[PRCo] Re: B2 and B3 Trucks

[Boris Cefer]

Correction of the correction: Jim had written B2!!! Guess he was comparing
the spring equalization of the B-2 with the frame equalization of a truck
that would contain rubber bushings in all 4 sideframe clamps.

Speaking of trucks, when I saw the remaining Pittsburgh PCCs equipped with
B-3 trucks, I noticed that PAAC added SOMETHING (rectangular plates) to the
rubber blocks which restrain bolster movements, but I was not able to
recognize what that SOMETHING was, because it was painted. My opinion is
that this improvement intended to provide protection of the rubber blocks
against direct contact with the bolster to avoid wear of the rubber surface
and it was possibly a steel or fibre plate screwened to the rubber.
On 1711 at PTM I also noticed that its original SLCCo truck (the front one)
had the rubber block pockets like worn by an excessive lateral movements of
the bolster against the sideframes. That would indicate that the rubber
blocks had not been maintained in adequate condition and the bolster was
allowed to move from one emergency stop to the other without any dampening
by the friction between the rubber and bolster (even small amount of
friction because the rubber blocks should not be inserted in their pockets
with large pressure).

Boris

----- Original Message -----
From: "Fred Schneider" <fschnei at supernet.com>
To: <pittsburgh-railways at dementia.org>
Sent: Friday, January 28, 2005 3:39 AM
Subject: [PRCo] Re: B2 and B3 Trucks


