what every boy needs - yeah seriously

On Jan 9, 11:09*pm, "Peter Dohm" wrote:


Bob...don't Jabiru use heads machined from billet stock?

That was my recollection as well, although I can no longer find it on the
web.

Peter

I had the same problem...ending up going to the Engine section on the
Zenith site.

On Fri, 9 Jan 2009 21:19:11 -0800 (PST), "
wrote:


Bob...don't Jabiru use heads machined from billet stock?
-------------------------------------------------------------------------------------------

I don't know. But judging from their appearance that seems to be the
case.

-Bob


the entire jabiru engine(s) have always been made totally from cnc
milled barstock.
in the early days the claim was that they could make a batch of 4 at a
profit.

Stealth Pilot

wrote in message
...
*
* First off, we can forget about lost-foam or anything more exotic than
* green-sand, simply because there aren't enough of us.
*
*Lost foam isn't all that "high tech" and is actually well within the
*ability of anyone that can build their own foundry and ram up some
*sand. Classic lost wax is still a viable option and if one uses oil
*based sand rather than bentonite green sand you can get much better
*detail and steeper angles - but you do need a muller for oil sand.
*
*Leon McAtee

How can you mold or sculpt invest foam articles with a simple hobby process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?

Also, if you use oil sand and wax investments, how can you possibly remove
enough wax from the mold to allow the introduction of molten aluminum and
yeild a useable casting, when you have detail as fine as a cooling fin?

"Stealth Pilot" wrote in message
...

| this will be no consolation but I've just thrown in a job that
| returned me somewhere between $80,000 and $100,000 per year to move
| below the poverty line.
| I've become my wife's carer as her psyche problems worsen.
|
| so I will be *making* my next aircraft. the turbulent will have all
| manner of bits cast and machined by me.
|

Do you have any photos of some of your projects?

On Jan 10, 9:27*am, "Maxwell" #$$9#@%%%.^^^ wrote:

How can you mold or sculpt invest foam articles with a simple hobby process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?
------------------------------------------------------------------------------------------

Dear Maxwell,

While there are some pretty sturdy plastic-like waxes that can
withstand ramming-up in a core box, most of the methods using lost wax
begin by DIPPING the wax model in a slurry of high-temperature CLAY,
after all of the sprues, vents gates and supports have been attached
manually. After the clay dries it is BAKED, first at a fairly low
temperature ( ie 200F ), during which it is rotated several times to
get rid of the casting wax, and finally at a higher temperatures, such
as 500F for about two hours. The resulting product is then stiff
enough to withstand ramming.

There are variations to this theme. Some call for several dipping &
baking episodes using different recipes of clay. Dentists are the
best source of information on this procedure. The main down-side is
the HIGH COST of the refractory clay dips.

-Bob

On Jan 10, 10:27*am, "Maxwell" #$$9#@%%%.^^^ wrote:
wrote in message


How can you mold or sculpt invest foam articles with a simple hobby process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?

Your're thinking WAY too much inside the box. Making the molds for
the wax/foam cores is simple and there are many references to the
process(s) on the internet.

Ramming up sand directly on a foam or wax mold - isn't - practical.
Maybe if you resorted to vibration to pack core sand and then gas the
whole thing with CO2 ? But there is a way around that limitation as
well. Again, a search on the net should turn up some clues. I'd find
a link or 2 for you to start but I have to head out for the weekend
shopping with the Wife .............. maybe this evening.


Also, if you use oil sand and wax investments, how can you possibly remove
enough wax from the mold to allow the introduction of molten aluminum and
yield a usable casting, when you have detail as fine as a cooling fin?

I may have been unclear in my earlier post. I did not intend to imply
using oil based sands with investment casting. Sounds kind of messy!
I meant that oil based sand allows one to make better detail and
thinner parts than you can get with bentonite based sands. Should
have been a separate paragraph...............

Investment casting of the quality needed is very doable by the hobby
caster.
=====================
Leon McAtee

wrote in message
...
On Jan 10, 9:27 am, "Maxwell" #$$9#@%%%.^^^ wrote:

How can you mold or sculpt invest foam articles with a simple hobby
process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?
------------------------------------------------------------------------------------------

Dear Maxwell,

While there are some pretty sturdy plastic-like waxes that can
withstand ramming-up in a core box, most of the methods using lost wax
begin by DIPPING the wax model in a slurry of high-temperature CLAY,
after all of the sprues, vents gates and supports have been attached
manually. After the clay dries it is BAKED, first at a fairly low
temperature ( ie 200F ), during which it is rotated several times to
get rid of the casting wax, and finally at a higher temperatures, such
as 500F for about two hours. The resulting product is then stiff
enough to withstand ramming.

