| Author | Message | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 153 Registered: 2-2002 |
Yep. 7.3... or is it 7.2?  | ||
| Roger Blakeman (Roger)
New member Username: Roger Post Number: 8 Registered: 2-2002 |
Thanks for "all" the info. So the answer is 7.3 ft. lbs., right?? Roger B. | ||
| Lawrence Coppari (Lawrence)
Junior Member Username: Lawrence Post Number: 67 Registered: 4-2002 |
When you exceed the yield point of steel (and I am speaking of stress here), you have exceeded the elastic range. The sample will not revert back to its original size/shape. If you do not exceed the elastic range (the portion of the stress-strain curve that is linear), the sample will return to its original size/shape when the load is relaxed. For the elastic portion of the curve, stress is strain times modulus of elasticity. When you exceed the yield of the material, the modulus of elasticity changes. When you relax the sample that has exceeded its elastic range (plastically deformed), you get a hysteresis loop. The object is permanently deformed, but will have a modulus of elasticity very close to the previous one and exhibits a new elastic range similar to the old one. But the strain does not return to zero. There is a slight weakening of the bolts, once yielded. That is why, say for CV joints, that it is recommended that bolts be replaced every time the things are mounted. | ||
| James Selevan (Jselevan)
New member Username: Jselevan Post Number: 10 Registered: 6-2002 |
An interesting "twist" to the torque discussion is the introduction of the concept of sliding versus static friction. When torquing a "critical" bolt, such as a head bolt, it is prudent to bring each bolt to an intermediate value in steps. HOWEVER, I believe that the last step (to the recommended torque value) should be in a smooth, continuous motion to the rated torque. For example, if the specification for a head bolt is 75 foot-pounds, then several steps of 20, 40 and 60 foot-pounds is appropriate. However, the last application of torque and movement of the lever arm (torque wrench) should be continuous up until an indicated 75 foot-pounds. To stop at 70 for example, and then apply additional torque may take you way beyond 75 due to the static friction (to overcome the friction of the threads at 70 foot-pounds). Here is a question. When retorquing a bolt, is it best to loosen the bolt first, and then smoothly bring it to the rated torque? Under my previous discussion, this would seem to be the appropriate action. However, part of bringing a bolt to proper torque specification is the intended "stretch" of the bolt which is a design characteristic. Is this action plastic - that is, will it return to its original length, thereby allowing for retorquing? Finally - to lubricate or not to lubricate the bolt? That is the question. Some torque specifications call for a ligthly lubricated thread. Just some addition thoughts. Jim Selevan | ||
| Lawrence Coppari (Lawrence)
Junior Member Username: Lawrence Post Number: 66 Registered: 4-2002 |
A Newton is 1 kilogram accelerated at 1 meter/sec**2. Since a kilogram of mass weighs 2.2046 pounds on earth where our acceleration of gravity is 32.174 ft/sec**2 one Newton is a force of 2.2046*3.2808/32.173=.22481 pounds. The 3.2808 is how many feet there are in a meter. Therefore a torque of 1 Newton-meter is .22481*3.2808=.73756 ft-lbf 1 Kilogram-meter is 2.2046*3.2808=7.2329 ft-lbf | ||
| phil hooper (Wolftalk)
New member Username: Wolftalk Post Number: 11 Registered: 5-2002 |
this site is pretty useful: http://www.onlineconversion.com/torque.htm go to their home page instead if you need to convert fluids or something else. | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 152 Registered: 2-2002 |
I suppose since one decanewton is 1.019716 kgf, Ferrari (and perhaps other Euro firms) use daNm as an "interchangeable substitute" for kg-m. (?) I dunno, but it's in several Factory WSMs that I have. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 793 Registered: 1-2001 |
No argument that "nm" would usually represent Newton-meters, but here I think they just made a sort of typo/mistake in Simon's documentation as 10 N-m does not equal 10 Kg-m. | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 150 Registered: 2-2002 |
newton meter (N�m) The International System of Units (SI) unit of torque. Torque, the tendency of a force to cause a rotation, is the product of the force and the distance from the center of rotation to the point where the force is applied. Torque has the same units as work or energy, but it is a different physical concept. To stress the difference, scientists measure torque in newton meters rather than in joules, the SI unit of work. One newton meter is approximately 0.737562 pound foot. | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 792 Registered: 1-2001 |
Simon -- 10 Kg-m (or ~72 ft-lb) is a reasonable torque for the two items you listed, but the "nm" part doesn't make any sense to me either. | ||
| Simon Campbell (Simonc)
New member Username: Simonc Post Number: 20 Registered: 2-2002 |
Perhaps I'm being a bit slow but I can't work this out. My workshop manual for my 400 says, for example, that the wheel bolts and cylinder head nuts should be tightened to 'torque 10 nm (kgm)' so what is this in ft-lb. | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 144 Registered: 2-2002 |
DOH. Slip of the decimal point! It's 7 lb-ft, but 1.0 daN.m (Kgm). One *deca*newton meter. Actually the book calls for 0.9... | ||
| Lawrence Coppari (Lawrence)
Junior Member Username: Lawrence Post Number: 59 Registered: 4-2002 |
That's what my Handbook of Chemistry and Physics says. | ||
| Peter S�derlund /328 GTB -88 (Corsa)
Junior Member Username: Corsa Post Number: 205 Registered: 4-2001 |
I think 10 Nm = 7.3756 lb-ft and 10 lb-ft = 13.5580 Nm Ciao Peter | ||
| Dave Penhale (Dapper)
Junior Member Username: Dapper Post Number: 72 Registered: 4-2002 |
deciNewtonMetres, whatever next, only the Italians could come up with that one! Whatever happened to agreements for SI unit convention? | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 782 Registered: 1-2001 |
Ric -- isn't 7 lb-ft ~ 10 Nm = 100 dNm ? | ||
| Ric Rainbolt (Ricrain)
Junior Member Username: Ricrain Post Number: 141 Registered: 2-2002 |
10 dNm, or 7 lb-ft | ||
| Roger Blakeman (Roger)
New member Username: Roger Post Number: 5 Registered: 2-2002 |
I'm replacing the engine oil sump gasket on my '80 308 GTSi. What should the bolts be torqued to? Just don't want to over do them. Thanks, Roger B. |