Bike Design Class

[[email protected]]

[email protected] wrote:
> There will always be "recumbents" in the bicycle industry and
> similarly, rear engined cars in the auto industry. They do not make
> up the mainstream or any part of it. There is no excuse for air
> cooling in cars without some special purpose in mind.

Simplicity? I don't even like air cooling in motorcycles, and I'm
inclined to agree with you, but I'm not sure that it was a flaw even
though it does make it more difficult to control head temperature.
OTOH, you never got stranded because of a problem in the cooling
system. The VW and 2CV were both air cooled, so it must have met some
purpose for utterly basic transportation that was not completely lost
even into the '70s.

Porsche got 1100hp out of the 917/30 and won a lot races with it so air
cooling doesn't seem to have been too great a drawback. Is that a
special purpose, indicating that air cooled flat engines are
particularly well suited to racing and high output?

> That's what PR will have you believe. Porsche never designed any part
> of the VW. In fact you can't find a single drawing, that he
> made. That work was done by engineers after he brought the car in from
> Czechoslovakia where he had seen it and sold the concept to the German
> government. The main appeal was that everything about it was
> different and that Porsche was a good salesman of the idea. The same
> was true for the American market.

I guess I thought the main appeal was the idea was that the car could
be made and maintained cheaply. I don't know whether Porsche designed
the car or not. I have read books that say he did. I guess you have
proof that it is a lie. The lack of drawings would not seem to be that,
especially given the intervention of a war between the car's design and
its production. Also, I would never expect that the designer of a car
would personally design every component of it.

> That was one of their great PR claims, that one could remove the
> engine in less than 15 minutes. To that I ask, how often did you need
> to remove the engine from your... Ford, Chevrolet, Dodge, Nash...

Well, in the case I'm talking about the car was old and needed a new
clutch. With most of those cars the labor cost to remove the engine
would have been greater than the value of the car. But to answer your
question about those other cars: every time you needed to replace the
clutch.

> In
> contrast, VW engines were out on the repair bench all the time. Let's
> not get into the details of transmissions, torsion bar suspension and
> all the other odd features.

I didn't.

 

[[email protected]]

Simon Cooper <[email protected]> writes:

>>> engine, so that would seem to invalidate your statement that NO
>>> ONE makes use of ANY of the design concepts. There is at least one
>>> maker still using at least one of the design concepts. Of course,
>>> there never were that many air-cooled flat fours, anyway. I do
>>> have a water-cooled flat four in my Subaru, though.

>> There will always be "recumbents" in the bicycle industry and
>> similarly, rear engined cars in the auto industry. They do not
>> make up the mainstream or any part of it. There is no excuse for
>> air cooling in cars without some special purpose in mind.

> If you'd had as much trouble with the water cooling system of a car
> as I've had with my Trans Am, you might think more highly of air
> cooling...

That's what was a major selling point of the VW. At the start of WWII
cars with boiling engines on hills were common so the military said
"Fix that". That is when the carbon water pump seal arrived making
all the boiling engined go the way of history. The graphite rope
seal, although it looked good, only leaked when the engine was running
and hot, and at that moment all water that came out evaporated so no
one seemed to get any wiser about this massive leak. The carbon seal
made those experiences into a thing of the past except that car buyers
were unaware that it was no longer a problem and bought VW's with
the justification that they didn't boil on hills.

> The flat four in my Subaru seems fine. I'll bet a poll of this
> group would reveal a far higher than is natural number of Subaru
> owners...

Spoken as a true believer. What is it about this cylinder arrangement
that you believe is superior to in-line and v-engines?

Jobst Brandt

 

[Bill Patterson]

> I don't know what the rules are now. I'm retired and loving it. But I
> only asked that the bike be different and hopefully handled well.
> I did require a report that included the geometry including the exact
position of the cg of the bike/rider and a measured radius of gyration.

We needed these to determine the handling quality derivatives.


