Torque and turn equals what?

[sled dog]

Been watching the torque wrench / impact responses in another thread, and have used the torque / turn for years. But is there a formula to calculate what the final torque would be on a torque / turn? 12 years ago worked with a young mechanic to inframe a 3406. I was working with a shattered, casted right wrist, so slightly hampered as to what I could do, or pull. I remember us torqueing the mains, then the turn. We used a 19 to 1 multiplier, he did the pulling, and I held the torque head, socket and reaction bar up. My 1 5/16 socket is still marked with 6 paint marks. Been too long, don't remember how many degrees, but remember thinking that final torque must have been WAY up there. Always wondered about that...

 

[Truck Shop]

Using the 3406B as a platform for your question, first there were three different rods used for the B.
The 8N, 7E and 9Y, the eight and seven both pre-torqued to 60 lbft then a 120* twist, the 9Y at 66 lbft
and a 90* twist with both having a plus or minus 6 lb ft. The early rod worked out to 185 plus/minus 5 ftlb
at full torque the late rod at 160 ftlb plus/minus 5 ftlb IIRC.
Mains were 190 ftlb pre-torque with a 120* twist which worked out to 340 ftlbs plus/minus 10 ftlbs. IIRC

Correct me Nige, C Mark if I'm wrong or any other Cat wrench for that matter.

 

[Nige]

Been watching the torque wrench / impact responses in another thread, and have used the torque / turn for years. But is there a formula to calculate what the final torque would be on a torque / turn?

As far as I know there is nothing official as to what the equivalent final torque should be after "torque + turn", whatever the turn was. From memory I know of varying degrees on different locations. 60 degrees, 90, 120 & 180 being the common ones but something tells me I've come across others in the past.

I guess a logical response to "What's the equivalent final torque?" would be........
"Why do you need to know? If you put the correct torque on it in the first place and pulled it the required number of degrees as per the D&A instructions or the Specification - it's right......"

Mathematically it's possible to calculate what the final torque OUGHT to be, but you have to make a lot of assumptions along the way regarding such things as thread form, friction between threaded fastenrs, friction between bolts heads/nuts and washers, etc, etc. I recall studying it at uni but have never used it since.

If you want to dig into the subject, crack on & don't let fear stop you - http://vdi2230.de/engineering fundamentals.pdf

 

[Truck Shop]

We did it years ago using three 600 lb torquer's starting at a base of 290 ftlb increasing at 10 ftlb increments, all three came within 10 to 15 ftlbs of each other. IIRC.

It was a slow day.

 

[Nige]

We did it years ago using three 600 lb torquer's starting at a base of 290 ftlb increasing at 10 ftlb increments, all three came within 10 to 15 ftlbs of each other. IIRC.

It was a slow day.

I'm sure lots of people have done the same thing on a slow day, just for sh1ts & giggles .........

 

[56wrench]

the only important thing to remember is that the torque-turn method imparts predetermined stretch into the bolts/capscrews thereby applying the engineered clamping force to the component. the first torque-turn fasteners i ever encountered were in Deutz air cooled diesels, specifically the cylinder barrel/head retaining hardware. that was the first time i had used the procedure. a lot of deutz engines had cyl head sealing issues when operators used any form of starting fluid to get them going because the fasteners would stretch. use of starting fluid in those engines is bad. they usually use an intake manifold preheater which needs to be in operating condition. i am referring to the old BF6L913 etc

 

[Nige]

Deutz 913 Series..? That brings back memories, none of them particularly edifying.

 

[truckdoctor]

Thats what I remember about torque turn. It's about proper bolt stretch. I remember having a fastener class and we used a dial indicator to measure bolt stretch on 3/8's bolts to seal where they stopped stretching and then when it gave up and started to yield. Went through that with some 385 track bolts.

 

[56wrench]

actually, once i accepted the metric way of thinking, i did not mind working on them. no coolant-related issues, just a few awkward pieces of shrouding. those engines were where i first learned to do basic verified fuel injection timing. after those, other injection timing was simple

 

[sled dog]

Thanks guys for all of your answers. After TS answered I remembered the 120 turn. I guess the final torque wasn't as high as I would have guessed, just seemed astronomical laying under that pig Western Star holding all that stuff up with a bad flipper...

 

[fastline]

There is not a direct correlation thus the reason for that method. These are what we call "torque to yield" values. This is also why it is not cool to reuse bolts like this inside an engine. The "turn" ensures that the bolt received the proper amount of elongation to hit yield. The main issue as we have run into with even aircraft, is a torque value without other parameters is useless. Is that torque dry? with moly grease? Grease under the bolt head? In some cases is just torquing even to spec, you can over stretch a bolt. You area dealing with torsion and tension, and even shear when torquing a bolt. One of the main reasons to hit yield on say a rod cap or head is get any of the elastic deformation out as a bolt could cycle through that zone long enough it will fatique and break. Strength will continue to increase into the yield zone, so max strength and minimal elongation would be achieved at that zone.

So in short, the turn method usually achieves the intent better than just torque alone.

