Author Topic: Best Of Tehachapi Layout research help wanted  (Read 28442 times)

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kiwi_bnsf

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Tehachapi Layout research help wanted
« on: January 25, 2009, 06:01:31 PM »
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Hi there!

I am based in New Zealand and I only get to railfan in the USA once a year when I visit San Francisco for the Apple Worldwide Developers Conference (I work for Apple).

I am in the process of building an N scale model railroad that covers the Tehachapi line from Bakersfield to Mojave. I've been gathering lots of research material, but one major gap exists. I am really struggling to find many photos or info on BNSF's Bakersfield yard.

My layout is set in 1998-1999 because I love the variety of the immediate post-merger era and want to be able to model helper operations and run locos in SP and Warbonnet paint. I have managed to find out that Amtrak operations at Bakersfield were operated out of the F street Station right opposite the BNSF yard throat until this was replaced in 2001 with the new station further East. I have gathered photos of the old Amtrak station off trainweb, but I can find precious few photos of the BNSF yard itself. Google Earth shows the present track layout and I can see the old depot, and it looks like the West end yard limits cross a river.

Is anyone on this list familiar with the BNSF yard in the late 1990's? Specifically I am interested in info on the Amtrak trains and BNSF yard operations. Also was there any engine servicing by BNSF in the yard? Were helpers cut on or off here? Any help would be most appreciated.

I have about 15 feet of layout space to model a condensed version of the yard and I think I should be able to pack in the Amtrak station, mains, 4 staging tracks, and 6 classification tracks plus some representative service tracks. It would be great to get the track plan as prototypical as possible.

The remainder of the track plan is pretty much finished with plenty of photos and DVDs available with shots of Mojave Yard, Summit, Walong, Cliff, and Edison (the other locales I'm modeling).

Thanks for your time.

Cheers

Tim
« Last Edit: October 11, 2015, 05:09:46 PM by tom mann »
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Tim

Modelling Tehachapi East Slope in N scale circa 1999

GaryHinshaw

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Re: Tehachapi Layout research help wanted
« Reply #1 on: January 25, 2009, 10:08:23 PM »
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Tim:

You might try Joe Gurtman (sp?) over on Trainboard and/or the A-board (maybe he reads this too?).  He is a BNSF engineer based in Bakersfield so I would guess he would be able to help.  On this board, tehachapifan, James Costello and Ed Nadolski are also potential fountains of Tehachapi wisdom.

Have you posted the rest of your plan?  I'm developing a Tehachapi plan too, but mainly concentrating on the over-exposed mainline stretches from Ilmon to Cliff and from Woodford to Tunnel 10, but in a 25x25 space, so there is room to spread out.  I'd love to see what you're planning.

Gary
« Last Edit: February 02, 2009, 04:31:03 PM by GaryHinshaw »

kiwi_bnsf

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Re: Tehachapi Layout research help wanted
« Reply #2 on: January 26, 2009, 01:55:46 AM »
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Hi Gary,

Thanks so much for the pointers. Glad to hear you are planning your own layout. I have posted on Calrailfans and trainboard as well, and a few helpful souls have already pointed me to some resources.

My layout space is a narrow L-shaped room approximately 20' down each side with width of 5'. I have planned a shelf layout that is double deck on one side (Bakersfield on the lower level, Mojave on the top), and then climbs 3% between the levels on the other side. The line is selectively compressed: Staging -> South Mojave junction -> Mojave UP yard -> Searles branch interchange -> Monolith -> Summit -> Walong -> Woodford -> Cliff -> Bealville -> Edison -> Bakersfield BNSF yard / Amtrak -> Staging. Levels are joined by a helix to staging on a lower level.



Once I have the BNSF Bakersfield yard design more complete I will post the full plan for feedback/critiquing.

I'm currently finishing room preparation with a suspended ceiling, valanced lighting. I have a full roster of 60 locos all ready to go - I just wish someone (Atlas or Kato) would produce the GP60M and GP60B :)

Thanks again for the assistance.

