[PRCo] Re: Interurban PCCs_and_Models_Propulsion,_etc.

Boris Cefer westinghouse at iol.cz
Mon Mar 28 10:53:07 EST 2005


Nice, Jim!

Of course, to maintain the speed, you have to keep the pedal on the steel
floor. If the car does not show any tendency to accelerate then, it means
that all mechanical resistances are in balance with the tractive effort
provided by the traction motors and you are running just at the balancing
speed for that particular track conditions and car load.
When you suddenly get on a downgrade, it represents a "negative" resistance
which is added to the tractive effort and helps to accelerate the car until
a new balancing speed is reached when the acceleration ends.
Even on a 6 % or 10 % downgrade the car has a theoretical speed at which all
forces would get in balance and the car would stop acceleration, but guess
it is far behind the motors' mechanical capabilities as they would fly in
pieces.

The service 17xx had possibly higher field shunting (?!) and was thus
capable of higher speed.

At high speeds the dynamic spotting is too heavy because the accelerator
does not have enough resistors to put in the braking loop and keept the
dynamic current at a proper value, which is between 10 and 30 Amps for each
motor group (20 to 60 Amps total current). Your equipment does not
ampermeters on driver's desk. We have! So we can observe what happens in the
propulsion circuits and how heavy the spotting is at very high speed. Before
additional field shunting was developed, it was whole not rare to see 200
Amps of spotting current on ammeter!

B

----- Original Message -----
From: "James B. Holland" <PRCoPCC at P-R-Co.com>
To: <pittsburgh-railways at dementia.org>
Sent: Monday, March 28, 2005 6:07 AM
Subject: [PRCo] Re: Interurban PCCs_and_Models_Propulsion,_etc.


