trenace
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posted September 05, 2005 10:33 AM
 Edited By: trenace on 5 Sep 2005 11:40
From the 'Net (Crower is closed today, I'd expect) it looks like billet Ti rods are only $400-something each. Which is not unreasonable. Twelve-week lead time though.
Turns out if I use the valves I was intending to use (only a trace larger than stock, being oversize is not the purpose) there is a 12-week wait on them too, so the wait may not matter. Or I may just say the hell with it and stick with stock valves to save time.
Crower certainly ought to be able to say whether their Ti rods can run tighter squish than steel, and how tight is reasonable as well as answer other questions such as durability. Who knows, maybe I'll be able to combine tighter squish with lighter weight and still long-lasting durability (without fatigue problems of the Ti.) It will be interesting to find out what Crower says.
On the other hand, the billet aspect doesn't sound that great -- fully machined forged would be better. Perhaps those are the $4000/set rods, and the $400/each are the crap ones. On the other hand, for custom rods unlike anything a company might presently be making, new dies would be needed for forged and that's totally out of the question price-wise, so it may be that Crower only does the billets. Another interesting point to find out.
  
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gunner
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posted September 05, 2005 12:11 PM
Trenace I think Pankel has the forged Ti. Yosh had them at one time but I don't know about now or who has them. I may be completely wrong about them being forged, but it seems like I rmember this to be true.
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trenace
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posted September 05, 2005 12:13 PM
Edited By: trenace on 5 Sep 2005 13:15
I can't figure how a custom length forged rod could be made, unless only the big end is forged to shape and the rest is left just as a block to be machined out (Basically equivalent to billet then.)
If the Ti has to be billet anyway then I have to wonder how much improvement it really would be compared to a really quality forged steel rod, as granularity is even more of a factor with Ti than with steel.
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entropy
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posted September 06, 2005 12:02 AM
my understanding of "forged", "billet"...
forging is the the process of treating a chunk of cast metal by heating then applying great pressure (pressing/whacking/rolling) to change the structure from lil granules (brittle) to something not brittle. Using a die to whack it would get it close to the final shape.
The resulting chunk of metal is a billet
Machine the billet and get a high tensile strength product like "forged rods", "forged pistons", "billet crank".
cast aluminum head is brittle, billet big block is not.
Sorry for the technical terms 
Some engineer can certainly correct me, yep!
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trenace
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posted September 06, 2005 11:29 AM
Edited By: trenace on 6 Sep 2005 15:24
I'm no engineer unfortunately but my understanding is that billet need not, and generally does not, have grain structure conforming to a given design shape.
It's usually a block of metal, period. Perhaps forged as a block, but not with the grain conforming to any particular pattern. It's typically a "blank slate" so to speak, if the end product is not being described as forged.
And so when you machine it away yielding a part described as "billet," the grain generally does not flow around the points that one might wish it to flow.
On the other hand, a piece described as forged, while as you say whacked under heat to the correct shape in dies, typically has a surface that while quite useable generally speaking as the exterior surface for things like connecting rods and so forth, is not perfectly smooth and can result in points where cracks are more likely to begin.
So forging to a slight oversize and then fully machining the piece (all surfaces of it) combines the best of both worlds -- the grain structure of forged, flowing and conforming around the shape of the object, and the fully machined or even polished surface finish.
Anway, in a Ti rod described as billet, as I understand it the grain doesn't flow around the big end the way it does with a Ti rod described as forged. But, though one can get away fine with forged steel rods that don't bother machining most of the exterior surface of the rod, with Ti that should be done as it is more prone to cracking from surface defects. At least that is my understanding of it.
Something described as billet is of course cheaper, there being no forging dies specific to that part required. And I guess that explains Crower's $400/rod price as opposed to $1000/rod that may be typical for forged Ti rods. But even to get that, probably one must be needing a rod that matches up to an existing set of dies, which in my case seems unlikely, and even if that did happen by chance, $4000 is more than I want to spend on rods.
