Rocky Mountain Pacific in Fn3

Rocky Mountain Pacific Logo-1

The Rocky Mountain Pacific is Bruce's Fn3 garden layout. Fn3 uses 45 mm (typical garden railroad) gauge track and a 1:20.3 scale ratio to model accurately 3 foot narrow gauge railroads.

The name is registered with the NMRA. It came from the idea of southwestern Colorado narrow-gauge railroads that were always short of cash and long on ideas. Everybody seemed to be planning on running to the coast or Mexico, when really they didn't have enough cash to get over the next hill!

The reporting marks for the Rocky Mountain Pacific are RMP. That can also stand for Real Money Pit.

This is being built in our back yard here in Goodyear AZ. It will use an NCE 10 amp radio DCC system.


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Over the weekend, we (Linda and I) got most of the track leveling and ballasting done. There are a few spurs that still need ballast and a turnout to repair.The large piles of stocks and dirt have been removed or leveled.

Our back yard is starting to look like a railroad, not a dirt pile.

I even started getting some of my Fn3 rolling stock out.

Track work continues

All of the bridges scratch built and exhibited at the NMRA AZ division meet in June have been installed. The track is now connected all around the layout.

On 9/25/15 I graded the yard - the last task in rough track work.

Now comes the ballasting.

Also on 9/25, I ballasted the yard and leveled the entire area. Once the ballast settles, it will be walkable, allowing for train make up and break down.

I’m using the same methods the prototypes did, except somewhat in reverse. 

The ground level was established by the landscapers I hired to build up the area and bring in topsoil.

The track was laid on that base and the track plan verified.

Next, I shim the track to the desired height and grades. Most shimming was done with 1 x 2 garden stakes. Occasionally more or less shimming was needed and smaller sticks and rocks were used. This was shown in a prior post - CLICK HERE to see it.

I used several levels to establish level and grade sections. The level used to establish grade is 48 inches long and has a ¾ inch copper pipe coupling zip tied to the end. This provides 1 inch in 48 worth of rise for a 2% grade.

Once an area was shimmed,  landscape decomposed granite was tamped under the rails. Here I used a tool of my own design - a truck with a bubble level attached. It helped me to maintain grade and to establish the desired right-to-left level.

Once the granite was under the track the area was ballasted. I used what landscapers call ¼ minus rock. This is what comes through a ¼ inch screen. When it gets wet, it sets up almost as if it had concrete mixed with it. However, it can be broken loose if desired.

A single track cement culvert

On June 10, 2015, I finished a scratch built culvert for the final bridge I need to complete the main layout. The mine-to-stamp-mill track needs a replacement. That’ll come later.

Here is a photo of the culvert. I’ll be taking it to the AZ division NMRA meet this weekend to show. Then, it will be installed on the layout.

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After showing it at the Arizona division NMRA meet on June 13, 2015, it is now installed and ballasted on the RMP upstream from the patio. In the photo (below), you can see the old rail - hopefully to be weathered by exposure to the elements in Arizona - holding back boulders and rocks to allow drainage into the wash without loosing fill or ballast.

Fn3 single-track cemet culvert

A double-track angled timber culvert

In the lower right area of the track plan, the two main tracks cross over a ravine. This ravine will carry rainfall runoff from the layout, as well as providing a visually interesting section.

I built this culvert to carry the rainwater under the tracks. The photo below is of the upstream side (away from most viewers). The downstream side does not have the angled wing walls, but short straight ones, as can be seen in the background.

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After showing it at the Arizona division NMRA meet yesterday, it is now installed and ballasted on the RMP near the patio. The photo above shows the upstream side with the 30˚ wing walls. The patio, below, is on the downstream side where the ballast is retained with old rails and boulders.

Fn3 dual-track box timber culvert - 1

A MOW shed for the RMP

My proto-lanced Rocky Mountain  Pacific railroad needs to store MOW supplies (spikes, plates, hardware and tools) along the pike. This shed was built to fulfill that need. The design was based on normal construction techniques with a few modifications to withstand life on a garden railroad.

9 Fn3 Narrow Gauge MOW Shed

A short trestle for the outer loop

I scratch built a short (one-bent) trestle for the main track crossing over the stream bed. The stream runs up and down on the drawing below to the right of the yard.

I will be showing it at the NMRA AZ Division meet on June 13, 2015.

Here is a photo of it taken in the studio, as it won’t be installed on the layout until after the meet.

Fn3 Single Bent Wood Trestle

The design was adapted from drawings in the Model Railroader book Model Railroad Bridges & Trestles (PP124, 125).

I did find one design flaw in the book drawing. The wing walls were positioned so that they would keep the dirt, etc. from holding up the footers at each end of the trestle. I redesigned them to fix that issue.

Starting on leveling and grading

The weather has gotten warmer, but there is still some cool time in the morning to spend an hour or two on the leveling and grading.

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Wiring is done

Got the wiring done on both loops now. Wrote a column about how I did it for the July 2015 issue of Model Railroad Hobbyist.

Here is how I used landscape staples to keep wire buried.

Bus in the garden

The first photo shows the wire as it laid on the ground.

In the second photo the trench is dug, the wire placed and the staple started into the ground - look for the shadow of the staple.

The third photo shows the staple seated.

Int the last photo you can see the end of the brush that was used to sweep the dirt back over the wire.

Track plan

I finally found the software that will allow me to draw my track plan as I want it to be on my Apple Mac computers. I have it on my MacBook Pro, so that I can go out to the yard and measure and input the data directly, instead of running between the office and the back yard as I was doing previously. I also have it on my iMac in the office, so I can use the dual screens and increased resolution to enhance and label things.

The software is know as Railmodeler Pro and is available in the Apple App store.

Here is the first pass of the layout. I have NOT tried to be totally accurate, but to show the relative relationship of the various track elements. Click on the image for a larger view.

RMP Track Plan

The red track is the outer loop (mainline). The green track is the auto-reversing section, both a teardrop loop and a wye. The blue track is the inner loop (town)

As the structures and operations plans evolve, I’ll be posting revised versions of the track plan with more details.

Lots of wiring done

The good weather held - highs only in the 70s and a bit of rain one evening (actually, quite a bit - ½ inch). Thus, I was able to get all of the drops connected to the rails on the entire layout. There are a couple of sub-buses to install in the yard and a few drops left to solder to the bus in the inner loop.

Since I needed to re-lay the track to the depots (freight and passenger), I actually went ahead and graded it and leveled it.

Look for the information on how this wiring was done in my July 2015 column in Model Railroad Hobbyist magazine.

Copyright © Bruce F. Petrarca 2007 - 2015; All Rights Reserved