Sunday, 17 March 2013

Semaphore Peco

Timber semaphore's are currently available from Kerian Ryan Models for NSWGR 7 mm O scale [# KRN023] but searching the web lead to examining the possibility of using the Great Western Railway semaphore kits marketed by Peco [#LK-790] to create a plausible NSWGR working semaphore. Kerian Ryan's signal is an all brass model, highly accurate and excellent value but some modellers feel more comfortable in plastic and well - this one looks different...!

The general outline for this model is in a article published in the Australian Journal of Railway Modelling in Issue #8 on page 13. See Data section of this blog for official drawings for the home or distance signals

Two-position lower quadrant semaphore   [click for more information] The distant signal in NSW has a fixed upper green light. Lower Quadrant Semaphore signals use an arm that works in a horizontal position and may be lowered to (about) a 45-degree angle, they can only give two indications. In the horizontal position a red light is displayed, in the lowered position a green light is displayed. There are two types of arms. A Distant signal uses a fishtail arm, Home and Starting signals use a square-tail arm. Semaphore distant signals in New South Wales are fitted with a fixed green light, positioned above the arm and spectacle, so that they may be easily distinguished from stop signals at night. Although yellow lights were tried, neither they, nor yellow and black arms were adopted, meaning that distant signal arms are still painted red and white.

If the Home or Starting signal is at Danger, the Distant signal will be at Caution, its arm in the horizontal position with a green light over a red light exhibited at night. If the Home and Starting signals are Clear, the Distant will be Clear, its arm lowered, with two green lights exhibited at night.

Pole Preparation.
Begin by marking the location for the lamp mount 12 mm from the top of the post. As this is to be a working signal a wired LED will be routed through the cavity in the tapered pole from the kit. To do this create a 1 mm wide notch in one of the pole halves at 10 mm from the top to intersects with factory cavity. Chamfer the lower edge at 45 degrees to reduce the angle of entry of the LED wire into the pole cavity. 

The tapered pole components supplied with the kit are correct but have distinct dishes in their faces which will need to be filled with spot putty. On this model automotive spot putty was used and works as well as the more expensive model putty's. After drying for 24 hours dry block sand with 120 grit aluminium open cut paper.

Identify the correct sides by tapping the pole halves together with green painter masking tape then drill all holes shown on the supplemental plan at the end of this article. All holes are 0.020'' [0.5 mm] except the balance pivot which is enlarged at installation. 

Hint: Locate the simulated bracket for the platform this is at the REAR of the pole.

Why painters tape - it can be removed week's later..!

Lighted Lamp Assembly
The lamp body was modified by drilling a 0.03'' [0.8 mm] hole through the centre of the simulated lens then a hole was then drilled from the base to intersect with the first hole. Both holes are then enlarged to 2.0 mm and the remaining part of the lens is cut flush.

Install a tested TCS YELLOW mico LED into the lamp body. Bend the wire parallel with the base of the PCB and install through the hole in the base of the lamp body. The hole will have to be extended into the lamp body further to centre the LED at the lens opening. When correct the wires are lightly twisted together for there full length and a piece of styrene was shaped into a wedge to jam the LED into its position - a drop of liquid adhesive is applied to keep it in place.

Fit the lamp to the base provided by threading the wire through the base and glue.  The wire is fitted through the notch in the side of the pole. The wires are retained by small balls of blue tack to aid assembly. Once happy with the fit glue both pole halves together using a liquid cement and a fine brush. The pole was assembled with the joint vertical pressed on a sheet of glass to align both sides. Gluing was done about 20 mm at a time from the base to the top checking the fit on the way to the top - glue lamp base into its final position, set aside to dry.

Glue the packers shown onto the poles. Styrene strips used were 0.156'' & 0.080'' x 0.010''  - 10 mm from the top of the pole to the top edge of the larger size with the smaller size centred on the larger.

