This is what I do. Freight trains run slowly, passenger trains run a little faster, switchers run very slowly. .......and that is almost the top speed of the prototype. I had one from the original run that used to run at walking speed. I took it apart to letter it. When I put it back together it no longer ran at walking speed. I bought two from the second run and both run at walking speed. I sold all of my first runs after that. Those things look great with a bunch of wood boxcars and a wood combine as they pull the train at walking speed. That one is from the era in N scale when most locomotives had two speeds: Very Fast and Not At All. There were some that would not run at all, such as the Lima 2-6-4T. There were some that had three speeds: Very Fast, Still Too Fast and Not At All. The C-C Hudson and PA were the exceptions. Both had pretty good slow speed control. When Atlas introduced its RS-3 with the Kato chassis, that really changed things and it was up from there. The E-R Baldwin sharks are similar. The top speed on those things is not that far above that of the prototype. While those do have flywheels, it is amazing what many of B-mann's locomotives will do without flywheels. As you correctly indicate, the seventy and forty four tonners have excellent slow speed control. I fried the decoder on two of those, so I run them DC and the slow speed is walking speed. Bachpersonn's smaller steam power is similar. The 4-6-0 and 2-6-0 will operate very slowly with or without decoder (I fried decoders on several of them, as well). If you do the SPECTRUM tender upgrade to the 0-6-0, that slow speed control is good, as well. Bachmann accomplished all of that without flywheels. We had a guy here who used to baby and re-work old B-manns. He could make them run well. He remarked that the gearing was actually pretty good on them, it was simply that the QC on the gears was poor (they had a nasty habit of cracking) and that the old motors were not the best. I had a Reading 2-8-0 that fried its motor. I coupled it to a powered boxcar, removed the pilot truck and if freewheeled nicely. I left the gears in place, so they must not have been that bad, if they did not bind.
Thanks Carl, Not looking for perfect, just wanting to understand how people are dealing with what appears to be some very high speeds. What is setting the minimum voltage? How much margin do you give it?
brokemoto, this Trix unit has a pretty good speed range. It’s min speed is 12 SMPH at 3.6 volts. A bit high in speed, but this is in as received condition. I am confident that I can get both of those values lower. The Kato was 5 SMPH at 1.6 volts. These numbers are on true DC, no PWM. With a decoder the speeds would be lower. Thanks, Larry
Larry, I use a bit more complicated approach to speed matching than most, but it also allows mid-train helpers and end train pushers to move gracefully if you use the right decoders. This is much more difficult than one may think. For this reason, every locomotive that may run together gets setup with the same speed profile, that way trim can be used to dial it in more closely. For yard switchers I have a max speed of 35 mph For road switchers I have a max speed of 50 mph Early Passengers F & E units have a max speed of 75 mph Early mainline units have a max speed of 65 mph Modern passenger have a max speed of 110 mph (they run that hot out here in the wide open west) Modern mainline units have a max speed of 70 mph All steam locomotives are what seems right seeing them run. A Mikado should not be able to keep pace with a GS-4 When using Zimo decoders you can easily add midline and pusher locomotives if you want a modern super long freight train. This is where a little fun experimentation comes in. The Zimo decoders have a the ability to apply trim to the momentum settings. It takes a little experimentation to sync it all up. But it does work, set the head units first 6 inches later the midline units and 6 inches later the pushers. Give them all the same speed table, this will not work with the 3 point settings. Give them all the same momentum settings and then set the Momentum Trim to a value on the midline helpers and then double that for the pushers. On the test track, I use a large oval the length of two hollow core doors to dial things in.
