From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <DK6Rd.7258$m31.90327@typhoon.sonic.net>
Date: Thu, 17 Feb 2005 20:01:39 GMT

David L. Johnson writes:

>>> It wasn't always poor design that created these resonances.  As I
>>> understand it, a 4-cylinder in-line engine will produce on its own
>>> a lot of vibrations, which are of course propagated throughout the
>>> car.  What has changed has not been superior engineering as much
>>> as bigger engines that produce proportionately less vibration in
>>> the frequency range that causes the noise.

>>> One car I heard about had an acoustic damper; it fed the noise
>>> back into the car out of phase from what the engine was
>>> generating.  Poor solution in my opinion, but apparently it
>>> worked.

>> Porsche engines and some Hondas have a harmonic balancer shaft to
>> minimise this.

> I thought that opposed-4 engines like Porsche, old VWs and Subaru,
> were not susceptible to this vibration.  I also thought that the v-6
> and v-8 did not have the problem because of the non-aligned
> cylinders, so that a straight-6 or -8 would be prone to the same
> problem (less so, because of the greater balance of piston phases
> than in a 4, though).

The opposed cylinder engine to which you refer are known as boxers
while Porsche engines like the 917 are 180 degree V-engines, the
difference being that there are a pair of connecting rods on each
throw in the V-engine and only one on the boxer.  However, the boxer
is a false prophet and works only if you see it in 2D, axially.  It
is a big miscalculation and always was.

The offset of its cylinders causes an imbalance that is like that of
an in-line four.  Besides that, the old VW beetle had the engine
rigidly mounted to the chassis so that the vibrations were directly
connected to the dashboard.  The BMW opposed cylinder motorcycle
engine has a substantial imbalance which is noticeable.

The boxer engine is a phony and always was.  It was blessed by
F. Porsche who was one of the best promoted inventors without
portfolio in the business.  Without the industrious and meticulous
German mechanic, the beast would have been a looser.  It was the
support system that made it survive, not the design.  You'll notice
that today no one is building with a boxer, rear engine, air cooling,
torsion bar springs, swing axles or any other part of the concept.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <KzbRd.7297$m31.90540@typhoon.sonic.net>
Date: Fri, 18 Feb 2005 01:31:22 GMT

Robert Box? writes:

> I'll agree with Jobst that the Beetle was a maintenance hog. Valve
> adjustments every 3k and even then exhaust valves died rapidly after
> leaded fuel went away. Spark plugs seemed to love freezing up in the
> heads, pulled cylinder studs, etc.Fun car for a tinkerer , but high
> maintenance.

> Question Jobst, when did they build Beetles with the engines
> rigidly mounted? All the ones I ever worked on had the transaxle to
> frame rubber mounts.

As long as the original swing-axle was used it was the only way to
make the car stable because the engine is bolted to the transmission
and the rear wheels are located by the transmission/differential
housing.  Therefore, that unit (with the engine) had to be rigidly
mounted to the chassis.  Although there was rubber between the
transmission housing and chassis, that rubber was mostly confined and
because rubber is incompressible, acted like concrete.  That is why VW
switched to the double jointed drive axles and semi trailing link
suspension, in order to isolate the engine that could not be
elastically supported before that.

In retrospect, I am amazed that no experienced had spoke up and said,
let's rethink the whole concept.  Only Carl Hahn did that when he
replaced Heinz Nordhoff as CEO of VW and got out of the 111 VW
realizing that the company was going under with the antiquated noisy,
unreliable and dangerous handling beetle.

http://www.modelcarworld.de/Content/Nachrichten100/Nachrichten228.html

You'll notice that the diehards kept the air cooled engine alive in
the 411 and the bus, but even that ultimately switch to water cooling.
The whole thing was a religion and is still alive at Porsche with it's
faithful.  What I learned from this is that more important than the
design is the commitment and enthusiasm of the support team.  Ferrari
showed that with his cars as did Porsche.  The Ferrari 120 degree V-6
was the worst possible dynamic balance one could pick, yet with nearly
every screw and bolt safety wired against vibration, these cars won
GP's.  Likewise, the Porsche 804 won a GP before Mr. Porsche pulled
the financial plug, the F1 business having become too expensive for a
small car company.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <YxdRd.7329$m31.90821@typhoon.sonic.net>
Date: Fri, 18 Feb 2005 03:46:00 GMT

David L. Johnson writes:

>>> Question Jobst, when did they build Beetles with the engines
>>> rigidly mounted? All the ones I ever worked on had the transaxle
>>> to frame rubber mounts.

>> As long as the original swing-axle was used it was the only way to
>> make the car stable because the engine is bolted to the
>> transmission and the rear wheels are located by the
>> transmission/differential housing.  Therefore, that unit (with the
>> engine) had to be rigidly mounted to the chassis.  Although there
>> was rubber between the transmission housing and chassis, that
>> rubber was mostly confined and because rubber is incompressible,
>> acted like concrete.  That is why VW switched to the double jointed
>> drive axles and semi trailing link suspension, in order to isolate
>> the engine that could not be elastically supported before that.

