The Home-made Home-builders Engine

To All:

For those of us who own a lathe and milling machine, somewhere in our
past there is probably a tiny steam engine. Indeed, there's probably
more than than one. A company in England provides the basic castings
as a kit. As the machinist, you are expected to provide all else,
from the machine to do the work to the KNOWLEDGE needed to operate the
machine.

Producing such an engine, from the basic one-cylinder model to larger
engines of remarkable complexity, serves as silent testimony as to our
abilities.

It strikes me as little more than a step along the way to produce a
FULL SIZE engine such as the Pobjoy. The crankshaft calls for a
professional piece of goods, probably obtainable from a Chinese
manufacturer, but the cylinders, being identical, call for much less
in the way of skills and tooling. With cast-iron cylinder barrels and
cast aluminum heads, the bulk of the engine can be produced on the
tooling found in the shops of literally thousands of amateur
machinists found in every country around the world.

While the copyright to the engine is presently held by the same
company that produces the Rotax, there are enough example of the
Pobjoy in aviation museums that it would be a relatively minor chore
to produce a set of drawings. Indeed, knowing the engine's bore &
stroke even a good PHOTOGRAPH gives a wealth of data leading to a
usable drawing. So long as those drawings contained significant
differences from the original there should be no question as to
violation of those rights. Such differences could be calling out
parts and bearings NOT used in the original Pobjoy.

With suitable drawings in hand we could produce the required molds
needed to produce the required castings. The drawings will also tell
us what gears and bearings are required, allowing us to order them
from suppliers who deal in such components. The drawings will also
show what type of valve guides are needed and even the valves, springs
and rocker-arms. With a bore of 75mm and a stroke of 87, we can
determine what EXISTING pistons my be used as well as the size of the
carburetor that is required.

The 'Experiment- Amateur-built' licensing category exists to promote
aeronautical education in America. Learning how radial engines work
and even building one yourself is no more difficult, in my opinion,
than building your own airframe.

-Robert S. Hoover

"Veeduber" wrote in message
...
To All:

For those of us who own a lathe and milling machine, somewhere in our
past there is probably a tiny steam engine. Indeed, there's probably
more than than one. A company in England provides the basic castings
as a kit. As the machinist, you are expected to provide all else,
from the machine to do the work to the KNOWLEDGE needed to operate the
machine.

Producing such an engine, from the basic one-cylinder model to larger
engines of remarkable complexity, serves as silent testimony as to our
abilities.

It strikes me as little more than a step along the way to produce a
FULL SIZE engine such as the Pobjoy. The crankshaft calls for a
professional piece of goods, probably obtainable from a Chinese
manufacturer, but the cylinders, being identical, call for much less
in the way of skills and tooling. With cast-iron cylinder barrels and
cast aluminum heads, the bulk of the engine can be produced on the
tooling found in the shops of literally thousands of amateur
machinists found in every country around the world.

While the copyright to the engine is presently held by the same
company that produces the Rotax, there are enough example of the
Pobjoy in aviation museums that it would be a relatively minor chore
to produce a set of drawings. Indeed, knowing the engine's bore &
stroke even a good PHOTOGRAPH gives a wealth of data leading to a
usable drawing. So long as those drawings contained significant
differences from the original there should be no question as to
violation of those rights. Such differences could be calling out
parts and bearings NOT used in the original Pobjoy.

With suitable drawings in hand we could produce the required molds
needed to produce the required castings. The drawings will also tell
us what gears and bearings are required, allowing us to order them
from suppliers who deal in such components. The drawings will also
show what type of valve guides are needed and even the valves, springs
and rocker-arms. With a bore of 75mm and a stroke of 87, we can
determine what EXISTING pistons my be used as well as the size of the
carburetor that is required.

The 'Experiment- Amateur-built' licensing category exists to promote
aeronautical education in America. Learning how radial engines work
and even building one yourself is no more difficult, in my opinion,
than building your own airframe.

