Making the Grade! How much is too much?

[doctorwayne]

I guess my point is that 2% is much harder then one think, at least I really didn't think it would effect as much as it does. My Bachmann 2-10-2 and 2-8-0 will only make the grade 3 or 4 of those cars. My Bachmann 4-4-0 will not even make it up with one!

Magnus

A 1% grade will effectively halve the length of train that a locomotive can handle, going upgrade.  If you introduce a curve into the same equation, expect a further reduction in train length, depending on the severity of the curve.  Here's a link to a very interesting and useful site:

Railroad facts and figures

As for the downhill surging, it seems as if the advent of DCC has obviated the use of the throttle as the primary means of speed control (I've noticed that some modellers seem to "re-discover" that a throttle adjustment will slow the train when it's running downhill)  First off, the prototype usually has a speed limit on grades:  if you're running fast enough on a 2.5% down grade that the slack is stretched, you're going too fast.  The prototype can stretch the slack, even at low speeds, because the brakes on the cars can be applied independently of those on the loco, a luxury that our models don't have.  So, slow down a bit:  the train should be under control at all times, and this is a good way to learn proper train handling.  You need to match the loco's speed to that at which the cars will roll if there was no loco impeding things, while still keeping within the speed limit.  Without a speed limit, you could simply increase the speed steadily to prevent the slack from running in, and obtain no surging, although it would look pretty silly.  Another cause of surging is excessive gear lash, exacerbated by end-play in the locomotive's motor.  When the train is moving uphill, the gears mesh on the front faces of the teeth.  When the loco runs downhill, a point is reached where the wheels are actually turning the gears - this occurs for only a very brief moment when the gears are very free, meshing effortlessly.  Then, the rolling chassis gets ahead of the motor and gears, with the gears meshing on their back faces.  Friction increases, with the momentum of the train bearing upon the gears momentarily, increasing the load on the motor, which is trying to resist the excess speed and yet trying to overcome the increased friction at the same time.  The result is that the gears act as a brake until the momentum of the train has been reduced, at a given throttle setting, to a speed that the motor can keep up with. Then the whole cycle occurs again and again.  This surging, or bucking, can be reduced by minimizing play in both the motor and the gears.  On most diesels, the only area for easy adjustment is in the motor, where the use of thrust washers can reduce motor shaft endplay significantly.  For steam locos without gearboxes, usually older models, or some of the simpler newer ones, worm-to-wormgear mesh can be adjusted by the use of properly-placed shims.  Most of the foregoing information is from an article entitled "How Locomotives Perform", in the September 1970 issue of Model Railroader.

Wayne 

[Pathfinder]

...

2. The pinion gears had .027" end play. I took 2 NWSL .010" washers and tightened this up. After cleaning all of the garbage and thick grease out of the trucks I reassembled them. I then re-lubed them with a LITTLE dab of Labelle #106 grease. Three years later and I have yet to see any sign of "the Surge".

 What I found later is there was so much play in the gears that the weight of the free rolling cars pushes the locomotives. Then the locos' motors pull in the slack in the pinions and creates a "surge". I have had no surging problems with the rest of my fleet. I have had to replace several sets of plated wheels that have been worn through.

....

What I have read/been told is the above is the most common reason for surging down hill: play in the gears and or motor.  Too much and you get the effects mentioned.  Maybe not such a big deal now with better quality motors and gear boxes but still could be a strong contributor.

[santafemikie]

I have a 48' helper district with a 2.8% grade and 32" radius curves throughout. All of my rolling stock has free rolling wheels and Kadees. I didn't have any problems going downhill until I got a pair of Atlas C30-7's detailed and painted. I had an 18' train of 86' auto parts boxes with those 2 C30's. They went up the hill fine, but coming down, there was a noticable "surge" as they rolled by.

A bit of inspection revealed 2 problems;

1. The nickel plating on the wheels was flaking off. This was interrupting my command control signals. I put NWSL SOLID nickel silver wheels on them and this problem was corrected. The "surge" was better but still present.

