Dead-Rail Conversion of the Lionel H-7 2-8-8-2

Introduction

Warning: This is a very long, detailed post!

I like Lionel steam locomotives because Lionel designed them for simplified servicing, and Lionel’s documentation and parts are easily-available. Also, some of the locomotives, such as the H-7, are nicely detailed and are rich in features such as extensive lighting, smoke, and excellent speakers. Lionel very much “gets” the importance of the user experience.

What I don’t like are Lionel’s high-rail flanges and three-rail operation. The high-rail flanges look awful and will not work well on 2-rail trackage that meets NMRA standards S-3.2 “Scale Track, Standard Scale.” Also, many of the locomotive driver wheels are mounted on a “trapped” axle, requiring removal of the driver wheels from the axle “in situ” with a wheel puller and subsequent remounting in the correct “quarter.”

I have performed three dead-rail conversions of Lionel’s H-7 2-8-8-2 locomotive. This post will be a composite of these three locomotives.

The conversion process consists of the following:

  • Mechanical conversion: modifying or replacing all wheels and coupler replacement.
  • Electronics: All Lionel electronics are removed and replaced with a DCC decoder
  • Dead-rail: Addition of a ProMiniAir (PMA) receiver and DCC amplifier, battery, antenna, charging plug, and power/charging switch

Mechanical Conversion

Locomotive

Before proceeding with the locomotive conversion, several “magic screws” must be removed to separate the upper boiler shell from the lower shell and wheel chassis. This step is necessary to provide clear access to the drivers for removal and modification.

Removal also provides access to the locomotive’s electronics for removal and replacement with a DCC decoder and its wiring.

Locomotive shell disassembly #1
Locomotive disassembly #2
Locomotive disassembly #3

Removing the flexible hose mounting shown below provides clearance to remove the drivers.

Removing the flexible hose mounting provides clearance to remove the drivers.

After I gained enough clearance around the drivers, I used a wheel puller to remove those drivers whose axles were “trapped” in the chassis.

Using a wheel puller to separate a driver from its trapped axle. For illustrative purposes only, since the brake shoes require removal to prevent mechanical interference, and this particular driver pair can be removed from the frame by removing the retaining plate held in place by two screws.

The locomotive drivers present several issues:

  • Large, ugly flanges
  • Grooved tires with rubber traction tires
  • All drivers are uninsulated. This aspect is important only if you want track-powered 2-rail operation.

Lionel manufactures the locomotive driver center and flange as s single unit with a separate cylindrical tire with no flange.

The photo below shows an end mill to separate the driver tire from the driver center integrated with the flange. The process was the following:

  • A 3/16″ brass tube was fit in the axle.
  • A small brass tube was inserted into the crank-pin hole to prevent wheel rotation while milling.
  • Two pieces of brass close to the height serve as height spacers that avoid cutting into the flange.
  • The tooling is a 1/16″, two-flute end mill in a Tormach collet
  • Cutting oil was applied.
  • The end mill was very carefully translated along the radius, cutting into the cylindrical tire without cutting into the flange.
  • After the radial cut was deep enough, I used an “ordinary screwdriver to pop off the tire with an axial twist.
Removing the cylindrical tire with a 1/16″ end mill shows the integrated Lionel driver center and flange.
Lionel driver wheel with the tire removed. The 3/16″ brass tube loosely fits the axle center to hold the driver in lathe or milling chucks.

I used two strategies for modifying the Lionel driver wheels:

  • Machine down the large flanges and leave the tire in place with the driver uninsulated. I used this technique when using the locomotive strictly as dead rail.
  • Completely machine off the flange. I use this technique when creating insulated drivers for 2-rail operations using track power.

Machining down the drivers

I used a 3/16″ brass tube as a reasonably close match to the driver’s axle diameter. Because the fit is not tight, a separate small brass tube is inserted in the driver pin that will butt up against the lathe chuck’s jaws when cutting torque is applied. This technique is a bit of a kludge, but I have successfully machined down the flanges of 8 H-7 drivers on two different H-7s with this technique.

