This just appeared in one of my feeds:

---
In his book Not Much Of An Engineer, Rolls Royce supercharger designer
Stanley Hooker states that Ford UK looked at the Merlin engine drawings
and said "we can't build an engine to those tolerances." Hooker said
loftily (his words) " I suppose the tolerances are too tight for you?" "
No, they are much too loose - we use much tighter tolerances for car
engines so all the parts are truely interchangeable without any hand
adjustment needed."

Ford UK then spent a year redrawing all the Merlin engine drawings to
finer tolerances, and then built. 30,000 of them during the rest of the war.

"and they were very good engines too" said Hooker.

---

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On 2/04/2023 5:51 am, Trevor Wilson wrote:
> This just appeared in one of my feeds:
>
> ---
> In his book Not Much Of An Engineer, Rolls Royce supercharger designer
> Stanley Hooker states that Ford UK looked at the Merlin engine drawings
> and said "we can't build an engine to those tolerances." Hooker said
> loftily (his words) " I suppose the tolerances are too tight for you?" "
> No, they are much too loose - we use much tighter tolerances for car
> engines so all the parts are truely interchangeable without any hand
> adjustment needed."
>
> Ford UK then spent a year redrawing all the Merlin engine drawings to
> finer tolerances, and then built. 30,000 of them during the rest of the
> war.
>
> "and they were very good engines too" said Hooker.

I don't think the British would know what fine tolerances are. They've
never used any :)

--
--
--
Regards,
Noddy.

On 2/04/2023 5:51 am, Trevor Wilson wrote:
> This just appeared in one of my feeds:
>
> ---
> In his book Not Much Of An Engineer, Rolls Royce supercharger designer
> Stanley Hooker states that Ford UK looked at the Merlin engine drawings
> and said "we can't build an engine to those tolerances." Hooker said
> loftily (his words) " I suppose the tolerances are too tight for you?" "
> No, they are much too loose - we use much tighter tolerances for car
> engines so all the parts are truely interchangeable without any hand
> adjustment needed."
>
> Ford UK then spent a year redrawing all the Merlin engine drawings to
> finer tolerances, and then built. 30,000 of them during the rest of the
> war.
>
> "and they were very good engines too" said Hooker.

Rolls relied on rough machining and squads of poorly paid workers with
files to complete the job. That worked in the 30s if you weren't into
mass production.

Hooker's book is an excellent read on the subject if you are into that
sort of thing. He didn't do the original design for the supercharger,
but he took a mediocre design and transformed it. The original Merlins
only gave 800 odd bhp, by the end of the war it was 2000bhp, a lot of
that came from supercharger improvements.

Packard also made changes, I believe that they simplified the bolt and
screw inventory, Rolls had apparently used every size and thread known
to man.

On 13/04/2023 9:59 pm, Keithr0 wrote:
> On 2/04/2023 5:51 am, Trevor Wilson wrote:
>> This just appeared in one of my feeds:
>>
>> ---
>> In his book Not Much Of An Engineer, Rolls Royce supercharger designer
>> Stanley Hooker states that Ford UK looked at the Merlin engine
>> drawings and said "we can't build an engine to those tolerances."
>> Hooker said loftily (his words) " I suppose the tolerances are too
>> tight for you?" " No, they are much too loose - we use much tighter
>> tolerances for car engines so all the parts are truely interchangeable
>> without any hand adjustment needed."
>>
>> Ford UK then spent a year redrawing all the Merlin engine drawings to
>> finer tolerances, and then built. 30,000 of them during the rest of
>> the war.
>>
>> "and they were very good engines too" said Hooker.
>
> Rolls relied on rough machining and squads of poorly paid workers with
> files to complete the job. That worked in the 30s if you weren't into
> mass production.
>
> Hooker's book is an excellent read on the subject if you are into that
> sort of thing. He didn't do the original design for the supercharger,
> but he took a mediocre design and transformed it. The original Merlins
> only gave 800 odd bhp, by the end of the war it was 2000bhp, a lot of
> that came from supercharger improvements.
>
> Packard also made changes, I believe that they simplified the bolt and
> screw inventory, Rolls had apparently used every size and thread known
> to man.
>

**I was under the impression that American, high octane fuel was a big
part of that power increase. Obviously engine mods would have been
required to cope with that high octane fuel.

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On 14/04/2023 5:57 am, Trevor Wilson wrote:
> On 13/04/2023 9:59 pm, Keithr0 wrote:

>> Packard also made changes, I believe that they simplified the bolt and
>> screw inventory, Rolls had apparently used every size and thread known
>> to man.
>>
>
> **I was under the impression that American, high octane fuel was a big
> part of that power increase. Obviously engine mods would have been
> required to cope with that high octane fuel.

It would have made the engines more stable, but it wouldn't have boosted
power in and of itself. It would have made the engines less likely to
detonate at high levels of boost.

--
--
--
Regards,
Noddy.

