# Rule of "thumb" for length of trains?



## noela (May 22, 2008)

Is there a rule of thumb for the number of cars an engine can pull safely without doing damage to the engine. I have used an Aristo SD45 to pull 71 cars on flat level track. All of the cars have ball bearing and steel wheels and body mounted KD's. The engine did not seem to have any problems, and it wasn't hot, even after running for 15 minutes. I ran it at a scale 40 mph. The reason I ask, I see pictures and videos of 15 or more cars being pulled by 2 and 3 engines. This engine did this on track power, but I have also run 50 cars with battery power with the same loco.
Thank you. 
@import url(http://www.mylargescale.com/Provide...ad.ashx?type=style&file=SyntaxHighlighter.css);@import url(/providers/htmleditorproviders/cehtmleditorprovider/dnngeneral.css);


----------



## chuck n (Jan 2, 2008)

There are several ways that I have used to determine the maximum load an engine will pull. The first is keep adding cars until the wheels on the engine start to slip. My thought is that as long as the wheels aren't slipping the engine is operating within the proper limits. A second method I have used is to get a scale that is used for weighing fish. It has a hook on one end. put the hook on the engine coupler and gradually increase the voltage until the wheels start to slip. Read the weight. That will be the maximum drawbar pull of that engine. Then take 10 or so of your typical cars and determine with the fish scale the weight needed to pull those cars. Divide the engine draw bar weight by the drag of the cars and you will have an estimate of the number of cars that the engine will pull.

I'm sure that there are other ways, but these have worked for me.

Chuck


----------



## Polaris1 (Jan 22, 2010)

I have been to 11 Garden Layouts via Open Houses over 3 years...... and almost 100% of the trains I had seen had 1 engine pulling 9 to 12 Freight cars..... 

This can border on boring... Compared to the double & triple headed trains I see often in 3 rail O Gauge. 

AS for what an engine can do..... 1 diesel should pull 6 Pass cars on the Flat..... Two engines pull up to 12 .. This is For 1 to 1 real Trains... 

A Freight engine should double these Train lengths in G model practicality...... 

Plastic geared G engines must watch their P's & Q's...... Use of expensive BB wheels aids car count while grades hurt car count.... 

Run what looks good on your layout... Run What couplers will allow.... There is no exact Answer to your proposition.... Tight curves hurt car count too.... 

Dennis M from GBay, WI


----------



## Randy Stone (Jan 2, 2008)

Chuck's ideas are great for engines that don't have traction tires on one or more of the drive wheels. But you have a great chance of stripping gears before slipping the rubber tire treads. 

Also, some of the older Bachmann locos would strip the gearbox gears when only 4-5 cars were in tow. 

Another thing to keep in mind is grade. You might get away with pulling 10 cars on level but trying to pull those 10 cars up a grade might end up damaging the gears. 

As for over heating the motor, if you have to have the engine at full throttle to get it to move, then you need to lessen the load.


----------



## noela (May 22, 2008)

Thank you. 
I should have included the video of this run. Here it is: http://www.youtube.com/watch?v=rkIH4llFfRA&list=UUMWrg6CMpI16wI9FOrx-mLQ&index=1&feature=plcp


----------



## Greg Elmassian (Jan 3, 2008)

Big ditto on what Randy said. The "abnormal" grip from traction tires can put way too much load on gearboxes, and also the specific axles that have the traction tires. Ask anyone who has a lot of USAT locos with traction tires and grades. 

I pulled all the traction tires from all my locos to have more realistic results. 

Greg


----------



## bnsfconductor (Jan 3, 2008)

I've pulled 32 cars up a 4% grade with my USA GP9 (w/o traction tires) in the rain. 34 cars caused the train to slip and stall. I wouldn't do it on a regular basis, but that's what I know 1 locomotive will pull. 

Craig


----------



## chuck n (Jan 2, 2008)

A while back there was a related thread. At that time, , using the fish scale method, I measured the pulling power of some of my engines. The table below summarizes the data. The average engine with traction tires (tt) has a pulling power that is about 36% of the engines weight. The average pulling power for engines without traction tires is 33%. It appears on average that traction tires add about 8% to the pulling power. There was not as large a difference as I thought there would be.


Chuck



Number of 

Pulling Power with tt without tt 
Number of Wheels With Weight Pulling Power % of Engine % of Engine % of Engine ENGINE Powered Axles Traction tires (lbs) (lbs) Weight Weight Weight LGB 






AT&SF Diesel 6 1 9.4 2.5 27 27 
Diesel F7a 4 1 8.75 3 34 34 
Mogul (2-6-0) 3 1 7 1.5 21 21 
Mallet (2-6-6-2) 6 2 9.8 3 31 31 
Forney (0-4-4) 2 1 7.6 2.75 36 36 
AristoCraft 