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Tim

Modelling Tehachapi East Slope in N scale circa 1999

atsf_arizona

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Re: Tehachapi Layout research help wanted
« Reply #3 on: January 26, 2009, 02:03:44 AM »
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Tim:

You might try Joe Gurtman (sp?) over on Trainboard and/or the A-board


kiwi_bnsf,

Joe's name is Joe Gartman, and on Trainboard, he is SP4009.  He's a great guy, if he's got time, I think he'd be happy to help.

Hope this helps.
John Sing
Sarasota, FL
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https://web.archive.org/web/20151002184727/home.comcast.net/~j.sing/
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Modeling the Santa Fe's Peavine Line (Ash Fork -> Phoenix, Arizona) during the 50s and 60s

kiwi_bnsf

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Re: Tehachapi Layout research help wanted
« Reply #4 on: January 26, 2009, 02:04:32 AM »
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I thought I might as well post some more of the logic behind the layout to get people's thoughts...

Vision

An operations focused mountain pass with heavy through freight traffic running on APB/CTC signalled single track with passing sidings. Double track on the upper and lower decks keeps traffic flowing either side of the pass.

The Tehachapi loop is obviously a key part of the layout, but is not the sole focus. The enjoyment of following a train over the length of the layout and the challenge of the gradients is a bug part of the appeal. Helpers added at Bakersfield and Summit, with a helper pocket provided at Woodford siding. However the towns of Mojave and Bakersfield at each end of the layout provide much needed operational interest with yards, industrial switching an interchange, and even Amtrak passenger trains!

Operations will be limited to 2-4 people in the layout room because of space considerations, so a sequence timetable will probably end up working better than a fast clock. I want things to be relaxed and flexible and I also want to be able to operate on my own.

To maximize the available mainline run double-deck benchwork is used down one side of the room. The ascent from the lower level to the upper level is achieved with 2-3% gradients, the Tehachapi loop itself, and a hidden single turn helix. There is a compromise with track passing through the same scene twice while climbing from Bena through Woodford, but this is ameliorated by use of tunnels on the lower level to focus the attention of the viewer on the upper level in constricted sections of benchwork. Also there are several locations on the real Tehachapi pass where you can see the line at more than one level - Caliente and Cliff/Bealville spring to mind.

Appropriate cribwork, retaining walls and culverts will be used as common with the prototype between Bealville and Cable. Tehchapi creek bridges will be accurately modelled on the between Woodford and Walong, and the lower level will cross this on a through truss bridge (of the style seen between Bena and Ilmon).

Design choices

On the lower deck Kern junction is omitted completely from the layout as space in the corner was too limited with tight radius hidden trackage and short stub ended UP yard causing issues. Instead UP trains run on joint trackage passed BNSF Bakersfield yard to staging. The choice to model the BNSF Bakersfield yard is based on my preference for BNSF motive power, and the location of the nearby Amtrak station that allows me to model the push-pull San Joaquin passenger operations. The Amtrak California operations are limited to running from and from staging, these would still add much operational interest by tying up one main track in Bakersfield - forcing bi-diriectional running and interesting dispatching. Also I love the EMD FP59PH locos.

The BNSF Bakersfield yard is not a division point for most through trains - with most BNSF services continuing North to Fresno, Modesto or Oakland. All UP trains bypass the yard. However helpers are serviced here, and I think some manifests originate/terminate/re-block at this yard. The dedicated arrival and departure tracks allow trains to flow freely into and out of the yard without blocking the double track main. The yard is double-ended with long drill tracks at both ends to simplify classification. Five classification tracks have capacity for 75 cars, and a thoroughfare track keeps the switch crews happy. A RIP track and engine service tracks allow for fueling and sanding of motive power (particularly BNSF helpers and local switch engines).

A BNSF local switches the nearby auto rack unloading facilities, oil transloading facility, and the packing houses in Edison. Unfortunately there is not much room for industries, and so there is one crammed in every corner on the lower level. Trackage is designed to make runaround moves simple to keep the main tracks free during switching.

No industries are modeled between Edison and Summit to keep the mountain scenes as realistic as possible.