On 14/04/2023 5:57 am, Trevor Wilson wrote:
> On 13/04/2023 9:59 pm, Keithr0 wrote:
>> On 2/04/2023 5:51 am, Trevor Wilson wrote:
>>> This just appeared in one of my feeds:
>>>
>>> ---
>>> In his book Not Much Of An Engineer, Rolls Royce supercharger
>>> designer Stanley Hooker states that Ford UK looked at the Merlin
>>> engine drawings and said "we can't build an engine to those
>>> tolerances." Hooker said loftily (his words) " I suppose the
>>> tolerances are too tight for you?" " No, they are much too loose - we
>>> use much tighter tolerances for car engines so all the parts are
>>> truely interchangeable without any hand adjustment needed."
>>>
>>> Ford UK then spent a year redrawing all the Merlin engine drawings to
>>> finer tolerances, and then built. 30,000 of them during the rest of
>>> the war.
>>>
>>> "and they were very good engines too" said Hooker.
>>
>> Rolls relied on rough machining and squads of poorly paid workers with
>> files to complete the job. That worked in the 30s if you weren't into
>> mass production.
>>
>> Hooker's book is an excellent read on the subject if you are into that
>> sort of thing. He didn't do the original design for the supercharger,
>> but he took a mediocre design and transformed it. The original Merlins
>> only gave 800 odd bhp, by the end of the war it was 2000bhp, a lot of
>> that came from supercharger improvements.
>>
>> Packard also made changes, I believe that they simplified the bolt and
>> screw inventory, Rolls had apparently used every size and thread known
>> to man.
>>
>
> **I was under the impression that American, high octane fuel was a big
> part of that power increase. Obviously engine mods would have been
> required to cope with that high octane fuel.
>
Higher octane fuel allowed higher boost pressures to be used but did not
of itself add power.

This is a reasonable view of the Merlin development in a nutshell

https://en.wikipedia.org/wiki/Rolls-Royce_Merlin

Most of the power increases were due to supercharger improvements
leading to higher boost pressures(also better performance at altitude).
It is worth noting though that every little helps and pointing the
exhausts to the back gave the equivalent of a 70hp power increase.

On 15/4/2023 4:15 pm, Keithr0 wrote:
> On 14/04/2023 5:57 am, Trevor Wilson wrote:
>> On 13/04/2023 9:59 pm, Keithr0 wrote:
>>> On 2/04/2023 5:51 am, Trevor Wilson wrote:
>>>> This just appeared in one of my feeds:
>>>>
>>>> ---
>>>> In his book Not Much Of An Engineer, Rolls Royce supercharger
>>>> designer Stanley Hooker states that Ford UK looked at the Merlin
>>>> engine drawings and said "we can't build an engine to those
>>>> tolerances." Hooker said loftily (his words) " I suppose the
>>>> tolerances are too tight for you?" " No, they are much too loose -
>>>> we use much tighter tolerances for car engines so all the parts are
>>>> truely interchangeable without any hand adjustment needed."
>>>>
>>>> Ford UK then spent a year redrawing all the Merlin engine drawings
>>>> to finer tolerances, and then built. 30,000 of them during the rest
>>>> of the war.
>>>>
>>>> "and they were very good engines too" said Hooker.
>>>
>>> Rolls relied on rough machining and squads of poorly paid workers
>>> with files to complete the job. That worked in the 30s if you weren't
>>> into mass production.
>>>
>>> Hooker's book is an excellent read on the subject if you are into
>>> that sort of thing. He didn't do the original design for the
>>> supercharger, but he took a mediocre design and transformed it. The
>>> original Merlins only gave 800 odd bhp, by the end of the war it was
>>> 2000bhp, a lot of that came from supercharger improvements.
>>>
>>> Packard also made changes, I believe that they simplified the bolt
>>> and screw inventory, Rolls had apparently used every size and thread
>>> known to man.
>>>
>>
>> **I was under the impression that American, high octane fuel was a big
>> part of that power increase. Obviously engine mods would have been
>> required to cope with that high octane fuel.
>>
> Higher octane fuel allowed higher boost pressures to be used but did not
> of itself add power.

