on another forum, someone asked what locos pull more than expected? what's expected?
i estimated that the pulling power of a loco is 20-25% of its weight and that the effect of gravity going up a 1% grade is approx that percentage of a car's weigh -- the grade requires 0.04 oz to pull a 6" car weighing 4 oz.
so 50 4oz cars adds 2 oz of resistance to be pulled up 1% grade which is 20% of a 10 oz loco and the # of cars the OP on the other forum said his loco could pull
i've gone thru my trucks, measured the grade they roll freely on and after tuning the worst truck would roll freely on a 2% grade. some rolled uphill :). But Armstrong's chart indicates the full cars roll more freely than empty cars and I would expect better performance with a weight car body.
is 1% of the weight an accurate estimate of the resistance of model cars on level ground?
greg - Philadelphia & Reading / Reading
I have always had small layouts in HO scale, longest trains are 12 cars, no grades anywhere, dead flat.
.
I expect all locomotives to pull a 12 car train, and so far, all have been able to do it.
A double headed pair of powered Stewart F3s can simply walk away with a 12 car train with ease. I am satisfied.
I think each person's expectations will be different.
-Kevin
Living the dream.
Not familar with all the math & physics involved..but I do know that most, if not all, of my HO Athearn & Atlas 6 axle locomotives will easily pull up to 30 free rolling , truck tuned, properly weighted cars by themselves on level grade. Meaning most single loco trains are about 18-24+ ft long depending on car type...auto racks, 50' box etc
These are straight out of box locos with no modifications or added weight
dbducklocomotives will easily pull up to 30 free rolling
loco weight?
Hello All,
Then there is this thread...
Prototyical horsepower versus actual pulling power of modlels
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
Here is some info to start with, I will post some more in a bit:
(this information provided by another modeler known to some as "Hunt")
Sheldon
James Wright the youtube guy measures loco pull with probably a micromark scale that looks like that. A "spring scale" could do the same.
The question was the "expected pull" That would depend on the loco weight, the quality of the motor, the number of driven wheels. Weight and wheels are obvious, though some locos have traction tires, so that implies they need extra friction. Motor quality must be determined empirically.
Henry
COB Potomac & Northern
Shenandoah Valley
gregc they vary but most between 15-18 ounces dbduck locomotives will easily pull up to 30 free rolling loco weight?
they vary but most between 15-18 ounces
dbduck locomotives will easily pull up to 30 free rolling
I have read that the maximum pulling ability of most locomotives, model or full-size, is equal to about 25% of their weight, and some modified Athearn U-Boats verified that figure, almost exactly, in tests done at a nearby model railroad club.
Each of the three locos tested weighed 33oz., and each tested at a drawbar pull of 8.3oz., plus-or-minus a bit.
I don't have much level track or straight track on the lower part of my layout, but I did do tests with most of my locomotives on the two most severe grades (2.8%). One is fairly short, about 15' with two 34" radius curves in opposite directions.This helped me to determine (very roughly, as I would consider the rolling qualities of my freight cars to be rather disparate) "tonnage ratings" for most locos.I did test the U-Boats on that short grade, and was disappointed to see that one unit could not pull a 44 car hopper train completely up the grade, slipping its wheels about 6' from the crest of the grade. Much of the trailing train was still on straight and level track.
I backed the train down the hill, and added another unit to the one used in the first run. The two units easily took the train up the hill, with no wheelslip whatsoever. I would have liked to have added more cars, but I had no more hoppers, and no "coal" to add to them either. I use Black Beauty blasting medium for Anthracite coal, so the trailing train's weight was 22lbs.
When I backdated my layout, those diesels, along with most of my other ones, were sold.I did another test with four remotored Athearn switchers (the SW7s, originally sold as SW1500s), and they were able to pull a train of 71 cars, with various rolling qualities, up the 2.8% grade to the second level (or at that time, where the second level was to be built).I repeated that test several times, with the locos in various places within the train, and substituting modified Athearn Mikados and/or Bachmann Consolidations for some or all of the diesels. Every combination was able to reach the top of the grade, but there was nowhere to go beyond that.
I did learn that two of those switchers or two of the Bachmann and Athearn steamers (and various duos of each) can handle 12 loaded hoppers and a caboose up both of the 2.8% grades. The upper grade is about 45' long, and features two horseshoe-type curves in opposite directions, plus several other curves just before the top of the grade. Weight of the trailing train in this instance is only 100oz.Using two such steamers on such a short train is not likely all that realistic, but I have an unmodelled coal-fired power plant on the upper level, and that coal traffic is part of the operations. I could, I suppose, use unmodelled coal in the hoppers, too, but I like the idea of the challenge.Most regular freights will be between 12 and 20 cars long, adjusted somewhat if there are too many heavy cars - I have a lot of gondolas with "live" loads, and many of them are in excess of 10oz.
