Monday, 19 June 2017

DB Loco Mechanism Options

As an aid to deciding which mechanism to use for Marbelup Models DB Locomotive, the following summarises the main features of the Hollywood Foundry (HF) and ViTrains (VT) mechanisms.

Comparison of ViTrains bogie (left) and Hollywood Foundry bogie (right)

Bogie Wheelbase

Prototype: 3810 mm = 59.5 mm in S scale
HF Bogie: 59.5 mm
VT Bogie: 58 mm

Wheel Diameter

Prototype: 1016 mm = 15.875 mm in S scale
HF Bogie: 15.7 mm
VT Bogie: 14.8 mm Note: Upper part of wheels is largely hidden by bogie sideframes

Flange Depth

HF Bogie: 0.65 mm (RP25)
VT Bogie: 1 mm - operates on Code 70 or larger rail

Cost (for drive bogies and motor):

HF Single Bogie Drive: Approx. $200
HF Double Bogie Drive: Approx. $250
VT Drive: $140

HF Mechanism Features

  • Choice of 6-wheel (single bogie) or 12-wheel (dual bogie) drive
  • For single bogie drive, cab area is clear to allow for interior detailing
  • Worm gear on each driven axle, with dual belt drive from bogie input shaft

VT Mechanism Features

  • 8-wheel drive (centre axles are idlers and lightly sprung)
  • Twin flywheels included
  • Smoother operation
  • Quieter operation
  • Cab area is clear to allow for interior detailing
  • Worm gear on each bogie with spur gearing to powered axles
Back to Marbelup Models Home Page

Friday, 9 June 2017

DB Loco Assembly Tips

Please Note - This is a "preliminary" version and subject to change during construction and testing of the development models.

Parts List (Preliminary - subject to change)

In addition to the 3D printed parts, the following parts must be obtained separately by the modeller:
  • Brass wire for handrails, etc. (0.4 mm, 0.6 mm - 3 x 300 mm lengths)
  • Air hoses - e.g. Detail Associates #6206 - 12 required.  (Vacuum brake hoses are included.)
  • Handrail Knobs (4) for uncoupling levers - e.g. Markits 1.5 mm (short) - available from Railwest Models.
  • Handrail Stanchions (optional) - A-Line D1070 or D1071.  Limited quantities available from Marbelup Models.
  • Vi-Trains Class 47 mechanism.  Limited quantities available from Marbelup Models,
  • Hollywood Foundry mechanism, with NorthYard Wheels and Mashima 1833D motor - see below for details.
  • DCC decoder and speaker (both optional)
  • Light Emitting Diodes (LEDs) for headlights 4 x 3 mm (sunny white) and optic fibre (2 mm)
  • LEDs (red and white) and optic fibre, if operating marker lights desired
  • lead or other weighting material
  • Kadee couplers #146 for scale coupler height,  #149 for HO coupler height (see below)
  • Kadee draft gear boxes #262 (supplied)
  • Fixing screws for body, couplers and fuel tank:
    2-56 x 19 mm, 4 required for central body fixing screws
    2-56 x 6 mm, 8 required, for remaining body fixing screws and couplers.
    2-56 x 12 mm, 2 required for fuel tank.
    Kadee #256 nylon screws can be used for the fuel tank, couplers and end body fixing screws.
  • Fixing screws for motor (ViTrains mechanism only) 2-56 x 25 mm (1"), 4 required - to be trimmed to required length.
  • Fixing screws for speaker M1.4 x 6 (slightly longer is OK) - 4 holes are included correct size (1.1 mm) and screws should make their own thread, tapping shouldn't be required.  Suitable screws are available from DCC Concepts - Part No. DCS-PHB156 or in assortment DCS-PHBSet.  Although described as 1.5 mm, the DCC Concepts screws are actually M1.4 thread.
  • Fixing screws for bogie sideframes - self tappers, 1 mm dia. x 3 mm long (8 required).  Suitable screws are available from DCC Concepts - Part No. DCS-PH103
  • Fixing screws for nose - self tappers, 1 mm dia. x 5 mm long (2 required).  Suitable screws are available from DCC Concepts - Part No. DCS-PH105
  • Paint and decals, as desired.

