Bob has some interesting points there, and I am glad the Bachmann DCC booster does not drop anywhere near 35%.  In fact, it's drop is only 13%.  Thanks to Stan and TOC, we can calculate the no load to full rated load drop as follows:

(17.8 - 15.5) x 100 / 17.8 = 12.921%.

The drop in voltage when you draw another 4 amps of current compared to when you were drawing only 1 amp of current is:

  (17.5 - 15.5) x 100 / 17.5 = 11.429%

Cranking up the 4 amp Shay would only pull the voltage on an E-Z Command booster down 2 volts, not 6.3.  Calculated as follows:

  17.5 - 15.5 = 2.0 volts

(17.5 is the voltage at 1 amp, 15.5 is the voltage at 5 amps)

Bob is correct that motor speed is not a linear function of voltage.  Especially not with dc.  With DCC, it is much closer to linear because we always apply full supply voltage to the motor and regulate the motor speed by how long we apply it compared to how long we do not apply it.  So even though a dc driven locomotive might slow from high speed to a crawl under a particular set of conditions, a pulse width driven locomotive will change speed only slightly to moderately.  Of course, if we are using DCC and are at all concerned with these minor changes in speed, we have the option of using back emf control which works very much like the cruise control in your automobile.  With back emf control in operation, the speed change at a measly 2 volts would be all but undetectable.

Personally, I don't much like running with back emf control turned on.  I like to drive my model locomotive like I would drive a real one.  I like having to work the throttle, opening up a bit going up hills, closing down a bit on down grades.  Someone else drawing down the track voltage?  Not much different than all those little things that affect a real locomotive - a curve wet with dew here, a track a tad tight on gauge there, a boggy spot where the rails settle and you run up hill in both directions, well, you name it.

As I explained elsewhere in this thread, a 5 amp output on a power source is often the guaranteed minimum under a given range of conditions, particularly temperature.  If you get more output at some specific conditions within the limits of the guaranteed range, that is fine and it will not harm the power source.  But do not make the mistake of counting on the greater output at all conditions within the limits of the guaranteed range.  To put that in simpler terms, if Bachmann called it a 5 amp booster but at some conditions within its rated range it produced only 4 amps, you would quite rightly be mad.  But if it produces at least 5 amps in that range, and maybe more, then be glad that Bachmann is using a good, honest rating.

Thanks, Hunt, for hitting the nail on the head.  In his earlier (October) posting, Stan Ames made the outlandish sounding claim that a certain Lenz decoder could run on battery backup and could pickup up DCC signals through tape on the rails.  And that is exactly what approximately 150 model railroaders here in Saskatoon witnessed this weekend.  That decoder is the Lenz Gold Maxi, available from Tony's Train Exchange for $63.95.  Tony's also has the Lenz Gold JST for H0 and Lenz Gold Mini for N scale.  All can be viewed at this link:
http://www.tonystrains.com/products/lenz_decs.htm

I think receivers complete with motor controls and function outputs for lights and sound systems are about $100 more than Tony's price for the Gold Maxi, but if I am in error, I am sure someone will correct me.  As such, I believe these decoders may be a viable alternative to radio control when it comes to battery powered layouts, particularly small to medium sized backyard layouts.  I appreciate Tony Walsham's open mindedness on this, and absolutely agreed that an indoor test on five feet of track is not an adequate substitute for outdoor testing under various conditions.  With that in mind, I can hardly wait for my railway to thaw out so I can get started with these tests.

I agreed with Steve Stockham and would NOT advise anyone with a large investment in battery power with radio control to toss it all out and re-equip his fleet with a new control, as long as he is happy with the setup he is using.  Just like I do not generally advise anyone in small scale to toss out his block control system as long as he is happy with it (and many are.)

Kevin Strong asks a very good question:

QuoteWhich brings me to my third observation. If I'm going to go through all the trouble to install this system, including a block of batteries with enough capacity for running the train (because of the two reasons stated above), why would I want to bother with track pick-up after all?

Sending high frequency signals over wires instead of through air is pretty common.  Think of high speed internet being sent over phone wires and TV signals being sent coaxial cables.  With our railways, we need tracks to carry our trains, why not use them to carry control signals as well?  We certainly would not need large power supplies or boosters to feed power to the rails if we had onboard "blocks of batteries with enough capacity for running the train."   I feel the high frequency signals will probably not require rail clamps to travel from track section to track section (this is but one of a large number of things that needs testing.)

I suspect bobgrosh never made it past the third paragraph of my first posting on this thread.  If he had, he would have realized that the battery backup that he proposed adding to the + and - outputs of a regular decoder's bridge rectifier could only accomplish a fraction of what the Gold Maxi can do.  He may have run over tape on a track, but did he stop on the tape, reverse, accelerate, etc. all on the tape?  I don't think so.  And do I need to explain that if a decoder costs less than a receiver/controller then a decoder plus a battery costs less than a receiver/controller plus a battery??  I assume Bob is making the comparison between battery powered with radio control versus battery powered with decoder control.  But if Bob was considering only of the backup battery, I would be forced to admit that mine cost six dollars total.  Six little Canadian dollars at that.  I am glad that Bob could understand what TOC was saying, because I couldn't.  Except his kind wishes that I learn to like batteries.  If this all works out with the Gold Maxi, I guess I will have to do just that. 

