There are a number of cut down methods availble : Hot Wire/Resistor, Pyro and Magnetic.

Pros :

• Low power use.
• Light.
• Very fast.

Cons :

• Explosive - duh.

TAKE CARE WITH THESE WEAR SUITABLE EYE PROTECTION

You're all clever people but these blow up with some force. Take precautions.

The pyro cut down is fairly easy to construct using some acrylic tube of the following dimensions :

External Diameter: 10mm Internal Diameter: 6mm Wall Thickness: 2mm

Other items you need are some Estes D-ES2301 rocket motor igniters, transparent epoxy resin, smokeless powder. Rob Harrison has prepared a series of pictures here : Construction of Pyros

In practice you can replace the smokeless powder with the head of some matches scraped off and crushed down.

Match Stick Pyro
Gun Powder Pyro

Pros :

• Safe.

Cons :

• Can be slow.
• Can use alot of power.
• Can be mechanically fragile.

Pros :

• Safe.
• Fast

Cons :

• Can use alot of power ?
• Heavier than pyro/hot wire ?

Magnetic cutdown