Underframe Preparation

Remove the support structure from the 3D-printed underframe.  Take particular care around areas with delicate detail, including the vacuum hoses and ... (details to be added).

Clean out the indicated holes with a 1.8 mm drill bit and tap with 2-56 thread.  Note that the four holes closest to the motor cutout are for the ViTrains mechanism only.  If desired, the coupler mounting holes can be drilled right through as the top surface of the underframe will be hidden by the loco body.

Underframe Holes to be Tapped 2-56 (viewed from below)
If intending to fit couplers at HO height, file out 1 mm from the bottom of the coupler mounting holes, as per diagram below.  The headstock is only 0.5 mm thick in this region.  Up to 1.25 mm can be removed, if required, to accommodate fine adjustment of coupler height.

Headstock Modification for HO Coupler Height

Bogies and Drive Train

There are two mechanism options: Hollywood Foundry and ViTrains.  The DB loco underframe is specific to each mechanism, so the choice of mechanism must be made at the time of ordering.

See comparison of the mechanism options.

Please refer to the separate assembly tips for:


The coupler height of the DB loco has been set at the correct scale height for WAGR/Westrail narrow gauge rollingstock, i.e. 12.2 mm (above rail height) rather than the HO coupler height (9.9 mm) which is commonly used for most Sn3½ models.  This has been done because the correct height "looks better" for modern locos and rollingstock.  For correct scale coupler height, use Kadee #146 couplers.  

Provision has been made in the underframe design to lower the couplers to match the HO coupler height by using Kadee #149 couplers which have an "overset" shank together with a spacer approx. 1 mm thick between the coupler box and mounting pad.  The bottom of the coupler openings in the headstocks is only 0.5 mm thick, and this thin section needs to be filed 1 mm deeper to allow for the lower coupler mounting height.

The #146 and #149 couplers are both "long shank" style which avoids the problem of the "glad hand" on opposing couplers from fouling the cowcatcher.  The suggested draft gear boxes are Kadee #262 (supplied).  Kadee suggest assembling the coupler so that the main part of the draft gear box is on the bottom and the lid is on top.  The draft gear boxes simply snap together.  

Due to the length of the DB loco and long end overhang, coupling of 4-wheel wagons next to the loco is not recommended on curves of 850 mm radius or less.  The loco itself will operate on curves of 700 mm radius, or slightly less, but the coupler overhang is probably the limiting factor.

Underframe Details

There are four large air pipes to be added to the air reservoirs on the underframe, as highlighted in yellow below.

Underframe Air Piping (viewed from below).
These can be formed from 0.8 mm brass wire, and glued into the holes provided in the air reservoirs and underframe.  

Approx. dimensions for the L-shaped pipes are as follows:
  • Front left: 5 mm + 8.5 mm
  • Front right: 13 mm + 8.5 mm
  • Rear left and right: 34 mm + 8.5 mm.
Note that the front right pipe should have a gentle upwards bend, about midway along the longer part, to match the height of the hold in the underframe.

DCC and Sound

The underframe is specially designed to accept a 23 mm square high-bass speaker (Soundtraxx 810129 or equivalent) if a sound decoder is to be installed.  The speaker faces downwards on a "sound duct" which has a "tunnel" through it for the front drive shaft.  

The underframe speaker mount include four holes, nominally 1.1 mm diameter, which are suitable for M1.4 fixing screws, 6-8 mm long.  Ideally, the holes should be tapped with a M1.4 thread, but the screws can be inserted without tapping.  (DCC Concepts sell suitable screws - part number DCS-NB14x6 or as part of an assortment DCS-Nbset.)

The recommended sound decoder is the Soundtraxx Tsunami EMD 645 Non-Turbo.  The Tsunami "AT" style decoder model 828048 is suitable and slightly cheaper than the TSU-1000 style model 827109.  More recent equivalents are also available in the Soundtraxx Econami and Tsunami 2 ranges.

Note: The above links are for the SoundTraxx web site.  SoundTraxx do not sell direct but their products are available from many retailers.

Body Preparation and Details

Take care when removing the support structure from the body, especially around the cab windows to avoid damaging the vertical dividers between the windows.  

