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Post by railfan4life on Sept 12, 2016 18:33:22 GMT -8
Guys,
Here's the link to my new review of Intermountain's HO scale Citirail ES44AC GEVO. The engine is equipped with a LokSound select DCC sound decoder. Overall, I found the a great looking and running engine. The silver, blue and yellow paint scheme is very striking and gives a nice break to the constant parade of Armour yellow and BNSF orange. I found the pulling power of the engine was really good on a level mainline, but was less than expected on a 2% grade.
Hope you enjoy the video.
Cheers,
Kevin
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Post by SD90 on Sept 12, 2016 18:55:01 GMT -8
Thanks for the review!
WOW, 57 cars on the flat is great, but only 11 up a 2% grade?
The grade sure takes it's toll!
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Post by edwardsutorik on Sept 13, 2016 8:18:23 GMT -8
WOW, 57 cars on the flat is great, but only 11 up a 2% grade? The grade sure takes it's toll! And more, it seems. A quick internet search says that a 2% grade typically cuts pulling power VERY ROUGHLY in half. Which 11/57 isn't. I wonder what's going on with this strange ratio. Ed |
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Post by Spikre on Sept 13, 2016 8:45:17 GMT -8
?? is this unit still using that Mabuchi based can motor ? that could be a part of the problem. or the unit is just too heavy for the motor and grades ? Spikre  |
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Post by Deleted on Sept 13, 2016 8:45:30 GMT -8
I thought Intermountain fixed their motor problems? Guess not?
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Post by NS4122 on Sept 13, 2016 8:54:43 GMT -8
All the models in this latest release have the new motors. I have two BNSF ES44AC's from this run and they pull significantly better than the first run.
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Post by Brakie on Sept 13, 2016 9:02:52 GMT -8
I thought Intermountain fixed their motor problems? Guess not? A 2% grade is a hard pull with the cars trying to do what comes natural-roll down grade while the engine(motor/gears) insist the cars go upgrade. While 11 cars doesn't seem heavy try this.. If you have a 2% grade on your layout then use your fingers on the coupler to pull those 11 cars..You will be surprise at the resistance. You want more fun? Your engine(s) is still fighting gravity as the train starts going down hill-half your train is still resisting because the cars is still coming up grade. |
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Post by canrailfan on Sept 13, 2016 9:11:22 GMT -8
?? is this unit still using that Mabuchi based can motor ? that could be a part of the problem. or the unit is just too heavy for the motor and grades ? Spikre The key question would be did the locomotive's wheels stop turning on the grade (weak motor) or were they still turning (poor traction)? Poor traction could be due to the trucks being 'warped' or the loco just being too light. IM's units are not that heavy, adding extra weight makes them pull better. |
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Post by dharris on Sept 13, 2016 10:16:07 GMT -8
That is a sharp looking paint scheme.
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Post by railfan4life on Sept 13, 2016 11:28:21 GMT -8
?? is this unit still using that Mabuchi based can motor ? that could be a part of the problem. or the unit is just too heavy for the motor and grades ? Spikre The key question would be did the locomotive's wheels stop turning on the grade (weak motor) or were they still turning (poor traction)? Poor traction could be due to the trucks being 'warped' or the loco just being too light. IM's units are not that heavy, adding extra weight makes them pull better. The trucks appear fine and not warped at all. To answer your question on the wheels, they continued to spin which indicates a lack of traction is more of the problem than motor power. The engine could probably have some weight added inside somewhere, but I haven't taken the shell off to see how much extra space there is. Cheers, Kevin |
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Post by railfan4life on Sept 13, 2016 11:30:47 GMT -8
