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More on Putting the Blobs on a Diet

Thoughts, observations and other stuff that didn't fit into the "One Reader's Opinion" Model Railroader article from September 1998

By Craig Bisgeier

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Thanks for your interest in my article on “Putting the blobs on a diet” in the September Model Railroader. It’s really hard to try and get across a concept like this in just 800 or so words, so I thought I’d try and expound on a few of the ideas presented in a location where page space isn’t at such a premium. If you don’t have the original article copies can be obtained from Kalmbach Publishing for reasonable rates by writing to I may be able to post the text here in the future, if Kalmbach will allow it I will do so.


Let me start off by shaking you out of your comfort zone, to try and take you away from conventional thinking for a little while. Try to forget the blob for a moment. Forget the blob is a device so common to model railroad layout design it is accepted without any critical thought by nearly everyone who has ever designed a layout. As of now you have never heard of a blob, never seen one used. Following me? Good.

Assuming your focus is to model a railroad (rather than simply build a place to run model trains), your goal should be to represent the setting and route as realistically as possible, within reason. When you go trackside to visit a real prototype railroad, what will you see? Generally, You’ll see tracks that reach off in one direction and continue in another, usually in nearly opposite directions. Here and there you see curves, but they are generally very broad, compared to what we are used to.

It is a very rare occurrence when curves are so can be seen to actually bring the track back around in the direction they came. Almost always, this occurs in mountainous terrain as a trick to cross a wide valley without having to build a long bridge, or to gain extra distance trying to climb steep grades. Because of the spectacular view offered, locations like Horseshoe Curve near Altoona, PA are popular among railfans. But as I said, this is a very rare feature. It is extremely rare in areas where the land is relatively flat.

The reason for this goes back to the basic purpose of the railroad. Put simply, it is a transportation system designed to carry good and passengers from one point to another. The railroad’s only interest is to get the trains from here to there as quickly and efficiently as possible, and track that curves back on itself without a very good reason is in conflict with that simple goal. Therefore it is something you rarely if ever see in real life.

Still with me? We’ve established, then, the railroad is a linear entity with curves where necessary to avoid inconvenient terrain features or provide access to locations, which may be out of the direct path. However as we all know, model railroads aren’t build in the basements of spaghetti factories, four hundred feet long and four feet wide. We have square or rectangular spaces to build in most of the time, and if we want to use the space to its best advantage, part of the railroad needs to occupy the center of the room.

Here’s where the problem starts: When you extend the model railroad into the middle of the room, sooner or later you either have to bring it back again the way it came or you have to run it to another wall, creating and isolated space reachable only by duckunder. (Since the latter option is even worse than the former, let’s ignore it for now.) Obviously this requires a loop of some sort. But (alarms should be going off in your head wildly here) as we’ve just established, railroads simply don’t use sharp loops that turn back on themselves! Now that you know what to look for, and are actually thinking about it, I bet you are having the same reaction I did when I first put it together -- Ugh!

Welcome to the rock and the hard place. You can’t just leave the track hanging in midair, right? Your senses are now screaming at you that this is WRONG! But you have to do something to keep the railroad going, so you put in the blob anyway. You do what you can to minimize the damage -- wide radius curves, so the trains don’t look like accordions as they pass around, but that makes the footprint of the blob bigger and it becomes even more obvious. You try to turn the tables, to use this big honking space hanging there to highlight a special layout feature, like (oh god, not another one) a Curved Trestle! Please trust me, it doesn’t work and it is obvious to everyone who looks at it that you had no idea what else to do with it. The end result is almost always the same: Horrible, big, misshapen -- blobs! -- That, once you think about it, are eyesores that stick out into your layout room like sore thumbs, taking up huge amounts of floor space. Why do we do this to ourselves?

Because it has always been done that way...

From a strictly engineering point of view, it makes perfect sense to create a loop at the end of a section of layout that springs forth from the wall into the room. Certainly the first model railroaders must have thought so, having evolved only recently from simple ovals and circles of track on the floor or mother’s dining room table. As they brought the tracks around the walls of the room, it seems likely they simply extended the tight, cramped tabletop loop they already were used to into the center of the room and ran straight tracks to it from the wall.

