Centering ring to mount smaller diameter body tubes or motor mount tubes in tubes of larger diameter, compatible with Public Missiles Ltd.
Fits PT-2.1 or QT-2.1 outer body tube and PT-1.1 or MMT-1.1 inner tubes (motor mount).

Centering rings are mostly used to make engine mounts in model rockets by mounting two of them on a motor mount tube, ang glueing this assembly into the body of the rocket.

Use two of these rings to make a motor mount for a 54 mm rocket with a 29 mm motor. Another common use use is to couple two body tubes of different diameter in order to build various parts of the rocket airframe structure.

Sierrafox centering rings and plates are laser cut from aeronautical-grade birch plywood, compact, rugged and lightweight, with a thickness of 4 mm.

Laser cutting guarantees high measurement accuracy and repeatability. Thanks to this cutting technique, the size of all the rings and discs are perfectly identical to each other, a quality which is not often found in commercial centering rings made with conventional tools.

Although the diameters are accurate, a small tolerance is possible. The tubes themselves have slight differences in diameter than the nominal value. In these cases a little sanding with fine sandpaper is all what is needed to get a perfect fit.

The type of centering ring is identified by a very simple code, easy to read:

First letter: L = LOC compatible, P = Public Missiles compatible
Second two letters: CR = Centering ring
First two digits: the diameter of the outer tube in mm
Last two digits: of the diameter of the inner tube in mm

So, for example, the PCR-7538 ring is a Public Missiles Ltd. compatible centering ring for an outer tube of 75 mm (PT-3.0 or QT-3.0) and an inner tube of 38 mm (PT-1.5 or MMT-1.5)