Bike Design Class

[JeffWills]

Michael Press wrote:
>
> 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.
>

It depends on how you define "best". In purely mechanical terms, an
inline 6 is better balanced. However, a V-6 with a 60 or 120-degree
angle between the cylinder banks can be nearly as well balanced and
might make for a more compact package.

For instance, the Lexus IS300 built from 2002 to 2005 featured a
3-liter inline-6. The 2006 Lexus IS350 has a 3.5-liter V-6.
Why the switch?
More room for forward crush space?
Better weight distribution?
Public demand for a "high-tech" V-6?

I dunno- and it's probably a combination of all of those factors and
more. I doubt if there's a difference that matters for the vast
majority of owners.

Hey- when did this turn into the
alt.lets.talk.about.motors.until.we're.blue group?

Jeff

 

[JeffWills]

JeffWills wrote:
> >
>
> It depends on how you define "best". In purely mechanical terms, an
> inline 6 is better balanced. However, a V-6 with a 60 or 120-degree
> angle between the cylinder banks can be nearly as well balanced and
> might make for a more compact package.
>

Well- Jobst's answer is better than mine. I'll defer to his superior
knowledge in this area. But he's not going to get me to give up my
recumbent!

Jeff

 

[John Forrest Tomlinson]

On Sun, 11 Dec 2005 03:07:36 -0500, "Simon Cooper"
<[email protected]> wrote:

><[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.

The salesman who sold us our Suburu claimed the center of gravity of
the engine can be a little lower.

JT

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[Dave Larrington]

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

> 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.

The "Sharknose" 156 started life with a 60 degree V6 - a development of
the "Dino" used in F2 in the late 1950's - and went to a 120 later. By
the end of the 1.5 litre formula they running V6s, V8s and flat-12s and
watching Lotus clean up...

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Never play leapfrog with a unicorn.

 

[Dave Larrington]

In article <[email protected]>, Jasper Janssen
([email protected]) wrote:

> 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.

It's still aft of the rear axle, though. The Boxster & Cayman are
properly mid-engined, though you can't actually get at the motor except
from underneath. I think they come with a sticker saying "No user-
serviceable parts inside".

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
I am now returned from both the seventeenth century and the Post Office.

 

[Dave Larrington]

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.

When I was a small Mr Larrington, I taught myself to ride a bicycle with
my arms crossed, though I cannot for the life of me remember why...

I've seen one of the carnival bikes with not only reversed steering, but
also reversed pedalling and IIRC, eccentric wheels. Squarely in the
land of odd.

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Me, I wanna be an anglepoise lamp, yeah!

 

[Jasper Janssen]

On Mon, 12 Dec 2005 12:53:44 -0000, Dave Larrington
<[email protected]> wrote:

>In article <[email protected]>, Jasper Janssen
>([email protected]) wrote:
>
>> 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.
>
>It's still aft of the rear axle, though. The Boxster & Cayman are
>properly mid-engined, though you can't actually get at the motor except
>from underneath. I think they come with a sticker saying "No user-
>serviceable parts inside".

Doesn't really matter much where it is exactly, except for weight
distribution, though. Mid-engine happens to make 50/50 weight really easy,
but it can be done with the engine anywhere -- although adding a few
blocks of lead over the front nose to balance will result in problems
compared to something that has more of the weight centrally, of course.

Jasper

 

[Bill Sornson]

John Forrest Tomlinson wrote:
> On Sun, 11 Dec 2005 03:07:36 -0500, "Simon Cooper"
> <[email protected]> wrote:
>
>> <[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.

> The salesman who sold us our Suburu claimed the center of gravity of
> the engine can be a little lower.

OK, I'll bite. What does that mean? (If you were trying to say that the
salesman claimed that, due to its configuration, the engine's COG was /in
fact/ lower, then you failed to convey that clearly.)

Bill "when in Rome..." S.

 

[[email protected]]

ahhh bs!
here are there design advances worth considering?
is there something to advance human propelled transport into the 20th
century?
do we see fractional improvement? degrees of improvement?

 

[Andrew Price]

On Mon, 12 Dec 2005 15:00:38 GMT, Jasper Janssen <[email protected]>
wrote:

>>It's still aft of the rear axle, though. The Boxster & Cayman are
>>properly mid-engined, though you can't actually get at the motor except
>>from underneath. I think they come with a sticker saying "No user-
>>serviceable parts inside".
>
>Doesn't really matter much where it is exactly, except for weight
>distribution, though.

What matters are the *consequences* of that distribution. Having a
lot of weight behind the rear axle (rather than between the axles)
tends to unbalance the car and cause oversteer. I owned a number of
rear-engined cars, and although they were all great fun to drive, they
could be dangerous if not handled properly.

