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?
ChuckAllen, TX
I remember it as being 2%. These days a "free rolling" car will do a lot better than that.
Hello All,
cefinkjrI would think it's somewhere in the neighborhood of 1 or 2 percent. Does anyone have a better number?
I run cuts of upgraded Tyco 34-foot operating hoppers from the 1970s.
The upgrades are:
I use a Micro-Mark HO Truck Tuner to ensure the bearing surfaces are burr-free and at the NMRA RP of 60º.
These cars are underweight at 3 oz each when empty (NMRA RP weight is 3.34 oz or 95 g).
My 4'x8' pike has a less than 1% grade (0.96%) along the 8-foot side because it sits on the bed in the computer/train/spare bedroom.
This is measured with a Micro-Mark digital level.
If I let a cut of eight (8) cars go at the top of the "grade" they will free-roll and settle in the middle of the curve at the bottom of the grade.
This is on a straight section of track 50-inches long to the asymmetrical curve of 18- and 15-inch sectional track.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
I also run those old Tyco cars. Mine are from the early 1960s, certainly pre-65 when I graduated from high school. I have also replaced first the Talgo couplers with body-mounted Kadees, and then the trucks and wheelsets with Tichy trucks and Intermountain wheelsets.
The string of cars used to take a pair of engines to pull around, but it's down to one engine after the wheelset upgrade.
I try to maintain a zero grade on my layout, but since I went to all-metal wheels I've found a few sidings where I was careless and had to add some tall grass between the ties to keep cars from rolling downhill.
It takes an iron man to play with a toy iron horse.
Mr Beasley
Thanks for the tip about adding tall grass between the ties. That sounds like a very clever and not obvious way to deal with a siding that is a bit off level. I have this problem and love this solution. Thanks.
wdcrvr
"One difference between pessimists and optimists is that while pessimists are more often right, optimists have far more fun."
The better cars today (NOT "upgraded" Tyco) will start rolling for me on my 0.4% grade. I'll call that free-rolling.
Also, some manufacturers (including but not limited to Exactrail) advertise cars as being free rolling when in fact they are anything but. So I take that term with a grain of salt.
John
Wouldn't "free-rolling" be defined as the gradient on which the piece of equipment in question begins to roll, without motive power? As stated, depending on many factors, the same pieces of rolling stock, from the same manufacturer will require different percentages of gradient to begin independent movement.
The term "free rolling" appeared frequently in advertisements and reviews, without any specific percentage of gradient ever being mentioned. It could be 0.4% as mentioned for some of the upgraded Tyco hoppers, or 14% for a straight-out-of-the-box example of the same car. A lot of modelers found out their layouts were not as flat as they thought, when they began using Lindbergh trucks, way back when.
i believe "grade", not gradient is the appropriate term
after noticing that some cars seemed to roll up hill, i checked each of my car's trucks on an adjustable grade, "tuning" those that required more than a 2% grade to roll on there own.
some trucks easily rolled on far less than 2%. others required work to roll at 2%
we measured the pulling force of a loco with a string so cars on level track but thru some turnouts. there were ~30 cars we estimated at weighing ~4 oz/car. we measured ~2.4 oz of force which works out to be roughly 2%.
greg - Philadelphia & Reading / Reading
My latest "free rolling" cars will move if you simply breathe in their vicinity, and rapidly run away if you give them a funny look....
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.
ricktrains4824 My latest "free rolling" cars will move if you simply breathe in their vicinity, and rapidly run away if you give them a funny look....
Mine too. Terrible for switching. It tends to just bump the car down the spur. I need to replace free rolling trucks with old Tycos or something.....
- Douglas
I do recall a siding on our railroad that required quite a bit of work before cars stopped rolling out toward the mainlne switch.
The bump and run syndrome disappears if you are switching cuts of cars, rather than an individual car. It may also be a signal that you need to free up some couplers to guarantee the knuckles open and they center correctly.
It also depends upon how fast, or not, the cars are banged.
I've taken to over-weighting the cars in my roster that I can, and all of my Accurail kit builts are true "heavy weights" with added weights inside them.
When I delivered auto parts, my boss and coworkers thought I was nuts that I asked to purchase a box of wheel weights, as I do not have a tire mounting/balancing machine. But the cost was way less than the cost of similar weights available from the model companies.
While they still roll very smoothly with the added Intermountain wheelsets, they tend to not "take off" when slowly switching industries. (So long as I don't bump hard...)
Doughless ricktrains4824 My latest "free rolling" cars will move if you simply breathe in their vicinity, and rapidly run away if you give them a funny look.... Mine too. Terrible for switching. It tends to just bump the car down the spur. I need to replace free rolling trucks with old Tycos or something.....
This drives me absolutely nuts. The cars jump because they have so little resistance. I have almost replaced the wheelsets with something with more resistance because of it. The cars follow the gradient more readily than my switchers force. That my freinds is free rolling!
JJF
Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing.
Yesterday is History.
Tomorrow is a Mystery.
