what every boy needs - yeah seriously

Peter Dohm wrote:
I really had decided to let this whole matter slide; since, in the end,
everything that I might actually want to build would require 80 to 120
horsepower--and more if I really want the aircraft to have utility for
transportation. So this mostly an intellectual exercise.

However, since you phrase your response in the above manner:
1) To get from a thermal limitation of 45 horsepower to 60 horsepower looks
like a 33% increase. If you dissagree, please respond to
Hewlett-Packard--since I have been using their calculators for the past 25
years or so.

As I understand it, it doesn't actually work that way. As the power
goes up, an increasing proportion of the heat goes out the exhaust, but
it is probably close enough. According to various reports and Mackerle,
the proportion of heat going into the head goes up though, and the
proportion going into the cylinder goes down, so if you are trying to
maintain the head temp it is likely to be more than 33% difference.

2) Doubling the velocity of airflow should require 400% (not 300'%) of the
energy, according to the old engineering texts that I can no longer find.

If you could find those texts, they would tell you that when driving a
fan, the power required actually goes up as the cube of the difference
in RPM and the CFM at subsonic speeds scales with the rpm, so doubling
the CFM results in 800% increase in power required. For ram air it is
slightly more complicated, but it essentially rises as a cube of the
airflow as well. NACA did some tests on fan cooled radials and the
Japanese actually deployed some (Kawanishi N1K is one) so there is
research out there. As for the 300% I picked it up off of where I had
actually started to calculate the power difference required for a 33%
increase in HP and a diminished heat transfer coefficient and then left
off unfinished. My mistake, but it understates not overstates the
problem of improving cooling by just increasing the airflow. As in all
things, it depends on just where on the curve you are. The bottom
almost looks like a straight line, the top like a brick wall.

3) By the combining the above calculations, and using the latest trusty
Hewlett-Packard calculator, the 33% increase in cooling should require 177%
of the energy.

See above....

4) The basic point was that: if you climb at 60 (kph, mph, kts, or
whatever) and you would need to be climbing at 90 to adiquately cool the
engine; then the difference could be made up by the addition of a cooling
fan.

You would have to figure out how to connect the fan. I think the stock
VW fan moves about 1000CFM at 3000rpm and about 1500CFM at 4000rpm (when
I have been told the belt starts slipping). Veeduber I am sure has the
proper numbers. I don't think it would be a minor thing hooking it up
mechanically and not losing everything you gained in additional weight,
additional drag and HP losses to the fan. If your design speed is slow
enough, I guess you can drop the drag. The Japanese did it with a
geared coaxial fan on a radial, so they had a simpler task. They ended
up with a smaller nose that was almost completely filled with the
spinner and a really small air intake ringing that.

5) As to the real engineering textbooks: BRING 'EM ON.

Peter

On Jan 16, 4:39*pm, Charles Vincent wrote:

You would have to figure out how to connect the fan. *I think the stock
VW fan moves about 1000CFM at 3000rpm and about 1500CFM at 4000rpm (when
I have been told the belt starts slipping). *Veeduber I am sure has the
proper numbers.
--------------------------------------------------------------------------------------------------------

The numbers,, proper or not, are 1300cfm, according to the VW Factory
Service Manual... or whatever... (black covers w/embossed silver
printing). But I think it's a giant LEAP backwards. Somebody out
there is sand-casting VW crankcases in aluminum. Torture them with
lotsnlotsa money and get them to shuffle things around a bit, allowing
a BORE of about 4.625" and a stroke of 88mm, then cast a LONG #1 main
bearing and throw away the tranny flange... might even get them to
cast a Dyna-Focal mount on the other end... and make some entirely NEW
1-cylinder per head headz, and we can stop calling it a VW (although
we'd still be using a lot of VW parts) and start calling it a DIY
Homebuilder Engine... with about 100bhp @ 2700 rpm (or whatever... use
the C-90 cam timing; get someone like Dick (sp?) Schneider to grind us
some wiggle sticks. 40A. coaxial alternator. Itty-bitty geared
starter. Electronic ignition. Holes for two plugs. SIX head-stays.
Juice valves outta the little Chevy. Absolutely NOTHING
certified...although EVERYTHING has done a million miles or more in
other engines. That is to say, there ain't nothing new in such a
design.

Kinda heavy, though... about 181 bare, mostly because of the crank.