On the upper deck the town of Tehachapi has been omitted altogether as although it provides scenic interest, it does not provide operational interest. Instead a version of Summit is modeled to allow helpers to be added and removed heavier trains. Unfortunately there is no room to model Summit wye so helper sets will have to be bidirectional or reshuffled as required.

The iconic Portland cement at Monolith is modeled in the large space available in the corner, with structures partly in low relief. A UP local originating in Mojave switches the cement plant from the Summit yard.

The UP Mojave yard is modeled as this balances BNSF operations on the lower deck, and originates locals to switch Portland cement and the Searles/Trona branch. Four tracks provide capacity for 60 cars with spurs for fueling local switch engines and helpers. Anticipated traffic is cement, potash, coal and chemicals.

The Searles branch is squeezed in as a single spur, but provides much operational interest as a "universal industry" providing traffic for the Mojave yard.

Access to staging is an issue with a substantial helix required to provide access to loop staging on a hidden lower deck. Accessibility will be an issue and requires careful benchwork  and light to allow easy maintenance. Automated occupancy detection electronics for start/stop would simplify staging operations. However the tight 18" radius on the helix (3.5% gradient) will be the acid test of N scale running characteristics with train lengths being 26 cars on average (with 3+ locos), with the occasional 35 car train with 5+ locos. Full testing is to be performed soon.

Design Process

The current track plan is the fifth or sixth iteration of plans to make most efficient use of the space. Initial doodling lead to a variety of options, but ultimately the majority of the planning was done in full scale on the floor of the room in cardboard. Photocopies of Peco code 55 N scale switches were used to make sure that ladders and complex track were workable. Curves were drawn using a trammel with easements laid out using a bent lath. Track spacing was checked with temporarily pinned flex track and 89" autoracks.

The final centre lines were marked on the cardboard and then considered over several weeks. The plan evolved rapidly, with trackplans becoming simpler after contemplation. Mojave yard has become a more faithful representation based on research of the prototype. Tehachapi township was dropped in favour of Summit for greater operational interest.

Standards

Visible minimum curve radius is 18" with easements, with most curves being a broader 22-26". Hidden curves have a minimum radius of 15".

Deck heights are 37" and 57" designed for sitting on a backless office rolling chair, and standing.

Aisle widths are typically 30" with a narrow 18" choke point on the way into the room. I consider 30" to be fairly tight, but with only 2-4 operators this should be acceptable. A small 15" aisle accessible via duckunder is provided on the far side of the Tehachapi loop to allow for scenery detailing, maintenance and photography.

The layout has mainline and siding capacity for around seven full 30 car trains while remaining fluid. Staging has capacity for a further seven 30 car trains. Total yard and industry capacity is around 250 cars (obviously this will only ever reach 180 cars in operation).

Control will be Digitrax DCC with walkaround throttles. The Digitrax loconet will be integrated with JMRI running on a dedicated Apple Mac computer running a customised PanelPro CTC system linked to BDL16 occupancy detection units and SE8C signal control units. Signalling will run in two modes - automatic APB based on block occupancy and turnout settings, and full CTC for dispatcher operation.

Each location will have its own local control panel recessed into the facsia with mimics for signal indications and block occupancy. The local control panels will have lock/unlock switches to pass control from CTC to local. Bakersfield Yard will have duplicated control panels - (one at each end) to allow switching at either end without having to walk all the way to the other end - allowing two operators to switch cars and assemble trains.




I'll try to get the current plan scanned in the next week or so - I am not a CAD guy and so will need to condense the 1:1 version down onto a smaller piece of paper!

I'd love to hear people's thoughts....

Cheers

Tim
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Tim

Modelling Tehachapi East Slope in N scale circa 1999

ednadolski

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Re: Tehachapi Layout research help wanted
« Reply #5 on: January 26, 2009, 10:19:30 AM »
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I'm afraid I don't have much on the yards or ops -- I've been focused mostly on the Loop & a few of the other areas on the hill.

Have you contacted anyone from the La Mesa club in San Diego, CA?  They have a huge, 2-story Tehachapi layout that is very accurate, and lots of very knowledgeable folks.

There used to be a Tehachapi group or two on Yahoo, but the list has gone dark.  Is there enough interest here to start up another one?

