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Thread: How to determine Ft/Lbs?

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    Club Member Beigg's Avatar
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    Default How to determine Ft/Lbs?

    If during the installation for some hardware required for a torque value, yet was only possible by using some degree of angle & extensioning, how would you figure that out? Included below is a quick paint shop image for reference to better help explain the situation.




    Thank you.

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    I don't think the 20 degree angle will change the torque. What will change the torque is the torsional force of the long extensions pushing back against you. That is IF you can keep the constant 20 degree angle on the extensions. If you are swaying back and forth while tightening the bolt, then it is impossible to determine the torque difference.

    If you use moly lube on the bolt threads and seat, you can reduce your actual torque number by something around 20% (I think) over plain oil on the threads.

    Been 45+ years since I got out of college...I forget stuff...Hahaha

    Gary

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    Club Member wrath's Avatar
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    No torque loss unless there is radial deflection. So if you can keep the pile of stuff rigid and you don't have loss in torsion it will be the same.

    In reality, you're going to have some loss depending on components. For example, I lose 10ftlbs in my 48" antique Crapsman 1/2" extensions. It seems rigid until you measure it and you realize a lot of energy is being lost in loading up the extension.

    Can you mock up the same setup using a coupler to an old style needle torque wrench from your normal torque wrench?

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    I have my original Craftsman needle torque wrench in the original box from the 60's if you want to borrow it...

    Gary

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    I always just assumed there was some torque wrapped into an extension. So I always SWAG it and add 5 ft lbs, (assuming a number of around 100 ft lbs). That way you'll probably be within a couple ft lbs and not enough off the mark either way to matter. Have never had a problem this way. I know that's probably not good enough for some applications and it would be good to know for sure how to calculate actual numbers.
    Last edited by DeFormula; 09-10-2017 at 03:05 PM.

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    ill ask where did you get a 6 foot 1/2 drive extension?
    To me, it's a good idea to always carry two sacks of something when you walk around. That way, if anybody says, "Hey, can you give me a hand?" You can say, "Sorry, got these sacks."

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    Club Member Beigg's Avatar
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    The drive head pushed farther "away" from the socket begins with and ends with the torque to be achieved. It's the angle that I'm concerned with.
    IF a crowsfoot were used, or an offset attachment, then that will change the torque value too.

    I'm not looking for the person's need of adding effort, I am trying to maintain the specification needed at the head of the bolt from the socket using a click-type torque wrench.

    Think of it as a driveshaft angle. Pinion angle not only impacts reliability and durability, but it can play around with how much effort is needed to turn the universal joint at the rear end if that degree is excessively pitched.


    Quote Originally Posted by moneypit View Post
    ill ask where did you get a 6 foot 1/2 drive extension?
    two extensions at 36" + the little addition.
    The stability is sound, no wiggling/wobbling around as it is all supported in some way or another.

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    Club Member moneypit's Avatar
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    Quote Originally Posted by Beigg View Post



    two extensions at 36" + the little addition.
    The stability is sound, no wiggling/wobbling around as it is all supported in some way or another.

    ah ok, what the hell are you torquing
    To me, it's a good idea to always carry two sacks of something when you walk around. That way, if anybody says, "Hey, can you give me a hand?" You can say, "Sorry, got these sacks."

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    Club Member Beigg's Avatar
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    mf'n PTO bolts.

    If it is able to apply torque this way, it'll save a lot of knuckle busters and time.

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    Depending on the kwality of your extensions and the amount of torque you're putting through them, you will lose torque in winding them up. Just like how torsion bars in a truck work. A shitty universal will lose torque in it also. The good ones (that use 3 ball bearings, like a CV joint) lose less. This is assuming you're working with a static load (fastener not moving, versus a kinetic load where it would be). If you're measuring when it's moving (dealing with kinetic friction after overcoming static friction) then there is no loss but I doubt you're doing that as it would be pointless.

    When I worked at Michigan Tech I had access to some sweet labs including the Keweenaw Research Center. One of the many hillbilly things I did is experiment with things like that. It made it easier for this dumb EE to deal with Statics and Fluids classes (for smert MEs) when I could do things hands-on.

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