I think you mean CV3, CV2 is the start voltage, and the higher you set it the more the loco leaps like a gazelle when the throttle is cracked. Most decoders, CV3 = 10 equals 1/10 second between speed steps, that's not that much of a delay.
Anyway, that's momentum, not slow speed. If the best adjustment to CV2, start voltage, the best you can do is have the loco run at 5 scale MPH, it won't creep no matter how high you set the momentum.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Part of the answer is in getting the engine to run smoothly. If the CVs are set right, the engine will run so slow you can not see it unless there is binding in the engine.
Set CV2 to 5= Watching grass grow.
Set CV2 to 10= Watching paint dry
tatans wrote:Still no exact answer to my question, it would seem a certain element of MR's will do everything possible to super slow their locomotives, but will not give a reason why. Conversley, if they can mega slow their locos for some strange reason, what would their response be to a group who goes to the other end of the spectrum and runs their trains at absolute maximum speeds, would they be considered a little odd???
I have read on Ken Clark's guide to remotoring and regearing (http://hometown.aol.com/kenrclark/guide_to_repowering_and_regearing.htm) that a can motor typically has a starting RPM to top RPM ratio of approximately 12:1 (on filtered DC). The implication is that you cannot have very slow speed running and a fast top speed. If you gear for a 3 scale MPH minimum speed, top speed is going to be about 35-40 MPH. For many modelers, that is too low a top speed, so the gearing is set for a higher top speed, and various pulsing methods are used to generate the very slow speeds. To get a wider speed range, coreless motors are needed, which creates a new set of issues and much higher costs.
Whether you favor higher top speeds or very low speeds depends on your preferred operational style. Those who like to watch trains run tend to prefer higher speeds. Those who want to do switching or run timetable operations prefer slower speeds.
Manufacturers (except 3 rail O, where faster is expected) have been prodded for years to make the 12 volt scale speed about equal to the prototype's maximum speed. If a model loco doesn't do this, it gets dinged in the MR reviews. The same happens if the slowest speed isn't below 5 scale MPH.
For my TOC shortline and narrow gauge, I'd personally rather have the top speed limited to what was practical operating speeds for the prototype - quite a bit less than top speed - to gain in improved low speed performance. For instance, a 4-4-0 pulling a passenger train would rarely be operated above 40-45 MPH - the track wouldn't permit it, even though the loco was capable of faster with a light load on level track. The speed limitations were certainly true of most narrow gauge operations where maximum speed anywhere on the line was usually less than 40 MPH, and 30 MPH or less was more typical. Shays had top speeds of around 12-15 MPH, and the other geared locomotives weren't much faster.
Even today, the now-UP trains I see going over Donner Pass are usually in the 30-45 MPH range, and about 50 through Humboldt Valley in Nevada. In the days of drag freights, speeds seldom exceeded 15 MPH over the mountain grades - the object was to drag just as much tonnage over the summit as possible, rather than trying for speed.
Bottom line, as other have said, is that most model railroaders tend to operate much faster than their prototype. If you are modeling prototype operation (except for regional Amtrak operations), you want a slower locomotive.
my thoughts, your choices
Fred W
I suspect you have a mindset or just venting frustration. rrinker and a couple others explain it quite well. Multiply engine movement by 87 (HO Scale) to get an idea of actual speed. When locomotives normally connect to a car, they do not move the car/cars at contact as the hose have to be connected. A nice slow moving model loco with good couplers will couple without moving anything else. Most model coupling I have seen and done would damage prototype rolling stock. Don't forget, we are all boys still playing with toys. Ask our significant other. I am sure those who work on prototype railroads laugh at how we modelers operate.
rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
tatans,
While it's true that we hardly ever run an engine at these ultra-slow speeds, the slower one can be made to run the better, simply because doing so indicates that you have a very good decoder, a good motor, and very smooth running mechanism; and these are all desirable traits in a model.
I think I answered it. Watch a real train. They go SLOW, especially when starting, drifting to a stop, and switching cars. Under the best of circumstances, a model loco will never coast like the real thing, using momentum for the slow drift to a halt. In scales larger than HO it might be possible to build a gear train with a large enough flywheel to make it work, but in smaller scales it has to be simulated.
As for the racetrack type, yes, I think they are wierd. Even if a particular protoype loco could go 120MPH, our model curves, even in some rather large layouts, are so tight that the prototype either couldn't negotiate them or would be restricted to low speeds. Even a 30" radius curve in HO is very sharp by prototype standards and no train would be able or allowed to negoiate such a curve at 100 mph. The physics works for us in this case and we can run our models at warp speed. But the physics works against us when it comes to simulating the momemtuma nd inertia of a real train, which is why we simulate it electronically.
Doc,
Along with a decoder with BEMF, you can improve low end response by tweaking the start voltage (or CV2).
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
tatans wrote:Just a quick question, what would the reason be to have a locomotive (move?) in super slow speed so it is almost impercievable to see it move? is there a reason for this, I have never seen a locomotive in real life move a slow as possible. Am I missing something here? I have heard this before that model railroaders do everything to prototype then run trains at mega-slow speeds. any help here?
Remember we are dealing with scale here as well. I've seen real steam locos start up and as they start drifting forward you can count the ties passing by. And even with large flywheels, the coasting capability of most models isn't up to the prototype's momentum so you need a slow speed to couple up cars withotu smashing them to bits. As for scale speed - an HO model moving 1 inch per second is moving at a scale 5mph. Run your train at a speed you think looks good, then see how fast it is covering a measured distance and convert to scale speed. Bet it's WAY faster than you think.
Well, if you are switching a yard, you want fine control so that you aren't crashing into cars. (Saves wear 'n tear on couplers.) Also, for the MRRer, speed matching locomotives for MUing is easier if you have finer control.
Aside from swapping the whistles (my model is an in-service unit and the second whistle on F4 is the one I wanted on the momentary function F2) I think the only thing I changed was adjusting CV2 so that it started moving on speed step 1. I just did this trial and error using ops mode programming, set it on speed step 1 and just kept increasing CV2 until it just began to creep.
I DID have to open up the loco and align the motor to get it to run smooth, the motor was cocked to one side which meant the universal joint was always bent. I loosened up the motor mount screw and help it straight and re-tightened it, problem solved. With the motor cocked to the side there was a slight hitch in the motion with each rotation.
A combination of a good motor, a back-emf decoder, and good power pickup will generally result in very smooth slow motion operation. Some tweaking of CV values might be required to get just the right settings for a given locomotive. A factory example is my PCM T1, you can watch the drivers step bit by bit at speed step 1. It takes over a half hour for it to make one loop of my 8x12 layout.
If you are adventurous you might try to re gear the engine. I have a HO 4-6-0 with can motor, flywheel and 45:1 gear reduction and a 0-4-0 with can motor, flywheel and 72:1 gear reduction. I used NMSL motors, flywheels and gears. With DC and pulse power, action was beautiful. Now with DCC, I cannot believe tha action or almost lack of action.
Also, find out what your system and decoders are capable of. Yahoo has some good DCC groups.
Along with Art's advice, make sure you purchase a decoder that has back EMF (BEMF). You'll nomally find that feature on 4 and 6-funtion decoders. The locomotives that I have BEMF really have terrific low speed response.
How can I get super slow motion in DCC?