Torquing with a crow's foot - Chevy and GMC Duramax Diesel Forum
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post #1 of 7 (permalink) Old 08-30-2018, 03:54 PM Thread Starter
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Torquing with a crow's foot

Torque wrenches are designed for use with sockets. When using a crow's foot instead of a socket, like when doing the injector pressure pipes going to the injectors, what difference does that make to the torque delivered to the bolt? Since the force is not applied on-center, like with a socket, it will be less - since the torque is applied away from the bolt. In effect, you are levering the torque, in the negative direction - meaning it will take a higher torque reading on the wrench to deliver the required torque to the bolt - because of the negative leverage.

Any smart people out there, anyone?
I'm wondering if this in going to stump you fellas.

BTW, number 8 below is a crow's foot.
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Last edited by Area 51; 08-30-2018 at 03:59 PM.
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post #2 of 7 (permalink) Old 08-30-2018, 04:01 PM Thread Starter
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Number 8, below, is a crow's foot.
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post #3 of 7 (permalink) Old 08-30-2018, 04:04 PM Thread Starter
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Did I mention number 8 is a crow's foot.

Apparently we can't delete our own posts. Brother.
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post #4 of 7 (permalink) Old 08-30-2018, 06:33 PM
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Quote:
Originally Posted by Area 51 View Post
Torque wrenches are designed for use with sockets. When using a crow's foot instead of a socket, like when doing the injector pressure pipes going to the injectors, what difference does that make to the torque delivered to the bolt? Since the force is not applied on-center, like with a socket, it will be less - since the torque is applied away from the bolt. In effect, you are levering the torque, in the negative direction - meaning it will take a higher torque reading on the wrench to deliver the required torque to the bolt - because of the negative leverage.

Any smart people out there, anyone?
I'm wondering if this in going to stump you fellas.

BTW, number 8 below is a crow's foot.
If it is placed at 90 degrees to the torque wrench there will not be any effect on the applied torque. I googled it and came up with this formula

E- Effective length of extension - measured along the centerline of the torque wrench. L Lever length of the wrench - center of grip to center of drive. T(W) - Torque set on the wrench. T(E)- Torque applied by the extension to the fastener.

T(W) = T(E)* L/L+E
T(E) = T(W)* (L+E)/L

Supposedly instructions from a Husky torque wrench

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post #5 of 7 (permalink) Old 06-16-2019, 02:03 PM
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Quote:
Originally Posted by Jimc295 View Post
If it is placed at 90 degrees to the torque wrench there will not be any effect on the applied torque. I googled it and came up with this formula

E- Effective length of extension - measured along the centerline of the torque wrench. L Lever length of the wrench - center of grip to center of drive. T(W) - Torque set on the wrench. T(E)- Torque applied by the extension to the fastener.

T(W) = T(E)* L/L+E
T(E) = T(W)* (L+E)/L

Supposedly instructions from a Husky torque wrench
This is accurate. In the torque manual that is used by Navy Aviation, they provide this same formula. If the crow's foot or torque adapter (dogbone) is extended past the head, the actual applied torque is higher than the reading on the wrench. If it is set below the head of the torque wrench, the applied torque is less.

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post #6 of 7 (permalink) Old 06-16-2019, 05:32 PM
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Torque applied with a crows foot will be slightly higher. Due to the slight arm from center of, bolt or nut, to center of extension into crows foot. However it should still be within range of the torque specs. Unless you are shooting for maximum torque then it will probably still be within specs. Most consumer torque wrenchs are 3 to 5 %.
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post #7 of 7 (permalink) Old 06-16-2019, 07:21 PM
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