ENGINE BASICS

[Veeduber[_2_]]

To All:

Recent posts about the Pobjoy radial engine have generated a number of
private messages which indicate some subscribers to this Newsgroup
lack a basic understanding in how the Internal Combustion engine
actually works. For example ALL engines have some degree of overlap
in their cam timing. If you have a text book that says otherwise, it
is in error.

The reason for this overlap is fairly simple: The incoming fuel/air
charge has mass and all mass has inertia. If the cam did not open the
intake valve until TDC there would be no in-flow of the fuel-air
charge until several degrees of crankshaft rotation AFTER the valve
opens because it takes that long for the difference in PRESSURE
between the combustion chamber and the inlet manifold to overcome the
inertia inherent in the fuel/air charge.

By the same token, the exhaust valve must remain OPEN for several
degrees past TDC for the pressure in the combustion chamber to fall to
a value equal to or less than that of the inlet manifold. Without
that difference in pressure there can be no flow.

The amount of overlap determines the engine's maximum rpm. If you
want an engine that turns 6,000 rpm, it would have to have an
appreciable amount of overlap.

The opening and closing of a valve takes the SAME amount of time,
regardless of the speed of the engine. Factors that effect the RATE
at which the valves open or close is the MASS or weight of the
components in the system, meaning the tappet, push-rod and valve, as
well as the strength of the SPRING, the tension of which must be
overcome in order to OPEN either valve. And of course, if you want
the valve to CLOSE quickly, you will need a stronger spring, but you
must pay for that greater strength upon opening the valve.

The thought that OVERLAP will cause some of the fuel/air charge to be
drawn out the exhaust port is largely nonsense except for engines
having a great deal of overlap -- too much to allow the engine to be
installed in a normal car.

This matter becomes significant with small aircraft engines, or any
aircraft engine that drives the propeller directly. For such engines
the AVERAGE OVERLAP is 33 crankshaft degrees (14 on the INTAKE, 19 on
the EXHAUST) but for some geared engines the overlap may be as much as
95 degrees.

The R-Type Pobjoy used cam-rings giving an overlap of 15 degrees (4 on
the intake, 11 on the exhaust).

-R.S.Hoover

[Charlie[_2_]]

Veeduber wrote:
> To All:
>
> Recent posts about the Pobjoy radial engine have generated a number of
> private messages which indicate some subscribers to this Newsgroup
> lack a basic understanding in how the Internal Combustion engine
> actually works. For example ALL engines have some degree of overlap
> in their cam timing. If you have a text book that says otherwise, it
> is in error.
>
> The reason for this overlap is fairly simple: The incoming fuel/air
> charge has mass and all mass has inertia. If the cam did not open the
> intake valve until TDC there would be no in-flow of the fuel-air
> charge until several degrees of crankshaft rotation AFTER the valve
> opens because it takes that long for the difference in PRESSURE
> between the combustion chamber and the inlet manifold to overcome the
> inertia inherent in the fuel/air charge.
>
> By the same token, the exhaust valve must remain OPEN for several
> degrees past TDC for the pressure in the combustion chamber to fall to
> a value equal to or less than that of the inlet manifold. Without
> that difference in pressure there can be no flow.
>
> The amount of overlap determines the engine's maximum rpm. If you
> want an engine that turns 6,000 rpm, it would have to have an
> appreciable amount of overlap.
***
> The opening and closing of a valve takes the SAME amount of time,
***
> regardless of the speed of the engine. Factors that effect the RATE
> at which the valves open or close is the MASS or weight of the
> components in the system, meaning the tappet, push-rod and valve, as
> well as the strength of the SPRING, the tension of which must be
> overcome in order to OPEN either valve. And of course, if you want
> the valve to CLOSE quickly, you will need a stronger spring, but you
> must pay for that greater strength upon opening the valve.
>
> The thought that OVERLAP will cause some of the fuel/air charge to be
> drawn out the exhaust port is largely nonsense except for engines
> having a great deal of overlap -- too much to allow the engine to be
> installed in a normal car.
>
> This matter becomes significant with small aircraft engines, or any
> aircraft engine that drives the propeller directly. For such engines
> the AVERAGE OVERLAP is 33 crankshaft degrees (14 on the INTAKE, 19 on
> the EXHAUST) but for some geared engines the overlap may be as much as
> 95 degrees.
>
> The R-Type Pobjoy used cam-rings giving an overlap of 15 degrees (4 on
> the intake, 11 on the exhaust).
>
> -R.S.Hoover
You might edit the line between the ***'s to say 'same degrees of crank
rotation'. (Time obviously varies with rpm.)

