Definitive word on grades >2%

In planning my first layout, I've committed myself to sticking with true-scale grades, with nothing to exceed 2%. The problem with that, in the space I have to use, is that it's... ...well... ...BORRRRRing...

I had really wanted to do an over/under, but I simply can't get the elevation I need.

Setting scale-accurate realism aside for a moment, how important is it to stick to the 2% standard? I see that Woodland Scenics makes ramps in 4% grade, and that would definitely give me a lot more flexibility. I've gotta assume that since they make them, it's got to be okay -- yet, I've read commentary elsewhere that would lead me to believe that it's asking for trouble to exceed 2%. I seem to recall reading about difficulties such as having lots of difficulty getting trains started on the steeper grades, increased potential for derailments, and in some cases, trains that simply can't make it up the slope if they are a sluggish runner. How valid is any of that? I mean, if I'm willing to sacrifice the absolute scale-realism, is it really that big of a deal?

 

You'll find varying opinions on this, but I'd say that 3% is likely fine. 4% might work okay too depending on train length. Curvature and curve radius on the grade also have much to do with operational success.

As I plan my new N Scale road, I've used a yard stick with a straight length of flex track upon it to test the appearance and practicality of grades. I stick blocks of wood under the yard stick to approximate various grades and with the yardstick's measurements in plain view, the math is easy.

 

That makes sense. I will try that.

Can I ask you to elaborate, just a bit, on exactly how turn radius affects things? I mean, I think I get it: the loco is working against the friction of the rails more, plus having to go uphill. But is that it? Based on current planning, the elevation change would -- in part-- be going through a curve of 220mm radius (4 Rokuhan R004 sections).

 

I have a Woodland Scenics Scenic Ridge and I've loved every single thing about it EXCEPT THE 4% grade!!! That 4% grade has given me no end of trouble. It has greatlly reduced the locos I have been able to use because some great looking and otherwise great performing locos CAN NOT pull anything up a 4% grade, on a curve, no less.

I don't know how Z locos perform, but I don't know why things would be any better in Z. I have vowed that my next layout will NOT go above 2% grade, and if I want elevation changes (and I do) I'll just have to have twice the length to achieve it.

 

This is good to hear -- thank you for that. It's all I need to hear. I will stick to 2%. With that, I can get up to 1" elevation change, and I'll just call that good. I was finding all sorts of reasons to want to go steeper, but this is the general word I keep hearing: that the limitations and headaches are not worth it.

 

Yes, basically the train wants to go straight and the wheel flanges rub against the rail. The larger the radius the less force against the rail. One way to counter this would be to use super elevated track, R065 in your case. Gravity helps pull the cars away from the rail, lowering the fiction. I did 4% grades on my first layout (along with 145mm curves!) the results were less than satisfactory. I would limit it to 3% on straight and 2.5% on curves.

One thing to consider is lowering one track while raising the other on the approach to the crossing. At 2% you need about 36" on each track.

Mark

 

You hit the nail on the head exactly. In designing my N Scale road, I worked, re-worked and re-re-worked the plan until all my mainline grades were under 2%. My reverse loop (which isn't a loop) is 2.9% and is mostly straight with one short curve. There was just no way to avoid it. However, I'll be able to enter the section from either end, so can route a train via the less-than-2% mainline and descend the 2.9% if I wish.

 

Okay, I am following you here, except for the thing about needing only 36" of track on either side of the crossing. That part doesn't add-up, in my mind. The figure I'm using, for clearance -- the one I've seen quoted before -- is that for Z scale you ought to allow for a minimum of 1.5" of clearance above any crossing. At a strict 2%, that means I should need more like 72" of track on either side -- enough to go up and back down, assuming the two sections connect.

But, honestly, I think I've actually moved-on from wanting the over/under. There are other things I am doing with the plan, now, that I actually find more interesting.

 

I was using 1/38" for overall clearance. It would of course depend on the details of the bridge. Your right, it's 72", it's just that it's 72" with two tracks. For a single track you'd need 144" up and down.

Another thought would be to design 2 different levels.