Once the body has been "cleaned up", it is also necessary to remove the two temporary braces which link the fixing posts near the centre of the body, as highlighted in yellow below, as well as another one just behind the cab.  These have been included to protect the body during production and shipping, and must be cut away to provide clearance for the motor, etc.  These can be cut with a fine-toothed razor saw or a cutting disk in a rotary tool, at low speed.  

The ten fixing holes in the body shell and nose should be tapped with a 2-56 thread.  If necessary, clean out the holes prior to tapping using a 1.8 mm drill bit.

Nose Assembly

The nose is a separate 3D-printed part.  This has been done to avoid stepping on the sloping top surface of the nose from the 3D printing process.  Once the supports have been removed from the nose, a light sanding may be required on the bottom surface to remove the slight stepping present there.

Small holes have been provided to secure the nose to the cab with small screws, e.g. 1 mm dia. x 5 mm long.  The screws should be inserted from inside the cab, into the nose.  The holes are angled so there is some hope of reaching them with a small screwdriver.

Once satisfied with the fit of the nose, it can be superglued onto the cab, preferably from the inside to avoid traces of glue on the visible surfaces.

Handrails on Body

Starter holes are provided on the body for three handrails which can be formed from brass wire (e.g. 0.3 or 0.4 mm).  The starter holes should be drilled out slightly larger, e.g 0.05 mm larger than the wire size.

One handrail is inside the topmost recessed step on the left side of the loco, next to the radiator grilles.  The spacing between the holes is 3.5 mm (centre-to-centre).

Photo by G Stallard
The other two handrails are on the roof, adjacent to the recessed steps.  The spacing between the holes is 8.5 mm.  Photos indicated that the bends in the top handrails should have a radius of approx. 1.5 mm.  Radiussed corners can be formed by bending the wire around the shank of a drill bit, or using special pliers with round jaws made for wire forming.

Photo by G Stallard
Starter holes are also provided on the sides of the long hood for the handrails for the rear steps, and on the nose for the front handrails. - see below.

Handrails on Cab Front

Two handrails either side of central window:
  • Right side: 7.5 mm between hole centres
  • Left side: 7.5 mm + 12 mm between hole centres, with 65 degree bend between straight segments to match slope on nose.

Handrail on Top of Nose

  • Left side, on top step notch: 4 mm between hole centres
  • Left side, on sloping section: 8.75 mm between hole centres
  • Right side, on sloping section: 11 mm between hole centres*
* Front hole for this handrail is missing from some nose prints, but can be easily be marked and drilled.

Handrails on Underframe

The 3D-printed chassis incorporates holes approx. 0.6 mm diameter to house the vertical handrail posts, typically cut from 0.6 mm brass wire.  There are also starter holes on the rear steps, and on the headstocks, for the end handrails.

One option for the long handrails is to solder each section of handrails from 0.6 mm brass wire.  Marbelup Models has developed a PDF template for the handrails which can be downloaded and printed.  Ensure it is printed at 100% size - check the scale on the bottom of the template to ensure the scaling is correct.
Handrail Diagram - Download PDF for Accurate Dimensions

Handrail Diagram (PDF)

On the real locos, the rear handrails and the rear end of the long side handrails have 2 fixing points near the rear steps.  Holes been provided in the underframe for the additional fixing points, if desired, which would entail soldering additional short lengths of wire to the respective handrails.  The vertical spacing between the upper and lower fixing points is 8 mm.

Use of A-Line Handrail Stanchions

An alternative, which is potentially easier than soldering, is to use preformed steel handrail stanchions available from A-Line (Division of Proto-Power West, USA).  These are available from various online hobby shops and/or eBay.  (Marbelup Models has limited stocks of these stanchions available at $15 per pack of 35 stanchions.  Each loco requires 16 stanchions.)

A-Line Handrail Stanchions
Although these stanchions are intended for HO locos, the two longest sizes are sufficiently long to be trimmed to the correct length for the DB .  The A-line part numbers are D1070 (extra long) and D1071 (long).  The stanchions should be trimmed at the bottom.  After trimming, file off any rough edges from the cut end.  