Before matching down the large flanges, you must address the grooved tires. The rubber in these tires increases the tire diameter, increasing the chances that the reduced flanges will derail. And these rubber tires are a bad idea since they could cause the locomotive to simply stall rather than slip when pulling heavy loads. Stalling is very bad since it dramatically increases the motor current, potentially causing a decoder shutdown and/or significant heating.

I used J-B Weld 8267 SteelStik Steel Reinforced Epoxy Putty Stick to fill the rubber traction rim groove. This material is metal-filled, providing traction and wear resistance.

I applied an excess of putty in the groove, and after curing, I cut the putty excess down to the radius in the lathe. It’s a fool’s errand attempting to shape the putty in the groove. The epoxy sets fairly quickly, so you have a short window of time to work the putty into place.

Machining the epoxy-steel filling to the proper diameter

The photo below shows the finished driver wheel with the Steel Reinforced Epoxy Putty machined to the driver center radius and a machined-down flange with a flange height of 0.036″ and a flange width of 0.040″. As previously, a small diameter rod was inserted into the side rod hole to prevent wheel rotation relative to the axle while machining.

The tire, after machining the flange to 2-Rail standards

Completely Machining OFF the Original Flange

First, I’ll show you how I created a new tire with a small flange. This is a long detailed section, perhaps of interest to only a few of you.

First, the driver’s tire center must be prepared. The idea is to entirely cut off the integral flange to ensure a constant radius from the front to the back of the driver center.

First, you must remove the cylindrical tire. In this case, you can use a cutting wheel to cut a slot through the flange and the tire without cutting into the driver center. Then the tire can be popped off with an axial twist using a standard screwdriver. Care must be taken not to nick the driver’s wheel center.

The slightly undersized brass tube fits somewhat loosely in the crank-pin hole but will prevent slippage in the spindle by butting against the jaws once torque is exerted by the cutting tool on the rim as the spindle rotates.

The tooling and technique to completely machine off the integrated flange

After the wheel center’s rim is machined flat, I use 0.010″ fish paper to insulate the left-side drivers. You can hold the fish paper in place with a touch of CA on the side of the rim opposite where the fish paper ends will join. This allows a shorter run to hold the fish paper tight on the rim while applying CA to the ends.

Fish paper was applied to the wheel center.

With our wheel center ready to mount inside a tire, we now create a tire with the proper dimensions. Caveat: My tire machining technique fits my modest matching skills using a small Sherline lathe. This technique is wasteful of metal blanks, but their cost is low. Other more skilled model railroad machinists have more efficient techniques that utilize a larger lathe and specialized tooling.

To help the discussion, the figure below shows the terminology from NMRA Standard S-4.2. The important terms/dimensions are flange width, flange depth, and tread width. Creating a tire within an acceptable range of these dimensions is necessary to ensure that the driver will work on 2-rail trackage defined by NMRA standard S-3.2.

Wheel dimension definitions (from NMRA Standard S-4.2)

I start with a 1.5″ diameter Ledalloy 12L14 1″ long blank obtained from OnLineMetals.com. This represents a maximum driver size of 72″, which is plenty large for our 57″ plus twice our flange depth of 0.036″ for 2-rail operation (1.1875″+2 x 0.036″=1.2655″).

Ledalloy blank

A 1/2″ hole is drilled into the center of the blank to provide clearance for the boring bar that will hollow out the blank to fit the outer diameter of the driver’s center.

A 1/2″ hole is drilled into the blank to provide clearance for the boring bar.

The blank is then placed in the lathe, the face is squared off with an end cut, and then a side cut reduces the blank’s diameter to the final wheel diameter + 0.072″ to account for the additional flange depth (0.036″). For our H-7’s 57″ drivers, this diameter works out to 57/48″=1.1875″ plus twice our flange depth of 2 x 0.032″=0.072 for 2-rail operation: 1.1875″+2 x 0.036″=1.2655″.

The blank after a face cut and side cut to a final diameter equal to the wheel’s final diameter + 2 x the flange depth. Note this picture does not show the center hole that should already be drilled.

