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Torque wrench for fluid fittings?

R

roee

Well Known Member
What are people using to torque the fittings on fuel lines, etc? A normal torque wrench that takes sockets obiously won't work (or am I missing something?). Seems like you'd need something with an open end so the tubing won't be in the way.

Descriptions, pictures, advice, ridicule, all welcome. Thanks!
 
You need a set of "Crow's Foot" wrenches - picture an open end wrench without a handle, but with a square hole to snap on a rachet or torque wrench.

Paul
 
Got it

Thanks!

Picked up an 11/16" crow's foot wrench ($4 at Sears).

Of course this lengthens the arm of the torque wrench, and therefore affects the torque. I think using the crow's foot at a right angle to the wrench should make the difference minimal. Otherwise, I'd have to do some math to calculate a modified torque setting.

FYI osxuser, the 120 in-lb torque was quite a few more "flats" than hand-tight. Not sure if that's what you meant by "snug".
 
Here's the Math

From the "Standard Aviation Maintenance Handbook"...

T = Actual (desired) torque
Y = Apparent (indicated) torque
L = Effective length lever
E = Effective length of extension

T X L
----- = Y
L - E

torquezh8.jpg
 
roee said:
Thanks!

Picked up an 11/16" crow's foot wrench ($4 at Sears).

Of course this lengthens the arm of the torque wrench, and therefore affects the torque. I think using the crow's foot at a right angle to the wrench should make the difference minimal. Otherwise, I'd have to do some math to calculate a modified torque setting.

FYI osxuser, the 120 in-lb torque was quite a few more "flats" than hand-tight. Not sure if that's what you meant by "snug".
Click to expand...
"Snug" would be the point where the majority of the movement stops when tightening. In other words, If your tightening the B-nut down with a wrench, the point that "snug" would be is the point where you would want to start using the torque wrench, when most of the relative movement stops, and it starts taking more effort to turn the wrench.

More difficult to explain than I thought it would be.
 
roee said:
Thanks!

Picked up an 11/16" crow's foot wrench ($4 at Sears).

Of course this lengthens the arm of the torque wrench, and therefore affects the torque. I think using the crow's foot at a right angle to the wrench should make the difference minimal. Otherwise, I'd have to do some math to calculate a modified torque setting.

FYI osxuser, the 120 in-lb torque was quite a few more "flats" than hand-tight. Not sure if that's what you meant by "snug".
Click to expand...

You're right....at a right angle to the wrench, the difference IS minimal. It's 0, in fact :D
 
Just to be clear, putting the adapter at 90 degrees is not creative. It accepted practice. If you're really worried, run it through the formula and you will get

(T x L) / (L + E) = (T x L) / (L + 0) = TL/L = T = Y

where E is the distance along the handle's axis that the mouth of the crowsfoot is located relative to the socket drive.
 
Last edited:
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