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

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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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Only when the crank is stationary = no additional cyclic stress applied to the fastener. Think things are muddled here, applied cyclic loading and the stress within the fastener itself. A material will still experience variation in stress and strain in the plastic zone right upto fracture, if it did not then it would never fracture once in the plastic zone.

A con rod at TDC is stationary, so no odd forces other than the pressure from compression or the pressure from residual gas above the crown.
 
I haven't seen a crank failure on a street bike that I can recall. I'm sure it might happen from time to time but there are so many other weak points that the crank is probably the least worry.
 
All the split DS crankcases I have seen have been gassed to within an inch of their life - for racing use ones that don't show gassing, they should last longer.
Gassing is a trick foundry's use to get the melt to pour better but comprises material strength. It looks like hundreds of tiny pin pricks in the smooth machined surface. Still used today, but easily overcome by densificaton.
 
I have a set of crankcases in my garage to which I have welded a shrunk-on strengthening plate to cover the crack in the drive side. The young guy who gave them to me used to race his mates on the Great Ocean Road on weekends and rev his Commando to 8000 RPM. His mates used to ride Z900 and H2 Kawasakis.
 
acotrel said:
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.
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Madnorton said:
Only when the crank is stationary = no additional cyclic stress applied to the fastener. Think things are muddled here, applied cyclic loading and the stress within the fastener itself. A material will still experience variation in stress and strain in the plastic zone right upto fracture, if it did not then it would never fracture once in the plastic zone.
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Since it appears long proven metallurgical science will continue to be ignored I will move on away from this discussion.
Good luck!
 
Going back to the original question (at least partly), ie: is it better to re-use genuine conrod bolts or to use new ones... what would be really helpful would be to know from where to source new conrod bolts of reliably high quality? And not just in USA, which seems to have a lot more available by way of quality components than the UK.

Does anyone know who sells conrod bolts (for standard rods) that are as good as, or better than, the originals, in the UK? (I mean retailers, not aero engine workshops, unless they are know to be willing to sell to the public). I couldn't find an answer to this when building my last T140 engine and solved the quandary expensively by buying a set of Thunder rods. That isn't always what I want to do!
 
I would not and have not ever worried about replacing original bolts on an engine rebuild but if you prefer new, why not just buy them from any of the well-known suppliers of Norton parts? If I needed new bolts in the US, I'd buy them from Old Britts and not worry at all about who the manufacturer was - probably from the UK, anyway. Do you have some reason to think that fasteners for the purpose from AN are not going to be up to the job? Can't imagine they would be selling a lower strength-grade bolt than what is necessary for that service.
 
And I would not be doing my job if I didn't get them tested against the competition either. As above, buy from old brits and not worry.
Often when the rod snaps the bolts stay intact. You can have the best of everything put it together badly and they would not outlast original parts. No matter what you use, the old parts, super parts, or standard parts, put them together correctly and all will be well.
 
I once bought a set of bolts for a 3 piece Triumph crank from a reputable dealer in Melbourne. He sold me 'Bees' as being high tensile and claimed they were genuine Triumph. They were not even ground. When I tensioned them up, they would not even reach the recommended tension, they stretched so much. There is a point at which engineering and science cross over. An scientist is not an engineer and vice versa. What engineers do not know about science can be very dangerous. Failure Mode and Effects Analyses often don't take into account scientific matters such as metallurgy, safety factors and such things as hydrogen embrittlement from electroplating and interactions of dissimilar metals. Aerodynamicists are often not engineers but are scientists. In Australia, we lost our entire aircraft manufacturing base through the crash of one aeroplane which was flown before the wind-tunnel tests had been evaluated. The cause of the crash was flutter in the tail assembly. When the tunnel results were evaluated after the crash, they showed the flutter. Off-hand I can think of three similar incidents in the past 40 years, which have resulted in major catastrophe.
 
If the bolts have been tensioned beyond their elastic limit, I would not re-use them. But their replacements might be non-genuine, and give up in service. So you are cooked either way. Save your money, unless you can be sure of the quality of what you are buying. With the con-rod bolts in earlier Triumphs, the acceptable stretch when tensioned was specified.
 
That’s an interesting read on the ‘Pirate Parts’...
 
They all failed in the same place and look at the thickness at the break point in the wassel test. If he original cross sections were same there would not be a lot in it.
 
The only tensile tests I have seen where necking did not occur have been with cast iron.
 
jimbo said:
All torqued up, my rig worked good, used my trusty lathe as a crankshaft holder.

View attachment 8941 View attachment 8942 View attachment 8943
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FWIW if the adapter/extension is at 90 degrees there is no torque correction required, though it is supposed to ideally be 3" or less IIRC. I used this setup to torque my hard to reach head nuts...

What is the opinion on reusing rod bolts, crank studs( MK3) ,a used cam with different followers?
 
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yea ,with the longer extension length the less likely I would go with the 90* no correction method
 
This is the tool for torquing Ducati heads, a similar set up could be made to suit the Norton crankshaft ?
For bevels I just used a long ring spanner, heat, bend, weld a socket on, it would have to be much longer for a crank for clearance.

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