This "doodlebug", with only the front truck powered, can easily handle 19 cars on level, albeit mostly curved, track...
In normal service, a coach or two and maybe a freight car should look believeable, though.
I don't know if this old video will still work. This is DC operation, and while the video, if it works, has sound, it's that of electrically-powered models, along with some wheelslip and other noise.
I checked the video in "Preview" and it works for me. If you click on the link, please let me know it it works. If it doesn't, I'll remove it, as I don't wish to waste anybody's time.
Wayne
Most modelers own way more locomotives than they need for the number of cars they have. So you can always throw another engine on a train.
Disclaimer: This post may contain humor, sarcasm, and/or flatulence.
Michael Mornard
Bringing the North Woods to South Dakota!
All HO model locomotives that I have ever seen have enough motor power to spin the wheels. In that case, maximum pulling power is given by the coefficient of friction for metal on metal. Which is something in the order of 0.20 to 0.25. So the maximun pulling power of a locomotive, be it full size or a model, will be 0.20 to 0.25 times the locomotive's weight.
To increase pulling power, you need to add all the weight that you can cram into the locomotive. Or you can increase the coefficient of friction with rubber traction tires or Bullfrog Snot. Coefficient of friction for rubber on metal is 0.75 to 0.80. Or you can do both, add weight and use traction tires.
David Starr www.newsnorthwoods.blogspot.com
many have confirmed the pulling power of a loco is 20-30% its weight
gregcworst truck would roll freely on a 2% grade. some rolled uphill :). is 1% of the weight an accurate estimate of the resistance of model cars on level ground?
has anyone done a pull test on a long string of cars?
At the Bucyrus HO club the front layout had ridiculous steep grades yet four Athearn BB GP38-2s pulled a 36 car train around that layout which means while half the train was on the downside of the grade the other half was still on the upgrade side..
My cars weighed 3 oz and uses IM wheelsets. I usually ran 18 car trains with three Athearn BB GP38-2s simpily because the train look better on those ridiculious grades.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
The only test I have ever done for pulling was on a mock-up of the 5% grade with a 22"R curve at the top as proposed for my next layout to get the "local turn" into staging.
A Walthers Proto FM Switcher will pull four cars and a caboose up that grade and around the curve with no problem.
Good enough for me.
I have a small layout, the main line, about a 50' run at most, with a 1 1/2" grade, my longest trains are 20 cars.
It's an "L"shaped dog bone, with a 24"r. loop on each end.
Any of the 6 axles of have, Kato, and Genesis, all handle it well. Most start to creep at speed step 1. Spectrums, not quite.
4 axles, not quite, more like 12 or 15 cars.
I have plenty of power I can add on, if needed.
It is kinda fun to see how much a loco can pull, considering the curves I have on the layout, with the L shape.
Mike.
My You Tube
gregc many have confirmed the pulling power of a loco is 20-30% its weight gregc worst truck would roll freely on a 2% grade. some rolled uphill :). is 1% of the weight an accurate estimate of the resistance of model cars on level ground? has anyone done a pull test on a long string of cars?
gregc worst truck would roll freely on a 2% grade. some rolled uphill :). is 1% of the weight an accurate estimate of the resistance of model cars on level ground?
Long trains are a primary interest for me.
In the data I posted above:
Broadway N&W 2-6-6-4, 75 cars up 1.8% grades
And lots of other 30 plus car examples, many with my uniform set of piggyback cars.
Most of of my testing is with steam, since diesels all pull much better. All my four unit diesel lashup (typically F units or GP units) easily pull 100 cars up 2% grades.
Point of both my long posts? There is much more to this than engine weight or a single value for rolling resistance.
As an operator of long trains, typically 35 cars and longer, with many being 50 cars or more, knowing what it will take in motive power is important.
ATLANTIC CENTRALThere is much more to this than engine weight or a single value for rolling resistance.
just interested in a reasonable measurement of train (>30) resistance on level straight track, an average.
i understand that curves and grades add to this.
gregc ATLANTIC CENTRAL There is much more to this than engine weight or a single value for rolling resistance. just interested in a reasonable measurement of train (>30) resistance on level straight track, an average. i understand that curves and grades add to this.
ATLANTIC CENTRAL There is much more to this than engine weight or a single value for rolling resistance.