>
> I-F  one doesn't keep the pedal on the floor, then spotting takes over
> and the car automatically slows.      So it is necessary to keep the
> pedal there to maintain speed  --  the indication with M11 being that
> the car was Flat Out Moving but the service car, PCC Interurban 17xx
> which had to stop for passengers, Still Caught Us!----THAT  was my point
> (in the quote below!!)       If the PCC is traveling downhill with power
> pedal floored then speed  IS  increased  --  letting of power allows for
> spotting and this is quite heavy at such speeds and would definitely
> slow the PCC considerably  --  experienced this Multiples Of Times here
> in SF through the tunnels.
>
> Son Of A Gun, John, you know that this same principle holds in models as
> well, even transistorized throttles and DCC    ----    Very Good Thing
> you mentioned this so it can all be tied together!!       Turn the
> throttle of the Power Pack All The Way Up and we get full speed, half
> way slows the car down instantly, and off is Off  --  Instantly!!!
> This  Is  Fun! :-) :-P :-D
>
>
> Transistorized throttles were all the rage in the 1960s and I had plenty
> of time in Kodiak to study the model railroad magazines to design my own
> throttle but never built it until out of the Canoe Club.       The
> design allows for adjustment of acceleration  *Rate*,  Braking  *Rate,*
> and  *Coast*  when power was released.       Yes    ----    the pot that
> controlled acceleration was turned completely Off and the model
> trolleycar kept right on rolling because of a capacitor in the
> circuitry  --  the car gradually slowed but could go quite a
> distance.       Braking was through a separate pot which drained the
> capacitor more quickly  --  the pot just chose a  *Rate*  of
> deceleration with increased movement in the pot choosing a faster rate!
>
> I built a very crude set of foot pedals to operate the models and could
> do so for multiples of hours without a break  --  NO 10-hour limit
> behind the controls!!!!!!!       The deadman cut power to make an
> instant stop IF needed but I never used that feature but Had to keep the
> deadman depressed to have power!       Boris says this is not true of
> PCC operation, and I certainly accept his critique, but it  *seemed*
> that it was possible to build up speed with an All-Electric and then
> back off on the power pedal to just engaged to maintain that speed  --
> this way one could make a quick transfer to the brake pedal if
> needed.       Could not do this with the transistorized throttle and
> this disappointed me, but in reality, the transistorized throttle did
> mimic all aspects of All-Electric PCC acceleration, coasting, and
> braking quite admirably.
>
>
> I had a contactor in the overhead to operate my track switches ala the
> prototype  --  coast through the contactor and the turnout remains //
> sets for straight through  --  hit the toggle on the control panel when
> the trolleypole hits the contactor and the turnout sets // remains in
> diverge!       Worked like a charm!!
>
>
> DCC has the  *Rate*  features built into the decoders but the advantage
> here is that the Overhead voltage is constant  --  Always On at maximum
> setting!       This alone is an advantage, esp at lower speeds to allow
> the equipment to roll smoothly without jitters from contact problems at
> low voltages.       Contact can always be a problem but the constant
> voltage lessens it.       It is also possible to have the PCC bell,
> interurban horn, compressor sounds for Air-Cars operated through the
> decoder and it is also possible to turn on and off the roof light, head
> light, interior lights separately!!!!!!!
>
> Stationary or mobile decoders can operate various wayside items to
> control turnouts, animation, lights and a whole host of other items.
>
>
> Computers can be connected to the  *RR*  to control the equipment,
> signals, turnouts etc. - one, any combination, all.       Computers can
> have full control of the RR and total manual control of the RR is also
> possible while the computer controls signaling and other items.
> Any combination of automatic // manual control  --  i.e., computer
> operating some equipment and humans operating other equipment  --  is
> also very possible.       Very software intensive but I have basic
> outline of what I personally would like to do in this area and Chubb's
> books on Computer/Model Railroad Interface  (C/MRI,)  both the basic
> description and heavily technical volumes which will help to make this
> all possible.       Have the computer operate several cars on one line
> while a human(s) tries to keep a schedule on the same line!       Email
> lists also help with the learning curve.
>
> But DCC gets more interesting each day with all the new developments
> --  much like computers for the last couple decades.       Transponding
> and Bi-Di are now quite possible but still in the development phase and
> this could lessen the need for computer control or aid the computer in
> identification of equipment and location.       Radio control is all the
> rage because it allows for freedom of movement of the operator but
> suffers from interference of  Sloppular__Phones  as the frequency used
> by both overlaps!       Absolutely Detestable Thought that one of these
> ({[phones]})  could take control of a model!!!
>
> Twins were completely enthralled with  lrvs and I built each a Boeing HO
