Dolly Bungee Launcher Build Instructions

2 - A 3/16" piece of steel rod from the hobby shop is used for an axle. It is marked for cutting at 13 1/2" in length 3 - The rod is shown being cut and the ends are then flattened 4 - The rod is cleaned with very fine sandpaper, followed by alcohol CG. 5 - Most wheels have 5/32" axle holes, so I used a spare pair of 2 3/4" lightweight wheels and drilled them to 3/16" diameter to fit the axle 6 - You may have to sand/file the hole so it spins smoothly and without play on the shaft rod you made 7 - Loktite is used to install the set screws in six 3/16" wheel collars that are used 8 - Set screw shown installed in wheel collar 9 - Clean up the excess Loktite with a Q-Tip 10 - The first Wheel is installed and the Wheel Collar is tightened flush to the shaft 11 - A second wheel collar is installed to hold the wheel in position. Make sure the inside wheel collar is not binding so the wheel can spin freely 12 - 1/16" braided steel cable is purchased from Home Depot, Lowes or any other similar store. You will need about three feet of cable 13 - Aluminum Ferrels are also purchased for the wire. You will need three of them and they come two to a pack 14 - The first ferrel is placed over the wire end 15 - The wire is looped around and inserted into the other side of the ferrel 16 - The wire is pulled tight so that the loop can just fit over the 3/16" axle shaft 17 - Once crimped, you can solder the wire together for additional safety 18 - Wire shown crimped and soldered 19 - I used the side of a steel ruler to flatten the center of the ferrel and crimp it as shown 20 - Photo shows a closeup of the crimp 21 - A second ferrel is slid over the wire, then loosely looped back 22 - A third ferrel is slipped over the other end of the cable and the wire is passed through to make a large loop 23 - The center ferrel is shown in the photo on the left with the space between the two ferrels measured as seen 24 - The center Ferrel is also adjusted so a 1" loop extends past it as shown below 25 - Masking tape is used to hold the center loop and wires in position. Do not crip the center yet 26 - The third end ferrel is adjusted over the wire to the same space of 12" between it and the center ferrel 27 - The end is adjusted to fit over the 3/16" shaft, then it is crimped in place 28 - The other end ferrel shown crimped and the wires have been soldered 29 - Both ends shown even to eachother with similar sized loops 30 - Tape is removed from the center ferrel and it is slid up the wire to form a 1" long loop 31 - keep the two end loops together so the center loop is not made lobsided, then crimp the center ferrel as shown 32 - Wire completed with two ends and a center loop 33 - Once the wing set, use extra epoxy to fill any small gaps. One of the loops is slid over the shaft 34 - The wire loop is tightly retained with another Wheel Collar 35 - Two pieces of 3/16" inside diameter brass tube are cut to about 1/2" in length 36 - The tube is slid over the shaft 37 - Both brass tubes are installed on the shaft 38 - Slide another wheel collar on the shaft 39 - The other wire end is installed on the shaft 40 - Another wheel collar is loosely installed as shown 41 - The second wheel is installed on the shaft 42 - The final wheel collar is installed and tightened flush to the shaft end 43 - The inside wheel collar is tightened against the wheel, but make sure it can spin freely. Finally, tighten the inside wheel collar tight against the wire loop 44 - Once the inside wheel collars are tightened, remove the one outside collar and wheel 45 - The right wheel was removed so could more easily measure the distance between the two inside wheel collars. The distance is shown below as 10 1/2" 46 - Make a center line using a marker at half the distance between the two collars, in this case 5 1/4" 47 - Push the brass tube up against your mark, tape it in place so it doesn't move around and draw a full circle around the center line 48 - With both brass tubes pushed to the right of center, epoxy is applied to the shaft on the left side of the center mark 49 - The brass tube is slid past center and over the epoxy, then the excess epoxy is cleaned. Glue is applied to the right and the right side tube is slid over the glue back and forth until it fills inside, then the excess epoxy is removed from the right side tube 50 - Position the two brass tubes evenly on each side of the center line with about a 3/16" thick space between them as shown. Let the epoxy set up 51 - Bungee Dolly shown completed and ready to use 52 - The dolly should hang centered 53 - A 25-30' length of 1/8" wall x 1/2" bungee and stakes to secure the line are required for the assembly 54 - The dolly bungee system is shown 55 - A bungee release pedal is required and is covered in another build 56 - The towhook of the aircraft is hooked at the center of the Dolly axle, between the two brass tubes. The front loop of the Dolly is attached to the bungee cord using a 1/8" Quick Link 57 - The pedal is connected at the rear 58 - The bungee system shown hooked up to an aircraft. This completes the construction of a Dolly Bungee Launcher System This Website and all documents herin are Copyright © 2012 www.scalerocketry.com - All rights reserved.