But today is a Gift, that is why it is called the Present.
LastspikemikeTechnically grade is horizontal whereas gradient is the slope from one grade to another.
Of course when the civil part of the roadbed has no gradient we just call it 'level grade' just as the 'grader' left it...
Maybe there are parts of Canada where they sing 'She was going down gradient makin' 145 kilometers an hour when they heard that whistle scream...'
LastspikemikeAdding weight to a .....yada, yada...hollow iron sphere of the same volume from the tower of Pisa....
There seem to be several who have more time to discuss the semantics of the responses rather than addressing the point of the question.
The way we defined "free rolling" 40 years ago when the club was testing cars to make sure they met the club's standard was to place it on a tilted board that sloped up 2 inches in every 100. And that 2% was what I think was thrown around in the press. I know we didn't create that value. There was not ever any discussion as to whether this was grade, slope, gradient or any of the other felgercarbis that some want to throw around.
And there was not any "pushing" involved, either by 0-5-0 or powered engine. The car was simply placed at the top of the hill and the 0-5-0 released. The car either rolled (passed) or didn't (failed).
I know from experience that it is easier to couple to a heavy free rolling car than a light one. This is because the lighter car will want to run away from the coupler before the mechanical forces causing the coupler to remain closed can be overcome. I think this is called "inertia".
I also believe that a heavy free rolling car will roll further than a light one. When we balanced turbine rotors the heavy rotors always took longer to coast down from full speed than the light ones. Again, I think this was inertia.
So far as Galileo goes, I don't know what he dropped on his Pizza, but I do know that he didn't get it from Papa Johns.
I can't remember a standard different from 2% in any discussion by 'serious model railroaders'
My definition of free-rolling would involve much less 'gradient', but that's immaterial to the actual question that was asked... and it would, in fact, involve testing the car on an incline rather than measure its impact behavior.
At the risk of opening more cans of besserwisser worms, perhaps there should be several measures of "free rolling", including sensitivity to sustained 'rolling away' and enough inertia to facilitate 'making the joint' with Kadees even if the car would have run or recoiled away if the knuckles didn't engage. There should be different and descriptive names for any such 'metric' to distinguish it from rolling resistance or drag.
Lastspikemike We use grade to mean gradient. Technically grade is horizontal whereas gradient is the slope from one grade to another. A 2% grade is a 2% gradient but we modellers only mesh change of grade anyway. Highway signs use grade in the same inaccurate manner andcwe all understand the warning means gradient or rate of grade change.
We use grade to mean gradient. Technically grade is horizontal whereas gradient is the slope from one grade to another. A 2% grade is a 2% gradient but we modellers only mesh change of grade anyway.
Highway signs use grade in the same inaccurate manner andcwe all understand the warning means gradient or rate of grade change.
What are you talking about??????
I'm a licensed professional civil engineer. That means I sign and seal, and am responsible for, the plans for major projects completed under my supervision--and specifically that I can be sued for any mistakes because my job affects public safety.
Grade is NOT horizontal, but is defined as rise (or fall) divided by run. The only time grade is ever horizontal is when it is 0.00%. Gradient or gradiant in actual engineering practice is generally considered to be the EXACT SAME TERM as grade.
And NO those highway signs that warn you of a downhill grade are NOT talking about "rate of change of grade", but literally that the downhill grade IS that average number expressed in percent and stated with or below the warning sign. The motorist doesn't CARE if the grade is changing, they CARE how steep it is relative to braking capability of their vehicle (which is based upon conservative experimentally determined values for wet pavement that we use for real world design). Building a new Interstate freeway in rolling terrain? Your mainline grade cannot exceed 5% per federal standards (since they pay 80% of the cost).
Ruling Grade is defined as the grade over a division of a railroad (or highway) that represents the limiting design factor or tonnage restriction over that division. Ruling Grade is the grade upon which motive power tonnage tables (in both steam and diesel eras) are determined. How many and what types of engines per how many tons of calculated train weight?
Ruling Grade is affected by horizontal and vertical curvature as well. There are old mathematical forumlae dating back more than a century now that can be used to calculate friction losses due to curvature. All of this would get factored into determining the "compensated" grade, which will then affect which grade over a division might be the ruling grade.
I read recently in Railfan that one M-636 on WNY&P was required for each eight loaded covered hoppers over Keating Summit. That was an example of practical application of ruling grade to tonnage.
John Mock
Overmod I can't remember a standard different from 2% in any discussion by 'serious model railroaders' My definition of free-rolling would involve much less 'gradient', but that's immaterial to the actual question that was asked... and it would, in fact, involve testing the car on an incline rather than measure its impact behavior. At the risk of opening more cans of besserwisser worms, perhaps there should be several measures of "free rolling", including sensitivity to sustained 'rolling away' and enough inertia to facilitate 'making the joint' with Kadees even if the car would have run or recoiled away if the knuckles didn't engage. There should be different and descriptive names for any such 'metric' to distinguish it from rolling resistance or drag.
