Can someone please explain the usage of these cranks / rods in our sport? What are the relative strengths of "forged" versus "billet", and what is the difference in our application (racing).
I have commonly used Crower rods and cranks in my small blocks. Recently, I was told by a metallurgical-type that the forged units are just as strong, if not stronger due to tensile and fatigue strengths. That doesn't make sense to me. Top Fuel uses billet rods and cranks...I would think that would settle it, but no.....Mr. M.E. stated it was for cost-saving measures.
I don't know about anyone else, but I've never saved a dime by buying billet cranks.
I searched the EN40B thread, but it didn't explain the applications and relative strengths.
Thanks for your time.
S.
He who is in me is greater than he who is in the world.
I worked at Bryants for 4 years back when materials were changing a lot and when billets and the LA forging were both popular.
With forgings the design of the counterweights is limited to what was designed into the forging. This matters a lot!
With good CNC equipment the maching time on an LA forging and a billet are simlar. In some operations like plunging the mains, billets are easier. Also when you rough-in a billet it is about 26RC where the forging is in the mid 30s as I recall. As I recall that EN30B was a drag to machine if it was hardened at all.
The avaliablity of a given material is much more ready for the billets than the forgings which were made in Japan last time I knew about it in the 80s.
The universal big block LA forging weighed about 168lbs, a person could lift them but you got tired quickly in a shop. The billets weighed over 300lbs.
I think the differences in matertials also depends on the heat treating process being used. What is good for a thin rod may not be best for a thick crank. Of course journal hardness is a issue that rods aren't concerned with and the abilty to grind smooth radii without burning etc. There are a lot of issues beyond the strength in application that determines what is used.
Billets, or chunks of barstock are used for high-end cranks for a number of reasons.
Modern CNC crank-making machine tools can carve virtually any shape out of the 300-400 lb slug. They could also do the same thing to an oversized forging in a lot less machine time. The CNC crankmaking process is now affordable for many racers.
Forgings, especially non twisted ones may have "grain flow" that follows the metal from the main journals up thru the rod throws. Some think this adds strength. Heat treating may alter this, but it's not a bad idea.
The problem with forging is that it doesn't guarantee a 'clean' part. It's done in the atmosphere, so oxidation can be a problem and by the nature of the forging process, impurities can be literally pounded into the metal during the many strokes of the forging press. There is the very real possibilility of small voids or pockets being trapped in the metal. All of this compromises strength to some extent. The problem is you may not know how much it is compromised until you run over your crank.
OTOH, high quality steel bars (billets) can be vacuum melted and then vacuum remelted to eliminate virtually all impurities in the steel. Literally the steel is made in a vacuum furnace, so no nasty stuff from the atmosphere gets into the steel. The term VAR, which some may recognize as associated with "good" steel means Vacuum Arc Remelted. The steel is remelted after it's first vacuum melt to further refine the steel and remove the impurities. All of this adds to the big-time cost, but that's not the major problem today.
Most all VAR 4340 and similar alloy steels go to the aerospace industry. You definitely want your commercial airliner engine and steel structural parts to be the best they can be. Running over your fanjet engine turbine shaft or main landing gear is usually a whole lot bigger deal than running over your crank.
There is a limited supply of this VAR alloy steel. I read recently that production was sold out of much of it thru 2007. So you have to believe that the F1 teams and perhaps Cup and some ProStock teams have paid whatever it costs to get the material. A 300 or 400 lb slug could cost as much as the CNC machining, grinding and heat treating...perhaps lots more.
The bottom line is that if you want (and need) the best overall crank you can get, you need to make it from a high-quality billet, at least AQ or Aircraft Quality 4340. If you are Ferrari. Toyota, Renault, etc. or maybe Hendricks you might be using VAR alloys. I certainly would consider it if I was in that ballgame making engines that had to run well over 1 million revs 'in anger'.
Last edited by OldSStroker on Thu Nov 10, 2005 12:33 pm, edited 1 time in total.
Very good posts Schmidt and oldSStroker.
There is also a question if all 4340 cranks really are made with the same material. When you drill a Bryant or similar crank for heavy metal you basicly destroy a drillbit. Then drill out some Chinese "4340" cranks is like drilling in butter.
Its a difference between certified SAE 4340 material and just "4340" It can mean something else a serial number or what have you if you press the issue. I understand that one supplier of "4340" cranks are in court now having advertised US made 4340 cranks and laboratory tests showed it not to be.
Fantastic input, fellas. As an end-user, non- machinist, I had no idea the labor that went into the hard parts I was buying....or why they were better, for that matter. I've been lucky enough to have missed the opportunity to break a forged OR billet crank in 25 years, but I believe that has alot to do with keeping the rpm at a respectful level.
I am really grateful to you guys for enjoying the education I rcv on this forum; thanks a million!
S.
He who is in me is greater than he who is in the world.
I don't know about the Chinese cranks but the Bryant cranks are hard to drill because the heat treatment leaves the cranks much harder than other companies have the patience to do.
You think its a drag putting heavy metal in a hard crank? Try drilling the oil holes and rod pin lightening holes.
Now you are bringing back some memories, I prototyped the first few cranks from the LA forging in a Bridgport clone before we had the CNC. That was hard work at 42 RC.
When we first were machining counter weights on some cranks in the CNC the vibrations were so loud the you needed ear plugs, head phones. If you held your jaw just the wrong distance open your teeth would vibrate into eachother.
I guess What i was trying to ask was if i contacked a company like crower or even eagle would the cost still be as high.
I doubt they would even consider doing a single crank because the cost would be so high making all the programs and disrupting production and the time of the most valuable employees.
I would consider making one for you but it wouldn't be cheap, maybe $5K.
And at that price, even though it sounds high, I would probably regret having taken the project. Your only hope is that you can find someone that has already made some and has the programs finished.
The only poeple that make a billet one is moldex and they take for ever to get.
I,am in a buick club and they are making a new block for the 455 with smaller mains.I don,t know how many poeple at this time would want one just looking at diffrent senarios.
Mike Rogers
215-674-5240
EQ Cylinder Heads
http://www.rogersperformance.com
Contact Mike Mittler at Mittler Brothers they bought the crankshaft tooling from Oliver when they stopped making cranks. He might be interested in making something like a Buick 455 crank.
