Scratchbuilding a HO Semphore Signal-With Addendum Paul Allard Dana Brown December 10, 2017 Green Mountain Division - NMRA
Background Avoiding cornfield meets on obscure single track mainline. Semaphore signaling solution observed at Dave Sias Layout at Laconia NER convention, 2013
Double Track to Single at Lincoln With dispatcher-less operations, the train entering the tunnel doesn t know what to expect without signal protection.
Research MR article published March 2003 on building a working semaphore signal. Key points: making colored roundels easily mounting the light and blade assemblies adding details such as instrument case, ladders and mileage markers choosing a blade shape
Image of MR Article
Collecting Parts Brass tubing, sheet and U-channel Music wire, screws, Gallery Glass, LED lamp, switch motor mechanism and attachments Detail parts: ladder stock, relay case Misc: tools: soldering iron, solder, small drills and taps, files, nibbler, paints, air brush, modeling hand tools epoxy, solder (silver and regular), Stick-Tak
Key Parts List 3/32 & 5/32 brass tubing.025 brass sheet stock 1/8 U-channel.020 music wire or phosphor bronze wire ladder stock (Tomar #899) instrument case (Alexander Scale Models #3102) 603 surface mount LED with 4 leads (TTX led0603wpk) Misc connectors T-nut, push rod, brass strip
Basic Dimensions We chose the height based on looks on the layout. The signal mast ends up 27 tall from the ground. Prototype signal masts were 17 or higher. Original LED was chosen to be 3mm to fit 5/32 mounting tube. Much smaller 603 ditch light was used.
Mounting Lamp Holder 1/8 U-channel notched for lamp holder and slotted for mounting to mast use higher temperature silver solder
Lamp Holder U-Channel
Lamp Holder Trying 3mm LED in holder
Adding 90 Blade Pivot Mount Make a fixture we eyeballed the alignment and missed. Cut to length and tap hole (2-56 scew without drilling)
Cut Pivot to Length and File Shorten pivot mount to hold screw length File face of lamp holder and pivot screw mount so that blade passes over both without interference.
Blade Design Designed with Autocad or any line editing program with dimensioned lines Printed to Avery Easy Peel Address Labels 1 x 2 5/8 self sticking labels Cut out label and stick to.025 or.030 brass sheet stock. Drill holes before filing. File blade using printed sticker outline.
Blade Build
Blade Build
Blade Assembled to Mast
Add Side Slot for Actuator Wire File carefully to avoid bending mast mast becomes very week after the side material is removed. Remove very little metal at a time. Test end stop motion of blade each time. Bend phosphor bronze wire to engage blade. Drill.025 hole (#72 drill) in blade for wire (we moved this hole to make blade smaller and more realistic) Engage actuator wire with blade and test motion.
Actuator Side Slot
Blade with Actuator Note the moved actuator wire hole. Note finial turned from sprue stock and added to end of cut down mast. Big screw head use smaller round head and 0-80 screws instead of 2-56
Adding Ladder and Brace Tomar #899 brass signal ladder stock Metal straps from an etched brass ladder frame from
Almost Finished
Modify a case by adding 3/32 hole from top to bottom and removing unwanted features. Adding Relay Case
Slide Case onto Mast and Paint
Add Lens to Lamp Holder Microscale Kristal Klear looks like thick white glue. Spread a small blob on the end of a toothpick around the perimeter of the lamp holder opening. The glue will bridge the entire opening. After drying, there will be a transparent clear lens for the light.
Lamp lens
Install Lamp Drill small hole in rear of mast 2 steps #68 hole initially Redrilled hole at 45 degree downward angle with #61 drill to fit both wires from LED through Carefully insert lamp and press in light blocking Stick-Tak putty. After testing lamp, cover putty with epoxy to provide a firm painting surface
Back of Lamp Details
Lamp Performance Testing Very bright 1K dropping resistor with 9V battery. Will test with 2K resistor to make dimmer.
Seal with Epoxy
Finishing the Blade Painted in layers (used paint from personal collection no paint recommendations) Sprayed TTX yellow (Floquil) on front of blade. Didn t mask overspray. Covered yellow blade front and sprayed black (True Scale) over the remainder of the blade and body of signal head. Touched up edge of blade with yellow where black overspray occurred Painted black chevron with micro brush by hand on blade.
Installing Roundels Used Gallery Glass stained glass hobby liquid 3 colors used. It moves away from the center of the lens as it dries, leaving a thinner lens in the middle. Ruby Red #16015 Sunny Yellow #16004 Kelly Green #16008 Placed blade on Saran Wrap covered block of wood Placed 1 small drop of liquid in each roundel hole and let dry for 24 hours. Added another drop of Gallery Glass to each roundel and let dry for 24 hours. Added another drop of Gallery Glass to each roundel and let dry for 24 hours
Blade Painting and Roundels
Adjusting Lamp Brightness
Adding Motor Control Tortoise makes a drive mechanism for semaphore signals and crossing gates about $15 plus a Tortoise motor
Scratchbuilt Tortoise Signal Drive Attach a pivot to the Tortoise body. Add a lever to the pivot and the Tortoise movable throw bar. Connect signal via airplane wire connectors. Use signal throw dimensions to determine location of actuator bar connecting hole.
