Midget - K-40

Estes Midget K-40
Clone modified for gap staging

This is a clone of the old BT-50 based Estes Midget. The K-40 Midget was originally designed to use the old "S" (short) motors which were basically 1.75" long versions of the standard 18mm motors. The S motors gave way to the "T" motors - 1.75"x13mm - in the early 1970's.

This bashed clone uses the T motors but conforms in all outward appearances to the K-40 dimensions. BT-5 motor tubes were inserted concentric to the K-40's BT-20 motor tubes. Bashes include adding motor hooks in both stages and drilling two 1/8" vent holes into the booster just below the coupler.

My motivation for bashing it this way - besides needing to use the T motors - was easy reloading. The old K-40 configuration required taping the motors together and friction fitting them into the rocket. With the hooks and gap staging, reloading the motors is a snap.

A staging coupler joins the two stages. A piece of 1/4" masking tape at the aft end of the coupler provides just enough friction to ensure upper stage ignition prior to separation.

The booster motor sits about 0.5" aft of its original position. This provides the necessary gap and has no adverse affect on the CP-CG relationship.

4-18-2004