Scratchbuild Project - Sperry Detector Car in N Scale

[BCR 570]

Introduction

This build thread will document my efforts to build an N Scale model of one of the Sperry Rail Service inspection cars, specifically SRS 129.  These cars were equipped with induction equipment for detecting internal rail defects.  The Sperry Rail Service Corporation operated a fleet of rail detector cars, most of which were converted from various self-propelled railway cars or “doodlebugs”.  The corporation has provided rail testing services to most U.S., Canadian and Mexican railways as well as overseas.

My interest stems from the fact that SRS 129 visited the British Columbia Railway’s Dawson Creek Subdivision in September 1977 (exactly when I am modelling) and again in 1980.  It was also seen on various CP Rail lines including the Esquimalt & Nanaimo Railway on Vancouver Island. 

I am also interested in building a self-propelled car to meet one of the requirements for the NMRA’s Locomotive Builder Certificate as part of their Achievement Program.  The requirements include the scratch-build of a locomotive or self-propelled car.  While commercial parts for some components may be used, the main structure of the car must be scratch built.


History

SRS 129 began as an Electro-Motive Company gas-electric car built in November 1925 for the Lehigh Valley Railroad as their number 29 (builders’ number 1376A133).  The body was constructed by the St. Louis Car Company, and it as powered by a Winton gasoline engine.  Overall length was 59’-4”.  It served the Lehigh valley Railroad until April 1939 when it was retired and sold to the Sperry Rail Corporation.  This unaccredited photograph is the only one of LV 29 that I have been able to find:




Following acquisition by Sperry, it was converted to a rail detector car and renumbered SRS 129.  It was repainted into the Automation Industries Inc. scheme in 1973 at which time it appears to have been converted to diesel propulsion, likely of the Caterpillar variety.  It lost the three conical exhaust stacks above the forward engine compartment and received a large louvered ventilation and access panel on the left side.  This Ken Perry photograph (shared with his permission here) illustrates the left side and roof as they were during its visit to the Esquimalt & Nanaimo Railway in 1976:




Ken also photographed the same car a year later in September 1977 during a layover at Dawson Creek on the British Columbia Railway, this time illustrating the right side:




In 1978 it received 50th anniversary logograms on the sides (the Sperry Rail Corporation was founded in 1928) and in 1979 it received a new solid front pilot in place of the original boiler tube type.  By 1981 it was repainted into the SRS black band scheme, and by 1991 the rear end had been rebuilt with the cab doors and windows now transposed.  It has since received new windows and was still in service as of 2021.  If anyone knows of its present whereabouts and status I would be interested in knowing.


Operation

The detection cars roamed all over North America, operating with a Sperry driver and operator, and a pilot engineer and conductor supplied by the railway.  The cars typically operated as a work extra, progressing at low speeds with the induction equipment on the rear truck deployed onto the rails.  When a defect was detected, the car would stop, and the Sperry operator would detrain to mark the spot on the rail with a can of spray paint.  Some cars had paint reservoirs and automatic sprayers underneath.  He would then return to the car, and it would resume its journey.  Between trips the car would stay in a siding or yard and the crew would be accommodated on board, venturing out for supplies as needed.


Notes

Before getting started I should mention that mine won’t be the first Sperry detector car in N Scale.  My friend Mike Pagano kit-bashed one from the Bachmann doodlebug and his build is documented in the Sep-Oct 2014 issue of NSR starting on page 54.  I had been thinking of a similar build for some time, but my interest in earning the Locomotive Builder Certificate requires a scratch-build.

I have also been studying Randy’s thread on re-powering the Bachmann doodlebug with a Tomytec TM20 drive.  I have sourced and received a Bachmann doodlebug and Tomytec chassis, and I will evaluate both as drive options for this project.

This project requires a fair amount of research to work out dimensions as I have not seen any drawings for this particular car.  I will review my research efforts in the next post.


Tim

[BCR 570]

Research

I have not come across any drawings for this specific car.  All of the detector cars were unique to some degree, having been converted from different cars, and went through numerous modifications during their careers.  The best option seemed to be to go back to the original car and establish dimensions and layout for it, and then determine what was changed during the conversion by Sperry.