It enabled higher compression ratios, whether static of dynamic, hence
allowed for higher power output should the engine builder care to take
advantage of it. The higher octane fuel burns more slowly so, in order
to retain the same power, you need to advance the ignition timing, but
you do gain in slightly reduced fuel consumption. The advantage is when
you bump the compression ratio up to take advantage of the slower
burning fuel which is less prone to detonation. That is when you gain
*efficiency* and increase power output.
>
> This is a reasonable view of the Merlin development in a nutshell
>
> https://en.wikipedia.org/wiki/Rolls-Royce_Merlin
>
> Most of the power increases were due to supercharger improvements
> leading to higher boost pressures(also better performance at altitude).
> It is worth noting though that every little helps and pointing the
> exhausts to the back gave the equivalent of a 70hp power increase.
>
They also added a two stage blower and an aftercooler. The two stage
blower added less heat to the incoming air for the same given
pressurisation hence was more efficient vis a vis combustion. That and
the aftercooler would have enabled higher compression ratios by themselves.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 15/04/2023 10:04 pm, Xeno wrote:
> On 15/4/2023 4:15 pm, Keithr0 wrote:
>> On 14/04/2023 5:57 am, Trevor Wilson wrote:
>>> On 13/04/2023 9:59 pm, Keithr0 wrote:
>>>> On 2/04/2023 5:51 am, Trevor Wilson wrote:
>>>>> This just appeared in one of my feeds:
>>>>>
>>>>> ---
>>>>> In his book Not Much Of An Engineer, Rolls Royce supercharger
>>>>> designer Stanley Hooker states that Ford UK looked at the Merlin
>>>>> engine drawings and said "we can't build an engine to those
>>>>> tolerances." Hooker said loftily (his words) " I suppose the
>>>>> tolerances are too tight for you?" " No, they are much too loose -
>>>>> we use much tighter tolerances for car engines so all the parts are
>>>>> truely interchangeable without any hand adjustment needed."
>>>>>
>>>>> Ford UK then spent a year redrawing all the Merlin engine drawings
>>>>> to finer tolerances, and then built. 30,000 of them during the rest
>>>>> of the war.
>>>>>
>>>>> "and they were very good engines too" said Hooker.
>>>>
>>>> Rolls relied on rough machining and squads of poorly paid workers
>>>> with files to complete the job. That worked in the 30s if you
>>>> weren't into mass production.
>>>>
>>>> Hooker's book is an excellent read on the subject if you are into
>>>> that sort of thing. He didn't do the original design for the
>>>> supercharger, but he took a mediocre design and transformed it. The
>>>> original Merlins only gave 800 odd bhp, by the end of the war it was
>>>> 2000bhp, a lot of that came from supercharger improvements.
>>>>
>>>> Packard also made changes, I believe that they simplified the bolt
>>>> and screw inventory, Rolls had apparently used every size and thread
>>>> known to man.
>>>>
>>>
>>> **I was under the impression that American, high octane fuel was a
>>> big part of that power increase. Obviously engine mods would have
>>> been required to cope with that high octane fuel.
>>>
>> Higher octane fuel allowed higher boost pressures to be used but did
>> not of itself add power.
>
> It enabled higher compression ratios, whether static of dynamic, hence
> allowed for higher power output should the engine builder care to take
> advantage of it. The higher octane fuel burns more slowly so, in order
> to retain the same power, you need to advance the ignition timing, but
> you do gain in slightly reduced fuel consumption. The advantage is when
> you bump the compression ratio up to take advantage of the slower
> burning fuel which is less prone to detonation. That is when you gain
> *efficiency* and increase power output.

That may be true in general, but the compression ratio of the Merlin was
the same in all models - 6:1.
>>
>> This is a reasonable view of the Merlin development in a nutshell
>>
>> https://en.wikipedia.org/wiki/Rolls-Royce_Merlin
>>
>> Most of the power increases were due to supercharger improvements
>> leading to higher boost pressures(also better performance at
>> altitude). It is worth noting though that every little helps and
>> pointing the exhausts to the back gave the equivalent of a 70hp power
>> increase.
>>
> They also added a two stage blower and an aftercooler. The two stage
> blower added less heat to the incoming air for the same given
> pressurisation hence was more efficient vis a vis combustion. That and
> the aftercooler would have enabled higher compression ratios by themselves.
>
>
I am aware of what an intercooler does, in the case of the Merlin it was
an air to liquid type with it's own cooling loop and radiator
independent of the main cooling system and it was only present on
engines with the 2 stage blower. The 2 stage blower was mainly not added
to get more power, but to enable operation at higher altitude (30,000 ft
was the target), the same as the 2 speed blower which changed speed
automatically at a particular altitude. It could also be changed to high
speed in an emergency by the pilot pushing the throttle though a gate.
At low altitude the engine was not rated for more than 5 minutes on this
setting, but when you've got an Me109 up your arse, you don't care about
that.
On the Merlin 100 series, the 2 stage blower was redesigned and
incorporated single point fuel injection into the input of the first
stage of the blower. Rolls reckoned this was superior to the Daimler
Benz system of direct injection, as the fuel was fully evaporated when
the mixture entered the cylinder rather than as a liquid. The
evaporation of the fuel through the blower also helped to cool the mixture.

On 16/04/2023 9:05 pm, Noddy wrote:
> On 16/04/2023 5:25 pm, Keithr0 wrote:
>> On 15/04/2023 10:04 pm, Xeno wrote:
>
>>> It enabled higher compression ratios, whether static of dynamic,
>>> hence allowed for higher power output should the engine builder care
>>> to take advantage of it. The higher octane fuel burns more slowly so,
>>> in order to retain the same power, you need to advance the ignition
>>> timing, but you do gain in slightly reduced fuel consumption. The
>>> advantage is when you bump the compression ratio up to take advantage
>>> of the slower burning fuel which is less prone to detonation. That is
>>> when you gain *efficiency* and increase power output.
>>
>> That may be true in general, but the compression ratio of the Merlin
>> was the same in all models - 6:1.
>
> You'll do his mental head in by interfering with his irrelevant waffling
> by interrupting it with fact. You know that, right? :)
>
>>> They also added a two stage blower and an aftercooler. The two stage
>>> blower added less heat to the incoming air for the same given
>>> pressurisation hence was more efficient vis a vis combustion. That
>>> and the aftercooler would have enabled higher compression ratios by
>>> themselves.
>>>
>>>
>> I am aware of what an intercooler does, in the case of the Merlin it
>> was an air to liquid type with it's own cooling loop and radiator
>> independent of the main cooling system and it was only present on
>> engines with the 2 stage blower. The 2 stage blower was mainly not
>> added to get more power, but to enable operation at higher altitude
>> (30,000 ft was the target), the same as the 2 speed blower which
>> changed speed automatically at a particular altitude. It could also be
>> changed to high speed in an emergency by the pilot pushing the
>> throttle though a gate. At low altitude the engine was not rated for
>> more than 5 minutes on this setting, but when you've got an Me109 up
>> your arse, you don't care about that.
>
> No, you don't :)
>
> Pretty sure some American radials had these "War Emergency Power"
> settings available as well, and if I remember correctly I read (or most
> likely saw on some doco) that the later variants of the Me109 ran a
> water injection system to help avoid combustion problems in extreme
> situations.