DCESharkman, Thanks for the input. It gives me some interesting perspective to think about. For my more general testing, which will include my layout engines, Based on these discussions I am thinking about a slightly different approach. Namely, identifying three reference speeds. Main line diesel engines, 75 SMPH; switcher engines, 45 SMPH for now steam engines, 40 SMPH. My overall process will stay the same, for the engine only identify the speed & current voltage functions from min to 12 volts. In HO the max is 16 volts, so that will be different here. Previously(HO) the reference speed was what ever fell out at 12 volts. For this process that will be the above speeds & the voltage will vary for each engine. I do grade and train length studies at this reference condition. In most cases defining the speed, current draw train length functions at 0 & 2.5% grades. I use these results to identify the need & benefit for tune ups & with enough data, motor condition. Thanks to all who have shared their thoughts & processes. Larry
An old rule of thumb on steam locomotives was that their top speed in mph approximated the diameter of their drivers in inches. This was only an approximation though. Typically in a steam locomotive, speed and tractive effort were inversely proportional. That's why passenger locomotives typically had large drivers like the 80" drivers on a Pennsy K4 or the 79" drivers of a NYC Hudson while freight engines typically had small drivers such as the 63" drivers on a USRA Mikado or Santa Fe 2-10-2. Dual purpose locomotives (freight and/or passenger) typically had drivers with diameters around 72" or so.
I have been looking further into this subject. Running Engine only & up to maximum train length data on some engines. Eventually this will include the impact of grade as well. For now, I have the results of four N scale diesels shown in the following chart: This data is engine only on a DC test supply that is pure DC, no PWM or the variations. The tests are run on an 8 foot straight section. Except for the impact of a module in the system, test are run from a dead stop with he supply set at a specific voltage. The Atlas engine is new, so it must have the type motor that was indicated in the posts. The Kato engine, also new, runs as high a scale speed at voltage as any engine that I have tested. It also runs very low minimum sustained speeds. The tuning impact shown in the Trix engine has been demonstrated to varying degrees over a number of similar tests. The Bachmann engine is a fairly old vintage, but its speed function is close the the desired level. It has the highest minimum sustained speed & voltage. It also has significantly higher current draw than the other three. None are particularly high relative to the HO experience. The recommended max velocity level as recommended in earlier posts is show on the chart. It is interesting to see what that does to the corresponding voltage. This is an area of interest, because the train length capability is a function of electrical power, which voltage is a major player. The question is will the motor make up the voltage loss with current draw. If so, how close to the maximum sustainable current draw will the engine want to run. It may not be a problem. But it also may require the motor to run at a very high percentage of it capability, thus running hotter than desired. I have several more engines, including two steam engines the I am going to test. If I see anything of additional interest, I will post it as well.
That is an interesting scatter plot of the locomotives. I have never done that before nor thought about it. I just run the locomotives on the test track using DC to break them in. 2 hours forward and 2 hours in reverse at varying speeds. If I like the way they ran, then I install a decoder. I apply the correct speed table etc. Then I put them on the the test track with the Speedometer. I adjust the trim in forward and reverse so they can run together in either direction. The trim values can get down right silly. I had one Kato SD40 that had forward and reverse trim around 40. I have had Athearn Diesels that needed trim values in excess of 128. So the trim can be all over the map.
DCESharkman et all, I use these charts for a number of reasons in my improvement work. As I indicated in the first post, I am surprised that I am seeing the speed variation to be this large on latest release engines. The Kato & Atlas are both new. However that may not qualify them as latest release technology. The motor & drives may be from a thirty year old design. In HO that would not be the case for new engines. The design change with almost every release. They would tend to be more like the Atlas here. There are lots of reasons for variation in these curves. This is indicated by the pre & post tune results of the Trix engine. The variations seem to be manufacturer dependent as well. Indicating a quality difference in their parts. Most of the variations are motor dominated. When you are setting the Max & Min Vel CV’s, you are setting a X value on these charts to establish a Y result. As indicated by the range in the intersection on the desired max speed (Y value). This results in a large variation in the CV values. The decoder also will introduce additional changes in these results. The Trix engine results indicate that there is a time or deterioration element at play here as well.
The internal combustion engine is over 100 years old, but the basic operation of the valves and pistons are still the same all these years later. So because a chassis is that old in N Scale does not mean it is flawed. My Atlas/Kato GP-30 are all about 30 years old and still run like swiss watches.
