Project: Blade Runner
Part Two, Assembly.
By Richard A. Coyle
In Part One I outlined all of the modifications needed to create the masters for this intricate model.
Those of you who have done some prop casting will realize that I have left out many details about mold making, such as positioning of pour points and air vents, parting lines, etc.
The thrust of this initial article series is to relate the making of the blaster model from a research, engineering, and fabrication standpoint. To properly cover all of these basic mold making details could take as many pages as the first two articles combined. Besides, it is a well covered subject in many other sources, so I have decided to gloss over it here.
Perhaps some time in the near future I will do an article series on making molds and casts in the context of creating this type of model.
Meanwhile, back to our saga:
With the new molds ready, I cast an initial run of four sets of every component. This was to insure that I would finish with at least two completed models, one for Phil and one for me, with a selection of spare parts from whatever was left over.
After casting the raw parts, all flash is trimmed (the little extra plastic “lip” that typically finds its way into the parting lines of a mold), and all pour points and vents are dressed.
Next, all of the various holes must be drilled, and those that will have screws used to fasten parts are tapped to the appropriate thread.
Each model is then sanded with 300 grit sand paper, followed by 400 grit, and finally red Scotch-Brite® pads to a smooth finish.
I test fit the grips and sand them to fit.
The models can now be “dry assembled” to check for proper fit and any correction requirements. Any problems are fixed and the parts refitted.
Once I am satisfied that everything fits and functions well, all of the components are disassembled and mounted on wooden posts for painting.
Each and every part gets a base coat of primer, two to three coats of enamel in the appropriate color, and then three finish coats of clear enamel.
Turning to the lathe, I then section two brass rods to make the trigger pins, a piece of brass tubing for the hammer pin, five pieces of brass tubing for the cylinder rod, and one piece of brass tubing for the hammer spring assembly for each model. The small knob on the side cover, as well as the main body and end of the side rods, are then center drilled with the lathe. The next part to be machined is the cylinder, which first necessitated making a set of soft jaws to perform the lathe work without damaging the parts. Once chucked, I face off the bearing surface, leaving a small, raised washer-like projection on the front end of each cylinder.
The next step was to turn down an aluminum tube to the same outside diameter of the bolt, and then bore it to the inside diameter of the bolt’s necked-down end to provide for the rotation inside the receiver.
Again using the lathe, I turn down the ends of a 3/4-inch acrylic tube for the barrel and then crown the business end to reproduce a true gun barrel appearance.
The barrel also gets a full painting run, plus one extra coat and a couple of coats to the inside of the barrel.
Switching to the mill setup, three holes are drilled for the screws that mount the Steyr receiver and the ammo housing to the model. A flat cut must then be milled near the housing end of the barrel by the Bulldog’s frame so that the barrel will clear the cylinder’s rod.
Next on the milling setup, the aluminum tube made for the bolt is milled by cutting off a section to make a C-shaped part; then with a special jig made to hold this new part, I mill a slot in it for the sliding travel groove. Finally, a hole is drilled and deeply countersunk to facilitate mounting of the cocking lever.
For the hammer, the small lever return spring hole must be drilled by hand, and then the spring, lever, and retaining pin are installed. The hammer can then be pinned into the Bulldog frame using the special piece of brass tubing fabricated for this purpose .
For the trigger, the return spring hole must also be drilled by hand, after which the spring is installed, and then the assembly is mounted into the frame with its retaining pin.
Next I install the pistol grip frame by fastening it with four screws — two per side.
With the primary trigger and grip frame in place, the trigger guard can be installed into its rear capture slot and then fastened with the cylinder swing arm to the frame. A 4/40 Allen screw is used to hold both.
I then assemble the hammer spring assembly. The ball end is mounted onto 4/40 threaded rod, which is cut to length, sheathed with a pre-cut brass tube, fitted with the return spring, and fastened together with a washer and 4/44 nut.
The hammer spring assembly is then installed into the pistol frame and seated to properly engage the hammer.
