Rex-06 left side Rex-06 top view Rex-06 right side

Rex-06 with replacement spinner and APC 6x2 prop. A bent wire flood-off valve has been installed in the integral lug.

Front view showing the replacement spinner and prop driver.

Rex-06 with standard spinner and folding prop.

This is a Ukrainian engine made by Alexander Maximov. All the required Free Flight plumbing is pre-fitted. This includes a pressure tap in the backplate, flood-off inlet and a steel brake drum on the prop driver, though the brake spring is not supplied. The brake housing is integral with the crank case casting.

It is a well made engine using ABC technology. It has three transfer passages in a typical Schnurle rear exhaust setup. The bore is 11.0 mm and stroke 10.0 mm. It uses a Nelson plug, which screws into a one piece head. This can be shimmed for compression adjustment, though no shims are supplied, and is retained by five Allen head bolts. The bottom of the head forms the squish band. The inner edges of this are chamfered at 45 degrees and meet the base of the plug at its outer edge to form the combustion chamber.

The engine, when equipped as shown with a spinner nut (see below) and with the backplate replaced by a Galbreath radial mount adapter, weighs 97.3g. The spinner nut is 3.5g heavier than the standard spinner and the Galbreath mount adapter is about 2g heavier than a standard backplate, so the engine in standard trim would weigh around 92g, somewhat heavier than most of its rivals.

The mounting lugs are machined flat on their under surfaces and taper in width, with the rear being the widest. The minimum bearer spacing is 21.2 mm, with a maximum width over the lugs of 32 mm. There are four 2.2 mm diameter mounting holes drilled in the lugs. These are spaced 25.5 mm apart laterally and are 11 mm apart in each lug.

NOTE: that the head cannot be removed without damage unless the plug is taken out first. The plug is intentionally tight in the soft alloy head and the act of screwing it in expands the head to prevent top end leaks.

Alexander sells a folding 145 x 70 mm (5.7" x 2.75") prop for this engine, which in turn is designed on the assumption that his prop will be used with it. The 21 mm prop driver uses a collet to mate it to the crankshaft and is milled to accept the folding prop hub. It has no knurling or other method of securely driving any other prop. The spinner is pre-cut to fit the hub. At 24 mm long the spinner is too small to accommodate a larger propeller hub and prop nut, so use of an APC prop is incompatible with this prop driver and spinner. In consequence I had a replacement reduced diameter prop driver and a traditional solid bullet shaped spinner, 18mm diameter and 20mm long, made up for use with the APC 6x2 propeller. It is tapped with an M5 thread to match the crank shaft. This works very well, not least because its fatter shape is more suited to use with an electric starter.

Rex-06 head detail Rex-06 prop driver detail

Underside of the head showing the squish band and combustion chamber.

Props and standard prop driver / spinner. An APC prop (top) will not fit in the spinner. Note also the prop driver rebate. This engages positively with the folding prop hub (bottom).

My example, which cost $130 in 1995, turns 27,400 on an APC 6x2. The folding prop cost $30.00 in 1997.

These engines can be obtained directly from:

Alexander Maximov,
Staritskogo str, Apt. 2,
310018 KHARKOV,