-Bluesky Bob

wrote in message
...
On Jan 16, 4:39 pm, Charles Vincent wrote:

You would have to figure out how to connect the fan. I think the stock
VW fan moves about 1000CFM at 3000rpm and about 1500CFM at 4000rpm (when
I have been told the belt starts slipping). Veeduber I am sure has the
proper numbers.
--------------------------------------------------------------------------------------------------------

The numbers,, proper or not, are 1300cfm, according to the VW Factory
Service Manual... or whatever... (black covers w/embossed silver
printing). But I think it's a giant LEAP backwards. Somebody out
there is sand-casting VW crankcases in aluminum. Torture them with
lotsnlotsa money and get them to shuffle things around a bit, allowing
a BORE of about 4.625" and a stroke of 88mm, then cast a LONG #1 main
bearing and throw away the tranny flange... might even get them to
cast a Dyna-Focal mount on the other end... and make some entirely NEW
1-cylinder per head headz, and we can stop calling it a VW (although
we'd still be using a lot of VW parts) and start calling it a DIY
Homebuilder Engine... with about 100bhp @ 2700 rpm (or whatever... use
the C-90 cam timing; get someone like Dick (sp?) Schneider to grind us
some wiggle sticks. 40A. coaxial alternator. Itty-bitty geared
starter. Electronic ignition. Holes for two plugs. SIX head-stays.
Juice valves outta the little Chevy. Absolutely NOTHING
certified...although EVERYTHING has done a million miles or more in
other engines. That is to say, there ain't nothing new in such a
design.

Kinda heavy, though... about 181 bare, mostly because of the crank.

-Bluesky Bob

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

Well, those weight and power numbers look mighty close to the numbers that
Continental is just bringing to market and Lycoming is working on. So, if
you feel the need to swing a 70 or 72 inch prop and ALSO prefer a direct
drive engine that can idle on approach, they are still good numbers.

I could very well be a customer in the easily foreseeable future.

Peter

On Jan 17, 6:43*am, "Peter Dohm" wrote:
. *So, if
you feel the need to swing a 70 or 72 inch prop and ALSO prefer a direct
drive engine that can idle on approach, they are still good numbers.

I could very well be a customer in the easily foreseeable future.
---------------------------------------------------------------------------------------------

The fact you CAN swing that biga prop doesn't mean you HAVE to.

I was think more along the lines of a crankcase machined to accept a
crankshaft machined to accept a connecting rod that was laying there
on the shelf, along with the bearing-shells to fit it. We STILL gotta
come up with four barrels an' four slugs an' four heads an' four
rods... and I've no idea in the blue-eyed world where those would come
from. Grab 'Speedway' or 'Jegs' and they got all kinds of neat stuff
but if you want four BIG finned cast-iron jugs you're still looking at
something around 4" diameter (ie, about 101mm) But they DO got some
beeeutiful rods. Old Ford style. Got enough bearing area to use in a
steam engine. (See, it has to do with the Specific Impulse and
converting Torque into Thrust an' neat **** like that... an' I show up
with a VW engine in my pocket and they just LOOK at me...

-Bob

wrote:
On Jan 17, 6:43 am, "Peter Dohm" wrote:
. So, if
you feel the need to swing a 70 or 72 inch prop and ALSO prefer a direct
drive engine that can idle on approach, they are still good numbers.

I could very well be a customer in the easily foreseeable future.
---------------------------------------------------------------------------------------------

The fact you CAN swing that biga prop doesn't mean you HAVE to.


Say what???

wrote:

The fact you CAN swing that biga prop doesn't mean you HAVE to.

I was think more along the lines of a crankcase machined to accept a
crankshaft machined to accept a connecting rod that was laying there
on the shelf, along with the bearing-shells to fit it. We STILL gotta
come up with four barrels an' four slugs an' four heads an' four
rods... and I've no idea in the blue-eyed world where those would come
from. Grab 'Speedway' or 'Jegs' and they got all kinds of neat stuff
but if you want four BIG finned cast-iron jugs you're still looking at
something around 4" diameter (ie, about 101mm) But they DO got some
beeeutiful rods. Old Ford style. Got enough bearing area to use in a
steam engine. (See, it has to do with the Specific Impulse and
converting Torque into Thrust an' neat **** like that... an' I show up
with a VW engine in my pocket and they just LOOK at me...

-Bob

I would look to Harley-Davidson for the pistons. New Harleys use German
made Mahle pistons and they can go a lot of miles without service. The
sleeves could be ordered from any company that makes them and there are
more than a few to choose from. The fins could be turned out of
aluminum then pressed on or cast around the sleeve before the final boring.

All aluminum cylinders with nickasil coatings could also be made up but
the cost and R&D would both go up... There are small shops that apply
this coating...

Tony