John-NYBW I have a fairly large basement layout. My steepest uphill grade is 1.5% while the downhill grade is 1.75%. I generally limit my freight cars to 20 cars but early on I tried to see if I could run a 50 car freight. The couplers held up with no problem. The operational problem I had is there is a curve near the bottom of the grade and I superelevated it slightly. I found that all that weight tended to pull the cars over the inside rail. The other problem is a train that long dwarfs the layout. The locos on the front end would pass through a town while the caboose had yet to reach the town behind it. I've since reduced the amount of superelevation so the rails are near level on that curve so I might try the experiment again just to see if I get better results, but 20 car freight will continue to be the max. My freelanced layout is loosely based on the NYO&W and 20-30 car freights were not unusual on that line. That's probably why it went belly up.
I have a fairly large basement layout. My steepest uphill grade is 1.5% while the downhill grade is 1.75%. I generally limit my freight cars to 20 cars but early on I tried to see if I could run a 50 car freight. The couplers held up with no problem. The operational problem I had is there is a curve near the bottom of the grade and I superelevated it slightly. I found that all that weight tended to pull the cars over the inside rail.
The other problem is a train that long dwarfs the layout. The locos on the front end would pass through a town while the caboose had yet to reach the town behind it.
I've since reduced the amount of superelevation so the rails are near level on that curve so I might try the experiment again just to see if I get better results, but 20 car freight will continue to be the max. My freelanced layout is loosely based on the NYO&W and 20-30 car freights were not unusual on that line. That's probably why it went belly up.
John,
The way to prevent long trains from "dwarfing the layout" is to rethink your approach to layout design.
In a moderately large, or even medium sized space, rather than trying to model multiple "towns", which are then heavily selectively compressed, and too close to each other, you can just model one town, model it on a grander scale, with less compression, then model a few miles of open country on either side, some interchanges and junctions, all leading to lots of staging.
Move all the other "towns" off stage, or nearly so.
Now your long trains will look properly proportioned to the scenes. And you will capture more of the "immensity" of the prototype.
My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside. The entire area behind the freight yard will be urban scenery, the rest will be suburban and rural scenery.
A single 25' long freight yard is easier and less expensive to build than two 12' long ones at each end of a layout, and is way more realistic looking.
Use this rule, model each feature only once, and model it bigger and better.
Just a thought.
To my eye, trains look like the local wayfreight until you get up around 35-40 cars. Then they start to look like mainline trains.
The average train on my layout will require 3-4 diesels, or two moderate size steam locos. Some will require more or bigger power.
Sheldon
Lastspikemike Just to remind everyone that the rails (and roadbed) hold up the weight. The coupler, and indeed the locomotive moving the train, only overcome the rolling resistance not the total weight of the train. Indeed, the whole secret to the load carrying capacity of railroads is the low deflection of the rail and roadbed. Once the initial static friction is overcome, rolling resistance becomes quite low and not meaningfully related to train weight. Any force will accelerate any mass absent friction. Eventually you'll notice the mass moving....
Just to remind everyone that the rails (and roadbed) hold up the weight. The coupler, and indeed the locomotive moving the train, only overcome the rolling resistance not the total weight of the train.
Indeed, the whole secret to the load carrying capacity of railroads is the low deflection of the rail and roadbed.
Once the initial static friction is overcome, rolling resistance becomes quite low and not meaningfully related to train weight.
Any force will accelerate any mass absent friction. Eventually you'll notice the mass moving....
You are neglecting the effect of gravity on a grade. It is substantial. See Al Krug's article on locomotive horsepower and what it takes to ascend a grade with trailing tonnage. Just as a quick reference, for every 0.5% grade increase, it takes approximately 3.2 X the initial horsepower to ascend if maintaining the same track speed. If you are willing to slow substantially, you can get away with generating less tractive effort/horsepower.
The couplers each have to withstand the draw forces on them. Longer trains, or more horsepower stretching them, things start to break. Why else do we have 'distributed power' on trains going over mountain passes? It's to save the crew from having to walk back with a 70 pound knuckle and replace it.