I understand. My work with free rolling trucks has shown me that rolling resistance can very greatly, and is not automatically linear in relation to car weight.
I prefer sprung metal trucks, I use mostly Kadee trucks refitted with Intemountain code .110 wheels.
This combination rolls as freely or more freely than any rigid plastic truck/wheel combo I have tested. But it works better on heavier cars. Meaning that as the cars get heavier, the rolling resistance does not increase in proportion to the weight.
But pulling long trains, I find the lower center of gravity with metal trucks, and the equalizing, to provide much better tracking.
What about gear ratio? Does that effect pulling power of a diesel?
There were "Super Gearing" kits available for Athearn Diesels that made the run very slow and was supposed to make them better pullers.
How does this factor in?
ATLANTIC CENTRALrolling resistance can very greatly
i agree
ATLANTIC CENTRALThis combination rolls as freely or more freely than any rigid plastic truck/wheel combo I have tested. But it works better on heavier cars. Meaning that as the cars get heavier, the rolling resistance does not increase in proportion to the weight.
in the link from above
SeeYou190What about gear ratio? Does that effect pulling power of a diesel?
i'm guessing the gearing may increase TE, but weight limits max TE
Prototype railroads did lots of testing and calculations, but at the end of the day, they just needed to know how much tonnage a given loco could move (and stop/hold still) over the ruling grades of a given section of the line.
That is my goal. Once the new layout is operating I will do tests with the piggyback cars, which are for the most part my heaviest rolling stock, and set tonnage ratings for selecting motive power for trains.
The layout plan stores about 30 trains in staging, most being able to be 35 to 50 cars long.
Most will require two steam locos or three to four diesels.
Sheldon.
ATLANTIC CENTRAL wrote the following post 2 hours ago:
"Prototype railroads did lots of testing and calculations, but at the end of the day, they just needed to know how much tonnage a given loco could move (and stop/hold still) over the ruling grades of a given section of the line."
Almost all of the "holding still" is done by the air brakes on prototype cars. I did hear of a modeler who ran long trains of cars loaded with real iron ore up steep grades using rear end helper locomotives. After the helpers were cut off if the train went down grade too fast it could not be stopped. Even with the power shut of the weight of the train would slide the locomotives down the grade.
Mark Vinski
RR_Mel My degree is a EE so I have no idea if the way I measure the drawbar on my locomotives is accurate. I bought a digital hanging scale that measures from 0 to 5 pounds in tenths of an ounce. I bought a calibrated weight set to make sure the meter is accurate and it is. I replaced the hook to connect better to my trains from .032” Phosphor Bronze wire. This is the way I connect the meter to a locomotive with Kadee couplers. The track is a 18” piece of Atlas code 83 track with wires soldered to the rails that plug into my bench power supply. I crank up the voltage until wheel slip then use that reading on the digital meter for drawbar and the voltage and current on the power supply for wheel the wheel slip measurements. I’m open for suggestions if the above isn’t correct. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
gregc has anyone done a pull test on a long string of cars?
I don't know if it would be considered a long string or not, but I did a pull test on a Bachmann 0-6-0-T Porter side-tank engine not that long ago after reading a review of that model. The locomotive weighs 4.7 oz., and was able to pull 7 40' quadhoppers weighing 2.5 oz. apiece on fairly level track at about 30 scale mph without any wheel-slip. At 8 cars, it started to slip. I should also add that the quadhoppers still have stock plastic trucks and wheels. For such a small engine, I'd say it has pretty good pulling power.
thanks for the data
20% of 4.7 oz loco wt is a Tractive effort of 0.94 oz
8 2.5 oz cars is 20 oz.
that the equivalent of a 4.7% grade (0.94/20).
I was expecting < 2%
rather hastely measured a pull of 2.4 oz for 30 cars ~4 oz each, total 120 oz. comparable to going up a 2% grade. still expected it to be a bit less.
if max TE is ~20% of weight, a 12oz loco should be able to pull this train.
I have a terribly hard time believing any mathmatical formula that ends with basically a 12 ounce locomotive should pull X many cars.
There are too many other variables.
Quality of the gear train, center or gravity, are the trucks sprung and equalized, are the trucks balanced, what material are the wheels made of, gear ratio, bearing slop, worm end-play, and so on, and so on, and so on.
I guess that is why Model Railroader actually measures the pull of every locomotve they review, rather than just weigh it.
I'll bet that if I take two locomotives that are mathmatically indentical, load them up with cars, and send them up a 3% S-curved grade made with Kato Unitrack 28" radius sections that they WILL NOT both max out at the same number of 4 ounce cars all with indentical Kadee trucks.