Locomotive Discussion - physical power/traction on the layout? Diesel/Electric mainly


F

FlyFishn

Member
Hi All. First post here. I am trying to get a better feel for the different manufacturers of locomotives etc and a question I have had is how all the locomotives are rated, if there is such a thing, to power/traction. Are there different motors that are known to be more powerful than others? Any drive axle configurations? For example I would assume 6 wheel trucks would be bigger pullers than a set of 4 wheel trucks? Or does that still come back to the manufacturer and what kind of "guts" it has (motor, electronics, etc)?

For a frame of reference lets leave the layout out of the equation so we're comparing apples to apples strictly speaking of the locomotives and not layout considerations (power through the rails as opposed to leading off to a power buss, poor quality contacts, poor connections through track joiners, etc, etc).

Are there any "rules of thumb" for car count for certain makes/models of locomotives?

I am getting back in to model trains here from 15-20 years off. I have a 3x4ft oval layout for N. However, the locomotives and rolling stock are still MIA. They will turn up somewhere I'm sure, its just a matter of looking in the right place. A friend of mine took me to a club a few weeks ago and what really intrigued me was the DCC set up and wireless cab controls. Things are a world different than what I remember.

My goal is to experiment with wireless DCC. I figure I can start with the 3x4ft layout and expand on it with a yard. Then maybe keep it as a programming track. At some point I want to look in to a dual main line set up of some kind - perhaps a mountain scene. I am not sure what kind of space I will be able to work with yet.

On a side note, I have been intrigued with the SD70 model locomotives - specifically the Canadian National railroad with the black and red paint scheme. Does anyone know who makes locomotives in N scale for this model locomotive and rail road? Atlas does not, I got an email back from them - no SD70's in N period from them. I am trying to get a better mind's eye of what capabilities the locomotives have. I want to do a long freight train and maybe run dual locomotives at some point but I guess I don't have a good frame of reference to start with yet.
 
First of all, welcome to the forum. Lots of questions here, I will answer some of them. Disclaimer: I model in HO scale but there are many things that are common to both scales.
When Model Railroader reviews locomotives, they do "tractive" tests which give an approximation of power/pulling effort. It is different from manufacturer to manufacturer, and model to model. There are no real generalizations. They may have a list but I am not aware of one. One would have to look up the particular model in question and hope that they might have reviewed it.
Car count. An old rule of thumb was 2 freight cars per powered engine axle. Thus a pair of six-axle diesels could pull 24 cars. In reality I can pull more, again I am in HO scale but I would think that this generally applies across the lines. I generally don't pull more because of the length of my passing sidings, in HO mine are about 16' or so. N scale offers more possibilities for longer sidings.
I cannot assist on the SD70. Look at some model railroad retailers on-line for more info.

Willie
 
Welcome to the forum. Welcome.gif You asked a few very good questions. I, like Willie am in HO scale, but it is hard to gauge how much a locomotive can pull. If you are interested in DCC, the locomotives will probably pull a bit less as some of the weight inside the locomotive will have to be made smaller to allow for the decoder and possibly the speaker. Generally speaking, the more a locomotive weighs, the more it should be able to pull. I am a DC operator as I am a lone operator and my layout was build mainly for switching, but I also build some grades into the layout to limit the size of trains that can be handled by a single locomotive.

I do have a couple of DCC locomotives, on is operating in the video below, Switching in Churchill. This is a Bachmann locomotive. Excellent running locomotive. I have a very similar locomotive that is a DC only locomotive, which has quite a bit more weight in it as there is no need for decoders. It can easily out pull the DCC locomotive, by almost double. Od course, using DCC, you can easily add more locomotives, matching speeds and running multiple units.

I don't think there is any carved in a rock formula for how many cars a certain locomotive can pull.
 
Thanks for the info tootnkumin. They don't have any Canadian Nationals though. I sent them a message to see what the scoop is. It doesn't look like Kato may be easy to get in touch with directly.

OK on the pulling abilities. I can understand the size difference - if DCC is really that much "smaller" and/or "lighter" under the hood. Does anyone have an A/B comparison with a DCC vs non DCC version of the "same" locomotive to prove that theory?

When I was at the hobby shop here over the weekend they had some add on decoders for non-DCC locomotives. One of them looked pretty tiny. Would there really be that much required space to put one of those on?
 