> model using slides of each of them at the controls of a prototype Boeing
> as the actual ends of the model  --  looked decent enough.       Sides
> were plastic and were heated in the oven at very low temp, then pressed
> over a wood block which I had carved to the basic lrv design with
> fishbelly coutour  --  wider at belt rail than at roof line and
> skirting  --  with curved taper to the ends.       These were Christmas
> presents and this caused quite a bit of tension as I had to lock myself
> in my room to do the work!
>
> Both lrv models could be operated simultaneously and individually by
> each of the Twins as the lrvs picked up power from the overhead but
> grounded through only one of the two rails  --  right rail for one lrv,
> left rail for other lrv.       A contactor in the overhead as the model
> entered the single track section from either direction activated a
> simple switch machine with DPDT contacts to change the wiring alignment
> in the rails to keep the right and left rails aligned with the equipment
> direction  --  without this the lrv would be controlled by the other
> throttle in one direction along the single track.       If one of them
> ran the signal while the other was in the single track, the latter took
> control of both models    ----    and boy, the fuss this created!
>
>
> Including several photos which the email arranges in its own order
>
> URLs  should be at the very end of the email:::
>
>
> 1.>--   Prototype Boeing lrv shells
>
> 2.>--   Construction of HO layout for Twins.
>
> 3.>--   HO lrv body shells
>
> 4.>--   Completed lrvs on upper loop  --  contactor for acting switch
> machine for electrical circuit in single track can be seen in overhead
> of  lrv  in the back.
>
> 5.>--   A view into  "Downtown!"
>
>
> Before transferring to Kodiak in 1964, I had written to SLCCo and Clark
> --  SLCCo sent me drafting plans for all  PRCo  PCCs  as 0.75"=1'0"
> while Clark sent 1/4-Size(3"=1'0"!) prints of trucks for air cars and
> All-Electrics, both the B2 and B2B  --  some drawings included of
> various parts full size!!!!!!!       My dream was to have a 1"=1'0"
> PRCo  PCC  Interurban  --  a 1.12 model  --  or several if at all
> possible  --  And  I  Am  Still  Hoping  For  This.
>
> If anything is scaled down to 1.12 size it is done in 3-dimensions  --
> Length, Width, and Height!       And if it was possible to shrink
> something like this, then it can be claimed that the weight of the
> prototype reduced to 1.12 size would be  1/1,728.       A 1.12 PCC would
> weight almost 21-pounds; each truck would be  *aprox*  5-pounds  --
> hold a 5-pound bag of sugar in your hand for reference!       The body
> with all gear would weigh about 10-pounds and the truck, B3 Of Course,
> could be sprung ala the prototype for some very interesting action on
> scale prw!!!!
>
> The NMRA provided formulas to determine the motor characteristics I
> would need to power this car  --  one motor/axle ala the prototype  --
> and I had information from Pittman on the motors I could use.       Size
> is a problem  --  motors would fit trucks with barely any room to spare
> --  and body bolster would need modification to fit the motor in.
>
> In Those days, control would be through typical Model Aircraft radio
> control with various servos controlling apparatus on the
> equipment.       I could actually have a rotary accelerator by using a
> rotary rheostat but would have used a separate one for dynamic braking
> as the control features would be too complicated using one for
> both.       Actual Dynamic Brakes would have slowed the car  --
> magnetic track brakes could be used for emergency  --  and a lockout
> relay would prevent the friction brake from applying until the dynamic
> had faded.       RCA provided me with sample circuits for controlling
> the lock out relay and for charging the onboard battery which would only
> be used if the trolleypole dewired to prevent the drums from applying
> until brakes had been applied  --  otherwise all power would be received
> from the overhead.
>
> Today, however, DCC decoders Are  NOW  available to control the amount
> of current needed to run such heavy equipment  --  I would most likely
> use separate ones for acceleration and braking.       Hope I am able to
> make this happen!
>
>
> -- Attached file removed by Ecartis and put at URL below --
> -- Type: image/jpeg
> -- Size: 225k (230632 bytes)
> -- URL :
http://lists.dementia.org/files/pittsburgh-railways/Boeing_lrv_shells.jpg
>
>
> -- Attached file removed by Ecartis and put at URL below --
> -- Type: image/jpeg
> -- Size: 144k (148437 bytes)
> -- URL :
http://lists.dementia.org/files/pittsburgh-railways/HO_construction_1978xxxx
_JBHolland.jpg
>
>
> -- Attached file removed by Ecartis and put at URL below --
> -- Type: image/jpeg
> -- Size: 92k (94795 bytes)
> -- URL :
http://lists.dementia.org/files/pittsburgh-railways/HO_lrv_BodyUnit_197910xx
_JBHolland.jpg
>
>
> -- Attached file removed by Ecartis and put at URL below --
> -- Type: image/jpeg
> -- Size: 111k (114595 bytes)
> -- URL :
http://lists.dementia.org/files/pittsburgh-railways/HO_lrvs_UpLoop_19791225_
JBHolland.jpg
>
>
> -- Attached file removed by Ecartis and put at URL below --
> -- Type: image/jpeg
> -- Size: 285k (292741 bytes)
> -- URL :
http://lists.dementia.org/files/pittsburgh-railways/HO_PCC_Key_19791225_JBHo
llant.jpg
>
>
>




More information about the Pittsburgh-railways mailing list