I test fire the weapon a few times to make sure it works properly. The front trigger is then installed with its brass retaining pin.
Taking the tubing previously parted with the lathe, I solder these parts together to form the cylinder’s locking rod. Slipping on the cylinder’s swing arm and spring, I then solder a small piece of tubing onto the assembly to hold the spring and arm together. A quick trip to the belt sander results in smooth, beveled joints.
After cutting a 3/4-inch length of 1/2-inch OD aluminum tubing to create a barrel mount, I insert it into the Bulldog’s fame and then slide and glue the barrel onto it.
Next, a 6/32 button head Allen screw is cut to length and threaded into the tapped front scope mounting hole of the Steyr receiver in order to form the front sight, exactly like the original prop. The three remaining scope screw holes of the Steyr are plugged with slotted set screws, again to match the original. One of these is a special screw — slightly longer to allow it to lock into the bolt’s slot at the top for rotational travel control.
The tiny tip-like projection of the Steyr receiver end cap is then glued into place, followed by insertion and gluing of the cap itself to plug the opening of the receiver above the Bulldog barrel.
Using a small flat head 4/40 screw, the bolt cocking lever is fastened to the C-shaped tube, which is then installed onto the bolt and fastened together with a 4/40 Allen screw.
The bolt assembly is then inserted into the receiver, and the longer set screw in the Steyr receiver is screwed in to engage the travel slot in the top of the bolt.
Next, the entire Steyr receiver assembly is slid onto the bars cast into the Bulldog’s frame using the slot and rail mounts. The assembly is then fastened to the Bulldog barrel at the front using two 4/40 Allen screws inserted through the milled notches in the receiver.
The right side cover can be mounted at this point. I designed this cover to lock onto the side of the Steyr receiver near the cocking lever slot as a way to reinforce and support the receiver assembly. This seemed an important consideration, because once the machine work was completed to allow mounting onto the Bulldog frame, only a short, small piece of plastic below the cocking lever slot, weakening the receiver casting below and rearward of the lever where the Steyr safety switch mounts.
For attachment of the right side knob, I thread a short piece of 4/40 rod into the knob and then mount this to the front edge of the right side cover into a previously prepared hole.
As described earlier, the front screw head is now a casting that must have a short piece of 4/40 threaded rod glued into. This allows threading into the boss made for actual mounting to the Bulldog’s frame.
Once the cover is fitted and the cocking lever and bolt action satisfactorily tested, I can finally mount the Steyr bolt cap casting using a small 4/40 button head Allen screw exactly like the original prop.
The cylinder is then mounted to the swing arm for final assembly. To give the model actual rounds for the cylinder, I manufactured “safe” ammo by pressing hollow point bullets into primerless cartridges. These rounds are now loaded into the cylinder, which is swung closed to engage the locking rod into the Bulldog frame. Things are really shaping up at this point.
To mount the side rod, its knurled end cap is first glued on, and then the entire rod is glued to the left side cover. The left side cover with the rod can now be mounted directly onto the swing arm with two 4/40 Allen screws
To prepare the ammo clip, four red LEDs are installed, and their leads are soldered together. In order to provide an adequate power supply, I trim an “N” type battery holder to take the larger 7-volt battery that was selected, wire up the assembly, and then glue it into the magazine.
Moving our focus to the ammo housing, the DIP micro switch must be mounted inside next. The switch is then wired to the ammo clip, and installing a battery to test the electronics, I then snap the ammo clip into the housing and mount the assembly to the gun frame with one small Allen screw on the right side (just like the original, of course).
One larger 8/32 screw is also used, 
which is installed though a specially cut and trimmed tube to the front underside of the gun barrel.
The Bulldog’s cylinder release knob is now mounted to the left side of the frame with a small screw.
The next to last step is to mount the two pistol grips on the frame with four 4/40 Allen screws.
And last to mount the pistol grip butt plate with two 6/36 Allen headed screws to the bottom of the frame.
And there you have it, blade runners: the completed, fully detailed and functional blaster model ready to wreak havoc on all replicants!
