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Author Topic: Steam locomotives  (Read 13550 times)
SteamGene

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« Reply #15 on: September 05, 2007, 09:38:12 AM »

Inder,
As Bob says, there is no real connection between what a real locomotive pulled and what a model does.   I am quite satisfied by what my Spectrum 2-6-6-2s pull.  Part of the marvel of the Spectrum 2-8-0 is the fact that it was the FIRST well detailed plastic model that performed well that was also well known.  Before that, most plastic steam locomotives were poor performers, with Bachmann being at the bottom of the list.  So when the 2-6-6-2 came out many were perhaps expecting even better performance and were let down.
One current member, Sheldon, IIRC, has done some investigating on the theory that, with a model, the more drivers, the less tractive effort.
Gene
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Virginia Tidewater and Piedmont Railroad
"Only coal fired steam locomotives"
Stephen D. Richards

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« Reply #16 on: September 05, 2007, 12:22:22 PM »

Gene, that is very interesting!  I would tend to assume (yeah I know about assuming) the more drivers on the rail, the more traction!  Seems like a law of physics would apply here, unless of course it is directly proportional to the model locos weight! 

Sheldon, if you have any info on this as you did with the wheel sets, trucks, etc, I would truly be interested in seeing your findings!  This past Winter helped my immeasurably.

Stephen
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SteamGene

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« Reply #17 on: September 05, 2007, 12:54:26 PM »

Stephen, it just struck me that the reason is the sharing of the locomotive weight. Remember that Roger among others advocates removing springs from pony and trailing trucks to increase tractive effort.  Well, consider a model locomotive weighing 12 ounces.  If it has six drivers, each one supports two ounces, while if it has 12, each supports only one.  IIRC,  what counts for the real railroads is the amount per axle and not a multiplication of that. 
Granted, I'm not a physicist.
Gene
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Virginia Tidewater and Piedmont Railroad
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Stephen D. Richards

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« Reply #18 on: September 05, 2007, 04:03:14 PM »

Gene,  I think I am getting the hang of this, that makes sense!  Removing the springs makes even more sense!  So by this train of thought, (pun intended) I should be able to increase the weight of the over all locomotive and proportionally increase the tractive effort!  I understand that the more wheels on the rails the less axle weight they have on the rails!  Revelation here...similar to tractor-trailers on the road.  The more axles the more dispersed the weight!  Ah, slowly but surely.  Stephen
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Atlantic Central

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« Reply #19 on: September 05, 2007, 05:33:11 PM »

OK, here goes a basic explanation.

Physics does NOT scale down, if it did our models would pull as much or more than their prototypes because they are actually as heavy or heavier in scale proportion terms.

But, the coeffiecent of friction between the rail and the wheel does not scale down, so our much smaller wheels and rail are much more slippery.

So model steam locomotives that put all or most of their weight on just two axles pull better pound for pound than those with the loco weight distrubted on 3,4 or 5 axles, because greater weight concentrated on fewer wheels means less slip and more grip. Also the very way steam locos go around curves means a loss of adheasion, and our curves are much sharper than the prototype, making that worse. The two axle weight bearing makes this less of a problem as well.

Diesels don't suffer from these problems near as much, so they pull better.

My research into this showed clearly that 4 axle locos with two rigid alxes and the other two loosely sprung or floating so no weight was on them, pulled better than simalar weight locos with all the drivers sprung, evenly distrubting the weight.

Most model articulated locos have very little weight on the front set of drivers (regardless of mechanism design), and therefor only pull as well as the weight on the rear drivers allow.

Rolling resistance of cars has a lot to do with pulling capacity as well. I have done much study in this area also. With free rolling cars, train lengths up to 30-60% of prototype practices are possible.

On level track, a Bachmann 2-6-6-2 will pull about 130 oz of rolling stock with very free rolling trucks. That is equal to about 40 avarage freight cars, or about 1/3 of what the prototype could pull.

The best pullers by far, are those locos with most weight on only two axles and traction tires on the rear weight bearing axle. Some on this board will rail at the idea of traction tires and that is their right, but physics does not scale down and those of us interested in at least approaching scale train lengths are generally happy for MODERN traction tires on this new crop of locos.

Several have commented about prototype train lengths vs model train lengths. And, while I agree that model layouts often can look overwelmed by excessively long trains, many modelers settle for the opposite extreme.

A 2-6-6-2 or big 4-8-4 pulling 12 cars (on ANY layout) looks ridiculous. If you are going to settle for 12 car trains, settle for a 2-8-0 as well.