ATLANTIC CENTRALMy new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside.
-Matt
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
crossthedog ATLANTIC CENTRAL My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside. @Sheldon, my folks both sprang out of Maryland, my mom from Pikesville and my dad from Reisterstown. The history of my dad's family is all around Taneytown, Frizzelberg, Mayberry, Uniontown. When I'm in Carroll County, I can't swing a dead cat without hitting a dead relative's gravestone. My mom fondly remembers running to the end of her street as a girl to see the WM steam locomotives chuffing through the ravine on their way out of Bawlmer to points north and west. -Matt
ATLANTIC CENTRAL My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside.
@Sheldon, my folks both sprang out of Maryland, my mom from Pikesville and my dad from Reisterstown. The history of my dad's family is all around Taneytown, Frizzelberg, Mayberry, Uniontown. When I'm in Carroll County, I can't swing a dead cat without hitting a dead relative's gravestone. My mom fondly remembers running to the end of her street as a girl to see the WM steam locomotives chuffing through the ravine on their way out of Bawlmer to points north and west.
I'm originally from Anne Arundel County, now in Harford County for the last 26 years. But being a life long Marylander who has traveled all over the state to work construction, I know all those places you mentioned pretty well.
I grew up in Severna Park, where I was lucky enough to be a member of the Severna Park Model Railroad Club, once again recently featured in Model Railroader.
And while the new layout freelanced, there is a direct effort to give it the feel of the western/northern counties. While no effort is made to model exact places, the place names are taken from the region with some "association" with the real places.
ATLANTIC CENTRAL John-NYBW I have a fairly large basement layout. My steepest uphill grade is 1.5% while the downhill grade is 1.75%. I generally limit my freight cars to 20 cars but early on I tried to see if I could run a 50 car freight. The couplers held up with no problem. The operational problem I had is there is a curve near the bottom of the grade and I superelevated it slightly. I found that all that weight tended to pull the cars over the inside rail. The other problem is a train that long dwarfs the layout. The locos on the front end would pass through a town while the caboose had yet to reach the town behind it. I've since reduced the amount of superelevation so the rails are near level on that curve so I might try the experiment again just to see if I get better results, but 20 car freight will continue to be the max. My freelanced layout is loosely based on the NYO&W and 20-30 car freights were not unusual on that line. That's probably why it went belly up. John, The way to prevent long trains from "dwarfing the layout" is to rethink your approach to layout design. In a moderately large, or even medium sized space, rather than trying to model multiple "towns", which are then heavily selectively compressed, and too close to each other, you can just model one town, model it on a grander scale, with less compression, then model a few miles of open country on either side, some interchanges and junctions, all leading to lots of staging. Move all the other "towns" off stage, or nearly so. Now your long trains will look properly proportioned to the scenes. And you will capture more of the "immensity" of the prototype. My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside. The entire area behind the freight yard will be urban scenery, the rest will be suburban and rural scenery. A single 25' long freight yard is easier and less expensive to build than two 12' long ones at each end of a layout, and is way more realistic looking. Use this rule, model each feature only once, and model it bigger and better. Just a thought. To my eye, trains look like the local wayfreight until you get up around 35-40 cars. Then they start to look like mainline trains. The average train on my layout will require 3-4 diesels, or two moderate size steam locos. Some will require more or bigger power. Sheldon
Everything in this hobby is a tradeoff. Having multiple towns increases operational possibilities while fewer towns allows for more longer open country runs. I've been building my layout for the last 20 years and it's a little late to be rethinking the layout design. I have one large city and two smaller towns on the mainline with staging yards at either end. I think that strikes a good balance. My towns have a decent amount of distance between them. I could eliminate the middle town to create a longer open country run but I prefer having one more place where my passenger trains stop and my local freight has some switching to do.
Just outside my main city is my large classification yard. It has a 12 track ladder with the longest track being 25 feet. I designed it with the idea of maybe running 50 car freights but when I saw what that looked like, I decided it was just too much. 20 car freights look plenty long in my space. On rare occasions I might even stretch it out to 25. My freights generally run a single steamer or an AB set of F units. I have one ABB set for my fast freight but one of the units requires repair so right now it is also an AB set. I have lots of passenger trains, probably too many, and they are pulled by a variety of equipment from AB E units to RS-1s on the commuter trains. I have several streamlined Hudsons as well.
