can u give the reason for crank shaft failure and suggest way of improvimg it?

Answer 1

Nearly all crankshaft failures are due to high-cycle fatigue, which is what can happen if the alternating bending stresses exceed the metal's endurance limit. There's much more to be said on that subject, but you'd probably get bored before I ran out of space, so I think I'll spare you.

The root causes of this problem can vary, so I would need to interview you and see at least a photo of your crankshaft to have any hope of narrowing it down to one. It could have been inadequately designed in the first place, or it could have been overstressed by a modified high-performance (non-stock) engine, or it could have been improperly surface-hardened, or it could have lost lubrication, overheated and softened one or more of the hardened areas, or it could have been nicked or dented during installation, causing a stress concentration, or it may have been out of balance or bent, resulting in higher than intended alternating stresses in subsequent service. The list goes on and on.

Improvement? Assuming there were no secondary defects like those listed above, and short of redesigning the crankshaft and/or its hardening, one common short-term fix is to shot-peen the journal fillets. This imparts compressive residual stresses, protecting the surface from bending-induced alternating stresses.

Answer 2

It's almost impossible for crank shafts to actually break during normal motor operation, unless the forged piece was defective to begin with. A more common mode of failure is from inadequate lubrication, so that the journal bearings could seize up and the engine can overheat or stop. Once that happens, the engine has to be taken apart and the bearings replaced, and crankshaft remachined. That's the reason why attention to oil level and frequent oil changes is the best insurance against that.

Answer 3

Uneven wear of the piston rings can cause uneaven wear of the cylinder leading to crank shaft breakage. This may be due to wrong oil pumping into the cylinder.
In modified for performance engines sometimes crank shaft brakage occurs due to crankshafts not reinforced or balanced properly when modifying the components like piston heads, pistons etc;.
Generally if excess power is put on the crank shaft more than the specified limit crankshaft brakage can occur.

Answer 4

Crank shafts can fail for many reasons. To high of oil pressure, to low of oil pressure. Crank jurnals being to soft. Crank and related parts not balanced. Main bearing junals out of round. Rod jurnals out of round. You wont you crank shaft to last, have block main jurnals aline bored. Rod jurnels aline bored, Have rods pistons and wrist pins balanced as a unit.Also crank and all related parts balanced as a unit. Crank and rods should be magnifluxed or X-Rayed for structrual flaws. Block should be four bolt mains. Crank steal billet. Bearing inserts washed in clean solvent and then soap and water blow dryed. Cleanlyness is next to Godlyness when building a engine. Bearing clearance should be checked for proper clearance.When torquing down bearing caps work back and forth untill proper torque is acheaved. Running to high of oil pressure can wash out the bearings. I always use the oil I'm going to use in the engine when installing bearings. I have built a lot of engines and have never had a crank failure. When I build an engine it is blue printed from top to bottom. When your ready to fire up your new engine, insert a long frat tiped rod into the oil pump shaft and turn it with a drill untill oil pressure is built up. Install Disturbutor, set timing and fire it up. I may not be able to spell well but I can build and engine to last.

Answer 5

if the crank shaft in the moter fails then there is no way to help it the moter ect.. time to R & R (Rip it out & Replace it) i would sugest the hole moter and then cahnge the oil now and then......