The number and lengths of stanchions required are as follows:

  • 21 mm long, 8 required - left side
  • 18.5 mm long, 7 required - right side
  • 16.75 mm long, 1 required - right side, rearmost stanchion.
Note that the length should be measured from the top of the "loop".  When installed, the bottom of each stanchion should be flush with the bottom of the running boards.

The holes in the 3D-printed chassis should be carefully drilled out to accommodate the stanchions (suggested drill size: 0.75 mm  - test on some scrap plastic first).  

After preforming the long handrails as per the PDF template, test fit each handrail without stanchions.  Once satisfied with the fit, remove each handrail and thread on the 8 stanchions.  It is suggested to orient all stanchions the same way, e.g. with the open side of the top loop inwards.  For the right side handrail, ensure the single, short stanchion is at the rear.

Carefully insert each stanchion vertically into the drilled holes.    It is probably best to insert the stanchions part way initially, then go along and press them down to the full depth, and also insert the ends of the handrails into the holes in the underframe.  Make sure the bottom of each stanchion is level with the underside of the running boards.

Once all the stanchions are in place and the long handrails threaded through, check that all the stanchions are vertical and make any necessary adjustments.  Then, the stanchions can be glued into the holes in the running boards and the handrails glued into the holes in the underframe.  It is optional whether to glue the handrails where they pass through the loops in the stanchions.

Separately form the U-shaped handrails on the side, and the end handrails from 0.6 mm wire, as per the template.  Install and glue the U-shaped handrails into the underframe.

Temporarily fit the loco body to the underframe in order to test fit the end handrails, the top ends of which locate into holes in the loco body.  Only glue the bottom end of the end handrails, to allow for future removal of the body.  It is suggested that the top end of the handrails should protrude approx. 1 mm into the body, to allow them to be sprung out slightly when the body is removed.


Four horns are included as part of the 3D-printed underframe.  Carefully remove them from the underframe, leaving the spigots attached to the horns intact as much as possible.  Only two are required, with two spares.

(Alternate horns can be source from detail parts suppliers e.g. in brass, if greater robustness is desired.)

Starter holes are provided for the horns on the front wall of the cab (right side) and on the left side of the long hood, just behind the vestibule door.  Consult photos appropriate to the era being modelled to determine correct horn placement.

Drill out the starter holes to suit the diameter of the spigot on the back end of the horns.  Carefully trim the unwanted spigot (projecting sideways or lengthways) from the horns.


The holes provided in the body shell for headlights are nominally 1.8 mm diameter, but typically slightly undersize due to the 3D printing process.  The headlights should be 2 mm in diameter, so drill the holes out to 2 mm taking care not damage the thin surround around the hole.

(The holes are deliberately undersize because the thin surround would not print otherwise, as the minimum detail thickness is 0.5 mm. and the outside diameter of the surround is 2.8 mm.)

One method of lighting the headlights is to use a short length of optic fibre together with a 3 mm LED (Light Emitting Diode).

The DB locos had "sealed beam" headlights for which "sunny white" LEDs are a suitable approximation.  (Many older locos had larger diameter headlights with replaceable bulbs which tended to have a more yellow appearance, similar to "golden yellow" LEDs.)

Note: Incandescent (filament) lamps are not recommended due to their high operating temperature which may damage the 3D print material.

To attach the LED to the optic fibre, 3 mm black heatshink tubing is recommended.  With the use of a hot air gun, the heatshrink tubing will shrink to form a snug fit over the optic fibre.  However, the hot air may well be hot enough to melt the plastic optic fibre, so the trick is to shrink the tubing over the shank of a 2 mm drill bit, them slide the drill bit out and slide in the optic fibre.

Typical steps are:

  1. Cut heatshrink tubing to length, e.g. 8-10 mm.
  2. Hold 3 mm LED in a small vice by its legs, with the clear lens uppermost.
  3. Push the cut length of heatshrink tubing over the clear lens of the LED.
  4. Hold the shank of a 2 mm drill bit inside the heatshrink tubing while applying heat from a hot air gun.
  5. When it has cooled, withdraw the drill bit and insert the desired length of optic fibre.  For the rear of the loco, you will probably have to feed the non-flared end of the optic fibre through the curved hole provided (from the outside) and attached the LED with attached heatshrink tubing on the inside.
CAUTION: Do not used the hot air gun or other heat source to shrink the heatshrink tubing in close proximity to the loco body or other 3D printed parts as they may distort due to the heat.

