Jimmy's Northline Raceway
A/C Operating System
I'd like to share information with other model car racers on
a system that we have been using to power Northline Raceway for the past 20
months. We have been testing this system of running two independently
controlled cars in one slot, powered by an AC train transformer, with
surprisingly successful results. We have now, confidently put this system
to full time use. The inexpensive benefits could affect how you design
your next routed track. Or, even prompt you to add passing lanes onto your
existing layout.
Two cars independently driven in each
slot with improved control
Northline Raceway is a wood routed track nearly 140 feet long
that was originally designed to run 4 cars. (See Model Car Racing #14) Drivers
have the ability to change over to slots routed for them on either side of the
road. This creates two separate ways to do a lap, which allows cars to
pass or block on the scale width roadway. By clustering the slots into two
groups, with just enough room between the groups to allow cars to pass, the over
all width of the track is reduced. A narrower roadway helps any track design by
allowing a longer layout in the same space.
It is important to understand that adding passing lanes that
cars get switched over to, will actually reduce the track's width. (We'll do the
math further on to prove it to you) This dramatically increases the linier feet
of racing, since more race track can be designed into the same area. Note that
without a lane changing mechanism and a separate passing slot cut somewhere
around the track, two cars can run in the same slot, but will not be able to
pass one another. This restricts the lane sharing benefits of this AC
system to custom designed routed tracks that have a lane changing mechanism and
passing lanes built in. But, the benefits of nearly twice the racing, in
the same space, for very little money is worth breaking from the conventional
slot car "pass everywhere with eyes closed" mindset on your routed
track.
Rediscovering old technology.
Fifteen years ago, when I knew that the lane change feature
built into the hairpin on Northline Raceway worked well, I realized that if I
could get two cars running in the same slot they would be able to get by each
other by using the passing lanes. This would almost double the number of
cars racing on my track. I began looking into digital train control without much
luck. Then my brother, an Electrical Engineer, and I spent a year trying to set
up a pulse-width modulating system. But that system, like digital, was
complicated to add to a routed track and not user friendly in terms of visitors
bringing over their conventional cars. Nothing worked well on our wood track and
we were about to give up.
However, I remembered clearly that many years ago there was a
TV commercial showing Eldon cars changing lanes. Also, I recalled that in
the mid sixties my brother and I got Eldon cars that were labeled
"Selectronic". I was upset when they would not run on my
standard Eldon track. I cut out this electronic thing (diode) in line with
the motor, and bingo… the car worked.
Also, my conventional DC Eldon transformer went dead that
year and the jerk at the local hobby shop dumped a "Selectronic"
transformer on me. The cars just sat on the track buzzing. Since it
was an electronic item he would not take it back. At 13, that was an event
that was hard to forget since $12 was a fortune to me then! Those memories led
us to an idea that has improved the performance of Northline Raceway 200%.
My brother theorized that the buzzing must have been because
the Selectronic transformer was sending an Alternating Current to the
track. Alternating the polarity 60 times each second. I insisted that if
Eldon could get two cars to share a lane this way, so could we.
The results of almost two years of testing have left us
confident that this simple system has more than one benefit over the typical DC
power that model racers use today. Initially we planned to run this AC system
only when we wanted 8 cars on the track. We get such realistic control of
the cars that we now race even just two cars on AC.
How AC powers two cars in a slot with
independent control
By powering the track with a variable A/C current (old, used,
cheap Lionel train transformer) and rectifying the supply with a $.10 diode
wired into each car, we are able to send two separate signals to one lane.
Also, a second diode must be put into the circuit of the controller that is
coordinated with the diode in the car it controls. The diodes must be in
the same direction in the circuit. The diodes at the controllers can be
placed in line with either the black or white leads of the controllers but must
be in sync with the diode of the car it controls. The red brake line must
be disconnected at all times running the AC two car system.
