Idea on cranks.....

C

Chevalade™

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For those that need the absolute least friction losses.....why not try an idea that was introduced into the cooking arena.

If you look at the Santoku knife...it has very slight indentations running perpendicular to the edge of the blade....

The reasoning for this is so that it creates a pocket of air in what it is cutting through to reduce the suction created by the flat surface of normal blades.....thereby reducing the friction cause by the suction......

The faster the blade moves the better it works.

I think the same idea could be applied to cranks....with a similar result......

Any thoughts on it? I may be just full of it too....but i though I would  throw it out there.
 
Are you talking about doing this to the counter-balance weights?

Im not sure if a few indentations would work, but also think about golf balls and their indentations.  I remember years ago (mid to late 90's) people were experimenting with putting those sorts of dimples in all kinds of things and finding out it actually worked.  One that pops out in my head i remember seeing in a popular mechanics, and they put those indentations on a baseball bat.  the guy swinging was regularly able to swing it faster, and since there was no weight reduction to the bat, it would translate into hitting the ball further.  So obviously it works.. its just how would you translate that to a crank?
 
I thought he meant the bearing surfaces.....I think it would trap grit and trash...but what do I know.

Maddog
 
The scallops are called grantins (spelling?) and I think they would work. I also think Maddog has a point about getting dirty. So my thought is on a high maintainence race engine they might work. Street motor might lead to dirty oil problems
 
I was just thinking some more about the "golf ball" dimpling on the weights.  basically the idea with it is that the dimples hold more air and create a bigger boundry layer, essentially reducing the drag.  But i wonder if you could actually do that to the weights.  I mean, you shot peen certain items to make them more durable, but how would bigger "dents" affect the crank strength?  sure would be an expensive test, and something that would probably only be done by high hp engines where they would use that extra 1-2hp.  But the big thing i wonder if dimpling the leading edge/sides of the weights would be more effective than knife-edging it.
 
The dimple effect seems plausible as well....

I think it could be drilled in the weights......as part of balancing....

A person should be able to remove very little material, and achieve the same results.....

Be intresting to do a before and after.....
 
i do not see where it would hurt anything to try it

However i do know how they do the comp/prostock/indy honda cranks and what they end up doing is making the leading edge wider and the trailing edge narrower so it makes its own path.

Also remember that most high end engines have the oiling sealed off somewhat in an attempt to keep the oil out of the rotating assembly.

  Dry sumps and sophisticated oiling systems along with multiple scrapers are the finite stuff that you do to get hat last 1/2 hp here and there.

  Again if you want to try it what would it hurt ?

  JW
 
I'm thinking a dremel or a small 90 deg die grinder with a dot style stone might be the best way...and to do a random style pattern.....any thoughts on tools/design/bits?
 
I certainly dont think random is good....lay it all out and center punch them

  TI
 
The gain is likely to be small so some precise before and after testing would be in order to confirm anything. Also, higher RPM engines (like the Indy engines) would seem more likely to benefit from this than regular street engines. My  :twocents:

Good luck if you decide to go through with it though. :crossfingers:

Eric
 
I think your time spent would yield you a lot more gain If you just took weight off the crank, turned the counter weights round, knife edged and bull nose the crank, have the parting lines ground smooth on the counter weights and bored all the rod throws out, .  After you get rid of 14-15 lbs of iron and make it slick in the wind (and oil ) you'll get real world horsepower gains that can and will be felt in the seat of the pants and on the dyno.  :twocents:

Tom
 
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