As for compressing the towns, I don't feel I've done that at all. All three have backdrops which make them seem much larger than they actually are especially my largest city which is about 12 feet long but has a backdrop running the full length and gives it a lot of depth. To enter the staging yard, my trains pass under a mirror which doubles the apparent size of the city as well as the structures that butt up against it.
John-NYBW Everything in this hobby is a tradeoff. Having multiple towns increases operational possibilities while fewer towns allows for more longer open country runs. I've been building my layout for the last 20 years and it's a little late to be rethinking the layout design. I have one large city and two smaller towns on the mainline with staging yards at either end. I think that strikes a good balance. My towns have a decent amount of distance between them. I could eliminate the middle town to create a longer open country run but I prefer having one more place where my passenger trains stop and my local freight has some switching to do. Just outside my main city is my large classification yard. It has a 12 track ladder with the longest track being 25 feet. I designed it with the idea of maybe running 50 car freights but when I saw what that looked like, I decided it was just too much. 20 car freights look plenty long in my space. On rare occasions I might even stretch it out to 25. My freights generally run a single steamer or an AB set of F units. I have one ABB set for my fast freight but one of the units requires repair so right now it is also an AB set. I have lots of passenger trains, probably too many, and they are pulled by a variety of equipment from AB E units to RS-1s on the commuter trains. I have several streamlined Hudsons as well. As for compressing the towns, I don't feel I've done that at all. All three have backdrops which make them seem much larger than they actually are especially my largest city which is about 12 feet long but has a backdrop running the full length and gives it a lot of depth. To enter the staging yard, my trains pass under a mirror which doubles the apparent size of the city as well as the structures that butt up against it.
John, I would not disagree with any of that and your layout sounds very nice.
I think the biggest difference is I took almost all the industries off the mainline, and put them on industrial branch lines or belt lines, mostly in the one city modeled.
There are a few more remote industries out on the main, but there are four separate industial areas all associated with the main yard and city, two do not require even going on or across the main for operations, one is on the main, the other only requires crossing the main.
So by the standards most layouts are built to, that is four "towns" worth of industries, and four local trains that have little effect on what is happening on the mainline.
I don't expect to run many trains larger than 40 or 50 cars, but for my eye that is large enough to require three and four unit diesel lashups, and doublehead lots of steam, especially in a region that is in the piedmont, leading to the mountains.
My staging is all thru staging, the mainline is continious double track, which also helps improve the appearence of long trains - no worrying about siding length vs distance between sidings.
According to Sam at Kadee their couplers are made of pure zinc.
I had a Kadee coupler fail one time. I was running about 50 cars down a 2% grade when a truck screw near the rear of the train worked its way out. It got caught in a switch frog and brought the train to a sudden stop, at least that part of the train behind the knuckle that snapped.
Real trains can break more than one coupler at the same time. If the brakes apply suddenly on the rear of the train a group of cars can break off while the rest keeps moving. When enough braking force builds up on what's left another section can separate. This can repeat a number of times. I heard of one instance where four knuckles were broken.
Mismatched coupler heights are the cause of most model train separations which can lead to frightening runaways on grades. I saw this happen once on a live steam operation. The size of that equipment can lead to serious injury or even death in the resulting pileup. Some of that equipment has safety chains between the cars like older prototype passenger car used to have.
