Torque “plus” value - meaning?

[Brian Cameron]

What does the shop manual mean when it gives a torque value like “86.8 + 14” for the shock gland nuts?

Does that mean to torque to the first value, then add 15, and torque again (kind of like an angle gauge)?

[icarp]

HMMMM
got me thinkin

Ian

[winders]

Torque + angle?

[Brian Cameron]

I searched the entire manual and couldn’t find any reference to use of an angle gauge, even for head bolts or connecting rods bolts - so maybe using angle gauge for torque to yield bolts wasn’t a thing on 911’s of the 1979 SC vintage.

Seriously doubt this would be an angle gauge application- it’s a gland nut on a shock housing, there’s no “bolt” per se except the housing itself; can’t stretch that to the TTY point or the housing couldn’t be used again next time new shock inserts are needed.

Have also seen this notation in my 993 workshop manual, but it definitively references an initial torque value plus X degrees specifically.

This is the WSM page, and the Boge housing is the only item with this kind of notation:

[917_Langheck]

If you parse the mkp column you will see that it relates directly to the ft lb column. In that same row the mkp reads 12 +2, therefore it is reasonable to believe that this is a first torque reading followed by the second as an add to final, or circa 101.3 ft lb.

[Magyar Kiwi]

I believe this is a torque with a + tolerance only.
I.e. 12 mkp + 2 mkp. Allowable range of 12 to 14 mkp.
or 86.8 ft.lbs + 14.5 ft.lbs. Allowable range of 86.8 to 101.3 ft.lbs

Suspect the inconsistency, (compared to all the other torques) maybe because it was specified by BOGE.

[Brian Cameron]

Edit: ha, i see Magyar Kiwi beat me to it as i was composing the following

Wonder if it might be a tolerance?

Ie minimum of 12 mkp, but tolerance up to 2 more mkp more, ie for a total if 14 mkp, say, if 12 just doesn’t seem snug enough.

And what the heck kind of torque measurement is a metre-kilopond (mkp) anyway? Apparently it’s about 9.8 Newton meters… when did they drop mkp and switch to Nm?

Anyway tomorrow i guess I’ll torque those gland nuts to 94 ft-lb and see what happens…

[Dpmulvan]

Originally Posted by winders

Torque + angle?

You are correct, the + means angle. That means you would torque the bolt to 86.8 and then an additional 14.5 degrees not another 14.5 lbs.

[thetorch]

Originally Posted by Dpmulvan

You are correct, the + means angle. That means you would torque the bolt to 86.8 and then an additional 14.5 degrees not another 14.5 lbs.

That's pretty wild. 14.5 degrees? Seems crazy specific for this example - a gland nut on a shock housing. 1/24.827th of a turn? 14.4 i could MAYBE understand (1/25th of a turn), but 14.5 is a weird number. Has to be some backstory on this one, no?

[Brian Cameron]

Edit: jeez, thetorch beat me to it again

Originally Posted by Dpmulvan

You are correct, the + means angle. That means you would torque the bolt to 86.8 and then an additional 14.5 degrees not another 14.5 lbs.

I rather doubt that, for 2 reasons:

1. The second measurement corresponds to the conversion from kilopond-meter to ft-lbs; it is very unlikely that an angle torque would coincidentally be the exact same number. See conversion table below.

2. I have never seen an angle torque given that is anything but a whole number. How would you reliably measure a half degree (14.5) with a dial gauge? The smallest gradation is 2 degrees, so you’d have to be precisely at one quarter of a gradation.

[dutchcrunch]

is that torque for a friction nut?

[Brian Cameron]

Gland nut for koni sport insert:




Close up:





Anyway the WSM torque value appears to be a moot point, I revisited the Koni instructions (for which it looks like they subcontracted IKEA) and their spec is 89 ft-lb / 120 Nm

[rwest]

Does it have a bend down tab or locking piece that you might need to turn to an exact spot?

You torque to spec and then add torque to get the tab to the groove?

[Brian Cameron]

Nope, there are tabs only on the dish washer and tab washer (9 & 10 in the diagram) on the very top of the shock piston (top part of #7), after it passes through the fender bushing (#8).

The part with the torque value in question is #4. Did it today using the Koni value of 89 lb-ft shown in my previous post.

[Walt Fricke]

I think the + means a tolerance of -0, +14.5 in lbs ft. Too little torque and the gland nut (I really wondered what the "plug" was until enlightened) can loosen. Has happened to me as I lack the tools to use a torque wrench here. But the shock insert and the strut tube are plenty strong so as not to distort due to the extra torque. Isn't steel stronger in compression than tension? The strut is in tension, the insert in compression.

If you have an innie gland, I see Koni even gives a rule of thumb spec for the gap between the gland flange and the top of the strut housing, which one presumes is where you end up when within the range specified.

[Indescikov]

Quite common to torque cylinder head bolts to a fixed value and then additional 180 degrees of rotation after attaining the initial torque. Some cases its done twice following the bolt tightening pattern.

[Dpmulvan]

I thought torque angle was a + sign I dunno.

[dannobee]

Walt has it right. Instead of a + or - tolerance, they only want you to err on the tighter side, i.e., +, no minus. They could have said 94 + - 7, but who knows of their though processes at the time.

And if we're going to pick nits, who had a torque wrench in 1979 that could measure down to tenths of a ft lb?

[Brian Cameron]

Yeah, good point on the gradation of torque wrenches but the primal measurement wasn’t ft-lbs, the original measurement was given in kilopond-meters, then converted to ft-lbs (with excessive precision) for the benefit of us troglodytes on the other side of the Atlantic. So the original intended setting was a whole number on the KPM scale.

To assuage my curiosity about that metric (KPM) I consulted the fount of all wisdom and argument settlements, Wikipedia. Turns out it is an obsolete non-standard metric based on gravity, ie one pond is the force at earth gravity (approx 9.8 m/sec2) exerted by one kilo of mass. It converts to the SI standard measurement of force Newton-meters as 9.80665 Nm because it is explicitly linked to gravitational force.

That metric was used in Germany in the 1940’s for measuring the thrust of rocket engines and the USSR continued that use until around the late 1980’s. Also used for measuring the tension of bicycle spokes and draw weight of bows in archery (vs lbs draw weight). And of course, for 1979’s Porsche torque settings.

http://https://en.m.wikipedia.org/wiki/Kilopondmetre