DCC conversion including lighting control and a sound solution for a Bachmann Class 37/6 re-sprayed by R3 Sprays in DRS Compass livery.

 

 

Class 37/0 at York

 

Introduction:

Two (OO gauge) Bachmann Class 37/6 locomotives in DRS Compass livery have been sourced from R3 sprays of Falkirk. These incorporate the distinctive upper forward marker lights plus a pair of lower Wipac light housings (at each end) accommodating day & night headlights, rear lights and the low level forward marker lights..... I believe thanks to a cooperative venture with Olivia's Trains. This page describes further enhancements planned for the locomotives, starting with the DCC lighting control system and choice of an appropriate sound decoder with speaker.

DRS Class 37 with the Compass livery. (The sub-class 6 locos have modified lighting compared to this Class 37/0 type).

 

Class 37/6 Running Lights Operation:

All three of the Class 37/6 loco forward marker lights are active at the front of the loco, together with either the day headlight (right hand side) or the night headlight (left hand side). The twin rear lights are both on at the rear of the locomotive unless it is pulling a train, in which case no locomotive rear lights are shown.

 

If the locomotive is acting as the second locomotive in a train and is positioned at the rear of the train, then no front lights are active, but the twin rear lights are switched on.

 

Updated Lighting Control Requirement:

As the locomotives will often operate in consist, mainly on nuclear flask trains, independent control of the lighting at each end is necessary, so that for example on the lead locomotive, only the forward facing lights operate and on the locomotive at the rear of the train, only the rear facing lights operate. In addition, the lead locomotive could usefully include an independent cab light, a detonator flash LED and a double strobe warning light output for shunting in the yard.

Summarizing:

Lead Locomotive: With hook & snow ploughs at End 1:

Location Forward Direction Reverse direction
End 1  Day headlight plus 3 marker lights  Rear lights
End 1  Night headlight plus 3 marker lights  Rear lights
End 1  Detonator flash LED  -
End 1  Cab light  Cab light
End 1  Double strobe light feed  Double strobe light feed
End 2  Rear lights  Day headlight plus 3 marker lights
End 2  Rear lights  Night headlight plus 3 marker lights

9 Function outputs are required

Number two Locomotive:

Location Forward Direction Reverse direction
End 1  Day headlight plus 3 marker lights  Rear lights
End 1  Night headlight plus 3 marker lights  Rear lights
End 2  Rear lights  Day headlight plus 3 marker lights
End 2  Rear lights  Night headlight plus 3 marker lights

6 Function outputs are required

The 3 forward marker lights at each end, will be combined using appropriate series resistors, and driven via isolating diodes from the headlight function outputs.

The decision has been taken to use Legomanbiffo LokSound V4 decoders. An additional expansion board will be used experimentally in the lead locomotive to provide the 3 extra function outputs. (This also includes a control input that could be connected to a Hall Effect sensor, to activate a sound or HW function output when passing over a magnet.

 

Illustrating the new lighting configuration & the colour of the front marker lights and day headlight. Judging from the light shape & colours, they use vintage technology, even if the configuration is now up-to-date!

This photo is included by kind permission of the photographer, Kevin Bates.     

 

Choice of Sound System:

Listening to Youtube recordings, I've decided to go for the Bif 37/0 or 37/4 solution. A 21 pin decoder configuration is required. If it's feasible, I'll fit one unit with a sealed 20x40mm or 28x40mm speaker in the fuel tank and the other with a base reflex speaker in the same location. After comparison tests, I'll retrofit the better solution to the loosing locomotive.

The Class 37/6 fleet I believe are similar to 37/4 except for a lack of ETH electrical train heating facilities (and different lighting). I shall have to seek advice on which of Bif's 37/0 versus 37/4 sound projects are the closest fit...... The view is that 37/4 is closest!

 

The units have arrived (Nice paint job!)