Ed

ednadolski

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Re: Tehachapi Layout research help wanted
« Reply #6 on: January 26, 2009, 10:45:13 AM »
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the tight 18" radius on the helix (3.5% gradient) will be the acid test of N scale running characteristics with train lengths being 26 cars on average (with 3+ locos), with the occasional 35 car train with 5+ locos. Full testing is to be performed soon.

For 18" curves, I'd recommend not exceeding 2%, and for 3% I'd recommend 22".

The 3.5% sounds too steep.  My trains are 30-35 cars, and it takes 3-4 Kato CC diesels to pull them up the grade (mixed 2% and 3%).  On 3% or more, you may need mid-train or rear-end DPUs, but my experience is that these do not work well in N scale if your cars have truck-mounted couplers.  The DPUs push the truck-mount couplers into compression, so they want to spin & derail. The usual "fixes" (more weight, pizza-cutter flanges) are counterproductive, because the DPUs just have to push harder to get up the hill.  The only real fix is to body-mount the couplers like the prototype, but you have to put enough body-mounted cars in front of the DPUs for it to work. (Cars that run with the couplers always in tension should be OK).

Also, I use DCC to speed-match my locos, and program the DPUs to run a few scale mph slower than the head-end units.  That helps keep the truck-mounted couplers in tension.

Quote
Photocopies of Peco code 55 N scale switches were used to make sure that ladders and complex track were workable.

Track-wise I wouldn't go larger than C55, since MT pizza-cutters are easy to swap with lo-profile wheels.  I've been really happy with the C55 Atlas #7 turnouts on my layout and in my staging yards.  Atlas now has a #10 turnout that looks awesome.

If you're doing modern, Tehachapi was re-laid with concrete ties in 1997.  Micro Engineering makes a C55 concrete tie flextrack with weathered rail and correct tie spacing (unlike their HO scale concrete tie flextrack).

I hand-laid the curved turnout on my Walong stub siding (solder & PC tie construction).


Quote
Visible minimum curve radius is 18" with easements, with most curves being a broader 22-26". Hidden curves have a minimum radius of 15".

Careful of the 15" radius if it is on a grade.  I have a section of 16" radius on 2.08% grade and that is a trouble spot for the longer trains.

I built my Loop a mix of 19" and 21" radii, to fit in the 4x6 space, but if I were doing it again today I would use 24" min. radii and trace the trackplan from the satellite image.

Here is a link to my Loop layout:


« Last Edit: January 26, 2009, 10:46:54 AM by ednadolski »

Hyperion

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Re: Tehachapi Layout research help wanted
« Reply #7 on: January 26, 2009, 01:40:00 PM »
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Quote
However the tight 18" radius on the helix (3.5% gradient) will be the acid test of N scale running characteristics

Why so much gap between levels on the helix?

To get a 3.5% grade with a 18" radius, you'd have to be planning 4" seperation between levels.  That's about what the HO guys shoot for.  You planning on moving some OD loads that are over 50 scale feet tall? :)

2.5" would be sufficient, and 3" is on the high end if you really wanted to allow room for your hand or something.  Split the difference and go with a still pretty tall 2.75" and you cut the grade down to 2.4%
« Last Edit: January 26, 2009, 01:41:55 PM by Hyperion »
-Mark

kiwi_bnsf

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Re: Tehachapi Layout research help wanted
« Reply #8 on: January 26, 2009, 05:46:56 PM »
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Thanks for the great advice!  Finally a forum where you get constructive feedback  :)

Ed - your loop looks great - I would love to achieve something similar. I hope my scenery techniques prove as pleasing. I am limited to a similar space for the loop (5.5' by 5') and I have to compromise to 18" radii on the inner part of Walong siding. However it quick eases out to 22" so hopefully with a bit of superelevation it proves reliable.

Thanks for the advice on using code 55 throughout - I had wondered whether it was worth going to code 83 for hidden tracks and staging. I will be re-wheeling to low profile wheels anyway so I guess if everything is reliable in Bakersfield yard ladders then it should be okay in staging. I'm planning to put re-railers either side of turnouts.