Thanks for the info. How does one go about finding out what the production schedules are for any of the manufacturers?
 
FlyFishn said:
Thanks for the info tootnkumin. They don't have any Canadian Nationals though. I sent them a message to see what the scoop is. It doesn't look like Kato may be easy to get in touch with directly.

OK on the pulling abilities. I can understand the size difference - if DCC is really that much "smaller" and/or "lighter" under the hood. Does anyone have an A/B comparison with a DCC vs non DCC version of the "same" locomotive to prove that theory?

When I was at the hobby shop here over the weekend they had some add on decoders for non-DCC locomotives. One of them looked pretty tiny. Would there really be that much required space to put one of those on?
Click to expand...

Difference between DC and DCC is probably very little. Again I speak from the HO point of view. Many brands of HO locomotives have some spare room in the DC versions, so the DCC's are more full due to the decoder only. I can see that N scale would most likely be different.

Thanks for the info. How does one go about finding out what the production schedules are for any of the manufacturers?
Click to expand...

Most manufacturers have up and coming information on their websites. Kato has limited information. https://www.katousa.com/

Willie
 
Most, if not all manufacturers have an upcoming models list/announcement page on their website and email updates. Just Google a manufacturers name and the first one up will give you the web address.
 
Athearn made an N-scale SD75i in CN colors, which is a very close cousin to the SD70M and looks almost identical. It's been out of production for a while, but sooner or later you can catch one on eBay (which is what I did). I have a CN and an Ontario Northland, and they're both good runners that pull well. There has never been a CN SD70ACe in N-scale, which is a completely different locomotive both visually and mechanically than what the SD70M & SD70MAC are. Unless CN buys more SD70ACe (they only have maybe four of them all together), I doubt you ever will see one. There are plenty of GE models (Dash 8, Dash 9, GEVO etc) of CN locos from Fox Valley, Kato, Atlas etc., and those are good looking locomotives. You might also look at Intermountain's SD40-2W, which I think is a very handsome locomotive and they do run and pull quite well. They've also been out for a little while and sold very quickly, so again eBay may be your best bet for those unless you can find an online hobby store that's still hanging on to one or two. Atlas also has several SD60's in the CN colors, but no SD60M if I recall correctly, so if you're wanting the comfort/safety (wide) cab, you may be out of luck there.

As for pulling power in N-scale, it's going to come down to weight of the individual locomotive in addition to the number of axles. An SD90 and an SD40-2 both have six axles, but the SD90 weighs probably 50% more than the SD40, and thus will stick to the rails a lot better, though the SD40 certainly isn't useless by any means. The SD70ACe and ES44's also pull quite well. Any of the four-axle locomotives have smaller bodies and thus lighter weight in addition to less wheel-to-rail contact, so of course they also pull less. You basically have the same or close to the same motor power in any given locomotive within a particular brand, and for that matter even among different brands to a large extent. The big determination is always weight of the locomotive and how well it sticks to the rails.

The type of cars you're pulling will make a difference also. Atlas coil cars weigh a lot more than your standard coal gondola or box car. Having said that, I've never had a problem pulling even the coil cars up a 2.4% grade with two 6-axle locos and my more-or-less standard mainline consist of 24-30 cars. That has more to do with train length than anything else, so I've never just kept stacking cars on to see how many can actually be pulled. Obviously if they can haul that up a grade, they can haul more on a level track. The 2-cars-per-axle formula someone suggested will give you a minimum number you can pull up a fairly aggressive grade, but depending on conditions and equipment you can almost always pull more than that. And again, remember that the 2-cars rule will apply to even a lighter SD40 or U30C. You're always going to be able to pull a little more than that with larger locos such as the big modern EMD & GE units.

As for DCC vs. non-DCC, it makes absolutely no difference in N-scale whatsoever unless you're wanting to go with old locomotives that were manufactured before DCC came about. There are more differences in HO, but all modern N-scale locomotives are manufactured with DC circuit boards for the lighting and motor, and the DCC decoder is simply installed in place of the factory DC circuit board. Or, in the case of Fox Valley, replacing a dummy plug with a decoder plug. There is no weight removed to convert a modern N-scale loco to DCC. If anything, the extra circuitry and components on the DCC decoder means you're actually increasing the weight by some tiny micro-fraction of a gram ;)

Hope some of that helped.
 
