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.
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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