Loop Polarized

Loop Polarized

My Lego Train Wont Go Around the Track!!

What is going on when your train won't go around the track? Can you make a lighter train or a different locomotive go around the loop? If so, then you've likely pushed the limits with the heavier train that won't. BrickTrainShop examines these limits to help you pick and choose where to focus your efforts to get your trains moving.

Let's begin with a little perspective; take a look back at most of the 9v line and you will see lightweight train sets with two to four cars, and often the cars did not have bogies. A good example is at the beginning of the line in 1992. The Load N' Haul Railroad (set 4563, profiled in this issue) had three cars, each with only two axles. This tradition continues to the remote controlled Cargo Train Deluxe (set 7898) released in 2006. Another trick you see in the 9v train sets is the fact that they often make use of panels and windows to increase the volume while keeping the weight down (e.g., sets 4559 and 4561). The LEGO train motors and controllers were made for these lightweight trains. The choice made sense since the sets only came with a small oval of track and many kids would not add to it, so the trains would be short and the motors did not need to be powerful.

A notable exception to the trend is the Super Chief locomotive and cars (sets 10020, 10022, 10025) released in 2002. In comparison to the 9v trains that came before them, they weigh a ton. After these sets came out we set up a small layout in the corner of the warehouse. While the floors looked level, the Super Chief made it clear that they were not: uphill slow and downhill fast. To pull five cars and two locomotives we needed two motors and they seemed to be straining at their limits.

Since those days we've gone on to pull very long and heavy trains using the 9v system. Our personal record is 51 bogied cars and four locomotives over uneven track at NMRA 2007. There are many challenges to running such long trains, the first of which is simply having enough cars and track to do it. But along the way we had to overcome many other challenges that you'll likely encounter with just six or seven cars. In fact at home, we can only comfortably run trains with 6 or 7 cars.

COLORING WITHIN THE LINES

No matter what the size of the layout is, weight will always be among your top concerns. If your surface is even a little uneven, as it was back in my apartment, the motors will have to pull the weight of the train uphill. So generally speaking, the lighter you can make the train cars, the happier your motors will be. Even if you are able to find a completely level surface, weight still comes in to play by increasing friction and inertia, which we will get to in a moment (no pun intended). Keeping the weight down is always a good starting point. But generally, the more realism you strive for, the heavier your cars will be. As a result, we personally prefer 6 wide cars for operational reasons, but we drool at the detail you can put into 8 wide. Sometimes you can figure out tricks that give you the realism with little or no weight penalty; it just becomes one more factor in your designing process. Some of my first MOCs were boxcars, and as a result of my linear thought process the sides wound up being composed of alternating rows of plates and bricks. Needless to say, the density of plates is higher than bricks and much higher than panels, so these original cars weigh a lot. Later, when we wanted a few more boxcars, we redid the design, and built the walls out of panels. The new cars are about two-thirds the weight of the originals, but look virtually identical from the outside. While balancing aesthetics, weight, and functionality, it is hard to beat the train base for its ratio between weight and longitudinal strength. Friction increases with weight and it crops up in several locations on a LEGO train - most importantly the wheel-sets, and secondly bogie rotation. Looking through the Lugnet archives, we clearly were not the only
one having problems with the weight of the Super Chief cars. The wheel-sets (part 2878) are designed to have a needle bearing, riding only on the points at the end of the axle and thereby minimizing the friction surface. In a discussion started by Reinhard "Ben" Beneke, various AFOLs quickly found a design flaw in the wheel holder. Apparently at some point a third party manufacturer of the train wheel holder changed the design without telling LEGO, and as a result, the wheel flange would rub at the 10 o'clock and 2 o'clock positions. Older versions of the wheel holder were measured to be 0.9 mm thick, but by 2002 the thickness had grown to 1.1 mm and thesethicker holders were the source of the problem. Reportedly
the design problem has been fixed, but even in a brand new LEGO set a given brick may have been manufactured many years ago.

