casting intricate finned heads

veedubber rapping greensand involves gently tapping the mould all
around as you will know.
if you are casting something box like all you get is a slightly larger
mould cavity and a mould which will pull out of the greensand.
cooling shrinkage of the casting will hide most of this.

fins however are a bugger.
if you rap for and aft along the fin then all is probably ok.
if you rap across the finning then sure as apples you will shear off
the sand between the fins.
if the finning goes in more than one direction you're sunk.

a better method might be to use resin moulding.
this involves a resin inpregnated sand and a heated aluminium or brass
mold. the sand is flung on to the gently heated mold with the heat
setting the resin binder (you use a silicon release spray on the
mold).
with just the right heating of the mold the set sand gradually grows
around the mold. when it appears thick enough you flip the mould over
and shake off the unset sand.

after you separate the impression from the mold the impression is
allowed to cool and the impression halves are held together and
supported in dry untreated sand. in use often the impression will
survive for up to 4 castings

the set sand impression in the one I've seen had immaculate fidelity
and was separated from the mold without any rapping.

This is something I've not done myself. it was demonstrated one
evening at a local teachers college by the instructor. they teach
manual arts teachers who in turn use the technique to teach high
school students live casting techniques. the kids cast and machine the
parts of a scale field cannon.

the boss at my old works has one his son cast and machined in pride of
place on his bookshelf at work :-)

Stealth Pilot

On Jan 13, 12:27*am, Stealth Pilot
wrote:
veedubber rapping greensand involves gently tapping the mould all
around as you will know.
if you are casting something box like all you get is a slightly larger
mould cavity and a mould which will pull out of the greensand.
cooling shrinkage of the casting will hide most of this.

fins however are a bugger.
if you rap for and aft along the fin then all is probably ok.
if you rap across the finning then sure as apples you will shear off
the sand between the fins.
if the finning goes in more than one direction you're sunk.
---------------------------------------------------------------------------------------------------------

Dear Stealth,

I am familiar enough with basic casting to have made a number of
useful items, some involved with the installation of computer
equipment about ships. Support and repair ships are floating machine
shops. And that includes a sea-going foundry... although the foundry
is seldom going when we are at sea. (Perhaps if a coffee pot required
repair...)

Repair ships are often called many things, some of which may be
repeated in mixed company, such as 'Submarine Tender,' Destroyer
Tender' and so forth. As a general rule, they can usually fix
anything, barring something contaminated with radiation or coffee from
the Chief's mess.

My short career as a Molder came to grief due to the process described
in your last sentence. But I finally figured out why my fins were
shearing, and I DID manage to produce a set of Hi-Power heads, which
were eventually cast and used... on a 6cid Briggs & Stratton engine,
largely without any help from my shipmates. (They said the
entertainment value was simply too great to waste.)

But I never even considered casting a VW head. I DID try to increase
its fin area by welding but that's a different story. What I'm
looking at now is the possibility of casting INDIVIDUAL cylinder
heads, which offers some unique challenges. However, with regard to
rapping the pattern prior to lifting, I'm considering casting the fins
SEPARATELY from the 'body' of the cylinder head (ie, the inlet &
outlet stacks, the heavy bosses for the head stays and valve guides.
The fins would then be attached to the 'body' by TIG welding. As a
part of this process, I would like to cast FOUR heads at a time, using
a flask that does not presently exist, but would be built atop a VW
front wheel spindle and coaxed into motion with some sort of belted
drive. This method would build-up a humongous 'bead' as the welding
progressed, hopefully sufficient so as to preclude the need to return
the part(s) to the oven between weldments... the work being done in a
box or other reservoir to keep the parts covered by argon or C25... or
Camel's breath, for all I know... something so I wouldn't have to keep
brushing the weld area as I moved from one head to the next, the time
relative to the length of the weldment, the amount of heat it
contributes, the angle of the rotating fixture and so on. Plus the
usual requirement -- that it has to be cheaper than durt and eazy to
build.

Yes, I realize it is another 'crazy' idea. I also realize I can only
melt a given quantity of metal in a given amount of time... so I could
not pour a fully finned head without going back and starting at square
one -- with a furnace and crucible capable of holding approximately
twice what I presently have.

I appreciate mention of the different methods, most of which are
completely new to me. There are a few techniques and methods I hope
to try but I'm more interested in producing something that actually
works, as opposed to exploring a host of new materials, methods and
procedures... but not turning out any parts I can actually use. Still
a lot of blue sky visible at this point; I've not ruled out a
combination of CNC and castings.... I would probably progress faster
with electronics and G-code than I would with the traditional
Mettalmelter Mentality. Right now I've been cautioned to not attempt
lifting anything that exceeds TWENTY POUNDS (!!) Because if I do,
they are going to have to glue another of my vertebrae together... and
I already walk like I've shoved an (unmentionable) up my (censured).

I expect to find lots of reasons why my non-foundryman ideas will not
work but feel they'll just have to get used to being made to do so by
stepping outside of the box and giving the thing a kick now & then.

-Bob

On Jan 13, 4:54*am, " wrote:

I appreciate mention of the different methods, most of which are
completely new to me. *

Well if that's the case, how about semi permanent molding...gravity
pour and reusable tools? There's lots of that around for automotive
manifolds and heads....

Tooling cost for permanent mold is prohibitive. Gas inclusion is also a
concern. Airset or Nobake molding lends itself to this sort of casting.
Then again, the answer might be right in Veeduber's back yard:
http://www.foundry-castings.com/adv4.htm



"cavedweller" wrote in message
...

Well if that's the case, how about semi permanent molding...gravity
pour and reusable tools? There's lots of that around for automotive
manifolds and heads....

