The world of scale modeling loves to represent speed, with jets and rockets. You can buy models of dragsters, hydroplane boats, racing planes, stock cars, and all the other vehicles of speed. Heaven only knows I built my share of that type model as a kid and stoked dreams of going that fast in real life. So here I am: editor of a model railroad magazine, where we gloat over how slow we can operate a locomotive. So what’s up with that?
In real life, trains don’t have jackrabbit starts. Sure, the occasional hogger will get into the throttle a little hard and give us a jerky start. This is a habit that won’t last long because it’s a good recipe for broken couplers. The fact is locomotives start trains very gradually for a couple of good reasons. First, locomotives by themselves are ponderously heavy. The latest road locos from GE and EMD weigh around 420,000 pounds. Train weights are noted in thousands of tons, as in a loaded unit coal train that runs something over 10,000 tons. You just can’t get this kind of weight to slingshot off the line.
Second, I recall a steam-era photo of a B&O Maintenance of Way foreman complaining bitterly to the Motive Power Superintendent about worn spots in the rails at the station from where certain hoggers would routinely spin their drivers as they started. The Motive Supe was completely sympathetic because this power largesse was also damaging the engines and accelerating the wear on their drivers. Smooth, gradual starts are appreciated by management.
When you’ve got a loco model that will crawl so slowly you can measure its progress in the number of seconds it takes the pilot to go from one tie to the next, you’ve got a dandy performer. I’ve had models that could go so slow you have to have the shell off and a marked line on the flywheel just to see the progress. It’s like the tip of the minute hand on a clock.
So, you ask, how often might an operator wish to have the model go this slow? The answer is simple: every time it starts or stops. Digital Command Control (DCC) allows us to break speed into 128 little steps. Then you add some momentum up and down, and now you can spin the throttle to Speed Step 25 and let the locomotive’s decoder add steps at reasonable intervals. When Step One produces a scant one scale mile per hour or less, the model may then start and stop with the appearance of prototypical smoothness.
Conversely, when the slowest speed your model will go is around 5 scale miles per hour, you now have a jackrabbit start that looks very unprototypical. Weighing down all this exuberance with a good train can help, but I’ve watched models that jump against the train, take out most of the slack, and then lay down until the voltage gets high enough for it to jackrabbit its way out of the situation. Predictably, this also contributes to its share of train-in-twos and derailments.
While DCC may offer some tools for improving this situation, the roots of the problem lie back in just plain DC and could be corrected there, and DC operators appreciate good, slow operation just as much as the DCC crowd. The components of the drive system explain the entire situation. From the motor to the drive wheels, there is a train of gears, usually starting with a worm-and-pinion and progressing through a variety of straight gears until we arrive at the drive gear on each drive axle.
The motor must be carefully matched to the process so it is powerful enough without wasting power or space. Its speed within the operating voltage range must match the gearing. Adding flywheels to the motor shafts has long been an ingredient for increased smoothness. Typically, worm gears are brass and must be carefully inspected to be certain there is no flashing or irregularities. The nylon pinion gear must mesh just so, neither too tight nor too loose. You, as an operator, can increase the life of this gear by not engaging in sudden power reverses. Easy does it, another reason for smooth starts and stops.
The motor alignment with the gear must be pretty close to perfect or there will be binding. I’ve seen motors with bent shafts such that the worm wobbled: not good at all. The pinion gear must be mounted in a good bearing on a good shaft, square with the frame. Every tooth on every gear must be properly shaped. Nylon gears tend to be molded and all flash and artifacts from the molding process must be removed.
Modern model railroad locomotive models have been generally good, at least of late, but there are still exceptions, better and worse. I like to give credit where it’s due, and so I’ll say it right out front: in terms of consistently superior low speed performance right out of the box, my award goes to Atlas HO. To be sure, they aren’t the only company with smooth, slow runners right out of the box, but I consider them to be the most reliable in this department. With everyone having their models produced in China — often in the same factory — differences in quality are often set by the determination of the importer. I get the feeling that Atlas demands the best, but they will also pay for that. You’ll pay for it, too, but you have to ask if it’s worth it to you.
Also, at least in drive operation, smoother starting locos generally perform better at higher speeds. I’ve had models of Geeps and 0-6-0T switchers that could post better than 120 smph, an utterly ridiculous number. Yes, you can trim back the top speed using DCC’s “Top Volt” control, but that begs the issue of fundamental design. Jackrabbit starts and overspeed on the top end often accompany each other, because the motor and gears are not scaled properly.
At Model Railroad News, we have taken some pains to construct our By-The-Numbers section on Z, N, HO, and Large Scale locomotives so you can see how our sample performed. On some occasions we detect a model that doesn’t perform up to snuff and suspect some error in manufacture, and we contact the maker to request a second sample. All of the companies we asked have been very supportive and wanted the defective unit back for their study.
If you are at all concerned about how a model might perform, please take the time to read the BTN tests on a variety of models and get a sort of sense about it. I took pains to gain the overview of a number of mechanical and design engineers who made suggestions and improvements until we had a process that can be duplicated with accuracy and would give valid results. For those who are new to this magazine and are unfamiliar with our BTN, look for a discussion about it in next month’s edition.
We give you the hard data and let you decide — laid against the rest of the model and its price — if this is a good product for you. When you take yours home, you can compare it to some extent to our results, letting you know what to expect. While car counts aren’t and won’t be included (they may be mentioned in the text), our ounces of pull serves the same role as Tractive Effort for railroads. It provided a baseline, which each railroad learned to compare against its ruling grades to determine power needs. That would be our goal here. You be the railroad and enjoy.