Now we make an angled side cut to create the tire surface by tilting the Sherline lathe’s spin axis by 2.5-3.0 degrees. This cut produces a shallow angle across the tire’s tread width. This angle was obtained from NMRA Recommended Practices 25.

The Sherline lathe allows you to create a tilted side cut.

A careful series of side cuts are made to reduce the blank to the wheel’s diameter at the base of the flange step with a width of the wheel width (N) of 0.172″ – the flange width of 0.039″ = 0.132″. I use a wheel width slightly smaller than “code 175″ (0.175”, from NMRA Recommended Practices 25) to improve appearance, and maintain operability with 2-rail track standards.

Angled side cuts reduce the front of the blank to the final wheel diameter and tire width of ~0.132″

Next, we “straighten out” the lathe and use a boring bar to hollow out the blank’s center to be slightly smaller than the driver’s center diameter. This cut reduces the amount of material removed during the difficult cut-off operation.

A boring bar is used to enlarge the blank’s center hole to slightly smaller than the driver’s center wheel outside diameter.

Next, the tire is cut off from the rest of the blank at a distance greater than 0.039″ (the flange width) behind the flange step.

The blank is cut off more than 0.039″ inches behind the flange step

The now-separate tire is remounted in the lathe using the flange step as an indexed surface, and a careful series of face cuts are made to reduce the flange width to 0.039″.

The back face of the tire is face cut until the flange width is 0.039″

A spacer (an old tire cut off the driver) is now inserted to displace the flange from the lathe chuck’s jaws to provide clearance for rounding the edges of the flange with a file.

A spacer (an old tire) to provide clearance for rounding the flange’s sharp edges

With the lathe spinning, a file is used to carefully smooth the sharp edges of the flange.

The tire, after rounding the sharp flange edges with a file.

Now, the tire is remounted against the lathe chuck’s jaws, and a series of careful cuts with the boring bar increases the tire’s inner diameter until the driver’s center fits inside the tire. This step is tedious since very small (0.001″) cuts should be used to prevent making the tire’s inner diameter too large! The fit should not be extremely tight since we will apply Loctite to the rim of the driver’s wheel center to lock the tire to the driver’s wheel center.

Fitting the driver’s wheel center into the tire. This tire had the insulating fish paper attached to the driver’s wheel center.

Loctite 609 is applied to the fish paper, and the driver’s center is inserted into the new tire. While inserting the driver’s center, I take the opportunity to ensure it is pressed into the rim to the proper depth. This depth is a bit of a judgment call based on examining the original mounting depth.

Before the Loctite dries, the driver’s center must be aligned with the tire. I use a simple technique of inserting a 3/16″ metal rod or tube into the driver axle hole and mounting the assembly in the jaws of a milling clamp with a small “v” machined into one side of the jaws, as shown in the photo below. I firmly press the tire rim onto some brass plates placed on top of the jaws, then tighten the jaws to very lightly bind the metal tube and rotate the driver wheel. This rotation action will force the driver’s center into alignment with the tire.

While aligning these components, I take the opportunity to ensure the driver’s center is still pressed into the rim to the proper depth.

Tender Mechanical Modifications

I removed the rather ugly Lionel coupler by cutting off the tender coupler mount and mounting a Kadee coupler directly to the tender. Micro-Mark coupler shims provide the proper coupler mounting height.

Tender coupler modifications
Tender coupler mount with coupler shims

DCC Additions

I used a Zimo MX696KS DCC decoder from SBS4DCC with the “Standard Gauge Steam Locomotive Alco/Baldwin Mallet 2-8-8-2” sound file DA_R_US_2_8_8_2 V2.zip. Modifications were made to the function mappings and set-up of the smoke unit.

Some of the sound project’s settings are shown in the following screen captures from Zimo’s ZCS software.

Zimo sound file settings, screen #1. The settings on this page set the loco’s long address and turn on the decoder’s acknowledgment of changed CVs.
Zimo sound file settings, screen #2. Note that F4 turns on two function outputs for the firebox effects.
Zimo sound file settings, screen #3. Note the two random flicker outputs and the smoke effects output.
Zimo sound file settings, screen #4. Smoke unit settings for both smoke (heater) and smoke unit fan.
Zimo sound file settings, screen #5. Not all sound functions are shown.