> My '62 bug had swing axles, but they made the change to a
> fully-independent rear suspension in the late '60s.  If I had to
> guess, I'd say '67 was the first double-jointed axle.  That also
> corresponded to the introduction of a larger engine and uglier
> bumpers.

> There was another reason for this change; maybe Jobst knows how much
> of the impetus came from which side.  But this was also the time of
> Nader's "Unsafe at any speed", which claimed that the Corvair's rear
> suspension, essentially the same as the VW, was the cause of a rash
> of one-car accidents.  Corvair changed to a double U-joint arm, but
> the car still went under.  VW may not have had the bad reputation
> that Corvair had, but the swing-arm rear suspension had the same
> fatal flaw.

The best part of that is that the Germans were fully aware of the
oversteer (as it is called in the industry) of this car and had
already installed an anti-roll bar and equalizer spring (a transverse
leaf) in the rear, something Corvair had also done but never installed
for cost reasons.  That's where Nader came in.  VW was a little more
safe because they could show that the car had no changes to its
handling other than adding the anti-roll bar (a distinct improvement)
in the years the car was under Nordhoff, who opposed the device.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <L4eRd.7333$m31.90760@typhoon.sonic.net>
Date: Fri, 18 Feb 2005 04:23:07 GMT

Ted Bennett writes:

>> Porsche engines and some Hondas have a harmonic balancer shaft to
>> minimise this[vibration].  The vibration is caused because the
>> pistons move faster at the top of the stroke than at the bottom.

> Eh?  Please explain further; I don't see how piston speed can be
> different at the top and bottom, where the piston slows, stops and
> accelerates again as it changes direction.

> Am I missing something?  Maybe I could parlay this into the next
> PowerCrank...

Piston speed is at its maximum when the crank throw and connecting rod
are at right angles.  That is, when the straight line from piston CL
to the crank main bearing and the rod and crank throw make a right
triangle.  That position is above the diameter of the crank throw
rotation so at constant crank velocity, more time is spent on the
lower portion of the stroke than the upper.

This is the effect that gives steam engines the syncopated rhythm made
famous by "The Little Engine that Could" as it said 'I-think-I-
can-I-think-I-can-...' as it puffed up the hill.

Interestingly, three cylinder steam engines have an unsatisfying
rhythm with three short and three long strokes... 1-2-3--4--5--6-
1-2-3--4--5--6...  This was known as the Southern Pacific Type around
here and these locomotives were numbered the 5000 series.

http://www.steamlocomotive.com/losangeles/sp5021.jpg
http://www.steamlocomotive.com/3cylinder/#5021

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <HQfRd.7346$m31.90851@typhoon.sonic.net>
Date: Fri, 18 Feb 2005 06:22:31 GMT

Carl Fogel writes:

>>>> Porsche engines and some Hondas have a harmonic balancer shaft to
>>>> minimise this[vibration].  The vibration is caused because the
>>>> pistons move faster at the top of the stroke than at the bottom.

>>> Eh?  Please explain further; I don't see how piston speed can be
>>> different at the top and bottom, where the piston slows, stops and
>>> accelerates again as it changes direction.

>>> Am I missing something?  Maybe I could parlay this into the next
>>> PowerCrank...

>> Piston speed is at its maximum when the crank throw and connecting
>> rod are at right angles.  That is, when the straight line from
>> piston CL to the crank main bearing and the rod and crank throw
>> make a right triangle.  That position is above the diameter of the
>> crank throw rotation so at constant crank velocity, more time is
>> spent on the lower portion of the stroke than the upper.

>> This is the effect that gives steam engines the syncopated rhythm
>> made famous by "The Little Engine that Could" as it said
>> 'I-think-I- can-I-think-I-can-...' as it puffed up the hill.

>> Interestingly, three cylinder steam engines have an unsatisfying
>> rhythm with three short and three long strokes... 1-2-3--4--5--6-
>> 1-2-3--4--5--6...  This was known as the Southern Pacific Type around
>> here and these locomotives were numbered the 5000 series.

>> http://www.steamlocomotive.com/losangeles/sp5021.jpg
>> http://www.steamlocomotive.com/3cylinder/#5021

> Darned nice explanation--thanks.

> Do you know if the three-cylinder rhythm just sounded odd?  Or did
> it have a practical drawback?

There is a drawback and those of us old enough to remember heavy
freight trains starting may recall the sound of a locomotive "burning
rubber" so to speak.  That railroad steam engines had this effect was
not understood by the railroad business and even today, those who
maintain historic locomotives are not aware of the asymmetry of the
stroke and believe it is a quirk of valve timing.

As has occurred often in my engineering career, be that tribology,
metallurgy, automotive suspension, cable car brakes, tubular tire
rolling resistance,... when explaining these concepts, the first
response is, have you ever raced an F1 car, or operated a cable car,
or had your hand on the throttle of a steam engine?

