casting intricate finned heads

On Jan 14, 2:57*pm, bildan wrote:

I presume you've had a close look at R4360 cylinders.
------------------------------------------------------------------------------------

I've rubbed my belly on them a time or two.

----------------------------------------------------------------------------------
*The art of
finning *reached its pinnacle at the end of WWII. *To cool these
monsters, the fins had to be extremely fine - as fine as radiator
fins. *The only way to make them was machining with thin saw blades.
------------------------------------------------------------------------------

Roger that. Then we chopped them up and melted them down and sold
them as ingots of aluminum for a few pennies per pound.

But you've left out what is perhaps the most interesting part. In
machining those thin slots they had to come up with a kind of profiler
-- a motorized pantograph. Not only did the blade, she spin 'round
and around, for each cut they had a CAM which caused the spinning
cutter to rise and to fall, producing this beautifully machined slot
in the fantastic FORGED aluminum... and made it so that even Rosy the
Riveter could swap-out the cams and torque-down the clamps and hit the
GO lever with her knee and keep right on gossiping at the top of her
voice with the girl at the next machine who was doing exactly the same
thing.

Meanwhile, back in Chermany, the Minister of Disinformation was
telling everyone that things were jus' hunky dory; that there was no
need for German wives & mothers to step up to the assembly line (we've
got lots of slaves for that), and 1943 came along and then the Germans
were so far behind the 8-ball you couldn't even SEE them.... (Little
black dots out there on the horizon [Great looking uniforms!] unaware
that the war was ALREADY OVER... because we had enough beans, bullets
and black oil to have kept the Russians supplied for something like
EIGHTEEN YEARS.)

Too bad we failed to learn that particular lesson... because now it's
being used against us.

-R.S.Hoover
I'd bet that it could be done far more easily today with CNC
machines. *For that reason, I'd machine heads from aluminum billet.

"cavedweller" wrote in message
...
On Jan 13, 9:31 am, "Dick Meade" wrote:
Tooling cost for permanent mold is prohibitive.

What I don't know about foundry practive would fill large volumes, but
a relatively simple single cavity that would last a while and some
appropriate finish machining still might (!) be worth looking
at....unless, of course, for some reason machining a head out of sound
billet stock isn't a solution.

Nice link.

================================================== =======

Machining a head from billet would be an excellent solution, just a lot more
expensive.

Cold finish aluminum billet is usually about 3 times the price per pound
than T-0 ingots, and you have to pay the same price for all the machine
shavings you do for the finished machine part. Considering something like a
VW head, you are probably tossing as much as 50% of your billet, purchased
at three times the price. Then you have to add the machining time. All worth
it if you can afford it for sure, but usually much more expensive.

That's why I suggested casting a head, including ports, combustion chambers,
rocker tub, etc, and leaving the fined area solid to be machined by CNC or
tracer. You get the ultimate detail in your cooling fins for maximum
efficiency, but save the cost of the alloy and all the extra metal discarded
when machining from billet.

On Jan 15, 5:19*pm, "Maxwell" #$$9#@%%%.^^^ wrote:
"cavedweller" wrote in message

...
On Jan 13, 9:31 am, "Dick Meade" wrote:

Tooling cost for permanent mold is prohibitive.

What I don't know about foundry practive would fill large volumes, but
a relatively simple single cavity that would last a while and some
appropriate finish machining still might (!) be worth looking
at....unless, of course, for some reason machining a head out of sound
billet stock isn't a solution.

Nice link.

================================================== =======

Machining a head from billet would be an excellent solution, just a lot more
expensive.

Cold finish aluminum billet is usually about 3 times the price per pound
than T-0 ingots, and you have to pay the same price for all the machine
shavings you do for the finished machine part. Considering something like a
VW head, you are probably tossing as much as 50% of your billet, purchased
at three times the price. Then you have to add the machining time. All worth
it if you can afford it for sure, but usually much more expensive.

That's why I suggested casting a head, including ports, combustion chambers,
rocker tub, etc, and leaving the fined area solid to be machined by CNC or
tracer. You get the ultimate detail in your cooling fins for maximum
efficiency, but save the cost of the alloy and all the extra metal discarded
when machining from billet.

So, how many actual dollars does the price difference between billet
and ingot represent as a percentage of the overall cost of an
airplane...after you sell the chips as scrap.

Presumably you are looking at at least 4 heads which fits well with
CNC. CNC milled heads made from billet will be exactly alike, which
is more than can be said for castings.

"bildan" wrote in message
...

So, how many actual dollars does the price difference between billet
and ingot represent as a percentage of the overall cost of an
airplane...after you sell the chips as scrap.
-------------------------------------------------------------
That's obviously a very difficult question, that will vary based on design,
size and number of the parts in the aircraft. But it is safe to say that,
after you incur the cost of both the billet and the machining, the scrap
value of the chips are never much of a saviour.




Presumably you are looking at at least 4 heads which fits well with
CNC. CNC milled heads made from billet will be exactly alike, which
is more than can be said for castings.
-------------------------------------------------------------------
You will get little argument from me on that one. CNC machined billet parts
hard to beat, especially when you need the strength. But when the strength
is not required, a casting can save tons of money.