Last edited by a moderator:
Thanks for the info. So if I am gathering what you say correctly, it sounds like the locomotives have enough power to break the drive wheels loose? Did I read that right? If they didn't then the same size drive for a dual 4 axle truck locomotive that bogs down, hypothetically, at 32 cars (2x the 2 car per axle rule), wouldn't be able to pull 48 cars (again, 2x the 2 car per axle rule). In fact, with more wheels the available pulling power would be less as there is more driveline resistance, plus more weight for the extra 2 axles, so even more resistance up a grade.
 
FlyFishn said:
Thanks for the info. So if I am gathering what you say correctly, it sounds like the locomotives have enough power to break the drive wheels loose? Did I read that right? If they didn't then the same size drive for a dual 4 axle truck locomotive that bogs down, hypothetically, at 32 cars (2x the 2 car per axle rule), wouldn't be able to pull 48 cars (again, 2x the 2 car per axle rule). In fact, with more wheels the available pulling power would be less as there is more driveline resistance, plus more weight for the extra 2 axles, so even more resistance up a grade.
Click to expand...

If I'm reading you right, you're thinking that if a locomotives wheels can slip under load it's because of resistance in the drive trucks axles/gears etc? That's not the case if that are your thoughts. That happens in the real world too when on a grade and the load is more than the power can handle. It's just physics. The answer is more locos in the model world, just as in the real. With DCC and well speed matched locos, you can add more the power consist (the term for a group of locos under the same control). I regularly run up 5 and sometimes 6 HO locos in a train using a lead group and mid train helpers. Have even split it into a 3 +2 +1 consist with the 6th being a tail end helper. Balancing them throughout the train is the trick in this case to make sure that the couplers on all rolling stock is kept under some tension. It's not quite the same as real life where the last one in particular is actually pushing, but just to spread the effort throughout the train.
 
FlyFishn said:
Thanks for the info. So if I am gathering what you say correctly, it sounds like the locomotives have enough power to break the drive wheels loose? Did I read that right? If they didn't then the same size drive for a dual 4 axle truck locomotive that bogs down, hypothetically, at 32 cars (2x the 2 car per axle rule), wouldn't be able to pull 48 cars (again, 2x the 2 car per axle rule). In fact, with more wheels the available pulling power would be less as there is more driveline resistance, plus more weight for the extra 2 axles, so even more resistance up a grade.
Click to expand...

Yes, the wheels will always slip before the motor will stall, at least in N-scale and with everything operating properly, meaning that the motor is in good running condition and nothing is physically jamming up the internal drive train. Which is a good thing, as it also keeps you from burning up a motor quite so easily.
 
I counted the cars on a train I spotted on Google Earth - 105 behind 3 locos. If the locos are 6 axle units that is 35 cars per loco and almost 6 cars per axle. So that is almost 3x the 2 car/axle rule.
 
Prototype examples are only that, an example. Model locos can vary between brands as to pulling power, i.e. the tractive effort of a given 1/160 ES44AC isn't 1/160th of a 1-1 scale ES44AC, and the weights of the cars don't scale either. It's all trial and error/rule of thumb. About the only thing you CAN copy is the practice the real railroads follow. If there's too much weight for whatever number of locos you have in the train, either take some cars off, or provide more locos. Just as in the real world though, you have to have enough fuel aboard to power them. In the real world that means gallons of diesel, in the electrical model world, a power pack with enough Amps to feed the current required by the sum total of each loco's current draw under full load and the wiring bus capable of distributing it around the layout. Rule of thumb does quite well there as well.
 
A good resource for anyone involved with or interested in N scale is http://www.spookshow.net/trainstuff.hthtml.

This is an excellent place to get answers for most anything pertaining to N scale locos, rolling stock, etc.. I have found it to be very useful, especially when considering buying older items from eBay or private sellers. Hope this helps.
 
Burlington Bob said:
A good resource for anyone involved with or interested in N scale is http://www.spookshow.net/trainstuff.hthtml.

This is an excellent place to get answers for most anything pertaining to N scale locos, rolling stock, etc.. I have found it to be very useful, especially when considering buying older items from eBay or private sellers. Hope this helps.
Click to expand...

The address should be, http://www.spookshow.net/trainstuff.html , you messed up the URL there a bit. Interesting site though.
 
You must log in or register to reply here.



Back
Top