Torque Adaptor Calculator

[DwayneGorniak]

Okay, maybe I have been drinking too much lately. But has anyone ever played with the numbers on the torque calculator?: http://www.forddoctorsdts.com/publications/torque_adapter_calculation.pdf

 

I use this calculator all the time. But I have noticed that if you increase the length of the torque wrench and leave the adaptor length and the torque spec the same, the torque calculation increases. The apprentice I used to work with had a fancy shmansy Snap-on digital vibrating make your wife happy torque wrench. It was 13.5 inches long from the center of the anvil to the center of the handle. My old beat up click type Snappy torque wrench is 10.25 inches long from the center of the anvil to the center of the handle. The end spec for my wrench with the torque spec set at 8.8 and my adaptor at .8" is 8.2 foot pounds. But if increase the length to 13.5, the end result increases to 8.3 foot pounds.

 

So with that being said, shouldn't a longer torque wrench with more leverage decrease the end result of what you set your torque wrench at? /forums/images/%%GRAEMLIN_URL%%/scratchhead.gif

[Keith Browning]

Hey, No kiddin! That can't be right. I played with it and came to the same conclusion. I will have to look into that further...

 

ON EDIT: I tried three other torque calculators and they all did the same thing. THe math is right and the formulas are the same.

 

I need to wake up before trying to think about this. /forums/images/%%GRAEMLIN_URL%%/coffee.gif

[SteveS]

OK, I know that I've been drinking too much, it helps me ignore my wife's blonde-isms. But it seems to me that the length of the torque wrench handle should not effect the torque applied to the fastener. i.e. If set at "x" ft/lbs the force applied to the adapter is the same when the handle is 9 inches long or 18. Isn't it just the length of the adapter that effects the difference between the setting of the wrench and the actual twist applied?

[Keith Browning]

Think of a torque wrench handle as a lever. The longer it is, the less force that is required at the handle to achieve a specific torque specification than a shorter torque wrench. This would apply to any wrench actually. In other words, the 13" wrench SHOULD require a HIGHER setting than the 11.5" wrench to achieve the same torque. So when we plug the numbers into the calculator and change the length of the wrench the output is changing in the opposite direction than we expect.

 

/forums/images/%%GRAEMLIN_URL%%/scratchhead.gif

 

AHH! The above is true for a wrench and a socket because a socket is at the fulcrum or pivot point. When we are making a calculation for use with AN ADAPTER the torque spec is offset by the adapter itself. The torque spec still measured at the fulcrum but now the fulcrum is BETWEEN the force applied and the output at the fastener. This is the whole reason for the calculator to begin with.