There are variations to this theme. Some call for several dipping &
baking episodes using different recipes of clay. Dentists are the
best source of information on this procedure. The main down-side is
the HIGH COST of the refractory clay dips.

-Bob

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

I'm well aware of the variations in the investment casting process, but you
hand already limited the discussion to a sand casting, and for economic
reasons I would have to agree. But there is no way to use a wax investment
in a sand casting. Subsequent melting of the wax will contaminate the sand
mold, regardless of green sand, oil sand or air set.

Considering the use of foam, first we have to mold or sculpt a foam cylinder
head in full detail for each head we have to produce. Then adequately pack
sand between the fins of a foam pattern, when the fins are as detailed as
this project would require. Doesn't sound possible, much less practical to
me.

wrote in message
...
On Jan 10, 10:27 am, "Maxwell" #$$9#@%%%.^^^ wrote:
wrote in message


How can you mold or sculpt invest foam articles with a simple hobby
process,
and then get something as detailed as air cooled fins on a foam or wax
investment to withstand even the most careful ramming process for green
sand, oil sand or air set casting?

Your're thinking WAY too much inside the box. Making the molds for
the wax/foam cores is simple and there are many references to the
process(s) on the internet.
-------------------------------------------------------

Care to provid a link of something as complex as VW head, "hobby" molded in
foam?





Ramming up sand directly on a foam or wax mold - isn't - practical.
Maybe if you resorted to vibration to pack core sand and then gas the
whole thing with CO2 ? But there is a way around that limitation as
well. Again, a search on the net should turn up some clues. I'd find
a link or 2 for you to start but I have to head out for the weekend
shopping with the Wife .............. maybe this evening.
-------------------------------------------------------------

Doesn't matter what other process there are, you still have to have the
"hobby" molded foam or wax investment.




Also, if you use oil sand and wax investments, how can you possibly remove
enough wax from the mold to allow the introduction of molten aluminum and
yield a usable casting, when you have detail as fine as a cooling fin?

I may have been unclear in my earlier post. I did not intend to imply
using oil based sands with investment casting. Sounds kind of messy!
I meant that oil based sand allows one to make better detail and
thinner parts than you can get with bentonite based sands. Should
have been a separate paragraph...............

Investment casting of the quality needed is very doable by the hobby
caster.
---------------------------------------------------------------

If you can reference any hobby process that will made it "simple" to cast
custom air cooled VW heads at home. I can assure you, I'm not the only
person on this group that would like to see a link.

50 HP at 30.6 pounds weight?
Which includes a 19:1 ratio gearbox!

PT-50 Turboshaft Engine

On Jan 9, 4:49*pm, Jerry Wass wrote:

HEY!Thanks for the answer---Hadn't heard of that alloy--mosta *my
castings . . . .

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

Sorry Jerry, but 'Electrum' (as I believe it's spelt), whilst the
cat's pajamas's in the 1930's because Germany produced about 90% of
the world's magnesium, thanks to one of their companies holding the
patent to the most efficient sea-water extraction process, by the
1950's everyone was discovering that the alloy, which was about 95%
magnesium, the other 5% made up of aluminum, zinc, copper and what-
have-you (remember, these are the folks who came up with 2024-T6), it
was discovered that the alloy -- which was vvery popular for the gear-
cases on helicopters -- was susceptible to AGE HARDENING. (Volkswagen
discovered the same thing... and changed their alloy in 1972.)

The problem was not discovered for about 25 years, when they noticed
that the Universal Replacement Crankcase often developed fatal cracks
from simply sitting on the shelf in the dealer's parts department.
These parts had never been assembled; had never been subjected to any
form of stress. Yet they still cracked. The quick fix was to
increase the percentage of Aluminum in the casting meta from about 2%
to about 4%. But engineers opined that the additional aluminum may
NOT be a permanent cure... but we would have to wait another 25 years
to find out.

Boeing found out the hard way. Their Vertol Division experienced
similar cracking problems in their helicopter crankcases.

The best solution was to go to aluminum vs magnesium.

-Bob