Here is my guidelines for model train lengths that look reasonable an are doable on medium sized layouts and above:

Mainline, class I train, locos as noted -

2-6-6-2 or 2-8-8-2 pulling 35-40, 34' hoppers

Two, 2-8-0's or 2-8-2's pulling 30-35, 40' and 50' merchandise cars

4-8-4 pulling 25-30 freight cars or 7-9 passenger cars

2-8-0 pulling 18 cars, local way freight

4-6-2 pulling 5-8 passenger cars


If your grades are steep you can justify doubling your power more so than shortening your train. It took three or four 2-8-8-2's to pull/push 70 hoppers over the Allegheny summit on the B&O, but they never would have thought of leaving the yard with only 16 hoppers behind one loco.

So on that note, I run 35-40 car hopper trains with two 2-8-8-2's on the head end. They look great.

Well just my thoughts for those who are interested. Mostly just run trains, build trains and have fun.

Sheldon

« Last Edit: September 05, 2007, 06:51:25 PM by Atlantic Central » Logged
thirdrail

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« Reply #20 on: September 05, 2007, 07:17:21 PM »

You asked several questions about the prototype that were not answered. As to the time it takes to "heat up" a steam lcomotive from a dead cold start - no less than four hours up to 12 hours. For this reason, most roundhouses had access to steam lines that charged the boiler with steam at the same time as a fire was built. Without this, building too hot a fire could cause great differences in the metal temperature at various parts in the boiler, causing leaks or metal fatigue.

Most locomotives required water every 25 miles when working a heavy train, and coal every 100  miles. Since early steam locomotives usually could run no more than 100 miles without requiring mechanical repairs, divisions were 100 miles long. A few railrads, NYC, PRR, B&O and a few others, had scoops under the tender and long track pans, permitting trains to scoop water into the tender at speed, eliminating the need to stop every 25 miles for water. Others put humongous 16 wheel tenders behind their steam locomotives.

One used to figure maximum speed as the driver diameter in inches, but the N&W "J" had 70 inch drivers and could do over 100 MPH. OTOH, most Shays had 36 inch drivers and topped out at 15 MPH.
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Stephen D. Richards

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« Reply #21 on: September 06, 2007, 10:39:30 AM »

Sheldon, thanks for the info.  Makes sense!  BTW, I did apply and test your data from last Winter on the free rolling cars issue.  I think I may have topped your data but only on level grade.  I used an Athern 4-8-8-4 and managed to circumvent my layout (175 feet of track) one time pulling 75 different types of freight cars without the train uncoupling or derailing.  The 4-8-8-4 was the only steam engine that I have that could do that.  I have a 2-10-4 and it did almost as well but the 22" radius turns was not very friendly towards that engine.  I have managed to pull over 100 different freight cards with a very large and heavy diesel but would only make one or two circuts before derailing!  Only did this to research and "just to see what I could do".  However, I also ran some "stock" cars and I could not accomplish the same results.  Have to have Kadee couplers, preferrably semi-scale!  Your recommended wheel sets and trucks, and very level grade!  It is interesting to see the results.  Thanks for all your assistance.

Stephen
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Inder


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« Reply #22 on: September 07, 2007, 02:55:39 AM »

Thank you all for your information.
Thirdrail.  I had never heard that steam locomotives scooped up water from below.  That's pretty ingenious.  I thought they simply stopped and filled up from water towers.  Back in the day I'm sure only upper class could afford first class and they were probably divided into several classes.

I bought a DVD of the mexican railroad called "Pacifico"  and this was video taped in the 90's.  Well they were still communication via telegraph relay.
Now I'm sure in the US they probably have a permanent computer link via satellite.  But it's interesting to see how some old systems and some really old engines are still being used elsewhere.  The reason why I dropped 30 dollars on the DVD is because I grew up in Mexico and I lived real close to the train station so I spent a lot of time watching the train go by.  I used to put money on the track so the train would flatten it.  That somehow never got old growing up.  I should have bought a DVD on steam engines but I figured, sooner or later I will have them all.

I was doing some work in Durango Colorado and I had the privilege of watching their steam engine make its rounds.  I didn't have time to actually ride it but it was a very special moment for me to watch it ride past me from just a few feet away.  I felt shivers down my spine.  It actually looks like a living machine.

