Torque wrench adapters for cyl. bolts

I finished rebuilding my topend last night (first time) and decided to make an adapter out of an old extension and brand new 'cheap' wrench. I used it at 90 degrees so no conversion was needed.

I like houndogs idea! However the cheapest and easiest thing to use would be a "crows foot". all it is is basically an open end wrench, minus the handle and it has a square hole in it to accept a socket wrench (torque wrench). As mentioned before as long as you hold the wrench 90 degrees to the bolt no conversions are needed. If you hold it inline with the bolt you'll need to do some math.

JP57, the 90 degree deal is based on the need to equilibrate forces in any static body. If an object is not accelerating, then all forces acting on the object, or free body, are in equilibrium. 

When you apply force to a torque wrench at 90 degrees to the work object, you are causing a couple things to happen. First, there is a translational force created parallel to your line of force. This force is opposed by an equal force from the cylinder stud, pushing back along the extension in this case. Secondly, you create a torque, or moment, about the extension. In order for the extension to not begin rotating in space, an equal and opposite moment is created at the other end, by the resisting torque of the nut.

Once the angle between the torque wrench and the extension deviates from 90 deg., then the translational force has two components - one is parallel to the extension, and the other perpendicular to it. It's that perpendicular force that creates another torque, in addition to the one you read on the wrench. Depending on on the configuration of the wrench & extension, this torque can be either additive or deductive to the indicated torque.

 

'equilibrate' ?

Ms. malaprop...what does that mean? ;)


The longer the lever, the more the leverage (the shorter the less). At 90º the lever isn't longer, so the torque seen by your wrench doesn't change.

re: crows foot.

Fine, if it fits. The amount of metal around the open jaws of a crows foot is more than the amount around a boxend. I recall reading on an earlier thread regarding this that a crowfoot didn't fit.

If it DOES fit, you won't get as much rotation out of it due to the same 'moh metal' thing.

Oh...just 'cuz it's a theory doesn't mean it ain't so! (this one is so)

The torque reading is accurate only if the adapter is at 90 degrees and you pull at 90 degrees to the torque wrench handle. If you pull along the wrench handle you will be reading high or low.

I was looking through a bolt catalog at work and found some data on bolt tensioning accuracy.
With a skilled fitter:
Tightening by feel was within +/-35%
Torque wrench +/-25%
Turn of the nut method +/-15%
Load indicating washers +/-10%
Fastener Elongation measurement +/-3-5%
and strain gauging accurate to +/-1%