Hi everyone:
I just installed a Loksound Select decoder in an IHC 4-4-0 American. My problem is that it seems to operate very smoothly at somewhat higher speeds but is very jerky at low speeds.
The locomotive in the illustration on the Loksound listing for the decoder is an older locomotive than the one I am working with. The illustration shows a 4-4-0 from around the 1850's whereas my locomotive I believe was made in or around 1885. I am basing that on having examined a real 4-4-0 locomotive operated by the South Simcoe RR in Tottenham, Ontario. I am not a steam expert - far from it, but the IHC model and the South Simcoe locomotive have many similarities.
What I am asking is: would a very early 4-4-0 American have operated very unsmoothly at very low speeds? If so, the decoder I have chosen for the somewhat later 4-4-0 may not be quite correct. However, if the early 4-4-0 locomotives operated smoothly at low speeds then I might have a defective locomotive, or at least one that needs some run in time.
Please keep in mind that at speed step 10 of 128 the locomotive is very smooth. Also, in reverse the locomotive is smooth at whatever speed it is running. I suspect that the programming in the decoder isn't quite what I need.
Anyone with any knowledge of how smoothly the original 4-4-0s operated out there?
Assuming it is a decoder programming issue, does anyone have any experience with how to reprogram this specific decoder.
Just to clarify, I am not a total newbie at decoder installation and programming. I have done more than a few. No, I haven't reread the Loksound manual yet. I was hoping someone out there could save me the trouble.
Thanks
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
In the real world they would have operated just as smoothly, they still had valve gear and variable cutoff.
Did you test run the model on DC before installing the decoder? There is probably a bind in the mechanism somewhere, possibly the valve gear, or the drivers are ever so slightly out of quarter. If the motion is kind of jerky at low speeds that's probably it, as it binds, the BEMF increase power to the motor to try and keep it going, it finially has enough to overcome the friction caused by the binding, and jumps slightly, then the BEMF crnaks back down until the same spot comes up in the next revolution. And at higher speeds, there's enough power to get past it so the jerky action seems to disappear.
Model steam locos can be more finnicky than the real thing, especially with the loose tolerances often employed to compensate for typical model curve radius which is far tighter than all but the tightest industrial trackage.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I had a similar situation in an older "cheapie" engine my grandson had me install a decoder in so he could run it on my layout. It was very jerky at low speed but smoothed out the faster it went. It looked for all the world to be a bind in the mechanism, but it ran very smooth and slow on DC, so I knew that wasn't the case.
LokSound Select decoders have an Automatic Motor Tuning Feature. This feature will automatically adjust the Back-EMF in most cases. This is not meant to be a “cure all” solution. This will only get the settings close. There still may need to be some manual adjustments made.In order to use this automatic adjustment you will first need to set CV 54 to a value of 0. Then put your locomotive on the layout and activate F1. Be sure to have plenty of clear space ahead of your locomotive. Your locomotive will quickly take off at full speed and gradually slow down to a stop while reading the motor responses. This will automatically set the load compensation in CVs 52, CV 53, CV 54, and CV 55. From here you can make any other manual adjustments if needed.
That cured most of my problem. Give it a try, it might be all you need.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Randy:
The locomotive did run smoothly on DC.
Mark:
I will try what you said. Your explanation makes sense because the locomotive did run smoothly at all speeds on DC. I should have mentioned that the low speed hesitation occurs more than once per revolution and changes with the speed step. At speed step 1 the hestitation seems to occur eight times per revolution. At speed step 2 it occurs four times per revolution. At speed step 3 it is as smooth as silk yet the speed is still very slow.
I will have to set up a length of track because I don't have a layout. Can you give me an idea of how much track I will need. I can get about 15 ft. on the floor of my workshop.
I really appreciate your detailed help.
It should be able to do its thing in about ten feet, but the extra won't hurt. It does kinda take you by surprise when it takes off at full speed, even when you're expecting it ! LOL
If you are still having a bit of problem, start lowering the regulation reference in CV56 until it smooths out. The default value is 255 at 100%.
What is causing the problem is how the BEMF is reacting with the "cheaper" motor. I'm willing to bet if you were to turn the BEMF off altogether, the problem will go away. Try setting CV49 to 18 (BEMF off) if you want to verify - CV49 default is 19 (BEMF on). I would try to get it running better with the BEMF on as it really improves slow speed performance. That being said though, some motors just don't like that BEMF pulse and function much better with it turned off.
Hi Mark:
I will try the engine with BEMF off to see what happens. I have been running it a bit on my test track (all of six feet) and It runs fine at speed step 3 (of 128). It is not what you would call 'creeping' exactly but it is plenty slow enough for switching. If I can't solve the problem then I will just avoid speed steps 1 and 2.
My biggest problem with doing the decoder self setting will be getting down on my knees. Even with good quality knee pads it just isn't fun. Oh well, that's my problem. Now if I could only lose about 60 lbs.
Thanks again.
EDIT:
I tested the locomotive with CV 49 set to 18 and it wouldn't move at all. I pushed the throttle up to speed step 11 and still no movement.
Those little three pole motors take a pretty good poke to get them turning. I had one that would crawl on speed step one with BEMF turned on. If I turned BEMF off, it wouldn't move until speed step 16 of 28 ! Increasing the start voltage got it to move on speed step 1, but it wasn't very slow by no means.
Unless to re-power the little guy with a better quality motor, you might be rather limited as to just how well it will run. Still, with some tuning, it should run reasonably well with the BEMF on. Give the "self test" a try and see what you get.
All the auto tuning of the Loksound Selects i have done was in less than 3 feet. The auto tune gets it close but not perfect. After the autotune you can fiddle with the BEMF settings by one or two points to get it spot on.
Running better in reverse is telling me that there is something wrong with the drive train. Either the motor shaft is moving fore and aft or a worm is moving fore and aft. Also check for valve gear binds.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
Pete:
I was wrong about it running smoothly in reverse. When I went back to run it again the hesitation occurred in reverse in the same way it does in forward. I must have been running it at speed step 10 in reverse which is the first speed selected on my NCE Power Cab when you hit the "INC FAST" key - I don't remember. I apologize for not getting that part correct when I first posted.
Thanks for letting me know that I don't have to get down on the floor to do the auto tuning. I can get nine feet of track on my workbench if I run the track across the computer desk too. The workbench and the desk are at the exact same height, which was how I planned it when I built the workbench for just such an occasion.
Thank you for your input. Greatly appreciated.
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Dave.
I believe you have a bind somewhere. Either a bent rod, axle, or driver quarter or some sort of interfearence. When I reasembled my brass 2-6-0 I did not notice that the cylinder saddle was cocked to one side. The bind was very noticable at low speeds. It was not until I had it upside down on the workbench powering it with clips to the motor and then I saw that the cilinders were not parallel to the frame. Since that is the first part to be screwed to the frame I had to disassemble the whole thing again. I then used a small square to square it to the frame. Now it runs super slow.
I finally got around to doing the auto setting for BEMF as you (and others) had suggested.
Problem solved!!! It now barely creeps at speed step 1 with no hesitation. I didn't have to make any other adjustments.
Thank you very much for sharing your knowledge. I have several Loksound Select decoders but until you mentioned it I had no idea that the automatic setting option existed.