As already evident, the train wheel-set has evolved since 1992 in small but important ways. Another big change came in 2006. Prior to that year, a metal axle passed through the plastic wheels and provided the needle in the needle bearing. So the exact position of the wheels on the axle was variable. With these older wheels you may have to adjust the spacing to make sure the wheels do not rub on the wheel holder when they spin. If you notice any problems, you may also want to check the wheel spacing to make sure the wheel-set rides well on the track, particularly if your layout includes switches or crossovers. The easiest way to check is to simply put the wheel-set on the most restrictive type of track you have, i.e., crossovers and switches if you have them, otherwise, straight
track is fine. Starting in 2006, LEGO eliminated the "floating wheels" on the axle. Now the metal axle stops at the backside of the wheel and the needle is molded into the plastic on the front of the wheel. This change should eliminate the positioning problems on the axle, but the plastic on plastic bearing will likely have different performance over its lifetime than the old style metal on plastic. Whether you have old or new wheel-sets, inevitably the needle bearing will wear away the plastic in the wheel holder. As this wear-and-tear occurs, the wheel flanges are more likely to start rubbing on the wheel holder. So every now and then flip your cars over, give each wheel-set a spin to see how long they keep spinning. A new good wheel-set will continue spinning for up to 10 sec. But even after a little use the duration of spin on a good wheel-set will drop to a few seconds. If you get almost no residual spin, then you know it is time to repair or replace that wheel-set. And of course keep an ear out for rubbing sounds that might be easily fixed by repositioning the wheels. If you do have a sluggish wheel-set, don't throw it away. As of this writing, you can purchase individual black wheel holders in the United States from the on-line Pick-A-Brick. But even if you don't do anything to a sluggish wheelset, you can always use it under cars in a shorter train where friction is less likely to be a limiting factor, for static displays under a car that you don't run, or even detailing as train parts around the shop building or payload on a flatcar. Some builders do away with the wheel holder and build trucks that are more aesthetically appropriate for the given car or locomotive. From everything I've read and seen first hand about such custom trucks, the friction is higher than the LEGO wheel-sets. I've found that a simple bogie consisting of two train wheel-sets, a 2x6 plate, a bogie plate, and buffer is hard to beat for longitudinal strength (though its use may mean putting function above form). But experiment and see what works best for you. Returning to the entire train car, curves slow LEGO trains down just like they slow real trains down. There are two forces acting on a train car in a curve, the first being momentum trying to force the train car straight ahead, pressing against the outside rail that is forcing the car in a new direction. The second force being the friction on the bogie plates as they rotate. In my nonscientific experiments I can't say which of these forces dominates, but both appear to contribute. Aside from making your trains lighter, there is little you can do about momentum, since you have to turn sometime. In fact, at times the momentum will help your motors past dirty spots in the track. For reducing the impact of the bogie plate friction, you want the contact between the rotating truck and the car body to be as smooth as possible, e.g., using the bogie plate (part 4092) or tiles for your contact. Based on my experiences we've found that LEGO trains slow more in "S"-
curves than they would in an equal number of curve sections all bending in one direction. Since LEGO track has fixed radius curves, this rotational friction only comes at the junction between curve track and straight track, or curve track in opposing directions. Reducing the number of these transitions will also reduce the drag. For both momentum and bogie plate friction, you can reduce the impact of curves on your train simply by reducing the number of curves your train might be in at any given moment, spacing the curves far apart, with long straight-aways in between. If you think your track layout is causing significant slow downs, a good rule of thumb for shorter trains is to never have the angle between the front and rear of the train exceed 180 degrees at any time, and for longer (heavier) trains, try to get it down to 90 degrees. If you suspect weight is dragging your train down, try to make sure you are always pulling the train from the front rather than pushing from the middle or rear. If the slack is not pulled tight from the front, all of the cars ahead of a pusher motor will wobble, creating extra drag, as they are forced by the rails to go forward. While friction is your enemy in train cars, it can be your friend in the locomotive. Increasing the weight on the motor keeps your wheels from spinning. A purist can use the LEGO train weight (part 73090) or simply build your locomotives as solid as possible. Or if you don't mind concealing non-LEGO within your model, you can use coins or other metal as ballast (here in the US I prefer nickels since copper pennies are more likely to oxidize). But be careful not to over do it, since in the ballast is still weight the motor has to pull.