Mark
ATLANTIC CENTRAL John-NYBW Everything in this hobby is a tradeoff. Having multiple towns increases operational possibilities while fewer towns allows for more longer open country runs. I've been building my layout for the last 20 years and it's a little late to be rethinking the layout design. I have one large city and two smaller towns on the mainline with staging yards at either end. I think that strikes a good balance. My towns have a decent amount of distance between them. I could eliminate the middle town to create a longer open country run but I prefer having one more place where my passenger trains stop and my local freight has some switching to do. Just outside my main city is my large classification yard. It has a 12 track ladder with the longest track being 25 feet. I designed it with the idea of maybe running 50 car freights but when I saw what that looked like, I decided it was just too much. 20 car freights look plenty long in my space. On rare occasions I might even stretch it out to 25. My freights generally run a single steamer or an AB set of F units. I have one ABB set for my fast freight but one of the units requires repair so right now it is also an AB set. I have lots of passenger trains, probably too many, and they are pulled by a variety of equipment from AB E units to RS-1s on the commuter trains. I have several streamlined Hudsons as well. As for compressing the towns, I don't feel I've done that at all. All three have backdrops which make them seem much larger than they actually are especially my largest city which is about 12 feet long but has a backdrop running the full length and gives it a lot of depth. To enter the staging yard, my trains pass under a mirror which doubles the apparent size of the city as well as the structures that butt up against it. John, I would not disagree with any of that and your layout sounds very nice. I think the biggest difference is I took almost all the industries off the mainline, and put them on industrial branch lines or belt lines, mostly in the one city modeled. There are a few more remote industries out on the main, but there are four separate industial areas all associated with the main yard and city, two do not require even going on or across the main for operations, one is on the main, the other only requires crossing the main. So by the standards most layouts are built to, that is four "towns" worth of industries, and four local trains that have little effect on what is happening on the mainline. I don't expect to run many trains larger than 40 or 50 cars, but for my eye that is large enough to require three and four unit diesel lashups, and doublehead lots of steam, especially in a region that is in the piedmont, leading to the mountains. My staging is all thru staging, the mainline is continious double track, which also helps improve the appearence of long trains - no worrying about siding length vs distance between sidings. Sheldon
I have industrial belt lines that run on both sides of the track between my classification yard and main city. It provides ample opportunities for switching. I think my favorite job though is the wayfreight which serves the other two towns and then continues on into staging to theoretically serve more. The middle of the three towns is the smallest and has only two industries to serve. Just before reaching the last of the three towns, there is a dummy interchange which serves as a universal industry. Within the last town are 3 industries as well as an interchange with a short line that is currently under construction. There is a small yard there to handle the interchange traffic with the short line which hopefully will soon be operational.
Although I designed my yard with an A/D track that can handle 50+ car trains, from a practical stand point, 20 cars is the typical manifest freight. I use a car card/waybill system and occasionally that results in trains a bit longer but I can't ever remember going over 25 cars during normal operations. A 20-25 car train looks plenty long in HO. It's more than my eye can take in at once which makes it seem longer than it actually is.
Lastspikemike A 2% grade doesn't add much force to the couplers. Particularly model train couplers. But the maths is easy enough if someone wants to do the work. The OP postulated a 2% grade which someone pointed out as if it makes a difference to the issue of coupler failure. It doesn't and cannot. The total maximum force the locomotive can exert declines by exactly the same proportion. The grade isn't relevant to the underlying conceptual question actually posed. If a model locomotive can successfully move a train on the level without breaking any coupling links then it can haul that same train up a grade without breaking those same links. At least that would be my guess, not having done the maths. The underlying conceptual question, as yet not clearly identified, is can a model locomotive or consist of model locomotives exert enough force to break a model train apart? If so, what is the likely failure point?
A 2% grade doesn't add much force to the couplers. Particularly model train couplers. But the maths is easy enough if someone wants to do the work.
The OP postulated a 2% grade which someone pointed out as if it makes a difference to the issue of coupler failure. It doesn't and cannot. The total maximum force the locomotive can exert declines by exactly the same proportion.
The grade isn't relevant to the underlying conceptual question actually posed. If a model locomotive can successfully move a train on the level without breaking any coupling links then it can haul that same train up a grade without breaking those same links. At least that would be my guess, not having done the maths.
The underlying conceptual question, as yet not clearly identified, is can a model locomotive or consist of model locomotives exert enough force to break a model train apart? If so, what is the likely failure point?
I completely disagree with your premise and conclusions.
I am a practicing, licensed professional civil engineer (which means I don't just do the work but am responsbile for the plans; I sign and seal them, and can then be sued if something is wrong).