Some FW190s had nitrous injection.

Our Neptune has Wright 3350 engines. 52 litre 18 cylinder radials, they
have water methanol injection that enables the use of 60" of boost when
using 135 octane fuel giving 3370 bhp.

>> On the Merlin 100 series, the 2 stage blower was redesigned and
>> incorporated single point fuel injection into the input of the first
>> stage of the blower. Rolls reckoned this was superior to the Daimler
>> Benz system of direct injection, as the fuel was fully evaporated when
>> the mixture entered the cylinder rather than as a liquid. The
>> evaporation of the fuel through the blower also helped to cool the
>> mixture.
>
> No doubt helped to lubricate it as well, which is something that carries
> over into mechanical blowers to this day. When running a "Rootes" type
> blower on any car engine, an in particular one that's had it's
> clearances tightened up to produce boost from just off idle, they get
> incredibly hot. The solution is to run them "wet" by way of adding fuel
> into the arflow ahead of the blower. Easy enough to do on a carburetted
> engine by just plonking the carb(s) straight on top of the blower, but
> the downside is that blowers tend to have a "corkscrew" effect on
> airflow and they push most of the fuel to the rear of the inlet manifold
> on a V8 engine.
>
> A way around the phenomena with an injected engine is to run a couple of
> "weter" injectors above the blower, and individual port injectors
> underneath. I'm working on one such system right now, and hopefully it
> will perform very well.

They may exist, but I've never seen an aero engine with a rootes blower,
centrifugal ones seem to be the preferred choice.

On 16/4/2023 9:05 pm, Noddy wrote:
> On 16/04/2023 5:25 pm, Keithr0 wrote:
>> On 15/04/2023 10:04 pm, Xeno wrote:
>
>>> It enabled higher compression ratios, whether static of dynamic,
>>> hence allowed for higher power output should the engine builder care
>>> to take advantage of it. The higher octane fuel burns more slowly so,
>>> in order to retain the same power, you need to advance the ignition
>>> timing, but you do gain in slightly reduced fuel consumption. The
>>> advantage is when you bump the compression ratio up to take advantage
>>> of the slower burning fuel which is less prone to detonation. That is
>>> when you gain *efficiency* and increase power output.
>>
>> That may be true in general, but the compression ratio of the Merlin
>> was the same in all models - 6:1.
>
> You'll do his mental head in by interfering with his irrelevant waffling
> by interrupting it with fact. You know that, right? :)
>
>>> They also added a two stage blower and an aftercooler. The two stage
>>> blower added less heat to the incoming air for the same given
>>> pressurisation hence was more efficient vis a vis combustion. That
>>> and the aftercooler would have enabled higher compression ratios by
>>> themselves.
>>>
>>>
>> I am aware of what an intercooler does, in the case of the Merlin it
>> was an air to liquid type with it's own cooling loop and radiator
>> independent of the main cooling system and it was only present on
>> engines with the 2 stage blower. The 2 stage blower was mainly not
>> added to get more power, but to enable operation at higher altitude
>> (30,000 ft was the target), the same as the 2 speed blower which
>> changed speed automatically at a particular altitude. It could also be
>> changed to high speed in an emergency by the pilot pushing the
>> throttle though a gate. At low altitude the engine was not rated for
>> more than 5 minutes on this setting, but when you've got an Me109 up
>> your arse, you don't care about that.
>
> No, you don't :)
>
> Pretty sure some American radials had these "War Emergency Power"
> settings available as well, and if I remember correctly I read (or most
> likely saw on some doco) that the later variants of the Me109 ran a
> water injection system to help avoid combustion problems in extreme
> situations.
>
>> On the Merlin 100 series, the 2 stage blower was redesigned and
>> incorporated single point fuel injection into the input of the first
>> stage of the blower. Rolls reckoned this was superior to the Daimler
>> Benz system of direct injection, as the fuel was fully evaporated when
>> the mixture entered the cylinder rather than as a liquid. The
>> evaporation of the fuel through the blower also helped to cool the
>> mixture.
>
> No doubt helped to lubricate it as well, which is something that carries
> over into mechanical blowers to this day. When running a "Rootes" type
> blower on any car engine, an in particular one that's had it's
> clearances tightened up to produce boost from just off idle, they get
> incredibly hot. The solution is to run them "wet" by way of adding fuel
> into the arflow ahead of the blower. Easy enough to do on a carburetted
> engine by just plonking the carb(s) straight on top of the blower, but
> the downside is that blowers tend to have a "corkscrew" effect on
> airflow and they push most of the fuel to the rear of the inlet manifold
> on a V8 engine.
>
> A way around the phenomena with an injected engine is to run a couple of
> "weter" injectors above the blower, and individual port injectors
> underneath. I'm working on one such system right now, and hopefully it
> will perform very well.
>
More delusions Darren?
--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 16/04/2023 9:32 pm, Keithr0 wrote:
> On 16/04/2023 9:05 pm, Noddy wrote:

>> A way around the phenomena with an injected engine is to run a couple
>> of "weter" injectors above the blower, and individual port injectors
>> underneath. I'm working on one such system right now, and hopefully it
>> will perform very well.
>
> They may exist, but I've never seen an aero engine with a rootes blower,
> centrifugal ones seem to be the preferred choice.

They do, and for what it's worth I've never seen one either. However
regardless of the type *all* mechanical superchargers get incredibly
hot, and running them "wet" helps keep that under control.

As an interesting aside, I mentioned a little while ago that I met the
bloke who was the crew chief on the Bayswater Bulk hydroplane (or at
least one of them) and had a few decent conversations about the Merlin
and it's use in that type of racing application. It was a long time ago
and I don't recall what variant of the Merlin they used other than it
being "ex RAAf", but he said that at the speeds they were turning the
engine it cost over 400 horsepower to drive the supercharger.

--
--
--
Regards,
Noddy.

Noddy <me@home.com> wrote in news:u1gkpa$2h4th$1@dont-email.me:

snip irrel

> A way around the phenomena with an injected engine is to run a couple
> of "weter" injectors above the blower, and individual port injectors
> underneath. I'm working on one such system right now,

Really Fraudster? It's not like you to pass up an opportunity to big
yourself by posting some happy snaps.

> and hopefully it will perform very well.

I'm sure that we'll hear all about it if it doesn't. [That be irony
Fraudster]

alvey

On 16/04/2023 5:25 pm, Keithr0 wrote:
> On 15/04/2023 10:04 pm, Xeno wrote:

>> It enabled higher compression ratios, whether static of dynamic, hence
>> allowed for higher power output should the engine builder care to take
>> advantage of it. The higher octane fuel burns more slowly so, in order
>> to retain the same power, you need to advance the ignition timing, but
>> you do gain in slightly reduced fuel consumption. The advantage is
>> when you bump the compression ratio up to take advantage of the slower
>> burning fuel which is less prone to detonation. That is when you gain
>> *efficiency* and increase power output.
>
> That may be true in general, but the compression ratio of the Merlin was
> the same in all models - 6:1.

You'll do his mental head in by interfering with his irrelevant waffling
by interrupting it with fact. You know that, right? :)

>> They also added a two stage blower and an aftercooler. The two stage
>> blower added less heat to the incoming air for the same given
>> pressurisation hence was more efficient vis a vis combustion. That and
>> the aftercooler would have enabled higher compression ratios by
>> themselves.
>>
>>
> I am aware of what an intercooler does, in the case of the Merlin it was
> an air to liquid type with it's own cooling loop and radiator
> independent of the main cooling system and it was only present on
> engines with the 2 stage blower. The 2 stage blower was mainly not added
> to get more power, but to enable operation at higher altitude (30,000 ft
> was the target), the same as the 2 speed blower which changed speed
> automatically at a particular altitude. It could also be changed to high
> speed in an emergency by the pilot pushing the throttle though a gate.
> At low altitude the engine was not rated for more than 5 minutes on this
> setting, but when you've got an Me109 up your arse, you don't care about
> that.

No, you don't :)

Pretty sure some American radials had these "War Emergency Power"
settings available as well, and if I remember correctly I read (or most
likely saw on some doco) that the later variants of the Me109 ran a
water injection system to help avoid combustion problems in extreme
situations.

> On the Merlin 100 series, the 2 stage blower was redesigned and
> incorporated single point fuel injection into the input of the first
> stage of the blower. Rolls reckoned this was superior to the Daimler
> Benz system of direct injection, as the fuel was fully evaporated when
> the mixture entered the cylinder rather than as a liquid. The
> evaporation of the fuel through the blower also helped to cool the mixture.

No doubt helped to lubricate it as well, which is something that carries
over into mechanical blowers to this day. When running a "Rootes" type
blower on any car engine, an in particular one that's had it's
clearances tightened up to produce boost from just off idle, they get
incredibly hot. The solution is to run them "wet" by way of adding fuel
into the arflow ahead of the blower. Easy enough to do on a carburetted
engine by just plonking the carb(s) straight on top of the blower, but
the downside is that blowers tend to have a "corkscrew" effect on
airflow and they push most of the fuel to the rear of the inlet manifold
on a V8 engine.

A way around the phenomena with an injected engine is to run a couple of
"weter" injectors above the blower, and individual port injectors
underneath. I'm working on one such system right now, and hopefully it
will perform very well.

--
--
--
Regards,
Noddy.