Charlie

[Veeduber[_2_]]

On Jun 9, 9:47*am, Veeduber > wrote:
> To All:
>
> Recent posts about the Pobjoy radial engine have generated a number of
> private messages which indicate some subscribers to this Newsgroup
> lack a basic understanding in how the Internal Combustion engine
> actually works. *For example ALL engines have some degree of overlap
> in their cam timing. *If you have a text book that says otherwise, it
> is in error.
>
> The reason for this overlap is fairly simple: *The incoming fuel/air
> charge has mass and all mass has inertia. *If the cam did not open the
> intake valve until TDC there would be no in-flow of the fuel-air
> charge until several degrees of crankshaft rotation AFTER the valve
> opens because it takes that long for the difference in PRESSURE
> between the combustion chamber and the inlet manifold to overcome the
> inertia inherent in the fuel/air charge.
>
> By the same token, the exhaust valve must remain OPEN for several
> degrees past TDC for the pressure in the combustion chamber to fall to
> a value equal to or less than that of the inlet manifold. *Without
> that difference in pressure there can be no flow.
>
> The amount of overlap determines the engine's maximum rpm. *If you
> want an engine that turns 6,000 rpm, it would have to have an
> appreciable amount of overlap.
>
> The opening and closing of a valve takes the SAME amount of crank rotation,
> regardless of the speed of the engine. *Factors that effect the RATE
> at which the valves open or close is the MASS or weight of the
> components in the system, meaning the tappet, push-rod and valve, as
> well as the strength of the SPRING, the tension of which must be
> overcome in order to OPEN either valve. *And of course, if you want
> the valve to CLOSE quickly, you will need a stronger spring, *but you
> must pay for that greater strength upon opening the valve.
>
> The thought that OVERLAP will cause some of the fuel/air charge to be
> drawn out the exhaust port is largely nonsense except for engines
> having a great deal of overlap -- too much to allow the engine to be
> installed in a normal car.
>
> This matter becomes significant with small aircraft engines, or any
> aircraft engine that drives the propeller directly. *For such engines
> the AVERAGE OVERLAP is 33 crankshaft degrees (14 on the INTAKE, 19 on
> the EXHAUST) but for some geared engines the overlap may be as much as
> 95 degrees.
>
> The R-Type Pobjoy used cam-rings giving an overlap of 15 degrees (4 on
> the intake, 11 on the exhaust).
>
> -R.S.Hoover

[Veeduber[_2_]]

On Jun 9, 4:16*pm, Charlie > wrote:

> You might edit the line between the ***'s to say 'same degrees of crank
> rotation'. (Time obviously varies with rpm.)
>---------------------------------------------------------------------------------------

Dear Charlie,

Thank you for the heads-up. Big day at the doctor shop today. (Good
news, too) But there's really no excuse for not re-reading this stuff
before posting it.

-Bob

[Tom Wait]

"Veeduber" > wrote

> Factors that effect the RATE
> at which the valves open or close is the MASS or weight of the
> components in the system, meaning the tappet, push-rod and valve, as
> well as the strength of the SPRING, the tension of which must be
> overcome in order to OPEN either valve. And of course, if you want
> the valve to CLOSE quickly, you will need a stronger spring, but you
> must pay for that greater strength upon opening the valve.
>
> -R.S.Hoover

I'm going to go out on a limb here Bob and say that the RATE of valve
opening and closing is a function of RPM and cam lobe contour only. Mass of
the valve train would primarily affect the max RPM attainable without
destructive valve float.
Tom

[Veeduber[_2_]]

(deleted)

[Veeduber[_2_]]

On Jun 9, 8:35*pm, "Tom Wait" >
wrote:

> I'm going to go out on a limb here Bob and say that the RATE of valve
> opening and closing is a function of RPM and cam lobe contour only. Mass of
> the valve train would primarily affect the max RPM attainable without
> destructive valve float.
>-------------------------------------------------------------------------------------------------------

Dear Tom,

Not a problem. There's plenty of room on the limb for the two of us.
(See my error as caught by Charlie.)

With regard to the rate at which the valve opens, what I'm trying to
say is that a valve train having greater mass will open more slowly
than a valve train having less mass. The assumption here is that all
else -- including the factor you've mentioned -- are equal.

The object here was ways to increase Volumetric Efficiency, for which
the rate at which the cylinder fills is a critical factor. According
to Taylor (or possibly Litton) the shape of the combustion chamber,
especially with regard to the shrouding of the intake valve, AND the
mass of the valve train components, are the only ways of improving VE
without going to super-charging.

I can see where you're coming from with regard to RPM but as you must
know, VE falls as rpm increases. The idea behind lighter valve train
components is to allow more time for charging the cylinder at a given
RPM. For the purpose of this exercise, RPM is fixed.

So put away the saw -- there's plenty of room for the two of us on
this branch :-)

In a more serious vein, I apologize for stating my explanation so
poorly.

-R.S.Hoover

[cmyr]

Going back to some hot rodding roots,I believe V.E. was increased
in the late '60's-70's thru the use of a specially designed double
cone affair placed in the collector pipe of a tuned exhaust
system,which created a stronger vacuum effect , creating stronger
scavenging of exhaust, and to some extent , helping draw more fuel/air
mix into the cylinder.