I am going for concrete ties on the main as if I change eras it is more likely to be present day rather than back-dating, and concrete ties are correct for 1998/1999. I think I will compromise to Peco track throughout as MicroEngineering and Atlas can be a pain to source here in New Zealand, and the tie spacing shouldn't be too noticeable by the time the track is ballasted and weathered.

I really appreciate your warnings about curvature, grades and helper/DPU operations. I have to say you have confirmed some of my worst fears, and I think I am going to have to do a lot more operational testing before finalizing the benchwork. I may use an extra turn of 20" helix under the loop to try and keep the grades down to 2% on the ascent from the lower level.

I am really keen to model mid-train and rear helpers with 25-30 car trains so I will have to do some tweaking. Most of my 250+ cars are truck mount so this could spell disaster...   I am happy to put 3-5 Kato/Atlas locos on the front of every train as this is prototypical for Tehachapi, but the coupler compression effect of helpers is concerning. I like your idea of slowing them down ever so slightly - I could use my JMRI with some scripts to set a loco's CVs to helper or lead status.


Thanks Hyperion for the advice on the helix. I've remeasured my doublestacks and you are right. I can get the grade down to 2.5% easily.

Cheers

Tim
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Tim

Modelling Tehachapi East Slope in N scale circa 1999

GaryHinshaw

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Re: Tehachapi Layout research help wanted
« Reply #9 on: January 27, 2009, 03:07:30 AM »
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Quote
Joe's name is Joe Gartman, and on Trainboard, he is SP4009.

Thanks John -- sorry Joe!

Tim, you have clearly given this plan a lot of thought!  I have to say I'm having kind of a hard time following your description so I look forward to seeing a drawing, but it sounds like you're managing to pack a lot of ops into that space.  I definitely agree with the advice to avoid 3.5% grades, and, depending on curvature, strive for less than 2.5%, even if it forces some tough choices.

I am at a very similar stage of development - hanging a ceiling and generally finishing up the basement in preparation for benchwork:

http://therailwire.net/smf/index.php/topic,17421.msg150468.html#msg150468

If you don't mind sharing a thread, I'll describe a bit of my plan as there are several aspects of it that I'm still unsure about, especially from an ops standpoint, that I would welcome feedback on  - and it might give you some more food for thought.  As I noted above, my space is ~25' x 25' with a few stay-out zones and my stylistic preference is for a relatively open plan, mainly single level, with long mainline runs and modest selective compression.  Operations focus on bi-directional, single track mountain railroading with staging at each end.  After studying the line in Google and superposing key elements over my basement floor plan (with LOTS of permutations) I came up with the following mainline run:



The grid is 24"; here is a birds-eye view of tracks floating in space:



There are some extraneous bits in this plan that I haven't edited out yet, but the main idea is as follows: the central turnback yard represents both ends of the UP line: Mojave on the left side and Bakersfield on the right, joined by the turnback ("Mofield").  I haven't settled on the detailed track arrangements here and haven't decided if this should be a sceniced lower level with terminal ops, or just unsceniced staging.  The line leaves Bakersfield southbound at the upper right and emerges to the main level in the far upper right: this is where the line comes out of Ilmon canyon heading into Caliente.  From there, the plan pretty faithfully duplicates the run all the way to Cliff, with the exception of the Allard horseshoe.  The selective compression is roughly a factor of 2 for curves and 3 for straight sections.  The minimum radius is 20" with easements (strictly enforced) and the grade is a steady 2.0% the entire way (a little flatter coming out of Ilmon): this part of the run rises from 42" at Ilmon to 59" at Cliff, and it measures almost exactly 3 scale miles (the corresponding stretch on the prototype is 8 miles - 2.5 miles as the crow flies).  Here is a slightly closer view with very crude topography drawn in:



The Caliente horseshoe is at the bottom right, Tunnel 2 in the middle-far distance, Bealville on the left, and the beginning of Cliff siding on the lower left (coming around under the stairs).  It's quite a reach to the back (right) tracks in this plan, so I have 3 access holes in mind between the front and back tracks.  However, since there is only 1 turnout along that stretch, I'm hoping it won't be frequently needed... I'm planning to mock this up and get some experience with it before committing ("we're just living together").