Dead-Rail Conversion

Tender Modifications

My typical 14.8 LiPo battery did not comfortably fit in the back end of the tender, but a rather unusually-shaped 14.8V LiPo batter from MTO fit well: the TRAIN-10 LI-ION.

The 14.8V LiPo TRAIN-10 LI-ION battery.
Tender dead-rail additions. Note the battery, ProMiniAir receiver and DCC amplifier, antenna connections, power switch, and charging plug.
Underside view of tender dead-rail components

The tender’s LEDs must have “protection” resistors added since Lionel provided these resistors on electronics boards that were removed for dead-rail conversion.

Protection resistors were added for the rear light (“R.L”) and rear marker lights (“RML”)

Locomotive Electronics Modifications

The conversion strategy is completely removing all Lionel electronics and replacing them with a Zimo MX696KS DCC decoder, providing excellent sound, lighting, and smoke unit control.

These original Lionel locomotive electronics were all removed
Locomotive DCC decoder installation

Because the original Lionel electronics provided the protection diodes for the locomotive’s LED marker lights at low voltage, 5K resistors were added in series with the maker lights so that 14.8V power would not burn them out when activated by the Zimo decoder.

The red LED lighting for the firebox presented a bit of a challenge. The photo below shows where I added protection resistors for the two sets of LEDs that flicker independently using the “random” firebox setting for the Zimo decoder’s FO6 and FO8 outputs, as shown on the ZCS configuration menus elsewhere.

Electrical modifications for the firebox LEDs
Heater wiring
Smoke unit, number board, and marker light wiring

For one of the H-7s, I replaced the incandescent cabin light with an LED. See the photo below.

The incandescent cabin light was replaced with an LED to reduce power consumption.

I replaced the original low-current LED front marker lights with “nano” LEDs after I accidentally burned them out.

Front marker light replacement

The Proof in the Pudding

The video below is the “proof in the pudding,” showing off the lights, firebox effects, smoke, and great sound!

The “proof in the pudding”

Dealing with Loss of RF Signal in Dead-Rail for Onboard DCC Decoders

Note: This post deals with details of various brands of DCC-compatible, wireless RF receivers operating in the 902-928 MHz “ISM” band that connect to onboard DCC decoders. Some aspects of the discussion may apply to other RF bands as well.

Typical application. In some cases, such as the Airwire transmitters, the throttle and transmitter are combined. Also, the receiver and amplifier may combined, such as for Airwire and Tam Valley Depot receivers.

The designers of various DCC-compatible RF receivers have a couple of strategies for what output to provide to the onboard DCC decoders when a valid RF signal is lost:

  1. Output the random pulses that the RF receiver naturally outputs when a valid RF signal is lost. This option will cause most DCC decoders to maintain direction and speed while the DCC decoder “sifts” the random pulses searching for valid DCC packets.
  2. Output a fixed, positive Direct Current (DC) voltage to one of the DCC decoder’s “Track” inputs and a zero voltage DC the other “Track” input when either a) RF signal is lost, or b) when the RF transmitter does not send sufficiently-frequent “keep-alive” DCC packets. The latter is true for the Airwire CONVRTR. How the DCC decoder responds to these DC “Track” inputs depends upon DCC decoder configuration and, unfortunately, DCC decoder manufacturer discretion.

There are several NMRA-specified Configuration Variables (CV’s) that affect how DCC decoders handle the loss of valid DCC packets and are important to understand when the DCC decoder is connected to the DCC output of DCC-compatible RF transmitters because the RF receivers may lose or receive corrupted RF signal from the dead-rail RF transmitter.

The NMRA standard S-9.2.4, section C “Occurrence of Error Conditions” states “Multi Function Digital Decoder shall have a Packet Update time-out value.” Further down on line 60 the standard states “A value of 0 disables the time-out (i.e., the user has chosen not to have a time-out)”. This part of the NMRA standard is not universally-implemented by manufacturers, and it affects how decoders will respond to the loss of RF transmission of DCC packets. To implement this requirement, the NMRA standard S-9.2.2 has defined the recommended (R), but not mandatory (M), CV11, Packet Time-Out Value. A value of CV11=0 is defined to turn off the time-out, but CV11 is frequently not implemented.