 

A great point Rick -- that's essentially what I did on my primary track plan to alleviate a ridiculously steep grade on my reverse "loop" section. The mainline rises an easy inch at one end of the connection, greatly easing the climb on the loop. After the notion struck me, I felt like a Civil Engineer working out the track alignments and elevations.

Thanks again for your help with the curved Unitrack bridges on the other thread. I'm experimenting with their use to optimize an alternate track plan.

 

I have an over an under on my 2 x 4 ft layout. the rally important question is what do want to run over the grade, and that more than anything determines what you do . how much linear distance do you have to get the clearance for the train to pass under the bridge, in my case I dun an RDC on this over and under and minimum radius is 175 mm on the tightest loop and 195 at the largest part of route. I do occasionally run steam and diesel but not with more than 4 cars for diesel and 2 shorty passenger cars for steam with traction tires. The diesel and RDC have traction tires. by stretching the fig 8 so it length is maximized in the 4 ft length you get the maximum distance for the climb and descent. In determining the track plan , I use Woodland Scenic's risers and laid it out and ran trains on it before I was satisfied and committed it to the layout. I had a supply of long pins I used to use in building balsa plane models to hold i temporarily in place for trials on cork base.

 

Another problem with curves on hills and curves in general is that your car's center of gravity is no longer in the center of the rails. So long trains with long cars (like passenger cars) are more likely to derail on tighter curves going up hill. I've kept most of my rolling stock to 40ft boxcars for this reason. Long stable trains without problems on corners and less friction on corners for the same reason. Long passenger car's center of gravity on a tight curve going up a hill or not wants to pull the car to the inside of the radius, creating a lot of friction on the inside rail.

Truck mounted couplers also help, even with smaller 40 ft cars. they keep the weight distribution from car to car more true to the truck's articulation point and closer to the center of the track on curves. Body mounted couplers will swing out more on curves. This moves the articulation point of the coupler in relation to the articulation point of the truck away from the center of the tracks on curves (to the outside radius). This makes the train more unstable, more drag and more likely to derail in certain track conditions. Truck mounted couples follow the curve, creating less friction. Exception are on longer cars that use truck mounted couplers but also have a draw bar attacked (again, like on passenger cars). This can also cause problems on tight curves when you add a center of gravity that is far off from the center of the tracks.

-Jon

 

I have a 2% grade on my layout! I have also had problems with long consist and having some cars lighter then others having trouble on curves even if there not tight curves at some speeds. Most of my curves use two section then straight in three or four straight pieces before the turn. my layout uses the set of 4 pieces from 0-8' to 4" then back down in four pieces total of 16 feet. Having more then 23 cars the Engines slow down almost to a stop when climbing! This is a photo taken in 2007 when I first started my first Z scale layout 76" x 32"

 

Oh no! I used the woodland scenics 4% for my design. Thankfully I haven't plastered anything yet. Do you think I'd benefit from tearing it all up and replacing it with smaller grades? It took me so long to finalize my track plan.

 

If it's possible, I'd run your trains on it and see if things are satisfactory. Your environment might be fine and I'd be sad too if you had to demolish your work. I know what you mean about track plans. I've spent oodles of hours working and re-working mine and I'm still not completely happy.

 

Phew! I hope you're right. What do you mean when you say "if [my] environment is right?"

I actually haven't bought an engine, yet. So I guess this will be my catalyst to finally just pull the trigger and do it. (That and finally install my wiring!) I'll just pin some track down and see what happens. Here's hoping it'll work out.

 

Also, I read that MTL locos don't have as much pulling power as AZL locos. Perhaps my choice in the AZL GP38-2 will be OK with the grade?

 

I was thinking of the sort of operating elements we discussed here, such as train length, curvature, locomotive pulling power, type of rolling stock, etc.. I'm an N Scaler, so can't help with locomotive suggestions, but I'm sure someone can suggest a good one.

 

For pulling power check out AZL's first run of GP-7's They pull like no other.
Here is a video of one pulling a 86 car coal train at a show all day for 2 days.




and another video of a pair pulling 130 cars again all day for 2 days at a show