Public Domain Launch Controller
by Jerry Irvine
In order to advance access to the general public of adequately
powered launch controllers, I am suggesting this plan.
The vast majority of igniters are operated on 6 volt launch systems. A limited number require higher voltages. This plan assumes a 6v power supply, but can very easily be modified to accept any other power supply, including a vastly superior, rechargeable Gel-Cell. However, this system uses a set of four "D" cells for power which is adequate for the vast majority of igniters in use today.
Radio Shack (available worldwide)
SKU -----------Description --------------Price ($US)
270-373 ........PK10 Micro Clips .......1.99 (10)
275-609 ........PK2 SPST Push Sw .....2.79 (2)
270-396 ........4",D Cell Holder..........1.79
61-2745 ........6 ft Brown Extn Cd ......1.99
I had, and you will have to obtain:
2 ........................wire screw caps
10 ......................10-inch lengths of 18-24 gauge stranded leader wire
1 ........................roll electrical tape
1 ........................roll masking tape
1 ........................3-inch length 1/2" dia. electrical conduit
1 ........................20-foot extension cord.
Cut 10-12 inch lengths off both ends of the extension cord. Spread, strip and solder prep all ends.
Solder a SPST switch to one end of the longer middle piece of the former extension cord. Apply electrical tape to the joints to prevent shorting inside the handle (electrical conduit). Remove the retainer bolt and washer.
Slide the free end of the long cord through the electrical conduit tube and handle, until the switch butts against the tube. Wrap masking tape around the switch body until a smug fit is obtained inside the tube. Mark where the wire leaves the tube when the switch is in place against the handle. Wrap masking tape around the wire until a snug fit is obtained inside the tube. Once the wire and switch assembly is in place in the handle, wrap electrical tape while stretching it around the top and bottom ends of the handle to be sure it makes a watertight seal.
Solder one end of the battery cage wires to one end of the switch wire.
Solder the other end of the switch wire to one end of the "female" plug end.
Solder the other end of the female plug end to the remaining battery cage wire.
Solder a 10" length of leader wire to each micro clip.
Attach a micro clip lead to each contact of the stripped wires on the "male" plug end and attach with a screw cap. Wrap a layer of electrical tape to maintain strength. Remove and replace as needed.
Test the system by putting in four "D" cell batteries and attaching an Estes Solar igniter to the clips. Plug in the clip whip into the power plug. This is your safety key. Give a 18.104.22.168.1.0 countdown and fire the igniter by pressing the launch button. The harder you press the higher it goes.
Once successfully tested, wrap all remaining joints with electrical tape and insert a long extension cord between the plugs. You now have a safe distance for live launches. Flight test the system.
The launch button extension affords the ability to stand up while launching for better sighting and allows the freedom to detach yourself from the weight of your power supply unlike many other launch controllers.
One option which is recommended is a relay system going to a much stronger battery at the pad for clustering of high current igniters. This system is adequate to activate that and should give you years of service.
Total cost about US$20.
Homemade Launch Pad
Launch pads are cheap too:
3 wood 2 x 4 x 24 inches, 2 3/8" bolts, 4 inches long 4 3/8"- washers, 2 wing nuts, 1 1/8" x 36" piano wire launch rod, 1 1/4" x 36" piano wire launch rod, 1 1/2" x 60" stainless steel launch rod, 1 short ceramic figurine about 4 inches diameter.
Drill 3/8" holes in the center of two of the logs on the 4 x 24" side.
Drill 3/8" holes on both ends of the remaining log 2 inches from the end and centered along the width.
Arrange the logs in an I-beam shape or capital H shape. Put the two bolts through from the bottom of the two legs through the crossbar on the top. Put washers on bottom and top and screw the wing nut on the top.
Drill holes in the top bar somewhere near the center for 1/2", 1/4" and 1/8" launch rods about 2 inches apart and exactly straight up. Re-drill as needed in new spots to get straight up holes for each size. Drill holes for the 1/8" and 1/4" sizes at intentional 15 degree angles.
Drill a 1/4" hole through the ceramic figurine along its center to slide over the launch rod. Maybe even drill the hole one size larger to make it a loose fit. This is the blast deflector. Use good judgment when selecting which figurine to use as it will reflect your personal style and taste.
Get a larger figurine for the 1/2" rod and drill a 5/8" hole. I like to launch rockets with no blast deflector at all to see how deep a hole is drilled into the wood on each flight.
Tilt the pad into the wind by propping it up from underneath with pieces if 1 x 2 inch wood. If you are foolish enough to launch in gusty wind, secure the pad to the ground by placing piano wire loops over each leg and into the ground. This is also strongly recommended when launching rockets over 4 pounds or with thrust levels over 50 pounds.
Total cost about US$10.
Jerry Irvine - firstname.lastname@example.org
Box 1242, Claremont, CA 91711 USA
Annual copyright notice: All of my posts are copyright 1996 Jerry Irvine and are not to be used for commercial purposes.
The above article(s) originally appeared in rec.models.rockets newsgroup. It's content has been reproduced here by kind permission from Jerry Irvine.
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Last update on 7-Sept-96 - Copyright 1996, Chris Krstanovic (WR1F)