The torque wrench will click off at the chosen value around its own drive point, which is the centre line of the fastener in normal use. If you put a crows foot on, It will click off at the same force around the same point but you are multiplying that force by the length of the crows foot and therefore increasing torque at the fastener. So if you had a foot long wrench, set at 50lbft, in normal use will click off when 50lb of force is applied. If you then add a foot long crows foot (it’s a big ‘un) then the torque wrench will still click off at 50lbft, around it’s own reference point but you’ve double the length of the lever on the fastener. The wrench will still click at the same force, but the turning moment at the fastener will now be 100lbft.
* Good question. Let me try and paint the picture in my minds eye. Let's imagine the torque wrench was shaped like a screw driver applying 20 ft lbs of rotational torque thru a 3/8 square drive where the blade would be. As its a torque wrench it clicks off at 20 ft lbs. Applying that 20 ft lbs to a crow's foot would have leverage advantages due to the offset from the centre of the bolt because its a crows foot. 20 ft lbs is always the limit applied to the crows foot as the wrench clicks off. But in the case of a torque wrench shaped like a screw driver it wouldn't matter what angle the crows foot was to the screw driver shaped torque wrench, the force on the crows foot is 20 ft lbs regardless of angle. Now, my point is does it matter if the rotational force measuered by a torque wrench is from one shaped like a screw driver or one with a lever at right angles. Isnt the force that reaches the 3/8 square drive of the crows foot always the same and that any leverage advantages are wholy measured within the dimensions of the crows foot. If the answer to that is yes then surely the angle of the crows foot to the torque wrench is inconsequential. TB P.S. I read the Wikipedia article and it explains leverage well, but here we are limiting leverage advantage with a torque wrench.
I'm liking the right-angle approach , as mentioned by folks up-thread If I dial-up 40Nm on the torque wrench , and have the crowfoot at 90 degrees to the wrench handle , then I'm going to put 40Nm of torque on the bolt .... .... more or less , within the accuracy of the tool . Any other angle is going to involve some maths .... or " cyphering " as Jethro used to say ( Beverley Hillbillies anyone ? ) Can we all agree on that much , at least ? Is the torque wrench "sensing " ( or reacting to ) the actual torque applied to the bolt , regardless of what gubbins is between the wrench and the bolt ? No, it is not .... it's reacting to the load at the point where the 3/8" drive meets the crowfoot This was what I meant in the first post .... ..... about the risk of overthinking the problem
Try lifting a floorboard with your fingers,then try with a crowbar.Youre exerting the same force but with leverage,it makes it easier.
The video is partially correct but not completely. It finished up here and tell you that this is correct. It is not.For simplicity, say the torque wrench is 1m long and you want a torque of 2NM. So, that is applying a force of 2 newtons at the handle of the torque wrench. As the crowfoot has length no matter what position it is relative to the wrench, the torque is still greater at the nut then where it is measured on the wrench AND the wrench needs to be in a position where is will actually turn the nut (or try to).
By George I think you are agreeing with me. Moving the crows foot 90 deg to the wrench does not alter the force to the nut. TB
Difficult to explain - it's a tricky problem. First everyone needs to stop using 'force' and use 'torque' - pure torque (as if you're using, say, a motor). Start with the application of a pure torque - i.e. a pure rotational effort, with no 'levers', then transmit that pure torque somewhere else in the system and that torque will remain the same because you've not added any more moment or leverage. The instant your torque wrench clicks you'll be adding the additional moment that is so confusing. I am sure I'm right in this. Anyway, just test it within the range of torque-wrench accuracy. Instead of the nut that you're trying to tighten with your system of offsets, doglegs, etc pop another torque wrench there instead and see what happens...
Yes! I no longer care! Incidentally, it was touched on earlier: Ducati cylinder head bolts that you can't get a socket on. And so you might use a crowsfoot but I believe that there is a specific tool that Ducati do that is similar. Does anyone know if Ducati give the torque settings assuming that you are using this tool?
Always has and always will be the way to use the extended crowfoot, ring etc is at 90 degs to the torque wrench. I've been on the tools for over 30 years, working on pissy size stuff like bikes, to 1000Nm torque wrenches with 2 blokes hanging off them. Even instructions in makers manuals will give that clarification when maybe 1 out of 8 fasteners has limited access and they have supplied the extension tool as oem service kit for the awkward bugger. Torque setting will remain the same for the group, not be adjusted for the awkward one. It may look weird and get a lot of theoretical discussion going, but 90 degs is where its at, as @nelly said from the start.
The clue is in the name. 1 foot pound is the torque applied by applying 1 pound of force to a lever 1 foot long, or more accurately, at a distance of one foot along a lever. If you attach a crows foot spanner in line with your torque wrench, you are applying your 1pound of force to a longer lever, so it will no longer be 1 foot pound. To make it stay the same amount of leverage, the total length of the lever needs to remain at one foot when measuring from the end of the torque wrench to the centre of the bolt. 90 degrees may not give a spot on measurement but as long as the crows foot extension is not too long, it’s going to be plenty close enough
Yes they do , it's the standard torque setting , as stated in the factory manual The reason being that the tool puts the torque wrench and the cylinder head nut on a common axis ..... no offset means that no correction is needed .
So to make it simple, tighten an easily accesible bolt to 50 ft/lbs with your torque wrench, and then put crows foot on at 90 deg and see if it is still at the same value or will turn more. Then you will be 100% sure.
just tighten the bastard until you can't turn it any more, and then spray a bit of wd40 and hit it with a hammer to get it to undo.
Torque Wrench Extension Calculator Norbar’s torque wrench extension calculator is now available as an app to download free on iPhone and Android. An invaluable tool for engineers, the torque extension app calculates the exact torque wrench setting value for required level of torque to be applied. When you put an extension on a torque wrench (e.g. a crow foot or a dog bone) the torque applied to the fastener increases as the lever arm extends. The calculator will work out what value you should set into the wrench to achieve the required fastener torque. The following formula has been used: M1 = M2 x L1 / L2 Where: M1 is the torque setting of the wrench M2 is the actual torque applied to the nut L1 is the normal length of the wrench L2 is the extended length of the wrench PRODUCT SELECTOR[/paste:font] FIND A DISTRIBUTOR DOWNLOAD CATALOGUE WHAT OUR CUSTOMERS SAY DOWNLOAD OUR APPS FAQ USE CALCULATORS Manufacturing & Assembly Oil & Gas Transportation Energy Generation Aerospace Mining & Refining
I thought I was convinced by the 90 degrees thing , but now I've done thunk myself out of it ..... Drat and Double Drat ! Even at 90 degrees , the turning force is still being offset , although it's by a smaller amount , and maybe it can be ignored ? I don't know what accuracy the makers claim for their torque wrenches . I suppose +/- 10% would be a fair guess ? I'm "Indecisive Dave" .... again !
Simply measure from the end of the torque wrench to the centre of the bolt/stud/nut with and without the crowsfoot extension in place at 90 degrees. I’m pretty sure it will be within a Few mm, which will be well within the tolerance range of the torque wrench. It’s the effective length of the lever that matters, not the shape of it. Imagine the lever you are using is a solid triangular plate with the bolt attached to one corner and you applying pressure to another corner. The third corner is irrelevant and that’s what the 90 degree angle between the extension and the torque wrench is, an irrelevant corner. It’s the straight-line distance between the fastener and the end of the torque wrench that matters. If the measurement between those two points is the same or very similar with and without the extension in place, the leverage will be the same and so will the torque applied before the torque wrench clicks off.
