CASTING CALL!

To All.

The subject of this message is also the subject of the first article
in my blog...
bobhooversblog.blogspot.com
....where you will find some ILLUSTRATIONS of what I've been doing over
the weekend.

Have you ever cast aluminum?

Me too. In fact, most home-builders have some experience in the arts
of Thor. Most of us never progress beyond flat-castings. Those who
get Serious about casting will have delved into Cored Castings. And a
very few of those are able to Speak of Lost Wax or Lost Foam and a few
other more of the trickier bits.

I'm trying to cast individual heads for the VW engine, which is pretty
much a loser in the Power Department. That's because it wasn't
designed for Power, it was designed for Durability and Low Cost and
half a dozen other things you want to see in a practical People's Car.

And then I come along and start talking People's Plane!

I'm being forced to learn two things. The first, and where I'm most
likely to fail, is in the casting itself. Particularly in making a
suitable pattern and cores to produce a cylinder head capable of
satisfying the SECOND thing, which is to come up with the design of a
cylinder-head casting capable of coupling the required amount of heat
to the atmosphere.

I've got Liston's book on the design of aircraft engines and he has
been rather kind to people like me, taking the time to explain the
factors he uses in his equations. I don't think I'll fail because of
dumb-ness. The area in which I'm most likely to fail will be in
translating those Factors and the equations in which they are used
into the wooden patterns needed to turn the abstract into reality.

The illustrations in the blog offer some idea as to how I'm
approaching the problem. Something they don't show is the fact I'll
have to go back to basics with regard to the casting, since none of my
flasks are large enough to accept a pattern as large as the one needed
for a single head. That was something of a surprise but there have
been others :-)

All in all, it has been an enjoyable weekend.

-R.S.Hoover

On Mon, 19 Jan 2009 19:24:00 -0800 (PST), "
wrote:



Have you ever cast aluminum?

yes

Me too. In fact, most home-builders have some experience in the arts
of Thor. Most of us never progress beyond flat-castings. Those who
get Serious about casting will have delved into Cored Castings.

just bentonite based greensand because it is reusable time and time
again.


I'm trying to cast individual heads for the VW engine, which is pretty
much a loser in the Power Department. That's because it wasn't
designed for Power, it was designed for Durability and Low Cost and
half a dozen other things you want to see in a practical People's Car.

And then I come along and start talking People's Plane!

I'm being forced to learn two things. The first, and where I'm most
likely to fail, is in the casting itself. Particularly in making a
suitable pattern and cores to produce a cylinder head capable of
satisfying the SECOND thing, which is to come up with the design of a
cylinder-head casting capable of coupling the required amount of heat
to the atmosphere.


bob I couldnt visualise the head so I went out to the bench and got
myself a stuffed oily head to turn over in the hand.

first some amazement. people have sawn these heads in half so that the
higher thermal expansion of the rear jugs didnt jack the head off
square on the cylinders. how they did it I cant fathom because the web
between the intake ports is just 5mm wide at the manifold face.

anyway...
to me the design doesnt start from the whole downward as your blog
drawings suggest. doing this will send you insane.
start at the combustion chamber roof and work outward.

take the positions of the spark plugs top and bottom as set.
(I know you want only single ignition but dual is feasible so design
the heads for dual - it's easy)
we can of course tilt the plugs over to one side a little to gain
working clearance around their bodies.

I thought the valves could also stay where they are.
I also think that the exhaust duct can stay where it is.

one thing that needs to move is the inlet duct. this needs to move
away from the centreline and the manifold bolts need to go from being
located fore and aft to above and below. they are studs so it looks
doable to me.
as I squinted at it I realised that with the studs top and bottom the
plug position didnt even need to change.

the finning around the exhaust duct needs to change. I think the vw
fins in the area between the exhaust duct and the rocker well were
accepted as less than optimal to make the well a simple tooling shape.
bugger that though because it reduces the fin area just where you
need it around the exhaust duct. there is also a lot of interrupted
finning in this area.

if you look at the head side on so that you can see through the fins
around the exhaust duct, you can see that the fat fin at the exhaust
valve is an inch high. at the exhaust manifold the fin is quarter of
an inch high because the rocker well has been cast with a flat bottom.
what needs to happen is that the base of the rocker well needs to be
curved to keep it an inch off the exhaust duct.
the exhaust duct fins are wider spaced than the rest of the fins and
this seems to me to be wrong.

I think that by making the rocker well curve to stay parallel to the
exhaust duct and making the fins slightly closer together you would
nearly double the fin area in just the right area.

the existing exhaust spring could sit into a recessed well but you
could also machine up a longer valve and keep the spring standard.

I think that it is possible to substantially improve the exhaust
finning without changing the external dimensions much at all.
you just need to change the shape of the bottom of the rocker well.
tweaking the inlet duct position to achieve individual heads seems
trivial.