[George]

I believe that Ballenger Headers had the "pickle" located in the
collector of 4 tube equal length headers and there was also the
"coanda" effect which is specifically what I think you were speaking of.
It was used experimentally in a truly weird exhaust setup in the early
days by of one of the major racing teams back in the mid 60s, but my
memory is a bit foggy for specifics that far back, such as who or on
what car, sorry.


cmyr wrote:
> Going back to some hot rodding roots,I believe V.E. was increased
> in the late '60's-70's thru the use of a specially designed double
> cone affair placed in the collector pipe of a tuned exhaust
> system,which created a stronger vacuum effect , creating stronger
> scavenging of exhaust, and to some extent , helping draw more fuel/air
> mix into the cylinder.
>

[cmyr]

On Jun 11, 11:32�am, George > wrote:
> I believe that Ballenger Headers had the "pickle" located in the
> collector of 4 tube equal length headers and there was also the
> "coanda" effect which is specifically what I think you were speaking of.
> � It was used experimentally in a truly weird exhaust setup in the early
> days by of one of the major racing teams back in the mid 60s, but my
> memory is a bit foggy for specifics that far back, such as who or on
> what car, sorry.
>
>
>
> cmyr wrote:
> > � �Going back to some hot rodding roots,I believe V.E. was increased
> > in the late '60's-70's thru the use of a specially designed double
> > cone affair placed in the collector pipe of a tuned exhaust
> > system,which created a stronger vacuum effect , creating stronger
> > scavenging of exhaust, and to some extent , helping draw more fuel/air
> > mix into the cylinder.- Hide quoted text -
>
> - Show quoted text -

You remembered the word I couldn't put my finger on........coanda

[Tim[_8_]]

"cmyr" > wrote in message
...
On Jun 11, 11:32?am, George > wrote:
> I believe that Ballenger Headers had the "pickle" located in the
> collector of 4 tube equal length headers and there was also the
> "coanda" effect which is specifically what I think you were speaking of.
> ? It was used experimentally in a truly weird exhaust setup in the early
> days by of one of the major racing teams back in the mid 60s, but my
> memory is a bit foggy for specifics that far back, such as who or on
> what car, sorry.
>
>
>
> cmyr wrote:
> > ? ?Going back to some hot rodding roots,I believe V.E. was increased
> > in the late '60's-70's thru the use of a specially designed double
> > cone affair placed in the collector pipe of a tuned exhaust
> > system,which created a stronger vacuum effect , creating stronger
> > scavenging of exhaust, and to some extent , helping draw more fuel/air
> > mix into the cylinder.- Hide quoted text -
>
> - Show quoted text -

You remembered the word I couldn't put my finger on........coanda

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

Back in the 70s or so, there was a three cylinder two stroke radial, with
all three cylinders in a common crank case - that used the exhaust system
exclusively for scavenging the engine. There was no intake draft without it.

It was featured on an ultralight one year at OSH.

[Peter Dohm]

"cmyr" > wrote in message
...
> Going back to some hot rodding roots,I believe V.E. was increased
> in the late '60's-70's thru the use of a specially designed double
> cone affair placed in the collector pipe of a tuned exhaust
> system,which created a stronger vacuum effect , creating stronger
> scavenging of exhaust, and to some extent , helping draw more fuel/air
> mix into the cylinder.
>
There have been a number of things that improved VE: Generally, higher
compression ratios help especially at higher RPM, roller tappets seem to
withstand much faster ramp angles and can stay open further during the open
part of the valve cycles, and anti-reversion cones in the exhaust are said
to work very well in the mid-range of RPM for any given four cycle engine.
In addition, intake and exhaust port shapes play a major role; as do other
aspects of head ad piston crown design.

In a nut-shell, there has been a lot of progress over the past three
quarters of a century, and the only place that I can think of in which
aircraft engines have led the way has been in the area that we used to call
"blue printing" in which the ports are more carefully caste, machined, and
finished to closely match the design drawings for the engine. Today, every
late model engine that I have seen is done that way at the factory; but
forty years ago, automotive engines were really crude.

Peter

[[email protected]]

On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
> wrote:

> Going back to some hot rodding roots,I believe V.E. was increased
>in the late '60's-70's thru the use of a specially designed double
>cone affair placed in the collector pipe of a tuned exhaust
>system,which created a stronger vacuum effect , creating stronger
>scavenging of exhaust, and to some extent , helping draw more fuel/air
>mix into the cylinder.

The anti reversion cone was a dirty fix for a crappy header design.
Better than a manifold, but not as good as a proper "tuned" header.

[cmyr]

On Jun 11, 8:06�pm, wrote:
> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>
> > wrote:
> > � Going back to some hot rodding roots,I believe V.E. was increased
> >in the late '60's-70's thru the use of a specially designed double
> >cone affair placed in the collector pipe of a tuned exhaust
> >system,which created a stronger vacuum effect , creating stronger
> >scavenging of exhaust, and to some extent , helping draw more fuel/air
> >mix into the cylinder.
>
> The anti reversion cone was a dirty fix for a crappy header design.
> Better than a manifold, but not as good as a proper "tuned" header.

As I recall, this system was on the cover of Hot Rod magazine, on a
high end test vehicle,and was "scientifically" researched. In this
instance the reference to a crappy header design would be wrong.