Per MR Article Oops, doesn t work but the concept is good.
Drive Modifications 60 mil wire instead of 20 mil music wire. Measure end stops precisely since there are not adjustable stops on the Tortoise.
Mounting The Works - Finished
Addendum For producing multiple signals, changes were made in the design as follows: A jig was made to hold the parts in the proper alignment for soldering by one person using tools sold by Micro Mark: Solder pad: 7021M T-pins: #14318 The pivot screw for the blade was reduced from #2-56 threads to #0-80 to make the screw smaller. The pivot screw threaded holder was changed from tubing to 5/32 diameter brass rod (see photos that follow) The geometry of the blade was changed for optimal fit to the new pivot screw/mast assemblies (slight tuning change)
New Blade Pivot Mount Smaller screw in solid brass stock Backside view without screw
Bill of Materials The bill of materials and other notes used in the construction of the prototype (and follow on) signals is contained in a separate Excel spread sheet. A print out of that spread sheet follows.
Item Material Dimensions Comments Signal mast 3/32" brass tubing 4 1/2" long Finial 1/8" plastic rod (or scrap sprue) Turn on drill to fit into mast end and to have a decorative profile. Blade screw mount 3/32" brass tubing 1/4" long 70mil diameter hole (#50 drill) Blade structure.025" brass sheet About 3/4" x 1 1/2" material. It is easier to drill if the material is larger than needed. Cut to size after drilling holes for colored roundels. Signal lamp holder 5/32" brass tubing 1/4" long Signal lamp mounting bracket 1/8" brass U channel 3/8" long 0603 white LED (may substitute warm white) - Tony's Train Exchange Part Signal lamp number led0603w 4-5" leads built in Signal lamp mount light blocker Stick Tak (DAP Blue Stik) Adhesive Putty As needed (tiny amount) Paint surface on light blocking putty on the lamp back side Devcon 5 minute epoxy As needed small amount) Colored spectacle glass Gallery glass stained glass liquid 3 coats, less than 1 drop per coat Signal base instrument case Alexander Scale Models #3102 Signal ladder stock Tomar #899 3 1/2" Strip brass for ladder to mast holder 1/16" wide by 1/32" thick (31mil or thinner) about 1" long cut to fit model 3mm LED fits into tube without the flange falling in. Used a 0603 LED instead of 3mm LED. Use Micro Kristal Klear (by Microscale) to form a clear lens on the blade end of mount. Fill back end with light blocker putty (see below). Fill back end of lamp mount after inserting LED. This holds the LED in place, allowing the wires to exit the back of the mount. Tony's Train Exchange has this. Cover back of putty light blocker with epoxy to provide a surface for paint to adhere. Also used to glue the T-nut to the tortoise switch motor. Red lens: Ruby red #16015 Yellow lens: Sunny Yellow #16004 Green lens: Kelly Green #16008 Cut off post on top and file top and bottom flush. Drill 3/32" hole through the case from the top through the bottom for the signal mast to pass through. Glue case bottom 3 3/4" from the top of mast tube. K&S Precision Sheet Metal #185020 (1/64" x 1/16" x 12" brass strip) - sold by Walthers under part #370-815020
Actuating rod.020 music wire or phosphor bronze wire 6" long Tichy Train Group model #1103 Pushrod connectors Great Planes part number GPMQ3871 Used to clamp actuator wire to tortoise throw rod. T-nut for tortoise pivot #6-32 x 1/4", Everbilt: Home Depot model 802261 Tortoise slow motion switch machine Sold everywhere Throw rod for Tortoise 1/4" strip brass..016" to.030" range Sold at Lowes or mail order from Walthers Misc items: 2-56 black pan head or round head machine screw - for blade pivot 1/4" long Paul Allard changed to 0-80 round head screw to hide the screw better. #6 machine screw - pan head or round head - for tortoise arm pivot 1/4" to 3/8" long Mounting base and screws for under table tortoise actuator mechanism Miscellaneous pieces of wood and screws. Power and wiring for the lamp and tortoise Misc shop materials: silver solder (high temperature) normal solder (low temperature) black paint for blade yellow paint for blade silver paint for mast assembly Tru-Color Black (TCP-010) Floquil TTX Yellow (out of production) Floquil Old Silver (out of production) Special tools: mast hole for lamp wires to pass through at lamp holder #68 drill starter hole, followed by #61 final hole #50 drill for 2-56 screw (3/64" or #56 drill Blade screw hole for 0-80 screw) Blade screw hole tap 2-56 internal thread tap (or 0-80 tap) Blade hole for actuator wire #72 drill (.025" for.020" wire) Blade roundel holes and pivot hole 3/32" drill Metal nibbling tool For cutting excess blade material away Micro Mark sells a nibbling cutter, Item # 81477 Computer printer with label paper For making blade cutting mask pattern Staples: Avery address labels, #5260 Small tubing cutter Small metal files KS 296 (sold by Walthers as 370-296) - down to 1/16" tubing Micro Mark #86849 with rollers instead of plastic friction block (down to 1/8" tubing)