OOPS

V8Druid

V8Druid

do it as well as you can,but learn to do it better
Gecko said:
The trouble with torque wrenches and humans is they both try to measure torque, when the desired result is bolt tension.
Unfortunately, a torque wrench or 'experience' is usually only practical way of getting close.

If the tension is really critical, hydraulics is the way to go.
Click to expand...
used to get into IEP Doncasters in Blaenavon, most usually on a Sunday, or B/hol. with a crane, every other month or so to handle their hydraulic nut adjusting kit on top of their ****ing HUGE press ... was usually me due to the need to do it 'off shift'/odd hours, not to affect production time -- weird hours never bothered me and I always enjoyed getting in there - knew everyone well and wasn't exactly a hard day/night/however long it took.

vid below is the closest thing I can find in youtube, to give you some sense of scale ...... the big red nuts above the upper frame that had the Seah logo on in the vid, but IEP's press frame bolts were a lot longer to accommodate the hyd adjuster set up and the press was a lot taller ..... usually had a full 60ft of stick up and sat close to the press ... IIRC the bolts/nuts were circa 15" dia and six of 'em

 
Bri963

Bri963

Well-known member
Canal Navvy said:
I'd be disappointed if a torque wrench properly used wasn't more consistent than a human. It would seem that torque applied to a threaded fastener does not always stretch it by the same amount and torque wrenches don't notice this whereas humans can.
Actually measuring the change in length as a torque wrench applied the force just flagged up that they are inconsistent too.

I'll have to see if I can find the paper, I came across it when looking at the changes in stress/strain in wheel studs that had been overtightened 🙂
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Now at risk of boring the arse off youse, the effect of the applied torque can be affected by several factors, especially on re-used bolts. Condition of thread, (stretch, damage, rust), the cleanliness of mating faces being joined, face of bolt head/nut, lubricant used or not, type of lubricant. New bolts/screws used during assembly will be fitted dry, with a pre-coating, or will have a recommended lubricant precisely measured onto the thread before assembly. In the field you clean up as best you can.

this is why yield bolts are used on critical joints like mains, heads, big ends, flywheels, anything that can suffer thermal creep from heating/cooling, but not things like wheel nuts. You snug the fasteners to a low uniform torque, then tighten again to an angle. The angle applies a precise amount of elongation to the thread as x degrees = y longitudinal movement, so in theory the clamping force of each fastener is equal. For example on some Cat cylinder heads there are two bolt lengths holding the head down, they have the same initial snug torque but the longer bolts have a greater angle so the applied clamping force matches the shorter bolts.
 
Canal Navvy

Canal Navvy

Well-known member
Bri963 said:
Now at risk of boring the arse off youse, the effect of the applied torque can be affected by several factors, especially on re-used bolts. Condition of thread, (stretch, damage, rust), the cleanliness of mating faces being joined, face of bolt head/nut, lubricant used or not, type of lubricant. New bolts/screws used during assembly will be fitted dry, with a pre-coating, or will have a recommended lubricant precisely measured onto the thread before assembly. In the field you clean up as best you can.

this is why yield bolts are used on critical joints like mains, heads, big ends, flywheels, anything that can suffer thermal creep from heating/cooling, but not things like wheel nuts. You snug the fasteners to a low uniform torque, then tighten again to an angle. The angle applies a precise amount of elongation to the thread as x degrees = y longitudinal movement, so in theory the clamping force of each fastener is equal. For example on some Cat cylinder heads there are two bolt lengths holding the head down, they have the same initial snug torque but the longer bolts have a greater angle so the applied clamping force matches the shorter bolts.
Click to expand...

Got any eggs left after her last visit ? 🙂
 
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