For the dual headlights, it is simplest to wire the two LED in series as this reduces the wiring and avoids the need for two separate resistors.  A resistor of around 2K2 (2,200 ohms) is a suggested starting point for LEDs powered from DCC decoders.

Marker lights can also be drilled out and illuminated if desired.

Sunday, 4 June 2017

DB Loco Hollywood Foundry Underframe Assembly Tips

Hollywood Foundry Drive Components

It is up to the modeller's individual preference whether to fit two drive bogies or a single drive bogie plus a dummy bogie.

Drive bogie specifications: G16.5/B29.8+29.8/W15.7-110/22:1DUALBELT/NOBOL
Dummy bogie specifications: G16.5/B29.8+29.8/W15.7-110/NOBOL

To order the above bogie configurations, please use the special order page on the Hollywood Foundry web site and copy and paste the above codes into the Product Description field.  

The modeller should purchase the wheels, 15.7 mm diameter, from Northyard in New Zealand and send them to Hollywood Foundry in conjunction with each order.  Marbelup Models has a limited quantity of Northyard wheels available for purchase for $35 per set of 12 wheels.

Contact Northyard direct via email: for a quote for the wheels.  The current (September 2016) catalogue price is NZ$1.95 per wheel (not including postage).

Each loco requires 12 x 401N wheels, as illustrated in the following extract from the Northyard Catalogue:

The current (February 2016) pricing for the required Hollywood Foundry parts is:

Drive bogie - $91.30 (same price as Bullant In-Line 3-Axle)

Dummy bogie - $52.80 (same price as Bullant 3-axle Dummy)

Motor: Mashima M1833D - $31.35

Universal Joint Set for 1.5 mm shafts (set contains parts for 4 joints.  1 joint is required per drive bogie, but it is recommended to purchase 1 set per loco to allow for some "spares".) - $4.19 per set

Silicone Tubing - used for flexible coupling between motor and drive shaft(s).  Supplied free by Hollywood Foundry if requested when ordering other parts.  Tubing will fit both 2 mm motor shaft and 1.5 mm drive shaft.

Total price for two drive bogie configuration is $218.14 (plus approx $10 postage)
Total price for single drive bogie configuration is $171.94 (plus approx $10 postage)

Please not that the above prices set by Hollywood Foundry and are subject to change.

As of late 2016, Mashima Motors are no longer in production.  Marbelup Models has designed the chassis to accommodate other motors including Canon, which are available from some hobby shops in the same size as the Mashima M1833D.  Marbelup Models also has limited stock of another alternate motor which will fit in the space available.

Bogie Pivot Assembly (Hollywood Foundry)

Note:  Prior to assembling the Hollywood Foundry bogies to the underframe, place each bogie on a flat surface (glass is ideal) and check that the bogie doesn't rock from end to end.  Some bogies have been found to have the centre axle set a fraction of a millimetre too low, which means the outer axles don't properly contact the rails and could cause derailments.  If you are unlucky enough to experience this problem, contact Hollywood Foundry for repair or replacement under their Lifetime Warranty.

The underframe is designed for a nominal thickness of washers/packing of 1 mm between the top of the bogies and the mounting surface on the underframe.

The Hollywood Foundry bogies are supplied with two plastic shouldered washers, a formed phosphor bronze spring, a flat steel washer and an M1.4 machine screw. 

For assembly to the 3D-printed underframe, it is recommended to discard the flat steel washer and upper plastic shouldered washer.  This should result in the correct loco height from the rails and the phosphor bronze springs (at both ends) should minimise side-to-side rocking of the loco while allowing some movement to cope with uneven track.

Secure the bogie with the M1.4 screw provided, but don't tighten it fully so as to allow some for and aft rocking movement of the bogie as well.

To check the loco height, fit the underframe and body together, with couplers attached, and check the coupler height against a Kadee HO coupler height gauge.  Be aware that the 3D-printed underframe is somewhat flexible on its own, and relies on the rigidity of the body to keep it straight and level.  The top surface of the footplate should be 26 mm above rail level.

