Tony Koester suggested making sure the engines you plan to use on your layout can climb the grades you plan to have with the number of cars in the trains you plan to have. While this is good advice for planning a layout, it suggests that not all engines are alike.
I assume the small electric motors provide more than enough power for our models and can easily make the wheels spin on our models.
so should any 8 driven wheel locomotive (e.g. 0-8-0, 2-8-0, 4-8-4) having the same weight on all eight wheels have the same pulling power (force)?
but as Tony seems to imply, are all models comparable; do similar wheel arrangements have the same pulling power? does it matter to you?
greg - Philadelphia & Reading / Reading
LION builded layout with steep grades, locos and consists bulled their loads just fine.
LION switched to LifeLike Proto 1000 subway cars and could not pull the grade. LION pulled out the grade and installed helixes.
LION bought some Walthers/LifeLike Proto 1000 subway cars, and the motor could not even pull itself around the road.
LION installed NWSL motors, zoom and pull... Now must install new motors on all train sets.
Motors make the train go round.
Maybe we should call motors "the prime mover", traction refers to trolley cars.
ROAR
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As Lion relates not all motors are equal. In addition to weight some locomotives use rubber tires (or the equivalent liquid product) for more traction. Also the cars you are using, their weight and free rolling characteristics make a difference. How much weight (if any) is riding on the leading/trailing trucks makes a difference. Even the gears can make a difference.
Your locomotives and cars may be very different from one manufacturer to another (or even one production run to another) for the "same" 2-8-0.
Good luck
Paul
Pulling power on locomotives, all scales, including full scale, is the product of weight on drivers and the coefficient of friction between wheel and rail. For models, the weight on drivers is the full locomotive weight for all practical purposes. Let's ignore trainset diesels with only one powered truck, and ignore the trivial amount of weight on steamer pilot and trailing wheels. Coefficient of friction for nickel silver wheels on nickel silver rail is about 0.2. This means the wheels will slip when they push on the rails with a force greater than 0.2 times the locomotive weight. If the locomotive weights one pound, its pulling force will be 0.2 pounds.
Other metals, brass, steel, aluminum have about the same coefficient as nickel silver. Only rubber, as in traction tires or Bullfrog Snot, has a significantly better coeffient of friction, about 0.7.
So, first lesson, put as much weight in a model locomotive as you can. Second, assuming metal wheels, pulling power will be 0.2 times the locomotive weight.
In the matter of picking locomotives that can handle your grades and curves, get the heavyist locomotives you can find. If you have 18 inch curves, beware of six axle diesels and big steam. If you buy such, make sure the store will allow you to return it should it fail to stay on your track. Six coupled steamers work on 18 inch radius, no sweat. Most 8 coupled steamers will also make it. Ten coupled and up, probably not.
David Starr www.newsnorthwoods.blogspot.com
so it seems that weight of a loco is a significant factor in it's "pulling power" (force). Locos of equal weight should have roughly equal pulling power.
do you think it would be helpful for manufactures to list the weight of their locos or that a review list the weight of a loco?
do you think the NMRA could provide a table listing the approximate number of cars a loco can pull up a 1% grade based on the weight of the loco?
Model engines with the same weight, wheel arrangement, gearing, and motor may pull about the same (assuming both engines have been broken in about the same length of time). Or they may not. An old 1990's Bachmann N&W "J" 4-8-4 with a 'pancake' motor isn't going to run as well or pull as much as a new BLI "J", no matter how much weight you add.
You can add the weight you want to your Yugo, but it's not going to make it a Cadillac.
wjstixAn old 1990's Bachmann N&W "J" 4-8-4 with a 'pancake' motor isn't going to run as well or pull as much as a new BLI "J", no matter how much weight you add.
why won't it pull as much? Are the physics different for BLI locos?
i don't believe gearing is going to cause the wheels to slip with a greater or lesser load, it depends on the torque at the wheels, the weight on the wheels and the coefficient of friction, as Dave mentioned.
I wouldn't expect to add weight to a Yugo and expect it to have the performance of a Cadillac. But they add wings to F1 cars to increase the downforce (3.5g) on the wheels to increase the friction at the wheels so that they can take the turns at much higher speeds without sliding.
are there any examples of full size locos that weight about the same but have significantly different tractive force.
Adding weight works most of the time (I put a piece of carbide on to of my Trackmobile and I can pull twice as many cars...and the added weight increases electrical pickup too), but smooth trackwork is essential too.
Our models have (mostly) rigid suspension and if the track is even slightly lumpy, it can cause one or more wheels to lift off the rails (sometimes imperceptibly) and cause wheelslip. Once wheels start slipping, you have to slow the motor down until they stop slipping and then reapply power. It's kind of like drag racers taking off from the line or stepping on the gas too hard when snow is on the ground. I read an article years ago about improving suspension on brass steam engines (it might have been one of Tony's articles)...I didn't even know they had sprung suspensions, apparently some, but not necessarily all, do.
Make sure wires or details don't interfere with the movement of the trucks on diesels...I found a switcher I have had stiff wires that kept the trucks from moving freely. I replaced the wires with smaller, more flexible wire, and now it runs much better.
To make rolling stock roll more freely, (and I'm sure everyone has their own specific results) I find metal axles in plastic side frames roll pretty freely; I do have some plastic axles in plastic side frames that roll equally as well, so it all depends. Axle length and the smoothness of the bearing surface are important too, get a Truck Tuning tool...I have one but it doesn't work very well (for me) so I rarely use it.
Always trying something new, I recently started using lock lube to lubricate the axle points. Lock lube is a very thin viscosity graphite lube, once the solvent evaporates, a thin coating of graphite is left...it beats my old way of using shaved pencil graphite in the sideframes. I apply the lube by removing the wheelset and using a small paintbrush to coat the inside of the sideframe with a little lube. Let the carrier evaporate a little (don't use too much) and reinstall the wheelset and roll it around a little (don't expect a huge improvement, but it adds up).
How much a loco weighs is only part of the equation. Put some weight on top of your loco and see if that helps, if not, check your trackwork, then try to modify the cars that you need to pull (maybe you only pull long coal drags? Only modify the hoppers at first, to see if that helps)...if all else fails, cut in a helper or pusher to get that train over the hill (both passenger and freight trains get helpers depending on where they run...even today).
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SEMI Free-Mo@groups.io
I posed a similar question to the forums...
http://cs.trains.com/mrr/f/13/t/243497.aspx
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"