2. The pinion gears had .027" end play. I took 2 NWSL .010" washers and tightened this up. After cleaning all of the garbage and thick grease out of the trucks I reassembled them. I then re-lubed them with a LITTLE dab of Labelle #106 grease. Three years later and I have yet to see any sign of "the Surge".

 What I found later is there was so much play in the gears that the weight of the free rolling cars pushes the locomotives. Then the locos' motors pull in the slack in the pinions and creates a "surge". I have had no surging problems with the rest of my fleet. I have had to replace several sets of plated wheels that have been worn through.

If you need any more paticulars, drop me a line.

Mikie 

 

 

[Lillen]

I would also like to ad that grades are fun. It is nice to ad a second engine to push them up. They are a bit of a hassle but not to much and they ad fun, what more could you ask for.

 

Magnus

[tomikawaTT]

At the moment virtually every millimeter of mainline track on my layout is on a grade, mostly 2%.  Some of it is tangent longer than my longest train, some of it is on curves down to 610mm (24") radius.  I run trains of varying consist every day and have never yet encountered surging.

One caveat.  Except for the locomotives, all of my cars roll freely enough that they can descend the grades at faster than prototype speed.  The locos have to hold them back on downgrades.

A second caveat.  I am operating analog DC with plain-Jane rheostat controls and (in many cases) 1960s design open frame motors.  The drives have been tweaked as necessary to minimize worm gear end play, which, IIRC, is a major contributor to surging.

I have experimented with a projected 4% grade, and don't anticipate any problems with it.  The necessary short trains and multiple locomotives (not units! this is steam, folks) are already part of the master scheme, so I rather doubt there will be any surprises.

Chuck [modeling (mountainous) Central Japan in September, 1964] 

[Lillen]

Magnus, it sounds like you are on a mission.  

I never resorted to refinishing the roadbed subgrade when I encountered these problems.  I used thin cardboard, the kind one can cut out of breakfast cereal boxes, to shim under the ties along 4-6" here and there.   Once the rails were in such a way that all my locos would keep their purchase along those places, I would cover everything, shims and all, with ballast and glue it.  To keep things aligned, I would place weights atop the rails while it all dried.  Also, I glue much more lightly than most folks.  Once or twice I have had to lift ballasted rail for a number of reasons, and I was always glad of my decision to only glue the top thin layer of the ballast.

 

I've shimmed that way too. You suggested it earlier on when I first started having problems and it works great. But now I will use the plaster to make it absolutely silky smooth and make it permanent. It just feels better to do it that way but as you say, the card is great. I'm also getting ready to to the yards, one big and one small and this time there will be no problems. I've learnt so much thanks to you.

 

And as you say I'm on a mission, this forum have kept constantly said that it is possible to run trains with out a problem and that is the mission.

 

Magnus

[selector]

Magnus, it sounds like you are on a mission.  

I never resorted to refinishing the roadbed subgrade when I encountered these problems.  I used thin cardboard, the kind one can cut out of breakfast cereal boxes, to shim under the ties along 4-6" here and there.   Once the rails were in such a way that all my locos would keep their purchase along those places, I would cover everything, shims and all, with ballast and glue it.  To keep things aligned, I would place weights atop the rails while it all dried.  Also, I glue much more lightly than most folks.  Once or twice I have had to lift ballasted rail for a number of reasons, and I was always glad of my decision to only glue the top thin layer of the ballast.

[selector]

    Grades on curves?  Maybe this is my problem,   My grade is straight as a string. Would curves in the grade lessen the surging problem?    Sorry,   Don't mean to hijack your thread, Maybe all the info here will help you in the long run.   Let us know what you come up with.      Mike

Yes, if you were making a 4-8-4 slip through a windy series of S-curves with radii below 22".  But if your engines are getting through wider curves, even on slopes, my experience is that surging will not be controlled well by them.