 

 

 

 

Circuit Diagrams: (Updated as the project progresses)

Lead Locomotive Circuit:

This will be the first time I've tried an ESU expansion board. There is insufficient head-height to accommodate the LokSound decoder, piggy-backed on

to the 51970 and the whole assembly plugged into the main PCB 21 pin connector.

Class 37 chassis assembly with a spare 21 pin LokPilot plugged into the 51970 to illustrate the head height problem.

The decoder has to be plugged in upside-down (which I think exacerbates the issue). The LokSound V4 maybe even higher!

The only 51970 manual available is in German, so I've made good use of the Google language translator!

To reduce the height, I plan to remove the main PCB, glue a thin piece of plasticard to the top of the chassis block, to act as an insulator and tape the 51970 / LokSound assembly to the roof of the upper body shell. All lighting connections in the upper body shell will be hard wired to the 51970, via small pieces of strip board. A 6 way connector will connect to the motor, wheel contacts and speaker in the chassis assembly. A two way connector will connect to a detonator flash LED in the lead bogie. All the original contact tabs will be removed or bent to a safe position.

Now the LokSound V4 has arrived, I can search for possible mounting locations:

This position places the high components of the decoder within a recess in the chassis block.

 

The corresponding location in the upper body shell is here. (With only 2 to 3 mm clearance.)

 

Outline cabling plan for Lead Loco.

 

 

Reduced Functionality Rear Locomotive Circuit:

Or something along these lines .......................... The Aux3 & 4 buffers, used in the rear loco, are small 2n7002 SOT23 N-Channel MOSFETs.

 

Modifications required to the lighting hardware:

I've just found some recent DRS 37 photos online that suggest a possible change has started to white (LED technology) marker lights. If confirmed, this means changing the lower marker light LEDs from amber to white. However, upon closer inspection, at least some Class 37 wipac marker lights seem to have white painted reflectors. Some of the "LED?" photos are taken with a low sun beaming directly at the lights. So the white lighting colour may simply be due to sun illuminated white reflectors. Other possible LED sightings on night shots could well be due to oversaturated camera sensors...... so the jury is still out!   One definite requirement is that the headlights need brightening, with a hint of yellow added and similar night headlights also need to be added.

So, if I model the older technology lighting:  Upper marker lights need to be more yellow and less bright. Lower marker lights are about right. Day headlights need to be more yellow and much brighter. Night headlights need to be added (matching the day headlights in colour and intensity).

Quick win: Careful probing with tweezers and a craft knife enabled the upper marker light light-pipe to be separated from its illuminating white LED in the roof of the cab. I added a touch of yellow water colour paint to act as a filter on the surface of the LED, to correct the colour and to drop the intensity, then slid back and refixed the light pipe. Finally the black mastic covering was refitted.

Looking up towards the inside of the cab roof

 
Modifications to the main lighting PCB assemblies:

The lighting boards have a mastic covering sealed in place by electrical tape covering the entire front of the PCB as received. This all had to be removed in order to modify the assembly.

The original lighting PCB is a simple single sided, very thick, hand etched board, populated with 0805 sized SMD LEDs and SMD resistors. Holes are drilled through the board to correspond to the Wipac lighting modules lens tunnels located in the resin cast front pieces. The holes are counter bored on the component side of the PCB so that the LEDs can be placed inverted, facing into the holes, within the counter bore, with contact tabs held in place to the tracks by solder bridges. Indentations in the side of the PCB effectively locate the board into the rear of the front piece. The two rear lights are connected in parallel with a single shared series resistor, as are the amber marker lights (at least on the number 2 end.....see below.)

To increase the intensity of the day headlight, I added a 1k resistor in parallel with the 4k3 original series resistor. (Increasing the current to circa 12mA). I drilled and counter bored a new hole for the night headlight and glued a daylight white 0603 nanolight in place. A 1k5 series resistor set the current through the new LED to around 8 mA.