-Robert S. Hoover


There is also the Lawrance 5-cyl. radial, about 35 HP from 75 cubic inches,
and a crankcase just under 9" in diameter.

As far as crankshafts, most radials used built-up cranks which can be
machined fairly easily. In the size of engine under discussion, the parts
that need to be ground can be finished on any commercial tool & cutter
grinder, and then assembled.

BTW, 75 cubic inches works out to 250cc per cylinder - how many 250 singles,
500 twins, and 1000-1200 fours are out there that could donate pistons,
pins, & rings; valves, springs & keepers, etc.?

Another Bob

On May 29, 3:12*pm, Charles Vincent wrote:

They do have an OHV version I believe. * At the RPM's these engines run
at i.e. direct drive prop, I am not sure the L head is that much of a
compromise.
----------------------------------------------------------------------------------------

All of the Pobjoy's were geared, OHV engines. They produced 80hp @
3300 rpm (prop speed of 1400rpm). Weight was 130 lbs.

-R.S.Hoover

Veeduber wrote:
On May 29, 3:12 pm, Charles Vincent wrote:

They do have an OHV version I believe. At the RPM's these engines run
at i.e. direct drive prop, I am not sure the L head is that much of a
compromise.
----------------------------------------------------------------------------------------

All of the Pobjoy's were geared, OHV engines. They produced 80hp @
3300 rpm (prop speed of 1400rpm). Weight was 130 lbs.

-R.S.Hoover


I was referring to the HCI Radials which are ungeared. I have seen the
Pobjoy. I have collected everything I can get my hands on with regard
to small radial engines. I have even managed to find factory blueprints
for parts of the Kinner and a Leblonde. No prints sadly for the Pobjoy,
just some contemporaneous technical reviews that do have three views of
the engine. There was a Pobjoy on display in a museum outside San Jose,
but that is a trek from your 20.

Charles

On May 29, 12:50*pm, "Bob Murray" wrote:
"Veeduber" wrote in message

...



To All:

For those of us who own a lathe and milling machine, somewhere in our
past there is probably a tiny steam engine. *Indeed, there's probably
more than than one. *A company in England provides the basic castings
as a kit. *As the machinist, you are expected to provide all else,
from the machine to do the work to the KNOWLEDGE needed to operate the
machine.

Producing such an engine, from the basic one-cylinder model to larger
engines of remarkable complexity, serves as silent testimony as to our
abilities.

It strikes me as little more than a step along the way to produce a
FULL SIZE engine such as the Pobjoy. *The crankshaft calls for a
professional piece of goods, probably obtainable from a Chinese
manufacturer, but the cylinders, being identical, call for much less
in the way of skills and tooling. *With cast-iron cylinder barrels and
cast aluminum heads, the bulk of the engine can be produced on the
tooling found in the shops of literally thousands of amateur
machinists found in every country around the world.

While the copyright to the engine is presently held by the same
company that produces the Rotax, there are enough example of the
Pobjoy in aviation museums that it would be a relatively minor chore
to produce a set of drawings. Indeed, knowing the engine's bore &
stroke even a good PHOTOGRAPH gives a wealth of data leading to a
usable drawing. *So long as those drawings contained significant
differences from the original there should be no question as to
violation of those rights. *Such differences could be calling out
parts and bearings NOT used in the original Pobjoy.

With suitable drawings in hand we could produce the required molds
needed to produce the required castings. *The drawings will also tell
us what gears and bearings are required, allowing us to order them
from suppliers who deal in such components. *The drawings will also
show what type of valve guides are needed and even the valves, springs
and rocker-arms. *With a bore of 75mm and a stroke of 87, we can
determine what EXISTING pistons my be used as well as the size of the
carburetor that is required.

The 'Experiment- Amateur-built' licensing category exists to promote
aeronautical education in America. *Learning how radial engines work
and even building one yourself is no more difficult, in my opinion,
than building your own airframe.

