What grade to model Tehachapi?

This is a question for those experienced with long N scale trains on steep grades. A recent article in great model railroads 2009 got me thinking about the best way to model this scene. What radius and grade do you think would replicate the Tehachapi loop best in N scale? IIRC the prototype is about 2.5 % , would N scale act similiar on 2.5% or would there need to be a grade correction made to compensate for the scale effect? As anyone who has been there knows the trains would be long with multiple units on the front, middle and rear ocassionally. The layout space is quite large so the loop can be any diameter but the reach distance becomes a problem if it's over about 6 feet diameter although I guess something could be worked out to allow scenery construction in the center . Regards, Dave Branum

 

Check to see if there is a Yahoo group for the Tehachapi. If none, join the Cajon Pass group and i'm sure you'll get plenty of help.

 

Rick is right - the Loop itself is about a 45" radius in N scale. The separation of the tracks at the crossing is about 77', or 5.75" in N scale. This makes for a grade of roughly 2%. I think there are some spots on the line that are as steep as 2.5%, but mostly it's in the 2% range.

For a model Loop, something about half this size is pretty decent looking. The most obvious compromise is the height of the crossing unless you really steepen the grade (not recommended).

-Gary

 

Hi Gary, I wouldn't have a problem using 45 inch radius (other than access to the center for scenery construction) Do you think N scale trains would perform close to the prototype on the 2% grade? Would they need the same amount of helpers as the real trains if they were scale length? I don't have much experience with N scale trains, only a few feet of level test track set up on the front of my O scale shelf....dave

 

N scale trains will NOT perform equal to the prototype, they will need a lot more power. With a 2.5% grade you will need something like 1 loco per 10 cars.

I should measure the dimensions of our model of the Loop at the GSMRM. From memory, it is about 3 inches with about a 22" radius. Our grade is probably slightly above 2%. The longest train I have run up it was probably about 14' long, enough to cross over itself. That's less than half a scale mile long. It needed four good Katos. We have other places on the layout that limit train length on the layout more than the loop, however.

Remember that the closer you make it to prototype dimensions, the longer your trains will have to be to achieve the spectactular crossing-over-themselves effect, and the harder that will be to do both in terms of power and in terms of having room for those trains on the rest of the layout.

At one point for fun I sketched the loop in XtrkCAD for fun, at about %70 scale, with a 30" radius on the east side of the inside track. (The radius gets larger on the west side as it heads uphill towards crossing-over point.) On such a loop, a train would have to be about 16' long before it started crossing over itself, and you could get almost 4 inches of rise at a 2% grade. I speculate that this is about the max size one could do in N and still manage to have fun running trains on it.

 

ctxm - here are a couple of drawings to help you visualize a mini-Loop. The first shot shows the planned Loop portion of my layout-in-progress:


In this plan, the mainline (inner) loop is 21" radius and a 2.06% grade (according to 3rdPlanIt). The height of the crossover is just under 3" or 40 scale feet. Here is a screen shot of a 16' rack train just about to cross over itself (the loop circumfrence is ~13'):

As long as you don't look at this scene side by side with a prototype photo, you can almost imagine it's about right... but I like Ben's idea of a 30" radius and 4" crossover. I wanted to include as much of the approach to the Loop as feasible in my plan, so I kept the curve radii to just under half the prototype size.

Ben - I never quite registered that you were with the GSMRM club. I visisted it last year when I was out that way - very nice Loop scene! You should post some pictures here.

Cheers,
Gary

P.S. Be sure to check out Dave N's Tehachapi layout:

http://www.trainboard.com/railimages/showgallery.php/cat/870

Unlike mine, his is real!

 

Yes, the loop was a big incentive to join the club!

Here are a couple poor quality pics taken with my cell phone, but you can get the idea of the loop size. (Unfortunately, from this vantage point the access hatch is real obvious too. The public can't really see it from the aisle.) Both these trains are about 11' long, so you can see it would take a few more cars to cross over themselves. I guess our radius is actually probably closer to 24".

I have to remember to bring the real camera one of these days.

