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Post by boxcarwilly on Jun 3, 2013 11:33:38 GMT -5
Dave. I do have a meter that my dad gave me years ago, and it is from the 1950's, but unfortunately, I don't know how to use it because I no longer have the instructions as to how to use it, and I can't remember what my dad said as to how to use it. Rob A. The speed was an estimate based on the positioning of the throttle on my power pack in relation to the other two 38's. The difference in the speed I estimated and what you got according to your instruments is based only on observation and perception. Without having the proper instrumentation, my 66% might equal your 30%. I think what I should have done in my initial tests is time each unit as to how long they took to complete one circuit of my layout. It never occurred to me to do that. Perhaps I should do that now. Be that as it may, if this Geep ran within tolerances on your test track and such was indicated with your instruments, then I can't dispute that fact. I therefore have to believe that the problem is in my layout. There is no other possible explanation. I have ruled out any of my power packs based on the performance of all my other engines. I think I'll invest in a new meter and learn how to use it. Perhaps that will give me some insight as to what is happening here. It might help me with my signalling issues as well. I do appreciate Rob K absorbing the shipping charges.
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Post by Rob Albritton on Jun 4, 2013 8:14:30 GMT -5
A meter is always a good investment. It's $20 well spent.
We stand-by to assist in any way we can. Whenever I get frustrated, I keep reminding myself of a tag line an N Scale guy use to use on one of the DCC forums: "Remember, Model Railroading is FUN!!!"
Best, -Rob(A)
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Post by markm on Jun 7, 2013 19:48:40 GMT -5
all, This thread has been interesting, but you seem to miss an obvious scenario: if the "slow" loco is within spec, the other two locos are just running too fast! Of course, I've never heard anyone complain about fast locos. I don't know whether AZL or any loco manufacturer rejects locos for being too fast. Even the NMRA's practice allows for a 50% spread, in maximum speeds, which isn't far off from the discussion here.
Willy, That siad, I don't know if you really want to put a lot of effort into examining the electrical on your layout. But if you do, having some knowledge of a meter will make the work go easier. If you want to post an image of your meter, I'd be happy to suggest the best ways of using it.
Rob(A), With all the locos AZL is bringing out, you might want to come up with a customer speed test. I might help to elminate much of the confusion over performance. My American Flyer locos all had a factory specified speed test like: "on a 21 inch oval, the loco will make at least 4 revolutions in one minute at 12V and draw less than 900mA." Maybe a 220mm oval at 5V? It's not a comprehensive test, but it works well to identify slow AF engines.
Mark
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Post by boxcarwilly on Jun 11, 2013 11:35:42 GMT -5
Mark: You present an extremely interesting perspective to my problem. I confess that I had not even considered the fact that my other two 38's were running faster then AZL specs called for and the slower one is actually within specs as indicated by Rob K's testing. If that is actually the case, and I'm thinking more and more that it is perfectly logical, then the problem isn't within my layout. I have been away from my layout for several days due to health issues and yesterday was the first day I've actually spent on it but I didn't do any testing of locos. I've been thinking about my problem during that period and trying to come up with ways to determine the issues here. But in reading you remarks, I think a light bulb just went on. When you get right down to it, the difference in speed doesn't really matter all that much since the two best performing 38's or higher speed if you prefer, as of the same livery and therefore run on a separate line then the slower 38 which has it's own line. When this is taken into account, speed no longer becomes the issue. The other thing to consider here is that both lines have their own power source so if one source doesn't put out the same power as the other, it doesn't matter. As long as I don't put both liveries on the same track, everything is just peachy. Interestingly, when I compare the speed of the two best running 38's to that of MTL's GP 35's they are slightly slower, but when compared to MTL's SD40-2's, they are slightly faster. Now when I take my slower AZL 38 and compare the speed to that of AZL's SD75's it is about the same speed and slightly faster then MTL's SD40's and much slower then MTL's GP9's. So in all of this, you have to draw your own conclusions. I guess speed really becomes relative to the consist you lash up to. It's all so technical and my mind is beginning to hurt.
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Post by BAZman on Jun 11, 2013 11:42:11 GMT -5
With DCC, each loco can have it's own speed table so there won't be any difference
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Joes
Fireman
Posts: 84
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Post by Joes on Jun 11, 2013 16:11:54 GMT -5
I like locomotives that run slow. Much more prototypical. :-D
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Post by ztrack on Jun 11, 2013 22:29:59 GMT -5
I have two NS SD70Ms - first generation. These were the ones that ran slowwwww.... We (AZL) took a lot of criticism for the speed range on these. But I have to tell you, these two are still up there for my favorite runners. That have put in many hours during running sessions in our train club. They run very smooth and consistently. More than once, we received comments from other railroaders on the the nice slow speed they ran. Of course, the kids wanted them to go faster! Here is a photo of them on our club layout. The locos are on the right. The tail end of the Bethgon unit train is on the left. This would be a 36+ car train. Rob
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Post by domi on Jun 12, 2013 3:46:36 GMT -5
I do agree... Locomotives that run at 250+ smph are no interrest for me.. I have 3 1st generation SD70s that are my absolute favourite locomotives. They barely make 45 smph under full power but they have terrific low speed caracteristics. And all this without the least sound, and pulling like mules... I do love them!