My friend Greg Kennelly provided a drawing from Edmund Keilty's book Interurbans Without Wires, which provided the general layout and dimensions for an EMC-St. Louis Car Co. gas-electric car.  These cars were very similar to each other with a standard motor compartment measuring 8'-6 1/2" in length, a baggage compartment which varied in length and could include an RPO section, a standard passenger compartment (usually divided into a smoking section 8'-9" in length and a non-smoking section 23'-4" in length, and a rear vestibule 3'-10 1/2" in length.  The passenger compartment and a portion of the baggage compartment were made up of 35" wide spaces, each containing a window.  This drawing provided a number of hard dimensions, from which others could be calculated:




I was also alerted to drawings of Sperry detector cars in the January 1952 issue of Model Railroader and the June 1956 issue of Railroad Model Craftsman.  While these drawings depicted different cars, they yielded some dimensions and some identification of underbody and roof components.  These drawings are seen here:




Another useful resource in working out the details of the Sperry conversion was a Sperry brochure which I found online.  It contained an illustration and a description of the internal arrangement of the cars.  When matched up with photographs of the car, the alterations to the window arrangement along each side began to make sense:




Another very useful resource was the Walthers HO Scale model of a Sperry car which I was able to borrow from a friend.  I measured all of the door, windows, and other features using an HO Scale ruler and documented those.  In most cases they compared favourably with my other resources.  The HO Scale model is seen here:




Armed with all of this information, and as many photographs of the car as I could find online, I created my own drawings of the original car and the converted car, documenting the dimensions I will use for the build:




The research was an enjoyable first step and I learned a lot about the detector cars.  In the next post I will review the configuration of the car and how I am planning to build it.


Tim

[BCR 570]

Configuration

In researching the construction and configuration of the car prior to modelling, it is helpful to know the internal arrangement before and after the conversion process.  As mentioned above, the original gas-electric car would have had a forward driving and motor compartment with side doors, a baggage compartment with side freight doors, a smoking compartment, a main seating compartment, a heater and toilet, and finally a rear vestibule with side and rear doors.  There would be fuel tanks and battery boxes underneath the car, and exhaust stacks and ventilators on the roof.

A standard layout was adopted for the various rail detector cars during conversion.  The forward driving and motor compartment was retained, and behind this a galley for the crew was installed.  This was followed by a crew lounge, and then a bedroom with bunks either side.  After this there was a shower and toilet across from each other, near the centre of the car.   Next came a rear mechanical room with power for the testing equipment, car lighting, a secondary air system, heating plant, work bench and other equipment.  At the rear end was the recording room in which the actual testing was performed.

This internal arrangement determined the changes to the window arrangement as well as the various exhaust, intake, and ventilation equipment on the roof.  Underneath the car, the original fuel tanks and battery boxes were retained, and additional tanks for air, kerosene, oil, and water were added.  Where cabinets or closets were installed against internal bulkheads, the adjacent windows were blanked out.  Smaller windows were substituted in the galley and bathroom.  A freight door was installed on the right side towards the rear for installation and/or removal of equipment in the rear mechanical room.

As mentioned, the diesel conversion resulted in removal of the original three exhaust stacks, and the installation of a large louvered ventilation and access panel on the left side.  I would imagine that this panel was hinged for installation and/or removal of mechanical components.


Build Plan

I plan to build the underframe, carbody and roof in styrene.  For the mechanism I will use either the Bachmann doodlebug power truck and drive train, or the Tomytec TM20 mechanism.  (The power truck and drive train are exempt from the scratch-built requirements for the Locomotive Builder Certificate.)  I will adapt a Rapido Trains six-wheel truck assembly for the rear truck, which had a 10’-8” wheelbase with the detection equipment between the two wheels.

I will use commercial parts as permitted for the pilot, couplers, lights, bell, horns, running boards and rotary beacons.


