What is the opinion on reusing rod bolts, crank studs( MK3) ,a used cam with different followers?

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robs ss said:
If the bolts and studs have previously been torqued properly then they have already been plastically deformed (read - started the failure process) includes the nuts though probably not as severe.
If they were not torqued properly (too loose) and were in a running engine for a while they are most likely some way down the path to fatigue failure.
Then again you might also enjoy a game of Russian Roulette!
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If the bolts have been torqued properly, they never get to experience loads which put them into the area where plastic deformation occurs. However when the motor is running they experience repeated stretching which can cause fatigue. If I was rebuilding the motor, I would try to find some original old stock bolts. I would not use bolts which are not ground to size or are of suspect tensile strength. It is possible you might find some aircraft bolts which are suitable, but would you be prepared to buy a batch and test a sample to get the few you need to rebuild your crank ?
 

If the bolts have been torqued properly, they never get to experience loads which put them into the area where plastic deformation occurs. However when the motor is running they experience repeated stretching which can cause fatigue. If I was rebuilding the motor, I would try to find some original old stock bolts. * I would not use bolts which are not ground to size or are of suspect tensile strength. It is possible you might find some aircraft bolts which are suitable, ** but would you be prepared to buy a batch and test a sample to get the few you need to rebuild your crank ?
* unlikely, as sold replacements from reputable sources rarely supply NOS only remanufactured items as best as possible

** again extremely unlikely , short of a major science project :)
 
acotrel said:
If the bolts have been torqued properly, they never get to experience loads which put them into the area where plastic deformation occurs. However when the motor is running they experience repeated stretching which can cause fatigue.
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Alan
The theory (and proven in practice) behind torquing into the beginning of the plastic zone is that the pre-stress is so high that the bolts/studs do not experience any stress cycling - thus avoiding fatigue effects.
Rob
 
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jimbo said:
The manual mentions different ones, other than that I have nothing
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I have also read this and delved deeper, and yes there were different MK3 cranks, but it seems that one type only made into production and the bikes. There is even a drawing for a one piece crank, and another for one which would trigger an EI. Most probably ran out of money and these never made production.
 
Interesting stuff... once piece cranks and crank triggered EI... what might have been eh !?

They would still have been massively out gunned, but it wudda given us interesting bits to play with 40 years later !!
 
Madnorton said:
I have also read this and delved deeper, and yes there were different MK3 cranks, but it seems that one type only made into production and the bikes. There is even a drawing for a one piece crank, and another for one which would trigger an EI. Most probably ran out of money and these never made production.
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In late '75 I bought the basis of a race engine from Mike Sadler, an engineer in the experimental department, who had just been made redundant by Norton and needed some cash. He had intended it for his own race bike. Turns out it was an unbuilt kit of parts, so as he put each part on the bench for me he told me where they came from.....that is a longer story...

He told me the crank had been used in a test rig for Electronic Ignition triggered by the crank! As I understood it just a rig, not a running motor. They ran out of time.....

In truth it was a standard MkIII crank, until I got some people to mess with it!

I recently made contact with Mike, who I only met the once, on facebook!
 
Something on the loctite, the photo up above shows 271, red loctite, that product packaging says it needs to be heated to 300 degrees C to break the joint! (package arrived this morning and it just happens to be on my desk!

I would rather be using blue 243 loctite!

What say you?
 
SteveA said:
Something on the loctite, the photo up above shows 271, red loctite, that product packaging says it needs to be heated to 300 degrees C to break the joint! (package arrived this morning and it just happens to be on my desk!

I would rather be using blue 243 loctite!

What say you?
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The manual states to use 241 . 271 is strong, and hard to break loose, but with a little heat,its good to go(off)
 
SteveA said:
In late '75 I bought the basis of a race engine from Mike Sadler, an engineer in the experimental department, who had just been made redundant by Norton and needed some cash. He had intended it for his own race bike. Turns out it was an unbuilt kit of parts, so as he put each part on the bench for me he told me where they came from.....that is a longer story...

He told me the crank had been used in a test rig for Electronic Ignition triggered by the crank! As I understood it just a rig, not a running motor. They ran out of time.....

In truth it was a standard MkIII crank, until I got some people to mess with it!