Last October, on the old board, Stan Ames  told us about a new decoder that worked in spite of dirty and/or corroded track.  It even worked, he said, with tape over the rails.  Based on what Stan said, I ordered one of these decoders, specifically a Lenz Gold Maxi, for further testing.  With my garden railroad under 3 to 4 feet of snow, I had to wait until today to properly test it.  And test it I did, at our local model railroad show, before many members of the model railroad fraternity and some members of the public.

The demonstration was simple.  One Aristo-Craft Little Critter locomotive fitted with one Lenz Gold Maxi Decoder running on one five foot section of brass rail with tape over both rails on a one foot section in the middle.  The decoder requires rechargeable batteries so I used 3 NiMH portable telephone batteries, each rated at 3.6 volts 320 mAh.  A switch was installed in series with the batteries so that they could be turned on and off, and a pair of 5.6 volt zener diodes were installed in series across the batteries to prevent excessive charging voltage.  Due to the nature of the test and the small investment in batteries, no current regulation was used.

The first test consisted of running the locomotive along the bare brass track, over the tape insulated section, and back onto the bare brass.  This simple test created a sensation among experienced model railroaders, particularly as the locomotive ran equally smoothly and at the same speed both on and off the tape.  The concept of battery backup is simple, but to see it operating so smoothly is amazing, even to those of us in the electronics field.

The second test was to run the locomotive back onto the tape, this time stopping, reversing, starting, stopping, again reversing, all while on the tape, then accelerating quickly off the tape.  All of the DCC users and many of the astute dc users immediately realized for themselves the significance of this second test - that the DCC signals were being picked up right through the tape.

Most of the observers accepted that technology had solved the age-old problem of dirty track.  A few wanted to know how this was possible.  These were mostly technical people in the electronics field, but included a nuclear physicist and a retired university professor.

Not surprisingly, a number of members of the general public who had come to the show to see some trains run saw nothing new or exciting in these tests - all they saw was a knob being turned and a locomotive running as a result.

There were some very interesting questions raised.  The most common were what about H0 and what about N scale.  (The answer was that both the Lenz Gold JST for H0 and the Lenz Gold Mini for N scale work with capacitors to create "electronic flywheels" to help the locomotives get over the dirty spots.)  Other questions included how big should the batteries be (The answer was that it depends on the ratio between dirty and clean track.  With mostly clean track, the battery can be small, just big enough to meet the current demand.  If the track were 100% dirty, then you would need a battery big enough to meet the ampere hour demand.)  And a related question was how much of the track could be covered with tape and the locomotive still work (the answer would seem to be ALL OF IT.)

The answers to the last two questions lead me to speculate on a whole new way of operating trains, one perhaps not even foreseen by Lenz themselves.  That would be to purposely prevent the decoder from picking any power from the track by isolating the decoder from the wheels with capacitors.  This would force the locomotive to rely completely on the batteries for power, just as battery powered trains already do.  The downside of this would be having to charge and maintain batteries.  The advantage of this would be that locomotives could be fitted with sophisticated DCC decoders at a fraction of the cost of radio receivers plus auxiliary function control modules.  Operation would not require track cleaning, which many find a nuisance.  And as a bonus, this type of operation would not require any DCC boosters as the power would be supplied by batteries, not by the rails.  The control for a typical backyard railway could then be a low cost, introductory level DCC command station/throttle/low lever booster unit such as a Zephyr or a Bachmann E-Z Command.  I am sure this would have no appeal on huge layouts where you must walk along with your train, but would be ideal for the average, suburban backyard sized layout that can be controlled from the patio while sipping a cool one and listening to the burgers sizzle.  Please keep in mind that this mode of operation is only speculation at this time.  It will be a couple of months before the snow is gone from my outdoor layout and I can start on testing this concept.

Seeing this is a Soundtraxx Sierra thread, maybe Mathew (0V) will let me talk about my experiences with Sierra.

In track powered dc steam locomotives, the wiring is simple and you can have the all important synchronized cuff.  But whistle/horn operation is awkward - you have to change speed to blow the whistle.  And then the best you can do is blow for a crossing.  I seem to remember that if you left the throttle up a little bit, you could have an idle sound on diesels without the locomotive moving and without the sound system automatically shutting down.  Biggest problem I found is that you have to run locomotives, particularly geared locomotives, unrealistically fast to keep the battery charged, otherwise run time is limited to an hour or so.

With battery r/c, you have much the same advantages and disadvantages, except the whistle/horn and bell can be operated by push buttons.  This is particularly nice with the whistle/horn because you can blow any pattern you like.  However, for reasons I don't understand, you lose the idle sound on diesels.  Perhaps the minimum motor pulse width is wide enough to move the locomotive and the only thing below that is no pulse, so the decoder shuts down. 