In real life, trains don’t have jackrabbit starts. Sure, the occasional hogger will get into the throttle a little hard and give us a jerky start. This is a habit that won’t last long because it’s a good recipe for broken couplers. The fact is locomotives start trains very gradually for a couple of good reasons. First, locomotives by themselves are ponderously heavy. The latest road locos from GE and EMD weigh around 420,000 pounds. Train weights are noted in thousands of tons, as in a loaded unit coal train that runs something over 10,000 tons. You just can’t get this kind of weight to slingshot off the line.
Second, I recall a steam-era photo of a B&O Maintenance of Way foreman complaining bitterly to the Motive Power Superintendent about worn spots in the rails at the station from where certain hoggers would routinely spin their drivers as they started. The Motive Supe was completely sympathetic because this power largesse was also damaging the engines and accelerating the wear on their drivers. Smooth, gradual starts are appreciated by management.
When you’ve got a loco model that will crawl so slowly you can measure its progress in the number of seconds it takes the pilot to go from one tie to the next, you’ve got a dandy performer. I’ve had models that could go so slow you have to have the shell off and a marked line on the flywheel just to see the progress. It’s like the tip of the minute hand on a clock.
So, you ask, how often might an operator wish to have the model go this slow? The answer is simple: every time it starts or stops. Digital Command Control (DCC) allows us to break speed into 128 little steps. Then you add some momentum up and down, and now you can spin the throttle to Speed Step 25 and let the locomotive’s decoder add steps at reasonable intervals. When Step One produces a scant one scale mile per hour or less, the model may then start and stop with the appearance of prototypical smoothness.
Conversely, when the slowest speed your model will go is around 5 scale miles per hour, you now have a jackrabbit start that looks very unprototypical. Weighing down all this exuberance with a good train can help, but I’ve watched models that jump against the train, take out most of the slack, and then lay down until the voltage gets high enough for it to jackrabbit its way out of the situation. Predictably, this also contributes to its share of train-in-twos and derailments.
While DCC may offer some tools for improving this situation, the roots of the problem lie back in just plain DC and could be corrected there, and DC operators appreciate good, slow operation just as much as the DCC crowd. The components of the drive system explain the entire situation. From the motor to the drive wheels, there is a train of gears, usually starting with a worm-and-pinion and progressing through a variety of straight gears until we arrive at the drive gear on each drive axle.
The motor must be carefully matched to the process so it is powerful enough without wasting power or space. Its speed within the operating voltage range must match the gearing. Adding flywheels to the motor shafts has long been an ingredient for increased smoothness. Typically, worm gears are brass and must be carefully inspected to be certain there is no flashing or irregularities. The nylon pinion gear must mesh just so, neither too tight nor too loose. You, as an operator, can increase the life of this gear by not engaging in sudden power reverses. Easy does it, another reason for smooth starts and stops.
The motor alignment with the gear must be pretty close to perfect or there will be binding. I’ve seen motors with bent shafts such that the worm wobbled: not good at all. The pinion gear must be mounted in a good bearing on a good shaft, square with the frame. Every tooth on every gear must be properly shaped. Nylon gears tend to be molded and all flash and artifacts from the molding process must be removed.
Modern model railroad locomotive models have been generally good, at least of late, but there are still exceptions, better and worse. I like to give credit where it’s due, and so I’ll say it right out front: in terms of consistently superior low speed performance right out of the box, my award goes to Atlas HO. To be sure, they aren’t the only company with smooth, slow runners right out of the box, but I consider them to be the most reliable in this department. With everyone having their models produced in China — often in the same factory — differences in quality are often set by the determination of the importer. I get the feeling that Atlas demands the best, but they will also pay for that. You’ll pay for it, too, but you have to ask if it’s worth it to you.
Also, at least in drive operation, smoother starting locos generally perform better at higher speeds. I’ve had models of Geeps and 0-6-0T switchers that could post better than 120 smph, an utterly ridiculous number. Yes, you can trim back the top speed using DCC’s “Top Volt” control, but that begs the issue of fundamental design. Jackrabbit starts and overspeed on the top end often accompany each other, because the motor and gears are not scaled properly.
At Model Railroad News, we have taken some pains to construct our By-The-Numbers section on Z, N, HO, and Large Scale locomotives so you can see how our sample performed. On some occasions we detect a model that doesn’t perform up to snuff and suspect some error in manufacture, and we contact the maker to request a second sample. All of the companies we asked have been very supportive and wanted the defective unit back for their study.
If you are at all concerned about how a model might perform, please take the time to read the BTN tests on a variety of models and get a sort of sense about it. I took pains to gain the overview of a number of mechanical and design engineers who made suggestions and improvements until we had a process that can be duplicated with accuracy and would give valid results. For those who are new to this magazine and are unfamiliar with our BTN, look for a discussion about it in next month’s edition.
We give you the hard data and let you decide — laid against the rest of the model and its price — if this is a good product for you. When you take yours home, you can compare it to some extent to our results, letting you know what to expect. While car counts aren’t and won’t be included (they may be mentioned in the text), our ounces of pull serves the same role as Tractive Effort for railroads. It provided a baseline, which each railroad learned to compare against its ruling grades to determine power needs. That would be our goal here. You be the railroad and enjoy.