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Author Topic: Bachmann Steam Locos  (Read 3204 times)
rookie

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« on: October 21, 2010, 04:50:30 PM »

Could someone tell me if it makes a difference in pulling power if the steam locos have more wheels. I think ones with more wheels (drive?) look a lot better. Which numbers do better if any? I am just talking about from Spectrum on down in cost. Thanks, David
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ABC
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« Reply #1 on: October 21, 2010, 05:02:56 PM »

It makes a difference, but there are several factors that affect pulling power. The size of the drive wheels, the size of the drivers, the weight of the loco, the number of drive wheels, etc...
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rookie

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« Reply #2 on: October 21, 2010, 05:16:05 PM »

ABC, so a o-6-o would be better than a 2-4-2 and not as good as, say a 0-8-0? More wheels would add a little more weight, right? Of course, a heavier loco would pull better also, right? thanks, david
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Doneldon

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« Reply #3 on: October 21, 2010, 05:18:10 PM »

rook-

The number of wheels on a loco has a lot to do with the weight of the loco itself.  If a builder tried to put the entire weight on just one or two axles, the rail would fail.  So multiple axles served to spread out the weight to a manageable level.  This went beyond mere rail to bridges, viaducts, turntables and so on.  Essentially, the larger the loco, the greater the pulling power.  But not always.  

Two otherwise identical locos fitted with very large or very small drive wheels will pull differently.  The loco with the large wheels will go very fast but not be very powerful.  The loco with the small wheels will have great pulling power but only at modest speeds.  Railroads purchased or, less often built, their locomotives with this in mind.  If you look at photos of heavy coal drags in the mountains you will see that the locos tend to have a lot of drive wheels, as many as ten, twelve or sixteen, but small ones.  On the other hand, fast passenger trains use locos with large and generally fewer wheels.  Of course, that coal drag might have been 100 or more heavy cars - perhaps 80-100 tons each - but the passenger train was only a handful of cars.  As passenger trains grew longer (and therefore heavier) the locos got bigger, but still with relatively large wheels.  Some of the best examples are the western railroads which had a very long way to go compared to most eastern lines.  The western railroads used huge powerful engines like Hudsons and Northerns with large wheels.  Most of the eastern railroads also used such engines, but the mass and power of the western railroads' locos were typically greater than those of their eastern brothers.

It might seem as though these principles don't apply to diesels, but they do.  The largest diesels have six-wheel trucks, the others four.  This reflects the need to spread the weight.  Incidentally, many six-wheel trucks have only four powered wheels; the center axle is unpowered and only there to carry weight.  As for the size of the wheels, well they're generally the same but one cannot see where the differences are.  Specifically, we can't observe the gear trains inside the trucks.  Locomotives are geared for either speed or power, so you can't just swap one diesel for another.  Additionally, passenger diesels needed steam generators to run the heat and air conditioning in the passenger cars.  Diesels intended for freight use don't include this capability.

This is just an elementary description of loco wheels and sizes, but I hope it's helpful.  Be aware as you plan your layout and purchase motive power that larger locos need broader curves or they will derail.  Large locomotives will also look much better on wider curves.  I suppose most of us love the idea of a huge articulated steam engine racing through a mountain pass but we must do a reality check.  These engines are intended for trains and distances far beyond what most of us can model credibly.  Look to small- and medium-size locos for your motive power unless you are planning a gigantic layout.
                                                                                                                                                   -- D
« Last Edit: December 05, 2010, 03:30:43 AM by Doneldon » Logged
richg
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« Reply #4 on: October 21, 2010, 05:27:31 PM »

I am only talking model trains here.
How even you track is can make a difference in pulling power. How tight the curves are can also affect pulling power. Not always an issue but it  does happen to some at times.
Many have mentioned that having metal wheel sets on your rolling stock can be an advantage. Also, the wheels have to be free wheeling. Just inserting new wheels is not always the answer.
The loco may have the pulling power but plastic wheels can be a hindrance.

Rich
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bobwrgt

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« Reply #5 on: October 21, 2010, 06:19:13 PM »

I would have to say that the Spectrum Heavy Mountain 4-8-2 will pull the most. Large boiler with good size drivers and lots of weight.

Second would be the Light Mountain 4-8-2 or the 2-6-6-2. The 2-6-6-2 has lots of wheels but does not have the weight or drivers to get the power to the rails.