--
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See bikes and the first human powered helicopter at:

http://www.calpoly.edu/~wpatters/

Reply to [email protected]
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[[email protected]]

someone writes:

>> There will always be "recumbents" in the bicycle industry and
>> similarly, rear engined cars in the auto industry. They do not
>> make up the mainstream or any part of it. There is no excuse for
>> air cooling in cars without some special purpose in mind.

> Simplicity? I don't even like air cooling in motorcycles, and I'm
> inclined to agree with you, but I'm not sure that it was a flaw even
> though it does make it more difficult to control head temperature.
> OTOH, you never got stranded because of a problem in the cooling
> system. The VW and 2CV were both air cooled, so it must have met
> some purpose for utterly basic transportation that was not
> completely lost even into the '70s.

Had you worked in the auto industry with air cooled cars, you would
have seen how complex engines get with air cooling. Separate
cylinders and heads that have unmanageable thermal expansion. Airflow
control that requires vanes and dams between engine parts and
basically an oil cooled engine, which to a large degree "air cooled"
engines are. Besides that, running as hot as they do, their fuel
efficiency is poorer. The need for aluminum fins make engine parts
composite castings with high wear rates.

> Porsche got 1100hp out of the 917/30 and won a lot races with it so
> air cooling doesn't seem to have been too great a drawback. Is that
> a special purpose, indicating that air cooled flat engines are
> particularly well suited to racing and high output?

So did Ferrari with their 120 degree V-6 GP engines but to make up
for this, the worst possible engine balance angle, all screws on the
car had to be safety wired or they would vibrate out. Forcing the
design with extra costs does not mean it is a good solution, only that
with sufficient effort, it can be made to work. VW also had the best
service network of any post WWII car and that is what made them
famous.

>> That's what PR will have you believe. Porsche never designed any
>> part of the VW. In fact you can't find a single drawing, that he
>> made. That work was done by engineers after he brought the car in
>> from Czechoslovakia where he had seen it and sold the concept to
>> the German government. The main appeal was that everything about
>> it was different and that Porsche was a good salesman of the idea.
>> The same was true for the American market.

> I guess I thought the main appeal was the idea was that the car
> could be made and maintained cheaply. I don't know whether Porsche
> designed the car or not. I have read books that say he did. I
> guess you have proof that it is a lie. The lack of drawings would
> not seem to be that, especially given the intervention of a war
> between the car's design and its production. Also, I would never
> expect that the designer of a car would personally design every
> component of it.

It was a relatively cheap car but it required much upkeep. As to
Mr. Porsche, there are the faithful who want to attribute great things
to the man. He was well connected with the government and Heinz
Nordhoff built VW to a great reconstruction employer in the post war
years, something the government was glad to see.

>> That was one of their great PR claims, that one could remove the
>> engine in less than 15 minutes. To that I ask, how often did you
>> need to remove the engine from your... Ford, Chevrolet, Dodge,
>> Nash...

> Well, in the case I'm talking about the car was old and needed a new
> clutch. With most of those cars the labor cost to remove the engine
> would have been greater than the value of the car. But to answer
> your question about those other cars: every time you needed to
> replace the clutch.

I don't recall replacing a clutch except on our Model-A Ford.

>> In contrast, VW engines were out on the repair bench all the time.
>> Let's not get into the details of transmissions, torsion bar
>> suspension and all the other odd features.

> I didn't.

Jobst Brandt

 

[Jasper Janssen]

On 09 Dec 2005 03:05:26 GMT, [email protected] wrote:

> I can't imagine
>them designing a piece of machinery optimized for manufacture,
>assembly and possibly repair.

Repair is irrelevant to the bottom line, witness cars like the New Beetle
where you have to remove the battery to replace one of the front
lightbulbs and remove the engine to replace the sparkplugs (this is why
platinum spark plugs were invented).

Assembly is usually a plug-and-play event with various subassemblies
coming together and a robot plugging some bolts or welds in.

And the manufacture? Well, I have a friend who graduated from Delft
Technical University who specialises in manufacturing processes, like
getting TL lights through machines at rates of 1 or 2 or even more a
second without breaking them -- that involves making sure you don't speed
them up too quickly and don't slow them down too quickly either, which at
that speed makes the simplest of operations tricky.

