Aristo FA1/FB1 Lowered & Body Mount Kadee 907s Aristo FA1/FB1 Lowered & Body Mount Kadee 907sTed DoskarisJune 23, 2017Rev GE-A August 19, 2017Rev GE-B; Updated drawings, Added REA brand info., Added ladder info. Contents: OverviewLowering MethodsFactory FA1 / FB1 VersionsHeight vs. PrototypeDisassembly of unitChassis modificationsCar body shell modificationsSpacer blocks fabricated for Kadee couplerLadders & new mounting platesRemedying factory flawsReassembly of unitAdding extra weightOperational ConcernsAppendix A, Car Body Exploded Views Overview The American Locomotive Company (ALCO) FA1 freight diesel was stated to be Aristo-Craft's first model loco, being produced by its antecedent company, REA. It is a "G", 1/29, scale model. Aristo-Craft (and successor company, Polk's GeneratioNeXT) are no longer in business; however, so many Aristo FA1 cab units and FB1 booster units were produced in numerous road names that gives rise even at this belated time to making them more realistic and fitting them with Kadee couplers. In this regard, I have 10 such units, most in Union Pacific, but also Rock Island and Napa Valley Wine Train. Accordingly, this article will describe a method to lower the FA1 / FB1 whilst fitting them with body mounted Kadee 907 centerset couplers. The 907 is the newer more realistic "E" type coupler that supercedes the Kadee 789, though it could be installed in place of the newer 907. As with so many locos and cars produced in "G" scale, all but the last production run of the FA1s are too high from the railhead when compared to the real world prototypes. (As far as I can determine, the FB1 was not factory produced in a lowered version.) Since lowering these locos lends itself to body mounting Kadees, that's what I chose to do. Illustrated below is an example Napa Valley Wine Train (hence referred to NVWT) FA1 before and after comparison. The NVWT FA1s are my newest factory version being they have ball bearing trucks, though unlike the last factory version, sill high off the railhead. Illustrated below is an example Union Pacific FA1, FB1, FB1 three unit set that have been lowered. Note that coupler mounting location on the loco is chosen for train operation down to a worst case 8 foot track diameter without incurring binding of the locos or connected cars. Lowering Methods There are many possible methods to lower the FA1/FB1 locos that include the following examples: Method 1 Example:(1) Modify the loco's chassis where the trucks mount. This is described on George Schreyer's Web site, but as described, the lowered amount is limited to about 0.2 inch. Method 2 Example:(2) Modify the car body shell (that involves other details) so the chassis can be recessed or "telescoped" within the shell. Jerry Barnes, an accomplished modeler and craftsman, appears to have used this method that seems to have been done when whimsically adapting an Aristo E8 nose to an FA1. The lowering Jerry did was briefly referred to in the June 2010 issue of Garden Railways Magazine. However, having examined Jerry's Web site, the June 2010 issue of GR magazine and other resources, I could not find any detailed description as how this method was done other than to "cut some off the posts inside the body that the frame attaches to". Method 3 Example:(3) Replace the factory chassis with a custom made one. This could be a lot of work to accurately cut holes and slots to mount the trucks' A frames and to adapt the ladders. That said, this could be a viable method if you have the skill for designing one in concert with software and a 3-D printer, particularly if needing many reproductions. Method 4 Example:(4) The simplest method is to obtain (if possible) the Aristo FA/FB Lowering Kit, Aristo P/N ART-29711; however, it appears this offering is a derivative from the late factory lowered FA1 but may never have actually been produced. The kit primarily includes a new replacement chassis that has pocketed areas where the trucks' A frames mount. That said, the principle component of the kit would be the chassis itself, and this is shown in manuals for FA1 and FB1. The Illustration below is helpful to identify the versions of chassis. Chosen Method:I opted to lower the FA1 & FB1 using method 2 (telescope chassis within car body) because it affords a greater amount of lowering - in my chosen case being 5/16 inch (0.3125") whilst body mount Kadee 907s. To do so can be broken down into several tasks, each of which will be described and illustrated. Tasks to custom Lower FA1 & FB1 Locos & body mount Kadee 907 couplers are as follows: Chassis modifications and: FA1 Pilot modifications FB1 Chassis Extension Modifications End bulkhead panel modifications & Switch Board trimming Car body (shell) modifications Making spacer blocks for Kadee coupler and: Mounting coupler on FA1 Pilot Mounting coupler on chassis Making mounting plates for Ladders and: Attaching ladders on plates & mounting ladder/plate assemblies on chassis Factory FA1 / FB1 Versions There are several evolutionary versions of the FA1 / FB1 loco. The first produced ones were branded in Aristo-Craft's antecedent company name, REA. These were initially packaged in gray boxes and made in Korea, then packaged in black boxes, then made in China, and