DoughlessThere isn't much concern about free rolling unless you want to max-out the pulling power of the loco.
That is how I feel.
Sine I can only pull short trains, super-free-rolling can actually be a negative property.
-Kevin
Living the dream.
tstage Maybe we just need to roll with it...
Maybe we just need to roll with it...
Excellent pun!
I was worried how some of my cars were "free rolling" at 2% but others were not. I guess some cars are more easy to move than others. Perhaps they replicate people in this case?
richhotrain Doughless Southgate 2 Just bumping the post. When i saved it, I was in reply mode, and that's what favorites brings up. But, seems there were some recent discussion that this would help with? Dan What contribution did you want to share? Another aspect of "forum culture". Rich
Doughless Southgate 2 Just bumping the post. When i saved it, I was in reply mode, and that's what favorites brings up. But, seems there were some recent discussion that this would help with? Dan What contribution did you want to share?
Southgate 2 Just bumping the post. When i saved it, I was in reply mode, and that's what favorites brings up. But, seems there were some recent discussion that this would help with? Dan What contribution did you want to share?
Just bumping the post. When i saved it, I was in reply mode, and that's what favorites brings up.
But, seems there were some recent discussion that this would help with?
Dan
What contribution did you want to share?
Another aspect of "forum culture".
Rich
There seems to be an oxymoron happening before us.
So we're talking about forum culture in a "free rolling" thread, where the entire complaint registered by the forum culture thread is members not staying within the thread's topic. The bumping of this thread for that reason is validating the complaint lodged by the other thread.
IOW, don't we already have a thread about that?
- Douglas
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Alton Junction
Southgate 2 Just bumping the post. When i saved it, I was in reply mode, and that's what favorites brings up. But, seems there were some recent discussion that this would help with? Dan
cefinkjr The term "free rolling" has been used repeatedly in MR arictles and I thought I had once seen a definition but a search of trains.com just now returned only articles that use the term without an objective definition. My memory says free rolling was once defined as the gradient when a car begins to roll when released. My questions here is, "What is that gradient?" I would think it's somewhere in the neighborhood of 1 or 2 percent. Does anyone have a better number?
The term "free rolling" has been used repeatedly in MR arictles and I thought I had once seen a definition but a search of trains.com just now returned only articles that use the term without an objective definition. My memory says free rolling was once defined as the gradient when a car begins to roll when released. My questions here is, "What is that gradient?" I would think it's somewhere in the neighborhood of 1 or 2 percent. Does anyone have a better number?
IMO, if an objective definition of "free rolling" uses a 1 percent grade as the measure, then either the article was written in, or the author is stuck in, the 1960s; rendering the term pretty useless.
In 2021, most RTR cars will roll on their own on a grade far less. My Atlas Master 4650 3 bay covered hopper will begin to roll as I lift a 2 foot section of track only 1/16th of an inch. About the thickness of a piece of cardstock. (Coke can packaging)
That's about 4/16th over a 100 inch span, or about a 0.25% grade.
Got any better performing (IOW, not free rolling) TYCO wheelsets you can spare?
JaBear SeeYou190 Sorry for the way everyone ignored your request for good information. ??????????????????????????
SeeYou190 Sorry for the way everyone ignored your request for good information.
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Sorry, poor choice of words. I edited the offending post.
SeeYou190Sorry for the way everyone ignored your request for good information.
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
cefinkjr49 (FORTY NINE!) replies to a simple question and only a few actually attempted to answer the question. Makes me sort of glad that the "Receive notifications" option doesn't seem to work.
Yep, starting with the first response it was easy to see where this thread was going, so I stayed away from it.
Sorry for the way <edit> some of us <edit> ignored your request for good information.
I have dealt with this issue, but it was easy to see from your original post that my solution/experience would not be of any help to you.
95% of what followed was just ridiculous.
49 (FORTY NINE!) replies to a simple question and only a few actually attempted to answer the question. Makes me sort of glad that the "Receive notifications" option doesn't seem to work.
The reason for my question was that I'm considering building a new test track for my workbench. The one I've been using for years was once flat but the homosote has gradually warped so that now the track rises at ~.5% in both directions from a permanent magnet uncoupling ramp in the middle.
My new test track is to be built on 3/4" pine or poplar with a grade that's adjustable from 0% to about 3%. Other improvements will be installing at least one rerailer, a bent paper clip hand brake on the adjustable height end (to consistently release the car being tested without unconsciously pushing it into motion) and Kadee coupler gages on both ends, insulated from the test track itself. I'd like to have a remote uncoupler in the middle but can't justify the expense to my management (me).