After rounding the corner at Cliff, the tracks enter a double-track 4-turn helix to drop down about 8" before sneaking over to the other side of the room for the scene from Woodford to Walong.   I will probably reroute this track in front of the stairs instead of *through* the stairs, but this is still TBD.  The Woodford/Walong stretch has the same specs as the lower segment: 20" min.rad. 2% max. grade, with the inner loop of Walong being 21".  I'm a little worried that Ed recommends 24", but since I'm starting the build on the Ilmon-Cliff section, I should get a pretty good idea of how reliable ops will be from the reverse curves in Bealville.  Finally, the line terminates at Tunnel 10, entering an 8-turn double-track helix to get back down to "Mofield".  The details of this helix routing are still being assessed: either around the boiler (unlikely) or just a simple helix to the right of the boiler (better, but takes up more space).  BTW, the shortest siding is 16.5' (half a scale mile) which is about the longest train I could imagine running on these curves & grades anyway.  This would hold, e.g., 4 C-C locos and ~25 auto-racks.

The key thing still missing for me is the BNSF terminal trackage.  There is a lot of room to fit it in under the right side, but I can't quite get my head around how *big* this plan really is and what it will be like to access lower level trackage (even using 3rdPlanit).  So I'm just going to plow ahead with a mock-up of Ilmon to Tunnel 2 to get a better sense of what it would be like to have tracks underneath, and what kind of crowding I might expect in the aisles in such a case.

The thing that gives me hope that I might actually get somewhere with this plan is that it's basically very simple: relatively few turnouts, almost no structures or trees, etc.  For me it's a train watchers dream, with some decent mainline ops possible.

Here's a parting shot of a rack train emerging from Tunnel 1 and snaking down to the Caliente horseshoe:



That blue orb up there is my head, with a big grin.   :D  Sorry to blather on.  Hope this gives you some food for thought, and I'd love to hear your take as well.  Maybe we should start that Tehachapi group up Ed...




James Costello

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Re: Tehachapi Layout research help wanted
« Reply #10 on: January 27, 2009, 06:29:52 AM »
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I am going for concrete ties on the main as if I change eras it is more likely to be present day rather than back-dating, and concrete ties are correct for 1998/1999. I think I will compromise to Peco track throughout as MicroEngineering and Atlas can be a pain to source here in New Zealand, and the tie spacing shouldn't be too noticeable by the time the track is ballasted and weathered.
Tim

Hi Tim - I've enjoyed reading your posts on your thoughts and planning on your layout, as I am trying to accomplish something similar - modeling Tehachapi from distance (Australia in my case). My primary modeling period is the 1990-96 years of the Espee, particularly the I-5 corridor and Tehachapi, in N scale. I don't have the room at the moment for my dream layout, so those tough decisions about what's in-scope and out-of-scope haven't had to be made yet. I also dabble in UP/BNSF in 2006-2008 thanks to some railfanning buddies and the fact that it's pretty easy to turn a SP/ATSF intermodal train in 1996 to a UP/BNSF train in 2006.

Most of my information is SP focused, but I do still have some generic information on Bakersfield etc from the railfan and model-railroading press. If there's an article or something you're looking for, just sing out, I'd be more than happy to pass anything on. The April 1994 Pacific Rail News has a small 2 page spread on Bakersfield that I can scan for you if you'd like.
I did railfan Bakersfield in 2006 and 2008 and I took some photos of the BNSF yard in 2008 - they're aren't much, but I'll post them here when they get a chance.

Do you have this book? It's before your BNSF timeframe, but it's worth it for the photos alone.... I think it does cover helper operations though.
http://www.amazon.com/Tehachapi-Railroading-Mountain-Steve-Schmollinger/dp/1550460633

The concrete ties do pose a future problem for me - do I go with the wood of my primary modeling as they were in 1996, or the concrete of the later years and pretend the Espee upgraded in 96? Decisions, Decisions.

