27.083333333 You might want to round it. conversions It's really just 325 divided by 12, but thought I'd post the conversion link for you anyway as it's useful.
Hey thanks alot Ken i appreciate it,i wasnt sure what it actually was the same as saying 12"= 1 ft. Thanks:TU:
Torque is defined as force acting at some distance from the center of rotation. Torsion is defined as a twisting deformation of a body about an axis in which straight lines that are initially parallel to the axis become helixes. Torque is a physics term with a defined formula, (Torque= Force X Lever Arm) and a unit of measurement whereas torsion is a state of being. As in your crankshaft is in torsion (really it does twist even if only a small amount) when you hammer the throttle and the dyno measures the amount of output torque. Any other questions? Is the mid-term open or closed book?
somebody's had WAAY TOO MUCH coffee this AM! Ken put DOWN the coffee cup!!:spank: No, thanks for the link for conversions, very handy!:TU: :grin:
Ken, here is a question for you since you are on a roll right now.... A lot of the newer engines use torque to yield bolts. I know how to install them and I understand what they are doing by stretching the bolts, but when you torque a normal head bolt for example, don't you get the same result?? I mean, a torque to yield bolt at 100 ft/lbs plus 20 degrees of rotation should have a torque that can be measured when it reaches its final postion (why not just go with the final torque figure, whatever it works out to?). any thoughts?? later Tim
OK, I'll take a crack at it, but I'm sure someone out there has more practical knowledge. First of all, let's define what yield is. Yield is the point where something is stretched and when the force is released it does not return to it's original shape. It is said to have gone through "plastic deformation". Every bit of stretch up until the point of plastic deformation is said to be in the materials "elastic range". Now another important principal to understand is "elongation". This is basically defined as how far you can stretch or bend something until it breaks, otherwise known as reaching its "ultimate strength". Think of bending a piece of glass versus a piece of plexiglass and you'll get the picture. One other tidbit is to realize that regardless of yield, ultimate, and elongation values, like materials behave essentially the same when they are in their elastic zone. That is, for every .001 of stretch of your bolt (TTY or Std), it resists with a specific force up until yield occurs. Torque-to-yield (TTY) bolts are designed to yield when fully tightened. That is once fully torqued, they stretch never to return to their original shape once untorqued. Once yield happens on all your head bolts, the clamping force between the bolts is pretty even (see below). Now because these are intended to yield, the designer must have taken into account both a yield point and an elongation (amount of stretch before fracture). At a certain tightening load, the bolt is supposed to yield. As you continue to tighten, the bolt is supposed to stretch. On a regular head bolt, the bolt was most likely designed with the yield point in mind (little regard to elongation). That yield point needs to be higher than the maximum torque value with a significant safety value, say 2 or more. That means this bolt won't hit its yield point when torqued to specification. The bolt shouldn't permanently stretch when properly torqued. It does stretch, but in the elastic zone (before yield). If you take the bolt out, it's its original size once again. Further, as it is always intended to be used in its elastic range, the designer most likely did not take into regard elongation beyond yield as much as the TTY bolt designer did. That is, the regular bolt might hit its yield point, begin to stretch, then immediately break as it has very limited elongation after yield. The TTY bolt on the other hand, will stretch a long way before fracture occurs. OK, now to finally answer your question. When materials are in their elastic range (prior to yield), the resultant force curve is rather steep for every bit of stretch. For the sake of example, let's say that for every .001 of stretch, our TTY bolt resists by 500 lbs. This continues up until the point of yield. That yield occurs before the specified torque value. Now once the bolt starts to permanently stretch, it might resist by only say 100 lbs of force for every .001 stretch. In other words, the curve flattens out. The force (now clamping our head) increases gradually now. This means that for a given range of torque the range of clamping force is narrower than for our standard bolt that's in it's elastic range still. The regular head bolt is still resisting by 500 lbs/.001 stretch right up to the specified torque. This making sense?? I've attached a stress-strain curve to look at. Think of stress as your head clamping force and strain as the bolt stretch. The regular bolt operates in the straight line portion of the curve- lots of force change for little stretch. The TTY bolt works in the portion after yield- relatively little force for the same amount of stretch. And the reason you don't want to reuse TTY bolts is that they stretch and become thinner everytime you tighten them. The thinner they are, the weaker, naturally. Now, for a disclaimer, it's been over twenty years since I took a strength of materials or machine design class. I am not a fastener designer. I was an engineer, now I'm in management, meaning a mandatory chunk of brain required removal. Who knew you could say so much about a bolt?
What is the air speed velocity of an un laden swallow? (Sorry, I couldn't resist!) :bglasses: That's a handy site you linked to there Ken. :Smarty:
Interesting stuff Ken. I always enjoyed physics. Question regarding TTY bolts. When the block is drilled and threaded for the TTY bolts is it done differently to accommodate them? If the TTY bolt can only really be used once, does it affect the threads in the block after multiple torquing?
I always had open book tests. Strength of Materials, Mechanical Design, Dynamics, Thermo.....hmmm haven't thought about that stuff in awhile. Engineers sure do have a way of overcomplicating things?
Ken, No, It was an excellent explanation and I learned from it. :Smarty: I remember when I replaced the struts on the '90 Riv I owned, the GM manual said to not re-use the bolts that attached the strut to the knuckles, which made no sense to me. I had my suspicions, but I went ahead and re-used them anyway of course, with no problems. I figured if it was so important not to re-use them, Monroe would have given me new ones in the box. But now I realize what I suspected was true and have a better understanding of why I probably shouldn't have re-used them. I was in no way intending to knock you with the "un-laden swallow" comment if that is the way it came across. :beer
