Altimeter Bay - Electronics Selection

Designing the altimeter bay on any 38mm minimum diameter rocket is never a simple task. Trying to fit the altimeter, battery, switch, and wiring into such a confined space is both challenging and limiting. Choosing the right altimeter is always the best place to start. I wanted to have an altimeter that could keep up with the performance demands of a supersonic project. I compiled a list of the following needs/wants.

1. Needs a mach delay setting.

2. Has audible reporting.

3. Small enough to fit in the 38mm coupler.

4. Data recording capabilities.

5. Able to opperate at altitdes above 15K.

A brief internet research session yeilded the Perfectflite MAWD altimeter as the best choice. A battery designed for a minimum diameter rocket also removed the bulky 9V battery from the equation.

Altimeter Bay - Switch Design

The only other problem with the altimeter bay(AB) is caused by the one piece airframe design. For the altimeter to work on a switch system the switch itself needed to be internal. I decided to solve this problem with a slap switch that implemented a pull pin system. This setup will be easier to understand from the photos. This is a cool way to arm your electronics on the pad that doesn't take alot of time.

Altimeter Bay - Construction

The actual construction of the AB is pretty basic and strait forward. I used a sled design and incorporated anchor points on both sides of the AB(one for shock chord attachment and the other for a radio transmitter). The last major component in the AB is the ejection canister. A spent 357 magnum casing or shell is a great fit for a 38mm rocket. Shell casings are durable and can take the abuse of multiple charges before replacemnent is required. Attaching the AB to the airframe in a way it can still be removed for reloading charges and altimeter data retrieval is accomplished using 4 small plastic rivots.