Are studs better than bolts?

[bcmc33]

You can spend oodles of dollars on books and journals to become conversant on the latest knowledge, or follow generally accepted guidelines for our 50 year old technology.

Thank's for that, David,

Its good to know my ancient teaching and understanding was not a waste of time after all.

[GrUmPyBoDgEr]

Out of interest, How do ARP specify their tightening procedure for:-
1. Studs (not waisted).
2. Waisted Bolts.

I anticipate for:-
1. A straightforward high Torque figure with a tolerance
2. A low torque + An Angle with tolerances

John

It depends on the application. ARP's full catalog, including use instructions, is available on their web site. ARP recommend measuring bolt elongation for connecting rod bolts and they offer dial indicator tools for this application. This is fine when the big end is split at 90 degrees to the connecting rod long axis and you have access to both ends of the bolt, in situ. OK for my Twin Cam, less so for the FWE in the "other" project (unless I use Carillo rods and grind clearance into the crankcase to swing the "modern" big end configuration. Otherwise ARP specifies torque. The tightening angle method has been mentioned in this thread. In my experience that method is used in civil engineering applications (buildings, bridges) where people understand cubic meters of soil but otherwise could not be bothered to measure anything (yes, my academic background is Mechanical Engineering, second only to Physics as true art...ahem). The fastener elongation method has long been used in big dollar / big risk applications such as marine and aircraft powerplant applications. Without direct measurement of axial load, fastener elongation is the most reliable indication of tensile load.

Russ,

I hope I've not misinterpreted your posting but I understand that you consider tightening to a given angle to be "agricultural" when compared to "Torquing".
If that is the case I must disagree.
You & several others have quoted that measuring Fastener elongation is the most accurate method of insuring that the required clamping load has been achieved.
I think that is beyond dispute but tightening to Angle is second best.
The advantage of using the Angle method is that any form of friction from any of the component parts, by that I mean Thread Flank, Bolt underhead etc. Friction is eliminated from the equation.
The tightening angle is a geometric component related to the Thread Pitch where theoretically the Fastener elongation can be calculated.
Tightening to Angle is widely used in the assembly of modern Car Engines; not only for highly loaded fasteners like Head Bolts, Main Bearing & Big end Bolts, Torsional Vibration Damper central Bolt, Timing Sprocket to Camshaft etc.,etc. but also for Screwed Blanking plugs etc., where Fastener elongation is replaced by achieving the needed compression of Aluminium/Copper Sealing Rings.

I've been sitting back on this debate until now but felt the need to comment on the content of your Post with the best intentions


David also mentioned a Torque Tightening History going back 50 years. That must surely be an understatement I know of 1940's engines that employed all 3 mentioned Fastener tightening methods & think that 100 Years would be a closer estimate.

John

[bcmc33]

David also mentioned a Torque Tightening History going back 50 years. That must surely be an understatement I know of 1940's engines that employed all 3 mentioned Fastener tightening methods & think that 100 Years would be a closer estimate.

I have to smile at this comment, John, and you're quite correct.
When I referred to my ancient teaching, which was about 50 years ago on this subject, the methods being taught/learned then were considered as 'ancient'. The only thing that was missing was the technology to properly apply the knowledge of the day.
Just think what IKB could have achieved with todays technology.

Without the technology of today, and in the absence of perfect operator control, the torque-angle method cannot reliably be applied.

A QUESTION - what is the load applied to the con-rod bolts on say a 150 bhp Twink at 6500 rpm? Answers in psi, please.

[GrUmPyBoDgEr]

David also mentioned a Torque Tightening History going back 50 years. That must surely be an understatement I know of 1940's engines that employed all 3 mentioned Fastener tightening methods & think that 100 Years would be a closer estimate.

I have to smile at this comment, John, and you're quite correct.
When I referred to my ancient teaching, which was about 50 years ago on this subject, the methods being taught/learned then were considered as 'ancient'. The only thing that was missing was the technology to properly apply the knowledge of the day.
Just think what IKB could have achieved with todays technology.

Without the technology of today, and in the absence of perfect operator control, the torque-angle method cannot reliably be applied.