I recently made contact with Mike, who I only met the once, on facebook!
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It would be awesome to get an interview with him showing you the parts on video. History like this is so fleeting.
 
swooshdave said:
It would be awesome to get an interview with him showing you the parts on video. History like this is so fleeting.
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Indeed, history is fleeting, and the parts are no longer with us as far as I know! After last racing it in 1979 I sold the bike in 1980. When I rediscovered it in 2007 I realised when talking to the guy who had by then owned it and raced it for around 15 years, that he knew nothing of the trick parts that were in it when I sold it. He bought it from the guy I sold it to, who apparently now lives in Scotland and nobody I know is in touch with him. I bought the frame back from it's second owner in 2009 and built another bike based on it!

I plan to be racing that bike again this year at some point. I may even go back to the UK in September to race it at Cadwell Park for the 40th anniversary! But at the moment the pull of an event in the South of France is a bit stronger.....
 
robs ss said:
Alan
The theory (and proven in practice) behind torquing into the beginning of the plastic zone is that the pre-stress is so high that the bolts/studs do not experience any stress cycling - thus avoiding fatigue effects.
Rob
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When the crank is cycling within the motor, it must flex or it would break. On every cycle, the bolts are subject to a load change. Many engineers do not know how to calculate safety factors for various materials. It is usually done on the basis of the 0.1% proof stress. In aircraft, materials are often stressed to 90 % of their 0.1% proof stress, which means they are right up near the stress level at which plastic deformation will occur. With steel most engineers think of a number and double it - i.e 50% of the 0.1% proof stress is used as the safety factor. While materials are kept below the stress level where plastic deformation occurs, they usually do not break until the load cycling causes fatigue. And the break usually occurs where there is a stress raiser, such as a notch in the surface of the material. If you tension the bolts to a level at which plastic deformation occurs, the bolt will grow in length as it is cycled, until it breaks. The 0.1% proof stress is the load at which plastic deformation just begins to happen. Even if the bolts are torqued up very high, they must experience the load cycle.
 
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acotrel said:
Even if the bolts are torqued up very high, they must experience the load cycle.
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No Alan - simply put, if tightened into the plastic zone they will not experience variations in stress nor strain.
 
robs ss said:
No Alan - simply put, if tightened into the plastic zone they will not experience variations in stress nor strain.
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What you are telling me is that when a Norton crank is spinning in a motor it is not stressed. The bolts are holding the crank together. If the crank flexes, the bolts experience a load change regardless of how tight you torque them up. If they are tightened into the plastic zone, they grow when the load is applied. Below the plastic zone they return to dimension as the load comes off. Load cycling with materials which are in the plastic deformation zone means they will continually grow until they break. If you think of the stress/strain curve - always stay where the material is elastic. Then it can spring back to size after each load cycle.
 
They are probably fine, the studs and bolts that is......

At a lowly 3000 rpm the crankshaft is doing around 50 revolutions a second, each piston has probably travelled a good 29 feet... If the whole show did not have some integrity or tolerance it wouldn't get pass the front gate on your next ride.

The crankshaft is more likely (imo) to fail at a transition (journal radius) long before the bolted flange could loosen,detach or fail at the flywheel that's if the flywheel didn't go first.

The connecting rods themselves are probably under some odd forces at TDC on the exhaust cycle.... I think it would be wise to check the rod pad surface and radiused corners where the bolt head seats all the same, new or old.

One of the best tools for chasing fairies is a jewellers eye glass.
 
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Have a look at a tensile testing machine sometime. For me, this stuff used to be bread and butter.
 
I did not race my Seeley for 20 years because I knew what is inside the motor. I still expect it to fly apart. My crank is balanced to 72%. At 7000 RPM the motor is dead smooth. Below 4000 RPM the whole bike rocks backwards and forwards. So what is the crank doing ?
 
Does a crank come apart at road speeds? Probably not. They make one piece cranks if you take it beyond that.
 
swooshdave said:
Does a crank come apart at road speeds? Probably not. They make one piece cranks if you take it beyond that.
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A one piece crank is obviously the answer. I am amazed the crank in my 850 has not let go. But I never rev it over 7000 RPM. I figure it should cop that on a fairy regular basis. Also when it is revving high, the motor is very smooth. So the crank is obviously not really being abused.
With a road bike with the 54% balance factor and the isolastics, the three piece crank is probably very safe at low revs. At high revs, the split in the drive side crankcase probably happens first.
 
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