Correctly installed rod bolts will be at ~75% of their yield strength. My math is terrible, but for a 3/8" bolt with 180,000psi yield strength I get the following.

area = .1104sq.in.
tensile strength 180,000psi
clamping force = 180,000*0.1104*75 = 14,900lbs*2 = 29,800lbs total for two bolts

If you switch to a really strong alloy, with say 250,000psi tensile strength you get ~20,700lbs/bolt or a total of 41,000lbs. That's a LOT more force. A 7/16" 180,000psi bolt gives 40,600 total clamping force (for both). So, you can see why I only "need" regular CM bolts for the big block and use the $$$ bolts in the small block. BTW, I checked the receipts and those ARP 3.5 bolts cost me approximately $25/bolt (~$400) while the OEM big block bolts were ~$3 a piece (~$50/set)!!!

Rich

 

a couple things
1. are rods made with a bow in themlike this ()
maybe they could straighten out as it hit tdc. i don't know much about these things and to me it would make sense to want to take some load off of the the open circle (i'm sure there's a name for that) that goes around the crank. it seems like it would go elliptical after a while.
2. do engine builders put alot of thought into the size of the radius of that rod hole *technical term*? from the basic physics course i took 4 years ago it seems that the farther apart those bolts are from eachother, the more force they will have to deal with. but if your bolts are up to that, you can make the rods hole radius (techincal term) larger and put less stress on the circumference of the crank that goes in there. if this is true, i wonder if anyones ever graphed it out as the just before failing crank radius vs. the pistons rod radius (or force on the bolts)
3. i'll give this a shot, if i haven't confused you all with my incoherent questions so far.
http://img116.exs.cx/my.php?loc=img1...cissors3ef.jpg
if you made a rod do something like what is pictured, would it work. the red dot is a bolt, sort of like an axle point. when the rod is pulled the crossing design would absorbe more force. the drawing is that good, but the red dot, axle part where the metal would cross would be lower than what is pictured. so then when the rod is pushed down on, a scissor actino would sort of happen. so not only would the bottom open circle be pushed down, wanting to go oval, but the scissor type action would pull out on the sides, reducing the force on that open circle.

 

Wow, cant believe I messed that one up, I knew that too, just for some reason never devided 7/16 in half to finish it up.

Ill work on the rest, my linear algebra is a little sketchy so Ill have to be giving my engineer brother or sister a shout when I get stuck on stuff. Really need to take another basic algebra class again, I really screwed up when I tried college the first time, didnt take it seriously whatsoever, barely passed, but I understood everything in highschool very well.

 

Does anyone know:
Young's Modulus for 8740 steel?
the typical 'free grip lenght' of a bolt
in a rod for SBC?

tia

 

I doubt you will find a young's modulus specific to a grade of steel. It vary's so little by different alloys, heat treatements, ect that the value of 30 Mpsi (30*10^6 psi) is used for all steels. The only time you use a different value is for brittle metals in tension like cast iron.

annealed
Tensile yield strength 60 kpsi
Ultimate tensile strength 95 ksi
2" elongation 25%
Rockwell Hardness 190HB

Tempered
Tensile yield strength 133 kpsi
Ultimate tensile strength 144 ksi
2" elongation 18%
Rockwell Hardness 288HB

I can't help you with with the rod question.

-brent

 

Only 4-bangers I touch have two wheels.

-Mindgame

 

Banger Sisters?

Or isn't legs what you meant by "wheels"?

http://www2.foxsearchlight.com/theba...dex_flash.html

 

They go very very very very far

 

I'd work on those two-Bangers too....








at the same time!

-Mindgame

 

You two crack me up.... lol