[Tom Wait]

"cmyr" > wrote in message
...
On Jun 11, 8:06?pm, wrote:
> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>
> > wrote:
> > ? Going back to some hot rodding roots,I believe V.E. was increased
> >in the late '60's-70's thru the use of a specially designed double
> >cone affair placed in the collector pipe of a tuned exhaust
> >system,which created a stronger vacuum effect , creating stronger
> >scavenging of exhaust, and to some extent , helping draw more fuel/air
> >mix into the cylinder.
>
> The anti reversion cone was a dirty fix for a crappy header design.
> Better than a manifold, but not as good as a proper "tuned" header.

As I recall, this system was on the cover of Hot Rod magazine, on a
high end test vehicle,and was "scientifically" researched. In this
instance the reference to a crappy header design would be wrong.

All the previous 6 or7 posters have come up with methods of increasing VE
w/o superchargers. I want to add 4 or more valves per cylinder which would
probably increase the mass of the valve train. Certainly the complexity. I
don't see how a massive rocker arm or longer fatter pushrod could decrease
VE. Certainly a larger valve head would increase mass but would also
increase VE. A thicker valve stem would increase mass and decrease VE but I
think only marginally. I think the only way more mass would decrease VE
would be if the push rods were rubber.
Tom

[Torn Lawence]

Tom Wait wrote:
> "cmyr" > wrote in message
> ...
> On Jun 11, 8:06?pm, wrote:
>> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>>
>> > wrote:
>>> ? Going back to some hot rodding roots,I believe V.E. was increased
>>> in the late '60's-70's thru the use of a specially designed double
>>> cone affair placed in the collector pipe of a tuned exhaust
>>> system,which created a stronger vacuum effect , creating stronger
>>> scavenging of exhaust, and to some extent , helping draw more fuel/air
>>> mix into the cylinder.
>> The anti reversion cone was a dirty fix for a crappy header design.
>> Better than a manifold, but not as good as a proper "tuned" header.
>
> As I recall, this system was on the cover of Hot Rod magazine, on a
> high end test vehicle,and was "scientifically" researched. In this
> instance the reference to a crappy header design would be wrong.
>
> All the previous 6 or7 posters have come up with methods of increasing VE
> w/o superchargers. I want to add 4 or more valves per cylinder which would
> probably increase the mass of the valve train. Certainly the complexity. I
> don't see how a massive rocker arm or longer fatter pushrod could decrease
> VE. Certainly a larger valve head would increase mass but would also
> increase VE. A thicker valve stem would increase mass and decrease VE but I
> think only marginally. I think the only way more mass would decrease VE
> would be if the push rods were rubber.
> Tom

The British made some WWII engines with rotating cylinder sleeves that
had in and out ports cut into them - rotary valves! No poppets. Good
performance, but burned oil and left conspicuous smoke trails, not a
good thing for a warbird to do.

That's what I remember from an engine class, unless I'm hallucinating again.

[Gerry van Dyk]

Ah yes the "sleeve valve" engine

Bristol's Hercules in the radial engined Halifax and Lancaster
bombers, and Centaurus in the Sea Fury and several transports. Also
the Napier Sabre in the Hawker Typhoon and early Tempest.

The Centaurus turned into a real workhorse, but the Sabre died out
quickly. The Brits seem to keep the Bristols in service in warbirds
but American's tend to replace them with R-3350s, presumably for
spares availability this side of the pond.

Gerry

On Jun 12, 3:55*pm, Torn Lawence > wrote:
> Tom Wait wrote:
> > "cmyr" > wrote in message
> ....
> > On Jun 11, 8:06?pm, wrote:
> >> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>
> >> > wrote:
> >>> ? Going back to some hot rodding roots,I believe V.E. was increased
> >>> in the late '60's-70's thru the use of a specially designed double
> >>> cone affair placed in the collector pipe of a tuned exhaust
> >>> system,which created a stronger vacuum effect , creating stronger
> >>> scavenging of exhaust, and to some extent , helping draw more fuel/air
> >>> mix into the cylinder.
> >> The anti reversion cone was a dirty fix for a crappy header design.
> >> Better than a manifold, but not as good as a proper "tuned" header.
>
> > As I recall, this system was on the cover of Hot Rod magazine, on a
> > high end test vehicle,and was "scientifically" researched. In this
> > instance the reference to a crappy header design would be wrong.
>
> > All the previous 6 or7 posters have come up with methods of increasing VE
> > w/o superchargers. I want to add 4 or more valves per cylinder which would
> > probably increase the mass of the valve train. Certainly the complexity.. I
> > don't see how a massive rocker arm or longer fatter pushrod could decrease
> > VE. Certainly a larger valve head would increase mass but would also
> > increase VE. A thicker valve stem would increase mass and decrease VE but I
> > think only marginally. I think the only way more mass would decrease VE
> > would be if the push rods were rubber.
> > Tom
>
> The British made some WWII engines with rotating cylinder sleeves that
> had in and out ports cut into them - rotary valves! No poppets. Good
> performance, but burned oil and left conspicuous smoke trails, not a
> good thing for a warbird to do.
>
> That's what I remember from an engine class, unless I'm hallucinating again.- Hide quoted text -
>
> - Show quoted text -

[Charles Vincent]

Torn Lawence wrote:
> The British made some WWII engines with rotating cylinder sleeves that
> had in and out ports cut into them - rotary valves! No poppets. Good
> performance, but burned oil and left conspicuous smoke trails, not a
> good thing for a warbird to do.
>
> That's what I remember from an engine class, unless I'm hallucinating
> again.

