cranks cranking around

[lyonsy]

about to do some crank shaft grinding
what i was looking at doing is cleaning up all the crappy casting marks on counter weights and big ends (mainly matching the castings up as they are lower on one side to the other)
i was also going to round off the counter weights and give a nice radius on them.
after that the crank will be sent to the machine shop to be checked for phasing of the journels and made to be spot on then balanced up.
ive seen the crank shaft lighting topic but i dont have the equipment or money to do it that way but iam more after just making the best out of standerd crank.
anything else worth doing that i can do my self with a die grinder and a 4in grinder.
and yes ill have the old bearings over the journels and wraped up to prevent any damage.

 

[rbohm]

8) knife edge the leading and lagging edges of the counterweights.
radius the oil galley openings.
have a generous fillet ground where the journals meet the counterweights.
polish the crank, then have it shot peened.

 

[lyonsy]

have a generous fillet ground where the journals meet the counterweights
unsure what you mean by this
iam also trying to advoid shotpenning if possible so can you polish the crank and not lose strenght.
and yes the stock crank will handle what iam throwing at it

 

[StrangeRanger]

iam also trying to advoid shotpenning if possible so can you polish the crank and not lose strenght.

shotpeening strengthens the crank.

 

[rbohm]

8) if you look at the crank where the journal meets the counter weight, you will see a small radius there. that is called a fillet. the larger this radius, the stronger the crank. remember that where there is a corner, you have a stress riser that weakens the metal as stress is concentrated in that area. reduce the corner, and the stress is relieved, and that strengthens the area. you dont need a much larger fillet, just a bit to substantially reduce the stress riser.

and as SR said, shot peening increases the strength of the base metal. remember to shot peen after polishing.

 

[lyonsy]

ive only got a budget of 4g to build the engine and i cant justify the extra expense as the standerd crank and rods will handle double the power and boosted.
yes id like to but cant afford it when it will do the job with out failure for the life of the crank and rods.

so dont polish the crank undless having shotpen done

thanks for the filliting info anther thing onto the list for the machine shop

 

[wallaka]

Won't taking the casting lines off strengthen the crank? Less stress risers, etc?

 

[rbohm]

so dont polish the crank undless having shotpen done

8) actually you can polish without shot peening the crank. the only reason i said to polish the crank before shot peening is that some will peen the crank, then polish it, and that rather defeats the purpose of shot peening. wallaka is right, polishing the crank in and of itself increases strength by removing stress risers left by casting flash and the mold parting line.

 

[lyonsy]

nice so ill polish the crank and and the inside of the block.
doesent have to me a mirror perfect finsh just cleaned up?
is it worth doing the rods as i dont really want to take to much metal off the rods.

 

[StrangeRanger]

If you're going to polish the rods, you have to have them shot peened too. A great deal of the strength lies in the surface. If you remove that surface you absolutely must restore it by shot peening

 

[lyonsy]

yep i thought it was something like that so ill leave the rods alone then.

 

[StrangeRanger]

What is your objection to shot peening?

If you polish your rods and prep your crank then have everything peened, you end up with a much stronger bottom end.

 

[lyonsy]

i havent got any objection at all id love to do cant afford it the machining is going to be close to 2.5g.
and parts will make up the 1500 easy.
on the rebuild i probly will re balance polish and shotpeen.
problem is the engine that was ment to be this one pumped up lifter ad droped a valve and destroyed the engine bad enough iam not using any bits in this one
bits that arnt to bad are going into a street engine iam rebuilding but i whouldent trust them under race loads.
plus iam also building a new car in which a majority of the money allocated for it is now the new engine.
thats the problem.

 

[Anonymous]

Do not grind and polish any forging without shot-peening afterwards (and don't get it hot while grinding). Find the best tuner in the area and ask him if there is a shop in the area that has real expertise in shot-peening, because there are shops that don't know how to use the equipment. You probably can't hurt and might help a casting by grinding/polishing out the stress-risers, though shot-peening would still help. Eagle has some relatively low-buck racing rods that are better than any shot-peened stock rod, and probably don't cost a lot more than buying ARP bolts and getting all the work done on the stock rods. Rods are one place in a racemotor where spending some money could save you grief later.

 

[addo]

I think our member "xdee" would have a good lead on shotpeening. My experience has been that it's only a little dearer than sandblasting.

 

[Thad]

You might think about Cryo, should have a similar effect to shotpeening.
Got a price of $90 plus shipping.
Maybe available close enough that shipping does not hurt so bad.

 

[lyonsy]

i never really got the hole cryo thing its supose to bond the particles together better or something sorta like anneling.
but how do particls that are frozzen move together when frozen?

 

[Lazy JW]

...how do particls that are frozzen move together when frozen?

Because nothing is totally "frozen" at any temperature above Absolute Zero. Absolute zero (-459.69ºF) is when ALL molecular movement stops.

Cryogenic treatment is used for various things with reportedly good results such as rifle barrels, chipper knives, whatever. It seems to help items that have repeated heat/stress cycling. I have never used it myself.
Joe

 

[Anonymous]

Cryo is controversial, too. Northrop reported extending the life of drillbits, milling cutters, etc.. Boeing said it was a waste of time. But, useful or not, cryo isn't a direct substitute for shot-peening, which achieves a different effect (and about which there is no controversy); ideally you would do both.

 

[StrangeRanger]

Cryo gives a very uniform grain structure and minimizes the residual stresses, this reduces the potential failure points of the part. It does little or nothing to improve the tensile strength of the part. Shot peening causes a compressive stress in the outer surface of the part while leaving the core undisturbed. This substantially increases the fatigue life of any part, such as a conn rod, subject to cuyclic loading.

So, you would grind and polish your rods, then have them cryo treated, then have them shot-peened