While it may appear on the surface that a 2% grade does not increase the mass or weight all that much, you are completely neglecting the affects of metal wheel on metal rail friction, which adds an "effective" increase to the weight of any train (and the force on couplers), which in real life, with 10,000+ ton trains on a 2% grade like Cajon Pass, becomes very significant. This is why some above commented that grade DOES affect pulling power. You are increasing the EFFECTIVE weight as the grade increases. You also are dramatically increasing the effective weight that must be braked on the downgrade due to acceleration of the train pushing on the engines.
Additionally, any horizontal curvature at all also increases friction drag between the wheel flanges and the rail. In real life there are mathematical equations that can estimate the increased friction based upon horizontal curvature.
Real railroads do the math and then assign maximum tonnages allowed over a division, and it varied quite a bit based upon the grade and horizontal curvature.
Drawbars are more likely to break with slack run in and run out forces if train movement is not carefully controlled.
Even in the model world, poor rolling wheelsets dramatically increase the pulling forces on the couplers in long trains because they dramatically increase friction forces. Most Kadee couplers are not going to fail barring a manufacturing defect, but plastic ones may.
The free-rolling qualities of the rolling stock being pulled can make a tremendous difference in what one's engines are able to pull. When non-free-rolling freight cars are in a train, they dramatically increase the drawbar pull required to move the train. It is not even the weight issue so much as the friction issue. Just try pulling an 80 car train by the coupler only using two fingers. The cars may not weigh much but there's an awful lot of friction to overcome.
In most cases, the model engines will fail to move the model train well before the metal couplers break. This is because the pulling power of the engines is more the limiting factor than the couplers.
I'm not even going to try scaling down equations to HO. There are too many variables in the model world that can affect train performance.
PRR8259, thank you for that excellent contribution. I took high school physics but that was it, you gave us food for thought presenting more variables than I would have thought of or considered. Now if Lastspikemike will bring forth his simple enough math I may be even more informed, or not.
Brent
"All of the world's problems are the result of the difference between how we think and how the world works."
I don't see that broken Kadee couplers could be all that much of an issue. The only ones that I've experienced were on locos or rolling stock that decided to take a face-first closer look at the layout room's concrete floor.
Lastspikemike Just a note to remind all that a 2% grade doesn't add much weight to the force on the couplers. The maths is fairly easy.
Just a note to remind all that a 2% grade doesn't add much weight to the force on the couplers. The maths is fairly easy.
It may not have much influence on the couplers, but it definitely affects the locomotive's pulling abilities.A loco that can handle a heavy train on level track can be "on-it's-knees" on a 2% grade, and there's no need for math, other than perhaps the number "2" or even "3" (representing a 2nd or 3rd locomotive).
BATMAN PRR8259, thank you for that excellent contribution. I took high school physics but that was it, you gave us food for thought presenting more variables than I would have thought of or considered.
I second your "thank you" Brent.
LastspikemikeThe effect of the grade will be to add a small proportion of force from the exertion of gravity on the mass of the train, minus the locomotive mass of course. Grades cannot increase rolling resistance. Curves can but not grades.
Lastspikemike ... Grades cannot increase rolling resistance. Curves can but not grades. ...
... Grades cannot increase rolling resistance. Curves can but not grades.
...
Mike, let us perform a thought experiment. You and I are both standing beside a bench where a 3/4" plywood plank is elevated at one end, the lower resting on the bench surface, such that the elevation constitutes a 2% grade.
I couple two small HO ore jennies together and ask you to grasp the lead coupler and draw the two cars up the incline. I ask you to note the apparent effort. No need to measure it exactly.
