My theory is, which is mine, is that all brontosauruses are thin at one end, get much thicker in the middle, and are thin again at the other end. Doug
Great test and conclusion, good sir! Do have one question, perhaps Moose missed where you mentioned it (highly likely), but do you recall the % grade you tested? Although this moose understands and accepts your conclusion, it still be fun to measure the pulling power as you had done. If Moose only had a measuring do-hicky...
Now, if only you could go back and do it on different radius curves, both flat & on grades mind you, then the test would be truly complete! Of course, the conclusion would still be the same...
My my. Science or math? Tell me moose. Scale down the weight of a common 484 northern to n scale. Lol. Do we have strong enough layout frames? Sent from my SM-G975U using Tapatalk
Moose'll get right on it, good sir! ... ... ... Wait, what?! Moose was arguing against comparing 1:1 to 1:160 in this way? Dag'gum'it, now you've gone and done it - got poor moose brain in a knot... Groan...
I have doubts about using something like this because the loco can't move. You are measuring the pulling power of a loco whose wheels are slipping, but from driving on snow and ice I know that once your wheels slip you lose a lot of traction.
The scale I use freezes at the highest weight. Once the wheels start slipping and the weight decreases you still have the reading at the highest mark....
The Atlas GP7 photos are relevant to some work I have been doing lately, so i thought I would share. My current club layout (The Midwestern N Pioneer in Chicago suburbs) has two helices and some other grades that are over 2%. I have some Atlas SD7 and GP7 that I've not used much due to poor pulling power on these grades. Well I thought I would do something about it. So I added some sheet lead to the empty spaces, using kapton tape to ensure no shorting of the frame halves. IMG_20210406_172542 by jbonkowski posted Apr 6, 2021 at 5:36 PM I didn't do an entirely clean test, but before modifying, two SD7 would pull 15 40' boxcars up the helix. After modifying one engine with the sheet lead, the pair pulled 22 cars, so 7 more. This is effectively a doubling of the pulling power of the single modified engine. I just modified the other one so I will soon know if I got the pulling power of the pair up to ~30 cars. This was easy to do, and the improvement in pulling power is significant, more than I was expecting. I assume the Atlas frame designers were worried about potentially tall components on the DCC board (Digitrax in this case), removing a lot of frame metal. I also cleaned up the 15 years of oxidization on the brass pickup strips bringing power from the trucks to the frame halves. Jim
Do you have any idea how much you added. With the radius, the effective grade was likely greater than 3%. The curve adds resistance roughly equal to a little more than a percent of grade. I would guess you added between one to two ounces for seven cars. The weight benefit depends on the motor charactistics. I have seen that if you add two equal increments one at a time, the number of car increase is roughly 1.5 times the first. This won't go on forever and it depends on how hard the motor is working in the first place, but I had seen it on several tests.
Lol. Its crazy heavy. Not sure why we're putting all this math into it. I suppose an someone with a degree in engineering can't resist. I still find that well balanced weight on the drivers. With proper placement of at least 2 traction bands. And a fair amount of weigh. Makes a Loco and his owner happy. I believe that math by the way is alot of tonnage on a layout.. Sent from my SM-G975U using Tapatalk
I've never seen or heard of an N scale locomotive's electric motor "stalling" due to lack of capacity. Have you? It's always wheels spinning. btw: your link appears dead Larry.
I have seen applications where the motor could not spin the wheels. That is the unusual case. I recently finished a design of experiments on fifteen motors, six engines, three weight increments, & three wheel configurations. The pulling capacity difference across the motors was as large as the weight increase. In every case, wheel slip occurred. In most cases the engine could pull additional cars with the wheels spinning. How many & the speed that it maintained was impacted by the three primary variables. This study was done with HO models, but the physics will be the same for N scale engines. http://www.llxlocomotives.com/?p=2439 The car numbers that have been referred to in posts in this discussion fall short of those that were seen in the study. This has peaked my interest in the N scale situation. I have recently put my personal focus here because of space limitations. In a limited manner I will do some similar examinations on my engines in this scale. Part of it is natural curiosity and part is because I spent 40 year working with gas turbine engine performance. Before I get into that, I will be determining the nominal best rolling freight car. Then creating a train of 35 or 40 of these cars. One more thing, weight will scale by the change in volume. That means it would be 160 cubed. Thus a 230,000 pound F7A would weigh around 11 ounces in N scale. Not far off of what they weigh. Perhaps the stresses and material mechanics are as well.
So there's potentially another factor that could come into play that lies somewhere between wheel slip and outright motor stall, which is splitting the worm shaft doughnut that's found on some N scale locos. This would potentially result in no wheel slip and no motor stall. ...also, because I sometimes can't tell if people are joking or not when posting, we all know that weight doesn't scale like size does, right?
As the song from the movie Grease goes. “Tell me more tell me more!” Sent from my iPhone using Tapatalk
