YarnMaster
Yep, you got it ... I don't like being rushed
Originally Posted by V8Ian
Panda's ya man Dave, as long as you're not in a hurry.
YarnMaster
Now then Cooper, of course I believe you ...
[quote=cooper;1073179]That wouldn't be a bit of sarcasm now would it Cooper? It least my steering damper matches
[/QUOTE
Not at all,swallows tongue,it is a vast improvement on the boring silver number offered from new.Dances with glee that perhaps she believes me.
YarnMaster
Thanks Deano ... yep, makes sense. However, where the hell did I put my knitting?
....................................If the threads are damaged or covered with dirt, you can feel some resistance before the fastener actually pulls the parts together. This is called "run-down" torque. If you can "feel" that 5 Nm of run-down torque is needed to make the nut turn on the bolt, then add this 5 Nm to the recommended torque. Sometimes you can hear a clicking sound and feel the nut "stick" before it gets to full torque. Then, as you apply more torque, the nut does NOT move until you reach a higher value of torque. The cure is simple. Just back-off half a turn, and once it has broken free, tighten it again with a steady and smooth action....................
© Karl S. Kruszelnicki
Pinched this off the ABC website.
Talk about a long winded way to explain a simple principle.
What they are saying is that when you have a dirty or damaged nut/bolt that you are tightening, some of the force you are using to tighten it with is being used up to overcome the friction caused by the dirty/damaged nut/bolt. When you are tightening a nut/bolt to a specified torque you need to apply extra torque to compensate for this 'wasted torque' in overcoming friction. In the example given above they've determined that friction to be 5 Nm. I guess you'd determine this by feel when you're experienced but until then try this. If the nut/bolt isn't "pulled up" and you can feel resistance as you tighten it you'll be able to read the amount of torque required to overcome this resistance on your torque wrench. Add this to the required torque and bobs your uncle, the nut/bolt is now done up to the correct tension.
Hope that makes some sense.
Deano
YarnMaster
Is the SIII an "interference" engine or a "non-interference" engine? Just wondering ...
ChatterBox
SubscriberWhich engine ? 4 cyl petrol, 4 cyl diesel, 6 cyl abominationIs the SIII an "interference" engine or a "non-interference" engine? Just wondering ...
You'll find out quick enough if you break the timing chain !!
Deano
ChatterBox
SubscriberLow compression engines like the petrols probably OK, the diesel though............Is the SIII an "interference" engine or a "non-interference" engine? Just wondering ...
Only guessing really.
Deano
YarnMaster
Well, mine's a 2.6 standard Leyland petrol ... does it make that much difference if it's an interference engine, or not, in the schemes of things? (as far as breaking the timing chain & the ensuing damage to the engine?)
God I need to get a life ...
Which engine ? 4 cyl petrol, 4 cyl diesel, 6 cyl abomination
You'll find out quick enough if you break the timing chain !!
Deano
YarnMaster
Oh crap ... did I get it wrong?
Youth?
ChatterBox
SubscriberDon't know much about SIII 6cyl petrol engine, I'm just assuming here that its that horrible overhead inlet side exhaust thing LR used in the late SII's. But it really doesn't matter as far as your question goes, I'm just being nasty to LR's (excuse for) engineers.Well, mine's a 2.6 standard Leyland petrol ... does it make that much difference if it's an interference engine, or not, in the schemes of things? (as far as breaking the timing chain & the ensuing damage to the engine?)
God I need to get a life ...
If you lose a timing chain/belt its always better, and a lot less expensive, not to have the valve gear and pistons colliding. Or if they do only a little bit. Its the degree of interference thats the issue. No interference is best, but with interference, slightly bent valve stems can be straightened but valve(s) through top of piston(s) is terminal.
Deano
RoverLord
galling is essentially the removal of metal when 2 pieces of metal are forced to slide along each other. its usually a microscopic effect and is generaly more noticable when a corse hard material (like say a steel file) is dragged across a softer metal (like say aluminium) if you try this you will notice that the alluminium gets stuck in the file, ITs the same deal with threads on a bolt. This is usually bought about by not cleaning out the threads of the nut/bolt/stud or when there is defects in the production of either. At the microscopic level its not a big deal when it becomes noticable it is. First off because where theres thread damage you have a potential fail point (stripping the threads entirely or jambing and snapping the fixture) but worse it has the potential to skew your torque setting.
nice segway to rundown torque.
Rundown torque is the amount of torque required to have a threaded fastner draw the components the fastner is supposed to hold into contact BEFORE you start torquing it up. In theory if you know the rundown value you add that to the final desired torque.
ITs a pain in the ass when you do have to deal with it and its part of the reason that the phrase "torque in sequence and in stages" came about. In day to day use if you use the correct tensioning pattern and do the bolts up a little bit at a time then run over them all with the torque wrench a second time you will usually eliminate rundown torque issues. HOWEVER. That assumes a perfect world scenario If you have a warped piece that needs to be pulled flat, if you have a dodgy thread, some crap in the hole, suffer galling on the way in have thermal difference issues, have a badly made nut or bolt, are using the wrong nut/bolt or any other of the plethora of things that can pooch the motion of the fixture (nut/bolt/stud) that can add some big numbers to the rundown torque.
Heres where it gets dangerous. If you try to measure the rundown torque and you find it and like your supposed to you add the rundown torque figure to the desired torque figure you can wind up over stressing the fixture or the component and it'll fail.
My advice.
If you encounter rundown torque while assembling a component (bolts that you cant wind in by hand) find out why and sort that problem out. IF theres a good reason for it (its a bloody big bolt, its a nyloc nut, its holding something heavy that wants to sit on the threads) mount the thing in place and put in some dummy bolts wind them down to your initial torquing value (remember in sequence in STAGES) then remove and replace them one by one with the correct fastener.
Where possable the use of guide dowels to locate the component first and a little brain one about the tensioning sequence will eliminate about 90% of the problems you find with rundown torque thats not caused by thread abuse.
Dave
"In a Landrover the other vehicle is your crumple zone."
For spelling call Rogets, for mechanicing call me.
Fozzy, 2.25D SIII Ex DCA Ute
TdiautoManual d1 (gave it to the Mupion)
Archaeoptersix 1990 6x6 dual cab(This things staying)
If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
If you think you're in front on the deal, pay it forwards.
Posting Permissions
| Search AULRO.com ONLY! |
Search All the Web! |
|---|
|
|
|
Reply With Quote
Bookmarks