Then, I couple sixteen jennies of the same type, all with the same rolling resistance in the wheelsets due to friction and fit, and I ask you to repeat the process. Would you expect to have to exert yourself considerably more to draw all those coupled cars up the grade? I believe you would. That is rolling resistance, and it's due to gravity. If you were to release the lead car, what would happen? The cars would accelerate back down the incline. This is what the engine must contend with. It isn't reasonable to say that gravity doesn't amount to rolling resistance. Otherwise, why have more horsepower? And, if you put a sufficient horsepower on the head end, say six SD-70M at Run 8, and trail them with 20K coupled tons, all but one coupler at 100% designed capacity, the one at 99%, would you expect any breakage? I believe you should, and we both know which it would be in all probability. Now trail the same tonnage, same horsepower, on a 2% grade. Would you expect the one coupler to part even more easily? I believe you should. See - HP vs TE
John-NYBW I have industrial belt lines that run on both sides of the track between my classification yard and main city. It provides ample opportunities for switching. I think my favorite job though is the wayfreight which serves the other two towns and then continues on into staging to theoretically serve more. The middle of the three towns is the smallest and has only two industries to serve. Just before reaching the last of the three towns, there is a dummy interchange which serves as a universal industry. Within the last town are 3 industries as well as an interchange with a short line that is currently under construction. There is a small yard there to handle the interchange traffic with the short line which hopefully will soon be operational. Although I designed my yard with an A/D track that can handle 50+ car trains, from a practical stand point, 20 cars is the typical manifest freight. I use a car card/waybill system and occasionally that results in trains a bit longer but I can't ever remember going over 25 cars during normal operations. A 20-25 car train looks plenty long in HO. It's more than my eye can take in at once which makes it seem longer than it actually is.
John, again your layout sounds very nice and well thought out for operations.
I was simply pointing out that there are ways to run longer trains and not have them overwhelm the layout, even a moderate sized layout.
You are correct, trade offs and compromises, which do you want to make. My choices worked well for me because I like the double track action.
Double track, combined with the "one citiy" theory, does a lot to make the layout feel bigger than it is and make longer trains more at home.
Those choices to do not suit or interest everyone, agreed and understood.
The other "choice" gets back to the idea of having most destinations off the layout, or one the layout. Some really like the idea of seeing the origin/destination of rolling stock both on the layout. For me that is not and issue, as an operator or a viewer.
My passenger operations do include one large thru terminal and five small "suburban" and rural stations to allow good commuter train and "rural local" operation in addition to long distance trains arriving/departing the main terminal.
My goals include the ability to have both advanced opps sessions, and very good high action display running.
Let's try physics. The force you need to pull an object against rolling resistance is
f = m g C(rr)
where m is the mass of the object, g the gravitational constant, and C(rr) the rolling resistance coefficient. The energy (work) needed to pull this object over the distance d is
E = m g C(rr) d
If you have a gradient, you have to put in additional work in form of potential energy, E(p), to get the object up the height h:
E(p) = m g h
For a 2 % gradient, h is obviously 2 % of the distance or 0.02 d, giving
E(p) = 0.02 m g d
m, g, and d are the same in both equations. Thus, the question is how large is C(rr)? According to Wikipedia, the values for (prototype) railroad wheels on steel rails fall between 0.0010 and 0.0024, with a value of 0.0020 given for a railroad passenger car. This means that the energy needed to overcome the 2 % gradient is about 10 times as large as the energy needed to overcome the rolling resistance. This is why railroads need helpers on an incline. Admittedly, I do not know what the C(rr) value for model trains is, but I cannot imagine that it is an order of magnitude larger than for the prototype.
Well, that makes no sense at all. Lots of words just to lead to this incoherent conclusion.
-Kevin
Living the dream.
BATMANFor argument's sake, let's say we are using good Kadee couplers and have a layout with modest 2% ups and downs and 40" radius curves. There are other variables I am probably not including, so how many cars as an average do you think an HO train could have before suffering coupler breaks under the weight?
Look at the nonsense you started Brent.
In conclusion, your question is meaningless in the real world. 2% grades would require a train so heavy to break couplers that it would be nearly impossible to get enough locomotives to pull that hard.
Anyway, there are plenty of YouTube videos of ridiculously long trains and couplers do not break.
A number of years ago, in an issue I cannot find at the moment, MR did a comparison of many of the available HO couplers. As part of this testing they did a test to see how much force was required to break/deform the coupler being tested.