Remember that some commercial track pinches a bit in curves, so the tighter gauge may also contribute heavily to the work that the loco has to perform, particularly on tighter curves where the flanges get bound by the inner head surfaces of the rails.

Same applies to making engines work extra hard upslope along curved grades; if the curve is a generous one and does not reverse itself partway up (snakey), I don't feel that there is a huge encumbrance to the train.  In those cases, the weight of the consist and the grade would be much stronger determinants of engine performance.

 

[Lillen]

Crandell you are right as usual on what you say. There are small spots where the problem is most visible and as you say they are near small dips. I've been working hard to get to every trouble spot. But I still think that there are some differences between locomotives on what they are good at.

So today I bought 10 Kilos of plaster to fix and smooth out every possible problem area. I think it is worth the time to fix the issues rather then live with them. I'm now to a point where almost everything goes problem free. I use only 36" curves since I use large steam and passenger cars.

 

Here is another thought, one should probably try as many different locos and cars as possible when fixing the layout. Because as Crandell says every new(almost) finds a new spot. But with hard work they will be fixed.

 

Magnus

 

[mikesmowers]

    Grades on curves?  Maybe this is my problem,   My grade is straight as a string. Would curves in the grade lessen the surging problem?    Sorry,   Don't mean to hijack your thread, Maybe all the info here will help you in the long run.   Let us know what you come up with.      Mike

[selector]

This is just a personal observation I do not know how this relates to other peoples experiences. I have two PCM y6b's. And as strong as they are, they do not work grades with curves very well. ..

Magnus

I agree with Pathfinder about this.

Magnus, I have the same problem with my 8-coupled steamers.  My Lionel Challenger is smooth sailing all over my layout, but my Niagara and my Duplex seem to slip a bit right in the transition in two spots.  I had to go back and shim up some very slight dips that caused the middle drivers to lose traction.  Once I spent the hour it took to clean up these places, my engines performed much better.  BTW, mine are on curves, too, but broad curves.

Also, Magnus, it seems that every time I introduce a new loco to my layout, despite all the tuning I have had to do for others, I still have to fart around with a section or two.  Funny thing, though, whatever I do for the newbie never becomes a problem for what ran on the layout until that day.  It suggests to me that all the trouble is a worthwhile improvement.

-Crandell

[Pathfinder]

I think the biggest issue will be the transition into/out of the 2.4%, make it nice and smooth.

[selector]

Hey, guys.  All of my engines, whether QSI or Tsunami or Loksound, pick up speed as they commence a descent, and they also pick up speed as they level out after a climb.  In fact, the location of the locomotive is by far the major factor in this phenomenon.  I have a 3% grade througout much of my layout (folded loop with overpass at one point).  My longer trains chuff and struggle up the slopes, but as soon as the engine clears the grade, it will accelerate all the dangling train behind it noticeably.  So, I conclude that the major part of the resistance against the motor and drive comes, in most modest trains, from the loco's own mechanism and its own weight.

As for descending that same grade, they all speed up, but only to a point.  It isn't as if they accelerate until the grade evens out to level once more.   Not at all.  In fact, if I want it to appear to be holding back, I have only to back off on the throttle, and the train will slow on the descent.

Therefore, surging is highly unlikely to be a problem.

FWIW, I have heard that surging is definitely a problem in the AC ops of O gauge.  Those motors do not do nearly the same job of keeping their rotation speed as our DC ones.

[Virginian]

Have at it.  2.4% over 6 feet isn't bad.  I have never experienced this surging phenom (not saying it does not happen - just not to me), but it sounds like even if you did you would practically be out of the graded section by the time it started.

[mikesmowers]

   Surging...  speeds up until it takes the slack out of the train then the cars trying to coast down hill will try to ''push'' the locos there for taking up all the slack. The locos then will slow the cars so there is no slack, the process starts all over again.   Did I explain this so you can understand it?      Mike

[scubaterry]

Mike - What do you think causes the surging?  I have read that
going downgrade gravity wants to push the cars faster than the Loco may
be going.  When the cars do finally bump the loco the loco pulls
in slack causing the surging?  And of course this process repeats
itself until clear of the down grade.  No idea how valid that is
but it sounds plausible.  Do you find that the rolling stock with
metal wheels and very free wheeling tend to surge more than the less
free rolling ones?