However, another CV that is often implemented addresses some aspects of loss of DCC. The optional (O) CV27, Decoder Automatic Stopping Configuration, is under re-evaluation by NMRA, but the NMRA has taken no definite action some time. Here is what the NMRA standard S-9.2.2 currently (as of 2019) states about CV27: 

Configuration Variable 27 Decoder Automatic Stopping Configuration
Used to configure which actions will cause the decoder to automatically stop.

Bit 0 = Enable/Disable Auto Stop in the presence of an asymmetrical DCC signal which is more positive on the right rail.
“0” = Disabled “1” = Enabled

Bit 1 = Enable/Disable Auto Stop in the presence of an asymmetrical DCC signal which is more positive on the left rail.
“0” = Disabled “1” = Enabled

Bit 2 = Enable/Disable Auto Stop in the presence of an Signal Controlled Influence cutout signal.
“0” = Disabled “1” = Enabled

Bit 3 = Reserved for Future Use.

Bit 4 = Enable/Disable Auto Stop in the presence of reverse polarity DC.
“0” = Disabled “1” = Enabled

Bit 5 = Enable/Disable Auto Stop in the presence forward polarity DC.
“0” = Disabled “1” = Enabled

Bits 6-7 = Reserved for future use.

Since DCC decoder manufacturers frequently do implement CV27, what electrical output the DCC-compatible RF receiver provides to the DCC decoder upon loss of a valid RF signal will influence how the DCC decoder responds. We will break this down for various brands of DCC-compatible RF receivers in the 902-928 MHz ISM band in the following subsections.

Note that some DCC decoders will not honor CV27=0; i.e., all auto-stopping features disabled. For example, with CV27 set to 0, the Zimo MX-696, and probably other Zimo DCC decoders as well, will continue speed and forward direction if positive DC level is input to the “Right Track” DCC input, and a zero DC level is input to the “Left Track” DCC input. Under these “track voltage” conditions, the locomotive will stop if originally moving backward. Some (but not all) DCC-compatible RF receivers, such as the Airwire CONVRTR, provide these DC inputs, if a valid RF signal is lost, but only if connected correctly.

The “correct” connection relates to how the user connects the DCC output from the RF receiver to the “Track Right” and “Track Left” inputs of the DCC decoder. Under normal circumstances, when there is a valid RF signal, which way the DCC decoder connects to the RF receiver does not matter. Under the exceptional case of DC-only output by the RF receiver, if it loses a valid RF signal, which way the DCC decoder connects to the RF transmitter does matter. The user will likely want the locomotive to continue forward with the loss of a valid RF signal, so some experimentation is required to determine which of the RF transmitter DCC outputs should connect to which of the DCC decoder’s “Track” inputs to achieve the desired behavior.

Example DCC waveform output from a DCC-compatible RF receiver when there is a valid RF signal
Example random pulse output from a DCC-compatible RF receiver when there is no valid RF signal. Note the waveform’s superficial similarity to valid DCC output.

As a further complication, the user should probably turn off the decoder’s “analog” mode of operation by setting Bit 2 of CV29 to 0 to force the decoder to use “NMRA Digital Only” control of ”Power Source Conversion” (see the NMRA standard here). If Bit 2 of CV29 is set to 1, and again we emphasize the user should probably not activate this feature, then “Power Source Conversion Enabled” and then CV12 determines the power source; the most common of which is CV12=1, “Analog Power Conversion.”

Airwire CONVRTR Series

CVP Airwire CONVRTR-60X tender installation. The CONVRTR operates on Airwire channels 0-16. Note that the U.FL antenna lead was later connected to the CONVRTR. The LokSound L V4.0 DCC decoder mounting harness can be seen mounted on the tender wall opposite the CONVRTR, and its Track Left/Right inputs are connected to the CONVRTR-60X’s DCC A/B outputs.

