750 Commando Crankshaft reassembly hardware question: Is new hardware really needed?

marshg246 said:
ARP nuts and bolts that I've seen have a radius that requires the ARP washers or they don't sit flat. I'm no expert on ARP and have only used the cNw sets, but those will not work properly without the special ARP washers.
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While that's certainly true for AN Spec washers against the radius of the bolt shoulder, I don't think it makes any difference where the nuts are concerned.
 
marshg246 said:
ARP nuts and bolts that I've seen have a radius that requires the ARP washers or they don't sit flat. I'm no expert on ARP and have only used the cNw sets, but those will not work properly without the special ARP washers.
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OK, so does that mean these studs on the crank are OK with (ARP) washers fitted? The crank doesn't normally have washers.
 
SteveA said:
OK, so does that mean these studs on the crank are OK with (ARP) washers fitted? The crank doesn't normally have washers.
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I can only say that the ARP bolts and nuts I've had in my hands required ARP washers. If there are ARP nuts that are completely flat on the bottom, then they would not require washers.

If you have washers you may or may not have enough threads available especially when using studs rather than bolts (2 washers)

Personally, I would not deviate from what AN sells for the crank kit and I use the appropriate kit for every crank.
 
marshg246 said:
I can only say that the ARP bolts and nuts I've had in my hands required ARP washers. If there are ARP nuts that are completely flat on the bottom, then they would not require washers.

If you have washers you may or may not have enough threads available especially when using studs rather than bolts (2 washers)

Personally, I would not deviate from what AN sells for the crank kit and I use the appropriate kit for every crank.
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That's fair enough, but does not address my case.

AN hardware does not fit a Steve Maney crank. He made the studs rather than bought them in, probably a good task for the apprentice!

Some time after he had made mine and before ceasing production, he told me he did fit 12 point nuts. He called them 'aircraft' nuts rather than ARP!

I will have the crank out shortly and see how it has faired.
 
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SteveA said:
That's fair enough, but does not address my case.

AN hardware does not fit a Steve Maney crank. He made the studs rather than bought them in, probably a good task for the apprentice!

Some after he had made mine and before ceasing production, he told me he did fit 12 point nuts. He called them 'aircraft' nuts rather than ARP!

I will have the crank out shortly and see how it has faired.
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Triumph used 12-pt nuts long before the ARP company existed, for instance, cylinder base nuts. Being 12-pt does not make a nut or bolt ARP. McMaster-Carr lists them as "High Torque 12-Point Flange Nuts". Flange bolts are also readily available that have nothing to do with ARP and do not require special washers.

Norton crankshafts would be an excellent place for 12-point nuts, especially the top two on pre-MK3 as it would allow full socket purchase on those nuts. But, the ARP brand nuts I've had would be a bad idea there.

So, are you calling them ARP because they are 12-pt or because they were made by Automotive Racing Products (ARP)?

See: https://arp-bolts.com/p/about.php
 
I think a subtle misunderstanding has crept into the conversation:
I referred to AN Spec hardware, referring to US Military aircraft (AN: Army Navy) requirements dating back to WWII; not Andover Norton OEM spec.

So Steve Maney's 'Aircraft' nuts are AN Spec, I believe, as are ARP.
Similarly, UNJF is an aircraft-specific UNF derived thread form - the nuts would work OK on a standard UNF stud, but not the other way around
 
This is what mine looked like from Steve.

Zoom in and you can see ARP on the nut.

IIRC these do not need replacing as a matter of course.

I would also suggest that unless you know EXACTLY what you’re replacing them with, new ones could well be a downgrade…

750 Commando Crankshaft reassembly hardware question: Is new hardware really needed?
 
Fast Eddie said:
This is what mine looked like from Steve.

Zoom in and you can see ARP on the nut.

IIRC these do not need replacing as a matter of course.

I would also suggest that unless you know EXACTLY what you’re replacing them with, new ones could well be a downgrade…

View attachment 104845
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Yes - I believe that these critical fixings (crank assembly and big end) should never be reused.
If done properly they will have been torqued to proof and, as such, their life is spent.
New bolts and studs here every time in my view.
Cheers
 
robs ss said:
Yes - I believe that these critical fixings (crank assembly and big end) should never be reused.
If done properly they will have been torqued to proof and, as such, their life is spent.
New bolts and studs here every time in my view.
Cheers
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Well I recall for certain that the bolts supplied with the Carrillo rods definitely do NOT need replacing.

I think it’s the same for the crank hardware, but confess I’m not 100% sure…

Anyone else recall the specifics from Steve ?
 