> Correction:  The B3 truck frame can only bend at two corners but that is
all
> that is needed to allow flexibility at four corners.  (see Jim's statement
that
> is now in a larger font, below)  Take your thumb and forefinger of each
hand
> and touch them thumb to thumb, forefinger to forefinger to simulate the
box
> shape of the frame.   Now notice how you can move them so that you can
lift any
> one of the four corners independent of the other three. Lifting a wheel at
the
> fix corner flexes the rubber in two non-fixed corners.   Functionally it
is the
> same as the B2.  It allows each wheel to apply equal weight to the rail no
> matter which corner is higher.   the B3 had frame equalization, i.e. the
frame
> was allowed to flex.    It wasn't totally common but there are other
designs
> out there that did the same thing, such as the St. Louis EIB series
(you'll
> find them on a lot of the older Johnstown cars).
> Spring equalization, however, was much more common.  Meaning springs were
used
> to transmit equal weight on the rail at each wheel  It just takes a lot
more
> parts to do the same thing
>
> I wish I had all of the comments that went back and forth between the
engineers
> during the ERPCC and TRC truck design phases.  I suspect that for both the
B1,
> B2, B2b and B3 designs, minimum weight remained a very important
> consideration.  When Philly Suburban asked for a MCB type truck for their
1949
> St. Louis cars, they got a PCC style body with a fabulous ride not matter
how
> rough the track was.  But it had solid steel wheels and a solid steel
frame ...
> there wasn't an ounce of rubber to keep the high frequency noises from
> penetrating the car body.  Noise suppression was not as important on an
> interurban railway as it was on city streets.  It was a much heavier
design.
>
> Boris's statement about the movements a truck dampened was very good.  The
B2
> bolster hangs on four swing links.  If centrifugal force tries to push the
body
> to the outside of a curve, it is lifted up on the swing links and
immediately
> falls back down to center.  Just picture a beam hung on rods at each end
that
> can rotate about an axis.   On the B3 the bolster simply moves sideways
against
> rubber blocks.
>
> The B2 designs were not all alike.  The earliest cars had rubber springs
> vulcanized to steel coil springs, eight to a car, two at each end of each
> axle.  The were simply following on a practice done for years .. that one
type
> of spring has different properties than another.  For years the industry
used
> eliptic springs above coil springs for the same reason.  When World War II
came
> along, with the attendant rubber shortages, the few new cars came through
with
> steel coil springs.  Come to the Baltimore Streetcar Museum some day when
I'm
> there and I'll show you just how rought steel coils alone can be.  When I
was
> doing the PCC book I came across all sorts of spring drawings for a B2
truck.
> I surmised that this was one of those cases where "Its your car.  You're
paying
> for it.  You can have whatever you want."   The same thing resulted in a
> ghastly number of different control versions, mostly just differences in
> resistance development.  An engineer from GE told me that there was no
valid
> reason for all the differences except that GE was in business to make
money and
> they would make whatever the customer wanted.   Westinghouse wasn't dumb
> either.
>
> Remember two that one of the most important things the ERPCC was trying to
do
> in 1930-1935 was to reduce noise (audible vibrations) as well as rough
riding.
> They were trying to copy an automobile.  The B1 and B2 trucks gave the
quiet
> cushioned ride they wanted.  The B3 came about because of a need for a
truck
> that could ride acceptablly well on Pittsburgh's rough unpaved tracks.  It
> should come as no surprise that PRC was behind the B3 because they had
more
> miles of private right-of-way than any city of that size or larger.  And
> therefore the needs were different.
>
> For the model builders out there who question why we must equalize a truck
...
> it isn't done in small models such as HO and N gauge because we solve the
> problem of uneven track with gigantic flanges.   And model builders need
not
> worry about comfort to the little people in their cars, nor to problems
with
> momentary loss of traction to one axle.
>
> I'm thinking through my fingers when I say that there might also have been
> fewer problems with the B2 had American's not staggered rail joints.  Had
we
> put all the rail joints opposite each other like the British do, there
would
> have been a lot of bounce on rough track but not a lot of sway.
>
> "James B. Holland" wrote:
>
> > All the  *problems*  with B3s are lateral and that is where the B2
> > excels.       And I believe a case can be made for the B2 being better
> > on rail joints as well since the framing of the B2 allows flexing at All
> > 4-corners of the truck, Not Just 2.       Vertical shocks have more room
> > for absorption in a B2 and less is transmitted to the bolster and car
body.
> >
> > Going to a system like Shaker is where one can experience an absolutely
> > exquisite ride on B2 trucks at Break Neck Speeds.       Have done that
> > often.       The Operators Did Not Like the B3-equipped IT cars because
> > they bounced considerably  --  never had the opportunity to ride them on
> > Shaker but I Did Try!       But I shall dismiss the problem bouncing to
> > age and very low maintenance of the springs and spring pots over time