Diagram to add diode
into car wiring : pdf
Diodes block the flow of power in one direction and allow
current to flow in the opposite direction. Our work shows that any diode
will work. We use diodes bought from DIGI-KEY.COM. Mail ordered in
bulk of 100 for around $20.
One controller and car in the lane is referred to as car
"A" and the second controller and car in that same slot is
"B". 60 times each second, power from the AC transformer
reverses polarity. The diodes in the circuit of car A block the flow of
power to it whenever it is not the current who's polarity allows it to move
forward. The same with car B, which has it's polarity to it's motor
reversed. When car A is coasting 60 times each second, car B gets power
through the B controller. When car B coasts 60 times each second, car A
gets power through the A controller. Yes, each car coast for half the
time, but with almost twice the voltage pulsing 60 cycles a second, it's tell
tale growl is all you see or hear. The cars equipped with lighting
circuits still work just fine.
Instead of 4, we can now run 7 race cars at one time on our
track, with the 8th car being a pace car that leads the field. The pace
car shares lane 4, which on our track, runs down the center of the roadway with
no lane change capabilities. When the field is grouped for the rolling start,
the safety car picks up the pace, then pulls into the pits to clear the way for
the 7 cars roaring to the starting line. The system works very well, and
is quite inexpensive. Once you know the combination and placement of
diodes it is cheap and easy to do.
Conventional track design vs. the passing
lane design with switching capabilities
In order to understand the narrow track width design
advantages allowed by a system that can independently run two cars in one slot,
we need to compare the road width of a conventional routed track (slots around
the layout spaced widely apart) vs. a track designed with an extra passing slot
cut around the course for each car (allowing cars A & B sharing a slot to
pass or block each other when switched to a passing slot cut on the opposite
sides of the road).
If we were to design a conventional DC track to run (6) 1/32
scale cars using 1/8" routed slots, it would require a min of 2.75"
between slots, and 1.75" on either side for minimum track edge
clearance. The total road width on this layout would be 18".
(Of course, track width at turns would be expanded, but for this comparison
we'll compare just the straight sections) Now, let's design a track to
race (6) 1/32 scale cars on the AC system that will run two cars independently
in one slot. Since two cars can share the same slot, we need to cut 3
slots in a tight group spaced 3/4" apart, and 1.75" from the tracks
edge. Then we cut a second group of 3 slots, again 3/4" apart,
2.75" from the first group. Whenever a driver chooses to switch to
the second group of 3 slots (the "passing lanes") the 2.75" space
between the groups allows any car to pass any other car when they run in slots
on opposite sides of the track. The total width of this roadway, allowing
1/8" per slot and another 1.75"min distance to the other edge of the
track is now 9.25"
The benefits of a narrower roadway
The conventional design required 6 slots cut to allow 6 cars to
race on an 18" wide track all passing at will in an unrealistically typical
"slot car" manner.
With the "passing lane" design and the AC system, 6
slots would also need to be cut. However, since the AC system allows two
cars to inexpensively share a slot, we now can have 6 cars racing on a track
9.25" wide. That's almost half as wide! This allows for double the racing
layout in the same space ! The track design running 6 cars on this narrow
roadway can be designed to be nearly twice as long. Plus blocking and
passing makes for much more realistic and exciting model car racing.
If you are designing a miniature road course, by adding this
passing slot in addition to the regular slot, and building in a lane change
mechanism, you can now run double the cars, nearly double the distance in the
same space for the cost of an old train transformer and some $0.10 diodes.