Thanks to some clumsy soldering, I destroyed one of the marker light LEDs at the number one end. This was replaced with an amber coloured nanolight, but I had to then provide separate series resistors for the original intact marker LED and for the replacement LED, to balance the light intensity.

I've decided to mount the decoder & expansion board in the roof of the upper body shell, so the lighting connection tabs have become redundant.  This makes the task of re-assembly of the modified nose assemblies much less critical, with no lateral forces due to tab spring pressure, to deal with. Two diodes were added to activate the Wipac markers from either day or night headlight. The 4 control wires now required, will be routed beside the cab and then up into the roof of the central body area. They will be soldered to a small piece of tag strip on the roof underside, near the decoder.

On the number one end, an additional strobe warning light has been fitted in the position of one of the lamp brackets. The wiring for this shares the lighting PCB common positive, with the remaining conductor running beside the other wires.

 

Original number two end lighting board complete with connection tabs.

 

The other side of the lighting board after the addition of a night headlight & some hole adjustments to reduce light leakage between rear & headlights.

(The yellow colour around the headlight holes is yellow water colour paint, to give a slightly warmer hue to the headlight beams.)

Inside surface of the front resin castings (showing the Wipac light module tunnels).

 

Outside of the front casting.

 

Modified number two end lighting PCB assembly back in place.

 

I've also added a warning strobe to the number one end.

 

Modified number one end PCB assembly back in place.

 

The lighting has all been tested using a bench power supply, before re-assembly...... which follows next!

 
Bogie updates:

A small SMD white LED is glued adjacent to the leading wheel of the front bogie. The LED wiring shares the same routing as the wheel contact wires. The sound system includes a triple detonator warning sound sequence and this LED will be synchronised with the detonator explosion sounds, to simulate the brief flash that occurs each time the detonators explode.

Based on a photo study of DRS Class 37s, I've also painted the wheel bearing covers yellow and the outside suspension coil springs, red.

 

 

Fitting the loudspeaker:

In the lead locomotive I've fitted a DCC Supplies 58x22x9mm bass reflex speaker in the fuel tank mouldings, facing down towards the track.  In order to dismantle the chassis frame, the bogies need to be removed. The chassis frame can then be unscrewed from the big cast block. A ballast weight surrounding the original lighting switches can then be unscrewed and removed with the switches.

 

Some surgery is required to remove the fixing screw bushes and part of the bridge between the two fuel tank bottoms.

The speaker can then be located.

I've used black mastic (similar to Blue Tac) sandwiched between the motor underside and the speaker rear, to hold the speaker firmly in place.

Holes are also required, of course, to allow air movement between the speaker cone / bass reflex port and the outside air.

And this time, there is room for some protection against a wayward thumb!

 

Chassis re-assembled with new speaker on board, updated bogies and wiring now connected to a new tag-strip board.

 
Wiring up the upper body:

a) The lighting boards:

The number one end nose piece complete with lighting parts was glued back in place. The cables were routed through the available space beside the cab and up through the rear cab bulkhead, into the central roof area.

The strobe series resistor is glued to a small "shelf" to simplify a later value change if required.

 

Number 1 end cab roof now painted white, with cab light glued in place. New series resistors added for the top markers (replacing the originals on the now deleted main PCB). Isolating diodes and tag strip fixed in place..... All we need now is the expansion board and decoder!

 

b) The Expansion Board:

All connections to the expansion board are via solder pads on the underside of the board. (The side nearest the roof underside).

Photo of the Expansion board underside, with the connections photo-shopped in.

 

51970 board underside wired up ready for installation.

 

Some very careful soldering required to avoid any shorts!

The 6 way connector wiring (to motor, wheel contacts and speaker) is on the left (loco number 2 end) and the function outputs with common positive are routed out to the right (loco number 1 end). The latter wires will connect to strip boards which also terminate the lighting cables.

 

Expansion board wired to the tag strips.