If the loco sits too low, a spacer should be cut from styrene and added above the phosphor bronze spring (or glued to the bogie pivot on the underframe).  The spacer needs to be large enough, e.g. 8 mm square, so that the phosphor bronze spring is effective in minimise rocking.

If side-to-side rocking is still a problem, Marbelup Models can provide details to fabricate a mounting plate from brass sheet and wire which can be fitted to the top of the rear bogie, to provide a "3-point" suspension.  Marbelup Models has also produced a 3D-printed version of this mounting plate which is printed in high-detailed stainless steel at a cost of approx. $16.

Drive Shaft Assembly (Hollywood Foundry)

Brass rod 1.5 mm diameter is suitable for the drive shaft(s).  The required length is approx xx mm.  Check the exact length required from your model.  Allow some "end play" in the universal joint at the bogie end to accommodate movement of the bogie on curves or uneven track.

Hollywood Foundry have published an instruction sheet on the basic assembly. One end of each shaft requires a "flat" to be ground or filed to accommodate the male end of the plastic universal joint.  Grind or file a flat on the shaft with a minimum length of about 2 mm.  The depth of the flat should be 0.3 mm, so that the measurement over the remaining shaft is 1.2 mm.  Don't force the joint onto the shaft if it is very tight, as it may split later.

Hollywood Foundry can supply silicone tubing (free on request with each order) for the motor end of each drive shaft.  The tubing is sufficiently flexible to fit both the 1.5 mm drive shafts and 2 mm motor shaft.

The drive shaft for the front bogie of a loco with both bogies driven must pass through the "tunnel" in the speaker housing.  One technique is to attach the drive shaft to the motor before installing the motor, then pass the drive shaft through the "tunnel" to engage with the universal joint on the bogie and, finally, fix the motor in position with the short M2 screws provided with the motor.  The rear drive shaft can be attached to the motor last, as there is no "tunnel" to get in the way.

For a loco with one powered bogie, it is suggested to install the powered bogie at the rear to avoid the "tunnel" and leave the cab free for interior detailing, if desired.

DB Loco ViTrains Underframe Assembly Tips

ViTrains Drive Components

Remove the plastic body from the ViTrains Class 47 locomotive by gently easing the body sides out to disengage the lateral grooves on the chassis, as per the instruction sheet supplied with the loco.

Unsolder the wires connecting to the bogies and motor (3 green, 3 black) from the Printed Circuit Board (PCB) on the ViTrains chassis.

Unscrew the 4 black screws and remove the PCB.  

Remove the motor and its rubber mounting block. 

Unclip the bogies by gently pressing on the raised clip which engages in the curved slot in the chassis.  Take care with this step as the clip can break if bent excessively.  

Set aside the two bogies and motor with their wires attached.  All other parts of the loco can be discarded.

Bogie Sideframe Assembly

Unclip the keeper plate/sideframe assembly from the underside of each bogie.  There are clips at each end and on each side between the wheels.

Using a fine-bladed razor saw, or similar, cut off the dummy Class 47 sideframes flush with the insides of the sideframes, as per photo below.  Also cut the smaller attachment points at the ends of the keeper plate.  Discard the dummy Class 47 sideframes.

Cut lines to remove dummy Class 47 sideframes.
Optionally, the parts of the previously-removed "sprue" can be fitted to the underside of the keeper plate to provide a representative profile of the traction motors, when the finished loco is viewed side on at track level.  

At this stage, the central joining piece (highlighed in red, below) can be left intact.  Position the two "traction motors" aligned with the matching notches in the ViTrains bogie.  Orientation is not important.  Carefully, drill two 0.8 mm holes through the holes in the "traction motors" for 1 mm dia. x 3 mm long fixing screws.  After drilling the holes, remove the central joining piece and attach the individual "traction motors".  Don't use screws longer than 3 mm as clearance is needed for the gears.

Adding dummy "Traction Motors" to Keeper Plate
Reassemble the keeper plate to the ViTrains bogie. The orientation of the keeper plate is not important.  It the wheels fell out previously, ensure that the power collection wires are correctly located in the grooves on the inside faces of the wheels.
ViTrains Bogie after Reassembly
Remove the support structure and clean up the 3D-printed bogie sideframes.