eventually packaged in yellow boxes. As far as hardware is concerned, motor blocks had their axle tips extending into the side frame bushings that afforded electrical pickup along with the motor block being fully sprung, whereas, later versions characteristic of no axle tips and screwed on wheels have rigidly attached motor blocks with axles having ball bearings and internal electrical pickups. Moreover, the orientation of the motor blocks themselves appeared to vary at different times of manufacture. The brass hand rail size was changed to a larger diameter from what the earliest production units had. Smoke units were also upgraded for only the FA1 in its late production that included burnout protection should smoke fluid be used up - though it was still advised to set smoke power off when not in use. Then the last production run of the FA1 was factory lowered to the railhead for a more prototype appearance, apparently owing to the "G" scale hobby transitioning away from its toy era roots. The following illustrations show most of these evolutionary changes: The following illustration shows the early version compared to late production run, factory lower to rail head, FA1 version: Finally, illustrated below, is a comparison of the factory lowered version vs. the custom 5/16 inch lowered version described in this article. Comment: Interestingly, it has been written that Union Pacific having regeared the ALCO passenger PA locos for freight service in their final years of use paired them with ALCO FA1 / FB1s. However, to date I found nothing that indicated the FA1 / FB1s locos were paired with EMD E type passenger locos or EMD F type locos. Note reference material listed below: (1) Book: "The Union Pacific Diesel", Volume One: Dieselization - 1959, by Dr. Cinthia Priest, Published by Pair Rail Railroad Publications, Ltd. Page 75, top paragraph includes statement: "....the then president of the company, Arthur E. Stoddard, to make the decision to convert these passenger [PA] locomotives into freight haulers as other railroads had already done. The PA's gearing was changed from 64:23 to 77:18. These units could then be paired up with FAs and FBs. The units did, however, serve as passenger units on occasion after this conversion and retained their steam generators..." (2) Magazine: Diesel Era, January / February 2005, Volume 16, Number 1,Withers PublishingPage 15 text includes the statement: "Rarely mated to EMD cab and road-switcher unit's, the FA/FBs were seen mated to their passenger-service cousins, the PA/PBs, which had been regeared for freight service in their final years of operation." Aristo FA1 / FB1 Dimensions Length vs. Prototype Illustrated below is the measured value of an Aristo FA1 Illustrated below is the measured value of an Aristo FB1 Width vs. Prototype Illustrated below is the measured value of an Aristo FA1. The FB1 is the same. Height vs. Prototype The prototype dimensional drawing I was able to locate is for the closely related, later version ALCO FA2. The FA2 was essentially a lengthened FA1 to accommodate an optional steam generator for passenger use; otherwise, it should be good for judging the FA1 as to height from the railhead. That said, the drawing on page 130 in Missouri Pacific Lines book by Patrick C. Dorin, ISBN 1-883089-54-9, of the FA1 that confirms the height of the FA1 is the same as the FA2. Illustrated below is the measured height from the railhead of the Aristo FA1. To lower the loco that much (0.425 inch) would result in the truck side frame brake cylinders being recessed under the car body, which would not look good. Given that, I decided to compromise and lower the loco 5/16 inch (0.3125") determined by judging how it would appear when placed adjacent / coupled to other fairly realistic contemporary locos and passenger cars. Illustrated below is the comparative height of the factory FA1 vs. the custom 5/16 inch lowered FA1 Illustrated below is the how the factory height FA1 relates to an Aristo-Craft E8 passenger loco. Illustrated below is the how the custom lowered 5/ 16 inch height FA1 relates to the same Aristo-Craft E8 passenger loco. The Illustrations below depict how the factory and custom lowered FA1 relates to an Aristo-Craft heavyweight passenger car. The following illustrations show more detail: As shown above, it's very realistic to have the FA1 just slightly taller than a heavyweight passenger car - albeit FA1s were not used in prototype passenger service, whereas, longer length evolutionary models FPA2 & FPA4 / Canadian Montreal Locomotive Works (MLW) locos were. Disassembly of unit Illustrated below is an example FA1 with the chassis removed. First, it's behooving to know the locations within the car body (shell) where all the fastening points are located for the chassis (floor). This is illustrated below for both FA1 cab unit & FB1 booster unit.Note the differences between the two locos, particularly at their front areas depicted in the upper half. Note that the chassis itself is held by 8 screws for both FA1 & FB1, albeit with some locational differences (4 each side for FA1 sans pilot & 4 each side with FB1 floor extension attached). The FA1 has its pilot held at the nose by two additional screws. See Appendix A for