patra_is_here Posted June 7, 2013 Report Share Posted June 7, 2013 Phil, isn't rod failure going to be either from forces pushing on the rod or from forces pulling on the rod? is there another load being applied that would lead to failure? Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 (edited) how about the vehicle that you are attempting to accelerate? it always comes down to load. HP or TQ "limits" typically have little meaning. They are loose guides if anything. Edited June 7, 2013 by Funky Phil Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 Take my buddies promod drag car for instance. He absolutley MUST maintain a certain amount of wheel spin during launch otherwise he will drop rods onto the track. Same car, weight, gearing, track, HP & TQ. Just a varied application of load is what keeps it together. Link to comment Share on other sites More sharing options...
patra_is_here Posted June 7, 2013 Report Share Posted June 7, 2013 (edited) how about the vehicle that you are attempting to accelerate? it always comes down to load.I thought that this was implied. the framing of the discussing requires the assumption of there being load placed on the motor, and subsequently to the rods, at which time they experience either positive or negative compression loads. I'm asking you if there is another type of load that I don't know about? is there axial load that causes failure? I'm just asking if there is another type of load experienced by the rod other than compression loads (either positive or negative) Edited June 7, 2013 by patra_is_here Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 hahaha, so vehicle weight is just implied? Probably the most important force, but you guys want to argue stroke and piston weight? should we now argue H,I, and X beams?How about manufactured material? great post Link to comment Share on other sites More sharing options...
Shelby Posted June 7, 2013 Report Share Posted June 7, 2013 I think you all just like to agruee a piston stops and starts moveing twice per stroke once at bottom and once at the top Phill as for your buddys car,, the same thing applys to all of our cars , what do you think would happen if your rear tires did not spin when you droped the clutch @5k parts would be flying every where as to the oreg question which fails first ,, you first must decide on what you call failure ,, most of our engine failures are the result of tuneing when it comes to pistons,, as for rods most of the time the big end egg shapes due to over reving or rod bolt streach now if your talking ford alum engines dang near any thing will bend their rods , one small fart in the intake lol Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 (edited) hahaha everything comes down to application. what does the travel matter? If your generalyzing the automotive industry and the stock untouched internals, the weak link is almost always rod "related". rod bolts always come to mind. That is why people that care ask in hopes of not breaking yours. But then again, you cant know all the limits without the research, all applications and manufacturers vary. Edited June 7, 2013 by Funky Phil Link to comment Share on other sites More sharing options...
Shelby Posted June 7, 2013 Report Share Posted June 7, 2013 hahaha everything comes down to application. goodnight application and material being used Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 application and material being used right, but those are probably implied aswell. haha Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 Phill as for your buddys car,, the same thing applys to all of our cars , what do you think would happen if your rear tires did not spin when you droped the clutch @5k Ummm duh, Id pop a wheelie! That is if the damn axle would hold hahaha! Besides why would I ever drop the clutch at such a low RPM? Am I in traffic or something? Link to comment Share on other sites More sharing options...
Convette Posted June 7, 2013 Report Share Posted June 7, 2013 lol Link to comment Share on other sites More sharing options...
patra_is_here Posted June 7, 2013 Report Share Posted June 7, 2013 hahaha, so vehicle weight is just implied? Probably the most important force, but you guys want to argue stroke and piston weight? im not arguing stroke or piston weight. Link to comment Share on other sites More sharing options...
Funky Phil Posted June 7, 2013 Report Share Posted June 7, 2013 yeah, i really wasnt directing at you. I was more after the relation of torque and stroke that some use to disquise a chocked hotside. G54B is an engine. Very unspecial and simple. Link to comment Share on other sites More sharing options...
jszucs Posted June 8, 2013 Report Share Posted June 8, 2013 oh my goodness.And when did I bring up a short stroke setup? What G54B has a short stroke?If youve had much experience with making decent power with a G54B you wouldnt keep bringing this up.Your piston speed/redline scenario has nothing to do with the numbers an engine will put out. If anything it is a small piece of the puzzle that becomes load. the o/p was asking in general about rods and pistons Link to comment Share on other sites More sharing options...
jszucs Posted June 8, 2013 Report Share Posted June 8, 2013 hahaha, so vehicle weight is just implied? Probably the most important force, but you guys want to argue stroke and piston weight? should we now argue H,I, and X beams?How about manufactured material? great post so you couldn't cause a rod fail or piston fail by just free reving a motor? Link to comment Share on other sites More sharing options...
psu_Crash Posted June 8, 2013 Report Share Posted June 8, 2013 If free revving throws a rod then your engine has pre-existing issues. Link to comment Share on other sites More sharing options...
Funky Phil Posted June 8, 2013 Report Share Posted June 8, 2013 ^ Link to comment Share on other sites More sharing options...
Shelby Posted June 8, 2013 Report Share Posted June 8, 2013 If free revving throws a rod then your engine has pre-existing issues. you don't damage a rod by reving,,BUT you can damage it when you let off.it has to do with the absence of load and the fact the throdle is now closed causeing the engine to become a vacuum pump and not an air pump , this vacuum will create a pulling load on the piston at the change direction point and create high stresss on the rod big end and rod bolts , that along with the ineritia of all moveing parts will add to the vac stress ,enough if reved high enough to axctualy streach the big end and or the rod bolts,, an instant later the brg goes south Link to comment Share on other sites More sharing options...
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