That approach certainly removes extraneous moments - i.e. use the Crow's foot at 90-degrees so that its length is the base of an isosceles triangle thus giving the same direct-line moment to the nut/bolt. I'm now fully intrigued by this conundrum and shall work on it!
Hahaha - yes - I got all caught up on the sides being equal! I shall squirm out of it by saying that with the slack in the system and a high aspect-ratio triangle, it tends towards being a tall isosceles triangle. I'll get me rock to hide under...
very good explanation... i was agreeing in my head with the 90 degree making a difference but couldnt have worded like you have... although i must admit, until i started following this thread, i didnt even know what a crows foot was...
Yes and because of that, the longer the crowsfoot extension is, the bigger the discrepancy between the actual length of the torque wrench and the effective length with the 90 degree extension. An isosceles triangle would be better, as there would then be no discrepency but not necessary if the extension is fairly short.
Had this conversation quite a few times at work. A torque wrench is calibrated for its given length, if you alter the fulcrum where it clicks by moving where the torque is applied then the value will alter. So by putting the crows foot on moving where the torque is applied further away from the fulcrum (giving you a bigger lever) then you dont have to apply as much force to tighten the nut/bolt to the torque required, if you apply enough force to click the torque wrench off then you have over tightened the fastener. Another point to remember which is very important is to apply the correct lubricant to the threads and faces of the nut/bolt, this has a huge impact when using a torque wrench, if the thread is tight the torque wrench will click off, but the fastener wont be at the correct torque, not so much when using tension bolts or stretch bolts with angular tension figures, ie 90*, 180* or rotabolts, torque goes out the window with these things, as it all about tension.
Recent posts show differing opinions ..... Me , I'm already easing into my weekend mode , with a rather nice malt , and one of Frank Zappa's mellower moments ... "Lucille Has Messed My Mind Up"
Of course extending the length of the lever by attaching the crows foot at 180 degrees is going to significantly alter the torque applied before the mechanism clicks. However, attaching it at at 90 degrees alters the effective length of the lever very little, so should be perfectly fine.
Totally agree, your not altering the effective length of the lever putting it at 90*, never said it did. ;-) Although I should have said putting it in line 180* will. I knew what I meant anyway. Been on enough courses with work MJI 10 and MJI 19 trade tests
This odd gizmo popped up on the YouTube ..... "recommended for you " list .... it claims to let you put a torque wrench on more-or-less any spanner :- Motion Pro Torque Wrench Adapter Review BTW - it costs more than a full set of crowfoot wrenches though , and it seems to be made of cheese . The 90 degrees theory appears again , but now with a much larger offset ! . We've pretty much agreed in this thread that working at 90 degrees will minimize any errors in applied torque .... ..... but this device is really stretching it , isn't it ?
90 degrees is not absolutely optimal but is close enough with minimal offset. It’s not hard to get the optimal angle for any reasonable offset. All you have to do is draw a simple diagram using a geometric compass to draw an arc from the centre of your bolt with the spike of the compass at or near the end of your torque wrench. Where the length of the offset from the centre of your bolt meets the arc will give you your optimal angle. To be truly accurate, the length of the torque wrench would need to be correct as it would affect the radius of the arc but any error would be small as long as the torque wrench is not extremely short or long.
