pourin pistons

http://www.enginebuildermag.com/Arti...ston_pour.aspx


Very neat 2 spout ladle

On Feb 10, 4:24*pm, Jerry Wass wrote:
http://www.enginebuildermag.com/Arti...ston_pour.aspx

Very neat 2 spout ladle

Freaky clean foundry, that. Pretty sophisticated permanent mold,
including a permanent, internally expanded core. That ladle and the
two gates enabled the casting to fill rapidly from the bottom without
choking the runners. Very well designed mold.

"Jerry Wass" wrote in message
...
http://www.enginebuildermag.com/Arti...ston_pour.aspx


Very neat 2 spout ladle

Cool link.

Are most aircraft pistons cast or forged???????

On Feb 11, 7:21*pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

...

http://www.enginebuildermag.com/Arti...ston_pour.aspx

Very neat 2 spout ladle

Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

stol wrote:
On Feb 11, 7:21 pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

...

http://www.enginebuildermag.com/Arti...ston_pour.aspx
Very neat 2 spout ladle
Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

I would have guessed "cast" because of the larger temperature
coefficient of forged metal---already have a big enough problem
with the cast pistons, controlling clearance changes with rapid
external temperature changes.

"Jerry Wass" wrote in message
news
stol wrote:
On Feb 11, 7:21 pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

...

http://www.enginebuildermag.com/Arti...ston_pour.aspx
Very neat 2 spout ladle
Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

I would have guessed "cast" because of the larger temperature coefficient
of forged metal---already have a big enough problem
with the cast pistons, controlling clearance changes with rapid external
temperature changes.

Are they a metal reinforced casting, like a lot of auto pistons?

On Feb 12, 9:35*am, "Maxwell" #$$9#@%%%.^^^ wrote:
"Jerry Wass" wrote in message

news


stol wrote:
On Feb 11, 7:21 pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

. ..

http://www.enginebuildermag.com/Arti...ston_pour.aspx
Very neat 2 spout ladle
Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

I would have guessed "cast" because of the larger temperature coefficient
of forged metal---already have a big enough problem
with the cast pistons, controlling clearance changes with rapid external
temperature changes.

Are they a metal reinforced casting, like a lot of auto pistons?

Probably. I'll find out when I make a cutaway later this year,
I hope. The steel inserts in the piston wall around the pin boss are
to control expansion across the widest axis of a cam-ground piston,
which is 90 degrees to the pin. Aluminum has a coefficient of linear
thermal expansion of almost exactly twice that of steel and an
aluminum piston can get bigger than its steel cylinder without some
control, or else a lot of clearance.
Pistons are usually cast of a high-silicon aluminum for wear
resistance. Machines beautifully.

Dan

wrote in message
...
On Feb 12, 9:35 am, "Maxwell" #$$9#@%%%.^^^ wrote:
"Jerry Wass" wrote in message

news


stol wrote:
On Feb 11, 7:21 pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

. ..

http://www.enginebuildermag.com/Arti...ston_pour.aspx
Very neat 2 spout ladle
Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

I would have guessed "cast" because of the larger temperature
coefficient
of forged metal---already have a big enough problem
with the cast pistons, controlling clearance changes with rapid external
temperature changes.

Are they a metal reinforced casting, like a lot of auto pistons?

Probably. I'll find out when I make a cutaway later this year,
I hope. The steel inserts in the piston wall around the pin boss are
to control expansion across the widest axis of a cam-ground piston,
which is 90 degrees to the pin. Aluminum has a coefficient of linear
thermal expansion of almost exactly twice that of steel and an
aluminum piston can get bigger than its steel cylinder without some
control, or else a lot of clearance.
Pistons are usually cast of a high-silicon aluminum for wear
resistance. Machines beautifully.

Dan

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

Those steel tabs are so small, it seems hard to imagine they could do much
to control thermal expansion. When metal, much like water in an ice tray,
begins to heat or cool, there is little if anything you can do to stop it.

On Feb 16, 6:59 am, "Elliot G" wrote:

Those steel tabs are so small, it seems hard to imagine they could do much
to control thermal expansion. When metal, much like water in an ice tray,
begins to heat or cool, there is little if anything you can do to stop it..

They don't entirely stop it, but they reduce it greatly and force
the piston to modify its shape as required.

From http://www.mgcars.org.uk/mgcc/sf/000304.htm

"Another contender was the "Invar Strut" piston, originally introduced
by Adolph Nelson in 1925. He decided that if the piston crown had a
temperature so much higher than the skirt, why not arrange a clearance
between these two components, or even link them together with a metal
which did not readily expand. It was highly successful and was more
widely used throughout the automotive world than any other design.
"INVAR" was not a trade name, but in fact a metal alloy with an
expansion of only 0.000002" per degree centigrade. So effective was
the use of the ‘strut’ that these pistons operated with less clearance
than a cast iron version, without any risk of seizure. "Birmalite"
alloy, was just one version, made by the British Aluminium Company at
Smethick.

The reduced clearance between the piston and the cylinder bore,
automatically limited the ‘changing sides’ movement caused by the
angle of con rod thrust. In turn, this reduced the pressure on the
piston rings, eliminated piston slap, and the oiling up of spark
plugs. This more effective seal also reduced oil consumption. All of
these factors lead to a reduction in cylinder bore wear. "

See the whole article. Enlightening. FYI, the .000002" expansion
per degree F is about a third to a quarter of ordinary mild steel's
expnasion rate, and maybe a fifth to sixth of aluminum's.

They still make them:

http://www.team-integra.net/sections...?ArticleID=183

More stuff:

http://books.google.ca/books?id=2_QQ...esult#PPA32,M1

Some newer alloys, with fewer expansion problems, are starting to
replace the strutted pistons.

Dan

stol wrote:
On Feb 11, 7:21 pm, "Elliot G" wrote:
"Jerry Wass" wrote in message

...

http://www.enginebuildermag.com/Arti...ston_pour.aspx
Very neat 2 spout ladle
Cool link.

Are most aircraft pistons cast or forged???????

Cast ..

I would never buy forged parts. Counterfeit parts with forged
documents are usually lower quality.

Dan, U.S. Air Force, retired