 

HI Gary, Thanks for the graphics. Yes, I agree that it looks great with the approaches in the correct relationship. Do you have a complete layout track plan yet?
I have a 32 by 36 foot building available but I'd like to keep part of it open for a workshop so I'm thinking of designing something horse shoe shaped around the outer walls. I guess at some point the climb would get the track high enough to double deck some areas for more length . The problem seems to be the climb at 2% will make the track get too high on a long run, so maybe I'll need to cut down the grade in hidden areas?
I'm just beginning to work this out, I've got a few other possibilities for this space in various scales. Each scale has it's own advantages and I think the possibility of the long mountain run is N scales string point.One problem I'd have is getting enough locos and cars to make up trains since this is a very busy line.
The scenes I'd want represented are ATSF yard/Amtrak at Bakersfield, ATSF/SP junction,some industrial switching in Bakersfield, Edson,Caliente,Bealville/cliff,Keene,Woodford,the Loop,Marcel,Cable,summit,Monolith,and Mojave. Sounds like a lot but with a long winding route it's probably possible?
Regards, Dave Branum

 

Hi Rick, Here's one I took from a little higher on the hill a few years ago, the train is very long, one end is down by the highway in the distance, the other end is out of scene to the left. Go back sometime and wait for a train! The sight is amazing and the sound fantastic.
The quality of this shot is poor because it was done with a disposable film camera then scanned :>) ....dave

 

Here's Walong from my vantage point...



I was working a helper several years ago and took some shots on my way back down the mountain. We headed in at Walong for this empty grain train. The pass is mostly 2.2-2.3% with a few spots of 2.5-2.6%.

 

Joe - I am so jealous! Just out of curiosity, where are the steeper sections of the line located?

Dave - I posted a track plan in a Tehachapi thread a few months ago (a thread started by you, I just noticed!):

http://www.trainboard.com/grapevine/showthread.php?t=99234&highlight=tehachapi

Some of the details have changed since then especially in the lower level terminal layout (and a great deal of progress on room preparations have occurred). The basic features of the mainline are 1) a run from Ilmon to Cliff on the right side with a steady 2% climb (~42" to 60" in track elevation). Then it disappears into a 4 turn downhill helix to reset the elevation and emerges at Woodford on the left side for the section from upper Woodford to Tunnel 10 (~51" to 63" in elevation). If I didn't reset the grade midway I'd be in the living room upstairs... The overall room size is ~25'x25'.

Ben - nice shots, especially for a cell phone. I think that looks like a good size for a model Loop. Do you have any problems running 14' trains on this part of the layout? (That's roughly what I'm aiming for.) Also, how does that access hatch work out? Is it frequently needed? Anything about it you would change?

Thanks,
Gary

 

Hey Joe, did you ever get close up shots of the signal bridge at Walong? I remember a thread about that, I think Bob from Traincat wanted to produce a kit?

Just curious, since as you can see we still need to model that bridge...

I've run 14' trains through our loop on probably 3 or 4 occasions total, and in all cases it went smoothly. I've also string-lined shorter trains a couple times, but I put the blame for that on bad order rolling stock (one case was a hanging trip pin).

Note that our loop uses curved turnouts, whereas the prototype has S-curves in the siding. I don't know how important that is, but it might turn out that if you do it like the prototype, you want those long uphill trains on the main.

I think I could probably haul a 16' or 17' train through this loop if I carefully inspected every car beforehand and made sure they rolled properly. (Unfortunately, such trains would have to come or go from either from a staging yard which can't handle such a long train, or through an 18" radius, 3% grade section. That's the weak link the chain. Plus, a lot of our sidings are only 10' or less, so running a train that long really monopolizes the layout. I wish we had a couple extra feet between our "tunnel 10" portal and the staging yard, so that one could get a train all the way into the tunnel and then break it up into the yard.)

The hatch...yes, it's gotten used a few times when I string-lined those trains! But mostly it's used when we do work on this section. I'd say we're lucky and it doesn't get used too often. It works pretty well, it's held in place underneath with barrel bolts and is removed downward. I wish it weren't necessary, but I think it would be hard to avoid with a loop this size, even if we didn't have ours smashed up against a wall. As i said, ours is not visible from the aisle, which is nice.

