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Discussion Starter · #1 ·
Some HO scale locomotives (regardless of the countermeasures we take) are a disappointment when it comes to pulling power. We all have those.
But we also might all have that one locomotive (or two) that pulls surprisingly well, especially for it's size.
For instance ounce for ounce, my BLI SW1500 by far out-performs any other loco I have.
As an example, to break down a 50-car train with my other 4-axle switchers, would typically be three cuts of 13 and one of 11 (four moves). But the BLI will do it in two.

I'm wondering if there are other "muscle-buses" out there you might be surprised or impressed with... either switchers or haulers, steam or diesel.
 

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for me it's a heisler ... top speed is only maybe 20 smph, and it's brass, so it's heavier than normal ..
 

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Discussion Starter · #7 ·
The whole point of the O.P. is not what you have that pulls the most...
The point is -- what you have that pulls a lot more than you expected.

That's why I made the "ounce for ounce" remark.
My BLI E7's and RSD15 will pull stumps all day long without overheating, but that's about what I expected.

I would expect larger heavier locomotives to pull longer trains. But I didn't expect a 10 ounce 4-axle switcher to handle 26 cars.
 

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I expect my locomotives will pull a lot more coaches than I currently own or that will fit on my layout.

I've seen Roco and ACME locomotives pulling a string of 17 passenger coaches at 85' each up a 3% grade without any indication of slipping or stalling.

Those traction tires and six-axle drive makes a big difference.
 

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I have an old SD60 shell on an Overland chassis from a couple decades ago that I packed the shell with lead. Must weight a few pounds at least. I'll have to put it back in service to see what it can do.
 

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what you have that pulls a lot more than you expected.
prototypes commonly expect the tractive effort (dry rail) of a locomotive to be 25% of it's adhesive weight (weight on drivers when balanced evenly on all drivers). This is often true of models. Using a somewhat more conservative value of 20%, your 10 oz loco has a tractive effort of 2oz

a properly (NMRA recomendation) weighted 6" car weighs 4 oz.

on a 1% grade, the effect of gravity is approximately that % of the car's weight. a 4 oz cars requires 0.04 oz to pull it up the grade. (grade is surprisingly accurate for typical grades)


therefore, with very free spinning wheels, a 10 oz loco with a TE of 2 oz should be able to pull 50 6" cars up a 1% grade.

but i've noticed a lot of variance between trucks. some seem to roll uphill :). I went thru my trucks and tuned them but the best I could make some trucks is to roll on a 2% grade.

Armstrong has curves for both empty and full cars on his chart for trains resistance indicating the resistance/ton vs speed. Full cars have less resistance. So i assume that same truck that only rolls on a 2% < will have less resistance with some weight on it.

regardless, truck resistance will further limit the pulling power of loco on both flat and track on grades.

maybe a good estimate for train resistance on flat ground is a 1% grade

if you had a scale, i'm curious what the resistance of 50 cars is on level track
 

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I have a bli 2-8-2 that pulls a ton more than expected. I also have a northern that’s the same situation by bli. But the one I was most surprised by was a rivarossi 0-6-0 tank Oliver mining company. I did the dcc install and for it being such a light locomotive it has pulled 12 cars and a caboose up a 1% grade before it even thought of wheel slip. And it’s one of the older models of it with the open motor and pizza cutter wheels that have no traction tires on them. I was shocked anyway.
 

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Some of my older single truck locos are surprising pullers, in particular a Tyco c630 and an AHM C Liner. I think it's due to the traction tires. I know a guy who put yep traction tire powered trucks on a c630 and reports that it's his best puller. That's allot of rubber on the rails.

Definitely not my favorite locos but they do pull stumps
 

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Atlas Shrugged!

My Atlas(Austria) GP 38 High Nose....old as the hills, beat to snot, yet pound for pound performs admirably(She's not the prettiest girl at the Ball)....25 cars on a flat surface but as anything realistically I start her as slow as possible and once she gets her dander up...Giver!!:laugh::laugh::thumbsup: My Rivarossi Berkshires which are obviously heavier than the GP..struggle even with new Traction tires!!
 

