Science desk
< January 6	<< Dec \| January \| Feb >>	January 8 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

January 7

Haulin' tonnage

How much power, tractive effort and/or adhesive weight must a locomotive have in order to start and pull one fully-loaded Schnabel car (1) on the level, and (2) on a 1-in-75 grade? 2601:646:8E01:7E0B:0:0:0:64DA (talk) 05:30, 7 January 2018 (UTC)[reply]

An article "New Car Designed to Solve Outsize Shipping Problem" from 1957 states "Besides the transformer weight of 500,000 pounds, a train load of 150,000 pounds pulling and 375,000 pounds buffing was allowed for. Then too, there are the problems of side sway, and stresses on curves."[1] For more information on Schnabel usage see [2] and articles on individual transports [3] [4] [5] [6] [7] [8]. The tractive effort available from a locomotive regardless of its power is limited by its weight on the driven wheels. The List of largest locomotives suggests that multiple locomotives are typically needed to pull a schnabel load, especially on a 1-in-75 grade that effectively adds 1.3% to the pulled mass. Braking distance and a line survey to establish clearances and permissible line load, especially on bridges (see Theodore_Cooper#Coopers_Loading_System) must also be considered. SdrawkcaB99 (talk) 14:15, 7 January 2018 (UTC)[reply]

Suppose we use a Big Boy, Big Blow or DDA40X -- would one of these suffice, at least on the level? 2601:646:8E01:7E0B:0:0:0:64DA (talk) 03:43, 8 January 2018 (UTC)[reply]

Our article mentiones one (supposedly the biggest) as having a maximum mass of 1285.9 tonnes. Friction of that car depends on the bearings and I don't know how much that would be, drag depends on aerodynamics, but shouldn't be much given the low top speed of these cars, and rolling resistance would be about 25 kN (assuming a rolling resistance coefficient of about 0.002). On a 1:75 gradient, gravity adds about M×g/75 = 168 kN, which I expect to be the dominant force acting on the car. So we need a tractive effort from the locomotive of about 250 kN. Most modern mainline locomotives can provide that force, although the margin may not be very large. On dirty track you may need an adhesive weight of well over 100 tonnes, so a single locomotive, not optimised for low-speed goods, may not be able to provide that without proper track cleaning.

The power required is force times speed, so even at 6.7 m/s (the loaded top speed) that amounts to only 1.7 MW, which is doable for even medium sized diesel locomotives. For these oversized loads, power on the overhead wires may have to be cut. Most images of schnabel cars on commons don't show the locomotive, but one that does (a rather small one though) is hauled by a small DB class V 90 diesel-hydraulic locomotive.

Assuming the braking force of the schnabel car can be properly adjusted to its mass, braking distance should be rather short, in particular considering its low speed. Clearance and load are something to consider carefully, as you packed the weight of a normal 600 metre train in just 100 metres. PiusImpavidus (talk) 11:06, 8 January 2018 (UTC)[reply]

Thanks, that's the info I wanted! (BTW, I've done some googling on my own, and saw a video of 2 EMD SD60s pulling a yuge Schnabel car and several other flatcars (both empty and loaded) -- that seems to support what you're saying.) 2601:646:8E01:7E0B:1DAB:D57B:F9C8:4AE0 (talk) 07:42, 9 January 2018 (UTC)[reply]

Increasing exercise capacity

This editorial introduced an interesting idea amid a larger set of weight loss recommendations, with which I'm unfamiliar:

"Third, increasing exercise capacity, or the maximum amount of exercise a person can sustain, works. Specifically, it changes the body so that the survival response¹ is lessened. A person can increase capacity by attending to recovery, the time in between exercise bouts. Recovery interventions, such as food supplements and sleep, lead to increasing capacity and decreasing resistance from the body by reorganizing the biological signaling mechanisms - a process known as retrograde neuroplasticity."

¹:"When a person limits calories, the body slows baseline metabolism to offset the calorie restriction, because it interprets this situation as a threat to survival. If there is less to eat, we'd better conserve our fat and energy stores so we don't die. At the same time, the body sends out surges of hunger hormones that induce food-seeking behavior - creating a real, measurable resistance to this perceived threat of starvation."

Because there are so many unfamiliar ideas in this part, about which we have no articles ("recovery" is a disambiguation but I see no valid target for this), I wanted to see if anyone can cue us in on a good overall presentation of the specifics here to begin with. Wnt (talk) 17:26, 7 January 2018 (UTC)[reply]

"Exercise capacity" is similar to peak power output or VO2 max, and see Human power. Abductive (reasoning) 22:02, 7 January 2018 (UTC)[reply]
"Retrograde neuroplasticity" is a term invented by one publicity-seeking "doctor" who is hawking a book. I will assume that if it appears on Wikipedia that the user is not being a constructive editor. Abductive (reasoning) 22:05, 7 January 2018 (UTC)[reply]
"Recovery" simply refers to the process of healing the body must undergo following stress (such as during strenuous exercise). There's a bit about it in our article on physical exercise; the relevant citation points to this bit from the NIH. Googling exercise recovery nets many hits of greatly varying quality, but you probably get the gist of it. Matt Deres (talk) 01:44, 8 January 2018 (UTC)[reply]

That citation is interesting, but it's about competitive soccer players -- some of the fittest, trimmest, not to mention sexiest guys on the planet. But the quote above is being suggested alongside bariatric surgery, for obese patients not capable of exercising enough to matter for weight loss. Can we generalize in any way from the one to the other? I'd think a mouse model might be more reliable... Wnt (talk) 16:14, 8 January 2018 (UTC)[reply]

Animal models aren't very good for this as humans seem to a large extent to use the same amount of calories, and a large amount of them, whether they do a lot of exercise or not - we're quite a bit different even from the great apes in this respect. Dmcq (talk) 15:19, 12 January 2018 (UTC)[reply]