That was a sleeve valve engine, Harry Ricardo's magnum opus. The
Bristol Hercules and Centaurus. Wear was an issue they never did tackle.

Charles

[bildan]

On Jun 12, 4:27*pm, Gerry van Dyk > wrote:
> Ah yes the "sleeve valve" engine
>
> Bristol's Hercules in the radial engined Halifax and Lancaster
> bombers, and Centaurus in the Sea Fury and several transports. *Also
> the Napier Sabre in the Hawker Typhoon and early Tempest.
>
> The Centaurus turned into a real workhorse, but the Sabre died out
> quickly. *The Brits seem to keep the Bristols in service in warbirds
> but American's tend to replace them with R-3350s, presumably for
> spares availability this side of the pond.
>
> Gerry
>
> On Jun 12, 3:55*pm, Torn Lawence > wrote:
>
> > Tom Wait wrote:
> > > "cmyr" > wrote in message
> > ....
> > > On Jun 11, 8:06?pm, wrote:
> > >> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>
> > >> > wrote:
> > >>> ? Going back to some hot rodding roots,I believe V.E. was increased
> > >>> in the late '60's-70's thru the use of a specially designed double
> > >>> cone affair placed in the collector pipe of a tuned exhaust
> > >>> system,which created a stronger vacuum effect , creating stronger
> > >>> scavenging of exhaust, and to some extent , helping draw more fuel/air
> > >>> mix into the cylinder.
> > >> The anti reversion cone was a dirty fix for a crappy header design.
> > >> Better than a manifold, but not as good as a proper "tuned" header.
>
> > > As I recall, this system was on the cover of Hot Rod magazine, on a
> > > high end test vehicle,and was "scientifically" researched. In this
> > > instance the reference to a crappy header design would be wrong.
>
> > > All the previous 6 or7 posters have come up with methods of increasing VE
> > > w/o superchargers. I want to add 4 or more valves per cylinder which would
> > > probably increase the mass of the valve train. Certainly the complexity. I
> > > don't see how a massive rocker arm or longer fatter pushrod could decrease
> > > VE. Certainly a larger valve head would increase mass but would also
> > > increase VE. A thicker valve stem would increase mass and decrease VE but I
> > > think only marginally. I think the only way more mass would decrease VE
> > > would be if the push rods were rubber.
> > > Tom
>
> > The British made some WWII engines with rotating cylinder sleeves that
> > had in and out ports cut into them - rotary valves! No poppets. Good
> > performance, but burned oil and left conspicuous smoke trails, not a
> > good thing for a warbird to do.
>
> > That's what I remember from an engine class, unless I'm hallucinating again.- Hide quoted text -
>
> > - Show quoted text -

If you ignore oil consumption, (No one succeeded in fixing that
problem.) Bristol sleeve valve radials had a lot to recommend
them. Maybe today with modern metallurgy and high temperature
elastomers someone could.

However, without poppet valves and rocker towers in the heads, the
engine diameter was much smaller. Without a hot exhaust valve in the
combustion chamber, the compression ratio could be a point or two
higher with the same octane fuel and the same detonation margins - and
the engine tended to last longer. At the time, and maybe still,
poppet exhaust valves were the weak point.

They have Sir Harry Ricardo to thank for the sleeve valve design.

[Morgans[_2_]]

"Charles Vincent" > wrote in message
...
> Torn Lawence wrote:
> > The British made some WWII engines with rotating cylinder sleeves that
>> had in and out ports cut into them - rotary valves! No poppets. Good
>> performance, but burned oil and left conspicuous smoke trails, not a good
>> thing for a warbird to do.
>>
>> That's what I remember from an engine class, unless I'm hallucinating again.
>
> That was a sleeve valve engine, Harry Ricardo's magnum opus. The Bristol
> Hercules and Centaurus. Wear was an issue they never did tackle.

When engines were changed as often as shirts, and as easily as shoes, that isn't
a big issue either, IMHO.

You have always got spares sitting around wherever you stop frequently, and in
an hour or so, you put in a new engine and are on your way.
--
Jim in NC

[[email protected]]

On Fri, 12 Jun 2009 06:05:01 -0700 (PDT), cmyr
> wrote:

>On Jun 11, 8:06?pm, wrote:
>> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>>
>> > wrote:
>> > ? Going back to some hot rodding roots,I believe V.E. was increased
>> >in the late '60's-70's thru the use of a specially designed double
>> >cone affair placed in the collector pipe of a tuned exhaust
>> >system,which created a stronger vacuum effect , creating stronger
>> >scavenging of exhaust, and to some extent , helping draw more fuel/air
>> >mix into the cylinder.
>>
>> The anti reversion cone was a dirty fix for a crappy header design.
>> Better than a manifold, but not as good as a proper "tuned" header.
>
>As I recall, this system was on the cover of Hot Rod magazine, on a
>high end test vehicle,and was "scientifically" researched. In this
>instance the reference to a crappy header design would be wrong.