You may also encounter friction in some unexpected places. The train buffer beam with plow (part 45708) introduced in 2003 has very close clearance with the track. On a perfectly flat layout it is not a problem. But as soon as you encounter uneven track, the bottom of the plow can drag across the top of the rails. At best, it will simply result in a high-pitched squeak, but it can also result in a derailment. After balancing all of the various weights and frictions, once you assemble the train together, perhaps the most critical point in your heavy train is at the rear of the last locomotive. Just like real trains, the longitudinal force on the drawbar is the largest here. Likewise, with a long train, you will need cars and locomotives with sufficient longitudinal strength to withstand such forces. While the front cars need to be strong, you can still use the weaker cars, but they'll have to ride toward the rear of the train, a technique that is also employed by real railroads. One advantage of LEGO trains is the fact that it is so easy to swap out bogies (unless they've been carefully integrated into the model). So you can motorize a few cars and thereby distribute motors throughout a train to reduce the longitudinal forces. For e.g., returning to the Super Chief for a second, I often wondered if the extra space under set 10025 was provided to allow you to insert another motor. In any event, distributing motors throughout the train does add the risk that if the locomotive derails, the rear of the train will continue pushing cars off the track. This fact might not be important if your layout is on the floor but it could be disastrous if your track hugs the edge of a table. In the end, everything comes down to power and the need to get the electric power to the motor to move the train. If you are having problems, first check to make sure there are no breaks in continuity either due to an unplugged wire, switches being lined incorrectly, or two track segments pulled apart. The controller is supposed to put out a fixed voltage, Vcontroller. Each segment of track the current has to travel through before reaching the motor will drop the voltage seen by the motor. There is a miniscule voltage drop along an individual track segment, with a greater loss at the joint between two track segments, and a net resistance per segment, Rtrack_segment. The greater the number of track segments between the controller and train, the greater the power loss. If the voltage at the motor is too small, the motor will not move. After n track segments, the power reaching the motor is roughly: pmotor = Vcontroller 2 ⋅ Rmotor Rmotor + n⋅ Rtrack _ segment ( )2 In other words, power roughly drops inversely proportional with the square of the number of track segments between the motor and power connection to the track, i.e., 1/n2. Be sure to see things from the electrons' perspective. If there is a switch lined in the opposing direction then current can't flow that direction around your loop. A diverging switch next to the power connection can make for a very long distance that the electricity has to travel before reaching the motor; it has to flow all the way around the loop to get to the train, losing power with each track segment. So make sure to check that all of the switches are lined correctly.

Does your heavy train stop in spots? Can you improve performance at these spots by moving the power connection closer to them? If so, you are probably losing too much power along the track. When I have a choice, I try to put the power connector on the up-hill side of the layout, to ensure the least power loss when the train needs it most. If you have a large enough loop, there might simply be too much of a power drop to overcome through conventional methods. You can do some quick experiments to determine where the problems lie. While adding a headlight on the locomotive is extra power loss from the motor, it is a great indicator as to whether the motor is getting power and the intensity of the light should show you just how much power. Next, does a single locomotive make it all the way around the track? Then you should have continuity. Does it do so at slow speeds? If not, you might have dirty track (that darn inertia helped you get past at faster speeds). A pencil eraser should help clean the track but be sure to clean the right part of the rail. The 9v motors are a little odd compared to most model railroad motors. They do not take power from the top of the rail, they take it from the inside of the rail. From the shape of the motor wheels, the most critical spot is the inside- top corner of the rail. I've found a single sweep with an eraser across this corner on each rail is usually sufficient to clean the track. If your eraser leaves a lot of dust and droppings, follow it up with a soft cloth to clean them up. On a side note, I have also found that my locomotives with two motors under one baseplate seem to dirty the track quicker than two motors under separate locomotives. Assuming it is not simply due to a small sample size, my hypothesis is that this problem arises because when two motors are under a single baseplate they are rigidly fixed together and fight one another more than when there is the extra slack in the couplers between two locomotives with one motor each.

