Tokay Radio Control Modelers

Although modern glow-plug model engines can last almost a lifetime, the bearings in them eventually need replacement.

Sometimes they are attacked by rust or corrosion, other times they might simply be worn out.

The average model engine might turn at speeds of up to 15,000 RPMs which means that in an average year's flying of (say) an hour per weekend, that's a total of almost 50 million revolutions!

It's only natural that no matter how good the bearings are, and no matter how fancy your fuel is, sooner or later, those bearings will need replacement.

Fortunately, replacing those bearings isn't rocket science and can easily be performed by the average modeler with access to little more than an oven or gas torch, a rag or glove, some basic tools and a little space.

Because pictures are worth a thousand words, I've created a couple of videos that take you through the process

Where to get your bearings

I guess I could charge various bearing-suppliers a lot of money to advertise on this page but instead I'm going to let you in on a secret...

There are plenty of places that will sell you new bearings for your engine at highly inflated prices. Sometimes these companies have very flashy logos and websites that serve to create the illusion that their product is something special.

The reality is that, if you're looking for the best value in model engine bearings then you really can't go past RC Bearings. I've regularly bought my bearings from Paul at RC-Bearings.com and have found them to be far better than those provided as standard equipment in reputable brands such as Saito, Thunder Tiger and Magnum.

Paul's prices are extremely good, his service is second to none, and he is straight as a die. I strongly urge you to compare his prices to those of mainstream bearing suppliers before buying

2-Stroke Engine Prop Sizes

Engine Size
(cu.in)

Starting Size

Other Sizes To Try

.049

6-3

5.25-4, 5.5-4, 6-3.5, 6-4, 7-3

.09

7-4

7-3, 7-4.5, 7-5

.15

8-4

8-5, 8-6, 9-4

.19 -.25

9-4

8-5, 8-6, 9-4

.29 -.30

9-6

9-7, 9.5-6, 10-6

.35 -.36

10-6

9-7, 10-5, 11-4

.40

10-6

9-8, 11-5

.45

10-7

10-6, 11-5, 11-6, 12-4

.50

11-6

10-8, 11-7, 12-4, 12-5

.60 -.61

11-7

11-7.5, 11-7.75, 11-8, 12-6

.70

12-6

11-8, 12-8, 13-6, 14-4

.78 -.80

13-6

12-8, 14-4, 14-5

.90 -.91

14-6

13-8, 15-6, 16-5

1.08

16-6

15-8, 18-5

1.2

16-8

16-10, 18-5, 18-6

1.5

18-6

18-8, 20-6

1.8

18-8

18-10, 20-6, 20-8, 22-6

2.0

20-8

18-10, 20-6, 20-10, 22-6

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4-Stroke Engine Prop Sizes

Engine Size
(cu.in)

Starting Size

Other Sizes To Try

.20 -.21

9-6

9-5, 10-5

.40

11-6

10-6, 10-7, 11-4, 11-5,
11-7, 11-7.5, 12-4, 12-5

.45 -.48

11-6

10-6, 10-7, 10-8, 11-7,
11-7.5, 12-4, 12-5, 12-6

.60 -.65

12-6

11-7.5, 11-7.75, 11-8, 12-8,
13-5, 13-6, 14-5, 14-6

.80

13-6

12-8, 13-8, 14-4, 14-6

.90

14-6

13-6, 14-8, 15-6, 16-6

1.20

16-6

14-8, 15-6, 15-8, 16-8,
17-6, 18-5,18-6

1.60

18-6

15-6, 15-8, 16-8,
18-6, 18-8, 20-6

2.40

18-10

18-12, 20-8, 20-10

2.70

20-8

18-10, 18-12, 20-10

3.00

20-10

18-12, 20-10

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Engine Size Conversion Chart (ci=cc)

Cubic Inches

Cubic Centimeters

.049

.09

1.5

.15

2.5

.19

3.1

.21

3.5

.25

4.1

.29

4.8

.35

5.7

.40

6.5

.46

7.5

.50

8.2

.61

10.0

.80

13.0

.91

14.9

1.20

20.0

1.50

25.0

1.60

26.2

1.80

30.0

2.00

32.8

2.40

39.3

2.70

44.3

3.00

49.2

1Cubic Inch =

16.3934 Cubic Centimeters

.061 Cubic Inch =

1 Cubic Centimeter

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Aircraft Trimming Chart for aerobatic flight

To test for:

Test procedure:

Observations:

Adjustments:

Control Neutrals

Fly model straight & level

Use transmitter trims to achieve hands-off straight & level flight

Adjust devises to center transmitter trims

Control Throws

While flying apply full deflection of each control

Check response rate for each control

Aileron High: 3 rolls in 4 seconds
Aileron Low: 3 rolls in 6 seconds
Elevator High: Allows smooth square corners
Elevator Low: 130' diameter loop
Rudder High: 30-35 degrees for stall turns
Elevator Low: Just enough to maintain knife edge flight

Incidence

Power off vertical dive, cross wind. Release controls when aircraft is vertical

A. Model continues straight down
B. Model starts to pull out
C. Model goes nose down

A. No adjustments
B. Reduce incidence
C. Increase incidence

Center of Gravity
(method 1)

Roll model inverted

A. Lots of down elevator required to maintain level flight
B. No down elevator required

A. Add tail weight
B. Add nose weight

Center of Gravity
(method 2)

Roll into near vertically banked turn

A. Nose drops
B. Tail drops

A. Add weight to tail
B. Add weight to nose

Tip Weight (course adjustment)

Fly model straight & level upright. Check aileron trim, maintain wing level. Roll model inverted, wings level. Release aileron stick.

A. Model does not drop a wing.
B. Left wing drops
C. Right wing drops

A. No adjustment needed
B. Add weight to right tip
C. Add weight to left tip

Side Thrust

Fly model away from you into any wind. Pull into vertical climb watching as model slows down

A. Model continues straight up
B. Model veers left
C. Model veers right

A. No adjustments needed
B. Add weight to right tip
C. Add weight to left tip

Up/Down Thrust

Fly model away from you into wind. Pull into vertical climb and release elevator.

A. Model continues straight up
B. Model pulls up
C. Model pulls down

A. No adjustment needed
B. Add down thrust
C. Reduce down thrust

Tip Weight

Fly model away from you into wind, pull into small diameter loop

A. Model comes out wings level
B. Right wing low
C. Left wing low

A. No adjustment needed
B. Add weight to left tip
C. Add weight to right tip or remove from left tip

Aileron Differential

Fly model on normal pass and do 3 rolls

A. Roll axis on model centerline
B. Roll axis off to the side as roll command
C. Roll axis off to opposite side of roll command

A. Differential Okay
B. Increase differential
C. Decrease differential

Dihedral

Fly model on normal pass, roll into knife edge flight. Maintain with top rudder. (Test on both right and left side)

A. Model does not roll out of knife edge
B. Model rolls in direction of applied rudder
C. Model rolls opposite the rudder in both tests

A. Dihedral Okay
B. Reduce dihedral
C. Increase dihedral

Elevator Alignment
(models with split elevators)

Fly model straight into wind. Pull into inside loop. Roll inverted and push into outside loop

A. No rolling when elevator applied
B. Model rolls in same direction in both tests
C. Model rolls in opposite directions in both tests

A. Elevators correctly aligned
B. Elevator misaligned. raise or lower one half
C. One elevator half has more throw than the other. (Model will roll to the side with the most throw) Reduce the throw on one side, or increase on the other side

Pitching in Knife Edge Flight

Same as dihedral test

A. No pitch up or down
B. Model pitches up
C. Model pitches down

A. No adjustment needed
B. Alternate cures;
1. Move the CG back.
2. Increase the wing incidence.
3. Drop the ailerons
C. Reverse the above.

Although these steps will work on any aircraft, they are for experienced pilots to trim aerobatic aircraft. If you are uncomfortable with any of these maneuvers, get help. Trimming must be done in calm conditions. Make multiple tests before making adjustments. Trimming chart courtesy of Russell Knetzger of Milwaukee, Wisconsin.
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Metric Conversions to Inches

Metric (MM)

American (Inches)

1.0

1/32

1.5

1/16

2.5

3/32

3.0

1/8

5.0

3/16

6.0

1/4

8.0

5/16

9.5

3/8

13.0

1/2

25.4

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Calculating Wing Loading

Wing loading is the key factor for good aerobatic performance! As a guideline, a Sports Aerobatic wing loading of 19 to 25 ounces per square foot would be ideal.

To calculate wing loading:

Convert weight from pounds to ounces.

Weight of model 5 lb. X 16 oz./lb. = 80 Ounces

Wing Area in square inches.

600 sq. in. divided by 144 (sq. ft.) = 4.16 sq.ft.

Divide ounces by square feet.

80 oz. divided by 4.16 (sq.ft.) = 19.23 oz. per square foot.

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