Balance Arm Assembly
Fit the etch brass eye bolts supplied with the kit with ACC to provide a guide for the rods. Remove the straight balance arm and solder a piece 0.030" brass wire 20 mm long through the pivot hole projecting 5 mm on one side. Remove the balance arm pivot bracket from the sprue and glue on the backing plate from the kit and when dry cut the backing plate flush with the inside edges of the bracket. Enlarge the hole for the pivot point to 0.03'' and then glue a 0-90 brass nut around the hole centres as a packer.

Using a full length of CMA 0.020'' [0.5 mm] phosphor bronze wire crank one end at 90 degrees x 5 mm then engage with the balance arm and thread the wire through the eye-bolts from the top to allow installation of bracket and balance armFit the balance arm by placing the 5 mm shaft projection into the hole located in the pole to match location of the bracket - slide down the bracket and when aligned apply a drop of liquid adhesive to the bracket and fix the assembly to the face of the pole - check freedom of movement set aside to dry then bend the wire at the attach point at 180 degrees and trim to taste. Do not try to make the loop too tight as the wire will break..!

You can chose to use the counter weight supplied with the kit but it appears a little small and the arm needs weight.

To manufacture the weight four [4] hangers from drills packets were glued together using the end of a paint brush as a mandrel, Remove and coat the inside with ACC and allow to dry. 
The weight is made by melting solder into the hole on a piece of glass. The one in the photos was manufactured from rosin core solder but if you have 90 degree low melt this maybe better.

Remove the weight and using a single cut bastard file remove the miscues until you have a flat disc, file a groove in the back using the side edge of a small flat file then apply ACC to the weight and fit to the arm.

Select the flag type - refer to the diagrams below to clarify usage. Both types are supplied with the Peco kit.

Home IndicationMeaningDistanceIndicationMeaning
STOP Stop.redCAUTION- Proceed the next signal will be a stop.

Begin assembly by mounting the spectacle plate to the arm. On the model a hole was drilled through the flag to suit the tab on the spectacle plate. The tab on the spectacle plate was bent and inserted through the hole and fixed with ACC to provide more strength. Using a razor saw create a groove for the lens material between the arm and the brass etch. Trim one end of the lens material to fit onto the spectacle - apply a bead of ACC then dab lightly with a scrap piece of foam to reduce the glue mass - fit lens material into the groove in the arm and lower onto the back of the spectacle plate.  The joint line to the next lens should lie about the centre of the joint face on the spectacle plate to allow full support for both lens -  repeat for the next colour.

Drill the pivot point in the arm 0.03'' for the pivot and 0.022'' for the actuator wire - drill both actuator attachment points on the flag. There are two balance arms provided - remove the cranked unit and at the point were there are 3 etched holes solder a length of 0.030'' x 25 mm brass wire into the first hole to project about 20 mm from the rear and a  length 0.020'' x 10 to project about 5 mm into the third hole. To do this use a scrap of MDF and using the etch as a guide drill the appropriate hole about 0.005'' oversize about 5 mm into the block - insert wire - lay over the etch - flux and solder. The assembly should now be square and parallel and if not adjust as required. Insert the etch into the arm picking up the pivot point and the unused actuator hole with ACC will provide a strong attachment for the flag - install one of the washers provided with the kit over the attachment point for the actuator [unused hole] and ACC to the back of the etch.

Install the arm pivot bracket - you have a choice of the plastic one supplied or a fabricated assembly. On the model the brass etch was used with  piece of 0.062'' KS brass tube which was soldered into the groove in the etch - it was a little loose but at hand. Glue the arm pivot into position shown and allow to dry. When dry trial fit arm and check operation. When satisfied paint the backside of the arm as access with be difficult when assembled. The area on the post behind the flag can be painted white now for the same reason.

Fix the arm assemble remove the two etches for the lamp back and solder as shown in the photograph. Fit a cardboard V - fit lamp back to pivot with a little flux - adjust as shown and apply a spot of solder - check operation of the assembly.