Just need to figure out a way to hold it in place in a way that enables removal if things go wrong.

 

This should do the trick! ..... A couple of strips of plasticard glued to the roof.

 

c) Plug in the decoder:

LokSound V4 decoder plugged into the expansion board.

 

 

Completing the chassis assembly:

The chassis side of the multi-way connectors are wired to the tag strip, (as in the photo below) then covered with an electrical tape patch.

 

 

Programming the Lead Loco Decoder & Expansion board:

 

Button control of the lights:

To simplify the control, 3 buttons will operate the lights as follows: Button 0 = End one lights on/off;  Button 11 = End two lights on/off; Button 14 = day or night operation day/night. Direction will be set by the loco direction setting.

 

Preliminaries:

Action CV Orig value Final Value
Master Volume adjustment

63

192 85

 

Function Mapping:    

Function Button Mapping line Original Assignments Sound Slot Original Volume New Button Assignments (change areas in blue)
0(Fwd) 5 headlight FO - - End 1 day running lights forward    (Fwd+day: Fwd Light)
0(Bwd) 6 rearlight FO - - End 1 running lights Reverse    (Rev: Aux 3)
0(Fwd) 33   - - End 1 night running lights forward (Fwd+night: Aux 1)
1 7 Engine prime/start/stop 1 and 2 110&128 Engine prime/start/stop
2 8 Playable High Note Horn 23 110 Playable High Note Horn
3 9 Playable Low Note Horn 24 110 Playable Low Note Horn
4 10 Buffer Clash 4 128 Buffer Clash
5 11 Air Release 5 70 Air Release
6 12 Drivers door slam 6 110 Drivers door slam
7 13 Compressor 7 128 Compressor
8 14 Spirax Valve Popping 8 50 Spirax Valve Popping
9 15 Flange/Wheel Squeal 9 128 Flange/Wheel Squeal
10 16 Dispatcher's Whistle 10 50 Dispatcher's Whistle
11(Fwd) 17   - - End 2 day running lights forward  (Fwd: Aux 4)
11(Bwd) 35   - - End 2 running lights reverse (Rev+day: RearLight)
11(Bwd) 37   - - End 2 running lights reverse (Rev+night: Aux 2)
12 18 Roof Fan/Cooler Group 12 128 Roof Fan/Cooler Group
13 19 Sanders 13 128 Sanders
14 20   - - Lights: Day-off / Night-on
15 21   - - cab light (Aux 5)
16 22   - - warning strobe (Aux 6)
17 23   - - Detonator flash (Aux 7)
18 24 Detonators 18 128 Detonators
19 25 Aux 1 FO - - Remove Aux 1, Add zero momentum
20 26 Aux 2 FO - - Remove Aux 2

 

Detailed CV Changes to achieve new function mapping:

Button Action Prog Line Index CV32 Changes
0 End 1 day running lights forward 5 2 CV325: 0 to 2 (assume CV321=20, CV330=1)
0 End 1 day running lights reverse 6 2 CV346: 2 to 16 (assume CV337=24)
0 End 1 night running lights forward 33 4 CV264: 4 to 0, CV257: 0 to 20, CV261: 0 to 1, CV266: 0 to 4
11 End 2 running lights forward 17 3 CV257: 0 to 4, CV266: 0 to 32 (assume CV260=4)
11 End 2 day running lights reverse 35 4 CV289: 0 to 8, CV292: 0 to 4, CV293: 0 to 2, CV298: 0 to 2
11 End 2 night running lights reverse 37 4 CV321: 0 to 8, CV324: 0 to 4, CV325: 0 to 1, CV330: 0 to 8
14 Lights: Day-off / Night-on 20 3 (assume CV309=1; Check CV314 & CV315 are zero)
15 Cab light (Aux 5) 21 3 CV330: 0 to 64 (assume CV325=4)
16 Warning strobe (Aux 6) 22 3 CV346: 0 to 128 (assume CV341=16)
17 Detonator flash (Aux 7) 23 3 CV363: 0 to 1 (assume CV357=64)
19 Remove Aux 1 Add zero momentum 25 3 CV394: 4 to 0, CV396: 0 to 1 (assume CV390=4)
20 Remove Aux 2 26 3 CV410: 8 to 0 (assume CV406=16)

