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#3312352 - 03/14/14 11:23 PM Crankshaft Design
MolaKule Offline

Registered: 06/05/02
Posts: 16377
Loc: Iowegia - USA
It wouldn't be the Holidays if it weren't for the Turkeys, the Fruitcakes, the hams, and the mixed nuts. But enough about my relatives. smile

#3312367 - 03/14/14 11:59 PM Re: Crankshaft Design [Re: MolaKule]
Shannow Online   content

Registered: 12/12/02
Posts: 30915
Loc: Oz
That's a lot of information in a small space, thanks.

#3312379 - 03/15/14 12:22 AM Re: Crankshaft Design [Re: MolaKule]
expat Offline

Registered: 05/12/09
Posts: 4756
Loc: Canada
Thanks for posting.

But to put things in perspective:

Austin Seven two bearing crankshaft:

Amazingly they will run 6k rpm

#3312388 - 03/15/14 12:37 AM Re: Crankshaft Design [Re: MolaKule]
edhackett Offline

Registered: 06/09/03
Posts: 1698
Loc: Sequim, WA
Here's Alfa Romeo's take on a 4 cylinder crank from the mid 50's through the end of production of the Alfa designed engines.

Never attribute to engineers that into which politicians, lawyers, accountants, and marketeers have poked their fingers.

#3312418 - 03/15/14 01:46 AM Re: Crankshaft Design [Re: MolaKule]
Shannow Online   content

Registered: 12/12/02
Posts: 30915
Loc: Oz
There were some initial problems with bolt-on counterweights, which resulted (as one Formula One designer told me) in "several deep holes being dug in the surface of a few racetracks". There are tensile and fatigue stress issues, as well as the inevitable fretting between contact surfaces and the requirement for highly developed fastener technology.

Having observed more than a couple of high cycle fatigue failures of turbine blades, with horizontal shaft rotating equipment, there is obviously a 2g difference in the centripetal acceleration at 12:00 versus 6:00.

Most of the genuine high cycle fatigue (calc'd at 170x10^6 cycles from crack to failure in most) ones that I've seen have ultimately failed at around 6:00, as evidenced by trajectories and consequential damage.