With DCC, you have constant track voltage that lets you charge the Sierra battery, giving an unlimited run time (very important to me, maybe not so important to you.)  And you can apply a small enough pulse to the motor to keep a diesel sound system idling indeffinitely, or at least until the hydro company decides to have a power outage.  And like the battery r/c setup, you have the option of operating the horn/whistle and bell with push buttons.  The downside is that the Sierra's "motor inputs" must be isolated from the decoders "motor outputs" if you want to use track powered battery charging.

And one big plus for the Sierra is that programming controls are built right in, so you or your installer can program it the way you like it, independent of your power source.

I used CorelDRAW for that one.  If you use Widows Paint, you can do something similar, but a scan of a pencil sketch works too.

I think a mechanically synchronized (triggered) chuff is highly desirable no matter how we power our trains.  To me, nothing shatters the illusion as quickly as a motionless locomotive chuffing away.   I am glad the Sierra will be with us for some time to come.

Atlanticcentral, you are welcome.  I use Digitrax because of my dealer - he lives in the next province, but he serves me well by mail.  The reason I went with him is because he has been a Digitrax dealer for about as long as there has been a Digitrax.  Everybody starting off in DCC needs a guru.  He is mine.

Turnouts of all manufacture are affected by things like
- wheels out of gauge
- bad flange profiles (paticularly on older rolling stock)
- couplers (side sprung horn-hooks were really bad if truck mounted.)
- tracks within the turnout out of gauge
- poor alignment between points (movable rails) and fixed rails
- dirt preventing proper movement of points
- incorrect gauge (outside to outside) between guard rails and points

And other things that other people may add to the list.
Most of them can be checked with an NMRA H0 track and wheel gauge, and once the problem is found, the solution is usally obvious and easy. 

When it comes to trackwork, that gauge is the most important tool in my tool box.  If I forget my hammer, I can always use a rock.  If I forget my screw driver, I can always use a butter knife.  But if I forget my track and wheel gauge, then I might as well leave the rest of my tools at home because I will never know what needs fixing.

A sketch of the track plan would really help.  Do I see it right that the original smaller railroad is connected to the larger railroad by the tail track of a wye, so that you approach the smaller railroad along a single track, then have the option of running around the smaller railroad in either direction?  Sort of like this:



I am sure your layouts are not egg shaped as shown and I realize that the smaller one has an up and over along with a couple of sputs.  But is the wye arrangement basically the way you have it?

Good point, atlanticcentral.  The fellows who have 100 plus locomotives and a large investment in block control (both dollar wise and time wise) are daunted by the dollars and time to change.  They have my sympathies.  I went from computer block control, which had taken 14 years to develop, install and program, to DCC, but not without a tear in my eye.  And after close to a decade, I am still converting locomotives.

My pleasure to help.

Two ways -
(1) use an auto reverser for the tail track.
(2) Depending on the type of turnouts you use, you can use either auxilliary contacts on the switch machine or and Atlas Snap Relay connected in parallel with the switch machine of the tail track turnout.  These contacts need to be DPDT (the Snap Relay is DPDT) with the center two connected to the tail track and the end contacts connected to the tracks approaching the tail track turnout.  Then the polarity of one track or the other with be automatically selected depending on which way the turnout is set.

Note that in both cases that both rails of both approach tracks need to be gapped at or near the tail track turnout.

This is very similar to the reverse loop shown at the link below, with the track to the left of the turnout being the tail track.

http://members.shaw.ca/sask.rail/dcc/loop/loop.html

Note - if your wye is not a simple one, i.e. the tail track is not dead ended but connects back into the railroad somewhere else, then only the auto reverser will work.  And it will require another set of gaps at the next turnout.

The king of the flexible wires (and perhaps what Rivarossi used) is tinsel wire.  It IS a piece of string, with a very thin, flat conductor spiralled around it.  Current rating is low - it probably would not stand up to a locomotive to tender short driven by a 5 amp DCC booster, but it could be used for the other four wires. 

Chucknlead, that is surprising to hear.  I find that even rank beginners in the model railroad classes I teach, even the guys who still refer to a locomotive as a "train," have heard of DCC.  Perhaps this is because our local hobby shop sells four brands - Bachmann, Atlas, MRC and Digitrax.

TOC, could you please go back and reread my posting just above your latest one?  I am not sure what your posting below it has to do with the acceptable range of supply voltages for large scale locomotives.

Perhaps if I restate my posting as a single question:

If a supply voltage ranging from 18 down to 12 volts is good enough to run a Big Hauler locomotive,

And a supply voltage ranging from 14.4 down to 10.8 volts is good enough to run a battery r/c locomotive,

Then why is a supply voltage ranging from 17.8 down to 15.5 volts not good enough for running a DCC locomotive?

If you would be kind enough to answer this one simple question for us, we could get on to more interesting things.