Type Half Alternator

Rev - Nov 26, 2017

By Jan Zumwalt (EAA #66327)


See Also

Half VW media
Half VW Alternator Circuits
DIY Flywheel Dynamo
DIY Pulley Dynamo
For additional pertinent VW information on this topic see VW Type 1 & 2 Alternator.


Electricity is produced when you pass a coil of wire through a magnetic field... or pass the magnetic field through the coil of wire. If you wish to convert mechanical energy into electrical energy using rotary motion the output will be a sine wave -- alternating current.

The generic term for such devices is 'dynamo.' The terms 'alternator' and 'generator' are used as a handy means of defining which type of dynamo is being used. In the generator the magnetic field is fixed and the coil(s) rotates through it. The output is an alternating current that is converted to pulsating direct current through the use of a mechanical switching system mounted on the shaft supporting the coil (ie, carbon brushes and a segmented commutator). In an alternator the magnetic field rotates while the coil(s) remains fixed. The alternating current that appears in the coil(s) is converted to direct current by a rectifier.

The key points here are that 'alternators' and 'generators' are both dynamos. Each uses brushes. Each has a magnetic field and regulates its output by controlling that field. Since the advent of solid- state rectifiers, alternators have come into general use because they are less expensive to manufacture but they aren't really new. The Leese-Nevil alternator using copper oxide rectifiers has been available since 1921. Nor are permanent magnet dynamos 'new' in that they've been around in the form of magnetos since the 1890's. The reason we're seeing more of them nowadays is a reflection of economies of scale in the production of rare-earth magnets.

The output of any dynamo is a function of its rpm, the number of pick- up coils and the intensity of the magnetic field. The most common means of controlling the output of your dynamo is to control the intensity of the magnetic field by regulating the amount of current that flows through the magnetic field winding. If a variable output is not required you may replace the magnetic field winding with permanent magnets.

Usually generators are heavier than alternators. For that reason, most aircraft were switched from generator to alternator cicruits by 1970. By controling and energizing the field voltage of an alternator, it can be made to start producing usable voltage between 800-1200rpm. Most generators will not producce usable voltage until 1500-2000rpm.

Honda 125 Alternator (10amp)

There are many commercial and home made dynamo/alternator options available. Perhaps the lightest and easist is to modify an existing product. Motorcycle engines are ideal candidates because they share the common goals of needing to be compact and light weight. The diagram below is a proven design that has been used on many aircraft from the 1970's and is one of the lightest installations available. New stator and rotor can be found on Ebay for under $100.

How to install a Honda 125 aletrnator (10A~150W)

Tractor or RC Plane Motor/Generator

A very quick and simple alternator/generator can be made from lawn tractor, or small farm tractor alternators or RC airplane electric motors.

E-Flite Power 110 Brushless Outrunner Motor


John Deer and Kubota G3200 light weight alternators

A parts search can be made for garden or farm equipment such as the Kubota Agricultural equipment.

Excavators Diesel
2000 K008 D722 10HP
2000 K008-3 D722EBH-3 10HP
1989 - 1993 KH007 Z430-K1 8.5HP
1985 KH35 D850BH 13.7HP
1988 KH41 D950 17.8HP
1988 KH61 D950BH 22.2HP

Tractors - Compact Diesel
1988 - 1996 B1550D D850-5B 17HP
1988 - 1996 B1550E D850-5B 17HP
1990 - 1998 B20 D950AT 20HP
1990 - 1998 B20TL D950AT 20HP
1983 - 1996 B5200DT D750 13HP
1983 - 1995 B5200E D750 13HP
1983 - 1994 B6200DT D850-5B 15HP
1983 - 1994 B6200E D850-5B 15HP
1983 - 1994 B6200HSD D850-5B 15HP
1983 - 1994 B6200HSDT D850-5B 15HP
1983 - 1994 B6200HSE D850-5B 15HP
1983 - 1994 B6200HST D850-5B 15HP
1983 - 1994 B6200T D850-5B 15HP
2005 B7410DT-F D782-E 18HP
2005 B7410DT-R D782-E 18HP
1981 - 1990 B8200DT D950 19HP
1981 - 1990 B8200E D950 19HP
1983 - 1990 B8200HSD D950 19HP
1983 - 1990 B8200HSE D950 19HP
1983 - 1990 B8200HST D950 19HP
1987 - 1990 B9200DT V1200-A 22.5HP
1987 - 1990 B9200E V1200-A 22.5HP
1987 - 1990 B9200HSD V1200-A 22.5HP
1987 - 1990 B9200HSE V1200-A 22.5HP

Tractors - Garden
1989 - 1995 G1800 D662 16HP Diesel
1989 - 1995 G1800S D662 16HP Diesel
1989 - 1995 G1900 D722 18HP Diesel
1989 - 1995 G2000 WG750-G 21HP Gas
1983 - 1990 G3200 Z400 10HP Diesel
1984 - 1990 G4200H Z430 12HP Diesel
1984 - 1990 G5200H D600 14HP Diesel
1986 - 1990 Garden G6200H D640 16HP Diesel

Tractors - Sub Compact Diesel
2003 BX1500D Z602E
2001 - 2003 BX1800D D722E-BX 18HP
2004 - 2006 BX1830D D722E-BX 18HP
2002 - 2003 BX22 D905E-BX 22HP
2001 - 2003 BX2200D D905E-BX 22HP
2004 - 2006 BX2230D D902E-BX 22HP
2004 - 2005 BX23LB D905E-BX 22HP