Tim, my LHS is trying to keep a good quantity of ME flex track in stock, as there are a few modelers here in Australia that are using it in our current layouts. It's hard to get full stop, let alone on this side of the Pacific. Anyway, we got a shipment last week and still have quite a few (probably around 10) bundles of non-weathered, concrete tie code 55 flex in stock. Feel free to drop me a email if you'd like some more information - I know they ship to NZ.

Lovin' the mock-ups too Gary!

Ed, any more photos of that layout? Looks great!!!!

 
James Costello
Espee into the 90's

AlkemScaleModels

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Re: Tehachapi Layout research help wanted
« Reply #11 on: January 27, 2009, 09:49:23 AM »
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Quote
Joe's name is Joe Gartman, and on Trainboard, he is SP4009.

Thanks John -- sorry Joe!



Your images are a great way to visualize a layout, especially one with so much 3 dimensional variation.
BCK



ednadolski

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Re: Tehachapi Layout research help wanted
« Reply #12 on: January 27, 2009, 12:25:58 PM »
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I am really keen to model mid-train and rear helpers with 25-30 car trains so I will have to do some tweaking. Most of my 250+ cars are truck mount so this could spell disaster...   I am happy to put 3-5 Kato/Atlas locos on the front of every train as this is prototypical for Tehachapi, but the coupler compression effect of helpers is concerning. I like your idea of slowing them down ever so slightly - I could use my JMRI with some scripts to set a loco's CVs to helper or lead status.

Tim, on Tehachapi I think you can get away with even 6 or more engines on the head end, it's not too hard to find that on the prototype even with today's locos.  Much more than that tho, and stringlining starts to become a concern, more so if the curves are tight & the grades are steep.

On my curves/grades, I'm finding one loco good for about 8-9 cars on average, so with even a 30 car train, 4 head-end locos works OK.  It does help to DCC speed-match, so they aren't slipping/fighting each other up the hill.  The Trainspeed scale speedometer is really handy for matching, and for tuning the DPUs to run a bit slower, tho I find I have to re-tune on occasion since the settings seem to drift over time.

With DPUs I think it becomes a matter of balancing how many cars are running in compression, and where the cars/DPUs are located in the train.  If the DPUs are tail-end, then each DPU loco will push 8-9 cars in front of it, so the body-mount couplers are important on those.  OTOH, if they are mid-train, then each DPU can pull 8-9 cars behind it, and those couplers remain in tension so body mounts aren't critical there.  However in that case it's still a good idea to put a few body-mount cars ahead of the DPUs, if any of them will be in compression (truck mounts can handle some degree of compression).  Best bet is to run a few test trains & see where the slack point wants to be, but the slack point likely will vary as the train moves over varying grades and curvatures.

Going downhill, the MT couplers can be a bit annoying since (being made with springs) they have a tendency to "pogo" or "slinky", esp. at low speeds.   The slower-tuned, tail-end DPUs can help keep them in tension & eliminate the effect.  Unfortunately MTs can pogo whether body or truck mounted, and I think the pizza-cutter wheels can magnify the effect (since they add drag).  The Atlas/Accumate and Kato couplers fortunately don't have springs.

I'm still waiting for the new McHenry couplers to become available from Athearn (http://www.nscalesupply.com/ATH/ATH-McHenry.html).  I'm then planning to build a bunch of body-mount coupler boxes from rectangular brass tubing,  as per the Brian Bussey article in NSR a little while back.
« Last Edit: January 27, 2009, 12:29:35 PM by ednadolski »

bambuko

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Re: Tehachapi Layout research help wanted
« Reply #13 on: January 27, 2009, 12:49:40 PM »
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You could of course model it in Z:
http://www.platelayer.com/mj/tehachapi/index.asp
and just think, how much more prototypical could your radiuses be  ;D

ednadolski

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Re: Tehachapi Layout research help wanted
« Reply #14 on: January 27, 2009, 01:11:49 PM »
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You could of course model it in Z:
http://www.platelayer.com/mj/tehachapi/index.asp

Ah, this was one on my inspirations!  :)

If you don't mind hand-laying a curved turnout for the stub siding, then some of the sharp curvatures can be improved.

But I'll leave the Z-scale to Tom...   ;)