 

Action Index CV32 CV Change Detail
Set Aux 6 to double strobe 0 CV315 = 6  (double strobe)    CV318=31 (max brightness)   CV319=128 (LED)
Adjust double strobe timing NA CV112 reset to 20 for the desired effect.

 

All working correctly!

 

Active Button Sound Slot Assignments (& Lead Loco Lighting Controls): 

 

Sound & Light Control Function list

Sound Slot Volume changes Volume CVs  (CV32=1 first)
F0 End 1 directional running lights. -    
F1 Sound On/Off and engine start/stop. 1 and 2    
F2 Playable High Note Horn. 23 110-70 435
F3 Playable Low Note Horn. 24 110-90 443
F4 Buffer Clash/Buffering up when moving slowly. 4    
F5 Air Release (Air Dump). 5 70-50 291
F6 Drivers door slamming.   6    
F7 Compressor Startup.   7    
F8 Spirax valves.  8    
F9 Flange/Wheel Squeal Enable. 9    
F10 Dispatcher's whistle. 10 50-80 331
F11 End 2 directional running lights. -    
F12 Roof Fan/Cooler Group. 12    
F13 Sanders. 13 128-75 355
F14 Running lights: Off=day, On=night. -    
F15 Driver's Cab Light. (Loco1 only) -    
F16 Warning Strobe. Light (Loco1 only) -    
F17 Detonator flash. (Loco1 only) -    
F18 Triple Detonators. 18    
F19 Set zero momentum (for test purposes only). -    

 

Motor Control Settings  

CV Original CV Value New CV value Description
2 1 1 Start voltage
3 170 170 Acceleration delay
4 89 89 Deceleration delay
5 152 152 Max. speed setting
6 76 55 Med. speed setting  (<50% CV5 expands slow speed part of range)
49 19 19 Ext Config.1 includes 40kHz motor pulse frequency
51 0 2 Slow driving I component
52 48 40 Slow driving K component
53 125 125 Max speed adjustment
54 48 48 Normal driving K component
55 64 100 Normal driving I component (proportional to motor momentum)
56 255 255 100% range speed control
124 21 5  Ext Config.2 includes Enable adaptive regulation frequency

Smooth running is achieved across the entire speed range, but I'm sure many other combinations will achieve the same result! 

 

 

Snow Plough:

The original design plugs into the coupler socket, so it rotates with the bogie when on a curve. This looks rather unconvincing, so I've cut off the coupler fitting from the back of the plough moulding and instead, super-glued the plough to the bottom surface of the buffer beam. The horizontal joining pieces of the plough moulding have been painted matt black. Adding the hook assembly and a couple of hoses from the accessory bag completes the transformation.

 

Hook, hoses and snow plough added at the number one end.

Now tried on the test track and it behaves very well!

 

Day Running Lights

Night Running Lights

 

Cab Light On

Rear Lights

 

Detonator Flash

 

 

and the story continues with loco number 2...........

 

Differences in the update plan for the second Class 37/6 (compared to the first):

1) Decoder Interface:

This time I've retained the main PCB, but it has been modified to provide the missing 21 pin connector links to the decoder: Aux2, Aux3, Aux4 and Ground connections.

N-Channel MOSFET devices are fitted to convert the Aux 3 and 4 logic outputs to conventional function outputs (Under the paper cover taped over main PCB in the centre of the loco). (A similar Bif LokSound V4 is used, but without an expansion board.)  All the SMD component parts (unnecessary for DCC only operation) were stripped from the board.