It was a neat mechanical solution - engine and transmission in one
unit, hence optimum traction, yet mechanically simpler than
front-wheel-drive - but I think it's no chance that this
configuration, once so common in Europe, has been abandoned by nearly
all manufacturers.

 

[Matt O'Toole]

On Mon, 12 Dec 2005 15:00:38 GMT, Jasper Janssen <[email protected]>
wrote:

>Doesn't really matter much where it is exactly, except for weight
>distribution, though. Mid-engine happens to make 50/50 weight really easy,
>but it can be done with the engine anywhere -- although adding a few
>blocks of lead over the front nose to balance will result in problems
>compared to something that has more of the weight centrally, of course.

Actually mid-engine cars tend to have a rearward weight bias, with
both engine and transmission at the same end of the car. This is
helpful for braking (where passing maneuvers are made), but less than
optimal for general handling on real roads.

Modern engines are light enough that they don't make front-engine RWD
cars nose-heavy -- current BMWs have 50/50 or better weight
distribution.

Matt O.

 

[[email protected]]

John Forrest Tomlinson 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.

> The salesman who sold us our Suburu claimed the center of gravity of
> the engine can be a little lower.

Oh? Are you having center of gravity problems. Unless you are
considering a jacked up suspension to make your car look like a
micro-monster car, CG height of most passenger cars is defined more by
the body contours rather hand anything in the engine compartment.

If the salesman said that, you ought to give him ten lashes for
bringing up that red herring.

Jobst Brandt

 

[[email protected]]

used to be there was a feel to this-the big six ran free and easy at
70+
the four had a nasty vibration at 60 but at other rpm felt lika six
the bmw straight six is a legendary motor an apex in 6. renault had a
nice one too!
the v-8 always felt tight
the v-6 a disaster until ford germany tamed it in 1970 or so. chevy
still can't do it.
the v-12 esp the ferrari columbo desing!!
but now with balancing a five works and fits under the hood with extra
hp/torque
but the flat 4 is smooooth and has a low cg.
if everything else was equal the flat 4 would be more durable

 

[rcoder]

Here in Portland, Oregon, we have just such a museum: it's called OMSI,
short for "Oregon Museum of Science and Industry," and its exhibits
predominantly feature large-scale, interactive models of all kinds of
machines, from simple gears and hydraulics to logic circuits and blood
vessels. I suspect that many areas have similar resources. However,
since they tend to be targeted almost exclusively at young children,
the hands-on approach to engineering education tends to be discredited
amongst more "grown-up" institutions.

On the other hand, working on bicycles has certainly for me (and a
number of my friends who have recently rediscovered them) renewed my
interest in practical, concrete engineering, even if most of my efforts
seem to be devoted to substituting my pitiful supply of tools for the
array of specialized equipment availble in any modern bike workshop.

-Lennon

 

[[email protected]]

THE VW IS NOT A LINCOLN SIX
the vw is a urban car for germany's low speed urban population-transit
system based in 1750
and if driven at 40 mph and no racing art
it lives
and you know this JB!
where's the beef?

 

[[email protected]]

ruminating on future designers as dilllitante arteests
reverbs like LBS mechanics speculating on bike performance over time.

 

[Michael Press]

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

> Michael Press wrote:
> >
> > 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.
> >
>
> It depends on how you define "best". In purely mechanical terms, an
> inline 6 is better balanced. However, a V-6 with a 60 or 120-degree
> angle between the cylinder banks can be nearly as well balanced and
> might make for a more compact package.
>
> For instance, the Lexus IS300 built from 2002 to 2005 featured a
> 3-liter inline-6. The 2006 Lexus IS350 has a 3.5-liter V-6.
> Why the switch?
> More room for forward crush space?
> Better weight distribution?
> Public demand for a "high-tech" V-6?
>
> I dunno- and it's probably a combination of all of those factors and
> more. I doubt if there's a difference that matters for the vast
> majority of owners.
>
> Hey- when did this turn into the
> alt.lets.talk.about.motors.until.we're.blue group?

I took an opportunity to ask an expert a question that I
would only as an expert I trust. If you want to complain,
take it to the elastomer in a frame discussion. However I
find it a delicate question whether to enter a
(sub-)thread that has outlived its usefulness.

P.S. You and he appear to disagree about the 120 degree
configuration.

--
Michael Press

 

[Jasper Janssen]

On 12 Dec 2005 13:57:00 -0800, "rcoder" <[email protected]> wrote:

>On the other hand, working on bicycles has certainly for me (and a
>number of my friends who have recently rediscovered them) renewed my
>interest in practical, concrete engineering, even if most of my efforts
>seem to be devoted to substituting my pitiful supply of tools for the
>array of specialized equipment availble in any modern bike workshop.

For me, lately, it's been discovering structural engineering through
DIYing some walls up and down (non-load-bearing), and other serious DIY
tasks.

Jasper