A few wood track builders, who have investigated these ideas,
are currently in the process of revising their plans to go from 2 cars D/C to 4
cars A/C by adding these extra slots to their track design. One efficient track
builder in Grand Rapids MI. is even planning to use a simple auto choke cable
and spring to actuate his manual lane change switches. This pull cable, for
changing into the passing lane, is far simpler than using an electronic solenoid
to drive the switching mechanism that we now use on Northline raceway
The added benefits of a pulsing higher
voltage
The car control is fantastic! You can make a car creep into the
pits or go balls out down the straight. The cars growl as they go around, which
everyone agrees sounds cool. Although the motors run warmer, (not hot) the
GWLTRSCIOGBs (Guys Who Like To Run Slot Cars In Other Guys Basements) here in
Michigan have thrashed over 75 different cars for many hours with no negative
affects. There are tracks in this area, without lane changing capabilities
that are now running strictly AC, just to take advantage of this added
control. In this case, diodes in the cars are not required. One diode per
controller is wired in either the black or white controller leads and the track
is powered by a variable AC train transformer. Again, the red controller
leads must be disconnected.
Not only is control improved, but there is an added benefit for
copper taped tracks. The oxidation on the copper is no longer such a
hindrance since the cars run on twice the voltage for half the time. The
16 to 18 volts burns through the dust and oxidized copper film. No more
repeated warm up laps to polish in the copper so cars don't stall.
A big plus with this system is that when guys come over with
regular cars, no diodes installed, they can still put their car right onto the
track and run perfectly one car per lane. With the same great sound and
control. Unlike unique digital cars, it's not a problem as long as the
lane is not shared by another. But, any standard car can be made to run
two in one slot with the simple addition of the inexpensive diode wired in line
with the motor.
We have not had the D/C power supply on much since Northline
Raceway got the new A/C system going. Actually, the only time the DC power
supply goes on now is when we do a comparison demonstration to highlight the
difference in control to new drivers. They all agree, that although the
lap times drop, drivability is better and smoother, which makes the racing look
more realistic.
The hurdles
No new idea comes without some issues. One hurdle is that
you lose braking capabilities. It has not been a problem here though, since good
drivers know that the fastest laps are done coasting through the corners.
The red controller brake lead must remain unhooked or disconnected from the
circuit. Happily, there is a distinct reduction in rear end tapping sounds
at the end of each straight since all the cars are now running no brakes.
A second curious issue is that older diehard slot racers take a
while to get used to not having the unrealistic amount of wheel spin that they
were weaned on. Veteran drivers are used to gobs of wheel spinning torque
as they enter a straight. The AC system is a more realistic way to run
cars. The system's reduced torque is more prototypical in that you must
exit a turn as fast as you can, to get the highest speed at the end of the
straight. No different than real racing. Believe me, the cars can go
plenty fast! New guys never notice the reduced torque until we switch back
to DC. Then the cars revert to the jerky, wheel spinning, limited control
that we've all gotten used to. After an hour of running, even the veterans
agree that it is a great smooth way to run cars. No more flying blurs
darting mindlessly around the track. It takes a new mindset to drive, but
it looks smooth and realistic!
For scale model routed tracks, this AC system with secondary
passing lanes, provides more action with the added cars, more control, more
linear feet of racing in the area allowed, at a minimum of cost. Although
there are double the cars on the track, the racing is smoother than with half
the cars on DC. All of the GWLTRSCIOGBs who have run the past 20 months on
Northline Raceway agree that they are having more fun running with larger fields
of cars running with more of the look of realistic racing. Even though lap
times are slower than on DC, the cars are still lapping the track 100% faster
than prototypical speeds. But, with double the racing action because 8
cars are running side by side and nose to tail with much smoother control!
For answers to more questions related to the operation of Northline Raceway, see
the "Model Car Racing" Magazine #14. Robert Schleicher's books
on Model Car racing are also a great reference. The word on building and
designing wood routed scale tracks on the internet is Luf Linkert's www.oldslotracer.com
And, for answers to questions specific to lane changing and the AC system on
Northline raceway see Jimmy's Raceway Q & A on the Professor Motor web site www.professormotor.com/jimmysFAQ.shtml
I am excited to share what we've learned with others who have
our passion for realistic model racing and are interested in building a routed
track to take advantage of all the benefits that this system has to offer.