exploded view of individual FA1 and FB1. Illustrated below is the interior view of FA1 chassis with its attaching locations that correspond to those in the FA1 shell. (Note that the Prime Mover and Ladders had been removed for clarity.) Whist the FA1 has a pilot at the front of its chassis, the FB1 has a vestigial extension. That way the same chassis is factory used for both units. Illustrated below is the interior view of FB1 chassis with its attaching locations that correspond to those in the FB1 shell. Before removing the chassis, some preparation must be done as described in the illustration below. Note: When removing the chassis, the slide out end panels (bulkheads) may suffer broken alignment finger tabs that protrude into the end of the chassis. This is of no concern since the panel is to be modified - doing away with those little tabs in that process. The FA1 chassis removal process is described in the illustration below. Note it's preferable to remove the pilot first by removing its nose and tail screws; then the floor can be manipulated easer by reaching in the vacated area. Also, the floor can be manipulated by carefully inserting and sliding a small flat blade screw driver along the periphery between chassis and shell. The FB1 chassis removal process is described in the illustration below. Note the chassis extension cannot be removed first because the factory coupler arm is fastened to both extension and main chassis from within. Also, the end corners tend to be tight. The entire chassis can be manipulated by carefully inserting and sliding a small flat blade screw driver along the periphery between it and shell. Units newer than the very early production ones have a switch board with small connector as shown in the illustration above. However, very early production units do not have that connector but rely on the switch board fingers to make connections as shown in the illustration below. Once the chassis is removed its factory coupler assembly (arm and coupler) is to be removed.Note that trucks and fuel tanks do not need to be removed from the units. There are two different type ladders as shown below on example factory A & B units. The ladders are to be removed - an example method as illustrated. All is now ready for the modifications to follow. Chassis modifications Chassis Rails Modifications unique to FA1: The "rails" near the upper front of chassis to be used for the FA1 need to be notched to clear protrusions at the bottom of the cab within the car body interior. This operation is not needed for the FB1 since it has no cab. Dimensions are included in the following illustration. Caution: The rails terminate just short of the end of the chassis, so be sure measurements are made from the end of the rails, not from the end of the chassis. Pilot Modifications unique to FA1: The finished areas can be painted to match color of the rest of the pilot, particularly at the front notch that accommodates the Kadee 907 type coupler. FA1 & FB1 Chassis End Modifications: FB1 Chassis Extension Modifications: The spacer block for mounting the Kadee 906 coupler will be described later. FA1 & FB1 Bulkhead (End Panel) Modifications: Note:Shown below is an example FB1 having a bulkhead at both ends before they are modified. The FA1, of course, has only one bulkhead that includes a switch board at the end of that loco. What's noteworthy is that FB1 front bulkhead (without switch board) in this example loco was labeled differently where switches would have been if they were there! To speculate, it could be the front bulkhead was a design / factory error and Aristo used what quantities were made be dedicated at the front of the FB1 locos. That said, after the bulkheads are modified, be sure not to mix up the two bulkheads when it's time to reattached the switch board and slide the bulkhead back into the car body shell. The modifications for bulkheads to be used on both FA1 & FB1 are depicted bellow, including dimensions. The completed bulkhead's "T" leg at the bottom serves to both mate with the modified chassis and to align it during installation into the shell - taking the functional place of the two little tabs formerly used. Switch Board Modification: The factory Printed Wiring Board (PWB) with the 3 slide switches needs to be trimmed at the bottom. It appears the PWB is made in multiples from a long wafer strip that are "broken off" at the perforations to obtain individual PWBs. Its bottom should be filed down until smooth so the perforations no longer appear. This needs to be done to obtain needed clearance when attached on the bulkhead and the bulkhead is seated on the chassis. Car body shell modifications Overview: A razor knife is used for scribing marks where cuts are to be made on the posts within the car body shell. Painter's tape placed at the marks serves to enhance visibility. A Dremel tool with cutoff wheel is used to make the cut on both post and its webbing ever so close to the marks, and then a file is used to "square up" & finish to the proper depth. Caution: Be careful to hold the Dremel "square" with respect to the work, and don't plunge it down so deep that it penetrates through the wall of the shell.Posts have holes for the chassis attaching screws. Hole