Hints & Tips
DIY - Bungee Pedal
By Carl Tulanko
October 02, 2007 - 08:24:28 PM

A simple Bungee Pedal launcher can be made for parts readily available at your local hardware store such as Lowes or Home Depot. Nearly all the parts are shown	Required hardware includes the Spring Hinges as shown, Stainless Steel rustproof harware for the bolts to include three 8-32 x 1" countersink bolts, three 8-32 nylock nuts, a 1/4" x 2 1/2" bolt, a 1/4" "T" nut, a 1/4" fender washer (not shown) and a 1/4" nut. In addition, a 1" chrome ring, a piece of 3/4" x 1 1/2" long heat shrink (not shown) and some 3mm nylon cord round off the necessary supplies	The pedal is made from a single 24" long piece of hardwood, in this case we used Oak. It is a 1/2 x 3 that is 2' long
Construction begins with the wood piece. Make a mark 11" from one end of the oak board	Draw a vertical line at the 11" mark	Use a saw to cut the board into two pieces. One will be 11" long and one will be around 13" long
USe a small 1/2" diameter cap or coin to draw a 1/4 round at the corners of each board	Use a sander or block to round the corners as shown	Slightly round the edges on each board to prevent splintering
Fine sand both boards, top, bottom ends and sides	Make a mark on the long board at 5 7/8" from one end	Draw a vertical line using a ruler or square at this mark
Center the hinge's two inside holes over the mark with the hinge positioned as shown, mounting side of the hinge to the right and the 5 7/8" side of the board to the left. Draw circles in the hinge holes to transfer their location to the wood. IMPORTANT: Make sure the spring is positioned perpendicular at the location	Use a punch to mark the hole locations	Drill only the two end holes with a 5/32" drill. A drill press is recommended to keep the holes straight and centered
You need to open up the holes a bit for the 8-32 bolts, using the drill as shown	Install the two end bolts	Check once again that the spring is vertical. If not, you can slightly elongate one of the holes to straighten the hinge

Keep the hinge straight and drill the center hole	The holes can be countersunk on the bottom for the bolts	Install the bolts in each hole
Use nuts to hold the hinge in place and centered	Place the short piece over the long board, with the end flush as shown on the measured side (the 5 7/8" marked side)	Use a tie wrap to temporarily secure the end of the boards
Flip an hold the hinge up, then set the short board over it and while holding it together, use another tie wrap to keep it in place. Align the end of the two boards flush and keep the sides of each board even with eachother, then transfer the hinge location to the short board, outlining it with a pencil	Remove the short board by cutting the tie wraps and be careful of the rebounding spring hinge. Remove the hinge from the long board and place the correct short board side over the drawing	Make a mark at each hole location

Mark each location center with a punch

A small 3/32" hole is drilled at each screw location. The drill is set so it does not go all the way through the wood, leaving the last 1/16" or so undrilled. This will keep the top of the board looking clean

Make a mark on the end of the long board, at the short 5 7/8" side. The mark is 1 1/4" from the end

Draw a center line over the mark you just made	Use a punch to mark the location	Drill a 1/4" hole at the center. If you wish to countersink the location of the "T" nut, then use a 3/4" forstner and cut about 1/16" deep at the center bottom of the board. Make sure you countersink the bottom side
Open the hole to the width of your 1/4" "T" nut, which may be around 5/16" - 3/8" depending on the "T" nut you purchase	Transfer the location of the 1/4" hole from the long board to the short board. Make sure you mark the correct end of the short board	Use a 5/8" Forstner to bore a hole in the short board at the location you marked
On the opposite end of the long board, make two marks at 1 3/4" from the end as shown	Measure in 5/8" from one side of the board to make the cross mark	Make another mark 5/8" from the other side of the long board

Use a punch to mark the first location for drilling

Use the punch to finish marking the second location

A 5/32" drill is used to bore a hole through the long board at each of the locations you marked

Use a hobby knife and sandpaper to slightly round the exit areas of each hole on both the top and bottom of the board. This is so there are not any sharp edges to cut into the nylon cord

Both boards have been prepared, drilled and sanded and are ready for assembly

Mark the 1/4" bolt 2 1/8" from the threaded end. Note that Stainless Steel hardware was used in the assembly to prevent rusting

Cut the head off the bolt at the mark as shown

Grind and sand the cut area to round it

Hammer the "T" nut into the bottom of the long board until it is flush

Install the large fender washer, then the lock washer and nut over the bolt/pin as shown. Screw the bolt pin into the "T" nut

Use a wrench to tighten the bolt pin

Place a screw included in the pack of hinges along the side of the short board. Mark each screw to be cut so they will just be clear of punching through the top of the board

Cut each screw to shorten them and check the length so they are shorter than the board thickness

Install the hinge using the screws you just cut. Tighten them down all the way and keep the hinge spring centered

Slide a ruler under the hinge to assist with the next step to install the long board

Install the three 8-32 bolts through the bottom of the long board

Position both boards, and while holding the spring, install the long board so its bolts run through the hinge

Hold the pieces together and start the nylock nuts as shown, holding them with one hand while turning the screwdriver with the other hand

Photo shows nylock nuts in position

Make sure the two boards are lined up with eachother and then tighten all three bolts

With the bolts tightened and the boards centered, the 1/4" bolt pin should be centered in the hole as shown

When depressed, the pedal lifts up and the hole should clear the pin by about 1/4"

Cut a piece of 3/4" heatshrink to a length of 1 1/2"

Cut a piece of the 3.2mm nylon cord to a length of at least 26"

Use a lighter to melt and seal each end, which will keep the cord from fraying	Install the cord in one of the two rear holes from the top	Loop the cord from the bottom to the second hole and thread back through
From the top, pull each cord and adjust until they are the same length	Slide the heatshrink over both cords, then slide the 1" chrome ring over both cords	Fold the cord ends over and tie them in a knot as shown, passing the ring through the cord loops

Pull and tighten the knot so it is tight. You can dab it if you wish with a bit of epoxy

Cut some of the excess off the ends, leaving about 1/2" exposed. Re-seal them with a lighter to prevent fraying

Stretch and slide the heat shrink over the knot as shown

Use a heat gun to seal the knot

You can add a thin layer of epoxy to the bottom of the long board to waterproof it from the ground during use

The completed pedal assembly is shown. The aircraft release loop is placed over the 1/4" pin

When depressed, the pedal pushes the release loop off the pin

A 12" galvanized nail with a matching fender washer can be installed through the chrome ring and is used to stake down the rear of the pedal. This completes the assembly of the Bungee Release Pedal