Remove the central "sprue" from the bogie sideframes as per the diagram below.  The cut lines are highlighted below  in yellow.  Also cut away the raised section, highlighted in red, where the sprue is attached to the end "traction motor".  Part of the "sprue" is (optionally) reattached later, to represent the traction motors.

Cut lines for 3D-Printed Sideframes
Attach the 3D-printed sideframe to the ViTrains bogie, from below.  First, insert the end of the bogie (closest to the brass shaft coupling) into the dummy "traction motor" recess on the end of the 3D-printed sideframe.  Gently spread the 3D-printed sideframe apart to allow the projections on the ViTrains bogie to engage in the rectangular holes on the inside of the 3D-printed sideframe.

Fitting 3D-Printed Sideframes to ViTrains Bogie
Check that the sideframes are fully engaged with the ViTrains bogie by measuring the distance between the insides of the sideframes.  It should measure 23 mm.  If the measurement is greater, check that the rectangular holes on the inside of the 3D-printed sideframes are free of supports, and remove any burrs from the cut ends of the ViTrains bogie.

Once satisfied with the fit, gently squeeze the sideframes together while drilling two 0.8 mm diameter holes into the ViTrains bogie frame, using the small holes provided in the 3D-printed sideframes as a guide.  Use 1 mm dia. x 3 mm long screws to secure the 3D-printed sideframes in position.

Clip the assembled bogies into the "oval" holes in the underframe.  Again, take care with this step to avoid breaking the clips on the bogies.  The green wires should be on the left side of the loco.

Motor and Drive Shaft Installation

Remove the drive shafts and motor clamp from the separate parts "sprue", and clean up the individual parts.

Position the motor in the recess in the underframe, with the wires towards the rear of the loco, and the motor clamp on top.  Secure motor clamp in place with four 2-56 screws.  After checking that the motor clamp is level, measure the excess length for each screw and trim screws to length, e.g. with a cutting disc in a Dremel or similar motor tool.  The remaining screw length should be about 21 mm.

Before refitting the motor clamp, insert the 3D-printed drive shafts into the mating fittings on the bogies and motor flywheels.

Refit the motor clamp and secure with screws trimmed previously.  

Rotate the flywheels by hand to check the motor rotates smoothly.

Height Above Rail Level

The top of the footplate should be 26 mm above the top of the rails.  If necessary, minor adjustments can be made by adding packing (e.g. thin sheet styrene) between the bogies and underframe.  Note that the underframe on its own is slightly flexible, so checking of the height should be done with the loco body attached.

At the front end of the loco, packing can be inserted on the underside of the U-shaped bracket which rests on the top of the bogie assembly.

At the rear end of the loco, packing, can be inserted in the crescent-shaped cutouts which rest on the short metal rods protruding sideways from the bogie assembly.  Alternatively, the short metal rods can be bent slightly upwards or downwards, taking care that they are the same on both sides so that the loco sits level.

Note that the underframe is designed so that the front bogie can rock slightly from side to side to accommodate minor track irregularities, such as when entering a superelevated curve.  


For DC operation, connect the 3 green wires to each other and connect the 3 black wires to each other.  Verify that the loco moves in the correct direction.  The loco should move forward when the left rail is negative and and the right rail is positive - or check the direction against other DC locos.  They should all move in the same direction on the same powered section of track.

For DCC operation, connect the bogie pickup and motor wires to the DCC decoder in accordance with the decoder wiring instructions.  The green pickup wires are equivalent to the red wires (left side) for standard DCC wiring.

Thursday, 1 June 2017

Marbelup Models DB Loco Kit Project

The Marbelup Models project to produce a 3D-printed "kit" of the Westrail DB diesel locomotive in Sn3½* scale is progressing well and the 3D design is complete!  Test prints of all parts have been ordered from i.Materialise in Belgium and should arrive around mid-June 2017.

Completed 3D Design (Computer Rendering)
Basically, the "kit" will consist of 3D-printed parts for loco body, underframe, fuel tank and bogie sideframes,   The general construction will be similar to the Marbelup Models D and DA locos.

