Hiness Two-Stroke Radial


Created: June 2005

Name Two-Stroke Radial Manufacturer Inamura Co. Ltd.
Type Glowplug Ignition Capacity .60 cuin
Production run unknown Country of Origin Japan
Photo by David Owen Year of manufacture circa 1975



Commercial model radial engines were once quite rare, but are becomming more plentiful. I believe the reason for this has been the progress in manufacturing techniques that has made model-sized four-strokes commercially viable, and desirable in the modelling community--especially those with deep pockets. Discounting the Morton M5 (a four-stroke) as a market aboration, there have been very few two-stroke radials to reach commercial production, and even those never reached very high volume. All this is good for the collectors of today, and provides some introduction to the Hiness 3 Cylinder two-stroke radial. The engine pictured here is from the collection of Mr David Owen, and David has kindly provided the words that describe it.

This is a big engine with a bore of 16.10mm and a stroke 16.35mm, giving a total swept volume of 9.98cc. It is fully machined from bar stock with no castings being used. Over all diameter is 132mm, and the length from mounting face to rear of prop is 108mm. The cylinder fins are 39mm dia. The 10mm dia exhaust pipes are 100mm long. The 3-point mounting system uses 6mm hex head cap screws. Overall mass is 954g. The engine is built around a triangulated crankcase.

The front housing carries two ballraces and the rear housing one ballrace. In addition to supporting the rear of the crankshaft, the rear housing mounts the air-bleed throttle assembly. The long, one-piece, hardened and ground crankshaft is supported in three ballraces, the rear section of the shaft forming a crankshaft rotary valve. There are three throws at 120 degree spacing, giving simultaneous firing. The alloy conrods have split big-ends, the caps being retained by 1.5mm cap screws. The centre rod is symmetrical, whilst the front and rear rods have considerable offset at the little end. Tubular wrist pins with brass end pads are used.

The cylinder sleeves are unhardened steel, whilst the very thin and lightweight baffled pistons appear to be hard-chromed. The finned alloy cylinder jackets have milled transfer passages and the cylinder sleeves feature simple loop-scavenged porting. Each cylinder assembly is fixed to the foundation crankcase with four long 8x32 screws. Each cylinder jacket has a tubular exhaust collector (fitted with two small screws) into which the long exhaust pipe is screwed with a very fine pitch thread. One exhaust collector is fitted with a pressure tap.

The whole engine is beautifully machined, with superb indexing of components. No gaskets are used in assembly. All external parts are polished. The Hiness turns over very smoothly, with no hint of drag or binding and feels just like a large single cylinder engine when flipped. This particular engine has been test-run only at the factory. It was supplied in a large, varnished wooden box which has a carrying handle. The box is inscribed:

Hiness "Hand-made Model Engine". Work No. 043




Please submit all questions and comments to enquiries@modelenginenews.org