Third The most recent K-4 4-6-2 and 0-8-0 would come next. Both have good weight and large drivers. The 2-10-2 is probably also in this group. The boiler size , weight and drivers limit it's ability to get power to the rails. In addition the center driver is blind so it will make tight curve. Most of the time this driver does not touch the rail for pulling.

Fourth would be the 2-10-0.  Small boiler, little weight, and small drivers.

Last would be the Spectrum 4-4-0 and 4-6-0. Actually the 4-4-0 will pull better than the Low Boiler 4-6-0 because the drivers are larger. The high boiler 4-6-0 has larger drivers and will pull as well as the 4-4-0.

I left out the Spectrum  N&W J because i don't have one of them.

In modeling everything goes out the window as it has to do with the way the engineers put the weight and gearing into the engine as well as DCC may also make a difference.

Life-Like Proto makes some great steamers but they won't pull as well as the spectrum because of the design. Throw in rubber tires and it is another ball game.

Athearn made a 4-6-2 and 2-8-2 but the weight distribution was way off. All of it being on the rear driver and they won't pull well at all.

Bob
« Last Edit: October 21, 2010, 06:25:52 PM by bobwrgt » Logged
RAM

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« Reply #6 on: October 21, 2010, 08:06:06 PM »

another thing to look at is the Spectrum 2-10-0 is a very light locomotive and will not pull much. The Penn RR 2-10-0 are big and Heavy and there for are very powerfull.
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Woody Elmore

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« Reply #7 on: October 22, 2010, 10:08:17 AM »

Also, the bigger the driving wheels the faster the locomotive.  Passenger engines had drivers in the 72-84 inch range.  Switch engines and 50 inch drivers.

However, asking which engine puills the most is a very subjective question; it is like asking' "How big is a dog?"
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ebtnut

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« Reply #8 on: October 22, 2010, 12:50:43 PM »

Some model world basics to keep in mind - The number of drivers is an indicator, but not a determinant.  The more drivers, generally the larger and heavier the model, which would usually equate to more pulling power.  However, factors such as the finish on the driver tires (the shiner, the slicker), rubber traction tires, spring tension (especially on the pilot and trailing trucks) all enter into this.  You can have a good 0-8-0 switcher that might out-pull a 2-8-2 because all of the weight is on the drivers. 
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K487

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« Reply #9 on: October 23, 2010, 08:40:44 PM »

Hey Bob:

I like your Bmann HO steam loco review above.

Could you advise where you would put their 2-8-4?  Thanks.

Doug
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bobwrgt

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« Reply #10 on: October 24, 2010, 08:47:55 AM »

Sorry i don't have any 2-8-4 from Bachmann. Just Rivarossi and Proto. From what i have read they are not the best pullers for their size but others have added weight that works well.
All the light pulling engines can be improved using Bullfrog Snot. It's a coating for the wheels like a rubber tire.
I have used it on the 2-8-2 SY from Bachmann and it works great. The Sy is another not so good puller for it's  size. About the same as the 2-10-0.

Bob
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K487

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« Reply #11 on: October 24, 2010, 04:12:34 PM »

Bob:

Thanks.

Doug
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ebtnut

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« Reply #12 on: October 25, 2010, 01:52:44 PM »

Bob:  Have you made any determinant on the durability of the Bullfrog Snot?  I intend to use it on a loco to solve a shorting problem, and wondered how long I might expect to go between reapplications.
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bobwrgt

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« Reply #13 on: October 25, 2010, 06:17:18 PM »

Can't say. But i know the jar will last me a lifetime. It all depends on how many coats you give it. You can build it up in layers.  I have one engine with at least 4 hrs run time on the original coat.
If you are looking for an insulator between two non moving parts silicon sealer should work.

Bob
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Doneldon

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« Reply #14 on: October 27, 2010, 09:45:11 PM »

BF Snot can be useful, as is adding weight to the loco.  However, be careful when adding weight.  It is possible to put so much weight in that it strains and eventually burns out the motor.  I suggest checking the current the loco pulls when without load beyond its own weight, and then at full stall.  To check full stall hold the loco and push down until the wheels can't turn anymore.  Only do that for a moment as you will damage the motor if you hold it in stall for more than a very short time.  Then add weight until the amperage reaches about the midpoint between the free and stall currents.  Some folks weight up closer to 75-80 percent but I think that leaves too little margin for the load put on by a train.  Good luck with your problem.

                                                                                                                                          -- D
« Last Edit: December 05, 2010, 03:34:34 AM by Doneldon » Logged
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