ChuckAllen, TX
I wasn't planning on replying again, but seems like I need too.
OP asked to define "free-rolling", which a few have done so.
I stated that many are too free-rolling, and that adding weight to the cars helps with switching moves.
I have a small layout, so have zero concern that my locomotives have gone from being able to haul 80 cars to only 50... I cant fit 50 car trains on my layout anyways. (Used hyperbole numbers here, simply to make the point.)
The heavier the car, the more force required to start to move said car from a standstill.
I refuse to get all "science-y" about why. (Yes, it does make perfect sense from a Physics and Science standpoint. E=MC2. I could go further, but why bother with it?)
I will simply state that my practical experience is enough reason for me to adjust the weight heavier.
So, simply put - I have found out that it works better for me and my layout operations style.
No big words needing a dictionary definition to explain it this way.
Ricky W.
HO scale Proto-freelancer.
My Railroad rules:
1: It's my railroad, my rules.
2: It's for having fun and enjoyment.
3: Any objections, consult above rules.
DoughlessI see the chart claiming that "rolling resistance" decreasing as the car moves has to do with inertia, and not what I would call friction on the bearings or "rolling resistance" lessening.
the chart doesnt' show the resistance of a stationary car (0 mph). i don't believe it's the same as at 5 mph
i don't think "inertia" is the reason dynamic friction is < static friction. inertia is the principle that things at rest remain at rest and things in motion, remain in motion, quantified in Newtons equation:
acceleration = mass / force = mass / (tractive effort - resitance)
this equation doesn't describe the speed, just the change in speed, acceleration
i don't understand why the loaded resitance is < the empy resistance. my guess is the coefficient of friction is actually affected by the pressure on the bearings. no doubt it's more complex.
and if the guy (?) who allocate motive power for a train needs to know how much resitance there is, he's interested in that value at speed, hence the charts
DoughlessThings like aerodynamics, gravitational pull on grades, intertia, all impact how "easily something rolls" but that's not the samething as rolling resistance, at least how I think of it.
the resistance chart captures two values, others include gravity on grades and braking
DoughlessIt corroberates my thought that adding weight to a car will keep it staying put as the loco couples up to it because there is more friction on the bearings. Not to mention the greater the inertia
if the resistance is about the same regardless of weight, then it's the inertia, the added mass that requires more force to accelerate the car away from the loco when coupling
some of these concepts are not obvious. nase spent lots fo $$$ to show that a feather and hammer fall at the same speed on the moon without the drag of air resistance
greg - Philadelphia & Reading / Reading
cefinkjrThe term "free rolling" has been used repeatedly in MR arictles
Since the OP is asking about the term as used in Model Railroader magazine (and I have only heard the term used in the context of model - not real - railroading), my answer relates to model trucks.
As far as I know, there never was any gradient testing or other scientific study done to determine what a "free rolling truck" was/is.
In the early years of model railroading, model trucks were basically all metal - cast metal truck sideframes, steel or brass axles, brass or other metal wheels. Unless the axle connection was kept oiled, the trucks tended to roll very poorly...and not all that much better if oiled.
Later on (c. 1970), plastic trucks were developed that were made out of "slippery" Delrin plastic, which allowed the metal axles to spin much more freely than the old-style metal trucks had. These came to be referred to as "free rolling trucks". An engine that could pull 15 cars with old-style trucks could pull like 30-40 cars that all had 'free rolling trucks'.
So "free rolling trucks" is a kinda subjective term, kinda like "DCC ready" or (going way back) "semi-scale".
gregc Doughless The chart shows resistance when the car is in motion and not still, is that right? the chart shows the resistance as speed increases starting from 5 mph Doughless So which is it, does a heavier car create greater or less rolling resistance? probably always more but less than you would think ... ... because friction is the product of the coefficient of friction and the weight, meaning that friction is usually proportional to weight. also, in this cases, the reason for the increase with speed must be (?) due to aerodynamic drag which is usually proportional to the square of velocity
Doughless The chart shows resistance when the car is in motion and not still, is that right?
the chart shows the resistance as speed increases starting from 5 mph
Doughless So which is it, does a heavier car create greater or less rolling resistance?
probably always more but less than you would think ...
... because friction is the product of the coefficient of friction and the weight, meaning that friction is usually proportional to weight.
also, in this cases, the reason for the increase with speed must be (?) due to aerodynamic drag which is usually proportional to the square of velocity
The problem when such topics get expanded into more granular details, what exactly is "rolling resistance"? Narrowly, I would think of it as friction on the bearings.