The Kadee coupler could not be tested to failure bcause its strength exceeded the capacity of the testing device.
https://www.youtube.com/watch?v=-hPuNFjRTZA&ab_channel=JamesRisner
I did notice a couple of spots with mid-train helpers.
Not too long ago, I had my three Rapido F units haul a 72 car train away from an area I was working on to keep them away from my troublesome elbows. I parked it with the locomotives just over the crest of a 42' long hill that averages a tad less than 2%. It sat there all day and then whamo! A coupler gave way and the look of horror on my face must have been something as I watch some 70 cars heading for what I surely thought would be the floor. The rate they picked up speed was noteworthy and the actual speed they got to was considerably higher than what I would ever run a train at. In the end, the whole works held fast to the rails with not one derailment.
So, when a long HO scale train is descending a hill with a lot of cars does the engine(s) start bobsledding at some point? If the wheels keep turning what is going on with the motor? is this dynamic braking? Would there be anything disruptive or damaging going on? Would a decoder get confused? What else is going on? Once again my tiny brain wants to know.
https://www.youtube.com/watch?v=PAQUahxY7XY&ab_channel=JamesRisner
BATMANlong HO scale train is descending a hill with a lot of cars does the engine(s) start bobsledding
Russell
For what most home layouts, I'd think a 15-20 consist would operate fine even on a 2% grade behind one loco all with metal couplers.
My cars are 7-8" long because I operate the early 1980s. Correct that I should be fine when behind only loco even going up/down a 2% incline?
I agree with others that an extremely long consist (50+) doesn't look very realistic on many home layouts.
BATMAN So, when a long HO scale train is descending a hill with a lot of cars does the engine(s) start bobsledding at some point? If the wheels keep turning what is going on with the motor? is this dynamic braking? Would there be anything disruptive or damaging going on? Would a decoder get confused? What else is going on? Once again my tiny brain wants to know.
Generally speaking, all other speculation by others aside, if a loco, or group of locos, has the necessary tractive effort to pull the train up the hill, it likely has enough adheasion to hold the train still on the hill.
Are those equations always equal? No. And the protoype pays close attention to that.
But I have never had a string of cars, not even 100 of them in a 2% helix, push a loco down hill faster than the wheels are turning.
I read through the posts and got confused. Some says at a grade the resistance just increases slightly, so the loco can pull more than 2%. On a first look, it makes sense as we only increase 2% of the resistance. But my experience is that most of loco would have hard time to pull if the grade is more than 4%. What's wrong?
So I did some simple math or physics.
Assume the rolling resistance is Crr=0.001 (According to Wiki for metal wheels). Each car is W=4oz. We are pulling N=1000 cars.
On a flat track, the required pulling force is
F=Crr*N*W=0.001*1000*4=4oz
On a track with 2% grade, the required force is
F=Crr*N*W+W*N*G=4+1000*4*0.02=84oz
The second term is the weight contribution to the pulling direction due to the inclined angle.
jlwii2000 tested the recent scaletrain and intermountain ET44AC, the pulling force of these two locos are about 4.9oz and 4.4oz. So let's say a diesel has a pulling force of 4oz. So on a flat track, one loco can pull 1000 cars. But on a 2% grade, you would need 21 locos, or a loco can only pull 50 cars. On a 4% grade, you would need 41 locos, or a loco can only pull 25 4oz cars. The number of locos needed would increase significantly or the number of cars that can be pulled by a single loco would decrease significantly if you consider other factors, such as most cars are heavier than 4oz, 0.001 is actually the lowest number for Crr, you have curves on your track...
On a flat track, the loco only needs to overcome the rolling resistance. But on a graded track, the loco needs to overcome the weight, like DrW said, the potential energy.....
Jerry
Lastspikemike The calculations you performed demonstrate that although the proportion of coupler loading contributed by grade is significant the total added force isn't very much.
The calculations you performed demonstrate that although the proportion of coupler loading contributed by grade is significant the total added force isn't very much.
I am confused. In agreement with my approach via work/energy, the force calculations by Jerry show that a 2 % gradient increases the force needed to pull his hypothetical train from 4 oz to 84 oz. You call this "not very much"? Or do you imply that, in absolute values, 80 oz (the difference between 4 oz and 84 oz) is "not very much"? Have you ever tried if an HO coupler can support a weight of 5 lb?