On 16/4/2023 9:05 pm, Noddy wrote:
> On 16/04/2023 5:25 pm, Keithr0 wrote:
>> On 15/04/2023 10:04 pm, Xeno wrote:
>
>>> It enabled higher compression ratios, whether static of dynamic,
>>> hence allowed for higher power output should the engine builder care
>>> to take advantage of it. The higher octane fuel burns more slowly so,
>>> in order to retain the same power, you need to advance the ignition
>>> timing, but you do gain in slightly reduced fuel consumption. The
>>> advantage is when you bump the compression ratio up to take advantage
>>> of the slower burning fuel which is less prone to detonation. That is
>>> when you gain *efficiency* and increase power output.
>>
>> That may be true in general, but the compression ratio of the Merlin
>> was the same in all models - 6:1.
>
> You'll do his mental head in by interfering with his irrelevant waffling
> by interrupting it with fact. You know that, right? :)
>
>>> They also added a two stage blower and an aftercooler. The two stage
>>> blower added less heat to the incoming air for the same given
>>> pressurisation hence was more efficient vis a vis combustion. That
>>> and the aftercooler would have enabled higher compression ratios by
>>> themselves.
>>>
>>>
>> I am aware of what an intercooler does, in the case of the Merlin it
>> was an air to liquid type with it's own cooling loop and radiator
>> independent of the main cooling system and it was only present on
>> engines with the 2 stage blower. The 2 stage blower was mainly not
>> added to get more power, but to enable operation at higher altitude
>> (30,000 ft was the target), the same as the 2 speed blower which
>> changed speed automatically at a particular altitude. It could also be
>> changed to high speed in an emergency by the pilot pushing the
>> throttle though a gate. At low altitude the engine was not rated for
>> more than 5 minutes on this setting, but when you've got an Me109 up
>> your arse, you don't care about that.
>
> No, you don't :)
>
> Pretty sure some American radials had these "War Emergency Power"
> settings available as well, and if I remember correctly I read (or most
> likely saw on some doco) that the later variants of the Me109 ran a
> water injection system to help avoid combustion problems in extreme
> situations.
>
>> On the Merlin 100 series, the 2 stage blower was redesigned and
>> incorporated single point fuel injection into the input of the first
>> stage of the blower. Rolls reckoned this was superior to the Daimler
>> Benz system of direct injection, as the fuel was fully evaporated when
>> the mixture entered the cylinder rather than as a liquid. The
>> evaporation of the fuel through the blower also helped to cool the
>> mixture.
>
> No doubt helped to lubricate it as well, which is something that carries
> over into mechanical blowers to this day. When running a "Rootes" type
> blower on any car engine, an in particular one that's had it's
> clearances tightened up to produce boost from just off idle, they get
> incredibly hot. The solution is to run them "wet" by way of adding fuel
> into the arflow ahead of the blower. Easy enough to do on a carburetted
> engine by just plonking the carb(s) straight on top of the blower, but
> the downside is that blowers tend to have a "corkscrew" effect on
> airflow and they push most of the fuel to the rear of the inlet manifold
> on a V8 engine.
>
> A way around the phenomena with an injected engine is to run a couple of
> "weter" injectors above the blower, and individual port injectors
> underneath. I'm working on one such system right now, and hopefully it
> will perform very well.
>
And along the way you might learn to recognise an intercooler as well.

Bonus, eh?