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.

"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 13, 4:54*am, " wrote:

...

But I never even considered casting a VW head. *I DID try to increase
its fin area by welding but that's a different story. *What I'm
looking at now is the possibility of casting INDIVIDUAL cylinder
heads, which offers some unique challenges. *However, with regard to
rapping the pattern prior to lifting, I'm considering casting the fins
SEPARATELY from the 'body' of the cylinder head (ie, the inlet &
outlet stacks, the heavy bosses for the head stays and valve guides.
The fins would *then be attached to the 'body' by TIG welding. *

If you are going to make the fins separately you might consider
machining them from stock, rather than casting them.

Then how about sticking them onto a wax block that is the form
for the cylinder (or the head) so that when you cast the cylinder
or the head the pre-made fins weld to the cast metal.

How about if you make the fins from pure aluminum (for
good heat transfer) but make the body from an alloy for
better strength and heat resistance. Maybe you can
cast the cylinder or the head in aluminum bronze.

Maybe I'm crazy.

Just some thoughts.

On Jan 14, 11:06*am, Fred the Red Shirt
wrote:

If you are going to make the fins separately you might consider
machining them from stock, rather than casting them.
-------------------------------------------------------------------------------------

I tried everything I could get my hands on, including fins salvaged
from other heads. Until I can rule out a lack of skill on the part of
the weldor (me) I'm forced to assume that was most of the problem. Of
the heads welded by a professional, the Fat Fins were cut from .125
3003 and 5052. I ASSUMED everything would come out hunky-dory and was
more than willing to pay the full bolt to get a professional job.
Testing was done with a rose-bud tip on an acetylene torch, aimed into
the combustion chamber and dialed down to produce a CHT between 450
and 500F. Then I measured the outlet air temp and compared it to the
inlet air temp. All set? So here we go.... and saw the new fins
slowly bend and fold and finally touch each other, shutting off the
air-flow here & there. Attempting to straighten them (quite a bit of
time later... after they had cooled) revealed a nice collection of
cracks in the weld.

Then followed about six months of off & on 'experimenting' including a
stock 1600 engine assembled from junked parts (but it actually ran)
that used cast aluminum fins salvaged from other heads... but a lot
smaller than my original, more hopeful design (ie, about 3/4" addition
vs 1.5") Test club that has worked before... big bat-wing-looking air-
scoops....

They worked. Sorta. I think. The trouble was in the comparison.
So... this page in the notebook is the Fat Fin heads... and THIS page
is the stock heads... except they AREN'T really stock, that is. In
fact, they're pretty good heads, with all the flash cleaned up and the
chambers opened up a tad and a few other things like that because they
started out as NEW heads and would eventually go into a stock-
displacement engine that had a LOT more pizzazzz than a STOCK
engine... if you know what I mean. And the simple truth is that they
cooled pretty well -- probably BETTER than stock. So that I ended up
comparing apples to oranges. Which made me feel kinda dumb. Because
when I'd swapped heads and ran it in a bit then re-torqued the heads
and got the air-scoops mounted and started running the engine for
real... it gave me almost exactly the same figures per rpm as I saw
with the Fat Fin engine. At which point I said to hell with it and
went into the house and mixed me up a stiff Scotch and may have even
put some water in it.

-Bob Hoover

On Jan 14, 1:10*pm, " wrote:
On Jan 14, 11:06*am, Fred the Red Shirt
wrote:

If you are going to make the fins separately you might consider
machining them from stock, rather than casting them.
-------------------------------------------------------------------------------------

I tried everything I could get my hands on, including fins salvaged
from other heads. *Until I can rule out a lack of skill on the part of
the weldor (me) I'm forced to assume that was most of the problem. *Of
the heads welded by a professional, the Fat Fins were cut from .125
3003 and 5052. *I ASSUMED everything would come out hunky-dory and was
more than willing to pay the full bolt to get a professional job.
Testing was done with a rose-bud tip on an acetylene torch, aimed into
the combustion chamber and dialed down to produce a CHT between 450
and 500F. *Then I measured the outlet air temp and compared it to the
inlet air temp. *All set? *So here we go.... *and saw the new fins
slowly bend and fold and finally touch each other, shutting off the
air-flow here & there. *Attempting to straighten them (quite a bit of
time later... after they had cooled) revealed a nice collection of
cracks in the weld.

Then followed about six months of off & on 'experimenting' including a
stock 1600 engine assembled from junked parts (but it actually ran)
that used cast aluminum fins salvaged from other heads... but a lot
smaller than my original, more hopeful design (ie, about 3/4" addition
vs 1.5") *Test club that has worked before... big bat-wing-looking air-
scoops....

They worked. *Sorta. *I think. *The trouble was in the comparison.
So... this page in the notebook is the Fat Fin heads... and THIS page
is the stock heads... except they AREN'T really stock, that is. *In
fact, they're pretty good heads, with all the flash cleaned up and the
chambers opened up a tad and a few other things like that because they
started out as NEW heads and would eventually go into a stock-
displacement engine that had a LOT more pizzazzz than a STOCK
engine... if you know what I mean. *And the simple truth is that they
cooled pretty well -- probably BETTER than stock. *So that I ended up
comparing apples to oranges. *Which made me feel kinda dumb. *Because
when I'd swapped heads and ran it in a bit then re-torqued the heads
and got the air-scoops mounted and started running the engine for
real... it gave me almost exactly the same figures per rpm as I saw
with the Fat Fin engine. *At which point I said to hell with it and
went into the house and mixed me up a stiff Scotch and may have even
put some water in it.

-Bob Hoover

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

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.

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.