Carbody

I will start with construction of the carbody.  To understand the carbody arrangement of the Sperry car, it is helpful to go back to the original gas-electric car.  As mentioned, a study of an EMC drawing yielded many valuable measurements, which were compared against a photograph of the original Lehigh Valley gas-electric car.

The St. Louis Car Company carbodies for the EMC gas-electric cars were somewhat modular in construction with a front cab and motor compartment measuring 8’-6 ½” in length, a baggage room of varying length (which could include an RPO section), a passenger compartment of varying length, and a rear vestibule 46 ½” in length.  The passenger compartment was made up of 2’-11” or 35” spaces each having a window and half a separator on each side.  All of these are hard dimensions from the drawing.  Knowing the length of the motor compartment, passenger compartment and rear vestibule, and the overall length of this car, I can calculate the length of the baggage compartment.

The drawing also yields the overall height and width of the car, and the height of the letterboard, from which I can calculate the height of the lower sides and the window strip.

The next step was to go to the photographs of the Sperry car to determine specifically what changes were made.  A comparison between the EMC drawing and the photograph of the Lehigh Valley car with photographs of the Sperry car indicated which windows were blanked out, which were added and which were retained.

I worked from the rear of the car forward as I knew that the rear door opening and first window at the rear were retained.  On each side of the car near the centre there is a blanked-out window panel with a small horizontal window added.  I surmised that these were likely for the shower and toilet which means they were directly across from each other, and these aided in confirming the correct arrangement of windows.  Where an item spanned more than one window space, such as the door for the rear engine room or the louvered panel on the front left side, I relied on the measurements from the Walthers HO scale model.

I then sat down to create my own drawings of the original car and the Sperry car (shown above) to document the specific arrangement and measurements I will use.  I then made some sketches to note which dimensions of styrene I will use to get as close as possible to the desired dimensions.


Underbody and Roof

I also created my own drawings of the underbody and roof arrangements.  There is a fair amount of equipment mounted underneath and on top of the car.  Underneath we find battery boxes, fuel tanks, oil tanks, air tanks, as well as the underframe structure and usual brake appliances.  Measurements for these were obtained from the Walters HO model.

The roof has a central running board with platforms out to the front right and left rear sides where the grab irons for roof access are located.  At the front of the roof are a single air horn, a bell, a rotary beacon, intake screens for the motor compartment, and various exhaust stacks.  Behind these on the right side is a circular FM loop antenna, possibly for an entertainment system in the crew lounge.  There are two large cylindrical air tanks, one up front and one at the rear.  Along the roof are several large ducts for intake or exhaust of air.  At the rear end are another horn and rotary beacon.

The underframe components were fairly consistent over the years, with the exception of change from gasoline to diesel propulsion and a change in cooking fuel from kerosene to propane in the early 1970s.  The roof top components changed considerably, however, and a careful study of photographs is required to determine the exact layout for a particular decade.  I was fortunate to be able to obtain several good overhead views which helped to confirm the precise arrangement.


Commercial Parts

The NMRA's requirements for a scratchbuilt locomotive (or in this case a self-propelled car) list some specific exemptions including motor, gears, drivers and wheels, couplers, lighting, trucks, paint, decals, bell, marker/classification lights, brake fittings, and basic shapes of wood, plastic, metal, etc.

As mentioned I will use either the Bachmann gas-electric drive (still trying to figure out how to disassemble the model) or the Tomytec TM20 drive, either of which will yield the motor, gears and front truck.  The Sperry cars had a unique rear four-wheel truck with a wheel base of 10'-8" and the sensor equipment mounted beneath the side frames.  This wheel base is almost equivalent to the distance between outer axles on a six-wheel truck.  The closest thing in N Scale appeared to be the six-wheel trucks found under the Rapido Trains NSC baggage car model, and an email to the folks at Rapido resulted in a pair of these trucks coming my way.

