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13 Radius | Susquehanna S Gaugers
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November 13, 1999


Mr. Don Thompson
S Helper Service
2 Roberts Road
New Brunswick, NJ 08901-1621

Subject: S Gauge Rolling Stock For Small Diameter Curves


Consider (someday) maybe marketing a small S gauge hi-rail engine (and possibly cars) that can operate on small diameter track curves (about 24" diameter)

Action Requested:

Please file this in your 'Suggestions' folder.

This is one of those suggestions that you might disagree with. Even if you don't disagree, this may not be economically feasible. But this track diameter topic is something that I am enough agitated about, that I am writing you this note. 

1. The "Problem"

In my opinion, one of the "weak spots" of S gauge is availability of good running rolling stock, that can operate on small diameter curves. With currently available S-Trax, the smallest circle you can make is about 38" diameter.

In other words, S gauge seems to require a relatively large turning circle, compared with some of the other scales.

For example, you can operate a larger O gauge train on a 30" diameter curve that is about 8 inches smaller. You can operate a much larger G scale train on a 48" diameter curve that is only about 10" larger.


2. Why Would Anyone In Their Right Mind Want To Operate On A 24" Diameter Loop ?

Two possible reasons:
  1. Displays at train shows, to fit the standard 30" wide table
  2. Home layouts in small areas


3. Displays At Train Shows

One of my interests is in constructing small displays for train shows. It seems like it would be handy to be able to have equipment that would operate on a track of about 24" diameter. Then you could construct a layout that would fit on the standard 30" wide conference table that they usually use at train shows.

Figure 1 below shows how a simple oval could fit on the standard 30" wide table.

Figure 1 -- Display Layout On A 30" Wide Table


Figure 2 below shows how the ends of the layout could be covered with scenery, so the minimum VISIBLE radius would be fairly large.

Figure 2 -- Same Layout, But With Scenery Hiding Sharp Curves


4. Home Layouts In Small Areas

Some people may be "forced down" to HO or N scale or point to point layouts, because they don't have enough space for the "standard" 38 inch diameter turning circle required for S gauge.

If they could turn in a 24" diameter, this might give them a chance to use S gauge in smaller areas, where the standard 38" diameter will not fit.


5. What Size Would An S Gauge Track Circle Be, If It Was Proportional To G or O Scale ?

G SCALE -- If you examine LGB's G-scale trains, scale 1:22.5, their starter engines, their larger engines like the 2-6-0 Mogul, and their large ALCO diesel; can all negotiate a 48" diameter circle.

If you proportion this diameter to S gauge, an equivalent S gauge diameter would be about 17" diameter [ (22.5/64) x 48" dia. = 16.87 inches dia. ].

O GAUGE -- If you examine Weaver O gauge in hi-rail, a scale length E9 diesel pulling proper length passenger cars seems to be able to go around a 30" diameter circle. If you proportion this diameter to S gauge, an equivalent S gauge diameter would be about 23" [ (48/64) x 30" dia. = 22.5 inches dia. ].

Generally these diesels use power trucks where the motor and drive is all part of the truck, so there are no u-joints that have to bend on the corners. Bachman also does this in HO scale with their GE 44 tonner diesel; each truck has its own motor and gearbox all integral with the truck.

The following Figure 3 shows an O gauge trolley train turning on what I think is a 24" wide module. These traction guys seem to be the experts at getting trains around sharp corners.

Figure 3 -- Sharp Radius Turnaround Loop On A 24" Wide O Gauge Module


6. What Do I Have In Mind For S Gauge

The easiest way to do this would be maybe a small 0-4-0 diesel. If you look at G scale, Aristo Craft made their Little Critter by apparently using the cab portion of their RS3 diesel. Something similar in appearance to this engine could probably be built in S gauge.

If you look at LGB, their little 0-4-0 Stainz steam engine is the "cornerstone" of all their starter sets. An S gauge version of that engine (Americanized) would probably look good and be able to negotiate sharp curves.

COUPLERS -- Possibly some sort of special coupler would be needed. A simple link and pin would probably do the job. The one-piece link could be disguised to look like a pair of knuckle couplers for realistic appearance. (I have observed the battery-powered trains they use inside malls to provide rides for little kids. The trains go around incredibly tight curves, about 8 foot diamter, for a train that has about a 2 foot track gauge. And I notice that they use link and pin.)


7. Other Comments

I was fooling around the other night, with some old American Flyer Pikemaster 30" diameter track. My S Helper SW-9 appeared to be able to negotiate the Pikemaster curves. But I don't think the SW-9 would be very "happy" doing it all day long on a display layout.

Besides that, the Pikemaster track seems poor with respect to electrical connectivity. I had lots of problems just keeping electrical continuity from one section to another.

As I was struggling with this Pikemaster track, I was thinking to myself, "I would sure like to have a loop of my great-running, easy-to-set-up SHS S-Trax, but about 24" diameter; plus a small SHS engine and cars with appropriate couplers, that were designed to negotiate these curves".


8. Why Am I Writing This Letter To Don Thompson ?

Running an S gauge train around a small radius turn is something I plan to work on in the future, if my interest in this subject continues, and I don't die of old age first. However, since you seem to get things accomplished about 100 times faster than I seem to, I thought I should try to arouse your interest in this small radius subject.

Mass producing track for this small diameter may not be possible. But do you think it might be practical to mass produce a small engine, that would just happen to have the capability of negotiating sharp curves ??


9. Other Possiblilities

In my 1996 Scenery Unlimited catalog, I see they have Rex 0-4-0 docksider engines advertised, in scale versions only. If these 0-4-0's are still around, one could probably hand-lay a 24" diameter track, and use one of these engines.

But I really prefer to use hi-rail. (I can hardly see the difference between the hi-rail flanges on my SHS SW9, and scale flanges. Staying hi-rail allows me to operate with the Flyer guys. And hand-laying track is way over my current skill level, plus cumbersome to put up and take down. I've looked at the American Models and Gargraves flex track, but I can't see how it could be bent to a sharp radius without destroying it. )

If you have any ideas for getting a train around a sharp curve like I am talking about, that I apparently have not thought of, please let me know if you get a chance (my email is at the top).

Thanks for listening.


Jim Ingram