Head stud stretch

[Berlin Germany]

@jellyrug

by definition from mechanical engineering:

an expansion screw ! , at a given load, it lengthens permanently because it has been loaded beyond its elastic limit and this lengthening can be permanently determined with good measuring tools - even years after been turned out .

it will simply be longer than when delivered / when new.

the (elastic) stretch e.g. at a connecting rod bearing cap screw you can also easily measure that , but this screw or stud is normally never ever loaded beyond its elastic limit - means if put out it has the original length again as delivered .


stretch is no durable expansion.

a stretched screw returns to its original length.

an expanded one never ever - it remains in its longer, by torque etc. , stretched form and length .

eventually the us and the german engineers use other words for this type of screws,
but i´m tired to dicuss that any longer.

 

[jellyrug]

@jellyrug

by definition from mechanical engineering:

an expansion screw ! , at a given load, it lengthens permanently because it has been loaded beyond its elastic limit and this lengthening can be permanently determined with good measuring tools - even years after been turned out .

it will simply be longer than when delivered / when new.

the (elastic) stretch e.g. at a connecting rod bearing cap screw you can also easily measure that , but this screw or stud is normally never ever loaded beyond its elastic limit - means if put out it has the original length again as delivered .


stretch is no durable expansion.

a stretched screw returns to its original length.

an expanded one never ever - it remains in its longer, by torque etc. , stretched form and length .

eventually the us and the german engineers use other words for this type of screws,
but i´m tired to dicuss that any longer.

My Busa manual is on a different computer, as I never need it and it is on an old computer, I am not going to bother to look.

But on the Yamaha R1, where I just helped someone, the old manual also did not mention this. They however corrected that, so see below.

Anyway, in most cases when I rebuild a motor, I will replace the connecting rods, it is a small cost to having to do things over later. I will NEVER use the same bolts.

The Yamaha manual, I guess they must have learnt from Mercedes, to do things the right way? They are telling us exactly what I am trying to tell you.

And, whoever wrote the manual for the new R1 Yamaha below, missed something important. Want to guess what?

 

[jellyrug]

^^^

Vol.7　Screw Tightening Control Methods | NBK | Couplings, Screws, Clampers

Although fastening objects using the axial force generated from tightening is the main role of screws (bolts), in actual work, I think there are many people who control the torque by tightening with a torque wrench, because it is difficult to directly monitor the axial force, and so guarantee...

www.nbk1560.com

 

[jellyrug]

Hayabusa Gen 3 Manual snapshot.

Conrod bolts may not be reused, they are tightened into the "plastic region" per the procedure. Means once torqued and turned through x degrees, the bolt threads are permanently distorted.

 

[Redcurbjumper]

Hey all,

Details nobody has covered yet:

1) if you are using Locktight to install your studs, make sure you apply the same torque (dry fit everything) as you would during final assembly. Let the lock tire dry under tension for a few days.

2) The threads on your studs/washers/nuts are going through a “Break-in” process each time they are torqued. It takes upwards of 8 to 10 full torque events to mate the threads. (If your super anal, you will wash the threads and relube with ARP Ultra Torque each cycle) Don’t mix and match the studs and nuts now, they are now married to each other and will provide even clamping pressure on all studs when using the proper torque sequence. (ARP Ultra Torque is supposed to eliminate the need for fastener break-in, but I do it anyhow)

3) Copper-coat on the spacer plates below your cylinders will have some squish out depending on how much too much you have used. Another source for loosening of the clamping force of the studs.

4) Are you Micro-Inspecting ALL the mating surfaces of the case, spacers, block, gaskets, head ? Magnifying Glass and a bright flashlight shining sideways across the surfaces?

5) If you have milled your block or head, have you measured the length of your alignment dowels? Are they too long now? Perhaps holding the head up off the gasket?

6) How many of us use calibrated torque wrenches?

Extreme attention to detail is priceless......