I am hoping to use the front pilot, marker/classification lights and bell from the Bachmann model (if I can figure out how to remove them in one piece).  I have been trying to locate a package of the Detail Associates 8005 bells but to no avail.  The front headlight is a Pyle dual vertical headlight with angled number boards such as is seen on EMD switchers.  I believe that Sunrise Enterprises once made this part (N-645) but I have been unable to locate one.  I was alerted to the suitability of the headlight parts on the SW900/1200 switcher offered by Life-Like, and Jim Starbuck kindly sent me a pair which I will use.  The rear headlight is a single circular lens and I have a Sunrise part which might work for that.  I have a nice pair of single air horns from Sunrise, and I will use Dave Mackinnon's (Details N Scale) rotary beacons.

The remaining parts will include Precision Scale co. brake appliances, Micro-Trains couplers, paint and custom decals.  I am hoping to be able to scratchbuild everything else.


Confirming Methods and Dimensions

Prior to commencing the build, I want to try out my intended construction methods and sizes of styrene with a few test pieces.  I will share photos of those in the next post.


Tim

 

[Dwight in Toronto]

Hey Tim … I just wanted to commend you on the comprehensive approach you are taking as you convey the depth and breadth of this project.  Nicely written, with clear, easy-to-follow descriptions.  Following closely, and looking forward to seeing things progress.

[BCR 570]

Thank you Dwight; hoping to share some construction techniques as I go along.

Tim

[BCR 570]

Test Sections

With all of the research complete, the next step was to undertake construction of a few test sections to validate planned construction methods.  (Note:  These were assembled fairly quickly so not my neatest work.)  I built a shorter left side on which I could practise building the front and rear doors, and the various window types.  This test section also served to confirm the various sizes of strip styrene I was planning to use in assembling the sides:




From left to right:  cab door into motor compartment, louvers for motor intake or exhaust, blank panel, full size window with flush frame for recessed glass, small horizontal window for kitchen and bathroom, another flush frame window with horizontal divider, blank panel, four windows with the last one having a recessed frame for flush glass, panel for roof access with holes for grab irons and safety cover, another window with recessed frame (not cut out), and rear cab door into recording room.

The test side section was assembled on a sheet of .010” styrene cut to a height of 7’-6”.  A strip of .020” x .188” was laminated along the lower portion of this to represent the lower car side.  Above this I installed a .030” x .030” strip to represent the belt rail.  A strip of .010” x .125” was laminated across the top of the side to represent the letterboard.  This left the desired gap of 36” for the window strip.

The window separators are strips of .020” x .020” cut to a length of 36”.  Inside the window openings is an inlay of .010” x .010” styrene strips.  On some windows this is inset by .010” for a flush fitting window outside; on other windows this is flush with the side of the car and the window will be inset behind this.  The three small horizontal double windows for the bathroom and galley have frames assembled from .010” x .020” strips which are outset by .010”.




The door openings were cut out and a door skin made from .010” sheet styrene was laminated in behind.  The window openings were cut out of the door skins and the window glass will go in behind.  The motor compartment access panel with the four sets of louvers was assembled from various widths of .020” styrene, and the louvers themselves were cut from .040” thick clapboard siding with .030” spacing.  When all of this was assembled, the rear side was laminated with a strip of .010” x .188” styrene at the bottom and a strip of .010” x .125” styrene at the top to provide a car side which is .040” thick at top and bottom.


I also assembled test pieces for the front and rear ends on sheets of .010” styrene.  The window sizes for the front and rear ends are different and the front end also has the belt rail, which is higher than along the sides.  I had yet to work on a way to replicate the gentle curve of the ends on the prototype, so these were built flat primarily just to confirm sizing of styrene and windows:






I then proceeded to attempt a curved end with some spacer strips behind the window separators.  This was not entirely successful as the result is more of a bend than a gentle curve:




I will have to think of another way to accomplish this effect; perhaps a horizontal piece in behind above and below the windows with the curve filed into it that the end can follow.


I also assembled a short roof section.  It was built on a base of .010” sheet styrene with a central strip of .100” x .156”, a strip either side of .100” x .188”, and a strip of .100” quarter round on each side of the roof.  This was then sanded to conceal the joints between strips.  Another piece of .100” quarter round was attached across one end, and the corners were then filed down to match the side quarter rounds, resulting in the compound curve at each corner of the roof:




I also tried assembling one of the roof ducts using .080” strip and .080” quarter round, with a piece of clapboard siding at the outer end to simulate the louvers:




This roof sample looks good when viewed from the side, but it does yield a roof line which is flatter than on the prototype, which appears to have a gentler curve.  However this may be the closest I can get. 