Dom
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Post by catt on Jun 12, 2013 7:57:56 GMT -5
My AZL GP38-2s and my MTL GP35s all run a slow steady pace.Which is alright by me as they look more prototypical to me.I can understand kids wanting the trains to run faster, but I have had folks in my age group (I'm 68) tell me my trains are running to slow.I just explain to them that they are my trains and that is the speed I want them to run. ;D
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Post by boxcarwilly on Jun 12, 2013 12:19:04 GMT -5
Like I said, speed is all relative to the engines you use and the lashups you put together. I don't run DCC because it's far too expensive for my taste, but for what I have generally speaking I'm satisfied and I get good performance from all my engines. I like to keep my trains going at a scale speed of 50 mph. I figure that's a realistic speed for a main line freight. Of course going up grades will slow the speed down depending on the consist but that's to be expected. When I want to run mixed engines I put them on the same track and see which one goes the fastest. This engine becomes my lead, and then the next fastest goes number two and so on and so fourth and such like until I have the desired number of engines ready for the cars. It's really the only way I can do this since I don't run DCC. All my engines are numbered according to type, and I have a notebook where I have the engine numbers and how fast they run on a scale of 1 to 10. Complicated? Well perhaps, but it works for me. Since Mark enlighten me re: speed and manufacturers specs, I'll be happy with what I have right now with this particular 38.. But since getting it back from AZL, I have yet to try it pulling my heavyweights which is what it was originally purchased for. I'm hoping it will do better this time around. Rob. You will have to correct the sign you have in the background of your picture. Z scale is no longer the smallest scale. T scale is smaller still.
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Post by amtk908 on Sept 15, 2013 19:04:29 GMT -5
Greetings All:
Well it seems that I have encountered the same GP38 speed anomaly as boxcarwilly did. I have two GP38-2s purchased roughly six weeks apart. I just now am getting around to putting some track down and I opened both units to give them some break-in running on a small figure-eight layout. Both units were run-in for approximately one hour in each direction around the figure-eight. One unit appeared to be operating a good bit slower than the other so I did a few timings to confirm my suspicions.
The figure-eight is a circuit of approximately 3.45 meters and is comprised of 220mm curves, a 90 degree crossing, 220mm and 110mm straight sections and is on a level surface. The power supply is a Rokuhan RC-01 using the AC adaptor; and for these timings it is being operated at the full-throttle setting. Prior to the timings, each unit was run forward and reverse for approximately ten minutes to loosen them up. The average of ten timings for each unit / direction is as follows:
Unit 1 Forward 30 seconds Slower Unit Reverse 27 seconds
Unit 2 Forward 20 seconds Faster Unit Reverse 19 seconds
This data seems to correlate pretty closely with the performance experienced by boxcarwilly.
Obviously, with this speed differential, they may not run particularly well together. As I am using a Rokuhan power supply, track and modular power connectors, I did not have an opportunity to put an Amp-meter in-line to check current draw. Today I ordered yet another GP38-2 and I will be curious to see which unit it is a closer speed match for, Unit 1 or Unit 2. I will report my findings when it gets here and I have had a chance to break it in and rerun the timing tests.
Rob A. or Rob Z. … I would be curious to know which of these two units more closely represents the expected speed performance for this unit based upon your design and your experience with these units.
Thanks and regards, Cliff
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Post by markm on Sept 15, 2013 20:39:14 GMT -5
Cliff, It would be interesting if you had the throttle voltage. So we can talk in common terms, I converted your layout from scale (0.4715 mi) and find that Unit 1 is running at 56 mph and unit 2 at at 84mph. For reference the prototype top speed was 65mph. For my two gp38-2s I get a closely correlated average:
Voltage Speed (MPH) 7 55 7.5 60 8 72
Mark
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Post by amtk908 on Sept 16, 2013 6:26:02 GMT -5
Mark, Let me see if I can get you some voltage readings this evening; if not tonight, certainly within the next few days. Thanks for the SMPH conversions. I suspect that you are dead on with a max speed of 65 as I assume that NRE rebuilt the BNSF Geeps with 62:15 gearing. Yes, I know the body style is not correct for the NRE rebuilds, but that is where AZL chose to number their models. :-) I will certainly operate the units at considerable less than maximum throttle/speed. My point of curiosity is the difference in performance between the two “relatively identical” units. I will be curious to see where the performance of the third unit falls. Thanks, Cliff
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Post by ztrack on Sept 16, 2013 7:26:33 GMT -5
Cliff, We do not have an 'expected' speed. We test run all locomotives and look for them to fall into an acceptable speed range. There are many factors when it comes to speed that can affect how fast or slow locomotives run. I covered this topic in the May/June 2013 issue of Ztrack Magazine. The article, 'Speed matching, myth and reality' covers this topic in more detail. www.ztrack.com/issues/issues_13.htmlOne very important point to remember, you can run these locomotives together. Just put the faster locomotive up front with the slower locomotive trailing. Rob
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Post by markm on Sept 16, 2013 8:13:55 GMT -5
Cliff, Here's some of my data on the GP38. Thought I had posted this before. The Marklin is the "big blue" original DC throttle and the "Snail" is the commonly available PWM throttle. Note that the Marklin unit design regulates poorly at the low power draw of the GP38 and the maximum voltage can vary up to 12V. I don't recommend anyone operate their loco at such a high voltage. Hope this answers some questions. Mark [
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