 

Gary, between Ilmon and Caliente, Cliff and Rowen, Woodford, and from about tunnel 14 to just below Cable Crossover are all pretty steep.

Ben, no shots of the signal bridge:tb-sad:

 

Hi Gary, I remember your layout from last year. I really like the track plan and the realistic track design in the modeled areas. I like the idea of the helix to drop back down between scenes, it will also add some hidden running time and train length capacity which will be useful.
Do you have any updated drawings showing your benchwork and aisle outlines? It looks like you don't have any access to the inside of Calinete curve and the train watching spot by the old depot? Do you plan to view that whole scene from up above the tracks heading up hill from Caliente toward the tunnel 2?
Have you experimented with N scale locos on the 2% grade? Do they run downhill allright in multiple unit consists? Is there enough drag on an uphill train to slow it down on a 2% grade so helpers are more than cosmetic? I only have one N scale loco and a short flat test track so I can't do much testing :>) . If I do build a layout like this I'll probably have to beg folks to bring over their trains to run.
Regards, Dave Branum

 

Before you get too set on modeling Tehachapi, you should consider that there really isn't anything to do on the mountain. Very successful clubs that have the loop in their plan also model large parts of the yards at both ends to create the switching you will likely want once you have watched the train squeal around the loop for a while. :tb-biggrin:

 

I would agree with keeping your grades to 2%. The actual grades over the Tehachapi pass are 2%. Originally there may have been some 2.5 and possibly a short 3%. Most of these were eradicated when longer trains, heavier and taller train cars came into play. Historically, Not much is mentioned about the improvements. Most of this took place about the time Santa Fe gained trackage rights. The rumor at the time was Santa Fe paid for the improvements.

I might suggest a staging yard where you can prepare various trains to operate over the pass. I've done that on mine and it works when you are attempting to entertain a guest or two.

Edited add on: You can credit Joe Gartman with the present day facts. I wasn't aware that the route still had some 2.2, 2.5 and 2.6 gradients. Interesting. No intent to mislead meant here. Thanks Joe for your input.

Have fun.

 

Hi Tony, Yeah, I've spent quite a bit of time watching trains in that area so I know what to expect.
I'd model the passing sidings at a few spots on the hill to kill time, add and subtract helpers, switch the monolith cement plant, switch edson, model the east end of the ATSF and SP yards and some industrial trackage in bakersfield so I think I'd have plenty to do.
My biggest concern would be getting enough rolling stock to create the trains needed, but it would certainly be fun to see the oil cans or an SP lumber drag attack the hill again or watch the big blue GE's snake a Santa Fe train thru Marcel again. Regards, Dave Branum

 

Dave:

I have some sketches of bench work that I can post when I get them a bit further along. I am definitely planning access points in the Caliente leg both in the curve and further up between Tunnel 1 and the canyon below (roughly where the Bodfish road runs). The planning has stalled a bit at laying out the lower level staging in a way that is accessible, interesting to operate, and doesn't sacrifice the layout of the mainline run too much.... Overall, I'm going for a schematic something like this:


where A' would loop back to A, and B' back to B. In the plan I posted before, the yard loop in the middle of the room represents the UP terminals, A & A'. Given the grade, there is about 12-14" of clearance between the yard and Bealville above. I am in the process of mocking this up with some temporary bench work to see how it works in practice, but that effort is competing for my time with basement renovation work, actual modeling, etc.

As far as an ops concept, I am mostly interested in managing 2-way traffic on a single track mountain line (and watching said traffic!), less so in switching, so I think this schematic fits the bill nicely. While the square footage is rather large, the plan itself is rather simple - very few turnouts, structures, trees, so I believe it should be possible to pull it off in less than half a lifetime...

I can't comment on how well trains will actually run on these grades/curves yet.(!) I think Ben's experience is as good as any, and while I'm sure the trains could benefit from helpers/DPU's, I'm not at all confident that it could be pulled off reliably. Anyone have any positive experience with this?

Best,
Gary

P.S. Thanks for the responses Ben & Joe.