A QUESTION - what is the load applied to the con-rod bolts on say a 150 bhp Twink at 6500 rpm? Answers in psi, please.

Oh I think that even back then they had the required Technology; the "Protractor" & Mr Young had made his "Modulus of Elasticity" theory public knowledge.
It's the modern technology that makes life difficult with things like electric Spindles timing out & all sorts of other faults.
Ref. your question Brian, I'm no longer participating in the in depth discussions; as I mentioned before my Fastener Knowledge is only peripheral.
However with your background, the tightening figures given by ARP & being able to measure the CSA of the Conrod joint faces the sums should be simple.
Imperial units? How old did you say you were?
Have a good Weekend
John

[msd1107]

I had to smile about the comments on units. I'm at least as old as some of us old farts, and I learned metric in university.

And you will notice that all spreadsheets I publish are bi-lingual when it comes to unit input/output. So for those of us old farts that still think imperial, imperial it is. For the rest of the world, metric it is.

There are better things about which to argue.

David
1968 36/7988

[bcmc33]

However with your background, the tightening figures given by ARP & being able to measure the CSA of the Conrod joint faces the sums should be simple.
Imperial units? How old did you say you were?

How old - bloody ancient is all I'll admit to.

I've been working totally in metric since 1971. In 1970 all the Ford drawings were in imperial with the metric equivalent in brackets. In 1971 all new drawings were in metric with imperial in brackets. From 1972 only metric.

When I measure parts on the Elam its always in metric followed by bracketed imperial. When the imperial equates best, I reverse the record. (Just how pathetic does that sound?).

BTW, I asked for psi simply to equate to the ARP bolts and studs I've bought for my rebuild.

I'm at least as old as some of us old farts,

And David,

I don?t object to being called a fart, or any other derogatory adjective you can think of, but OLD ? NO.

[GrUmPyBoDgEr]

I had to smile about the comments on units. I'm at least as old as some of us old farts, and I learned metric in university.

And you will notice that all spreadsheets I publish are bi-lingual when it comes to unit input/output. So for those of us old farts that still think imperial, imperial it is. For the rest of the world, metric it is.

There are better things about which to argue.

David
1968 36/7988

Don't tell me about it David, I did my studying at one of the hardest times, having to cope with FPS, MKS & DIN Standards all within a couple of years; talk about confusing.
Trying to revert to FPS now would be a nightmare.
Is it just the USA that still works with FPS? I can't think of anywhere else.
Now someone will tell me that you can still buy 4 Lb of Spuds in England
(Lb = Lbf in Greengrocer Speak)
Well this threads gone quite mad anyway, considering the initial Question.
(& to which I still think I gave the appropriate Answer )
The most enlightening part was the talk of someones Wife preferring Studs

John

[bcmc33]

The most enlightening part was the talk of someones Wife preferring Studs

Not what I had in mind -- but still the best answer to date.

[GrUmPyBoDgEr]

However with your background, the tightening figures given by ARP & being able to measure the CSA of the Conrod joint faces the sums should be simple.
Imperial units? How old did you say you were?

How old - bloody ancient is all I'll admit to.

I've been working totally in metric since 1971. In 1970 all the Ford drawings were in imperial with the metric equivalent in brackets. In 1971 all new drawings were in metric with imperial in brackets. From 1972 only metric.

When I measure parts on the Elam its always in metric followed by bracketed imperial. When the imperial equates best, I reverse the record. (Just how pathetic does that sound?).

BTW, I asked for psi simply to equate to the ARP bolts and studs I've bought for my rebuild.

Ah yes, now the Pennies dropped ARP = USA = FPS
Yup same with me the Olympus Engines for Concorde was the first Metric job I did & we were developing the ISO Geometric Tolerancing system in parallel. Interesting times.
Oh & all of the Nuts & Bolts used on those engines (Double Hex.) were all sourced in USA, they cost a fortune but were superb.
UNF Fasteners were also used on later Metric Engines due to their supposedly better "self locking" properties (Thread Flank Angle / Pitch / Mean Dia. Ratios)
They know how to make Nuts & Bolts over there

I'm at least as old as some of us old farts,

And David,

I don?t object to being called a fart, or any other derogatory adjective you can think of, but OLD ? NO.