TheSamba.com :: View topic - Does torque value change when using adapter and/or crowfoot?

Sun Jun 09, 2013 9:04 pm

Hi,
I just torqued my new ball joints on my 69 Beetle using a 1/2" drive with a 3/8" adapter to a crowfoot and I wonder if this set-up alters the end torque value to the nut. I'm thinking just the crowfoot would as it extends the length slightly. If so, do I torque higher or lower to compensate?
Thanks!

Sun Jun 09, 2013 9:28 pm

if you extend the crows foot as a continuation of the wrench it increases the leverage, so for any given torque setting (for click style wrench) you exert more torque to the fastener. the length of the crows foot is small in relationship to the wrench though so the difference is not much. i wouldn't worry about it on ball joints, if you were torquing case bolts or rod caps it would be more of a concern. it the crows foot is at a right angle to the wrench the differential is even less. actual formulas can be accessed on MotionPro's site, they make the adapter wrenches for motorcycle cylinders where a torque wrench cannot directly fit, they have angle and differential values, you may have seen these adapters, they are usually a double ended box wrench (mine is 12mmx14mm) and in the center of the handle is the 3/8" hole for ratchet or torque wrench.

Sun Jun 09, 2013 9:49 pm

I think this wil help:
http://www.engineersedge.com/manufacturing_spec/torque_wrench_1.htm
{Fixed the link....}

Sun Jun 09, 2013 11:16 pm

Yes, a crowsfoot extension can lower the required torque setting on the wrench*.

T2 = (T1 x L) / (L + E)

T1 = required bolt torque
T2 = torque wrench setting
L = length of torque wrench (between the center of the torque wrench's socket head and the center of its hand grip)
E = length of extension (between the center of the crowsfoot drive socket and the center of its jaws)

Make sure your torque values and lengths have the same units: inches <-> inch-lbs, feet <-> foot-lbs.

So for example: Bolt needs 50 ft-lbs and you have a 18 inch long torque wrench and a 1.5 inch crowsfoot. Convert lengths to feet: 1.5 ft, 0.125 ft.

T2 = (50 x 1.5) / (1.5 + 0.125) = 46.1 ft-lbs for the torque wrench setting.

*This equation only applies if your extension points straight out of the torque wrench. If you attach the crowsfoot at a 90 degree angle to the torque wrench, then bolt torque equals the wrench torque setting (T1 = T2) regardless of how long the crowsfoot is. So if you can actually get to the bolt with the crowsfoot at 90 degrees, I recommend it so you don't have to do the math.

Mon Jun 10, 2013 10:13 am

Thanks for the replies guys. (Ashman - your link goes to a blank page).

The second part of my question - does the socket converter/adapter going from the 1/2" drive to 3/8" affect the torque produced by the wrench or just the crowfoot?

Also, I was able to do the torquing at a right angle with the crowfoot so it seems I should be ok. Bentley says 36-51 ft lbs for the ball joint nut. Am I reading this right? I took it to mean that it is an acceptable torque value within this range so I set it at 45 ft lbs. But why give such a wide range and not a set value? I don't understand that.

Mon Jun 10, 2013 11:43 am

Socket -----NO. Just the CF.
Marvin

Mon Jun 10, 2013 11:59 am

PJ_1600 wrote: Thanks for the replies guys. (Ashman - your link goes to a blank page).

The second part of my question - does the socket converter/adapter going from the 1/2" drive to 3/8" affect the torque produced by the wrench or just the crowfoot?

Also, I was able to do the torquing at a right angle with the crowfoot so it seems I should be ok. Bentley says 36-51 ft lbs for the ball joint nut. Am I reading this right? I took it to mean that it is an acceptable torque value within this range so I set it at 45 ft lbs. But why give such a wide range and not a set value? I don't understand that.

No, your 1/2->3/8" drive adapter (or a socket extension) has no effect on the required torque. A long drive adapter/extension just makes it harder to keep everything lined up to get correct values.

The ball joint stud is mostly held in by the friction of the interference fit between the tapered stud and hole. The lower limit will get you that amount of fit, the upper limit will keep you from cracking the hole in the spindle. Doesn't much matter where you are in between. As a common example, ball joints with castle nuts and cotter pins will have a minimum torque spec + whatever additional torque it takes to line up the next hole.

Mon Jun 10, 2013 4:14 pm

Hey - thanks very much. That makes sense plus now I know I didn't make a mistake on torquing it to 45 ft lbs.

Mon Jun 10, 2013 4:32 pm

I've got to chuckle...... Torque is such a poor way to measure fastener stretch.

The variables are astonishing! New fastener, Used Fastener, Dry Fastener, Lubed Fastener, Lubed with What? Fastener Material, on and on and on.

At best it's an educated guess. There aren't many affordable options available. The most frequently used option is torque angle.

You are actually measuring stretch of the fastener...... Not always an easy or practical thing to accomplish.
They have stepped washers, yielding washers squeezing out an indicator, etc.

Don't fret too much and lose too much sleep over a 1/2" of increased torque wrench length using a crows foot. What you are measuring is "iffy" at best.

This is all very important and much discussed in the Amusement Industry where human lives are at stake and how important the use of quality fasteners installed in a proper manner really is.
Next time you are in that Zipper or on a roller coaster....... Pray that the operator/owner is aware of quality fasteners.......

Dave

Mon Jun 10, 2013 4:43 pm

PJ_1600 wrote: Thanks for the replies guys. (Ashman - your link goes to a blank page).
Thanks for pointing it out. I've fixed it above.

PJ_1600 wrote: Also, I was able to do the torquing at a right angle with the crowfoot so it seems I should be ok.
Just so you know, the above formulas only apply when the crowfoot/extension add to the overall length of the torque wrench. If you mount the crowfoot at a 90deg angle to the wrench you are not really adding to the overall length.

But, since you are still within the range of acceptable torque, you should be okay.