I stand by my appraisal. It made a crappy header design work (sorta).
Just because it was on the cover of hot rod doesn't make it good. It
was a lot better than the standard "shortie" header without the cones
- but still nowhere near a properly tuned long header.

[[email protected]]

On Fri, 12 Jun 2009 13:12:48 -0500, "Tom Wait"
> wrote:

>
>"cmyr" > wrote in message
...
>On Jun 11, 8:06?pm, wrote:
>> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>>
>> > wrote:
>> > ? Going back to some hot rodding roots,I believe V.E. was increased
>> >in the late '60's-70's thru the use of a specially designed double
>> >cone affair placed in the collector pipe of a tuned exhaust
>> >system,which created a stronger vacuum effect , creating stronger
>> >scavenging of exhaust, and to some extent , helping draw more fuel/air
>> >mix into the cylinder.
>>
>> The anti reversion cone was a dirty fix for a crappy header design.
>> Better than a manifold, but not as good as a proper "tuned" header.
>
>As I recall, this system was on the cover of Hot Rod magazine, on a
>high end test vehicle,and was "scientifically" researched. In this
>instance the reference to a crappy header design would be wrong.
>
>All the previous 6 or7 posters have come up with methods of increasing VE
>w/o superchargers. I want to add 4 or more valves per cylinder which would
>probably increase the mass of the valve train. Certainly the complexity. I
>don't see how a massive rocker arm or longer fatter pushrod could decrease
>VE. Certainly a larger valve head would increase mass but would also
>increase VE. A thicker valve stem would increase mass and decrease VE but I
>think only marginally. I think the only way more mass would decrease VE
>would be if the push rods were rubber.
>Tom
>
Heavy valve trains only affect VE at high RPM - when the valves start
to float. Light valve-trains are better at high RPM, but are not
terribly effective in improving the power of a low speed "tractor
engine"

[Peter Dohm]

"Morgans" > wrote in message
...
>
> "Charles Vincent" > wrote in message
> ...
>> Torn Lawence wrote:
>> > The British made some WWII engines with rotating cylinder sleeves that
>>> had in and out ports cut into them - rotary valves! No poppets. Good
>>> performance, but burned oil and left conspicuous smoke trails, not a
>>> good thing for a warbird to do.
>>>
>>> That's what I remember from an engine class, unless I'm hallucinating
>>> again.
>>
>> That was a sleeve valve engine, Harry Ricardo's magnum opus. The Bristol
>> Hercules and Centaurus. Wear was an issue they never did tackle.
>
> When engines were changed as often as shirts, and as easily as shoes, that
> isn't a big issue either, IMHO.
>
> You have always got spares sitting around wherever you stop frequently,
> and in an hour or so, you put in a new engine and are on your way.
> --
> Jim in NC
While I would have phrased it a little differently, I am certainly on the
same page.

During the war, a little more horsepower was a far greater asset than longer
TBO,
and enemy fire was at least as great a threat as wear.

Peter

[Peter Dohm]

> wrote in message
...
> On Fri, 12 Jun 2009 06:05:01 -0700 (PDT), cmyr
> > wrote:
>
>>On Jun 11, 8:06?pm, wrote:
>>> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>>>
>>> > wrote:
>>> > ? Going back to some hot rodding roots,I believe V.E. was increased
>>> >in the late '60's-70's thru the use of a specially designed double
>>> >cone affair placed in the collector pipe of a tuned exhaust
>>> >system,which created a stronger vacuum effect , creating stronger
>>> >scavenging of exhaust, and to some extent , helping draw more fuel/air
>>> >mix into the cylinder.
>>>
>>> The anti reversion cone was a dirty fix for a crappy header design.
>>> Better than a manifold, but not as good as a proper "tuned" header.
>>
>>As I recall, this system was on the cover of Hot Rod magazine, on a
>>high end test vehicle,and was "scientifically" researched. In this
>>instance the reference to a crappy header design would be wrong.
>
>
> I stand by my appraisal. It made a crappy header design work (sorta).
> Just because it was on the cover of hot rod doesn't make it good. It
> was a lot better than the standard "shortie" header without the cones
> - but still nowhere near a properly tuned long header.

I agree with you about placement on the cover of Hot Rod, and the same
applies to most other publications: the ability of a writer to meet regular
and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.

Notwithstanding that cones were also tried as part of a "shortie" header
system, and may have been a little more or less usefull than "stepped"
pipes, there might be few modern applications aside from professional drag
racing and tractor pulls. Of course, you could argue that the exhaust on
the Merlin and Griffin, and also the Allison V12 of which I can not recall
the name, acted as untapered cones.

