Tommy timer release mechanism

A reliable and fairly easy to construct timer and release mechanism.
There are many different versions for a tommy timer release that can be found on the net, here is mine.
- easy to construct
- robust
- easy to handle

Step 1, main body part: -Cut off the top of a bottle, just below the part with the thread. -Cut off the bottom of the bottle. -Put some tape on the inside of the head, so the hole in the top is more or less sealed. -Shape the top with polyurethane or some other epoxy. -Cut out a section from wall off the bottle ( see picture) This will be the opening from the chute-bay. Height depends on the size of your chute. Width of the cut-out just a little less then half a circumference off the bottle for stability reasons.
Step 2 chute container top and bottom plates: -Cut out two round pieces of wood with same diameter as inside diameter of main body part. Balsa or ply-wood is ok.
Step 3, the chute bay cover flap: -Cut out a section from a bottle that is about 1 cm larger then the gap in your bottle top height. So the part can cover / and overlap the opening in the chute-bay. - Cut the bottle in a straight line from bottom to top. - Shape rest of flap as shown on picture, make sure the widest parts can cover the opening off chute-bay.
Step 4: glue and screw -Glue the two pieces of wood in the inside. Make sure that the rims of the main bottle opening do not overlap the wooden parts. (chute may stick behind these rims). -Mount chute-bay cover flap on one side of bottle main part. -Mount curvature of flap opposing curvature of main body part, so flap can act like a sort of spring. -Add a rubber band on smallest part of flap.
Step 5, tommy timer container: -The tommy timer is a part of many cheap wind-up toys. -Make a timer container from a piece of PET. Make sure that all the spindles can move without obstructions. ( 3 holes in container is for the three spindles on the back of the tommy-timer) -A piece of a connecting block (Dutch=kroonsteen) is cut in half. (used as hook for the rubber band).
Step 6:assembly and paint -Sand the polyurethane to get a smooth shaped surface. -You can use paper cut-outs to check for top line curvature. (if you go for optimum aerodynamic shape). -Mount tommy timer in its housing. -Attach parachute to chute-bay cover, attach it on the flap so that the chute is pulled out at release ( right hand side of chute-bay.
Step 7, does it work?: -Test the assembly. -Determine the amount of wind-up that is needed for your desired release time. -At pre-launch the timer is kept in wound position by means of a clothes pin attached to the ground. (see launch section for examples)