FD Van Construction Tips

"As Printed" with supports still attached.

Removal of Support Structure

The FD van is printed upside down, which results in the optimum surface finish on the louvres which are obviously the most prominent part of this model. The downside is that removal of the supports from the roof will leave small attachment points which require cleaning up, and there will be some visible stepping on the roof.

In general, it is best to first cut away the supports from the areas which have small details, and the areas which will be visible on the the finished model with a sharp hobby knife.  (An X-Acto style knife with a #11 fine blade can be useful for the fiddly bits.) Take particular care removing the supports from the brake handle, vacuum hoses, door tracks, and underfloor brake gear.  Note that there will probably be a tiny support at the top of each vacuum hose.

The brake handle has a "sacrificial" guard around it to provide some protection against breakage during production and shipping of the 3D printed model.  It is suggested to leave this in place until most of the other finishing work has been done to minimise the risk of breakage to these delicate parts.

Once the supports have been cut away from the delicate areas, the remaining supports can be broken away by wiggling them or applying pressure to break the small attachment points.  It is not necessary to remove all the supports from inside the van body as these will not be visible on the finished model.

The visible stepping on the roof can be smoothed of using a craft knife with a scraping action, then finished with sanding stick or sandpaper.  Any minor indentations should be filled with modelling putty (e.g. Tamiya) and sanded smooth.

Take care when scraping/sanding the roof to not damage the rain strips.  It may be helpful to make a concave, curved sanding tool using a segment of cardboard mailing tube or plastic pipe, with sandpaper attached with glue or double sided tape.  The radius of the roof is 33.3 mm so, ideally, the sanding tool should have a similar radius.

Sanding tool for roof, with handle from scrap wood.

Couplers

The FD is designed for Kadee "whisker" couplers.  Either the #158 (scale size) or #148 (normal size) couplers can be used, with #262 draft gear boxes.

The draft gear boxes supplied with the #148 and #158 couplers do not fit as they have a different mounting hole position.  The #262 draft gear boxes are narrower and have been used because they allow details such as the brake hoses to be positioned the scale distance from the van centre line.  Also, the #262 draft gear boxes are easier to use as the lid snaps into position.

Note that the height from rail level to the coupler mounting surface should be 11.5 mm, the standard for Kadee couplers.

The holes for the couplers are designed to accommodate 2-56 or 8BA screws without tapping.  

Note:  Tapping the holes is not recommended as it will remove more material and potentially lead to stripped threads.

W-Irons

The design of the FD van is optimised to suit the "closed" W-irons, made from etched brass, which are available from Railwest Models.  This is because the closed W-irons, when used in conjunction with Markits brass bearings, are the correct width for wheels with 26 mm axles, so that the sides of the W-irons are truly vertical.  (Refer to Sn3½ Blog article for more details.)  Other W-irons can be fitted with minor adjustments.

The mounting height for the W-irons is optimised for wheels of the correct scale diameter, i.e. 12.5 mm diameter.  If using the commonly available wheels of 12 mm diameter, packing pieces of approx. 0.25 mm will be necessary between the W-irons and floor.

"Closed" (left) and "Open" W-irons.  Photo courtesy of Railwest Models

Remove the W-irons from the fret, fold them up and fit brass bearings in the usual way.  If using compensation with the "closed" W-irons, the rocking W-iron is at the extreme left of the photo above, with the fixed W-iron adjacent to it on the same fret.

The underframe of the wagon includes eight small holes at each end for mounting the W-irons, using 1 mm x 3 mm pan-head self tapping screws.  Different sets of holes are used at each end, depending on the type of W-iron used, and each W-iron requires only two screws.  (These screws are available from DCC Concepts part no. DCS-PH103.)  

(Of course, you can glue the W-irons in position if you prefer, in which case the holes and grooves included in the underframe help to locate the W-irons in the correct position.)

The fixed W-iron is installed at end of the wagon opposite the brake handle.  Use the fixing holes which are located on the axle centre line, 15 mm apart, to fix the W-iron into position.   If using 26.5 mm wheels, the wheel flanges will most likely rub on the screw heads, in which case the W-iron should be glued in position (e.g. with super glue or Pliobond).  Screws can be used to locate the W-iron and hold it in position until the glue has dried.

To achieve compensation, the rocking W-iron is installed at the end of the wagon with the brake handle.  Remove the separate pivot bracket from the centre of the W-iron and fold up the ends to match the etched holes in the W-iron.  It may be necessary to bend the ends of the brackets slightly more than 90° to minimise slop in the rocking W-iron.  The idea is to use the holes in the pivot bracket to secure the rocking W-iron to the wagon, using the pair of holes on the wagon centre line spaced 10 mm apart.  To allow clearance for the screw heads, file or grind a hollow in the side of the W-iron.

As per the intended W-iron assembly procedure, pass a piece of brass wire (e.g. 1 mm diameter) through the pivot bracket and the corresponding holes in the side of the W-iron, and solder the wire on the outside only to the pivot bracket.  Check that the W-iron can move freely with respect to the pivot bracket.  Cut the centre of the brass wire out, to allow access for the fixing screws.  Cut the wire initially at a 45° angle to avoid forcing the sides of the W-iron apart, then cut the remaining section out leaving just enough to form the pivots for the rocking action.  Also trim the excess wire from the outside of the W-iron, and file the wire and solder until it is almost flush with the sides of the W-irons to allow it to be slid sideways between the brake shoe supports.

Fit the wheels (26 mm axle length) and check that wagon sits at the correct height above the rails, i.e. the coupler mounting surfaces should be 11.5 mm above rail level, and adjust if necessary.

After checking that the wagon runs happily, fit the cosmetic W-iron/axlebox assemblies to the outside of the brass W-irons.  It will probably be necessary to clean out the holes in the W-iron/axlebox assemblies with a 2 mm (or slightly larger) drill bit to fit over the brass bearings.

Handrails

Handrails can be formed from 0.4 mm brass wire.  Starter holes are provided on the side and ends, which should be opened out with a 0.45 mm or 0.5 mm drill bit.

The lengths of the handrails (centre to centre) are as follows:

• doors: 9 mm
• ends (vertical, above brake handle and shunter's step): 6.5 mm

Once in position, the handrails can be secured with Super Glue.

Floor and Weighting

To allow the van to be 3D-printed in one piece, the underframe is a skeleton only, with no floor.  If desired, rectangles of styrene (approx 1 mm thick) can be cut and glued between the underframe cross members to represent the floor.  Optionally, some or all of these pieces can be cut from sheet lead to add weight to the van.  

With no additional weight, the finished FD weight approx. 46 grams.  The suggested weight for a van of this length is approx. 68 grams (See Sn3½ Blog.).

The dimensions of the "floor" pieces are as follows:

• Centre: 11.5 x 10.5 mm 
• End: 12 mm x 6 mm 

Some of the pieces may require slight trimming around small details.  Because the vacuum cylinder occupies one of the "squares" near the centre of the wagon, lead weights should be applied to diagonally opposite "squares" to maintain equal weight on either side.  The unused "square" can be filled with styrene sheet if desired.

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