BURSTING OUT OF THE LINES

So far the discussion has been straightforward. But I was not able to pull that 50 car train without bending the rules, or <gasp> literally cutting corners. Any deviations from LEGO guidelines are done at your own risk, and most of what follows deviates from LEGO guidelines. So exercise proper judgment and precautions. First, let's return to the wheel holder. Whether you have a new wheel-set that drags from the first day or an old one that has worn out, the AFOLs also devised a solution, namely using a hobby knife to notch out the plastic where the wheels would otherwise rub on the wheel holder. I've used this trick on almost of my rolling stock.  If the train gets too heavy, the LEGO magnets can pull apart. Assuming you are running on a loop and don't catch it in time, the front of the train can smash into the rear. You can eliminate the magnets altogether and use drawbars or shared trucks (e.g., the center of the TTX car, set 10170), but assembling the train becomes a lot more difficult. Another alternative is to use rare-earth magnets. On Lugnet, Mathew Clayson suggested using D61 3/8" x 1/16" from K&J Magnetics. Noting that "this size works very well, and isn't too fragile.  On many occasions I've inserted these magnets between the standard LEGO magnets on adjacent cars to reinforce the coupling. When placing all of the motors at the front of the train, the forces drop off as you get further from the locomotives because there are fewer and fewer cars being pulled by that coupling. So you only need to reinforce the couplers in the front of the train, e.g., my 50 car train had these magnets between every car for roughly the first 30 cars. Rumors of other AFOL's using glue to stick the magnets together have floated around, but "glue" is a four letter word. Now let's return to that power equation. There are other ways to keep n small without shrinking the size of the loop of track. If the problem is simply a long loop of track, and not a heavy train, two or more power connectors (part 5306) from the same controller to opposite ends of the loop can shrink n in the denominator of the equation and reduce the power lost to the track. But care must be taken to get the polarity correct between the two power connections. Using multiple power connections also helps keep the train speed more even around the loop. When the train is really heavy or has more than two motors, a single controller probably cannot supply enough power. So instead of using multiple power connectors from a single controller, two (or more) separate controllers on a single track will increase the available power. But it becomes that much more important to have the polarity correct with the power connectors, and all of the controllers should be set to the same level and same direction. All four of the engines pulling my 50 car train had a single motor and power was supplied by two controllers connected on opposite sides of the layout. While the train made it around the loop under its own power, I had even more operational success when I cut back to 47 cars and added a fifth locomotive. In between, I added a third controller to supply enough power to the motors. The 47 car train ran for an hour before we replaced it with another train.

About the Author

Son of 2, Brother of 1, Father of 6, Friend to all, Bother to Many.  Born and raised all over the world I now reside in Southern California.

Physics -- Simple T/F for radio waves?

Question 1: True or False for the following five:
1. If a linearly polarized radio wave is approaching you head-on such that its electric field oscillates vertically, the best way to detect this wave with a loop antenna is to have the loop lying flat on a table.
2. If a linearly polarized radio wave is approaching you head-on such that its electric field oscillates in a horizontal plane, to best detect this wave using a dipole antenna, the antenna should be oriented horizontally.
3. The wavelength of red light is greater than the wavelength of green light.
4. Radio waves can be detected with either a loop antenna or a dipole antenna.
5. The frequencies of x-rays are greater than the frequencies of gamma rays.

[1&2] true

Lamda (Green) < Lamda(Red)
Lamda (Gama Ray) < Lamda(X Ray)

as for radiowave reception , its the wavelength ratio to dipole dims, what counts

Power Flower ~ Conducting the Serpent of Light ~ chakra 1 to 3.

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