Jasper

 

[Jasper Janssen]

On Fri, 09 Dec 2005 08:15:47 -0800, Ben Pfaff <[email protected]> wrote:

>It's getting a little off-topic for rbt, but I once visited a
>wonderful museum in Delft, The Netherlands. It was full of
>motors and engines and other mechanical equipment that had been
>opened up so you could see everything inside. For many of the
>exhibits, you could hand-crank them and watch how everything
>worked together. A lot of them were physically enormous so it
>was easy to see the interactions. We need more museums like
>this.

There's nothing like a crankshaft from a 7500 hp ship's diesel stood on
end to show you what crankshafts look like in detail.

The 'A [...] is Born' series on Discovery are also pretty good. A British
Country Veterinarian named Mark Evans who's a bit of a vehicle nutter goes
out and builds/rebuilds all sort of vehicles. Let's see, there was a
helicopter, a light 2 seater airplane from kits, an E-type rebuild, an AC
Cobra replica kit car, 3 Motorcycles in one series (a WWII Harley used in
Evita restore&customise, a British Triumph full restoration, and a VW
Beetle based trike), and a Range Rover/Landrover hybrid pickup truck.
Possibly one or two I forgot.

They always show the innards of the engine/clutch/transmission/
valves/diffs etc., complete with an explanation most mechanically minded
people would be able to follow.

Also, howstuffworks.com can usually give you an idea of the theory, but
they're not so good at showing you what the real thing looks like.


Jasper

 

[Jasper Janssen]

On 09 Dec 2005 21:04:26 GMT, [email protected] wrote:

>Location of the engine is not the problem although it presents other
>problems that most car designs recognize. Front suspension, steering
>gear, engine and controls all get along well in a front engine car.
>Baggage and spare wheel storage do fine alone in the rear. The front
>end mechanisms interfere with luggage space and make that a minimal
>space with rear engines.
>
>There will always be "recumbents" in the bicycle industry and
>similarly, rear engined cars in the auto industry. They do not make
>up the mainstream or any part of it. There is no excuse for air
>cooling in cars without some special purpose in mind.

Neither 911s nor Ferraris are truly rear-engined, though. They're all
mid-engined, these days. The 911 shifted the engine slowly forward over
time. Ideal goal is a 50/50 front/rear weight distribution, and most
supercars get there these days. And rear seat passengers and luggage space
are for wimps.

Torsion bar suspension was used by others than VW, incidentally. Older
Landies have it too, and presumably others.

Jasper

 

[Jasper Janssen]

On Fri, 9 Dec 2005 17:04:41 -0500, "Simon Cooper" <[email protected]>
wrote:

>The flat four in my Subaru seems fine. I'll bet a poll of this group would
>reveal a far higher than is natural number of Subaru owners...

Flat four seems like a strange design choice compared to inline four or
even V4, though. Flat-4 is (obviously) flatter, but it's got two heads
instead of 1 on inline, which adds a lot of complexity (especially if
you've got single, let alone double, overhead camshafts, which consumers
nowadays expect), and one thing engine bays tend to have lots of is height
and what they tend to have much less of are the other dimensions (mainly,
of course, because engines aren't usually shaped like that). I suppose you
don't have to put it transverse in order to have something wider than it's
long.

Jasper

 

[Jasper Janssen]

On Fri, 09 Dec 2005 03:45:42 GMT, Bill Patterson
<[email protected]> wrote:

>A couple of years ago we had one build a rear steer bike that could be
>ridden. It's on that web site somewhere.
>
>I suppose, it's the same process as riding a track bike backward.

There a (possibly UL) story about a man who would dare all comers to ride
his bike 100 yards for $100 or so, which he showed was entirely possible
by doing it, but nobody succeeded. Turned out there was a gear mech
(presumably something like 4 bevel gears, ie the inside of a diff) inside
the headtube that reversed the steering direction. Just fine if you're
used to it... but not gonna happen without a lot of practice otherwise,
even if you know the secret.