2) Lighting board assembly wiring:

An additional wire is routed from the negative side of the lower marker lights, up to the corresponding upper marker light circuit (to eliminate the need for 4 diodes).

6 way and a 2 way miniature connectors provide the interconnect between the upper body shell solder tag strips and the main PCB on the chassis, so that the original spring connection tabs can again be discarded. (Improving reliability and making it less likely that the front piece glue bonds eventually shear.)

3) Speaker:

An ESU 50334 22x42x12mm speaker is fitted, using the standard 12mm deep enclosure. For this speaker, the base of the fuel tanks needs a hole cutting, to ensure that the speaker cone does not make contact with the bottom of the tanks..... The enclosure just fits within the metalwork, when positioned exactly in the centre of the chassis block.

.....so the second loco needs to be handled with some additional care to prevent a wayward thumb damaging to the exposed speaker cone.  A careful comparison of the sound quality of the different speaker solutions in the two locos will be made!

4) Snow ploughs:

The second loco needs tension lock couplers at each end. So the centre part of the plough will have to be omitted. The coupler movement also precludes fixing the outer plough pieces to the buffer beam, so instead, I have attached these to the outside face of the bogies. Not ideal, but I think the ploughs make a very positive contribution to the appearance of the 37s.

Proof of concept on the tail end of Loco number one:

Fixings (before application of matt black paint)

 

Programming the Second Loco Decoder:

 

Button control of the lights:

As before, 3 buttons will operate the lights as follows: Button 0 = End one lights on/off;  Button 11 = End two lights on/off; Button 14 = day or night operation day/night. Direction will be set by the loco direction setting.

 

Preliminaries:

Action CV Orig value Final Value
Master Volume adjustment

63

192 70
Loco address

1

3 4

 

Function Mapping:    

Function Button Mapping line Original Assignments Sound Slot Original Volume New Button Assignments (change areas in blue)
0(Fwd) 5 headlight FO - - End 1 day running lights forward    (Fwd+day: Fwd Light)
0(Bwd) 6 rearlight FO - - End 1 running lights Reverse    (Rev: Aux 3)
0(Fwd) 33   - - End 1 night running lights forward (Fwd+night: Aux 1)
1 7 Engine prime/start/stop 1 and 2 110&128 Engine prime/start/stop
2 8 Playable High Note Horn 23 110 Playable High Note Horn
3 9 Playable Low Note Horn 24 110 Playable Low Note Horn
4 10 Buffer Clash 4 128 Buffer Clash
5 11 Air Release 5 70 Air Release
6 12 Drivers door slam 6 110 Drivers door slam
7 13 Compressor 7 128 Compressor
8 14 Spirax Valve Popping 8 50 Spirax Valve Popping
9 15 Flange/Wheel Squeal 9 128 Flange/Wheel Squeal
10 16 Dispatcher's Whistle 10 50 Dispatcher's Whistle
11(Fwd) 17   - - End 2 day running lights forward  (Fwd: Aux 4)
11(Bwd) 35   - - End 2 running lights reverse (Rev+day: RearLight)
11(Bwd) 37   - - End 2 running lights reverse (Rev+night: Aux 2)
12 18 Roof Fan/Cooler Group 12 128 Roof Fan/Cooler Group
13 19 Sanders 13 128 Sanders
14 20   - - Lights: Day-off / Night-on
18 24 Detonators 18 128 Detonators
19 25 Aux 1 FO - - Remove Aux 1, Add zero momentum
20 26 Aux 2 FO - - Remove Aux 2

 

Detailed CV Changes to achieve new function mapping:

Button Action Prog Line Index CV32 Changes
0 End 1 day running lights forward 5 2 CV325: 0 to 2 (assume CV321=20, CV330=1)
0 End 1 day running lights reverse 6 2 CV346: 2 to 16 (assume CV337=24)
0 End 1 night running lights forward 33 4 CV264: 4 to 0, CV257: 0 to 20, CV261: 0 to 1, CV266: 0 to 4
11 End 2 running lights forward 17 3 CV257: 0 to 4, CV266: 0 to 32 (assume CV260=4)
11 End 2 day running lights reverse 35 4 CV289: 0 to 8, CV292: 0 to 4, CV293: 0 to 2, CV298: 0 to 2
11 End 2 night running lights reverse 37 4 CV321: 0 to 8, CV324: 0 to 4, CV325: 0 to 1, CV330: 0 to 8
14 Lights: Day-off / Night-on 20 3 (assume CV309=1; Check CV314 & CV315 are zero)
19 Remove Aux 1 Add zero momentum 25 3 CV394: 4 to 0, CV396: 0 to 1 (assume CV390=4)
20 Remove Aux 2 26 3 CV410: 8 to 0 (assume CV406=16)

All working correctly!

Motor control CV settings and detailed volume adjustments mirror those of the lead locomotive......except for the horn sounds which are less harsh on the second loco (infinite baffle speaker) and have been left at Bif's original settings...... Interesting! there is a bit more extreme bass in the first loco (bass reflex speaker) but maybe its at the expense of some resonance(s) at higher frequencies, which perhaps are distorting the horn sounds??? More careful comparisons to follow...... 

The second loco number has now been adjusted with a small paint brush from its original 37605 to read: 37606.

 
More on the relative sound quality from the two speaker types:

Listening with the locomotives equidistant, some interesting differences are very apparent. 

The basic engine sounds are fairly similar, albeit with just a hint more extreme bass from the reflex speaker in loco 1, which also sounds slightly better in thrash mode. (Very similar but slight preference for bass reflex).

However, the higher frequency ancillary sounds are very different.

The higher frequency horn sound is the most obvious example. In loco number 2 (with the standard 20x40mm speaker) the sound appears undistorted and Bif's volume level seems about right. However in loco number 1 (bass reflex) the tone sounds harsh and distorted with the higher harmonics predominating and the sound level is much louder (had to turn it down). (Prefer std 20x40!)

The lower frequency horn also sounds fine in loco 2 (std 20x40mm speaker). However it sounds louder and a bit flat in loco number 1 (bass reflex).  (Prefer std 20x40!)

The dispatcher whistle is a little louder in loco 1 (bass reflex) and sounds more shrill. (Prefer bass reflex)

The driver's door slam is a richer sound in loco 1 (bass reflex)...... (Prefer bass reflex)

So.... as you might expect, there is no clear winner. I think I will retain the present speaker fit..... but when operating the two locos together, I'll use only the number two loco horns!

The published bass reflex speaker frequency response gives some good clues to at least some of the above behaviour:

 I bet that peak at around 1500Hz has something to do with the higher tone horn distortion!

Its a shame that I can't find an equivalent plot for an ESU 50334 20 x 40mm speaker sealed in its standard enclosure, for comparison!

 

 
The Train:

Fitting a switchable flashing rear light to one of the Bachmann nuclear flask wagons :

The DRS nuclear trains come in various configurations, always employing two locomotives on a loaded flask train. Sometimes the two locomotives operate in top and tail mode, with one at the front of the train (front lights only) and the other at the rear (rear lights only) with the flask wagons in between. On other occasions, the two locomotives double head the train, with the flask wagon(s) to the rear. A flashing rear light is then fitted to the rear flask wagon. 

I want to be able to operate in both train configurations, so I need to fit a switchable flashing rear light to one of my Bachmann flask wagons:

Having failed to find a way to separate the flask moulding from the main body, I had to remove the bogies, dismantle the chassis and carry out some access surgery to the floor of the chassis, below the flask moulding. This provides plenty of room to accommodate the circuitry and a convenient mounting location for the switch.

The dismantled Bachmann flask wagon, showing the holes cut to accommodate the new parts.