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Believe it or not and, don't laugh to much but. I have a couple of early 70's hong kong bachmann war bonnet f9's. The ones with the huge all cast, 2 piece chassis. 8 wheels drive, 8 wheels pick up track power. No rubber tires. Those things are monsters at pulling power. Mine are quite quiet too. ( ive heard others say them to be noisy).

My other mule is a blue box sw1500 that I added some 1/4oz stick on weights from the auto parts store up inside the shell.

These guys out perform all my 50's era mantua, gilbert, and bowser steam locos and any other 8 and 12 wheel diesels for car count.
 

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diesel for me

My F7A Athearn super geared and F7B Bachmann Plus.
My shelf layout is limited, but this pair can pull every car I can fit on the shelf and reversing 18" loop.
 

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Weight fraction data?

GregC, do you have data to support your assumption of 25% of the model weight? Because of some other reasons & curiosity, I have been examining how many cars a given engine can pull up a give grade. Because of practical limitations, I am starting at 2.5% and going up to 10%. I could go higher, but it is of questionable value. The intent is not to define a rule for how much grade ca be used, but as the OP indicates, How many cars can be pulled in a idealistic test. I only have a straight track section with nearly constant grade and no curves, ie little track resistance. at 2.5% I am seeing weight fractions that are much larger than 0.25.
Larry
www.llxlocomotives.com
 

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GregC, do you have data to support your assumption of 25% of the model weight?
first, it's a common value used by the prototypes

i've also weighed and measured various locos and read others measurements and would say the range is between 20-30%.

at 2.5% I am seeing weight fractions that are much larger than 0.25.
what do you mean by weight fractions?

i've been wondering what the equivalent grade is to pull a typical train on level ground. i expect there to be variation between trucks. I recently did a pull test on 30 cars estimated to weigh 4oz each and measure 2.4 oz, ~2% of the cars weight. (i expected a bit less)

Using 2% as the rolling resistance on on level track, 25 four oz cars weighing100 oz. have a rolling resistance of 2 oz.

a 20 oz loco has an estimated max TE (20%) of 4 oz.

the resistance of a 100 oz train up a 2% grade is an additional 2 oz. The combination of rolling resistance (2%) and grade (2%) requires a TE of 4 oz. which this loco can provide. This is what I would expect using the above values for max TE and rolling resistance.

it could pull more if the cars have very good tracks and the rolling resistance is less. But if the rolling resistance were zero, the most it could do is a 4% grade.
 

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I am pulling 34 4 oz cars on a 2.5% grade. The rolling resistance of the cars actually is less as the grade increases. The amount of the car weight pushing normal to the track is less as the weight vector has swung away from the normal. The amount of that weight that is resistance is based on the coefficient of friction of the car system. As the grade increases, the amount of friction resistance is reduced. However, part of the weight vector is now directly opposing the drawbar force of the engine. Which adds to the drawbar force required. To take this to a limit, if you tried to lift the cars vertically up a cliff, there would be very little rolling resistance, but you would have to lift the entire car weight. The other compounding impact is the grade effect on the engine draw bar force. As the grade increases, as with the cars, more and more of the tractive force is required to lift the engine weight.


What I have found interesting, is that on all of the engines I have tested this way, The engine by itself can easily climb a 10 - 15% grade. At 10 percent grade, some those engines can pull six cars. Others can not to pull any beyond six percent grade. What I have found interesting is that the amount of velocity degradation for a given supply setting is surprisingly small. The power change is in the current draw. When I'm doing this, I'm holding the supply voltage at 12 volts DC. This is close to what the DCC modules provide to the motor. What this is telling me is that these motors can and do provide an increase in power and thus more drawbar force. This seems to continue until the wheels start to slip. At which point the engine speed drops because the tractive force is not enough.

It is clear to me that the biggest factor is the motor size/capacity. This has to be normalized by the engine weight. However, if the motor is at it capacity, then adding weight is detrimental. Motor performance is not linear, particularly on the edges of the operating envelope.
 
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