I completely agree. I have pushed kadee equipped cars down a siding with just the couplers touching. Yet they won't couple. I love free rolling cars but there is or should be a limit to how free rolling a car can be. If I can push the car but not couple that is a problem.
PRR8259 Lastspikemike We use grade to mean gradient. Technically grade is horizontal whereas gradient is the slope from one grade to another. A 2% grade is a 2% gradient but we modellers only mesh change of grade anyway. Highway signs use grade in the same inaccurate manner andcwe all understand the warning means gradient or rate of grade change. What are you talking about?????? I'm a licensed professional civil engineer. That means I sign and seal, and am responsible for, the plans for major projects completed under my supervision--and specifically that I can be sued for any mistakes because my job affects public safety. Grade is NOT horizontal, but is defined as rise (or fall) divided by run. The only time grade is ever horizontal is when it is 0.00%. Gradient or gradiant in actual engineering practice is generally considered to be the EXACT SAME TERM as grade. And NO those highway signs that warn you of a downhill grade are NOT talking about "rate of change of grade", but literally that the downhill grade IS that average number expressed in percent and stated with or below the warning sign. The motorist doesn't CARE if the grade is changing, they CARE how steep it is relative to braking capability of their vehicle (which is based upon conservative experimentally determined values for wet pavement that we use for real world design). John Mock
And NO those highway signs that warn you of a downhill grade are NOT talking about "rate of change of grade", but literally that the downhill grade IS that average number expressed in percent and stated with or below the warning sign. The motorist doesn't CARE if the grade is changing, they CARE how steep it is relative to braking capability of their vehicle (which is based upon conservative experimentally determined values for wet pavement that we use for real world design).
I'm not a civil engineer but I was thinking the same thing John.
JDawg PRR8259 Lastspikemike We use grade to mean gradient. Technically grade is horizontal whereas gradient is the slope from one grade to another. A 2% grade is a 2% gradient but we modellers only mesh change of grade anyway. Highway signs use grade in the same inaccurate manner andcwe all understand the warning means gradient or rate of grade change. What are you talking about?????? I'm a licensed professional civil engineer. That means I sign and seal, and am responsible for, the plans for major projects completed under my supervision--and specifically that I can be sued for any mistakes because my job affects public safety. Grade is NOT horizontal, but is defined as rise (or fall) divided by run. The only time grade is ever horizontal is when it is 0.00%. Gradient or gradiant in actual engineering practice is generally considered to be the EXACT SAME TERM as grade. And NO those highway signs that warn you of a downhill grade are NOT talking about "rate of change of grade", but literally that the downhill grade IS that average number expressed in percent and stated with or below the warning sign. The motorist doesn't CARE if the grade is changing, they CARE how steep it is relative to braking capability of their vehicle (which is based upon conservative experimentally determined values for wet pavement that we use for real world design). John Mock I'm not a civil engineer but I was thinking the same thing John.
Pretty much this.
Rio Grande. The Action Road - Focus 1977-1983
There is a "maximum relative gradient" term which only a highway engineer would ever use, and it is expressed with the Greek letter delta. It is a unitless number because it represents the rate of change of one pavement edge line relative to another. It is a ratio and is used to calculate the required minimum length of superelevation transition between any two cross sections, or more typically between normal -2% cross slope and whatever the superelevation maximum rate is.
However, practically speaking most people mean grade whenever they say gradient. When doing superelevation calculations most civil designers will just refer to the required delta value rather than the full name given above.
Since we are mainly talking about trains, for railroad design purposes, they express superelevation in inches of elevation of the higher rail relative to the lower rail at a given point. Trackside observers will sometimes see the chalkmarks on the sides of the rails of recently laid track denoting the difference in inches.
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, heavier cars will roll further if hit at the same speed by the locomotive.
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, heavier cars will roll further if hit at the same speed by the locomotive.
I don't quite understand this line of reasoning. First you state that weight does not matter, then you claim that heavier cars will roll farther. This latter claim is based on what? Did you do test runs, or is this just your expectation?
Thanks
JW
Lastspikemike That's one reason we know Galileo didn't actually drop an iron cannonball and a hollow iron sphere of the same volume from the tower of Pisa....
That's one reason we know Galileo didn't actually drop an iron cannonball and a hollow iron sphere of the same volume from the tower of Pisa....
Speaking of Galileo, I recall a hearing that they were going to install a large clock at the top of the Leaning Tower of Pisa...
After all, what's the point of having the inclination, if you don't have the time?
Jim
hardcoalcase Lastspikemike That's one reason we know Galileo didn't actually drop an iron cannonball and a hollow iron sphere of the same volume from the tower of Pisa.... Speaking of Galileo, I recall a hearing that they were going to install a large clock at the top of the Leaning Tower of Pisa... After all, what's the point of having the inclination, if you don't have the time? Jim
Oh, that's bad, really really bad.
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
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?
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.
Sheldon
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!
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.
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!
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.