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Overview of electric flight
Symposium by Keith Shaw
Public Newsletter Articles
How to rebuild an Astro motor
Weight reductions for electric conversions
A low cost thermal peak detection charger
Making Printed Circuit Boards
Aerobatics for Electric Airplanes
Nicad Care and Handling
The Shuttle ZXX
Getting the Most Out of Ferrite Motors
What Difference Does A Bit of Wire Make Anyway?
Using 1100AAU Cells for the Speed 400
"Squirrel" - Construction - Speed 400
A Weight Comparison of some Lightweight Coverings
Motor Comparison
Keith Shaw on Props
Building Foam Models
Electric Flight Box
MOTORS - Cheap, Light, Powerful. You Canít Have It All
by Stefan Vorkoetter

 
Ferrite "Can"
Ferrite Car
Cobalt/Neo
Brushless
Cost Low cost - $10..$30 Medium cost - $20..$50 High cost - $125..$600 Very high cost $400 +
Quality - Low quality
- Brass bushings
- Carbon brushes on leaf springs
- Cheap ferrite magnets
- Large armature-magnet gap
- Medium quality
- Bushings or ball bearings
- Copper or silver brushes
- Brush holders and separate springs
- Better ferrite magnets
- Some have adjustable timing
- High quality
- Ball bearings
- Thicker output shafts
- Large brushes (usually silver)
- Brush holders and separate springs
- Powerful cobalt or neodym magnets
- Adjustable timing
- High quality
- Ball bearings
- Thick output shafts
- No brushes
- Powerful cobalt or neodym magnets
- Adjustable or self-adjusting timing
Weight Heavy (~2.3lb/HP) Heavy (~2.3lb/HP) Light (~1.5lb/HP) Very light (~0.5 to 1.2lb/HP)
Efficiency - Narrow efficiency curve
- Maximum efficiency about 70%
- Typically about 60%
- Narrow efficiency curve
- Maximum efficiency about 75%
- Typically about 65%
- Wide efficiency curve
- Maximum efficiency about 80%
- Typically about 70%
- Wide efficiency curve
- Maximum efficiency about 85%
- Typically about 75%
Power - Maximum power at about 50% efficiency
- About 140W out for a 7oz motor
- Maximum power at about 55% efficiency
- About 140W out for a 7oz motor
- Maximum power at about 60% efficiency
- About 220W out for a 7oz motor
- Maximum power at about 65% efficiency
- About 280W out for a 7oz motor
Advantages - Cheap!
- Readily available
- Can often be found surplus
- Wide range of sizes
- Low cost is great for multi-motor models
- Fairly inexpensive
- Readily available
- Brushes replaceable
- Some have ball bearings
- More efficient than "cans"
- Brushes replaceable
- Ball bearings for long life
- More efficient than car motors
- Low maintenance
- Wide voltage and current range
- Zero maintenance
- Ball bearings for long life
- More efficient than brushed motors
- Very wide voltage and current range
Disadvantages - Difficult to maintain
- Brushes not replaceable
- Loses power at high temperatures
- Difficult to find specifications
- Limited selection of sizes
- Fairly expensive
- Harder to get

 
- Very expensive
- Requires special speed control
- Not usually in stores
Examples - Graupner Speed 400, 600, 700
- Great Planes Goldfire and Thrustmaster
- Master Airscrew

- Kyosho Magnetic Mayhem
- Trinity Speed Gems (Ruby, etc.)
- Leisure Model Electronics
- Astro Cobalt
- Cermark Cobalt
- Graupner Ultra Neodym


- Astro Brushless 020 and 05
- Aveox
- MaxCim
- Kontronik

Effect on Power
- Sailplane with 12x8 prop and 7x2000 cells, geared for 4 minute run
- Graupner #1793 Speed 600 7.2V
- 2.65:1 gearbox
- 25A input
- 123W output
- Kyosho Magnetic Mayhem
- 2.7:1 gearbox
-25A input
- 128W output
- Astro #605 Cobalt 05 Sport
- 2.5:1 gearbox
- 25A input
- 146W output
- Aveox 1406/3Y
- 2.4:1 gearbox
- 25A input
- 159W output

- Effect on Run Time
- Sailplane with 12x8 prop and 7x2000 cells, geared to give 138W output
- Graupner #1793 Speed 600 7.2V
- 2.2:1 gearbox
- 32A input
- 138W output
- 3:12 run time
- Kyosho Magnetic Mayhem
- 2.3:1 gearbox
- 31A input
- 138W output
- 3:19 run time
- Astro #605 Cobalt 05 Sport
- 2.6:1 gearbox
- 23A input
- 138W output
- 4:24 run time
- Aveox 1406/3Y
- 2.55:1 gearbox
- 22A input
- 138W output
- 4:44 run time




Graupner #1793 Speed 600 7.2V


Kyosho Magnetic Mayhem


Astro #605 Cobalt 05 Sport


Aveox 1406/3Y