depth must be maintained at 0.3 inch after cutting down the posts. Some example units already had factory drilled holes fairly deep at about 0.6 inch; however, others did not. Therefore, before cutting down the posts, check the depth, and if needed, pre drill the holes deeper to about 0.6 inch so that when the posts are cut down the holes will be OK at about 0.3 inch deep. The FA1 shell has a total of 12 posts aft of the cab that must be cut down along with their webbing that offsets them from the walls of the shell. The FB1 shell has a total of 8 posts along with their webbing that must be cut down. Techniques are the same for both FA1 and FB1 units. Procedural Steps for Modifying Car Body Shell: The shell is modified by cutting down the interior posts and webbing that surround the sides and ends of the loco (except do not cut the FA1 nose front 2 posts used for pilot) The following are sequence of steps - to be illustrated subsequently: (1) Check that threaded holes within posts are 0.6 inch deep. If not, drill them to 0.6 inch deep. I noticed some locos or some posts within a given loco already had been factory drilled to that depth, but others have not. (It's best to drill them before posts are cut down since the existing holes serve as guides.) (2) Mark posts with a cut line located 5/16 inch (0.3215") down from their factory surface. Once marked, painter's edging tape can be used to aid visibility. (3) Cut posts & webbing using a Dremel with cut-off wheel held square with the car body. Engage the cutting wheel just shay of the cut line. The post's webbing that attaches to the side of the shell can be nipped off from there with a small pair of cutters. Flashing that results from heat caused during Dremel cutting can be removed with a razor knife. (4) Make a measurement at the post. In preparation for the finish cut, measure with dial caliper from the edge of the car body shell down to where the post & webbing are cut off. The value should be within 0.580 to 0.600 inch. (target value is 0.590 inch). (Note: In the event too much material had been removed, you can CA glue a thin shim of appropriate thickness to bring back into spec., then drill the small hole in the shim when glue dried.) (5) Perform the finish cut. Depending on how much or little needs to be trimmed to attain the value, carefully use the Dremel and /or use a file to complete the finish. (6) Using a file, finish the surface of the shell smooth where the webbing had been removed. (7) Pre-thread those post holes with screw used for fastening the chassis to a depth of about 0.2". (Caution: Attempting to go too deep may cause damage with initial tell-tail bulging of the post.) This operation is done to make it easier when the chassis is installed so you won't have too much struggle trying to get the screws started. Before threading, the hole entry surround should be chamfered so chassis mounting screw will engage OK. Remove screw when done. (8) The end of the FA1 and both ends of the FB1 must have their post webbing notched to clear the chassis "rails". The dimensions are included at the end in the illustration that follows. Cuts on webbing can be made with a razor saw using short successive strokes, and then a small pair of pliers can be used to rock back and forth the material to break it off. Finish notch surrounds with a file as needed. (Caution: Support column with post from flexing when making cuts since post is at risk of breaking.) Ultimately, the posts & webbing should ideally measure 0.590 inch (target value) down from the edge of the loco shell. Spacer blocks fabricated for Kadee coupler The required spacer blocks are fairly thick so I chose to make monolithic ones rather than stacking discrete pieces of material. Material Used: Plastic material used obtained from Tap Plastics is"King StarBoard® HDPE Marine Building Material", in choice of black: For the FA1 spacer block, a 1 inch wide by 3/4 inch thick long strip, maybe 3 to 4 feet long, can be cut by TAP plastics at reasonable cost. Likewise, For the FA1 rear and FB1 spacer blocks, a 1 inch wide by 1 inch thick long strip, maybe 3 to 4 feet long, can be cut by TAP plastics at reasonable cost. The material can be ripped and cross cut in a table saw using a carbide tip saw blade. The required length blocks can then be cut off on the table saw. A stationary disk sander can be used to surface finish the work piece. I found this works well with HDPE type plastic material. When cutting with the table saw, there is a tendency for tell-tail shreds at the corners of the work piece that can be removed with a razor knife. FA1 Pilot Block: The FA1 spacer block for mounting the Kadee 907 on the pilot is dimensioned as illustrated below. Note: For attaining the lager 3/8 inch diameter hole, start with using a small size drill bit, progressively going to larger bits. Work must be held in a vise whilst using a drill press FA1 Rear Block & FB1 Front & Rear Blocks: The FA1 rear and FB1 both ends spacer block for mounting the Kadee 907 is dimensioned as illustrated below. The spacer block is fastened to the modified chassis as illustrated below. The FB1 uses two blocks, one at each end. Note the front of the FB1 at the chassis extension has a bulkhead panel with no