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Thread: Torque with a crows foot
12-26-2006, 07:17 PM #1
I need to turque some head bolts and a couple will require a crows foot for access. How does that affect the torque values? Is there a formula based on the centerline length of the adaptor?
12-26-2006, 07:40 PM #2
Check here, they work thru an example. I was a litle confused by "Y" and "T" but see the proof farther down the page, T = ultimate fastener torque at the crow's foot. Y = torque applied to the click or beam wrench.
12-26-2006, 08:42 PM #3
To understand the logic view the mechanism as follows:
First, assume your pivot point at the center of the nut. The torque applied to the nut is the force on the troque wrench handle times the distance from the nut center to the point of applied force. This is L + E. There are no shunt force paths. So T = (L+E) * F.
We do not know the force. But we can determine the force from the torque wrench reading. Y is the reading of the torque wrench. Thus, F = Y / L.
Thus, T = (L+E) * Y / L .
L and E can be in any units so long as both are the same and T will be in the same units as Y.
12-26-2006, 09:09 PM #4
You don't have to make any correction if you put the crow's foot at 90 degrees to the handle of the torque wrench.
12-26-2006, 09:23 PM #5You don't have to make any correction if you put the crow's foot at 90 degrees to the handle of the torque wrench.
12-26-2006, 09:23 PM #6
From Winchman's example you can torque to the required value with no correction factor. To find the correction factor, torque at 90 deg and then straight on and note the difference in readings.
12-27-2006, 03:16 PM #7
In the Nuke industry, we are required to use a crows foot at 90 degrees when torquing safety related equipment in the plant.
12-27-2006, 05:18 PM #8
There is something to remember in Matt's formula. "E" is not the length of the adapter. It is the increase (or decrease) in length between the wrench drive center and the adapter drive centerline as measured PARALLEL to "L". At 90 degrees, the value of "E" would be zero.
With a 6" adapter at 45 degrees, "E" would not be 6". It would only be the added length measured Parallel to "L".
12-30-2006, 02:26 AM #9
Well I got to the project today. Of course my Snap-On neighbor wasn't home so I had to buy a cheapo crows foot from the auto parts store and it was dead square with the drive socket so you can't turn it over to change orientation. The head bolt I need to torque is under the rocker arm shaft and of course the adaptor wouldn't plug onto the extension while it was fully engaged on the bolt head. One with about 1-1/2" centerline woul be nice. I worked up through the sequence and estimated the torque on the one bolt with an open end until the adaptor lined up. I lucked out and it all came into alignment so I was able to use it properly for the final go round. Thanks for the input.