-Robert S. Hoover


There is also the Lawrance 5-cyl. radial, about 35 HP from 75 cubic inches,
and a crankcase just under 9" in diameter.

As far as crankshafts, most radials used built-up cranks which can be
machined fairly easily. *In the size of engine under discussion, the parts
that need to be ground can be finished on any commercial tool & cutter
grinder, and then assembled.

BTW, 75 cubic inches works out to 250cc per cylinder - how many 250 singles,
500 twins, and 1000-1200 fours are out there that could donate pistons,
pins, & rings; valves, springs & keepers, etc.?

Another Bob

Seem to me that the most modern motorcycle cylinders would be the
best. Metallurgy is still advancing rapidly and there are a lot of
innovations in recent bikes. Some even use "diamond-like coatings" on
high wear parts like cams and followers.

Recall that the Merlin and Allison V-12's of WWII used dual overhead
cams and 4 valves per cylinder which is the norm for motorcycles
today.

I worked up a CAD drawing of a radial using 5 banks of 4-cylinder
500cc motorcycle cylinder blocks. (7 banks didn't leave enough room
for intake and exhaust plumbing between the blocks.) The result is an
amazingly small 20 cylinder liquid cooled radial engine.

20 cylinders is enough that you could stop worrying about 2-plugs per
cylinder. If you fouled a couple, you probably wouldn't notice.

Looking through race parts catalogs turned up automatic transmission
planetary gear sets that are rated for 1500hp but are only 6" in
diameter and weigh about 15 pounds. The gear ratios are just right
for a PSRU. If they stand up to the hammering from a drag racer,
handling a couple of hundred HP should be a breeze.

To build this engine would require making a case, crank and rods with
the planetary in a nose case with thrust bearings. (Of course a lot
of other fiddly bits would need to be made as well.) However, the
heads, cylinders and pistons are the hard part and they are available
cheap.

On May 30, 9:21*am, bildan wrote:

To build this engine would require making a case, crank and rods with
the planetary in a nose case with thrust bearings. *(Of course a lot
of other fiddly bits would need to be made as well.) *However, the
heads, cylinders and pistons are the hard part and they are available
cheap.
--------------------------------------------------------------------------------------------------------

I disagree with regard to the heads and cylinders. But you are
correct when it comes to the gear reduction unit.

As several others have pointed out, publicly and in private messages,
there has been significant advances in metallurgy since the Pobjoy
first ran in 1926.

The Pobjoy had its share of problems, from its inception until its
production was finally dropped in 1946. But those problems would
probably not apply if the engine were produced today. For example,
the use of a planetary gear reduction system would eliminate the wear
problems encountered with the original herringbone gear, while a
modern, fully sealed valve train would improve the engine's mean time
before failure.

As for the question of using existing cylinders and heads, an aircraft
engine uses a different design philosophy than is used when producing
any other type of engine, although a stationary industrial engine
comes very close.

Ideally, the heads should follow standard aircraft engine practice in
the use of forgings rather than castings, although if the engine were
kitted, even partially so -- perhaps a pre-assembled lower end plus a
kit of parts for the cylinders and heads -- the price may be low
enough to satisfy the home-builder's budget limitations. For example,
if the heads were already machined, it does not take a great deal of
skill to swage the valve seats into place nor to stone them.
Volkswagen parts could be used for almost the entire valve train.

As a point of interest, while the basic idea is to produce an engine
sufficiently low in cost as to fulfill the needs of home-builders
around the world, should we be able to tap into a manufacturer at this
level, it is most likely they might be convinced to use their
facilities to produce the Fat-fin head needed to make the Volkswagen
engine more suitable than the existing engines by producing heads
having an honest sixty-five horsepower's-worth of fin area. Indeed,
this could be a method of subsidizing the cost of a 'replica' radial
-- OR OTHER ENGINE -- in that home-builders in those parts of the
world where Volkswagen components are still in good supply would
probably buy enough Fat-fin heads that their sale would provide the
start-up funds needed to get a more appropriate engine into
production.