On a side note:  A friend of mine bought
me a bunch of rolling stock off of ebay in the last couple of
weeks.  Most was old Tyco not much use stuff but there was a
couple of Mantua 40 ft gondolas that cleaned up real nice.  I put
on kadees, metal wheels etc.  Anyway I noticed on both of the
gondolas there was a bent copper or brass metal strip wrapped around
both axles on one truck and only on one side.  It appeared to be
factory installed but not sure.  At first I thought a current pick
up but the wheels were plastic?  So maybe it was some kind of
speed retarder?? (really reaching here).  Maybe someone can shed
some light on this. 

I want to thank everyone for their input so far.

Terry in FLorida 

[Jake1210]

What do you guys mean by the train "surges?"

[Lillen]

This is just a personal observation I do not know how this relates to other peoples experiences. I have two PCM y6b's. And as strong as they are, they do not work grades with curves very well. I mean, they are not poor but compare them to something else of that size and I'm a bit surprised that they handle that combo so poor. I have a 2% grade and that really effects the, Of course one of them is now broken partly but the other one still works fine. When I pulled ten Heavyweights(Walther's) I have to increase power to maintain speed in a way that my PCM Big boys just don't need. But perhaps I'm complaining to much, they do make it and they handle a 9 foot train without stalling.

 

I guess my point is that 2% is much harder then one think, at least I really didn't think it would effect as much as it does. My Bachmann 2-10-2 and 2-8-0 will only make the grade 3 or 4 of those cars. My Bachmann 4-4-0 will not even make it up with one!

 

Magnus

[mikesmowers]

  I can't answer your question 100% but I have a 2.5% grade that is about 14' long and like you said the HP going up the incline is not a problem. The train going down the grade does surge, I will start to surge about 1/4 to 1/3 of the way  down the incline and by the time it gets to the bottom it is really getting bad. You can sort of control it by playing with the throttle.  The longer the train the worse it is, and I like pulling at least 18 cars but would like to pull in the neighborhood of 30 using 2 P2K BN GP38-2's.  Here lately I have not been using the upper tracks because of the surging problem.  I will be watching this thread closely to see if I can pick up any useful info.   I would think you should be pretty good no longer than your incline is.     Hope this is of some help.   BTW  Some locos are worse than others.         Mike

[Jake1210]

You should be just fine. Joe's Siskiyou line has a ruling grade of 2.5% on rice hill for quite some distance. (correct me if I'm wrong, Joe) You may need a small helper, but that should be no problem.

[scubaterry]

I was putzing around with my layout design on XtrackCad again last
night.  With the help of Crandell (Selector) I was able to make a
simple addition to the plan to enable the ability to turn entire
trains.  (tks Crandell).  Of course there is never a free
lunch.  To make this addition workable I ended up with a six foot
stretch of track with a 2.4% grade. Now this track will only be used
for trains that are turning and is not part of the main.  My last
two layouts were plywood flat so this one has lots of rolling hills
anywhere from 1.3 - 1.8 % grades.  I have read that on steep
downhill grades the roling stock tends to surge.  So my question
is?  How much is too much.  Will I most likely have problems
with this short section of 2.4%?  Or am I being paranoid?  As
far as horsepower climbing the grade I have more than enough.  PCM
2-8-8-2, IHC 2-10-2, P1K C-Liners two A's and one B.  These guys
can pull stumps.  And my favorite an A-B-B-A consist of P2K
F2's.  All of my loco's have sound and hearing that A-B-B-A
consist rumble by is awesome.  Anyway any feedback or advice would
be appreciated.  I'm still about two months away from actual
construction so I have lots of time to get this one right.

Terry in Florida