Torqueing a wobble extension

[Son O Lark]

As to the swallow comments, I don't think Lark Parker has seen Monty Python And The Holy Grail.

[WCP]

I believe that brass nuts were factory issue for exhaust studs. The '63 Hawk (Canadian built) that I bought new in '63, had them. These nuts are approx. double length and of course national fine thread.

[gordr]

FWIW, sometimes thought problems like this can be resolved by thinking of the extreme case. Ask yourself, "how much torque would I put on the fastener if the wobble extension, was set at 90 degrees to the axis of the fastener?" (say you took a socket and slotted one side of the drive recess to permit the extension to go that far) In that instance, it's pretty easy to see that the answer would be zero. All the force would be directed at trying to move the fastener sideways. A great way to get isometric exercise, but otherwise pointless.

Let's see now. We have two endpoints. Extension right in line with fastener: 100% torque transfer. Extension at 90 degrees to fastener, 0% torque transfer. (looks at book of trig tables) Well, looky here! This property of angles, called cosine, has the same end points. Angle zero degrees, cos 0 = 1.0 Angle 90 degrees, cos 90 = 0. So the torque through a wobble extension (or U-joint) is equal to the applied torque X the cosine of the off-axis angle. If you have one of those little U-joint adaptors in your socket set, try it at 90 degrees; it won't turn the nut.

Since the cosine of 15 degrees is 0.965...., effectively at that small angle, your torque will probably be within spec. Torque to the high end of the quoted range if it makes you feel happy.

[Lark Parker]

Thanks Gord for the precise help. I was uncomfortable with my way of deduction.
I had also thought about the extreme of 90 being an isometric exercise. But I got sloppy in thinking when I remembered the sine of 90 was 1.000 so I used 10 degrees off 90 for the sine function. Something about the calculation kept nagging at me.
Although using 80 on a sine function probably yields the same numerical answer as 10 on the cosine.
Your thinking is correct, mine *lacks precision. (*Euphemism for I was wrong.)

If you use a China built universal joint, the 90 exercise does not hold in the real world as some guys can break one.

I was also lacking in precision about the torque wrench being invented before the last century. My computer says it was invented in 1918.

[JoeHall]

Oops. Lark, I now see you were serious in the above. Hopefully, you did not take seriously, anything I said above. It was meant to be tongue in cheek. For all except head bolts, flywheel bolts, and the like, I just tighten till it feels about right. But I know that does not address your question.

Joe

[Lark Parker]

Joe,
No harm -- no foul.
I delete about half of my responses on this forum because the
computer does not relate sarcasm or even humor very well.

[nvonada]

Lark,
What year is your manual? I might pick one up just for that torque table. The torque wrench may date to 1918 but there is not a single torque value anywhere in my 1941 manual.

Nathan

[63 R2 Hawk]

If all else fails, use common sense and any one of several torque table specs such as found in Machinery's Handbook or http://www.engineershandbook.com/Tables/torque3.htm.

[Lark Parker]

I agree that handbook is good and it's hardly worth the price just to buy the manual for the torque specs.
Here's another http://www.pirate4x4.com/tech/billav...lts_signed.pdf
with a short course in bolts, nuts and washers.
Use one of the suggested tables and just choose the bolt rating (most are grade 5), the diameter, and the thread(coarse or fine).
Such tables are universal and what Studebaker probably used to build with and write the shop manual.
For what its worth I used the 1955 Shop Manual since my 39 Manual is at the President's storage site.
The 1955 manual is excellent and better than some of the later shop manuals. My opinion only.
Since I was dealing with studs and not bolts (with the grade marking) I would have assumed grade 5 had I been using a general table.