On Jan 8, 7:30*pm, "Maxwell" #$$9#@%%%.^^^ wrote:

I've alway thought it would be more practical to CNC saw all the cooling
fins. Seems a bit extreme at first glance, but if you go to the time or
expense to fabricate patterns to cast the heads, we must be talk about doing
more than just a couple of sets. So the programming cost might well be worth
the cooling efficency of extremely detailed cooling fins.
------------------------------------------------------------------------------------------------------------------------
Dear Maxwell, et al

(more for the et al's at this point)
What makes this NOT a ' blue-sky & bull**** ' kinda project is the
fact we can pick up a telephone and have the key components sitting on
our front porch in a matter of HOURS. Such as:

Pistons & cylinders, crankshafts, camshafts, valves, valve seats,
valve guides, carburetors, electronic ignition components, electrical
system components... and so on right down the list.

In fact, the existence of the Roto-Way type heads... most folks think
of them as 'Scat-type'... provides 'Proof of Concept' -- meaning this
IS NOT a new idea. What's 'new' is coming up with an isolated head-
design that is amenable to air-cooling.

Historically, when the real engine manufacturers ran into the thermal
limitations of cast aluminum (**) they way they tackled the task
serves as our instruction manual. They tried liquid cooling and
machined fins but finally achieved the desired power-to-weight ratio
by going to FORGINGS for their aluminum heads.

(Forged aluminum is denser; it can couple more heat to the atmosphere
than a casting can. [and if one you grammarians jumps on that...] ).
Indeed, comparing the American & British efforts makes a damn good
adventure novel -- one in which the British should have won (ie,
because of their slide-valve engines). But buried in that 'novel' is
methods tried & discarded not because they didn't work but simply
because the goal was for more horsepower than those methods could
provide. And to be fair here we really need to include the Japanese
14-cyl radial... which was using the so-called 'Singh Grooves' in the
early 1940's, allowing them to run on 70 octane tractor gas.)

In fact, we can even use the Lycoming O-145 as a good model of how NOT
to do things. (Yeah, it produced 65hp... but only when you spun it up
above 3000 rpm. Stuck on the nose of a Piper 'Cub' it was a TERRIBLE
powerplant, simply because it produced all of its thrust in a narrow,
high-velocity slug of accelerated air into which the fuselage of the
Cub was buried. And as we know (and Lycoming seemed to forget), drag
increases as the SQUARE of velocity. But AFTER the war, when a bright
young fellow named Mooney came along with a sleek little single-place
design, the O-145 finally came into its own... because there was
simply no comparison to the induced drag of a Cub and a Mite.

So what's our engine gonna be? It's going to be what it ALREADY IS, a
set of 94mm jugs atop an 84mm Chinese crankshaft. But the difference
is in the HEADS. And it's not even the WHOLE head we're talking
about, just the outer portion that is associated with the exhaust
stacks. This is the HOTTEST part of the VW engine. VW's engineers
did some truly remarkable things to ensure the CORNERS of the engine
got the MAJORITY of the cooling air. Unfortunately, when you try to
do that using RAM-AIR instead of a blower, you run into all sorts of
problems, most of which can be resolved by simply increasing the AREA
of the cooling fins.

And how do we do that? (Someone asks) ...or, Why hasn't someone done
that? (another asks)... and in both cases the answer is pretty much
the same: We do it by altering the shape of the exhaust outlet, and
YES, someone has ALREADY DONE THAT... if you're familiar with the
Porsche engine.

The point here is that it's not a big change, in engineering terms.
Nor even an especially difficult change. The main problem is that all
previous efforts were aimed at CAR engines, which presented some space
limitations that they simply could not resolve if they wanted the
engine to fit in the car. Bottom Line: They came up with a new car-
body that provided enough room for the 'fatter' engine -- 'fatter'
because it had more fins. And put that fatter engine into airplanes,
too. Which means we're not quite the ground-breakers we think we
are :-)

So what's the basis of our 'success'? Easy! We simply re-design the
exhaust to dump out the BOTTOM of the head, as GM did with the
Corvair... and which VW could NOT do with the VW engine. When the
exhaust stack is moved outta the way it gives us access to the upper-
outer corner of the head for each of the jugs, and that is where we
install our additional fins. Not only do we add additional fins, we
increase the size of the fins that are already there, so that our
maximum PEAK output comes up to something on the order of 80hp, whilst
our maximum SUSTAINABLE output is about 60hp (Standard Day
assumed).

Does this give us a 'thousand hour' engine? Hell no! Lookit the
bearing area. At that level of output you'll be lucky to get a TBO of
500 hours. Of course, replacing every bearing in the engine will only
run you about sixty bucks.

Sure sounds easy, eh? In fact, if it's so damn easy you gotta wonder
why I haven't already done it. Surprise! I already did... sorta. We
called it the 'Fat Fin' head and tried to accomplish what I've
described here by TIGing on additional fin area to stock heads. Which
didn't work for a lot of reasons, but there were some examples that
DID work... until the fins warped or the valves overheated or any one
of a dozen other things. Plus the biggie: Fat Fin heads would not
fit in a VEHICLE. And without that market, they were little more than
a joke... some crazy ol' guy wanting to put a VW engine in an
airplane, for crysakes!

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

How do you get in touch with OTHER 'crazy ol' guys?' Back then, you
got Pope Paul to put a notice in the magazine. Remember all them
notices? Yeah. I don't either.

But now we got the Internet.

Tell you what... Somewhere in my drawings I've got a stock VW head,
sorta -373'ish (that's a VW part number... don't sweat it). I'll dig
it out, convert it into a .jpg and post it on my blog. Then you can
blow it up to near-full-scale and print it out. One it's printed, you
can start fooling with the location of this & that... moving the
exhaust stack... which is when you'll discover that a push-rod and an
exhaust stack will NOT peacefully co-exist :-) But there's a couple
of ways in which they WILL... expect they put one hell of an angle
onto the push-rod... and you gotta move the rocker-arm around... stuff
like that. THAT'S what we're talking about here. Once we can move
the exhaust stack WITHOUT trashing the push-rod, we can increase the
cooling-fin area by about 25%... mebbe more.

Best of all (mebbe) is that we'll come up with a casting that the
average home machinist can turn into a cylinder head. And that will
only take another 10,000 words or so... plus a few hundred
pitchers... if anyone is interested.

-R.S.Hoover


And just for Flavor of the Month -- sump plate