The model represents the DB in "as delivered" form.  As is common, some changes were made over the working life of the locos.  The most significant change is to the steps.  The steps at the ends were built out so as to be vertical, rather than inset on the original loco (to clear platforms).  Also the side steps behind the cab, which were originally attached to the front bogie, were replaced with longer steps hanging down from the underframe.

The expected "kit" cost will be about $410 per loco.  This is a bit more than initially estimated, partly due to the fact that the DB is a large loco.  Also, i.Materialise have removed the discount for ordering multiple parts, which adds a bit to the cost of the smaller parts (bogies, fuel tank, etc.). (Actual cost subject to variation due to exchange rate variations against the Euro and/or prices increases in 3D printing.  Current pricing is based on AU$1.00 = 0.666 Euro.)

Note that the majority of the 3D-printed parts will be printed in "Standard Resin" by i.Materialise.  Standard resin is a relatively new material and is translucent with a yellow tint.  The "Prime Gray" material, used for most previous Marbelup Models items, is still available but is about 30% more expensive than previously.  Initial indications are that the print quality of Standard Resin is equal to or better than Prime Gray, and the material specification indicate that it is stronger and less brittle.

To complete the loco, the purchaser must also source a mechanism as well as some detail parts, screws, couplers, DCC decoder (if required), paint, decals, etc.  Assembly instructions will be available online.

There will be two options for the mechanism.  One is the "inline" drive bogies available from Hollywood Foundry, as have been used for the D and DA locos.  One or both bogies can be powered, depending on the modeller's preference.

The second option is to use the motor and drive bogies from a ViTrains UK Class 47 loco.  The Vitrains motor is fitted with flywheels and the assembled mechanism is smooth and quiet.  The drive is to the outer 4 wheels of each bogie, the centre, free-rolling axles being lightly sprung.

See Summary of Mechanism Options for more information.

Marbelup Models has purchased several ViTrains locos from the UK.  These are available for purchase as a "donor" mechanism at a cost of $140 each.  This compares favourably with the Hollywood Foundry mechanisms which cost around $200 for single bogie drive and $250 for double bogie drive (including cost of NorthYard wheels.)

The 3D-printed underframe will be available in two versions, to suit either the ViTrains or Hollywood Foundry mechanism.  The different mechanisms are not interchangeable.  The 3D-printed bogie sideframes are also specific to each mechanism.

The coupler height of the DB loco has been set at the correct scale height for WAGR/Westrail narrow gauge rollingstock, i.e. 12.2 mm (above rail height) rather than the HO coupler height (9.9 mm) which is commonly used for most Sn3½ models.  This has been done because the correct height "looks better" for modern locos and rollingstock.  Provision has been made in the underframe design to lower the couplers to match the HO coupler height by using Kadee #149 couplers which have an "overset" shank together with a spacer approx. 1 mm thick between the coupler box and mounting pad.

Some modellers have paid a $100 deposit as per the initial invite for "expressions of interest" published in May 2016.  Those who have paid a deposit will take priority as the kits become available.  Additional kits will be available after the initial orders have been fulfilled, and there is no fixed limit to the number of kits produced, due to the 3D-printing process which allows additional kits to be produced "on demand".

Deposits are still being accepted, which will secure a place in the "queue" for delivery.  A $100 deposit per loco can be paid by PayPal (to or Bank Transfer.

Expected delivery time: 1 year, i.e. progressively from end of June, 2017, based on the order in which deposits have been paid.

Deposits refundable only if Marbelup Models unable to deliver, for any reason, 2 years from commencement, that is by end of June 2018..

You can pay the $100 deposit using the PayPal link below:

Specify Scale and Gauge*

Please email Marbelup Models for bank details if you wish to pay by Bank Transfer.

Please note that complete ready to run locos will not be available from Marbelup Models, although it is possible that "third parties" may offer an assembly and/or painting service at additional cost.

* The DB loco kits proposed in HO and HOn3½ scale will not be produced at this stage, due to lack of paid deposits from HO modellers.  The idea of producing kits in HO scale may be revived at some time in the future but only if there is strong interest.