All this really proves only the phenomenal efficiency of a hard wheel on a hard rail with low bearing resistance. I don't expect to see anyone running a THOUSAND CARS up a continuous 2% any time soon... did anyone bother to reality-check that little detail? Of course the resistance goes through the roof with even slight gravity... look at the trailing weight! (Happens with the prototype, too, with a lot fewer cars in the train... )
84oz seems not unreasonable for pulling about a tenth of a REAL mile of continuous model railroad cars.
LastspikemikeThat was my point. Early railway builders were also canal builders. The rolling resistance of a canal boat increased by a lot when the canal builders included a grade....
That got me thinking of all those paddle wheelers heading up the Fraser to Yale.
Sometimes they had to throw them a rope.
OvermodAll this really proves...
That is not what any of this proves at all.
ATLANTIC CENTRAL The way to prevent long trains from "dwarfing the layout" is to rethink your approach to layout design. In a moderately large, or even medium sized space, rather than trying to model multiple "towns", which are then heavily selectively compressed, and too close to each other, you can just model one town, model it on a grander scale, with less compression, then model a few miles of open country on either side, some interchanges and junctions, all leading to lots of staging. Move all the other "towns" off stage, or nearly so. Now your long trains will look properly proportioned to the scenes. And you will capture more of the "immensity" of the prototype. My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside. The entire area behind the freight yard will be urban scenery, the rest will be suburban and rural scenery. A single 25' long freight yard is easier and less expensive to build than two 12' long ones at each end of a layout, and is way more realistic looking. Use this rule, model each feature only once, and model it bigger and better. Just a thought. To my eye, trains look like the local wayfreight until you get up around 35-40 cars. Then they start to look like mainline trains. The average train on my layout will require 3-4 diesels, or two moderate size steam locos. Some will require more or bigger power. Sheldon
Sheldon: I like your approach to layout design. I intend to do something similar with my main line junction; featuring a full sized yard and interchange, and then running to staging in both directions.
Tin Can II ATLANTIC CENTRAL The way to prevent long trains from "dwarfing the layout" is to rethink your approach to layout design. In a moderately large, or even medium sized space, rather than trying to model multiple "towns", which are then heavily selectively compressed, and too close to each other, you can just model one town, model it on a grander scale, with less compression, then model a few miles of open country on either side, some interchanges and junctions, all leading to lots of staging. Move all the other "towns" off stage, or nearly so. Now your long trains will look properly proportioned to the scenes. And you will capture more of the "immensity" of the prototype. My new layout will model one small western Maryland city, and few of its "suburbs" and nearby countryside. The entire area behind the freight yard will be urban scenery, the rest will be suburban and rural scenery. A single 25' long freight yard is easier and less expensive to build than two 12' long ones at each end of a layout, and is way more realistic looking. Use this rule, model each feature only once, and model it bigger and better. Just a thought. To my eye, trains look like the local wayfreight until you get up around 35-40 cars. Then they start to look like mainline trains. The average train on my layout will require 3-4 diesels, or two moderate size steam locos. Some will require more or bigger power. Sheldon Sheldon: I like your approach to layout design. I intend to do something similar with my main line junction; featuring a full sized yard and interchange, and then running to staging in both directions.
Here is my trackplan, and there is thread on here with more details.
Model train wheels generally (excepting the use of "scale" wheelsets) would actually have a larger width of contact area on the rails than prototype tapered wheelsets do.
This alone will dramatically increase the amount of friction to overcome for a train to move. So it is not possible to scale down prototypical numbers to HO.
Also, although model locomotives running downhill theoretically are braked by the gears, this does not hold true in practice, as the weight of a train behind them can actually push the gears slightly faster. Didn't any of you who are operating long trains ever notice that they actually go a bit faster on downgrades than on the level? It may not be a lot but it definitely occurs.
Do you really mean to tell me that a second engine can't sometimes push the front engine to run faster than it normally does just by itself, despite the gearing? It does happen.
John