Model Rocket Design Notes

Dimensions

Engines

Type	Diameter	Length	Casing
MicroMaxx	6.3mm	26mm	1mm
Mini	13mm	45mm	1.6mm
18mm	18mm	70mm	2.6mm

Tube	Inside Dim.	Outside Dim.	Length
	mm/in	mm/in	cm/in
MM Stand	4.00 / 0.157	4.50 / 0.177	1.35 / 0.53

Body Tubes

Tube	Inside Dim.	Outside Dim.	Wall	Circumference	Estes OD	ASP OD
	mm/in	mm/in	mm/in	mm/in
T-MM	6.45 / 0.254	7.16 / 0.282	0.355	22.49 / 0.886		7.1
T-10.5	10.72 / 0.422	11.38 / 0.448		35.75 / 1.41
BT-5	13.2 / 0.518	13.8 / 0.544		43.35 / 1.707	13.7	13.7
BT-20	18.0 / 0.710	18.7 / 0.736		58.75 / 2.313
BT-50	24.1 / 0.950	24.8 / 0.976		77.91 / 3.064
BT-55	32.6 / 1.283	33.7 / 1.325		105.87 / 4.168
BT-56	33.1 / 1.304	34.2 / 1.346		107.44 / 4.230
BT-60	40.5 / 1.595	41.6 / 1.637		130.69 / 5.145
BT-80	65.7 / 2.588	66.0 / 2.600		207.35 / 8.163

BT-5 to T-MM downscale is 51.88%.

Electronics

Jolly Logic Altimeter Two

49mm x 18mm x 14.5mm (diameter 23.114mm)
9.9g (0.35oz)

Stability Notes

Stability (CP-CG) should be 1--2 caliber.

Velocity off rod should generally be at least 15 m/s (very rough rule of thumb).

Component Notes

Nosecones

Nosecone plug should be approximately the diameter of the tube.

Couplers

Coupler construction video from Apogee.

Tube couplers should be ~2x the diameter of the tube.

At what power levels?

Fins

Orient grain of balsa wood along leading edge of fins.

Engine Retention

Minimum diameter engine hook

There's a motor retention technique for minimum diameter rockets shown in Tim van Milligan's book that uses a piece of piano wire bent into three sides of a rectangle, two long sides and one short, where the short side goes over part of the bottom of the engine, staying clear of the nozzle of course, and the long sides are buried in fin fillets. I've started using that method on larger than minimum diameter rockets, with the ling sides going through pinholes in the aft centering ring. It seems like that should work nicely for MicroMaxx.

Recovery Systems

Parachutes

Parallel shrouds may prevent tangling:

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Design Notes