Picture of a broken crankshaft

Ignoramus8881 fired this volley in news: snipped-for-privacy@giganews.com:

Single-cylinder tug boat engine?

Lloyd

Looks too heavy compared to the throw for an engine. Is it off some kind of compressor or press? Looks like it hasn't been out of service long, not that rusty.

Pete Keillor

That was my reaction, too. Those big engines typically have a long stroke. This looks more like the crank for a mechanical press.

Great observation!

This was from a punch press.

This is how most Chicago people use most equipment, in general.

From a punch press

Gunner Asch fired this volley in news: snipped-for-privacy@4ax.com:

Yep, it was. But some of those old 'pancake' engines had short strokes (high ratios, but short strokes).

I've seen a couple of 36" piston-diameter tug motors with strokes of less than 10". Flat heads, though, so still good compression ratio.

Lloyd

I have no idea, I simply observed that crankshaft on the ground, I do not know the story. My guess is not much happened to the operator.

Can you explain this crystallized metal issue?

"Crystallized" is an old and incorrect explanation based on the grainy surface of the break, which follows the existing and usually visible grain boundaries.

However some solid metals do recrystallize over time, on a -much- smaller scale.

We studied fatigue failure in college but what I learned may be outdated. Here's a more recent overview:

Recently an ME who was investigating a fatigue failure told me that stresses below 1/2 of the ultimate tensile strength can be assumed to not cause fatigue, unless the manufacturing process causes unintended stress concentrations.

-jsw

I layed such a press with 15k forklifts...

Thank you for sharing this fun and educational story.

That's vaguely reminiscent of the trailer spare tire which got away while traveling down the freeway in LoCal...

Looks like a stamping press to me.

In a shop where I worked, a somewhat amusing lunchtime activity was taking clapped-out bearings, washing all the lube & dirt out of them, holding the inner race between thumb & index finger, spinning them up to some insane sp eed with an air gun & putting them down in the parking lot. They'd go some pretty impressive distances.

We can't let this trick go by without comment. First, if you turn the bearing to the side while doing that, the gyroscopic effect will side-load the bearing and likely burn your fingers, unless you instantly let go, in which case the bearing will run off and hit something at a very high speed.

If you put your finger through the shaft hole and it side-loads like that, it may seize and rip off your finger. However, your finger will have the ride of its life.

Third, if you succeed it getting it to spin up freely, you will, eventually, learn about the fracture mechanics of hardened 8000-Series steel, while the outer race explodes in your face.

'Just a caution.

In a (woodworking) shop where I worked , I epoxied a quarter to the concrete floor . Asshole floor sweeper used my best chisel to take it up . He did it on a day I was out ...

uh, with all due respect, I think that both of you share some culpability on that one. d8-)

I had the corner of a $20 bill (just a corner piece, not the whole bill) sticking out from under the anti-static mat on my workbench. I'm sure lots of people looked but ;-)

When I was in high school I brazed wood screws to several coins. They were screwed into several obvious places where I worked on the farm. Nobody ever got those up in the few years I was around there...

So you were one of *those* kids, huh?