Things like aerodynamics, gravitational pull on grades, intertia, all impact how "easily something rolls" but that's not the samething as rolling resistance, at least how I think of it.
I would think that weight of the car (gravity, its a Constant ,IIRC) causes more friction on the bearings and thus increases the rolling resistance of the wheels simply by increasing its weight. I don't see how that would lessen if the car is moving, unless it begins to levitate like an airplane......
It corroberates my thought that adding weight to a car will keep it staying put as the loco couples up to it because there is more friction on the bearings. Not to mention the greater the inertia.
I see the chart claiming that "rolling resistance" decreasing as the car moves has to do with inertia, and not what I would call friction on the bearings or "rolling resistance" lessening.
But maybe I'm confusing the components in some way.
DoughlessThe chart shows resistance when the car is in motion and not still, is that right?
DoughlessSo which is it, does a heavier car create greater or less rolling resistance?
Doughless Overmod Doughless Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well...gravity pulling it the opposite direction, and by contrast, that heavier car would continue to roll farther down the slight grade? Both compared to a lighter car. Which falls faster, a pound of feathers or a pound of iron? Then, which falls faster, a pound of iron or ten pounds of iron? Hint: examine what cancels in the equation for gravitational acceleration... you don't 'compare it to a lighter car'. There's greater force to overcome bearing resistance with the heavier car, which I think is probably what you meant, but the speed doesn't vary just because of car mass/weight. So which is it, does a heavier car create greater or less rolling resistance?
Overmod Doughless Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well...gravity pulling it the opposite direction, and by contrast, that heavier car would continue to roll farther down the slight grade? Both compared to a lighter car. Which falls faster, a pound of feathers or a pound of iron? Then, which falls faster, a pound of iron or ten pounds of iron? Hint: examine what cancels in the equation for gravitational acceleration... you don't 'compare it to a lighter car'. There's greater force to overcome bearing resistance with the heavier car, which I think is probably what you meant, but the speed doesn't vary just because of car mass/weight.
Doughless Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well...gravity pulling it the opposite direction, and by contrast, that heavier car would continue to roll farther down the slight grade? Both compared to a lighter car.
Which falls faster, a pound of feathers or a pound of iron? Then, which falls faster, a pound of iron or ten pounds of iron?
Hint: examine what cancels in the equation for gravitational acceleration... you don't 'compare it to a lighter car'.
There's greater force to overcome bearing resistance with the heavier car, which I think is probably what you meant, but the speed doesn't vary just because of car mass/weight.
So which is it, does a heavier car create greater or less rolling resistance?
Less per pound, but still more total.
I could see that effect in my rolling tests years ago
Sheldon
DoughlessHmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well...gravity pulling it the opposite direction, and by contrast, that heavier car would continue to roll farther down the slight grade? Both compared to a lighter car.
gregc Doughless Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well the chart doesn't say there's less resistance! simply that there's less per ton. so 6 lb/ton empty vs 3 lb/ton loaded at 25 mph. a 20 ton empty would have 120 lb resistance and at 50T loaded, 150 lb. you might so the resistance is practically the same. now going up a 1% grade, that 20T empty has ~0.2T added resistance and the loaded 50T ~0.5T added resistance.
Doughless Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well
the chart doesn't say there's less resistance! simply that there's less per ton.
so 6 lb/ton empty vs 3 lb/ton loaded at 25 mph. a 20 ton empty would have 120 lb resistance and at 50T loaded, 150 lb.
you might so the resistance is practically the same.
now going up a 1% grade, that 20T empty has ~0.2T added resistance and the loaded 50T ~0.5T added resistance.
The chart shows resistance when the car is in motion and not still, is that right?
DoughlessHmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well
DoughlessAnd a heavier car would have more intertia needing to be broken, making it less free rolling, at least initially.
The point of higher inertia is that it reduces acceleration in 'recoil' when pushed, so couplers that need time to engage when pushed together will get it even if the car runs on jewel bearings with superfinished near-line-contact tread patches.
Hmmm, I'm no engineer, but wouldn't a heavier car that was rolling up a slight grade not roll so well...gravity pulling it the opposite direction, and by contrast, that heavier car would continue to roll farther down the slight grade? Both compared to a lighter car.
Not getting into physics math, but some portion of the roll is based upon the friction on the bearings and another based upon gravity pulling the mass towards the bottom of the grade.
And a heavier car would have more intertia needing to be broken, making it less free rolling, at least initially.