Back then there was little concept of layout design beyond simply getting as much track as possible into the available space, and this had to have been a hugely important development. Little to no thought was expended on whether it was a prototypical practice or not -- in an era where good layout design still meant trains looping around the layout over and over again, with tracks crossing one another every which way, it simply wasn’t important.

But a funny thing has happened. As we have evolved, raised our consciousness about layout design, begun emphasizing fidelity to prototype, promoted “Sincere” layout planning (trains only pass through a scene once) and other advanced concepts like staging, we have never revisited the simple and venerable turnback loop, or Blob as John Armstrong named it. Through the 1950’s when popular design practices produced layouts with miles of hidden track, the blob persisted. Even as cutting-edge modelers pressed the edge and built layouts that more closely looked and operated like the prototype, the Blob was still included without a thought. What are we thinking?

It seems obvious we aren’t thinking, at least about the Blob. Surely if we were, something better would have been developed by now. But layout designers from beginner to expert continue to use the blob. Minimum visible radius curves are often based on what size blob we can fit into the trackplan and still get the trains around the layout. Its use has evolved to where it has become a given, a constant, the only variable in its execution being how large or small to make it.

Stop the Insanity!

It is amazing to me that I’d never heard anyone mention a hidden blob before. I’m sure it must have occurred to someone, somewhere before Jerry Bellina did it. One of the most creative and innovative guys I know, he started building a mushroom layout years before the idea was popularized in the Layout Design Journal or Model Railroader. Jerry’s reason for hiding his blobs was to solve a problem different from mine. His mushroom layout is built in a square room, about 32’ x 32’, and it has short peninsulas and narrow aisles. Because of the short distances, operators using his Rail-Lynx walkaround infrared throttles would stand in the main aisle and watch their trains snake around the inside between the blobs, and create human traffic problems in the aisles.

To clear traffic from the main aisles and force the operators to step into the space between the blobs, Jerry hung Masonite view blocks up around the ends of his blobs. Once the operators couldn’t see their trains from the end of the blob anymore, they walked in between them and cleared the outside aisle. So Jerry’s solution to the traffic problem was successful, but we shortly found there were additional benefits as well.

The most unexpected and useful benefit came from losing sight of your train as you walked from one side to the other around the view block. We found that psychologically the distance between the towns on either side of the blob seemed greater, that it felt a greater distance had been traveled when you got to the other side. It seems silly, but many operators noticed it right away. As your train departed the visible portion of side one, you saw it disappear around a curve and duck out of sight. This is a lot like what you see standing trackside on the prototype, where the train eventually disappears around a corner and is gone from sight.

When you walked around to side two, the train was already arriving in a scene that was different, and you’d traveled a bit from one place to another without the train in sight. The effect is very much like a common device in movies or television called the dissolve or wipe, where the location of the picture on the screen changes and we know some period of time in the story has passed, even though it is really just moments later. It is a difficult effect to describe, but surprisingly it works. The three factor the operator changing locations physically while the train is out of sight seems to be the key, as there is no similar effect observed watching a train duck into a tunnel and out again while standing in the same place.

The second unexpected benefit came from suppressing the attention a blob normally demands. As previously discussed, most blobs are eyesores you can’t avoid, and attract more attention than they deserve. Trains look lousy as they skirt the edge, riding on obviously sharp curves. (All right, I guess you know the litany by now.) But we never expected that doing something as simple as placing a view block around the end would make such a difference. Once the view block was up and we got used to it, the blob all but DISAPPEARED. Like the fascia of the railroad, which you hardly notice after a few minutes, the Blob was completely de-emphasized. Operators walk around it without noticing or seeing it.

OK, I admit it is really jarring the first time you run into it, I’ve seen visitors at Jerry’s have some interesting reactions to it. But after the novelty wears off it is quickly accepted as a part of the railroad environment. From the inside, the view block is painted as a regular skyboard, with trees, hills, clouds, etc. On the outside the view block is cut flush to and matched to the fascia edge. The fascia color is continued onto the view block so it fades into the background. And since the track loop is no longer right in front of you skirting the front edge, it can’t dominate the scene the way it usually does. Inside the block, it actually looks pretty good as it bends off into the distance and the track disappears behind a building or stand of trees.

