Why Three Rails?

It goes back to the days when insulation wasn't as mechanically strong, and they had live driving wheels.

Other 3-rail systems used DC, like Hornby.

Technically these are stud-contact not 3-rail.

There are raised studs in the cross-ties that serve the role of a third rail, but regular 3rd rail locomotives can't use this track because the pickup shoes will foul the studs. Pickup has to be from something like a ski that rides across several studs at a time.

Three-rail systems have a "hot" center rail and two "return" outside rails. Power is AC and, yes, it makes setting up the track easier since there is no way to connect the "hot" to the "return".

AC, but two rail such that track setup is the same as in HO

Marklin three rail is AC, same as Lionel et.al., but the center rail is modified into studs that stick up from the ties. Marklin locomotives have a skid that slides along the studs as the train moves. Marklin makes very expensive, high quality toy trains, but they are toy trains built to approximately 3.5mm scale, not scale models. Marklin trains are very substandard in the areas of scale fidelity and accurate details, especially on the North American stuff. Basically, Marklin is made for those who operate their model railway and their slot car track in the same manner. (Thanks to G.P. for that analogy)

CH

R> A friend at work was asking me about electric trains. He had memories R> of the Lionel trains his Dad had set up for him. And had seen an R> advertisement for a Trix Big Boy 4-8-8-4, for about $700. He had R> assumed that it was the scale he was familiar with. But the Trix model R> is HO, not O scale. R> R> My friend was not familiar with model railroads and had lots of R> questions. I explained to him the various scales, "O" "HO" "N" etc, R> but then came a question I could not answer. R> R> Why are there three rail systems? The only thing I could come up with R> is the way it is possible to make a reverse loop easily with three R> rail, but it is more compicated with two rail.

Maybe. Only Lionel knows for sure *why* they opted for three rails. This might have been one reason. Also, Lionel's old style track used

*metal* ties, so there would have been issues insulating rails from the ties that could have been a problem with two rails (although I believe American Flyer's 2-rail S guage also used metal ties similar to the Lionel, so it can't be too hard a problem).

R> R> And I think, Lionel "O" and "O27" are AC. But I don't know if this is R> the reason for three rails.

No, should not matter.

R> R> I grew up with Lionel O27, and never gave it another thought, having R> moved onto HO long ago. R> R> BTW what is the power system for American Flyer trains?

American Flyer are AC, much like the old Lionel O27, but two rail S gauge.

R> R> And not to complicate things too much, does anyone know about Marklin R> three rail systems? R> R> _Thank You_ group for your answers. R> R> Best Regards, R> R> Robert R>

\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu

|| snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

3-rail is not limited to AC though. I am using 3-rail Marklin C-track with a DCC signal. Of course this requires putting a DCC decoder in a 3-rail locomotive, but that has not been a problem so far. This set up allows me to use the flexibility of DCC yet still use the simplicity of 3-rail, the benefits of which are IMHO, no reversing schemes, more connection with the track for better signals and simpler wiring.

Steve

Am Sun, 20 Feb 2005 23:30:38 GMT schrieb Captain Handbrake :

Aha! As I understand your knowledge of Maerklin ist really deep.... :-))

only an "oversized" BigBoy...).... ;-)

Micha

As others have said, three rails eliminate polarity problems from reverse loops in layouts, and avoid the need to insulate one wheel from the axle. To add to that, recall that Lionel's first trains were 2-rail 2 7/8" gauge (with strap rails pressed into the slots of wooden ties), and that 3 rail standard gauge came later and with the preassembled metal ties was a much superior product. Ron Hollander, in his history of the Lionel Co., explains that in the 1900's and 19 teens, Lionel sold mostly in the NY City area where people were used to 3 rails on the subways and main line commuter services. Note too that before WWII American Flyer made standard gauge and O gauge three rail trains compatible wth the Lionel track systems. And the predominate pre-war scale model RRs were 3-rail (albeit outside 3rd rail) O systems. And lastly, one other benefit of the 3 rail systems was the ability to use track circuits similar to the prototype to activate accessories, which was (and still is) much more effective than the later gravity switches Lionel used.

Regarding the use of AC, remember that in the early years of the 20th century, many homes were not yet wired for electricity, or had DC power systems. An AC type "universal" motor can be run on either AC or DC power. Early catalogs describe systems for dropping line DC voltage for use on trains, or running trains on batteries, in addition to describing virtues of transformers. DC motors were either wound field types which required adjunct rectifiers which were expensive, large, and inefficient, or permag types which were not very efficient as the modern ALNICO type magnet materials were not developed until (I believe) well into the 1930's.

Prewar - all AC (or DC as above); post war primarily AC, but Flyer also offered many of its locos in special DC versions in the period around the early 1950's. Gary Q

I am a little puzzled on the AC vs DC thing. My brother had a Lionel 3 rail O-scale train set (all plastic bodies, maybe from the 60s or

70s???). It was DC, I used to run some of the HO locos around his set between the middle and outside rail (yes the HO locos wheels were slightly under gauge).