WOW, 57 cars on the flat is great, but only 11 up a 2% grade? The grade sure takes it's toll! And more, it seems. A quick internet search says that a 2% grade typically cuts pulling power VERY ROUGHLY in half. Which 11/57 isn't. I wonder what's going on with this strange ratio. Ed I think this is due to lack of tractive effort (wheel slip) more than motor performance. Probably adding weight would increase the pulling power on grades. I always run with multiple units though so I might not mess with it. Cheers, Kevin |
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Post by railfan4life on Sept 13, 2016 11:32:59 GMT -8
I thought Intermountain fixed their motor problems? Guess not? I think this has more to due with the weight of the engine than a problem with the motor. Cheers, Kevin |
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Post by edwardsutorik on Sept 13, 2016 13:27:20 GMT -8
And more, it seems. A quick internet search says that a 2% grade typically cuts pulling power VERY ROUGHLY in half. Which 11/57 isn't. I wonder what's going on with this strange ratio. Ed I think this is due to lack of tractive effort (wheel slip) more than motor performance. Probably adding weight would increase the pulling power on grades. I always run with multiple units though so I might not mess with it. Cheers, Kevin I'm not seeing that. The loco had GREAT tractive effort on the flat. Why would it suddenly evaporate on a 2% grade? It didn't on the locos I was looking at. For them, train length was cut to one half--not 20%. Ed |
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Post by Brakie on Sept 13, 2016 14:14:03 GMT -8
Ed, Try the coupler pull test like I mention.. It open my eyes to why 2 Athearn GP38-2s was stalling with 18 car train going up a 2% grade at the club. These cars wasn't weigh to RP20.1
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Post by railfan4life on Sept 13, 2016 14:15:59 GMT -8
I think this is due to lack of tractive effort (wheel slip) more than motor performance. Probably adding weight would increase the pulling power on grades. I always run with multiple units though so I might not mess with it. Cheers, Kevin I'm not seeing that. The loco had GREAT tractive effort on the flat. Why would it suddenly evaporate on a 2% grade? It didn't on the locos I was looking at. For them, train length was cut to one half--not 20%. Ed I think it depends on how free rolling the rolling stock are. In John Armstrong's book Track Planning for Realistic Operation he covers this a bit in chapter 5 and figure 5-11. The book says average rolling stock will cut a engine's pulling power by about 65% on a 2% grade. "Extremely" [his words] free rolling rolling stock on a 2% grade will cut the pulling power by 80%. These are his calculations and I haven't tested them at all to see if they are accurate, but he was pretty much right about everything else involving track planning. At the end of the day, I can only say what I observed in my test with this engine. Cheers, Kevin |
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Post by SD90 on Sept 13, 2016 14:20:13 GMT -8
I've heard that intermountain locomotives are VERY light, they need more weight to pull good.
I wouldn't have thought it would make that much difference between flat and a grade though.
Still it's a nice looking engine.
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Post by llxlocomotives on Sept 13, 2016 14:29:13 GMT -8
I haven't finished the video, so if you answered some of this bear with me. How heavy are the cars? Normally when people are making these comparisons, they are using 4 ounce cars. Heavier cas will increase the resistance on grades faster.
The loco wheels may also be the culprit. The polished wheels that are favored reduce the coefficient of friction by as much as 20 percent.
Overall curvature of the track will also impact this result. Curves add resistance. Inversely proportional to the radius of curvature.
Finally, where you are relative to the adhesion line also matters on this ratio. The largest draw bar force occurs near the wheel slip point. Most of the ratios people talk about are both at this slip point. The unit might pull more at a lower power setting.
I find defining the actual draw bar force to be difficult. There are a lot of factors that come into play. Here you probably need some history on how various models pull this same grade. What I have seen is interesting, good review.