Toward this end, while I mentioned the Pobjoy because of its excellent
ratio of power-to-weight, I also mentioned that an in-line engine such
as the de Havilland would be the least expensive.

This is another case where modern-day metallurgy may prove beneficial,
in that Lost Foam Casting might be used to produce the head and lower
end, using aftermarket air-cooled cylinders. The key to success in
this case would be the existence of a suitable crankshaft. That is,
one in which the throws are spaced sufficiently far apart to allow the
use of finned barrels.

-R.S.Hoover

On May 31, 12:35*am, Veeduber wrote:

, I also mentioned that an in-line engine such
as the de Havilland would be the least expensive.

The key to success in
this case would be the existence of a suitable crankshaft. *That is,
one in which the throws are spaced sufficiently far apart to allow the
use of finned barrels.

If I'm looking at this properly a standard VW water-cooled inline
crank (or most any similar 5 main bearing inline 4 crank) can be used
in a 90 deg. "V" 4. This would give plenty of room for fins. I think
all of the water-cooled VW cranks have 86mm or longer strokes and the
matching stock rods are between 7mm and 30mm longer than air-cooled
units, which should give good low speed torque. If it were a push rod
motor parts count would not be much greater than an inline?

A stub attached to the flywheel end of the crank and ground with the
mains to match a stock Continental front bearing, IMHO, would take
care of prop loads.
======================
Leon McAtee

On May 31, 12:35*am, Veeduber wrote:
On May 30, 9:21*am, bildan wrote:

To build this engine would require making a case, crank and rods with
the planetary in a nose case with thrust bearings. *(Of course a lot
of other fiddly bits would need to be made as well.) *However, the
heads, cylinders and pistons are the hard part and they are available
cheap.

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

I disagree with regard to the heads and cylinders. *But you are
correct when it comes to the gear reduction unit.

As several others have pointed out, publicly and in private messages,
there has been significant advances in metallurgy since the Pobjoy
first ran in 1926.

The Pobjoy had its share of problems, from its inception until its
production was finally dropped in 1946. *But those problems would
probably not apply if the engine were produced today. *For example,
the use of a planetary gear reduction system would eliminate the wear
problems encountered with the original herringbone gear, while a
modern, fully sealed valve train would improve the engine's mean time
before failure.

As for the question of using existing cylinders and heads, an aircraft
engine uses a different design philosophy than is used when producing
any other type of engine, although a stationary industrial engine
comes very close.

Ideally, the heads should follow standard aircraft engine practice in
the use of forgings rather than castings, although if the engine were
kitted, even partially so -- perhaps a pre-assembled lower end plus a
kit of parts for the cylinders and heads -- *the price may be low
enough to satisfy the home-builder's budget limitations. *For example,
if the heads were already machined, it does not take a great deal of
skill to swage the valve seats into place nor to stone them.
Volkswagen parts could be used for almost the entire valve train.

As a point of interest, while the basic idea is to produce an engine
sufficiently low in cost as to fulfill the needs of home-builders
around the world, should we be able to tap into a manufacturer at this
level, it is most likely they might be convinced to use their
facilities to produce *the Fat-fin head needed to make the Volkswagen
engine more suitable than the existing engines by producing heads
having an honest sixty-five horsepower's-worth of fin area. *Indeed,
this could be a method of subsidizing the cost of a 'replica' radial
-- OR OTHER ENGINE -- *in that home-builders in those parts of the
world where Volkswagen components are still in good supply would
probably buy enough Fat-fin heads that their sale would provide the
start-up funds needed to get a more appropriate engine into
production.

Toward this end, while I mentioned the Pobjoy because of its excellent
ratio of power-to-weight, I also mentioned that an in-line engine such
as the de Havilland would be the least expensive.

