Crankshaft issues

[IdahoRob]

Hearing about Ed's crankshaft breaking along with the rash of high HP engines, thought I'd post a thought that popped into me thick head.

We have been having water pump issues and while looking at the options, I started to think about the stress on the front of the crank and where the cranks have been failing. With the cam, waterpump, and oil pump being driven off the front of the crank.

Now high RPM;

is really spinning the waterpump creating large drag on the front of the crank.

Higher valve spring rates makes driving the cam harder.

High pressure oil pump also adds to the strees on the crank.

Then I thought about how much the rear of the crank is stressed turning the flywheel, and kind of went back to the drawing board

Ideas?

 

[RENODMAX]

It's a good thought nobody has really ever come up with solid reasons. I know Ed and Tony had an electric pump on their orange puller maybe ask him on that issue.

 

[Stingpuller]

Cranks

I really don't think it's from driving the stuff on the front. Look at a small block with a dry sump and really big spring pressure with a much smaller crank nose and I think you mite change your mind. Not sure what the problem is other than we are asking to triple the power output of what it was made to do. Mines not big power like some so maybe I will be lucky. I was looking at old times slips and I have a bunch of passes on this motor. I will be holding my breath this year and hoping for the best. Jeff

 

[RENODMAX]

I really don't think it's from driving the stuff on the front. Look at a small block with a dry sump and really big spring pressure with a much smaller crank nose and I think you mite change your mind. Not sure what the problem is other than we are asking to triple the power output of what it was made to do. Mines not big power like some so maybe I will be lucky. I was looking at old times slips and I have a bunch of passes on this motor. I will be holding my breath this year and hoping for the best. Jeff

So if stronger cranks become available do you think a new crank is going to become a standard part of a high hp build?

 

[TheBac]

Rob, seems to me you also have to take into account the mass of the balancer hanging off the end, dont you?

Would flex in the middle of the crank (thrust bearing area) have any bearing on this?

 

[bullfrogjohnson]

Rob, seems to me you also have to take into account the mass of the balancer hanging off the end, dont you?

Would flex in the middle of the crank (thrust bearing area) have any bearing on this?

The thrust bearings are at the flexplate side of the the crank. To me how every one of these cranks are breaking at #1 it points to the front of the motor.

 

[eds04max]

So if stronger cranks become available do you think a new crank is going to become a standard part of a high hp build?

BINGO!!!.....I think this is what we need to be thinking about.......either a 'fresh' crank or, better yet, a new stroker crank!
I must say, the old crank and it's 'lifestyle' never really crossed my mind during my build. That was probly the last thing on my mind..........and that's what got me!
Some guy's have some other theories that might prove correct.........we'll see.
Rob, whats happening to the w/p's????

 

[Stingpuller]

Crank

I think a stock crank with a big (.140) radius cut in it would live a lot better. Some people laughed at me when I said to cut the crank for smaller rods. If done correctly it will add strength. Look at a corrent pro stock gas motor make over 1400 hp and they run a 1.88 rod. Now something nobody(that I know of) has talked about is the gear to gear drive. I HATE THEM! They add a lot of harmonics to the crank and valvetrain that is not good on anything! Harmonics are bad to the bone on cranks. The better the dampner and the lighter the assembly the better it is to control. Theres something in how the shop does the balance job. They can zero balance or they can over balance to a amount to offset things going on at higher rpm. Larger gas motors are not normaly zero balanced. Jeff

 

[TrentNell]

Could it come down to basic quality control issue's ? there is something missing IMOP because some fail at low HP ( 600-700 ) like Jeremy's ( fishsmith) and others like on Max'd Out have held to 1300hp ?

 

[RPM Motorsports]

Hearing about Ed's crankshaft breaking along with the rash of high HP engines, thought I'd post a thought that popped into me thick head.

We have been having water pump issues and while looking at the options, I started to think about the stress on the front of the crank and where the cranks have been failing. With the cam, waterpump, and oil pump being driven off the front of the crank.

Now high RPM;

is really spinning the waterpump creating large drag on the front of the crank.

Higher valve spring rates makes driving the cam harder.

High pressure oil pump also adds to the strees on the crank.

Then I thought about how much the rear of the crank is stressed turning the flywheel, and kind of went back to the drawing board

Ideas?

Good thinking Rob! Im wondering if we could be cavitating a water pump that is not designed for the RPM and ramp rates, that we are throwing at it. If the pump is cavitating, it could be surging and causing issues with more then just the pump.

 

[TheBac]

The thrust bearings are at the flexplate side of the the crank. To me how every one of these cranks are breaking at #1 it points to the front of the motor.

But if the crank is walking forward and back, and also flexing due to cap flex, wouldnt that put undo stress on the weakest link in the chain (the front)?

 

[fishsmith]

Could it come down to basic quality control issue's ?

I think this is what got mine.

 

[TrentNell]

But if the crank is walking forward and back, and also flexing due to cap flex, wouldnt that put undo stress on the weakest link in the chain (the front)?

Have I missed something ? I never did really study my crank / motor for design issue's but how is the front of the cranks " design " weaker than the rear ? The front of the crank does have a few things it drives but the load is very minute when comparing to what the rear of the crank has to endure ? Maybe thats the issue the rear output / stress is trippled and the front load stays the same ? hell i dont know :rofl:

 

[TheBac]

Have I missed something ? I never did really study my crank / motor for design issue's but how is the front of the cranks " design " weaker than the rear ? The front of the crank does have a few things it drives but the load is very minute when comparing to what the rear of the crank has to endure ? Maybe that the wissue ? hell i dont know :rofl:

I was also thinking that the rear of the crank is "supported" by the converter and pump shaft...but the front is not. Could the balancer weight also be adding a cantilever effect? Hell, Im no engineer.

 

[eds04max]

Mine showed no signs of 'walking' back & forth. I'm no engine-builder........but I couldn't see any signs of anything.........except the broke crank and it's associated carnage.

 

[RPM Motorsports]

Mine showed no signs of 'walking' back & forth. I'm no engine-builder........but I couldn't see any signs of anything.........except the broke crank and it's associated carnage.

Any pictures of the broken area?

 

[eds04max]

here ya' go........

 

[RPM Motorsports]

Wouldnt have a pic looking directly at the broken area from the front would you? Im trying to see how the material looked in the fracture.

 

[RENODMAX]

You don't have to be able to see it for the crank to have walked. It's funny that we've had all these advancements in valvetrain and piston design etc and all we've done for the crank is balanced it covered it up and crossed fingers.

 

[fishsmith]

Mine didn't show any signs of back and forth movement either.