There isn't much concern about free rolling unless you want to max-out the pulling power of the loco. JMO.
gregc Lastspikemike Adding weight to a free rolling car won't change how far it rolls after being pushed by a locomotive during shunting. In fact, given that bearing and wheel friction is unlikely to be proportional to weight of the car Armstrong's charts on rolling resistance of prototype trains indicates that loaded cars have less resistance than empty cars. of course i don't know how well this scales
Lastspikemike Adding weight to a free rolling car won't change how far it rolls after being pushed by a locomotive during shunting. In fact, given that bearing and wheel friction is unlikely to be proportional to weight of the car
Armstrong's charts on rolling resistance of prototype trains indicates that loaded cars have less resistance than empty cars. of course i don't know how well this scales
It would be very difficult to scale this down to HO for a few reasons:
1. One would need to have the exact same wheel profile in HO to have the exact same relative size of contact area between wheel and rail. There are "prototypical" profile wheels in HO, however:
2. Our HO wheels are normally some kind of a nickel plated finish riding on nickel silver rails. Both have different friction factors from prototype steel rails and cast or machined steel wheelsets.
3. Volume and especially weights of model freight cars may not replicate the real weights either empty or loaded.
John
NHTX This discussion has become quite humourous at times. At one time the big quest was to get our anvils to move more effeiciently. The hobby press was awash with complaints about the rolling, or non rolling qualities of HO trucks. At the time, it was blunt ended axles turning in bored holes. Then, along came Central Valley brand trucks. They were sprung, with metal wheelsets and more attention paid to the bearings. They were Cadillacs of their day, but bricks compared to today's engineering plastic, needle point bearing gems. The complaints have done an about face. The trucks of today roll too much! Before we go back to the days of square wheels under bricks, a simple solution to frisky running gear would be wipers of varying material and tension, bearing on the inner axles of one or both trucks. I, for one, don't want to return to the days of sleds dripping 3-in-1 oil all over the place. I was taught that when spotting cars, once they were "on spot", before you pulled the pin, you made sure the hand brakes were set-tight. When you were picking up said cars, before releasing said handbrakes, you made sure you had made a good joint on the knuckles. Prevented lots of unnecessary excitement, cardio, and loud noises that way.
This discussion has become quite humourous at times. At one time the big quest was to get our anvils to move more effeiciently. The hobby press was awash with complaints about the rolling, or non rolling qualities of HO trucks. At the time, it was blunt ended axles turning in bored holes. Then, along came Central Valley brand trucks. They were sprung, with metal wheelsets and more attention paid to the bearings. They were Cadillacs of their day, but bricks compared to today's engineering plastic, needle point bearing gems. The complaints have done an about face. The trucks of today roll too much!
Before we go back to the days of square wheels under bricks, a simple solution to frisky running gear would be wipers of varying material and tension, bearing on the inner axles of one or both trucks. I, for one, don't want to return to the days of sleds dripping 3-in-1 oil all over the place.
I was taught that when spotting cars, once they were "on spot", before you pulled the pin, you made sure the hand brakes were set-tight. When you were picking up said cars, before releasing said handbrakes, you made sure you had made a good joint on the knuckles. Prevented lots of unnecessary excitement, cardio, and loud noises that way.
Interestingly enough, my metal on metal solution described above tends to not "roll away" easily but has very low friction once set in motion.
And I still have some Central Valley trucks.
This discussion has become quite humourous at times. At one time the big quest was to get our anvils to move more efficiently. The hobby press was awash with complaints about the rolling, or non rolling qualities of HO trucks. At the time, it was blunt ended axles turning in bored holes. Then, along came Central Valley brand trucks. They were sprung, with metal wheelsets and more attention paid to the bearings. They were Cadillacs of their day, but bricks compared to today's engineering plastic, needle point bearing gems. The complaints have done an about face. The trucks of today roll too much!
Chuck,
I don't have a bunch of numbers handy right now, but years ago I did a lot of testing and found that the following truck setup provided the most freerolling cars and best tracking.
Kadee self centering sprung (equalized) metal trucks.
Wheelsets replaced with Intermountain code 110 versions.
A drop of light oil in each journal box at assembly.
Cars weighted to NMRA RP or 10-15% less.
This combination inceased the pulling ablity of my locomotive fleet by 20-25% on average, and rolled free on .5% grades in most cases, performing better than ANY rigid plastic truck/wheelset combination I could find.
LastspikemikeAdding weight to a free rolling car won't change how far it rolls after being pushed by a locomotive during shunting. In fact, given that bearing and wheel friction is unlikely to be proportional to weight of the car
Armstrong's charts on rolling resistance of prototype trains indicates that loaded cars have less resistance
edit: resistance / ton
than empty cars. of course i don't know how well this scales