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 16/4/2023 9:32 pm, Keithr0 wrote:
> On 16/04/2023 9:05 pm, Noddy wrote:
>> On 16/04/2023 5:25 pm, Keithr0 wrote:
>>> On 15/04/2023 10:04 pm, Xeno wrote:
>>
>>>> It enabled higher compression ratios, whether static of dynamic,
>>>> hence allowed for higher power output should the engine builder care
>>>> to take advantage of it. The higher octane fuel burns more slowly
>>>> so, in order to retain the same power, you need to advance the
>>>> ignition timing, but you do gain in slightly reduced fuel
>>>> consumption. The advantage is when you bump the compression ratio up
>>>> to take advantage of the slower burning fuel which is less prone to
>>>> detonation. That is when you gain *efficiency* and increase power
>>>> output.
>>>
>>> That may be true in general, but the compression ratio of the Merlin
>>> was the same in all models - 6:1.
>>
>> You'll do his mental head in by interfering with his irrelevant
>> waffling by interrupting it with fact. You know that, right? :)
>>
>>>> They also added a two stage blower and an aftercooler. The two stage
>>>> blower added less heat to the incoming air for the same given
>>>> pressurisation hence was more efficient vis a vis combustion. That
>>>> and the aftercooler would have enabled higher compression ratios by
>>>> themselves.
>>>>
>>>>
>>> I am aware of what an intercooler does, in the case of the Merlin it
>>> was an air to liquid type with it's own cooling loop and radiator
>>> independent of the main cooling system and it was only present on
>>> engines with the 2 stage blower. The 2 stage blower was mainly not
>>> added to get more power, but to enable operation at higher altitude
>>> (30,000 ft was the target), the same as the 2 speed blower which
>>> changed speed automatically at a particular altitude. It could also
>>> be changed to high speed in an emergency by the pilot pushing the
>>> throttle though a gate. At low altitude the engine was not rated for
>>> more than 5 minutes on this setting, but when you've got an Me109 up
>>> your arse, you don't care about that.
>>
>> No, you don't :)
>>
>> Pretty sure some American radials had these "War Emergency Power"
>> settings available as well, and if I remember correctly I read (or
>> most likely saw on some doco) that the later variants of the Me109 ran
>> a water injection system to help avoid combustion problems in extreme
>> situations.
>
> Some FW190s had nitrous injection.
>
> Our Neptune has Wright 3350 engines. 52 litre 18 cylinder radials, they
> have water methanol injection that enables the use of 60" of boost when
> using 135 octane fuel giving 3370 bhp.
>
>>> On the Merlin 100 series, the 2 stage blower was redesigned and
>>> incorporated single point fuel injection into the input of the first
>>> stage of the blower. Rolls reckoned this was superior to the Daimler
>>> Benz system of direct injection, as the fuel was fully evaporated
>>> when the mixture entered the cylinder rather than as a liquid. The
>>> evaporation of the fuel through the blower also helped to cool the
>>> mixture.
>>
>> No doubt helped to lubricate it as well, which is something that
>> carries over into mechanical blowers to this day. When running a
>> "Rootes" type blower on any car engine, an in particular one that's
>> had it's clearances tightened up to produce boost from just off idle,
>> they get incredibly hot. The solution is to run them "wet" by way of
>> adding fuel into the arflow ahead of the blower. Easy enough to do on
>> a carburetted engine by just plonking the carb(s) straight on top of
>> the blower, but the downside is that blowers tend to have a
>> "corkscrew" effect on airflow and they push most of the fuel to the
>> rear of the inlet manifold on a V8 engine.
>>
>> A way around the phenomena with an injected engine is to run a couple
>> of "weter" injectors above the blower, and individual port injectors
>> underneath. I'm working on one such system right now, and hopefully it
>> will perform very well.
>
> They may exist, but I've never seen an aero engine with a rootes blower,
> centrifugal ones seem to be the preferred choice.
>
The induction pulses they create might get nasty in aircraft. Anyway,
for the record, they are *Roots* type blowers. They derive that name
from their inventors, Philander and Francis Roots, who founded the Roots
Blower Company.

https://en.wikipedia.org/wiki/Roots_Blower_Company

The Roots Blower Company has no affiliations whatsoever with the UK
based Rootes Group automobile company beyond said company's use of a
Roots blower on the Commer TS3 engine.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 17/4/2023 7:37 am, alvey wrote:
> Noddy <me@home.com> wrote in news:u1gkpa$2h4th$1@dont-email.me:
>
>
> snip irrel
>
>> A way around the phenomena with an injected engine is to run a couple
>> of "weter" injectors above the blower, and individual port injectors
>> underneath. I'm working on one such system right now,
>
> Really Fraudster? It's not like you to pass up an opportunity to big
> yourself by posting some happy snaps.

Only happy snaps that are totally irrelevant to the *claim at hand*.
>
>> and hopefully it will perform very well.
>
> I'm sure that we'll hear all about it if it doesn't. [That be irony
> Fraudster]
>

>
>
>
> alvey
>
>
>
>
>

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 16/4/2023 5:25 pm, Keithr0 wrote:
> On 15/04/2023 10:04 pm, Xeno wrote:
>> On 15/4/2023 4:15 pm, Keithr0 wrote:
>>> On 14/04/2023 5:57 am, Trevor Wilson wrote:
>>>> On 13/04/2023 9:59 pm, Keithr0 wrote:
>>>>> On 2/04/2023 5:51 am, Trevor Wilson wrote:
>>>>>> This just appeared in one of my feeds:
>>>>>>
>>>>>> ---
>>>>>> In his book Not Much Of An Engineer, Rolls Royce supercharger
>>>>>> designer Stanley Hooker states that Ford UK looked at the Merlin
>>>>>> engine drawings and said "we can't build an engine to those
>>>>>> tolerances." Hooker said loftily (his words) " I suppose the
>>>>>> tolerances are too tight for you?" " No, they are much too loose -
>>>>>> we use much tighter tolerances for car engines so all the parts
>>>>>> are truely interchangeable without any hand adjustment needed."
>>>>>>
>>>>>> Ford UK then spent a year redrawing all the Merlin engine drawings
>>>>>> to finer tolerances, and then built. 30,000 of them during the
>>>>>> rest of the war.
>>>>>>
>>>>>> "and they were very good engines too" said Hooker.
>>>>>
>>>>> Rolls relied on rough machining and squads of poorly paid workers
>>>>> with files to complete the job. That worked in the 30s if you
>>>>> weren't into mass production.
>>>>>
>>>>> Hooker's book is an excellent read on the subject if you are into
>>>>> that sort of thing. He didn't do the original design for the
>>>>> supercharger, but he took a mediocre design and transformed it. The
>>>>> original Merlins only gave 800 odd bhp, by the end of the war it
>>>>> was 2000bhp, a lot of that came from supercharger improvements.
>>>>>
>>>>> Packard also made changes, I believe that they simplified the bolt
>>>>> and screw inventory, Rolls had apparently used every size and
>>>>> thread known to man.
>>>>>
>>>>
>>>> **I was under the impression that American, high octane fuel was a
>>>> big part of that power increase. Obviously engine mods would have
>>>> been required to cope with that high octane fuel.
>>>>
>>> Higher octane fuel allowed higher boost pressures to be used but did
>>> not of itself add power.
>>
>> It enabled higher compression ratios, whether static of dynamic, hence
>> allowed for higher power output should the engine builder care to take
>> advantage of it. The higher octane fuel burns more slowly so, in order
>> to retain the same power, you need to advance the ignition timing, but
>> you do gain in slightly reduced fuel consumption. The advantage is
>> when you bump the compression ratio up to take advantage of the slower
>> burning fuel which is less prone to detonation. That is when you gain
>> *efficiency* and increase power output.
>
> That may be true in general, but the compression ratio of the Merlin was
> the same in all models - 6:1.