switch board. Ladders & new mounting plates With the loco lowered, the ladders cannot be attached to the chassis as they were by the factory.First, a description of the ladders as they are from the factory is in order. Aristo FA1 & FB1 factory Ladders: Illustrated below are where the factory positioned these ladders. The ladders are attached to the chassis by clipping into slots in the chassis. Aristo ladder measurements are shown for reference. Interestingly, the ladders USA trains has on their ALCO PA / PB passenger locos have a similar appearance and measurement to the Aristo ones, except they have a more conventional way they are attached to the USAT chassis. Since they have a right angle base, it's possible to adapt these ladders to the Aristo FA1 & FB1 chassis. I did not try to do this, but they appear to be a good alternative to Aristo's ladders.For reference, illustrated below are the measurements of the USAT PA / PB ladders in case someone wishes to use these. When the chassis is re installed in the car body shell, the Aristo ladders must be mounted differently than they were by the factory. Also, some ladders are to modified and new mounting plates are needed for all ladders. The following Illustrations show how the ladders are to be modified and where they are to be repositioned on the loco. Repositioning of the offset type ladders from where they were by the factory avoids modifying them. This is best done after the chassis is installed in the car body shell - to be described later. The offset type ladder with new mounting plate dimensions is illustrated below: The other ladders having no offset with new mounting plate dimensions are illustrated below. These ladders will be glued to their mounting plates after the plates are installed (press fit) in the chassis. It is recommended that the ladders be first glued to their mounting plates and augmented with additional fastening screw then press fit in the chassis. Illustrated below are how the ladders having no offset could be glued to their mounting plates after the plates are press fit in the chassis. Press fitting ladders with pre glued plates would be done with maybe wood buffer and plastic mallet. This should be done after the chassis is installed in the car body shell that is later described in the section, Reassembly of unit. If needing to extract a pressed in ladder with mounting plate, it can be done using a small offset screwdriver having similar dimensions to that shown below. Caution: With ladders just glued in place, do not handle the loco by squeezing at the side of the ladder area. Whilst the type of CA glue used is robust, reason should prevail. This is akin to handling one of the Aristo or USAT GP / SD type locos having delicate side & end railings where care should be done. That said, the FA1 / FB1 ladders should preferably include mechanical fastening to their mounting plates using correctly located # 2 flathead screws and nuts as previously illustrated. Alternatively, mechanically fitting & adapting USAT PA / PB loco ladders to the Aristo FA1 / FB1 chassis in place of the Aristo ladders is a possibility. Optional Ladder Retaining Clip A metal retaining clip can be made to secure the ladders to the chassis, though not really needed. I only did this on one unit to see how it could be done.In the example illustration below, the center offset ladders are held down with clips by the fuel tank.Ladders at other locations could be held in place by threading a screw through the clip's base into the chassis. The clips being 3/4 inch wide in the above illustration had to be notched near the base so they would fit between the chassis tabs - otherwise the sides of the fuel tank would be distorted (forced inward) due to lack of clearance. A simpler clip can be made with dimensions shown below. Remedying factory flaws Things to check and remedy are best done before reassembling the loco to avoid having to take it apart and putting it back together twice. Items discovered include the following: Wires Crushed, Pinched, or Cut During Factory Assembly: This resulted from routing the wires along side the Prime Mover that connect to the bulkhead end panel switch board. Consequently, the wires are prone to get stuck between a post and webbing of the shell when installing the chassis. I have seen this problem on all my old version locos that suggests this had been a consistent factory practice. Open circuit / intermittent Truck power pickups: This is of concern for track power users of old version units having fully sprung motor blocks. The factory wire in an eyelet located on the "A" frame may have no or intermittent electrical continuity due to poor crimping exacerbated by oxidation. These connections are suppose to make contact with the sideframe's buss bar - illustrated below. Reassembly of unit Pretest Operation of Loco: Finding problems and fixing them at this point will prevent having to needlessly dismantling the loco once it's assembled. The switch board should have motor on and lights on. Set the smoke switch to center off since it can't be tested without the shell attached. Verify the loco can travel on a test track without disruption in both directions and its lights adjacent to the Prime Mover illuminate - if you care about those lights. Ensure Smoke Tube Connected: The smoke tube supplies air from the fan housing to the smoke element near the center of the loco may become dislodged from at least one end when working on the loco. Installation of the chassis is the reverse of its removal except for allowing it to be recessed for lowering the loco. The same screws are used, and their fastening locations are un changed. When installing the chassis, care should be taken to route the wires going to the bulkhead switch board so they don't get pinched at the sides of the shell. Likewise, for the wires that emanate from the motor blocks. Accordingly, the FA1 end bulkhead with switch board is first to be slid into the end of the shell. The FA1 pilot is installed after the chassis is recessed into and fastened to the shell. Details concerning the pilot are illustrated below. Illustrated below is the FB1 unit chassis with end panel bulkheads temporarily positioned at ether end. These bulkheads are to be slid into their respective rear and front ends of the shell. Installation of the chassis is the same as described for FA1, except rather than a pilot the B unit has a chassis extension, so the whole chassis with extension is treated a single entity during installation. Install "Mud Flaps" & Reseat Handrails: Install ladders with mounting plates: This was described and illustrated in the previous section, Ladders & new mounting plates. Coupler Leveling: Final tweaking of couplers to level them can now be done with everything assembled on the loco. This is not always necessary, but depending on tolerances I found some locos needed it. This is to be done in concert with the Kadee 980 gauge. Adding extra weight Factory Weight Measurements: For reference, the illustrations that follow depict measured weight of locos before any modifications are made. The Aristo FA1 & FB1 locos as they come from the factory are fairly light weight. The newer version is slightly heavier, maybe because of its different motor blocks. Added Weight: I chose to add a small amount of extra weight to these locos using pre cut steel "washers" obtained from Home Depot. I placed the weights in the fuel tank for best low center of gravity (If loco tends to lean, it's more likely to self center). Interestingly, the fuel tank may have holes in one side, maybe to accommodate a switch and charging jack for a battery equipped loco. The steel "washers" used as weights are illustrated below. A trade-off is it takes the place of where the factory intended to have an optional speaker located if fitting a sound unit. That said, I think if adding a speaker for sound to this loco, it's better to eliminate the Prime Mover (that's difficult to see anyway) and put the sound unit and speaker in its place being higher up within the car body. That said, if it's desired to keep a speaker in the fuel tank, an alternative is to add the extra weight within the Prime Mover as illustrated below. Or, if you want to add even more weight than just using the fuel tank it can be put within the Prime Mover, too. Measured Weight of Locos having Added Weight to Fuel Tank Only: Illustrated below are measured weights of the custom lowered, Kadee 907 equipped, old version FA1 and FB1. Illustrated below is the measured weight of the custom lowered, Kadee 907 equipped, newer version FA1. Operational Concerns FA1 Pilot Proximity to Railhead: When Aristo-Craft introduced their last version FA1 that was factory lowered to the railhead, some folks reported that the front pilot lip would come in contact some of the layout track - likely critical with not so good or not maintained track work. Aristo spoke person, Ron Wenger, wrote and article in the July - August 2007 "Insider" that addressed this to slightly raise the loco up by placing a nut that acts like a shim where the motor block ears mount to pedestals within the "A" Fame . Though a simple and effective solution, this would result in the center of the wheels not being centered with the side fame "hot boxes", and may be visually objectionable to a discriminating person. Also, this solution is applicable to last version FA1 with ball bearing motor blocks. I think trimming off more or less of the lip at the bottom of the pilot would be a good alternative. That said, I did not find operational problems on my layout with the custom lowered FA1's pilot. The worst case proximity of the pilot to the track on my layout is illustrated below. Minimum Track Diameter Operation: Chosen proximity of Kadee coupler mount location on the FA1 / FB1 loco is optimized for 8 foot diameter or greater track. If using "S" bends, a straight track section about the length of the longest car or loco should be placed between directional transitions. The following illustration shows the Union Pacific units coupled together, including on 8 foot diameter track circle: The following illustration shows the units' coupled relationships, including distance measurements: The following illustration shows a Union Pacific 5 unit set coupled together: The following illustration shows a Rock Island 3 unit set coupled together: Layout Video: Union Pacific 5 unit set lowered 5/16 inch and fitted with Kadee 907s pulling a 40 car refrigerator train.