The limited re-use of fasteners has a lot to do with the self-locking properties of the locknut.
In aircraft applications there's a run-down torque and a final torque fiqure quoted.
When the rundown torque is below spec the nut is replaced. In safety critical applications, there's generally a hard limit on the times they can be re-used, which can be tricky when fitting V-band clamps, where they don't always drop cleanly into position (soft-faced hammers generally get a mention here) the first time.
Given that the ARP nuts aren't self-locking in these applications I don't believe there's a problem re-using the hardware - unless it's been apart multiple times.
 
robs ss said:
Yes - I believe that these critical fixings (crank assembly and big end) should never be reused.
If done properly they will have been torqued to proof and, as such, their life is spent.
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In fatigue-critical applications, bolts are pre-tensioned to 70-80% of their yield stress, which may be well over 1000 MPa for high strength fasteners.
Crank cheek flanges and flywheel are thus under compression, and a simple bolt/flange analysis reveals that the alternating stress occuring in the bolts is low and in the order of 10-20% of the bolt material's YS, if sizing is done correctly.
Should bolts be torqued to proof (=yield) stress in a fatigue-critical application? Never! If this is done (in error), the abused bolt and nut need to be replaced.

A petrol engine in a car has a design life of 150 000 km usually - we may assume the design life of a motorcycle to be 100 000 km. While the average speed of a car thoughout its design life is 70 km/hr, a motorcycle may fetch 80 km/hr.
This corresponds to 1250 running hours. Further assuming the average tachometer reading is 3000 rpm, we derive at 2.85E8 load cycles for the crankshaft bolts.
Bolt load depends on the revs to the square, but for now let's assume that the bolts were designed for an average of n=3000 rpm. A proper analysis would require a so-called rainfall analysis.

Fatigue curves (stress level vs. load cycles to rupture) for high-strength steels have a kink at 1.0E7 load cycles usually, above which their fatigue life is considered "infinite". My simple calculation shows that the crankshaft bolts were designed for an "infinite" life.
So, does this mean they will never fail at high load cycle figures? No! But the occurence is so low, it is never recorded.
Should I replace my crankshaft bolts? If you suspect that your bike has covered 1250 running hours (your crankshaft grind may give a clue - I'd be wary below 0.020"), as a matter of caution I suggest you replace the bolts. It's a cheap insurance.

- Knut
 
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mdt-son said:
In fatigue-critical applications, bolts are pre-tensioned to 70-80% of their yield stress, which may be well over 1000 MPa for high strength fasteners.
Crank cheek flanges and flywheel are thus under compression, and a simple bolt/flange analysis reveals that the alternating stress occuring in the bolts is low and in the order of 10-20% of the bolt material's YS, if sizing is done correctly.
Should bolts be torqued to proof (=yield) stress in a fatigue-critical application? Never! If this is done (in error), the abused bolt and nut need to be replaced.

A petrol engine in a car has a design life of 150 000 km usually - we may assume the design life of a motorcycle to be 100 000 km. While the average speed of a car thoughout its design life is 70 km/hr, a motorcycle may fetch 80 km/hr.
This corresponds to 1250 running hours. Further assuming the average tachometer reading is 3000 rpm, we derive at 2.85E8 load cycles for the crankshaft bolts.
Bolt load depends on the revs to the square, but for now let's assume that the bolts were designed for an average of n=3000 rpm. A proper analysis would require a so-called rainfall analysis.

Fatigue curves (stress level vs. load cycles to rupture) for high-strength steels have a kink at 1.0E7 load cycles usually, above which their fatigue life is considered "infinite". My simple calculation shows that the crankshaft bolts were designed for an "infinite" life.
So, does this mean they will never fail at high load cycle figures? No! But the occurence is so low, it is never recorded.
Should I replace my crankshaft bolts? If you suspect that your bike has covered 1250 running hours (your crankshaft grind may give a clue - I'd be wary below 0.020"), as a matter of caution I suggest you replace the bolts. It's a cheap insurance.

- Knut
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👍 👍 a long way round to agree that, for the cost of these fasteners and the consequences of failure - it's a no-brainer to replace.
 
Fast Eddie said:
Well I recall for certain that the bolts supplied with the Carrillo rods definitely do NOT need replacing.

I think it’s the same for the crank hardware, but confess I’m not 100% sure…

Anyone else recall the specifics from Steve ?
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I have not changed Carrillo rod bolts when replacing shells. I do use the Carrillo supplied lubricant and check stretch.

As I said earlier, I asked Steve Maney regarding his crank hardware. He said there is no need to change the hardware.

He said, 'aircraft nuts'. I assumed he meant ARP. Your picture shows my assumption was correct.

I fitted ARP nuts. No washers. Black ones even! Thus differentiating them from other 3/8" x 24 ARP nuts I have used on the bike.
 
marshg246 said:
Triumph used 12-pt nuts long before the ARP company existed, for instance, cylinder base nuts. Being 12-pt does not make a nut or bolt ARP. McMaster-Carr lists them as "High Torque 12-Point Flange Nuts". Flange bolts are also readily available that have nothing to do with ARP and do not require special washers.

Norton crankshafts would be an excellent place for 12-point nuts, especially the top two on pre-MK3 as it would allow full socket purchase on those nuts. But, the ARP brand nuts I've had would be a bad idea there.

So, are you calling them ARP because they are 12-pt or because they were made by Automotive Racing Products (ARP)?

See: https://arp-bolts.com/p/about.php
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Steve Maney called the later nuts he used 'aircraft nuts'. I assumed he meant ARP, and 12 point. I didn't specifically ask him if they were ARP.

I fitted ARP nuts, they came in ARP packaging. No washers. Fast Eddie's picture shows that Steve used ARP, no washers!
 

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