So, with methods and dimensions mostly confirmed, time to get on with the build!


Tim

[peteski]

I then proceeded to attempt a curved end with some spacer strips behind the window separators.  This was not entirely successful as the result is more of a bend than a gentle curve:

If you sand that bent piece, you should be able to shape it into the smooth curve you were going for.

[BCR 570]

Ah yes; sand out the kink - yes I think that would work.

Thank you,

Tim

[Dwight in Toronto]

Not long ago, there was a topic with a link to some fellow building a highway bus out of styrene. 
I recall seeing him do some impressive curved sections by applying gentle heating (open flame, using a Bic lighter etc).

[Ed Kapuscinski]

This is awesome.

I love the idea of building a few practice runs. That's really smart.

[JMaurer1]

One of these days, 3D scanners will be cheap and accurate enough that you can just scan the HO version and shrink it to N scale. Unfortunately, today is not that day. I keep hoping because I want some N scale Southern Pacific B-50-15 boxcars that Rapido has released in HO, but at $55 a car (!!!), I'm not going to get one until I know that I will be able to shrink it accurately to N scale and succeed in printing it.

[BCR 570]

Carbody Sides

I am often asked about the construction methods I use, so will offer a detailed description as I go along.  I also want to document everything for potential evaluation later.  If it is too much you can simply skip through to the photographs.

And so construction begins!  I am starting with the carbody sides.  This will be assembled on strips of .010" sheet styrene cut to a height of 7'-6". it is important to have these strips the same width along their length for a nice square build, so considerable care is taken with this first step.

I used the NWSL Dupli-Cutter and placed a strip of #188 .125" x .188" styrene along the backstop.  This was to prevent the .010" sheet styrene from slipping underneath the backstop as it was pushed up against it.  I then placed three more strips of the same styrene on top of the sheet styrene, which added up to a scale 7'-6" in width.  I pushed the cutting guide up against the styrene strips and locked it down:




I removed the three closest strips and double-checked the 7'-6" measurement along the width of the sheet to be sure of my alignment before cutting:




I made my cuts with a new #11 blade and made light, repeated passes to avoid distressing the styrene.  I cut several strips to have some spares:




After the strips were cut, I checked them along their length with a micrometer and marked the resulting width at each end:




I chose the two best cuts which were within .001" of each other at each end.  Each of these is long enough to yield a complete side and a complete end:




I used my NWSL Chopper to cut one end square.  I clamp a steel rule along the guide to assist in keeping the part square to the blade:




The resulting end cut is checked with a machinist's square:




A lengthy sanding stick is used to dress the two sides of the strips:




Another check to make sure that the ends are still square, and the cut ends are marked for starting the build there:




The two strips are now ready to starting building the sides on, starting from the right hand ends:




The two strips are as even in width along their length and as square at their right ends as I can get them.  This is important as I will be using these edges to help ensure that as parts are added, they are all square to each other for a neat appearance as the build progresses. 

In the next instalment I will start adding pieces along each side, starting at the front end of the carbody and working may back towards the rear.


Tim

[Ed Kapuscinski]

I appreciate your sharing of the process because it really IS instructive.

The idea of using a Duplicutter in that way is something I'm going to keep in my bag of tricks now.

Go Tim! Go Tim! Go!

[BCR 570]

Ok I'm going!

Carbody Sides (cont.)