At various times Lionel tried marketing DC sets, usually in the low end of their product line.

Also note that many of the OLDER lionel trains, while INTENDED for AC operation, would also run on DC (with different power supplies). This is not true of the newer 'electronic' versions.

Dan Mitchell ============

Also, 027 is DC, at least as far as Lionel engines go. You can of course hook up an AC transformer and run AC engines on 027 track. This is something that can catch the unwary on eBay.

Robert wrote:

The VAST majority of Lionel O-27 locos are AC, not DC, and always have been.

Only some low-end sets were made as DC, accompanied with an appropriate DC power pack that would not operate the regular AC locos. These DC sets were NON-standard, even by Lionel's standards. This can be VERY confusing to anyone buying a set at a discount store or flea market, and not understanding what they are getting.

When I worked at a hobby shop, for many years, people were always bringing in the DC locos (that they got somewhere else) and trying to get them 'fixed' so they would operate with their other Lionel AC equipment. We sold both, but were always careful to let customers know what they were buying if the wanted a Lionel DC set.

Dan Mitchell ============

After the original Lionel Co. was sold to the Fundimensions division of General Mills in 1970, some extremely cheap sets were made with very simple plastic parts, and powered by small permanent magnet DC motors. They did used regular O-27 track. I personally think these toys were unworthy of the Lionel name, are best forgotten, and thus failed to mention them in my prior response.

Lionel uses universal motors that have a wound field winding rather than a magnet like the DC motors use. As such, Lionel can run on either AC or DC. Back when Lionel got started, DC was a lot harder than now to generate as silicon diodes weren't around and the selenium rectifiers was the standard way of getting DC and they weren't as reliable or nice as the modern rectifiers.

-- Why isn't there an Ozone Hole at the NORTH Pole?

O-27 is AC , not DC. DC is used with all of the Lionel stuff to do the reversing of the loco.

-- Why isn't there an Ozone Hole at the NORTH Pole?

No. Reversing was accomplished by interrupting the current. Low voltage DC was used to activate the whistles. Exception to prove the rule - there was a special two train set offered around 1940 where one train was reversed the normal way and the other by DC using a modified whistle relay. This was called "Magic Electrol". Gary Q

"Back when Lionel got started" ...

"Back When" ... there were LOTS of places, whole communities, especially in rural places, that had DC for their community power distribution! As a kid, in the 1950's, I can recall visiting places that had 50 hz for power, and lots of farms were still DC. Lots of farms were self-powerd , via windmills or whatever, and used DC at all sorts of voltages.

Universal 60 hz 115 VAC, as we nearly all have now (in N.A. at least), is a creature of the post W.W.II era. Lionel was going strong long before then.

Thus it made sense to market a train that could run on either AC or DC, as most earlier Lionel trains could. Lots of them used to be run on battery power (not on transformers), as were most "O" scale 2-rail model trains of the period.

*IF* you had AC, you could use the available transformers, and avoid messing with the batteries.

But THAT has NOTHING to do with the 2-rail/3-rail issue, as either track will work just fine on either power. The electrical issues remain exactly the same for AC or DC on either type track.

Dan Mitchell ============

That's right. The earlier Lionel stuff would run on pure DC, if desired.

The electric whistles in the locos were probably the first things thet

*REQUIRED* AC. Even then, the train would still RUN on DC, but you couldn't blow the whistle.

They occasionally tried all sorts of things. The peak of this was the post W.W.II set that used various AC frequencies to control the trian. It was a primative version of "Command Control", and used tuned resonant relays to select between the various control frequencies. It did work, but NOT very well. The average person, including Lionel repair personnel, couldn't keep the things working. The sets were soon pulled off the market. These sets are a big collector's item these days.

Dan Mitchell ============

Not just rural and not that long ago!! See the following item found along with a discussion of the Thomas Edison vs. Nikolai Tesla (with George Westinghouse backing) battle about of the merits of DC vs. AC power distribution at

"New York City's electric utility company, Consolidated Edison, continued to supply DC current to customers who had adopted it through the twentieth century. In January, 2005, Consolidated Edison announced that it would cut off DC service to its remaining 1600 customers (all in Manhattan) by the end of the year."

generate as

Actually, selenium rectifiers were a great leap forward compared to the copper oxide rectifiers which preceded them and which only the telephone company could afford. They weren't very good rectifiers and the telephone company didn't like them, but used them because they needed DC and the only other ways to get DC pre-WW2 were from primary batteries and motor-generator sets.

Bob Netzlof

DC power is still in use in many LA movie studios, as lamps operated on DC last longer and are quieter in use than lamps on AC.