Are studs better than bolts?

[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

I have asked ARP this very thing via their website.
From the information given by Burton, there is a torque value with no tolerance.

I also asked where in the yield/elastic limit range do the specified torque values get placed. I guess I could have asked the question a little better, but whether I get an answer or not is anyones guess.


John,
When did torque-angle application become popular - I guess it was the early 80's. Now that's another story - and I'm not going there.

Well you have & I don't know.
I only got involved with the Automobile Industry at the beginning of the 80's where it was "standard practice"
Prior to that I was drawing fabricated & cast Aero Engine bits a long way away from Nuts & Bolts.
However with the experience I've gained, little though it may be, I still feel uneasy in my Boots about taking Bolts into Yield

[miked]

Jeremy,

My head touched the slipper as I lowered and you could not twist due to the studs. The chain slipper sticks out at an angle. I am just looking at it in Wilkins book. Page 72, 84, 122
When you say flip into place,are you talking about loosening the two countersunk headed screws?


Mike

[bcmc33]

I still feel uneasy in my Boots about taking Bolts into Yield

I would simply like to know where it is for the fastener, and ARP will know. Whether they will impart that information is probably doubtful.
You have to stretch fasteners to create the tension/clamp loading and to satisfy my curiosity, I want to know what they are.

Off to the CL meeting now - sod the snow.

[GrUmPyBoDgEr]

I still feel uneasy in my Boots about taking Bolts into Yield

I would simply like to know where it is for the fastener, and ARP will know. Whether they will imart that information is probably doubtful.
You have to stretch fasteners to create the tension/clamp loading and to satisfy my curiosity, I want to know what they are.

Off to the CL meeting now - sod the snow.

Yes stretching is one thing & quite rightly necessary but plastic deformation does take a Fastener beyond the point of no return.
CL Meeting; Arrow Mill maybe?

[bcmc33]

Off to the CL meeting now - sod the snow.

CL Meeting; Arrow Mill maybe?

Brave talk from me, John, - went about a mile and came back, roads are sheet ice. My AWD car is completely useless - at 5 mph I slid right past my road.

My local meeting is in Lichfield (Staffordshire branch).

[paddy]

When did torque-angle application become popular

Some more interesting information here:

http://www.boltscience.com/pages/tighten.htm

Paddy

[bcmc33]

I would simply like to know where it is for the fastener, and ARP will know. Whether they will impart that information is probably doubtful.
You have to stretch fasteners to create the tension/clamp loading and to satisfy my curiosity, I want to know what they are.

I did get a reply from ARP and was told that all the information I was asking about is in their catalog - pages 20 to 24.

I've had a brief look, and from what ARP say, it looks like the answer to my original proposition is YES.

The sytem won't allow me to add the large .pdf file, so for those interested this is the link to download the ARP catalog:
http://www.arp-bolts.com/Catalog/Catalog.html

I look forward to Herr Pelly's analytical comments

[TeeJay]

Downloaded OK. Thanks Brian

[Spyder fan]

Brian,

I would be happier using studs & nuts for the head to block application, my reasoning based on nothing more than intuition as follows:

A cast iron block is very fragile compared to a high tensile bolt or stud, therefore if the thread inside the block is effectively used to gain the required torque using a bolt there is the risk of thread damage and head failure. Using a stud that is screwed into the block at low torque to the complete length of available thread to the stud shoulder forms a solid and reliable anchor, the required torque is achieved by a high tensile nut on a high tensile thread : -- no damage if fitted correctly and more reliability.

No egg sucking intended here, I just think this is the reason studs were used as original equipment.

Regards

[bcmc33]

Alan,

Your intuition has some merit. As I said, my ancient teachings had it this way, only I couldn't remember why.

Reading the technical dialog in the ARP catalog explains it all very clearly.

[Spyder fan]

Brian,
That's a serious catalogue they have there! You normally have to part with some cash to buy a technical reference book to get that kind of in depth information. ARP are definitely on my list of approved suppliers just on the strength of their literature alone.

regards

[CBUEB1771]

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.

[CBUEB1771]

Yes stretching is one thing & quite rightly necessary but plastic deformation does take a Fastener beyond the point of no return.

I forgot to put my usual useless response here. The proximity you can take a fastener to yield depends on the required fatigue life. Fatigue life falls off precipitously the closer the initial load gets to yield (plastic deformation). The rule of thumb was always to keep the applied load on a fastener to 10%, or less, of yield to give infinite fatigue life. All reciprocating engine fasteners are subject to oscillating load and therefore fatigue life is a concern. I am sure that with modern numerical analyses the allowable load, in terms of percentage of yield, is much higher and much more dependent on exact application.

[rgh0]

Yes stretching is one thing & quite rightly necessary but plastic deformation does take a Fastener beyond the point of no return.

I forgot to put my usual useless response here. The proximity you can take a fastener to yield depends on the required fatigue life. Fatigue life falls off precipitously the closer the initial load gets to yield (plastic deformation). The rule of thumb was always to keep the applied load on a fastener to 10%, or less, of yield to give infinite fatigue life. All reciprocating engine fasteners are subject to oscillating load and therefore fatigue life is a concern. I am sure that with modern numerical analyses the allowable load, in terms of percentage of yield, is much higher and much more dependent on exact application.

My understadning for the design of most critical bolting is to preload the join being bolted so that the bolt itself is not subject to fluctuating loads. This is how head bolting and conrod bolting is designed. As the applied load comes on the join the bolt load remains essentially constant and the compression load on the join releases slightly to balance the load applied. Thus fatigue life of the bolt itself is not a concern in practical terms

cheers
Rohan

[msd1107]

My useless response is even more useless than normal since my degree is in math, not some useful physical discipline.

Rohan's response is the technically correct response. If you require infinite life in a fluctuating load environment, the preload should exceed the maximum fluctuating load. The bolt then in essence sees a constand load. Otherwise, the bolts should be replaced on a maintenance schedule that conservatively predicts the number of load cycles and peak load as a percentage of yield.

This preload is essential for bolt materials that do not have infinite life under fluctuating load conditions.

If you go into a fluctuating load, the maximum load is dependent on the bolt material, alloying makeup, and heat treating. The bolt manufacturer should give guidelines for usage.

Fortunately, our cars generally do not have critically loaded bolts. Ferrous bolts, consistantly torqued with a torque wrench to industry specified values for the bolt size can be used and reused with safety. If you have any questions about the tightening history of a bolt, it is far less expensive to toss the old bolt and use a new one than to risk a failure.

If you use a torque wrench, the manufacturer will specify whether to use a washer, tighten dry or with a specified lubricant, the torqueing and retorqueing sequence.

Or the manufacturer can specify using a strain gauge or measure bolt elongation.

All these methods get to a specified preload condition that will not fail under the specified operating environment and life.

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.

David
1968 36/7988