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#1




Is My Computation Correct?
As I'm about to do my DIY project of HG replacement so I read the service manual over the weekend. Then I come to the reinstallations of the cylinder head bolts. The final stage (to make story short) is torque 2632 ft/lb, then turn 75 degrees and another 75 degrees. I called O'Reilly, NAPA, Nissan dealer and they all don't carry the Torque Angle meter. Some guys even never heard of it. So I went searching in the Net for the ft/lb equivalent of 75 degrees angle.
After about 2 hrs. I clicked on eHow page and it gave the equation and answer on Newton's meters which is fine. The second challenge was finding the SIN on 75 degrees angle and I have verified it to be correct. So, if force is applied to a wrench and act as 75 degrees angle, the answer is 103.5 Newton's meters (N*m). It is easy to find the value of ft/lb. in relation to N*m. In other words, 1 Newton meters = .73756 ft.lb. If we multiply the answer above which is 103.5 N*m x .73756 (ft/lb value) = 76.1346 ft.lb., meaning 75 degrees angle is equivalent to approx. 76.1346 in ft/lb conversion. I have to trust eHow first equation is correct or my last computation would be skewed and I am screwed, LOL. Is this a coincidence that engineers pick the 75 degree angle? I don't think so. Mathematics is an exact science. I am not an engineer by a long shot. It just seem easier to work on 75/75 compared to 90/60, 70/80, etc., etc. So, the real question is, knowing the conversion number, if I torque; First Stage: 30 ft/lb, #2: 75 ft/lb, and Third Stage: 75 ft/lb for a total of 180 ftlb, is this a reasonable assumption given there's no info. to compare to. Anyone you're welcome to chime in. Its' appreciated. I'm sure Moderator mpe235 has a lot more tricks under his sleeve, (:. Thx. Last edited by bennyb53; 02272012 at 08:13 PM. 
#2




Unfortunately is not that simple, because you are calculating the linear force applied to the wrench, but what you need to calculate is the torque. In order to find to neccessary torque, you need to know the exact Force you are applying to the wrench and the Radius of the wrench.
Torque = Force * Radius (wrench length) Torque = Radius * Force * Sin(75) In short if you don't know exactly how much force you are applying to the wrench, you wont be able to calculate the exact amount of torque. What I usually do when and angle is require, is find points on my working area that represents 0,45,90,180 dregrees and then move the wrench to the require angle. I hope that helps.
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#3




Sorry I forgot to paste the link. Anyway, the first calculation was if you turn the 0.2m wrench to produce 20 N*m torque, then 20 divided by 0.2 = 100 Newtons. This is the one I have not verified.
How to Convert Torque to Newtons  eHow.com 
#4




Yes, I think a protractor would be just fine. I have also seen a dial type gauge in the Net for about $25. Snap Tools cost in excess of $500. I told him I'm just a garage mechanic. I understand.

#5




Thanks for the link. eHow has a definitely very interesting way to calculate to convert torque to Newtons.

#6




I cannot be certain for sure. If someone says it is flawed that's fine. If I cannot verify I can't rely. I'm going to buy a protractor at Home Depot and do actual test. I will set the torque wrench at 75 ft/lb and tie a fishing line. As I turn the wrench the protractor will be drag and see where the angle is as the torque click at 75 ft/lb. If the results identical then ehow is valid.
Thanks again. 
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