 

[Nige]

I remember the case of a complete 789 front wheel group nearly killing two mechanics. Contrary to the D&A Procedure or the Specs they proceeded to apply moly-based anti-seize on the 15 x 1" bolts securing the retainer plate then proceeded to pull them up to specified 830 ft lbs of torque to pull the wheel group up on to the taper on the bottom of the suspension cylinder rod. What they didn't realize was that either the torque figure should have been reduced by close on 50% when using that product - or simply install the bolts dry and use 830 as the factory intended. Apparently just as they finished pulling up the last one it pinged and the other 14 apparently followed it faster than you could get your pants zipper down - and apparently sounded somewhat similar. In the blink of an eye a couple of tons of wheel end assembly was on the deck and two stunned mechanics were looking at one another as if WTF just happened...?

 

[truckdoctor]

I seen that in class as well. Must be one of the D&A misprints. It's amazing how far thread lube can take torque over the fasteners engineered limit.

 

[Nige]

Somewhere I have a document that lists a load of different petroleum-based lubricants and anti-seize compounds and by what percentage a specified torque should be reduced when using each of them. The moly-based anti-seize was the highest of all.

 

[fastline]

Imagine having this issue bolting a $2M engine to a plane!!! This is what my bro had to design in when defining procedures for OEM installation.

The reality guys is people seem to get lost with what we are even trying to do when "torquing a bolt". We don't even 'want' to impart torsion, we are looking for tension and possibly elongation of the bolt.

The core issue is without critical information as to the alloy and heat treatment of the bolt, it can be difficult to determine the exact strength and elongation. Saying "grade 8" does nothing for me. But if I know the bolt is 4150 and what the temper is, I can determine hardness, ultimate strength, and optimal elongation, assuming you need EVERYTHING the bolt can give. In most situations, the bolt is just oversized!

The turn method is easily calculated based on the thread pitch, and initial torque is applied only to take up any play or slack. But if you have a compressible gasket, that is an issue! This method is primarily used on metal/metal interfaces with none, steel gasket, or oring interfaces. Compressible sealing washers is also a wild card.

I can tell you I noticed a super over engineered but required method of applying tension to some massive bolts I believe on one of the biggest marine engines in the world. Instead of throwing the torque turn at them, they use a stud, not a bolt, then run a nut down, then thread on a hydraulic puller behind the nut, and apply the exact amount of tension they wanted, run the nut down snug, and release the hydraulic puller. The beauty of this is they are not having the jam all that shear in the threads or all that torque in a bolt. If long enough, torsional deflection can be an issue and I was amazed of the engineering on this engine!
Found it!

28min in. Some might just enjoy the whole thing!

 

[Welder Dave]

I remember the case of a complete 789 front wheel group nearly killing two mechanics. Contrary to the D&A Procedure or the Specs they proceeded to apply moly-based anti-seize on the 15 x 1" bolts securing the retainer plate then proceeded to pull them up to specified 830 ft lbs of torque to pull the wheel group up on to the taper on the bottom of the suspension cylinder rod. What they didn't realize was that either the torque figure should have been reduced by close on 50% when using that product - or simply install the bolts dry and use 830 as the factory intended. Apparently just as they finished pulling up the last one it pinged and the other 14 apparently followed it faster than you could get your pants zipper down - and apparently sounded somewhat similar. In the blink of an eye a couple of tons of wheel end assembly was on the deck and two stunned mechanics were looking at one another as if WTF just happened...?

View attachment 230771

I know that pinging sound but from a different perspective. A 2-3/4" thick by 10ft. diameter pressure vessel head weighing over 10 tons had the tacks start pinging and the entire head fell off! Thankfully no one was in front of it and we kind of figured out what was happening. Took about 15 seconds. A wire feeder got crushed but the welder on the cart below was OK because it rolled out of the way. Made a dent in the concrete floor which was odd. There were a lot of wedges and hyd's. used to fit the head. I helped fit it back on. It had 2" long bridge tacks using 3/8" round bar about every 6" around the circumference. Took more time to grind out the tacks than to weld the root pass. Had to keep a tiger torch (weed burner) on it for preheat. Could have been a lot scarier.

 

[Truck Shop]

And------Some torque turns can be reused, Later Series 60 head bolts are reusable, defined by a minus sign on the bolt head. All good info above. Although dry torque can result in
uneven torque factor, normally just a drop of engine oil is enough in any standard automotive engine to achieve even torque. Probably the most over looked is the threads in the
block, all head and main block threads should be chased with bottoming tap also. Every item has to be free
of discrepancies to achieve even torque.

 

[Cmark]

Hydraulic tensioning is also SOP on the Cat 3600 series.

 

[Welder Dave]

Knew a guy who's dad was a certified DD mechanic at Waterous. Watched him put oil on head bolts putting engines back together. Even using torque values they say to do it in stages and not all at once.

 

[Nige]

And------Some torque turns can be reused,

Cat 3500 engine cylinder head bolts spring to mind. The idea of the torque-turn, like on the Series 60 TS mentioned above, is to get a more controlled clamping force on the threaded joint and not to take the fastener close to the yield point.
994 wheel studs are another example.

Hydraulic tensioning is also SOP on the Cat 3600 series.
View attachment 230780

I recall doing the same thing on some Mirrlees diesels in a power station back before the turn of the Millenium. Pull on the 4"-dia. bolts with the hydraulics then run the nuts down by hand. It made "torquing" a pleasure.