I am starting at the front end of the carbody and working my way back along both sides, taking care that when I get to the sections with windows, they are directly across from each other.  The two side sheets were labelled left and right, and the squared ends were labelled as to where I am starting.  I will use #247 .040" quarter round styrene for the front corner posts, so those were cut long (to be trimmed after installation).  I wont attach these for a while yet until the sides are built out to a matching thickness of .040":




The first section to be modelled is the motor compartment which houses the driving cab and the motor components.  The first item on the left side is the cab door which measures 24" wide x 6'-0" high and has a window 18" wide x 27" high.  The doorway will be framed with a piece of #122 .020" x .040" styrene below the door and a piece of #123 .020" x .060" styrene above the door.  These two strips are cut long and trimmed square at one end using the NWSL Chopper.  The parts are aligned along a steel rule to ensure a square cut:




A piece of #122 .020" x .040" is cut long, inset in from the end 24 scale inches and glued in place perpendicular to the side sheet.  This is the piece immediately to the right of the door.  Why do I leave the piece long?  Rather than try to cut a piece to size and then try to align it top and bottom to match the side sheet, it is easier to glue it in place and then trim it to length once in place.  Here it is after gluing:




Now I trim the part to length, using the edge of the side sheet to align the #17 blade.  Two chops and it is now the correct length matching the height of the side sheet:




I used the same technique for the pieces going in above and below the door.  They were left long and the ends cut square were butted up against the door post.  A square is used to align the parts, and a .010" thick strip of styrene is used underneath as a shim to keep the parts level during installation:




The carbody side is placed upside down on the Chopper and the two pieces are cut flush with the end of the side sheet:




The end is dressed with some fine sandpaper using the NWSL True Sander.  (The Chopper, Dupli-Cutter and True Sander are great tools for this work.)  Again, a steel rule helps to ensure a square end:




This is the resulting door frame.  The side sheet inside the door frame will be cut away and the door will go in behind, but not yet.  It will be left in place for now to protect the two pieces above and below the door.  How do I know how why to do this?  I cut this section out on my test part and noticed during subsequent work that those pieces were getting tweaked out of alignment during handling.  Another benefit of undertaking a few test pieces prior to a major build:




The cab doors will be cut from strips of ##108 .010" x .188" styrene which is about six scale inches wider than the door opening.  Again, the part is left long for ease of positioning and will be trimmed after installation.  The window opening was started with a few drill holes and then opened up with small files.  The window with rounded corners is difficult to get square and with symmetrical corners so I will make several of these doors and select the best ones.  This one is my first attempt:




Here is the completed door frame and first attempt at the door:




After the cab door comes a large panel with four sets of louvers, so I will tackle that next.   The nice thing about this type of work is that as I head into a very busy period at work, I can get a little bit done most evenings, one small step at a time.


Tim

[BCR 570]

Carbody Sides (cont.)

After the cab door on the left side comes a large panel measuring 4'-3" in width which appears to be hinged at its trailing edge, likely for access to the motor compartment when components have to be serviced or swapped in/out.  The panel has four sets of louvers for ventilation which stand proud of the panel side.  I need to install the four sets of louvers with material on either side, in between and above and below.

First up is a piece of #120 .020" x .020" which goes in adjacent to the door post for the cab door.  Squares are used to ensure an alignment perfectly perpendicular to the carbody side:




The louvers measure 18" wide x 24" high and I need four of them.  I cut them from #4031 clapboard siding which does a decent job of replicating louvers.  This material is .040" thick so it will stand proud of the carbody side about .020" which is about right.  I cut a long strip of this material 18 scale inches wide:




I then cut this strip into 24 scale inch high pieces, which works out to five louvers.  The louvers were used to align the #17 blade for a square chop:




There are several strips of .020" x .030", .020" x .040", .020" x .060" and .020" x .080" which extend across the width of both pairs of louvers plus the separator in between.  These all need to be cut to the correct and same length.  I began by lining them up along a ruler and cutting one end square:




I then turned them around and butted them up against a steel square, and used the louvers and their separator to get the correct distance between the square and the cutting blade:




The pieces above were installed, again using a square for alignment.  We are looking at the work upside down here:




The first pair of louvers went in, followed by the horizontal and vertical separator:




They were followed by the second pair of louvers and their horizontal separator:




The pieces across the bottom were installed next, and finally the vertical piece to the right of the louvers (again we are upside down here):




This is the finished panel, which turned out fairly well.  It will get hinges at some point:




I will get to the right side of the motor compartment next.


Tim