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Need to achieve a high tightening torque

Discussion in 'Technical Q&A' started by swift53, Mar 5, 2021.

  1. swift53

    swift53 F1 Rookie
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    Alberto
    Have to tighten a 41mm nut onto a crankshaft to about 360 ft/lb.
    This has been suggested :

    "360 ft/lbs , roughly 500nm? So 50kg force applied at 1m along steel bar , with socket attached the other end. This can be measured different ways or at different distances eg 2m = 25 kg
    Use luggage scales or fish scales etc , hook end around bar by your own method and pull on bar with scales until you get the magic figure"

    I have some left over 2m, one inch bars, I can weld a 3/4" stubby extension to tip and not kill the socket that way, then go!

    Opinions? To me it makes perfect sense, and much cheaper than another torque wrench...

    Regards, Alberto
     
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  3. Redneck Slim

    Redneck Slim Formula 3
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    Auto parts stores like O'Reilly and Autozone lend tools.
     
  4. yelcab

    yelcab F1 World Champ
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    I used an analog bathroom weight scale.

    I stand on the scale, read the value (for example 200lbs)
    I use a long 1/2 ratchet with a cheater bar to make 3 ft long wrench.
    Push down at the 3 ft mark on the wrench, (horizontally on the cheater bar) until the scale reads 80 lbs. At that point, the torque is 120 lbs times 3 ft, or 360 lb ft.

    Having said all that, I own a 4 foot long 3/4 inch torque wrench for this purpose.
     
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  5. 360+Volt=Prius

    360+Volt=Prius Formula 3
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    That’s really smart. I usually learn from your posts!


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  6. INRange

    INRange F1 Veteran
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  8. flash32

    flash32 Formula 3

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    #6 flash32, Mar 5, 2021
    Last edited: Mar 5, 2021
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  9. fatbillybob

    fatbillybob Two Time F1 World Champ
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    I like using the right tools.
     
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  10. greg328

    greg328 F1 Rookie

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    That torque measuring device is only rated to 147.5 lb/ft. You’ll need a heavier-duty one..




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  11. spider348

    spider348 Formula 3
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    Yep! When I had to rebuild the rear hubs on my former Porsche 930 bought a Large 3/4" Drive Torque Wrench to meet the 250 Ft lb requirement. Then used a lot on my former Center Lock TR. Good Tool!
     
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  13. yelcab

    yelcab F1 World Champ
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    Got plenty of the right tools, including that 3/4 inch 600 lbs monster to the right. That one is used on Porsche axles.

    Image Unavailable, Please Login
     
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  14. swift53

    swift53 F1 Rookie
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    Don't you mean 280 lbs? That would be your weight plus 80, and how do you figure
    "the scale reads 80 lbs. At that point, the torque is 120 lbs times 3 ft, or 360 lb ft." ?

    Thank you.
    Regards, Alberto
     
  15. GordonC

    GordonC F1 Rookie
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    No, he's correct. Consider that when standing on the scale while being able to push down on the wrench, there are two points to provide support to his body weight, which is the maximum vertical downward force that he is able to apply via gravity. If he's not pushing down on the wrench with any force, then the scale reads 200 lbs because all his weight is on his feet, on the scale. If he pushes down on the wrench handle with a force of 50 lbs, then the scale will only read 150 lbs from his feet - the same total 200 lbs downward force due to gravity, but because he is pressing on the wrench with 50 lbs force, only 150 lbs force is being exerted by his feet on the scale.

    Looking at it the other way - how to tell how much force is being exerted downwards on the wrench? It's 0 pounds when the scale reads 200 lbs; if he presses down and the scale reads 150 lbs, then the difference of 50 lbs must be exerted on the wrench. If the scale only reads 80 lbs, then the force on the wrench is 200 - 80 = 120 lbs. If the scale read 0 lbs, then his entire body weight of 200 lbs is being exerted downwards on the wrench.
     
  16. swift53

    swift53 F1 Rookie
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    You are absolutely right, it is the same as weightlessness :)
     
  17. Ak Jim

    Ak Jim F1 Veteran
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  18. vincep99

    vincep99 Formula 3
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    That is fantastic! thanks for the tip.

    Beats the $650 I spent on a torque wrench to tighten the wheels on my Testarossa
     
  19. swift53

    swift53 F1 Rookie
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    I am going to try it next week, will post results.
    Physics vs. electronics...

    Regards, Alberto
     
  20. RayJohns

    RayJohns F1 Veteran
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    You can use a torque multipler wrench or just use an impact gun.

    Ray
     
  21. swift53

    swift53 F1 Rookie
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    Definitely Ray, we use an impact gun on a trucks lug nuts, but in this case it is
    a touch more subtle, and delicate. Would not want to damage the nut / crank threads.

    We are going the 'physics' route, after all simple math, and if they could run the F1 Mercedes
    grand prix cars in the 30's without exotic modern tools, I think we can get at least to an acceptable point.

    Thank you for the tips, much appreciated.
    Regards, Alberto
     
  22. RayJohns

    RayJohns F1 Veteran
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    If it's good enough for Archimedes, it's good enough for me :)

    There's no arguing with Physics.

    Ray
     

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