The third unexpected benefit was at the same time the most understated and interesting from a design perspective. Once the blob was hidden and the large, obvious turnback loops of track de-emphasized, the railroad took on a more linear appearance. All of a sudden in a subtle way, the railroad seemed more like it was actually going somewhere else, continuing in a single direction, rather than appearing to go back the way it came. Most operators didn’t notice it but for a vague satisfaction with the railroad design. When asked if the lack of visible turnback loops enhanced the experience, many agreed it helped.

So in the end, we found that hiding the blob provided huge benefits beyond the original purpose: Greater apparent mainline length, de-emphasis of a troublesome layout design element, and a design trick reinforcing the linear nature of the prototype in the model. By itself, these results make the technique a success, and I would highly recommend then to anyone to try. But I felt there was still more room for improvement.

Sweatin’ to the Oldies

Jerry’s enclosed blobs worked great, but behind them still lurked the evil Blob. It might have been well hidden, but all you had to do was look down to the floor to see the real story. His minimum radius curves still created a large 6’ footprint, which took up a lot of aisle space. Now, since Jerry’s layout is a mushroom and the inside of the lower blob is the aisle way for the upper level, it worked for him and he was happy with this. But I had a different agenda. I wanted to be rid of the blob completely. 

Many layout designers use two minimum radius standards:   Visible and non-visible.  Visible minimum radius is usually an aesthetic consideration, having to do with what the designer feels is the smallest curve he can use and still have the trains look all right on the curve.  The non-visible minimum radius is usually tighter, closer to the physical limits the railcars can navigate without derailing because of coupler swing and truck swivel limitations. 

Once you've decided to close in the end of the blob, you no longer have the obligation to construct the blob to fit your visible minimum radius.   Because you can't see the track in the deepest part of the loop very well, you now have the opportunity to hide the middle of the loop with scenery and cut that radius back, significantly reducing the size of the blob.  Of course, you can see the approaches into and out of the curve, so it is necessary to use spiral easements into and out of the minimum curve.  When completed, the loop at the end of the blob should look more parabolic than circular.

The spiral easements are an important part of the key.  They allow you to use the tightest radius you can safely manage while reducing the coupler swing between cars to the minimum.  On curves that start abruptly from tangent track, the car ends swing out dramatically at the transition point.  This can cause longer cars to literally drag other cars right off the tracks.  A gradual spiral into a curve, though, minimizes the coupler swing problem and allows much tighter curves to be used than might normally be feasible.

Also because the curve is now hidden, you can dispense with any foreground scenery you might have otherwise included, and place the track at the edge of the blob with only enough space to clear the sky board edge.  This further shrinks the size of the blob you have to build.

All of these things contribute to the goal of making the blob as small as possible.  And when you do that, you open your layout space up to new possibilities.  Whether you use the extra space to add aisle width, or even cheat enough room to add an extra peninsula, it gives you new options you ordinarily would not have.

"Uhhh... Well... Mom's up in the tree..." 

There had to be a down side, right?  As with any design element that pushes the limits, there are trade-offs.  First, if you run long trains on your layout, you'll want to consider a wider radius than your theoretical minimum.  Long trains produce significant drawbar forces between each railcar, and tight curves can contribute to a phenomenon called stringlining, where the tension pulls the cars right off the inside of the curve.  Wider radius curves often reduce the stringlining problem by distributing the tension over a wider area, given the same train weight.  More weight in the cars may help but that will reduce the number of cars your locomotives can pull, which also happens to lessen the risk.

Second, modern railcar models are usually much longer than their 1940's and 50's counterparts, or my own 1890's cars which are tiny by comparison.   Even with smooth easements, the minimum radius for 50-60 foot average freight cars is going to be wider than that of the average 40' boxcar.  And if you run full-length 85' passenger cars in almost any era, you'll have to consider them as well when choosing a non-visible minimum radius. 

Third, grades are affected by curves.  If your skinny blob occurs on a section of your layout that will contain a significant grade, you may have to reduce or even out the grade through the tight curve or you'll have problems getting heavy trains past that point.  Curves, especially tight ones, on grades have the effect of increasing the apparent grade through the area.  Inside a skinny blob is not a good place to locate your ruling grade.

Happy trails to you

Well, that's it.  I hope you all enjoyed the article and this discussion.  I'd really like to hear your opinions on this idea, so please E-mail me at and let me know what you think.  Thanks for listening!

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