If you read what I wrote above, you will note the term I used,
*dynamic*. You can increase the dynamic (effective) compression ratio by
a number of means, the most obvious being boost, all the while leaving
the static compression ratio as is. Pump in pressurised air from a
blower and you will increase the dynamic CR whilst the *static CR*
remains the same. Flow more air and you can burn more fuel thereby
increasing the power output. The most obvious dynamic CR boost is that
obtained from changes to intake valve timing. Trevor was quite correct
when he mentioned engine modifications. Which reminds me, when they
started dragging more power out of the engines by various means,
including supercharging, they made quite a few modifications to the
engines in order to withstand the increased loadings on internal
components including, but not limited to, pistons, con rods & bearings.
>>>
>>> This is a reasonable view of the Merlin development in a nutshell
>>>
>>> https://en.wikipedia.org/wiki/Rolls-Royce_Merlin
>>>
>>> Most of the power increases were due to supercharger improvements
>>> leading to higher boost pressures(also better performance at
>>> altitude). It is worth noting though that every little helps and
>>> pointing the exhausts to the back gave the equivalent of a 70hp power
>>> increase.
>>>
>> They also added a two stage blower and an aftercooler. The two stage
>> blower added less heat to the incoming air for the same given
>> pressurisation hence was more efficient vis a vis combustion. That and
>> the aftercooler would have enabled higher compression ratios by
>> themselves.
>>
>>
> I am aware of what an intercooler does, in the case of the Merlin it was

I was referring to the *aftercooler*. It's a tad difficult to stick an
intercooler on a two stage centrifugal supercharger of the type used on
the Merlin but they designed one into the two stage supercharger itself
to retain compact dimensions though they called it an *interstage
cooler*. Makes more sense. The Merlin aftercooler, the one that looks
like a *radiator*, cools the air *after* it has passed through *both*
stages of the air compression process - so it is an aftercooler. Yes,
people may call it an intercooler - but they are wrong. Intercoolers are
*between* stages of superchargers and the Merlin in question has two
stages of centrifugal supercharger hence *interstage cooler*.

From an article I know you have read.

The ultimate Merlin variants used a twin-speed twin-stage
supercharger, with an intercooler and aftercooler, and were
for high-altitude bombers and high-performance fighters.

> an air to liquid type with it's own cooling loop and radiator
> independent of the main cooling system and it was only present on
> engines with the 2 stage blower. The 2 stage blower was mainly not added
> to get more power, but to enable operation at higher altitude (30,000 ft

The primary purpose of *supercharging* in *any* aircraft is to increase
the ceiling over that which can be achieved by naturally aspirated
engines and the secondary purpose is to increase power. Fighter aircraft
definitely need both. Air pressure decreases with altitude so air
compression helps maintain engine power as the aircraft climbs. A two
stage blower getting the same boost as a single stage blower but without
heating the incoming air as much *will* give an increase in power at the
*same* boost pressure and will give increased fuel economy. The two
stage blower has less overall heat input to the air for a given boost
pressure than a single stage blower - but I have mentioned that before.
The aim is to reduce *air density loss* through heating thereby
providing a *volumetric efficiency gain*.

> was the target), the same as the 2 speed blower which changed speed
> automatically at a particular altitude. It could also be changed to high

Different purpose, different aims. A single speed blower with a
compression ratio set for maximum power at high altitudes will flow much
more air than the engine can use at low altitudes. A two speed blower
provides high power for taking off at low altitudes and maximum power at
high altitudes, all with a single blower.

> speed in an emergency by the pilot pushing the throttle though a gate.
> At low altitude the engine was not rated for more than 5 minutes on this
> setting, but when you've got an Me109 up your arse, you don't care about
> that.
> On the Merlin 100 series, the 2 stage blower was redesigned and
> incorporated single point fuel injection into the input of the first
> stage of the blower. Rolls reckoned this was superior to the Daimler
> Benz system of direct injection, as the fuel was fully evaporated when
> the mixture entered the cylinder rather than as a liquid. The
> evaporation of the fuel through the blower also helped to cool the mixture.

The primary reason for injecting the fuel in the intake tract *anywhere*
is the density increase of the air which bumped up the VE. Water
injection does much the same thing - but with caveats. The latent heat
of evaporation provides a cooling effect - similar to what occurs in AC
systems. The cooled incoming air tends to reduce the risk of detonation
but the increase in air density tends to do the opposite because it
increases the dynamic (*effective*) compression ratio.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)