I can't wait to get my hands on my spectrum 2-6-6-2.  I was interested to see how many cars it could pull but it looks like that's already been done.
But as I build my railroad I will follow the following suggested numbers:

2-6-6-2 or 2-8-8-2 pulling 35-40, 34' hoppers
Two, 2-8-0's or 2-8-2's pulling 30-35, 40' and 50' merchandise cars
4-8-4 pulling 25-30 freight cars or 7-9 passenger cars
2-8-0 pulling 18 cars, local way freight
4-6-2 pulling 5-8 passenger cars

I wonder what it was like, preparing an engine for the morning trip.  What was it like when a locomotive broke down in the middle of nowhere?  What was their plan B?  Would they send out another locomotive or would they send horse carriages?  What was the customer service like then?  I'm sure people had a little more patient that now.  It was a much slower paced world.

Anyway this is all very awesome to me.  I was about 5 when my step dad showed me his N scale collection which comprised of a 0-6-0 switcher.  A few boxed cars and a caboose.  Also there was another locomotive without the shell and it didn't work.  I was hooked.  I knew that sooner or later I would have to have my own collection.  And the time is now.  I am 30 years old and I decided it was about time I start.
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JEPProperties

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« Reply #23 on: September 07, 2007, 05:03:19 AM »

If you would really like to learn about steam locomotives go to this link :

http://www.history.com/search.do?searchText=trains+unlimited&targetDB=THC_SPIDER_V2

and consider purchasing “Trains Unlimited” and “When Giants Roamed” in the Store section on the right of the webpage. The phrase “excellent viewing” is not good enough. If you love steam train engines the way I do you will watch these over and over. The cost is well worth in my book.
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ebtbob


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« Reply #24 on: September 07, 2007, 06:39:15 AM »

Inder,

       As you plan your railroad,  remember something.    The number of cars any of your engines will pull will be dependent on certain facts,  some of which I alluded to before.   For a road engine,  do you have grades?  If so,  how steep?   Also,  and it is always something that gets mentioned on this board,  the pulling capacity of an engine can be drastically changed just by how well your freight and passenger cars roll,  let alone their weight.   The rolling capacity will affect engine performance more than anything else,  in my opinion,  be it right or wrong.  Like I said before,  as you build your railroad you need to keep these facts in mind.
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Bob Rule, Jr.
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SteamGene

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« Reply #25 on: September 07, 2007, 07:31:59 AM »

Inder,
Bob is correct.  In addition, consider how large an area you have for a layout.  That should have a big bearing on the length of your trains.   I'm building what is probably a fairly large home layout and I'm not planning on anything longer than about 20 cars, plus locomotive and caboose. 
I've never heard of a steam locomotive breaking down.  They did derail or explode from time to time, but other than throwing a rod, I'm not sure what else might happen.  Remember steam in the U.S. didn't go out until the '50s.  Few folks were still using horses as primary transportation then. 
There were very few railroads that took on water from track tanks, the PRR and NYC being the only two I'm sure of.   As a rule, water got replinished while the tender was stopped.
Gene
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Chief Brass Hat
Virginia Tidewater and Piedmont Railroad
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BaltoOhioRRfan


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« Reply #26 on: September 07, 2007, 08:22:38 AM »

Gene, B&O also took water from track pans. Theres a picture in a B&O Book i'm reading that shows the 4-6-4 Lord Baltimore taking water from the track pans. I wouldn't want to be standing next to it when they do it though. (Book is called Royal Blue Line by Herbert H. Harwood, Jr.)
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Emily C.
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SteamGene

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« Reply #27 on: September 07, 2007, 09:07:15 AM »

I think they were all in the East.  I'm fairly sure that most of the "on the fly" tenders were for passenger trains.
Gene
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Chief Brass Hat
Virginia Tidewater and Piedmont Railroad
"Only coal fired steam locomotives"
Inder


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« Reply #28 on: September 07, 2007, 05:41:23 PM »

I would like to see that picture BaltoOhioRRfan.

What is the name of the book?

So does it splatter the water all over the place as it scoops it up?
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SteamGene

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« Reply #29 on: September 07, 2007, 05:58:37 PM »

The scoops of the original experiments were torn off the tender when they hit the water.  They finally came up with holes that relieved pressure, allowing some water to escape - sort of like a recoiless rifle.  IIRC, the pan was about a mile long, with a sign telling the fireman when to lower the scoop.  It did splash water out to the sides.  The locomotive had to be going a specific speed so the scoop lowered in the tank and raised before the tank ended.
Again, very uncommon in the U.S.  though I've been told they were common in the UK. 
Gene
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Chief Brass Hat
Virginia Tidewater and Piedmont Railroad
"Only coal fired steam locomotives"
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