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Dang it... crank fell over

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curtis73

· Hates: Liver. Loves: Diesel
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Discussion starter · #1 ·
I have a 3.75" SBC crank, forged 3430 in a plastic bag. I had it sitting upright and of course it eventually fell over. It landed on a counterweight on a concrete floor. There is no visual damage. I can't even see a scratch where it hit.

Is it wasted? I've always heard myths about storing cranks certain ways and that they're very finnicky. It really seems like BS. For cripes sake, its 70 lbs of forged steel.

Should I just magnaflux it?
 
#4 ·
It's not uncommon for a crank to tip over, especially when there are many stored together. It usually has no effect on the crank. An easy test, if you are concerned, is to set it in the bearings of the main saddle(without the caps) and rotate it. If it is "bent" you will be able to see the variation in the lube pattern as it is spun over. If you are still concerned it is easy to have a shop check it on a crank machine. I remember in the early 70s a big crank grinder would pick up the cores and take them back to the "factory" to be reground. I can assure you they took little care in transporting. They are a lot garder to "bend" than you would think. That doesn't mean to disregard precautions when handling though.
 
#6 ·
The flywheel idea works. But, if you have multiple cranks, storage becomes a problem. Mine are all standing. I always envision a bowling alley type calamity.
 
#7 ·
as long as there are no nicks on the journals there will be no problem.
as for storing them standing them on end is the best if you don't have a rack to store them,laying them down like at a swap meet is the worst,laying down with the sun beating down on it all day can warp a crank and you don't know how many swap meets it's been to.
just my 2 cents
 
Discussion starter · #8 ·
This was the topic of our debate... How on earth can gravity bend, warp, or otherwise change a forged chunk of 75 lb steel??? I've seen thousands of fenders that layed unsupported on their sides for years and didn't magically alter their shape. In fact, storing a crank inside an engine doesn't warp it and its laying horizontal while installed. Couple that with the fact that it deals with thousands of torsional forces per minute and a little bit of gravity doesn't seem like its a big threat.
 
#9 ·
curtis73 said:
This was the topic of our debate... How on earth can gravity bend, warp, or otherwise change a forged chunk of 75 lb steel??? I've seen thousands of fenders that layed unsupported on their sides for years and didn't magically alter their shape. In fact, storing a crank inside an engine doesn't warp it and its laying horizontal while installed. Couple that with the fact that it deals with thousands of torsional forces per minute and a little bit of gravity doesn't seem like its a big threat.
Click to expand...
Sounds like a job for Mythbusters. :p
 
#11 ·
i just read an aricle about a week ago about that wery thing.any crank being stored should be stood on end because they will warp over time.only problem is that i don't remember where i read it for an example.i'll try to remember and get back to you.
 
#13 ·
I don't buy it. I think they're stored on end for space reasons. Think about it, how does a new crank come when you guy one? It comes in a box laying on its side. Can you imagine Summit, Jegs or anybody else storing hundreds of boxes of crankshafts on end? They'd have an incredibly unstable situation. I have a new crank that sat in my back room for six months laying on its side before heading to the machine shop with the block. While at the machine shop they measured and modified it, stuck it in the block and gave it back to me.
 
#15 ·
Theory is just that theory. In theory anything can happen but most likely won't. I go with the crowd in saying if the journals aren't nicked put it in. Of course use standard procedure of checking all clearances and torquing one main at a time and if it doesn't bind your good to go.
 
#16 ·
Here's theory:

An engine sitting will be a better support than an uninstalled crank because the crank is supported more uniformly at the journals and held such that the journals should remain in-line.

Impact loading is a difficult load case to analyse, but for FEA analysis I've seen diffent ways of approximating such as doing a static load case of 10g or 15g, for example. So in this case, if you dropped a 70 lb crank, you'd simulate the impact by analyzing a 700 or a 1050 lb load.

Fenders and crankshafts are quite different things. On a crankshaft you're looking at multiple surfaces machined to size within a tenth (0.0001") which you're after similar tolerances on concentricity, and it's the concentricity that's going to be affected.

For fun if you have a bad crankshaft, put each end on cinder blocks, put a dial indicator under the middle and stand on it.

Now while you'll probably see deflection, you'll probably also see it go back to zero. Permanent deformation happens when you load something past its yield point, which most likely isn't happenning.

What could happen, though, is something more local. If you ding or dent the crankshaft, that could be a stress riser that will prematurely initiate a fracture.

Also, and I need to restate my engineering experience is more suspension related than engine related, but from what I know about stabilizer bars and axle shafts, and I think but am not certain if it applies with crankshafts, fatigue life is often extended with a treatment called shot-peening. The surface of a part that is going to see fatigue may be blasted to induce surface stresses that will increase the fatigue life of the part. dropping a part may degrade the shot-peening.

But this is all theory, and in general I'd be less concerned about forged than cast iron, and the degree to which I'd be concerned would also depend on the degree to which the crankshaft is overdesigned. OEM production crankshafts are going to tend to be designed for infinite fatigue life whereas weight optimized applications such as racing engine crankshafts might be designed to live exactly as long as they're needed, and dropping these will mean the engine won't last a race.
 
Discussion starter · #17 ·
This shaft is an aftermarket chinese crank rated at 750 hp. I think my 400-425 hp shouldn't stress it to much :)

Of course, magnafluxing isn't much of an expense. I'll probably flux it when the whole rotating assembly is in for balancing.
 
#18 ·
Sounds like a job for Mythbusters.



Ayuh,.........

And I'm Betting it would be an Easy 1 to Bust..........

If it ain't Dinged up,.... I wouldn't loose Any sleep over it........
----------------------------------------------------------------------------------------------------------------------------------------------------

i had a crank laying around and tried to warp it ,lot of time wasted and electricity .
machine shop guy i use said they warp laying down , so we took a crank and laid it in the block with bearings and all .
we left the front bearing main out completely .
we then put the top bearing in the main cap only and shimmed the bearing between the cap and bearing .
we tightened the main cap down to the dial indicator read 130 thousand out .
then we took a heat gun and wired it to stay on the first counter weight .
8 hours of heat and the thing was blue in color from heat .
we let it sit for the night and checked it about 20 hours later, nest day.
we then loosened the main cap and the dial indicator returned to 0 .
we rotated the crank and no movement from the indicator .

myth busted , on our part
wouldn't you like to see myth busters try the acetylene and oxygen cannon


when you buy them through mail , do you think the thing is standing up the hole bumpy way .
my opinion ,not yours :pimp:
 
#19 ·
Slipangle, I'm an engineer too. I've never really heard the whole concept of elastic deformation explained much more graphically than you and Burnt Olds, jointly, just did. It may go out of straightness laying outdoors in the sun. But that's because it's locally heated. Let it cool and it'll be straight again. If it ever was.

Pat
 
#20 ·
What would be the difference between storing a crankshaft or camshaft on their side versus the shops or warehouses that store all sizes and lengths of round stock made up of any of a number of different materials?
 
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