> > --  the cars were only for extra usage to fill schedules.       Had they
> > been brought up to standards of other Shaker equipment, the ride may
> > have been much better and without bounce.
> >
> > Boston is also an excellent example of using B2s on prw at High
> > Speeds.       From an engineering perspective the B3 may be better on
> > prw but from the perspective of the rider, I think the B2 would be Just
> > As Good and Possibly Better than the B3.
> >
> > The B3 being stiffer makes the ride harder  --  but don't get me wrong,
> > I Favor the B3.
> >
> > The  BIG  area where B2 fails is that motor vibration is transmitted to
> > the car body because the motors use the same springs for shock
> > absorption that supports the body.       Riding a B2 at speed on PRCo
> > was quite an experience with body panels and windows and all else
> > rattling to beat a band and on prw the value of the B2 is masked by the
> > motor vibration problems.       But otherwise I found the Actual Ride
> > Very Acceptable on B2s on prw  --  we had quite a bit of prw on city
> > lines in the Burger.
> >
> > I am Quite Partial to the  B2B  and  Know its Absolutely Wonderful
> > Riding Qualities from experience.       What you say about the B2B being
> > between a B2 and B3 may be true from an engineering standpoint, but I
> > would Far Rather Ride a  B2B  than Either a B3 or B2.       The B2B
> > performance on city prw was excellent  --  would liked to have
> > experienced the same on Interurban prw.
> >
> > How this all affects maintenance may be another story altogether.
> >
> > Jim__Holland
> >
> > Boris Cefer wrote:
> >
> > > No no no! The B-2 is softer vertically (=> bouncing), while the B-3 is
> > > in vertical direction stiffer and thus better for prw with rail joints
> > > in poor condition (but relatively straight vertically).
> > > The B-2 does not transmit lateral irregularities of the track to the
> > > body as much as the B-3.
> > > As for the B-2b, the truck bolster was laid on the truck frame
> > > somewhat higher than on standard B-2, from which I deduce that the
> > > riding quality on B-2bs was a transition between B-2 and B-3, but
> > > closer to B-2.
> > >
> > > Boris
> > >
> > > ----- Original Message -----
> > > From: "James B. Holland" <PRCoPCC at P-R-Co.com>
> > > To: <pittsburgh-railways at dementia.org>
> > > Sent: Thursday, January 27, 2005 7:16 PM
> > > Subject: [PRCo] Re: Nosing
> > >
> > >
> > >> You Say It So Nicely!
> > >>
> > >> So in theory, the B2 would provide a better ride on open prw than the
> > >> B3 -- yet theoretically the B3 was designed Just For That kind of
> > >> operation!!!!!!!
> > >>
> > >>
> > >> Jim__Holland
> > >>
> > >>
> > >>
> > >> Boris Cefer wrote:
> > >>
> > >>> The problem of B-3 is obvious. The main (coil) springs are higher on
> > >>> B-3 than on B-2, which means that the B-2 truck is laterally stiffer
> > >>> than B-3. In addition to that, on B-3 trucks the car body rests on
> > >>> the truck frame at higher point than on B-2s. The B-2 truck bolster
> > >>> design is selfcentering and the weight of the car body drives it to
> > >>> its lowest position (the result is automatical dampening). Also the
> > >>> tapered tread plus inadequate gauge clearance (bad track) provides
> > >>> very good excitation for lateral motions of the truck and whole the
> > >>> car body.
> > >>>
> > >>> Boris
> > >>>
> > >>> ----- Original Message -----
> > >>> From: "James B. Holland" <PRCoPCC at P-R-Co.com>
> > >>> To: <pittsburgh-railways at dementia.org>
> > >>> Sent: Thursday, January 27, 2005 6:41 AM
> > >>> Subject: [PRCo] Re: Nosing
> > >>>
> > >>>
> > >>>> Can be a variety of things.
> > >>>>
> > >>>> [[Snip]]
> > >>>>
> > >>>> It needs to be recognized that all *hunting__is__Not__hunting* --
> > >>>> the differences in design between the B2 and B3 make for different
> > >>>> performance on the same track. There was a portion on Church Street
> > >>>> here in SF outbound between 17th and 18th downhill that was quite
> > >>>> rough -- a B3 equipped car slammed back and forth sideways while a
> > >>>> B2 passed through with barely a disturbance. The Swing link
> > >>>> possibly saved sideways motion on the car on a B2 truck as the
> > >>>> truck itself moved back and forth on the uneven track -- the bad
> > >>>> track was short enough that the motion was not transferred to the
> > >>>> body. But the framing of the B3 truck would even get the spring
> > >>>> pots moving from side to side which then transferred this motion to
> > >>>> the body. The motion ceased when the car passed this brief section
> > >>>> of bad track -- that would not happen with hunting -- hunting seems
> > >>>> to intensify once begun until measures like purposely slowing are
> > >>>> taken to alleviate
> > >>>
> > > same.
> > >
> > >>>> This same type of situation is pointed out in the PCC books about
> > >>>> Chicago B2s and B3s on rough track -- considerably sideways action
> > >>>> to the B3 whereas it is hardly noticeable on the B2.
> > >>>>
> > >>>> Yes, the B3 was developed for open track but have said before that
> > >>>> the B2 did just fine from a ride standpoint -- don't know if it was
> > >>>> more problematic for maintenance. Would Dearly Like To Know what a
> > >>>> ride on the interurban would be like with the *Original__B2Bs* ----
> > >>>> A Truly Superb Ride And The ONLY equipment I have ever ridden that
> > >>>> aptly fit the description of *Riding__On__A__Cloud!*
> > >>>>
> > >>>>
> > >>>> Jim__Holland
> > >>>
>
>
>