Jasper

 

[Michael Press]

In article
<[email protected]>,
Bill Patterson <[email protected]> wrote:

> > I don't know what the rules are now. I'm retired and loving it. But I
> > only asked that the bike be different and hopefully handled well.
> > I did require a report that included the geometry including the exact
> position of the cg of the bike/rider and a measured radius of gyration.
>
> We needed these to determine the handling quality derivatives.

Sorry, I have trouble navigating the links. Is there a
technical paper on bicycle dynamics, that covers steering
angle, fork offset, and dynamics of steering and lean?

--
Michael Press

 

[Bill Patterson]

Michael Press wrote:
> In article
> <[email protected]>,
> Bill Patterson <[email protected]> wrote:
>
>
>>>I don't know what the rules are now. I'm retired and loving it. But I
>>>only asked that the bike be different and hopefully handled well.
>>>I did require a report that included the geometry including the exact
>>
>>position of the cg of the bike/rider and a measured radius of gyration.
>>
>>We needed these to determine the handling quality derivatives.
>
>
> Sorry, I have trouble navigating the links. Is there a
> technical paper on bicycle dynamics, that covers steering
> angle, fork offset, and dynamics of steering and lean?
>
http://www.wisil.recumbents.com/wisil/trail.asp
http://www.wisil.recumbents.com/wisil/trail.asp#What's%20trail,%20and%20why%20do%20I%20need%20it

This web site uses my equations.

My text is ok if you are willing to accept that stability isn't the end
all and be all of bike dynamics.

It is called the 'Lords of the chainring'. With Hobbits and partial
differentials included.

ordering info here'"

http://www.calpoly.edu/~wpatters/lords.html

--
See bikes at: http://home.earthlink.net/~wm.patterson/index.html

See bikes and the first human powered helicopter at:

http://www.calpoly.edu/~wpatters/

Reply to [email protected]
[email protected]
[email protected]

 

[[email protected]]

Jasper Janssen writes:

>> A couple of years ago we had one build a rear steer bike that could
>> be ridden. It's on that web site somewhere.

>> I suppose, it's the same process as riding a track bike backward.

> There a (possibly UL) story about a man who would dare all comers to
> ride his bike 100 yards for $100 or so, which he showed was entirely
> possible by doing it, but nobody succeeded. Turned out there was a
> gear mech (presumably something like 4 bevel gears, ie the inside of
> a diff) inside the headtube that reversed the steering direction.
> Just fine if you're used to it... but not gonna happen without a lot
> of practice otherwise, even if you know the secret.

That's an old trick. If you have a wise guy who boasts about how well
he can ride, get him to try riding (his own) bicycle with arms
crossed over to the opposite side. This reverses steering and almost
universally causes the rider to crash.

I've seen it done a few times.

Jobst Brandt

 

[[email protected]]

Jasper Janssen wrote:

> There a (possibly UL) story about a man who would dare all comers to ride
> his bike 100 yards for $100 or so, which he showed was entirely possible
> by doing it, but nobody succeeded. Turned out there was a gear mech
> (presumably something like 4 bevel gears, ie the inside of a diff) inside
> the headtube that reversed the steering direction. Just fine if you're
> used to it... but not gonna happen without a lot of practice otherwise,
> even if you know the secret.

I've heard of this, but have not seen it firsthand, as a carnival
sideshow - you know, ride the bike and win the big stuffed
animal. In the version I heard, the only person who could
ride it was a girl who figured out to cross her arms, right
hand on left bar, etc.

It seems like this bike shouldn't be any harder to ride
no-hands than a normal bike, but I guess the problem
would be getting up to speed.

