[TR] Torque using crow's foot adapter

[Tom Note]

Jeff and JC :  Thanks for your advice. I feel more confident now.

Tom

----- Original Message ----- 
From: "Jeff Scarbrough" <fishplate at gmail.com>
To: "Tom Note" <tom628 at verizon.net>
Cc: "TR List" <triumphs at autox.team.net>
Sent: Friday, May 20, 2016 7:43 AM
Subject: Re: [TR] Torque using crow's foot adapter


> Torque is measured as force times distance.  In the case of a socket,
> the distance is to the pivot point of the wrench, which is also the
> pivot point of the bolt. With a crow's foot, the pivot point is
> offset, so the torque ~might~ be different.
>
> If you think back to your high school trigonometry, or back to your
> Greek classes, you will remember that Pythagoras noted that the square
> of the hypotenuse of a triangle is equal to the sum of the squares of
> the other two sides.  So you could easily figure out the effective
> torque by finding the length of the hypotenuse, which is the distance
> from the handle pivot to the pivot of the bolt, by knowing the length
> of the wrench, the offset of the crow's foot, and the angle of the
> crow's foot to the wrench.  If you wanted to be clever, you could
> calculate an angle for the crow's foot that would result in the same
> hypotenuse as the length of the wrench handle, so the reading would be
> true.
>
> But consider two things:  1)  The offset of the crow's foot is very
> small compared to the wrench length, so the error in measurement
> should also be small; and 2) a beam-type torque wrench has a pivot
> point on the handle so the length is consistent, but a click-type
> wrench length can vary depending on where you hold it (I think - the
> click point may be the limit of length, I've not yet taken one apart).
>
> Consider the worst case - the offset adds length to the wrench.  Given
> a 24 inch wrench and a 1 inch offset for the crow's foot, and a 15
> ft-lb torque setting.  15 foot pounds is 180 inch pounds.  180 inch
> pounds divided by 24 inches is 7.5 pounds applied at the end of the
> wrench.  But, you are actually applying it to a 25 inch wrench, so 7.5
> pounds times 25 inches is 187.5 inch pounds, or 15.625 foot pounds.
>
> Not that different, and probably within the calibration of the click,
> or your eyeball, depending on what type of wrench you are using.
>
> Now, it's early on a Friday morning, so I expect corrections, but I
> think that's right...  I always torque the propshaft to two grunts and
> an elbow pop anyway.
>
> Jeff Scarbrough
> Corrosion Acres, Ga.
>
>
>
> On Thu, May 19, 2016 at 11:45 PM, Tom Note <tom628 at verizon.net> wrote:
>> Hi All:  I installed a new U-joint at the driveshaft- trans junction and
>> intended to torque it to the book value. However, i have not been able to
>> find a way to get a conventonal socket of any size in on either the bolts 
>> or
>> the nuts.  I have a set of "crows foot" adapters which I used (for the 
>> first
>> time), and torqued the nuts to the mid-point of the spec, range. I kept 
>> the
>> open end  in line with the axis of the torque wrench, and it only adds an
>> inch or so to the OAL of the wrench, Is there a correction factor that
>> should be applied in figuring the the torque that shoiuld be applid with 
>> the
>> wrench to get the true torque at the bolt or nut?  Also, it would appear
>> that these adapters only work when in line with the wrench axis, right?
>>
>> Thanks,
>> Tom
>>
>> ** triumphs at autox.team.net **
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