Stealth Pilot

On Jan 20, 7:50*am, Stealth Pilot
wrote:

bob I couldnt visualise the head so I went out to the bench and got
myself a stuffed oily head to turn over in the hand.
SNIP
Stealth Pilot

Rather than modifying the VW head It might be of interest to look at
the Corvair and adapt it to the VW?

If you don't have a Corvair head handy the link below has some good
pics

http://people.consolidated.net/tboyett/

If you are trying to figure out where the rockers get bolted down, the
'vair used a combination head nut/rocker stud.
=========================
Leon McAtee

On Jan 20, 6:50*am, Stealth Pilot
wrote:

I thought the valves could also stay where they are.
I also think that the exhaust duct can stay where it is.

I think that it is possible to substantially improve the exhaust
finning without changing the external dimensions much at all.
---------------------------------------------------------------------------------------------------

My goal is to DOUBLE the amount of waste heat the head can handle.
Which means I need between 3x and 4x the AREA of the existing fins.

Examining a Lyncoming or Continental shows how they did it, although
there's no way I can emulate their fin 'density.'

Playing with a Corvair head shows how they did it... and did it using
a method which I CAN emulate. But I've found it impossible to
maintain the bank-to-bank symmetry that makes the VW such a treat.

If you are interested in this project I suggest you begin with a
junked late-model head. Cut it in half. Remove the rocker arm
towers. Remove the exhaust-stack studs.

Using modeling clay, move the exhaust stack to about the present
position of the existing push-rod tube hole (ie, the one farthest from
where you have just cut). You may install a boss where ever needed to
secure the Corvair-style exhaust stack. Fortunately, Volkswagen
includes a formed exhaust gasket in their muffler-gasket kit which
lends itself to using the Corvair-type of exhaust stack.

Now you can go back to extending/adding-on new fins. So far, I've
'discovered' about 96 square inches (!!) of fin area that it MAY be
possible to develop. But it is going to be one weird bit of pattern-
making. (Due to the fins, one portion of the pattern must be
withdrawn ninety degrees away from the other.) Right now I'm looking
at a FOUR-PART flask. ( Remember, I said 'looking at' -- not in love
with.) Even so, it's going to be more difficult than anything I've
ever cast before. Not just because of the casting, but because of the
machining that follows.

I've not done anything at all with the inlet.

One step at a time.

-Bob

-Bob

On Tue, 20 Jan 2009 11:36:31 -0800 (PST), "
wrote:

On Jan 20, 6:50*am, Stealth Pilot
wrote:

I thought the valves could also stay where they are.
I also think that the exhaust duct can stay where it is.

I think that it is possible to substantially improve the exhaust
finning without changing the external dimensions much at all.
---------------------------------------------------------------------------------------------------

My goal is to DOUBLE the amount of waste heat the head can handle.
Which means I need between 3x and 4x the AREA of the existing fins.

Examining a Lyncoming or Continental shows how they did it, although
there's no way I can emulate their fin 'density.'

Playing with a Corvair head shows how they did it... and did it using
a method which I CAN emulate.

the corvair head in leon's link shows me in the little marks from
casting that the head is cast into a multipart steel die.
I believe for short runs of castings these could be bolted together
with machined parts in mild steel and a silicon spray type release
agent used. Foseco make the release agent I have in mind.

But I've found it impossible to
maintain the bank-to-bank symmetry that makes the VW such a treat.

I would have thought that you design one head and mirror image it for
the others. that is how the symmetry is achieved.

If you are interested in this project I suggest you begin with a
junked late-model head. Cut it in half. Remove the rocker arm
towers. Remove the exhaust-stack studs.

this is not an academic exercise for me. I will need just such an
engine for my Turbulent. The problem with the thread bases and the
woodruff key in the crankshaft causing fatigue failures is *exactly*
why I havent proceeded with just a simple vw conversion.
I'd actually like to build a sorted out trouble free engine.
sourcing one of the aero intended forged cranks and building around it
seems an option.


Using modeling clay, move the exhaust stack to about the present
position of the existing push-rod tube hole (ie, the one farthest from
where you have just cut). You may install a boss where ever needed to
secure the Corvair-style exhaust stack. Fortunately, Volkswagen
includes a formed exhaust gasket in their muffler-gasket kit which
lends itself to using the Corvair-type of exhaust stack.

so you are moving the exhaust from front and rear orientation to
downward.

what type of sparkplugs would need to be used for this engine and
where would they go?
this is critical because they need access clearance for servicing.


Now you can go back to extending/adding-on new fins. So far, I've
'discovered' about 96 square inches (!!) of fin area that it MAY be
possible to develop. But it is going to be one weird bit of pattern-
making. (Due to the fins, one portion of the pattern must be
withdrawn ninety degrees away from the other.) Right now I'm looking
at a FOUR-PART flask. ( Remember, I said 'looking at' -- not in love
with.) Even so, it's going to be more difficult than anything I've
ever cast before. Not just because of the casting, but because of the
machining that follows.

I've not done anything at all with the inlet.