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trenace
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posted September 06, 2005 02:35 PM
Edited By: trenace on 6 Sep 2005 19:14
I gave up on the Ti rods idea because I'm not comfortable with non-forged Ti rods, just does not seem a good idea to me except perhaps for something you replace every season. Too bad, as that concept of superstrong, same-weight-as-Carillos forged Ti rods that I could run tighter squish with was very appealing. However doesn't seem that that would be available, except perhaps at the $4000 cost Entropy mentioned.
I called Falicon and while they say they expect their rods are less stretchy than stock, nonetheless they recommend same squish as stock rods, e.g. 0.040."
Entropy, on the valve size matter, sorry I somehow missed replying to your answer above. It turns out the that the company in question recommending the change says that the purpose is not to be larger per se, actually the valves they use are only a little larger (about 1/2 mm.) Specifically,
quote:
The valves are .020" bigger than stock. The reason is as much for longevity as flow and in my opinion more than worth the extra work involved, especially for sprint use. They are one piece Hi-flow. Problem with the stock size is they tend to "curl" under hard use when running narrow seat bands, which the close clearance Nucleus guides allow you to do, the same fact also increases low -mid vacuum. (The special copper, nickle,alloy mix gives a massive advantage) this means thinner seats on the Inlet and a much improved 5 angle seat profile, plus vastly improved valve stem control adding up to big gains in Torque/reliabilty.
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trenace
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posted September 06, 2005 06:12 PM
Edited By: trenace on 6 Sep 2005 19:41
Ra had written:quote:
A 5mm stroke is a 2.5mm spacer + base gaskets with no cam chain issues.
Ra, actually I had thought that usually the aluminum spacer plate was run with no further gaskets on its top or bottom, though of course one could use additional gaskets to control height as Entropy is doing.
I'm supposing you're referring to 2 base gaskets in addition to the spacer plate... both 0.010's, or only 0.005's? Any thoughts yourself on thickness of the Cometic head gasket thickness vs stock or on the stock "in the hole" value or stock squish, to help calculate rod length for given squish and planned set of gaskets?
Thanks!
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gunner
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posted September 06, 2005 07:57 PM
quote:
my understanding of "forged", "billet"...
forging is the the process of treating a chunk of cast metal by heating then applying great pressure (pressing/whacking/rolling) to change the structure from lil granules (brittle) to something not brittle. Using a die to whack it would get it close to the final shape.
The resulting chunk of metal is a billet
Machine the billet and get a high tensile strength product like "forged rods", "forged pistons", "billet crank".
cast aluminum head is brittle, billet big block is not.
Sorry for the technical terms
Some engineer can certainly correct me, yep!
Simple terms for forged is a BIG piece of material that has had the shit stomped out of it and compressed into a small piece of material. More metal in the same space = stronger part peroid. It's a very simple way to view forging.
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There's no such thing as a motor with no more power to give only people with no more intelligence to get it
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trenace
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posted September 06, 2005 08:00 PM
Edited By: trenace on 6 Sep 2005 21:16
True, but if you forge something into a rectangular block, and then CNC out a shape from it e.g. a rod, the grain structure and properties won't be the same as when you forge it into dies conforming to your design, e.g. the shape and dimensions of that rod.
Both are forged in terms of process, but the result is not the same.
If someone passed off the first -- machined out of a block -- as a "forged" connecting rod or piston it would be somewhat deceptive.
Crower does not do that, they straightforwardly advertise them as billet and do not use the word forged, even though the block of billet might have been forged into that block.
If I could, just bumping my question to the bottom so it won't be lost:
Ra had written:quote:
A 5mm stroke is a 2.5mm spacer + base gaskets with no cam chain issues.
Ra, actually I had thought that usually the aluminum spacer plate was run with no further gaskets on its top or bottom, though of course one could use additional gaskets to control height as Entropy is doing.
I'm supposing you're referring to 2 base gaskets in addition to the spacer plate... both 0.010's, or only 0.005's? Any thoughts yourself on thickness of the Cometic head gasket thickness vs stock or on the stock "in the hole" value or stock squish, to help calculate rod length for given squish and planned set of gaskets?
Thanks!
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