"Cracked" con rods

[Ross]

Who can explain how these rods are manufactured?
Winfred, aren't the M70 rods that way too? I've not been in the bowels of one but seem to remembr something written about it in the old sales literature.
My understanding is that the process offers perfect alignment of the rod halves. What I don't get is how this can be done without distorting the part.

[Jon K]

Well most rods I know of are forged (yes most stock rods are forged) and they're made from two forgings.

[Jon K]

"The invention concerns an improved manufacturing method of a powder metal connecting rod with a stress riser crease formed in a side face by forging a sintered preform with a generally V-shaped notch in the side face. A one-piece forged rod is produced having a crease therein which is readily separated by a cracking process into a two-piece rod with a separable bearing cap. "

http://www.patentstorm.us/patents/56...scription.html

[Jon K]

I think I did read that this might be how my rods were made - I am not sure

[Ross]

Very informative. Unless I missed it the article doesn't address final machining but it must be done after the cracking as the force would certainly elongate the hole.
Yours look like sintered, what do the mating surfaces look like? Machined or broken?

[Jon K]

I haven't taken them apart (per engine builder recommendation). I will let you know - I think they would crack them and then machine them, because even on cracked rods you never see the V groove

[winfred]

they are broken, that way it has maximum contact area and locks together, i have not been into the bottom of a v12 yet but the m60 i built a few months ago was powdered/cracked rods, i do know when a m60/62 sucks water #6,7 or 8 usually punches through the valley and out again the side before it stops

[Barney Paull-Edwards]

After forging but before machining, they are split in a pre-machined groove by a bloody great hydraulic ram in order to achieve a molecularly perfect fit, Thats my understanding! By co-incidence BMW/Okrasa were the first to do it with the `80`s F1 engine I think,the rods are H beam but 90` from road engines.

[Jon K]

That is my understanding as well Barney

[Bill R.]

newer m3,m5,z8's have them. Its cracked when the forging is still rough and then the sides and bore are machined.. Here's a pretty good description in this article

Who can explain how these rods are manufactured?
Winfred, aren't the M70 rods that way too? I've not been in the bowels of one but seem to remembr something written about it in the old sales literature.
My understanding is that the process offers perfect alignment of the rod halves. What I don't get is how this can be done without distorting the part.