[PRCo] Re: Interurban PCCs_and_Models_Propulsion,_etc.

[James B. Holland]

Thank You, Boris  --  you have been a great instructor in the mechanics 
of PCC operation!


Boris Cefer wrote:

> 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!
>>
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>

-- 
Jim__Holland


I__Like__Ike.......And__PCCs!!

down with pantographs ---- UP___WITH___TROLLEYPOLES!!!!!!!