One step at a time.

ok. our approaches differ in that the fins worry you so you are
concentrating on them. I think that they are a solvable problem.
my approach is to worry about them last because I can look to lycoming
and continental and pratt 'n whitney et al for the solution.

where do the plugs go in the combustion chamber roof and where do the
valves go?

do you keep the valves in a horizontal line and place the plugs
vertically above and below as the usual vw conversion does?
this keeps the existing underslung camshaft reasonably happy.

if you keep the valves in the existing position in the chamber roof
and redirect the inlet port to vertically above and the exhaust to
vertically below? what advantages does that give you?
note havent got to the fins yet.
what answers do your gut feel from years of experience tell us?

Stealth Pilot

On Jan 21, 1:02*am, Stealth Pilot
wrote:

what answers do your gut feel from years of experience tell us?

Stealth Pilot

I'm thinking that rather than keep using all this bandwidth on RAH it
might be time to take these mind experiments to a dedicated Yahoo
group devoted to a modern home built power plant, VW based or
otherwise.

Opinions/votes?

I'd be willing to set it up and be - one - of the moderators.
=========================
Leon McAtee

On Jan 21, 12:02*am, Stealth Pilot
wrote:

this is not an academic exercise for me. I will need just such an
engine for my Turbulent.
---------------------------------------------------------------------------

Buncha other folks too.

---------------------------------------------------------------------------

The problem with the thread bases and the
woodruff key in the crankshaft causing fatigue failures is *exactly*
why I havent proceeded with just a simple vw conversion.
I'd actually like to build a sorted out trouble free engine.
sourcing one of the aero intended forged cranks and building around it
seems an option.
------------------------------------------------------------------------------------

The answer to the Fractured Pulley Hub Problem is to simply put the
prop on the OTHER END of the crankshaft... as is done with all other
auto engine conversions you can think of .

----------------------------------------------------------------------------------------

so you are moving the exhaust from front and rear orientation to
downward.
------------------------------------------------------------------------------------

YES! This appears to be the easiest modification to do, as well as
the one most likely to meet the requirements of the Home-built
community.

--------------------------------------------------------------------------------------
what type of sparkplugs would need to be used for this engine and
where would they go?
this is critical because they need access clearance for servicing.
-----------------------------------------------------------------------------------

The Volkswagen engine uses a Wedge-type combustion chamber with its
associated 'squish' areas. The spark plug will be located at about
the same location as resent, since this is the position of maximum
turbulence (which is needed for proper ignition). There is enough
'meat' in this area to allow room for a SECOND spark plug... but wedge-
type combustion chambers have shown no benefit from multiple points of
igntion until the diameter exceeds five inches or thereabouts. The
use of dual plugs in some modern automotive engines reflects their
extremely high COMPRESSION RATIO. Since that does not apply to a
converted VW, neither do the dual plugs. Indeed, the only reason for
providing ANY provision for dual ignition is to satisfy the Feel Good
legislation hurriedly passed (..1937? ) following the death of a
Congressman's son in an airplane having a single ignition system. (As
a point of interest, about 80% of ALL engine failures during that era
(ie, early 20's to late 1930's) were due to IGNITION failures.
Because of that, the US Navy REQUIRED their engines to be fitted with
TWO ignition systems. The joke here is that the problems which causes
all those failures had largely been ELIMINATED by the late 1930's [and
are totally absent today!]. Indeed, a modern automotive ignition
system is several order's-of-magnitude MORE RELIABLE than the typical
aviation magneto of the 21st century.)
--------------------------------------------------------------------------------------

where do the plugs go in the combustion chamber roof and where do the
valves go?

--------------------------------------------------------------------------------------
I donno. Where do they go on YOUR conversion? :-)

Actually, after spending several hours with heads last evening I may
have found a better system than the one I originally described.

In either case, it's a lot of work and I've got a few other things on
my plate at the moment.

-R.S. Hoover

On Mon, 19 Jan 2009 19:24:00 -0800 (PST), "
wrote:



Have you ever cast aluminum?

re my head suggestions in the other post....

I have to ask my edm owner to verify that this is possible.

in an ideal world I would cast everything castable and I would spark
erode the recesses to create the exhaust finning.

I'm not sure if spark eroding aloominum is possible but eroding
generally can do this sort of job with amazing precision.

Stealth Pilot

On Jan 20, 9:56*am, Stealth Pilot
wrote:
On Mon, 19 Jan 2009 19:24:00 -0800 (PST), "

wrote:

Have you ever cast aluminum?

re my head suggestions in the other post....

I have to ask my edm owner to verify that this is possible.

in an ideal world I would cast everything castable and I would spark
erode the recesses to create the exhaust finning.

I'm not sure if spark eroding aloominum is possible but eroding
generally can do this sort of job with amazing precision.

Stealth Pilot

SP & Bob,

Just wanted to let you guys know that even though I may not
participate in every discussion, I do read most of them and appreciate
your contributions here.

Maybe one should acquire one of these French engine heads and see how
they
did it.

http://www.jpx.fr/Jpx/english/4tx75E.htm

Reggie