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Post by amtk908 on Sept 16, 2013 9:12:49 GMT -5
Rob and Mark, Thanks for the input. Much appreciated.
Rob – Your point about operating the units together, faster in the front, is entirely valid! I was just surprised to see such a variance between two units of, what I would assume to be, pretty much the same lot. Although new to Z Scale, I have been modeling in a number of different scales for over 45 years and had not previously encountered such a variance in unit performance when comparing units of the same type, from the same manufacturer, with a close proximity of production dates. Guess I had been unusually lucky. One of the great things about this hobby is that there is something new to learn all the time.
Thanks again for all of your input!
Regards, Cliff
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Post by amtk908 on Sept 16, 2013 16:04:09 GMT -5
Mark -
Per specifications the Rokuhan throttle has an output of 10V. Per my meter, no load, the output is 11V.
Regards, Cliff
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Post by markm on Sept 19, 2013 13:04:07 GMT -5
Cliff, I'm impressed with the 10V under load. That voltage would imply that unit #1 is a bit on the slow side. That's a bit of a relief because it's much easier to figure out why a loco is too slow than too fast.
Regarding the variation between units as compared to other scales, there are NMRA standards and recommended practices for other scales that don't exist yet for Z. The NMRA recommends the model's speed at maximum throttle be the same as the maximum prototype speed with a 25% variance. Don't know if AZL tries to meet this recommendation but I've found at 8V, everything I've got from AZL falls in that range. Of course, there is no standard maximum throttle voltage for Z. So, what do use: 8V? 10V? I even recall reading that someone was using 12V motors. The only other scale I've modeled in is S. The manufacturer set a minimum standard of a certain number of revolutions per minute around a 21" circle. Test was performed at a given throttle, and maximum current draw was specified.
As a former manufacturing guy, I suspect the main issue is manufacturing variation. Things like a left-handed operator vs. a right-handed one can make a difference in a product. With the low Z scale production volume as compared to other scales, these sorts of differences become more visible.
Mark
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Post by amtk908 on Sept 20, 2013 20:28:56 GMT -5
Mark et al:
I purchased a third AZL GP38-2. After break-in and testing routines identical to those performed on the previous two units, the results are in for Unit 3 and it is nearly a carbon copy of Unit 2.
Unit 3 Forward 21 seconds Reverse 19 seconds
Upon further inspection of Unit 1, the slower unit, I noticed what seemed to me to be a somewhat excessive amount of oil on the bottom and lower edges of the frame. Using great care I cleaned the oil from the frame, frame power wipers and truck side frame power contacts. I then reran the test routine on Unit 1 and there was some improvement in the performance.
Unit 1 Forward 26 seconds Reverse 25 seconds
What does it all mean...
Unit 2 and 3 will become the road power and Unit 1 will be the yard power. Could all three be operated together? Yes. However, I prefer to operate the two closer speed matched units as my road power. I’ll recheck the unit’s performance from time to time and I’ll be sure to post if there are any significant changes.
Thanks to everyone for your input and advice.
Regards, Cliff
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Post by boxcarwilly on Sept 21, 2013 15:31:15 GMT -5
Cliff:
As you know from reading this thread I had this problem with my 3 GP-38's. I did much of the testing as you did and even sent the last one I bought back to AZL for analysis. Long story short, while the basic problem hasn't completely been solved, and because one of my 38's has a different livery then the other two and therefore runs on a separate line, I decided that the slowest of the 38's, ie; the last one would be the one that runs on one of line and the two faster one's would be on the other line. To do this I had to swap shells of one faster with the slower. I all works fine now. As you did, I did all the testing but did not do the time test. This was a big mistake I think. However, Mark brought up a very good point. It's possible that the first two 38's were running far above AZL's specs. as far as speed and the third was either right on or slightly below their specs. This was the only logical way I could solve my problem and keep my sanity. In your case though, if all three are of the same livery, try lashing up your slow poke to the speeders. As I do with many of my engines, AZL and MTL alike, the slower engine will naturally bring the overall speed of your faster engines down. It's sort of acting like a brake for the other two. I do this with my SD75's. Works like a charm so far.
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