Wheel spin on a steam engine occurred more often than engineers want
to admit and it was mostly a result of this asymmetry with more
experienced engineers.  They would open the throttle just enough to
get a solid stroke or two and believed they were in the clear, only to
get wheel spin on the next stroke that just happened to be on the more
powerful (shorter) portion of the cycle.  When starting, knowing in
what part of the cycle the engine was, was not discernible and is not
detectable without an indicator of what the position of the main-rod
is.  That no such indicator or visual feedback existed reinforces my
belief that this was never analyzed over the 100 years of steam
railway operations.

A three cylinder engine took longer to go from one phase into the
other but articulated locomotives with four cylinders on two separate
set of drivers were less prone to wheel spin because the occurrence
was so drastic that it was avoided at greater effort.  I never heard a
Southern Pacific AC spin its wheels pulling out of the freight yard.
These were mammoth engines fairly unique in design (there were no
others other than prototypes) and found only on the Southern Pacific.
They were possible because most of the SP was oil (bunker-c) fired and
could have a fuel tender at the "wrong" end of the boiler.

http://trains.nute.ws/4-8-8-2/SP4294.htm

This is the only one of these saved from the cutting torch through all
sorts of devious excuses of, for instance, in case of national
emergency this locomotive could move essential freight over Donner
Pass.  Today, no one would think of scrapping the fabulous piece of
heritage.  It is the center piece of the Sacramento RR Museum.

In contrast, there are 11 UP Big Boys on their wheels but not running:

http://www.steamlocomotive.com/bigboy/

This was the most powerful steam engine built and was used to haul
freight over the continental divide at Sherman Hill Wyoming.

http://www.trains.com/Content/Dynamic/Articles/000/000/001/820uxonh.asp
http://www.nps.gov/stea/bigboy.htm
http://steamcad.railfan.net/
http://steamcad.railfan.net/bigboy.htm

This drawing can only be fully appreciated on a CAD system on which
one can zoom in on the many fine details of this beast. UP 4002.

Jobst Brandt
jobst.brandt@stanfordalumni.org

From: jobst.brandt@stanfordalumni.org
Subject: Re: vibration damper for handle bars
Newsgroups: rec.bicycles.tech
Message-ID: <fSqRd.7394$m31.91399@typhoon.sonic.net>
Date: Fri, 18 Feb 2005 18:55:07 GMT

JP who? writes:

>> A three cylinder engine took longer to go from one phase into the
>> other but articulated locomotives with four cylinders on two
>> separate set of drivers were less prone to wheel spin because the
>> occurrence was so drastic that it was avoided at greater effort.  I
>> never heard a Southern Pacific AC spin its wheels pulling out of
>> the freight yard.  These were mammoth engines fairly unique in
>> design (there were no others other than prototypes) and found only
>> on the Southern Pacific.  They were possible because most of the SP
>> was oil (bunker-c) fired and could have a fuel tender at the
>> "wrong" end of the boiler.

>> http://trains.nute.ws/4-8-8-2/SP4294.htm

> Your reference notes that it was originally built as a Mallet and
> rebuilt as a "simple compound".  The Mallet design used recycled
> steam from the high pressure engine to power the low pressure
> engine.  Because of the different pressures between the two engines,
> and because there was nothing to synchronize them, there almost must
> have been some degree of wheel slip, but I guess it could be the
> opposite kind- where the wheels of the front engine are scooted
> along the rails without the pistons moving or the wheels revolving;
> conversely, getting enough steam to the front during starts would
> seem likely to require slipping the rear; probably at the time you
> heard them they had already been rebuilt to simples (the term
> "simple compound" is an oxymoron- Mallets are compounds, engines
> that run off high pressure steam only are simple).  At that point
> the slippage could have been much less noticeable but still probably
> existed because the engines were still not synchronized- any
> difference in traction between the two engines would necessarily
> result in wheel slip on one or the other.

Steam is compressible, unlike hydraulic liquids, so the difference is
at best a slight difference in torque, without slip.  Besides, the
primary and secondary cylinder sizes were designed to accommodate the
difference in volume and pressure.

http://www.catskillarchive.com/rrextra/blwmal00.Html

The above article is not written by a mechanical engineer or
railroader, which is apparent from his misunderstanding of tractive
effort.  Tractive effort is solely the weight on the drive wheels and
has nothing to do with the method of diving the wheels.  It sounds
like a PR article from Baldwin at the time.  The drawings are of
European locomotives.

Although M. Mallet thought he had a good idea, it had no fuel or power
advantages and was more complex than the single expansion engine.
Besides, the huge second expansion cylinders were difficult to fit
into the loading gauge (width of clearance).  There was a spate of
Mallets built but later designs reverted to single expansion.  The UP
4000 Big Boy was the culmination of powerful steam locomotives,
distilled from its predecessors and of course the UP 3900 series
Challenger 4-6-6-4 that look like an identical twin if you don't count
wheels or measure length.

UP 3985 is operational today and is used to pull a UP gold and yellow
1950's streamliner business train to various parts of the system as
you see it here:

http://www.uprr.com/aboutup/excurs/graphics/my3985.jpg

Jobst Brandt
jobst.brandt@stanfordalumni.org