When the CVP Airwire CONVRTR loses a valid RF signal or receives insufficiently-frequent DCC Idle packets, it detects these conditions and outputs a fixed DC voltage to the decoder. Consequently, the user should set CV27 according to the description above.

While it may seem that the user would want the locomotive to stop if its RF receiver loses a valid RF signal, consider what might happen in tunnels or locations remote to the DCC RF transmitter. Getting stuck under these circumstances if a valid RF signal is lost is probably not what the user wants, so we strongly suggest that the user set CV27=0.

The user is cautioned, however, that some DCC decoders, such as the new ESU LokSound 5 L DCC, do not honor the CV27=0 setting unless the “polarity” of the “Track Right/Left” is connected “correctly” to the CONVRTR’s “A/B” output. Experimentation may be required to determine the correct connection, but my experience is: CONVRTR A <–> Decoder Track Right & CONVRTR B <–> Decoder Track Left

QSI Solutions Gwire and Tam Valley Depot DRS1 Series

The QSI Solutions GWire operates on Airwire Channels 0-7. If the U.FL plug (at the upper-left corner of the Linx Transceiver chip) connects to an externally-mounted antenna, the antenna wire at the upper-left corner of the GWire board should be cut off at board level, or better yet, unsoldered.
The Tam Valley Depot DRS1, MKIII, operates on Airwire Channel 16
The Tam Valley Depot DRS1, MkIV, operates on Airwire Channels 0-16 (as well as other frequencies). Note the internal antenna on the right-hand side of the board.

The QSI Solutions Gwire and Tam Valley Depot DRS1, MkIII and MkIV DCC-compatible RF receivers will output random pulses to the onboard DCC decoder when a valid RF signal is lost, so setting CV27 is probably of no use. On the “plus” side, most DCC decoders will maintain locomotive direction and speed in the presence of these random pulses since the DCC decoder is actively sorting through these pulses for valid DCC packets, which is usually the behavior the user wants.

A Blueridge Engineering webpage describes how to easily modify the GWire for use as an RF receiver for any onboard DCC decoder.

OScaleDeadRail ProMiniAir Receiver

OScaleDeadRail ProMiniAir receiver operates on Airwire channels 0-16. The ProMiniAir can also be configured to operate as a DCC-compatible transmitter that wirelessly transmits DCC from any DCC source on Airwire channels 0-16.

The OScaleDeadRail ProMiniAir receiver has a default long address of 9001. Like the ProMiniAir transmitter, the ProMiniAir receiver’s channel can be reset in “OPS Mode” by setting CV255 to a value in the range of 0–16. The ProMiniAir receiver has the following options when a valid RF signal is lost:

  • Output random pulses to the onboard DCC decoder: The user can set the ProMiniAir receiver to output the random pulses when it loses a valid RF signal by setting CV246 to 0 in “OPS mode” at the ProMiniAir’s address. In this case, setting CV27 for the onboard DCC decoder is irrelevant because the random pulses from the ProMiniAir receiver will cause the onboard DCC decoder to maintain the speed and direction of the locomotive while it is “sifting” through the random pulses for valid DCC packets.
  • Output either fixed positive or negative voltage DC to the onboard DCC decoder: In this case, setting CV27 for the onboard DCC decoder at its address is relevant. The user can set the ProMiniAir receiver to output fixed DC voltage when it loses a valid RF signal by setting CV246 to 1 in “OPS mode” at the ProMiniAir’s address. A positive DC voltage is output by setting the ProMiniAir receiver’s CV248 to 1 in “OPS mode” at the ProMiniAir’s address, or a negative DC voltage is output by setting CV248 to 0. If the user does not want the locomotive to stop with the loss of a valid RF signal, then set CV27=0 for the onboard DCC decoder at its address. Of course, setting CV27 to other values (see above) in the DCC decoder will determine how the DCC decoder responds to the fixed DC voltage that the ProMiniAir outputs to the onboard DCC decoder upon loss of a valid RF signal.

Wrap-Up

It’s an unfortunate fact of life that we can lose a valid RF signal from our DCC-compatible transmitter. However, with a little study of DCC decoder documentation, and possibly a bit of experimentation, gracefully coping is definitely possible.