 

[Ryan Cousineau]

In article <[email protected]>,
[email protected] wrote:

> Jasper Janssen writes:
>
> >> A couple of years ago we had one build a rear steer bike that could
> >> be ridden. It's on that web site somewhere.
>
> >> I suppose, it's the same process as riding a track bike backward.
>
> > There a (possibly UL) story about a man who would dare all comers to
> > ride his bike 100 yards for $100 or so, which he showed was entirely
> > possible by doing it, but nobody succeeded. Turned out there was a
> > gear mech (presumably something like 4 bevel gears, ie the inside of
> > a diff) inside the headtube that reversed the steering direction.
> > Just fine if you're used to it... but not gonna happen without a lot
> > of practice otherwise, even if you know the secret.
>
> That's an old trick. If you have a wise guy who boasts about how well
> he can ride, get him to try riding (his own) bicycle with arms
> crossed over to the opposite side. This reverses steering and almost
> universally causes the rider to crash.
>
> I've seen it done a few times.
>
> Jobst Brandt

The Pacific National Exhibition, Vancouver's annual fair, had one of
these reverse-steering bikes as a midway event two years ago (I didn't
see it this year, but I wasn't looking for it). The required riding
distance was about 20 feet, and while I saw one guy manfully ride the
thing hard into the ground at about the 15-foot mark, that was as close
as anyone came while I was watching. I think the barker might have
demonstrated the thing, though.

The reversal was, if I remember correctly, done by having what amounted
to two head tubes in tandem, the front one holding the fork and the rear
one holding the stem and handlebars. Presumably they were linked with a
set of simple gears. Pretty neat for a carnival game.

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

 

[[email protected]]

Ryan Cousineau writes:

>>>> A couple of years ago we had one build a rear steer bike that
>>>> could be ridden. It's on that web site somewhere.

>>>> I suppose, it's the same process as riding a track bike backward.

>>> There a (possibly UL) story about a man who would dare all comers
>>> to ride his bike 100 yards for $100 or so, which he showed was
>>> entirely possible by doing it, but nobody succeeded. Turned out
>>> there was a gear mechanism (presumably something like 4 bevel
>>> gears, ie the inside of a diff) inside the headtube that reversed
>>> the steering direction. Just fine if you're used to it... but not
>>> gonna happen without a lot of practice otherwise, even if you know
>>> the secret.

>> That's an old trick. If you have a wise guy who boasts about how
>> well he can ride, get him to try riding (his own) bicycle with arms
>> crossed over to the opposite side. This reverses steering and
>> almost universally causes the rider to crash.

>> I've seen it done a few times.

> The Pacific National Exhibition, Vancouver's annual fair, had one of
> these reverse-steering bikes as a midway event two years ago (I
> didn't see it this year, but I wasn't looking for it). The required
> riding distance was about 20 feet, and while I saw one guy manfully
> ride the thing hard into the ground at about the 15-foot mark, that
> was as close as anyone came while I was watching. I think the
> barker might have demonstrated the thing, though.

> The reversal was, if I remember correctly, done by having what
> amounted to two head tubes in tandem, the front one holding the fork
> and the rear one holding the stem and handlebars. Presumably they
> were linked with a set of simple gears. Pretty neat for a carnival
> game.

As someone pointed out, the next time you see this deal, take it, and
ride cross-handed after assuring yourself that the guy wont wheedle
out because you "cheated".

Jobst Brandt

 

[Ryan Cousineau]

In article <[email protected]>,
[email protected] wrote:

> Ryan Cousineau writes:
>

> >>> There a (possibly UL) story about a man who would dare all comers
> >>> to ride his bike 100 yards for $100 or so, which he showed was
> >>> entirely possible by doing it, but nobody succeeded. Turned out
> >>> there was a gear mechanism (presumably something like 4 bevel
> >>> gears, ie the inside of a diff) inside the headtube that reversed
> >>> the steering direction. Just fine if you're used to it... but not
> >>> gonna happen without a lot of practice otherwise, even if you know
> >>> the secret.
>
> >> That's an old trick. If you have a wise guy who boasts about how
> >> well he can ride, get him to try riding (his own) bicycle with arms
> >> crossed over to the opposite side. This reverses steering and
> >> almost universally causes the rider to crash.