Mikado (2-8-2) 4 0 11 4.5 41 
41 Mallet (2-8-8-2) 8 0 14 5 36 
36 Bachmann 






Climax 4 0 7.3 2.25 31 
31 Consolidation (2-8-0) 4 0 10.1 3.25 32 
32 Mikado (2-8-2) 4 0 13 3.75 29 
29 Accucraft 






K28 Mikado (2-8-2) 4 0 12 3.5 29 
29 K27 Mikado (2-8-2) 4 0 17.5 4.75 27 
27 USAt 






Diesel SD40 6 4 10.4 3.5 34 34 
Diesel SD70 6 0 11 4.5 41 
41 Diesel F3a 4 4 7.5 3.25 43 43 
Diesel F3b 4 4 6.9 3.75 54 54 
F3a+F3b 8 8 14.4 6.75 47 47 average 




36 33


----------



## Greg Elmassian (Jan 3, 2008)

Chuck, from my experience this has a lot to do with the type and condition of the track... oxidized aluminum seems the "grippiest" and stainless the "slipperiest" .... brass seems to be in the middle, and of course polished shiny rail is more slippery than oxidized rail. 

Greg


----------



## NTCGRR (Jan 2, 2008)

amount of cars really changes based on length and weight. 
USAT passenger cars, VS LGB flat cars w/metal wheels. 
My stacked train with all BB wheels VS coal train. 
curve size also. 
I'd rather have my engine slip than stall or short out. 
As its been said many times before. ( one engine can pull the train, two can handle it very nicely). 

In the photo below, the 3rd E unit is depowered. the two lead ones handles the train just fine.

MAN!! they are a good looking set. I wish Greg's photo was in color..


----------



## chuck n (Jan 2, 2008)

Greg, I agree, I should have mentioned that the measurements were done on clean, scotchbrite green polished brass track. All of the engines had many hours of run time, so there was no factory plating left on the engines that came with it (Bachmann).


Oxidized aluminum (corundum) is the second hardest naturally occurring substance know to science. Only diamond is harder. On the Moh's hardness scale of minerals diamond is 10 and corundum is 9. It is also known in the popular world for the gems ruby and sapphire.


Chuck


----------



## Greg Elmassian (Jan 3, 2008)

Learn something every day, never heard aluminum oxide referred to as corundum, but see that it's referred to as "white corundum"... I don't think it's the same material as rubies and sapphires, but it is definitely a 9 on the mohs scale. 

Greg


----------



## chuck n (Jan 2, 2008)

Greg:

Corundum is Al2O3. It can be manufactured and it occurs in nature. Emery as in the type of sand paper is a mixture of corundum and magnetite (iron oxide). Ruby and Sapphire (also Al2O3) are gem varieties of corundum.


Minerals come in many different varieties, for example the mineral beryl when it is clear and pale blue is called Aquamarine and when it is dark green and clear it is called Emerald. Quartz another very common mineral when suitable for use as a gem stone has many different names depending upon it's color and texture.


Chuck


----------



## Greg Elmassian (Jan 3, 2008)

Very familiar with those things (except chemical composiition!), and again another learning experience, you are right, all carborundum like beryl, sapphire, rube are forms for aluminum oxide. 

Actually grew up as a "rock hound" and have collection of gems, have one of everything you mentioned... even my last name means diamond! (almas, elmas) 

Well, should have looked the chemical composition up first I guess! 

Thanks Chuck! 

Greg


----------



## chuck n (Jan 2, 2008)

My original point was that aluminum oxide is very hard and bonds to the aluminum rail, unlike iron oxide (rust). The aluminum oxide protects the aluminum while iron and many other oxides erode the parent metal. Because it forms these micro crystals on the surface, it probably increases the traction. On a mega scale it is like starting a sprint on ice versus a track made of sand paper.

Chuck


----------



## Greg Elmassian (Jan 3, 2008)

TOC has told me that oxidized aluminum has the greatest grip of any rail. All makes sense. 

Greg


----------



## lathroum (Jan 2, 2008)

@import url(/providers/htmleditorproviders/cehtmleditorprovider/dnngeneral.css); I run indoor on Brass track... I can pull 30+ cars with a GP38, or GP7 with no problem... through 6.5' diam curves... and never will the whole train be on straight track ever... my longest straight-away is only 6 feet...

I think it is a matter of what looks good, what isn't boring, and what you like... I usually, because of layout size etc, run double or triple headed trains with about 15 cars...

I use smaller single locos with trains of 3 to 5 cars (or less) running local runs, or switching... 

Philip


----------



## bnsfconductor (Jan 3, 2008)

Posted By Greg Elmassian on 08 Apr 2012 11:27 PM 
TOC has told me that oxidized aluminum has the greatest grip of any rail. All makes sense. 

Greg 
The grade up from Mound House to Confusion Jct, is Dave's steepest section @ 4%, and has a few curves thrown in too. It's kind of the test track for new locomotives at clean up time (that's where I did my test). TOC told me too that's why he went with aluminum because as it gets old the grip gets better (scale sand, with out scale sand?).

Craig


----------