This is another case where modern-day metallurgy may prove beneficial,
in that Lost Foam Casting might be used to produce the head and lower
end, using aftermarket air-cooled cylinders. *The key to success in
this case would be the existence of a suitable crankshaft. *That is,
one in which the throws are spaced sufficiently far apart to allow the
use of finned barrels.

-R.S.Hoover

With respect, motorcycle heads are CNC machined from high strength
forged alloy billet. To my knowledge, no such head has ever failed
even under severe racing conditions.

The only 'top end' failures I'm aware of resulted from revving way
over red line RPM which caused valve failure. I know of a few which
suffered bent rods when the owner tried to start a hydraulically
locked engine after fuel had drained into a cylinder.

I would SWAG that top end motorcycle heads and cylinder blocks are
over designed for aircraft use by around 5X. The motorcycle news
group I belongs to recently asked if anyone had EVER overhauled their
engine due to simple wear. No one reported they had even though some
reported over 300,000 miles on their bikes. One reported tearing down
a high-mileage engine after the bike was wrecked just to find out what
the tolerances were - and to possibly re-use the parts. He reported
no measurable wear.

These are enormously strong engines and I think homebuilders should
take a serious look at them.

wrote:

If I'm looking at this properly a standard VW water-cooled inline
crank (or most any similar 5 main bearing inline 4 crank) can be used
in a 90 deg. "V" 4. This would give plenty of room for fins. I think
all of the water-cooled VW cranks have 86mm or longer strokes and the
matching stock rods are between 7mm and 30mm longer than air-cooled
units, which should give good low speed torque. If it were a push rod
motor parts count would not be much greater than an inline?

A stub attached to the flywheel end of the crank and ground with the
mains to match a stock Continental front bearing, IMHO, would take
care of prop loads.
======================
Leon McAtee

What about using an American V8 crank to build a straight air cooled
four? All the ones I've seen apart had 2 rods per throw and that would
space things out more. Machining down the counter weights would be
required but it would still leave you with a very strong crank. A light
weight aluminum clamp that looked like a big end of a rod could be easy
to make to block off the extra oil ports.

Another option would be to take a lesson from the so called V6 VW that
is little more than a staggered in-line six. Staggering the cylinders
to make a shallow V4 would also improve cooling. The problems of uneven
firing order could be solve by using a distributorless ignition or a
pare of 2 cylinder distributors. This way you could choose any in-line
4 crank that is both cheap and common as dirt (like the Toyota 20R for
example...)

Tony

Anthony W wrote:
wrote:

If I'm looking at this properly a standard VW water-cooled inline
crank (or most any similar 5 main bearing inline 4 crank) can be used
in a 90 deg. "V" 4. This would give plenty of room for fins. I think
all of the water-cooled VW cranks have 86mm or longer strokes and the
matching stock rods are between 7mm and 30mm longer than air-cooled
units, which should give good low speed torque. If it were a push rod
motor parts count would not be much greater than an inline?

A stub attached to the flywheel end of the crank and ground with the
mains to match a stock Continental front bearing, IMHO, would take
care of prop loads.
======================
Leon McAtee

What about using an American V8 crank to build a straight air cooled
four? All the ones I've seen apart had 2 rods per throw and that would
space things out more. Machining down the counter weights would be
required but it would still leave you with a very strong crank. A light
weight aluminum clamp that looked like a big end of a rod could be easy
to make to block off the extra oil ports.

Another option would be to take a lesson from the so called V6 VW that
is little more than a staggered in-line six. Staggering the cylinders
to make a shallow V4 would also improve cooling. The problems of uneven
firing order could be solve by using a distributorless ignition or a
pare of 2 cylinder distributors. This way you could choose any in-line
4 crank that is both cheap and common as dirt (like the Toyota 20R for
example...)

Tony
Using a V-8 crankshaft would result in a weird firing order..(A 4 cyl
crank has 4 throws 180ºapart===-The V-8 has 4 throws spaced 90º apart.)
Jerry