OTOH, most of the what I can recall from those days is related to OEM
advertising, mainly by Ford, to the light and medium truck market and
friends told me at the time that the use of anit reversion cones on truck
engines was far more widespread than I supposed and certainly not limited to
a single brand. However, I never personally had nearly new engines apart
and I don't know whether the cones may have appeared on the scene at the
same time that head castings became much more accurate. Recall that the
iron heads from the fifties and early sixties had very irregular ports and
the resulting outlets were smaller than the gaskets and headers--effectively
giving them a marginally predictable anti reverson property along with their
poor efficiency at higher speeds.

In other words, they are part of a compromise that may be usefull or may
not, depending on the application and the space available to mount the
engine along with its accessories and its exhaust and cooling systems.

[RST Engineering - JIm]

the ability of a writer to meet regular
> and repeated deadlines is a far more important qualification than
> outstanding knowledge of a subject.
>

Snurf , sniffle, ... {:-(

Jim
Monthly Columnist
Kitplanes

[Dan[_12_]]

Peter Dohm wrote:
<snip>
>
> I agree with you about placement on the cover of Hot Rod, and the same
> applies to most other publications: the ability of a writer to meet regular
> and repeated deadlines is a far more important qualification than
> outstanding knowledge of a subject.
>

I guess that depends on the publication in question not expecting
both. For example, Weir knows what he's talking about and makes a
monthly deadline every time.

Dan, U.S. Air Force, retired

[Brian Whatcott]

A couple of workshop manuals were part of my childhood - the trove of
my Fleet Arm Arm artificer brother - but I finally tossed them...

Brian W

Gerry van Dyk wrote:
> Ah yes the "sleeve valve" engine
>
> Bristol's Hercules in the radial engined Halifax and Lancaster
> bombers, and Centaurus in the Sea Fury and several transports. Also
> the Napier Sabre in the Hawker Typhoon and early Tempest.
>
> The Centaurus turned into a real workhorse, but the Sabre died out
> quickly. The Brits seem to keep the Bristols in service in warbirds
> but American's tend to replace them with R-3350s, presumably for
> spares availability this side of the pond.
>
> Gerry
......
>> The British made some WWII engines with rotating cylinder sleeves that
>> had in and out ports cut into them - rotary valves! No poppets. Good
>> performance, but burned oil and left conspicuous smoke trails, not a
>> good thing for a warbird to do.
>>
>> That's what I remember from an engine class, unless I'm hallucinating again.- Hide quoted text -

[Brian Whatcott]

Charles Vincent wrote:
> Torn Lawence wrote:
> > The British made some WWII engines with rotating cylinder sleeves that
>> had in and out ports cut into them - rotary valves! No poppets. Good
>> performance, but burned oil and left conspicuous smoke trails, not a
>> good thing for a warbird to do.
>>
>> That's what I remember from an engine class, unless I'm hallucinating
>> again.
>
> That was a sleeve valve engine, Harry Ricardo's magnum opus. The
> Bristol Hercules and Centaurus. Wear was an issue they never did tackle.
>
> Charles

Ricardo! Reminds me of those current amusing INTEL commercials with the
theme;
"Our pop-stars are not like your pop-stars..."

Brian W

[Peter Dohm]

"RST Engineering - JIm" > wrote in message
...
> the ability of a writer to meet regular
>> and repeated deadlines is a far more important qualification than
>> outstanding knowledge of a subject.
>>
>
> Snurf , sniffle, ... {:-(
>
> Jim
> Monthly Columnist
> Kitplanes
>
Oh c'mon!

You are far more of a doer than a writer.

Peter

[Peter Dohm]

"Dan" > wrote in message
...
> Peter Dohm wrote:
> <snip>
>>
>> I agree with you about placement on the cover of Hot Rod, and the same
>> applies to most other publications: the ability of a writer to meet
>> regular and repeated deadlines is a far more important qualification than
>> outstanding knowledge of a subject.
>>
>
> I guess that depends on the publication in question not expecting both.
> For example, Weir knows what he's talking about and makes a monthly
> deadline every time.
>
> Dan, U.S. Air Force, retired

True, and I frequently wish that I could do so as well.

Regrettably, it is not universally true, even in the specialized media and
it seems to be much worse in the popular "mainstream"!

Peter

[Dan D[_2_]]

"Charles Vincent" > wrote in message ...
> Torn Lawence wrote:
> > The British made some WWII engines with rotating cylinder sleeves that
>> had in and out ports cut into them - rotary valves! No poppets. Good
>> performance, but burned oil and left conspicuous smoke trails, not a
>> good thing for a warbird to do.
>>
>> That's what I remember from an engine class, unless I'm hallucinating
>> again.
>
> That was a sleeve valve engine, Harry Ricardo's magnum opus. The
> Bristol Hercules and Centaurus. Wear was an issue they never did tackle.
>
> Charles

They still live today, but in a different form?

http://www.rcvengines.com/corporate/rcv_technology.htm

[[email protected]]

On Fri, 12 Jun 2009 14:55:48 -0700, Torn Lawence >
wrote:

>Tom Wait wrote:
>> "cmyr" > wrote in message
>> ...
>> On Jun 11, 8:06?pm, wrote:
>>> On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr
>>>
>>> > wrote:
>>>> ? Going back to some hot rodding roots,I believe V.E. was increased
>>>> in the late '60's-70's thru the use of a specially designed double
>>>> cone affair placed in the collector pipe of a tuned exhaust
>>>> system,which created a stronger vacuum effect , creating stronger
>>>> scavenging of exhaust, and to some extent , helping draw more fuel/air
>>>> mix into the cylinder.
>>> The anti reversion cone was a dirty fix for a crappy header design.
>>> Better than a manifold, but not as good as a proper "tuned" header.
>>
>> As I recall, this system was on the cover of Hot Rod magazine, on a
>> high end test vehicle,and was "scientifically" researched. In this
>> instance the reference to a crappy header design would be wrong.
>>
>> All the previous 6 or7 posters have come up with methods of increasing VE
>> w/o superchargers. I want to add 4 or more valves per cylinder which would
>> probably increase the mass of the valve train. Certainly the complexity. I
>> don't see how a massive rocker arm or longer fatter pushrod could decrease
>> VE. Certainly a larger valve head would increase mass but would also
>> increase VE. A thicker valve stem would increase mass and decrease VE but I
>> think only marginally. I think the only way more mass would decrease VE
>> would be if the push rods were rubber.
>> Tom
>
>The British made some WWII engines with rotating cylinder sleeves that
>had in and out ports cut into them - rotary valves! No poppets. Good
>performance, but burned oil and left conspicuous smoke trails, not a
>good thing for a warbird to do.
>
>That's what I remember from an engine class, unless I'm hallucinating again.
the Knight sleeve valve engine, perchance?

[Torn Lawence]

Dan D wrote:
>
>
> "Charles Vincent" > wrote in message
> ...
>> Torn Lawence wrote:
>> > The British made some WWII engines with rotating cylinder sleeves that
>>> had in and out ports cut into them - rotary valves! No poppets. Good
>>> performance, but burned oil and left conspicuous smoke trails, not a
>>> good thing for a warbird to do.
>>>
>>> That's what I remember from an engine class, unless I'm hallucinating
>>> again.
>>
>> That was a sleeve valve engine, Harry Ricardo's magnum opus. The
>> Bristol Hercules and Centaurus. Wear was an issue they never did tackle.
>>
>> Charles
>
> They still live today, but in a different form?
>
> http://www.rcvengines.com/corporate/rcv_technology.htm

Now THAT'S interesting. They have some with the prop shaft as part of
the rotating cylinder head, instead of the crank.
http://www.rcvengines.com/rcv120sp.htm

[Dan D[_2_]]

"Charles Vincent" > wrote in message ...
> Torn Lawence wrote:
> > The British made some WWII engines with rotating cylinder sleeves that
>> had in and out ports cut into them - rotary valves! No poppets. Good
>> performance, but burned oil and left conspicuous smoke trails, not a
>> good thing for a warbird to do.
>>
>> That's what I remember from an engine class, unless I'm hallucinating
>> again.
>
> That was a sleeve valve engine, Harry Ricardo's magnum opus. The
> Bristol Hercules and Centaurus. Wear was an issue they never did tackle.
>
> Charles

They still live today, but in a different form?

http://www.rcvengines.com/corporate/rcv_technology.htm

[John Ousterhout[_2_]]

Dan wrote:

> ... Weir knows what he's talking about ...

As long as it's Electronics or Aviation that he's talking about :-)

- J.O.-

[Jan Carlsson]

[QUOTE='Veeduber[_2_];695919']To All:

>For example ALL engines have some degree of overlap
in their cam timing. If you have a text book that says otherwise, it
is in error.<


No Not all engines have overlap, not early rotary radials with one pull/push rod operating the single rocker between the valves, opening one valve at the time, the valve clearence make it impossible to open both at the same time.

Jan

[[email protected]]

On Tue, 16 Jun 2009 19:54:20 +0100, Jan Carlsson
> wrote:

>
>'Veeduber[_2_ Wrote:
>> ;695919']To All:
>>
>> >For example ALL engines have some degree of overlap
>> in their cam timing. If you have a text book that says otherwise, it
>> is in error.<
>>
>>
>> No Not all engines have overlap, not early rotary radials with one
>> pull/push rod operating the single rocker between the valves, opening
>> one valve at the time, the valve clearence make it impossible to open
>> both at the same time.
>>
>> Jan
And then there is the "atmospheric" intake valve.

[coffelt2]

>>> Jan
> And then there is the "atmospheric" intake valve.

AKA "Wheeze valve" really worked great in 200 rpm
Vaughn Garden Tractors.

Knight sleeve valve engines suffered from carbon
build-up in the sleeve's ports. Oil and fire took their
toll.

60 years back, Ford flatheads didn't need headers.
just dispense with exhaust manifolds. (neighbors
withstanding)

Old Chief Lynn