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Thread: Torque wrench + Crowsfoot

  1. #1
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    Default Torque wrench + Crowsfoot

    Hi, if i use a crowsfoot socket with a torque wrench, will I get approx the same reading? or will it be way off?

  2. #2
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    BM,

    Good question!

    I think that the torque applied to the nut/bolt will be the same as if you'd used a socket. I'll even go further, I think that the length of the crowsfoot has no effect, ie a 12" long crowsfoot would give the same torque as a normal short one.

    The reason is that the drive end of the torque wrench is not constrained, and torque applied at one end of a beam should cause an equal and opposite torque at the other.

    But I could be wrong...

    Ian
    All of the gear, no idea...

  3. #3
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    Good morning

    Went through this problem on the head bolts of an old Cherolet 6 cylinder engine about 50 years ago. As I recall the answer involves measurieing the distances from the bolt center to the swivel pin in the wrench handle then reduce the torque by that ratio, not sure about doing this with the newer "adjustable - click when it attains the preset torque" wrenches.

  4. #4
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    May 2006
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    Default

    Depending on the position of the crows foot it can either amplify things or deduct from the torque value,

    in order to figure stuff like this out just go to extremes --- what if you had a crows foot as long as the torque wrench and you positioned it to come all the way back to your handle?
    You would be applying nothing, all the fastener would end up doing is catching side load.

    What about 180 degree's the other direction? Twice the torque...

    Sooooooo ----------- if its the only tool you can use then position the foot 90 degree's from the torque wrench head, put it in the direction so that it won't slip off while loading it --- not perfect but good enough.

  5. #5
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  6. #6
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    Default

    The reading will be different but close.

    Torque is a function of force at a distance. To not complicate things, lets say the axis of crows foot and torque wrench are aligned. Also, that the square drive is a perfect fit in the crows foot, making them mechanically one element; the distance that force is applied then is that of the crows foot combined with the torque wrench .

    If the crows foot was massive, say 24" and the torque wrench 24, force would be being applied 48" from the rotating axis whereas the torque wrench would only be measuring at 24"...hopefully that shows there is an affect. But in reality the crows foot is short, say 2". So what the torque wrench is measuring at 24" is really a force applied at 26" to the rotation axis - there will a difference but slight, approximately 1/12
    .

  7. #7
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    Default

    Interesting thread.

    Ok, try this idea. Plug a universal joint iinto the crowsfoot's socket, and another one onto the torque wrench. Put an extension bar between the UJ's. Move the centreline of the square drive of the torque wrench so that it is exactly in line with the bolt.

    As we are using perfect, friction-free UJ's and the torque wrench is lined up with the bolt, the effect is identical to replacing the crowsfoot with a socket.

    I think...

    Ian
    All of the gear, no idea...

  8. #8
    Join Date
    Sep 2010
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    if using a "click" type wrench with a short crowsfoot surely there will be very little difference?

    torsion type wrenches.... well i never liked them so never bought one or learned to use one......

  9. #9
    Join Date
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    Lomita, SoCal, USA
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    Old Tiffies pictures showed a Warren & Brown click type torquewrench. I've got those in 1/4", 3/8" and 1/2" drive. They're my only Aussie tools, but I really like them more than any other for repetitive torquing operations. I don't think they are imported to the U.S., but I got mine when I worked at Cosworth Racing. Every year, when we would send a crew to support the Champ Car series at Surfers Paradise, we would send someone with orders for these wrenches for anyone in the shop who wanted one. We had a torque standard in the shop that assemblers had to check their wrenches against, and even though the adjustment of the W & B is set by eye, it would be more accurate and repeatable than a Snap-On click type.
    Davis

    "Nothing is impossible for the man who doesn't have to do it himself"

  10. #10
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    I think that if you used a crowsfoot that was 12 inches from the center of the square drive to the center of the bolt in the crowfoot, you would have a 2 to 1 ratio.

    20# indicated on the torque wrench would be 40# on the bolt.

    If you turned the 12" crowsfoot around, you would have a reading of zero.

    The same would hold true for a standard crowsfoot.

    You would have to use a ratio based on the working length of the crowsfoot as a part of 12 inches.

    This of course applies to foot pound torque wrenches, but the theory would be the same for inch pounds or metric.

    Brian
    OPEN EYES, OPEN EARS, OPEN MIND

    THINK HARDER

    BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

    MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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