> > The Pacific National Exhibition, Vancouver's annual fair, had one of
> > these reverse-steering bikes as a midway event two years ago (I
> > didn't see it this year, but I wasn't looking for it). The required
> > riding distance was about 20 feet, and while I saw one guy manfully
> > ride the thing hard into the ground at about the 15-foot mark, that
> > was as close as anyone came while I was watching. I think the
> > barker might have demonstrated the thing, though.
>
> As someone pointed out, the next time you see this deal, take it, and
> ride cross-handed after assuring yourself that the guy wont wheedle
> out because you "cheated".
>
> Jobst Brandt

I can't wait 'til next August .

--
Ryan Cousineau [email protected] http://www.wiredcola.com/
"I don't want kids who are thinking about going into mathematics
to think that they have to take drugs to succeed." -Paul Erdos

 

[Simon Cooper]

<[email protected]> wrote in message
news:[email protected]...
> Simon Cooper <[email protected]> writes:
> > > The flat four in my Subaru seems fine. I'll bet a poll of this
> > group would reveal a far higher than is natural number of Subaru
> > owners...
>
> Spoken as a true believer. What is it about this cylinder arrangement
> that you believe is superior to in-line and v-engines?

Not sure that I do think of the arrangement as superior. But it's rally
success suggests to me that it doesn't have any serious drawbacks. Some
part of me wants to believe the moving parts will balance out better than in
a system with the pistons not opposed, but some sensible thinking dismisses
that quite quickly. Might be valid if the firing times of the cylinders
were synchronised...

 

[[email protected]]

Simon Cooper writes:

>>> The flat four in my Subaru seems fine. I'll bet a poll of this
>>> group would reveal a far higher than is natural number of Subaru
>>> owners...

>> Spoken as a true believer. What is it about this cylinder
>> arrangement that you believe is superior to in-line and v-engines?

> Not sure that I do think of the arrangement as superior. But it's
> rally success suggests to me that it doesn't have any serious
> drawbacks. Some part of me wants to believe the moving parts will
> balance out better than in a system with the pistons not opposed,
> but some sensible thinking dismisses that quite quickly. Might be
> valid if the firing times of the cylinders were synchronised...

As I mentioned, if the team is well run, they can win with almost any
design of equipment in the limits of reality. Saab won many rallies
with their two-stroke cars and Ferrari won GP's with their vibro
special engines. Il Commendatore made sure they won being a manager
who got right down to the mechanics level at all stages of his
endeavor. Jean Todt does the same.

Just citing race wins does not prove that, for instance, a flat four
is superior to other arrangements. I spent a lot of time engineering
around flat opposed engines. They, by the way, do not have the
excellent balance attributed to the boxer engine. They are no better
than an in-line four. The offset of the pistons is enough to make
them shake more than an in-line four.

A V-engine, regardless of cylinder angle from 15 to 180 degrees, has
two pistons attached to a common crank pin while the boxer has them
attached to staggered (180 degree opposed), side-by-side crank pins
and are always opposed flat engines. Piech's 917 engine was a flat
180 degree V-engine with 12 cylinders.

http://en.wikipedia.org/wiki/Flat-12

Jobst Brandt

 

[Michael Press]

In article <[email protected]>,
[email protected] wrote:

