small end has a bronze bush, there was no mention of this! , so you cannot say that is rough boring, so you cannot real blame the workforce of Bracebridge street, as the same things happed to Triumph as well, And the 650 manxman motors were bench tested to run for 12 hours at 6500 rpm and were calamed safe to 9000rpm by Doug Hele, Test engineer, of the time, and they were raced at Thuxton 24 hour race on three years running and won every race and beat Triumph 650 by 1 min and 20 seconds so there you are,

yours Anna J

I did read that large quantities of engine parts were scrapped by AMC once they realised they could not repeat the accuracy obtained at Bracebridge ST with the Machinery brought accross and the loss of the workforce. The loss of oil pressure is thought to be down to the centrifuge action of the crank. Although I do wonder if crank flexure allowed oil loss at the flywheel joint .This may cause an intermittent supply.I ran my 88 at 7000 rpm without a worry and never suffered rod damage.Siezure was an issue.

the only thing was they had to bring back the machine operator to find out how he operated this machine , he said did you bring the plank , ! yours Anna J