Manufacture the connect rod from 0.020'' phosphor bronze wire 40 mm long. Form a Z at one end then measure the required length for the rod. Fit a turn-buckle and form the end at 90 degrees.  Thread the Z through the balance arm using the middle hole in the group of 3 and the outer hole in the flag.  This is fiddly and takes time to ensure smooth movement. The packer that was glued to the face of the pole and the formed Z in the balance arm will trap the wire in its correct working location. 

The turn-buckles used are Grandt Line S scale D&RGW narrow gauge and are fixed to the both actuator rods about 1/3 the way up the rod. These must be installed before the final cranks in the rods are added - to fix determine it location and apply a little ACC to the rod and slide one end of the turn-buckle into the glue.

Final Assembly
Decide if the signal is to have a service platform or just a ladder either is correct. To install the service platform drill two 0.020'' hole on the ladder edge of the platform to match the stiles of the ladder. These will be used for the vertical supports that are soldered to the etched ring shown on the Peco plan. Glue a piece of 5/32 styrene angle the back edge of the platform on the underside then fit to the pole using the cast straps as a guide. On the model a scrap piece of 0.050'' wire was used for a knee brace - drill a 0.020'' hole through web of the angle on it centres and trim wire to pick up the inside edge of the frame cast into the platform on the underside. Apply a drop of ACC to both ends and allow to dry. 

The signal assembly is installed onto a 3 mm piece of ply 40 x 55 to allow mounting of the servo. Fabricate a base from 1 mm styrene sheet as shown in photo 48 x 20 mm then glue a 12 x 12 pad to the top. Locate centre and drill 5/32 thru for the wire to pass through. 

Mark the location for the actuator rod and drill 1 mm thru. Glue the completed post onto the base using ACC then fit the ladder to base and platform. Drill holes for the ladder stiles and insert ladder. Adjust the ladder into the base to align one tread with the top side of the platform. Ensure that the actuator rod is not fixed by the ACC.

The finial is now fitted to the top of the pole. Dress square the fit the finial with ACC and allow to dry fully. The finial used was a Model Signal Engineering SC017 and is close to a NSWGR type or contact Kerian Ryan Models and order his KMR031 NSWGR finial. 

LED Lighting and Power Supply
Scrape the enamel wire ends for about 3 mm then tin and repeat for two pieces of 36 gauge wire black and red 75 mm long. Solder to the LED wires to the plug wire by placing parallel to each other then run the soldering iron along length of each too fuse wires together. 

Insulate using liquid insulation available from Jay Car Electronics.

Note: On the LED wire red is negative [black wire] - green positive [red wire].

The lamp light is powered from a ESU 50705 Lighting strip. Remove the two red led supplied with the unit then solder the wires from the signal led onto the pad remembering that red is common [negative] as supplied from TCS. The ESU unit is voltage regulated so any power source up to 15VAC or DC can be used including the DCC bus. The power for the light circuit is delivered by a NCE Switch-it and using a 1 amp zener diode will allow the output to switch the LED light on / off as required in a 24 hour operating session.

Signal Actuator
The signal is actuated using a TAM Valley Singlet. The singlet was chosen for its slow speed, low noise and that TAM Valley provides a DCC accessory decoder which is necessary for future digital signal control.

The TAM Valley servo mount is manufactured from laser cut ply, assembled and is mounted to a 3 mm ply base with a piece of 1/2'' square basswood glued to the back edge. Fit the signal to its base and alight the face of the arm on the servo and glue the servo mount to the base using the 1/2'' block.

It is vital that the assembly drop freely as possible to allow the use of the fine 0.020'' [0.5 mm] wire. Actuation should be in tension with the servo begin the system balance. Adjust the servo movement to the TAM Valley instructions and finally set  its working address. Note: Ensure the servo is allowed to centre itself before trimming the wire.

Consider installing the assembly in such a manner that the whole unit can be removed for service as a complete unit and plugs should be installed for the light and the TAM Valley Servo.

Drawing : To enlarge double click on image


It's  recommend that go to Kerian Ryan Models site to review the notes on the painting and to appreciate the detail provided by that kit and maybe have a go....!

Model Photos