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Post by scl1234 on Sept 13, 2016 14:43:00 GMT -8
... The loco wheels may also be the culprit. The polished wheels that are favored reduce the coefficient of friction by as much as 20 percent. I was about to ask whether Intermountain locomotives use solid Nickel Silver wheelsets or some other Chrome/Nickel plated metal... |
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Post by edwardsutorik on Sept 13, 2016 15:11:21 GMT -8
I think it depends on how free rolling the rolling stock are. In John Armstrong's book Track Planning for Realistic Operation he covers this a bit in chapter 5 and figure 5-11. The book says average rolling stock will cut a engine's pulling power by about 65% on a 2% grade. "Extremely" [his words] free rolling rolling stock on a 2% grade will cut the pulling power by 80%. These are his calculations and I haven't tested them at all to see if they are accurate, but he was pretty much right about everything else involving track planning. At the end of the day, I can only say what I observed in my test with this engine. Cheers, Kevin Thinkin' on that, it does make sense. If you had INCREDIBLY free-rolling trucks, maybe you could pull 200 cars on the flat. But when you've got to lift those cars vertically 'cause you're on a grade, free-rolling doesn't do a lot for you. I think I'll disagree with the wording like "will cut the pulling power by 80%". The pulling power is the same no matter whether you've got free-rolling trucks or old un-oiled trucks from the fifties. I think it's the reverse: free rolling trucks will allow you to pull MORE on the flats than badly rolling trucks. Goin' up the hill, they kinda sorta match up. Here's a thought experiment: Let's suppose we take those cars with the free-rolling trucks and triple their weights. What'll happen on the flat? What'll happen on the grade? I predict that the loco will still haul close to 57 cars. But when it hits the grade, I think it'll be more like 4, instead of 11. Yup, Kevin, I think you've got the explanation! Ed |
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Post by Deleted on Sept 13, 2016 16:17:03 GMT -8
I guess the real question then, is how does this engine perform compared to others?
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Post by railfan4life on Sept 13, 2016 16:29:39 GMT -8
I think it depends on how free rolling the rolling stock are. In John Armstrong's book Track Planning for Realistic Operation he covers this a bit in chapter 5 and figure 5-11. The book says average rolling stock will cut a engine's pulling power by about 65% on a 2% grade. "Extremely" [his words] free rolling rolling stock on a 2% grade will cut the pulling power by 80%. These are his calculations and I haven't tested them at all to see if they are accurate, but he was pretty much right about everything else involving track planning. At the end of the day, I can only say what I observed in my test with this engine. Cheers, Kevin Thinkin' on that, it does make sense. If you had INCREDIBLY free-rolling trucks, maybe you could pull 200 cars on the flat. But when you've got to lift those cars vertically 'cause you're on a grade, free-rolling doesn't do a lot for you. I think I'll disagree with the wording like "will cut the pulling power by 80%". The pulling power is the same no matter whether you've got free-rolling trucks or old un-oiled trucks from the fifties. I think it's the reverse: free rolling trucks will allow you to pull MORE on the flats than badly rolling trucks. Goin' up the hill, they kinda sorta match up. Here's a thought experiment: Let's suppose we take those cars with the free-rolling trucks and triple their weights. What'll happen on the flat? What'll happen on the grade? I predict that the loco will still haul close to 57 cars. But when it hits the grade, I think it'll be more like 4, instead of 11. Yup, Kevin, I think you've got the explanation! Ed Ed, Agree that my wording/paraphrasing of John Armstrong probably wasn't as precise as it should have been. I think your wording is better. Pulling power is the same, but how many cars a given amount of pulling power can pull up a grade gets reduced. Cheers, Kevin |
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Post by gasmith on Oct 8, 2016 23:19:54 GMT -8
Ed, Try the coupler pull test like I mention.. It open my eyes to why 2 Athearn GP38-2s was stalling with 18 car train going up a 2% grade at the club. These cars wasn't weigh to RP20.1 IMHO RP20 weight is too heavy. As long as a car has enough weight to stay on the track I'm good with it. |
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Post by Brakie on Oct 9, 2016 3:15:35 GMT -8
Ed, Try the coupler pull test like I mention.. It open my eyes to why 2 Athearn GP38-2s was stalling with 18 car train going up a 2% grade at the club. These cars wasn't weigh to RP20.1 IMHO RP20 weight is too heavy. As long as a car has enough weight to stay on the track I'm good with it. I fully agree..RP20.1 was needed in the days of wooden car kits,trucks with oversized flanges and light plastic cars. |
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Post by calzephyr on Oct 10, 2016 5:50:18 GMT -8
Kevin
Thanks for the review and close up pictures of a nice looking model. The handrails seem to be less than straight but they can usually be worked on.
Since Curves and other factors influence the pulling power on a grade, how do actual tests of other models say Athearn or Kato units in general compare on your 2% grade with eleven or more cars??
The ratio of 57 down to 11 may be due to weight of the loco or the type of surface of the metal wheels. The pulling power could change with wear on the surface of the drive wheels also and can increase or decrease with use. Curves and other factors also influence the pulling power on a grade.
Larry
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