 

The circuit diagram. The flashing LED is my last from those purchased from Bromsgrove Models (Now sadly no longer trading).

The bridge diodes are 1N4007 types. The chip LED is a red Nanolight LED installed in the original flask wagon rear light moulding. The switch is one removed from the Class 37 locos.

Wheel contacts are installed on the bogie below the rear light.

 

Circuitry glued to a piece of plasticard inserted (and glued) into the inside of the flask.

The switch PCB is super-glued to one of the three steel plate ballast weights.

 

The recessed on/off switch below the flask.

 

Phosphor bronze wheel contact strips fixed in place. (Before black paint is applied to the plasticard mounts.)

 

The working tail light on the rear flask carrier lamp bracket.

 

37605 & 37606 "top 'n tail" a short flask train.

 

37605 & 37606 "double head" a short flask train.

 

 

.........You've read the book! Now check out the video!

Click here to watch the Class 37 video

 

Adding some useful extra ESU functionality:

ESU include several useful "logic functions" that can be assigned to available control buttons:

 

1) Sound fader:  Intended for use in tunnels etc, but also a handy quick volume adjustment if other family members complain about the noise:-)

Add to button 20:   Set register CV32 to 3 Set CVF=CV406 to 16 (normal default) Set CVN=CV413 to 8.

Set the amount of volume reduction: CV133 to around 75 for a little over half volume.

Note: Beware of the ESU "volume control" option..... although in theory more flexible, its easy to accidentally over cook, putting the speaker at risk!

 

2) Diesel notch-up and Diesel notch-down...... Not all LokSound V4 sound projects are compatible, but fortunately Bif's usually are:

Add notch-up to button 21: Set register CV32 to 3 Set CVF=CV422 to 64 (normal default) Set CVN=CV429 to 2.

Add notch-down to button 22: Set register CV32 to 3 Set CVG=CV439 to 1 (normal default) Set CVN=CV445 to 4.

Once you have started manual notching, ongoing notch control is manual via buttons 21 OR 22 until the loco is stopped and then notched back to idle, with both buttons 21 & 22 restored to the off position.

 

Revised Sound & Light Control Function list

F0 End 1 directional running lights.
F1 Sound On/Off and engine start/stop.
F2 Playable High Note Horn.
F3 Playable Low Note Horn.
F4 Buffer Clash/Buffering up when moving slowly.
F5 Air Release (Air Dump).
F6 Drivers door slamming.  
F7 Compressor Startup.  
F8 Spirax valves. 
F9 Wheel Flange Squeal.
F10 Dispatcher's whistle.
F11 End 2 directional running lights.
F12 Roof Fan/Cooler Group.
F13 Sanders.
F14 Running lights: Off=day, On=night.
F15 Driver's Cab Light. (Loco1 only)
F16 Warning Strobe. Light (Loco1 only)
F17 Detonator flash. (Loco1 only)
F18 Triple Detonators.
F19 Set zero momentum (for test purposes only).
F20 Volume fader.
F21 Diesel notch-up.
F22 Diesel notch-down.

 

Supplier website links:

 

R3 Sprays of Falkirk    The two Class 37s were re-painted in DRS compass livery at this specialist model maker.
Digitrains    Source for Nanolight pre-wired chip LEDs required to improve the lighting.
DC Kits etc    Source of Bif 37/4 LokSound V4 based sound system and the Standard 20x40mm ESU speaker used in the second loco.
DCC Supplies    DCC specialist supplier based in Worcestershire. Source of bass reflex speaker installed in the lead loco.
RS Components    Source for N-Channel MOSFETs used as buffers in the number 2 loco.
Amazon    Unlikely source for the ESU expansion board via their German supplier Arstecnica. (Also available from Coastal DCC, I found out later.)

 

The photos of the real Class 37/0 were taken several years ago at York Station. The model photos will be taken using a Canon Ixus, on the kitchen worktop.    

 

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