> Simon Cooper writes:
>
> >>> The flat four in my Subaru seems fine. I'll bet a poll of this
> >>> group would reveal a far higher than is natural number of Subaru
> >>> owners...
>
> >> Spoken as a true believer. What is it about this cylinder
> >> arrangement that you believe is superior to in-line and v-engines?
>
> > Not sure that I do think of the arrangement as superior. But it's
> > rally success suggests to me that it doesn't have any serious
> > drawbacks. Some part of me wants to believe the moving parts will
> > balance out better than in a system with the pistons not opposed,
> > but some sensible thinking dismisses that quite quickly. Might be
> > valid if the firing times of the cylinders were synchronised...
>
> As I mentioned, if the team is well run, they can win with almost any
> design of equipment in the limits of reality. Saab won many rallies
> with their two-stroke cars and Ferrari won GP's with their vibro
> special engines. Il Commendatore made sure they won being a manager
> who got right down to the mechanics level at all stages of his
> endeavor. Jean Todt does the same.
>
> Just citing race wins does not prove that, for instance, a flat four
> is superior to other arrangements. I spent a lot of time engineering
> around flat opposed engines. They, by the way, do not have the
> excellent balance attributed to the boxer engine. They are no better
> than an in-line four. The offset of the pistons is enough to make
> them shake more than an in-line four.
>
> A V-engine, regardless of cylinder angle from 15 to 180 degrees, has
> two pistons attached to a common crank pin while the boxer has them
> attached to staggered (180 degree opposed), side-by-side crank pins
> and are always opposed flat engines. Piech's 917 engine was a flat
> 180 degree V-engine with 12 cylinders.
>
> http://en.wikipedia.org/wiki/Flat-12

What is better straight six or V six? I heard a rumor that
the V angle for a V six is no help, and that the V six is
made only to fit small spaces. BMW six cylinder engines
are in line.

--
Michael Press

 

[[email protected]]

Michael Press writes:

>>>>> The flat four in my Subaru seems fine. I'll bet a poll of this
>>>>> group would reveal a far higher than is natural number of Subaru
>>>>> owners...

>>>> Spoken as a true believer. What is it about this cylinder
>>>> arrangement that you believe is superior to in-line and
>>>> v-engines?

>>> Not sure that I do think of the arrangement as superior. But it's
>>> rally success suggests to me that it doesn't have any serious
>>> drawbacks. Some part of me wants to believe the moving parts will
>>> balance out better than in a system with the pistons not opposed,
>>> but some sensible thinking dismisses that quite quickly. Might be
>>> valid if the firing times of the cylinders were synchronised...

>> As I mentioned, if the team is well run, they can win with almost
>> any design of equipment in the limits of reality. Saab won many
>> rallies with their two-stroke cars and Ferrari won GP's with their
>> vibro special engines. Il Commendatore made sure they won being a
>> manager who got right down to the mechanics level at all stages of
>> his endeavor. Jean Todt does the same.

>> Just citing race wins does not prove that, for instance, a flat
>> four is superior to other arrangements. I spent a lot of time
>> engineering around flat opposed engines. They, by the way, do not
>> have the excellent balance attributed to the boxer engine. They
>> are no better than an in-line four. The offset of the pistons is
>> enough to make them shake more than an in-line four.

>> A V-engine, regardless of cylinder angle from 15 to 180 degrees,
>> has two pistons attached to a common crank pin while the boxer has
>> them attached to staggered (180 degree opposed), side-by-side crank
>> pins and are always opposed flat engines. Piech's 917 engine was a
>> flat 180 degree V-engine with 12 cylinders.

http://en.wikipedia.org/wiki/Flat-12

> What is better straight six or V six? I heard a rumor that the V
> angle for a V six is no help, and that the V six is made only to fit
> small spaces. BMW six cylinder engines are in line.

For best dynamic balance, a 60 degree V-6 is required but that is an
inconvenient cylinder angle for intake ports, so the TAG Porsche
engine was 68 degrees as I recall. Because the imbalance function is
a cosine effect, small angles from the ideal are permissible. 120
degrees is the worst and that is what Ferrari had in the 1960's. That
shows how some engineers get fixated on firing order, which is perfect
with that angle, but then firing order is immaterial as we see with
Vincent, Harley, Ducati, Moto Guzzi and other engines where cylinders
fire in asymmetric sequence with no ill effects.

Whether you chose a V or in-line arrangement depends on space in the
car. The narrow angle V engines with one cylinder head covering both
banks is an ultimate in volumetric design. I think Piech was also the
driving force behind that concept. With balancing shafts an in-line
engine can be made to run as smooth as an ideal V. Of course, all
these require water cooling if economy and efficiency are desired.
Racing cars can do many things that would not play well on the
consumer market.

Jobst Brandt