22
Motor Gearing:
The important thing is to keep the motor in its optimal RPM range as much as possible around the entire track. This will
depend on the straight-away length and the size of the infi eld turns. The chart below is a guide to give you a starting point. You may want
to try gearing up (larger pinion or smaller spur) or down (smaller pinion or larger spur), one size at a time, noting the straight-away speed
and acceleration through the infi eld.
*NOTE: OVER GEARING (TOO LARGE OF A PINION OR TOO SMALL OF A SPUR) CAN CAUSE DAMAGE TO BOTH YOUR
ELECTRONICS AND MOTOR. USE CAUTION WHEN SELECTING YOUR GEARING.
Rollout:
The overall gear ratio, including the tire diameter, is compared in terms of a distance traveled (usually in mm) per revolution of the
motor, called rollout. In foam tire racing, the diameter of the tire is left as an option to the racer (within a given range, set by the sanctioning
body) to adjust the way the car handles. When changing the diameter of the tire, the overall gear ratio is effected. Use the formula below to
calculate the rollout of the car for a given tire diameter (
d
), internal drivetrain ratio (
i
), spur gear size (
s
), and pinion gear size (
p
):
For example:
(
)
3.1416
Diameter of Tire (
)
where
# of Teeth on Spur Gear
# of Teeth on Pinion Gear
Internal Drive Ratio (JRX-S=1.83)
d
mm
d
Rollout
s
s
i
p
p
i
π
π
⎧ ≈
⎪⎪⎪
⎪ =
⎪⎪
×
⎪
=
=
⎨
⎛
⎞
⎪
⎟
⎪
⎜ × ⎟
=
⎪
⎜
⎟
⎪
⎜
⎟
⎝
⎠
⎪⎪ =
⎪⎩
(
) (
)
(
)
3.1416
57
3.1416 57
179.07
If
128
Then
20.6
128
8.67
1.83
27
27
1.83
d
mm
mm
mm
s
Rollout
mm
p
i
π
⎧
⎫
≈
⎪
⎪
⎪
⎪
⎪
⎪
⎪
⎪
=
⎪
⎪
⎪
⎪
×
⎪
⎪
=
=
=
=
⎨
⎬
⎛
⎞
⎪
⎪
⎟
⎪
⎪
⎜
×
⎟
=
⎪
⎪
⎜
⎟
⎜
⎪
⎪
⎝
⎠
⎪
⎪
⎪
⎪
=
⎪
⎪
⎩
⎭
Table 4: Suggested gearing for the JRX-S Type R Expert Racing Sedan
Motor Manufacturer, Make/Model
Spur
Pinion
Suggested Rollout
Stock
EPIC Based Monster
128
32-33
25.0mm-27.0mm
EPIC Based Binary (Two Magnet)
128
32-33
25.0mm-27.0mm
EPIC Based Binary (Four Magnet)
128
30-31
23.5mm-25.5mm
EPIC Based CO27
128
33-36
26.5mm-27.5mm
EPIC Based X
128
36-37
27.5mm-28.5mm
TOP Based (Standard Brush)
128
36-37
28.0mm-30.0mm
TOP Based (V2)
128
36-37
28.0mm-30.0mm
Yokomo Based
128
36-37
28.0mm-30.0mm
19T
EPIC Based Chameleon 2 19T
128
37-40
30.0mm-31.0mm
EPIC Komodo 19T
128
32-35
29.0mm-30.0mm
Checkpoint Based 19T
128
37-40
30.0mm-31.0mm
Yokomo Based 19T 4 Magnet
128
37-40
30.0mm-31.0mm
23T
128
38-41
31.0mm-32.0mm
Modi
fi ed
7 Turn
128
26-27
19.5mm-20.5mm
8 Trun
128
27-28
20.5mm-21.5mm
9 Turn
128
28-29
21.5mm-22.5mm
10 Turn
128
29-30
22.5mm-23.5mm
11 Turn
128
30-31
23.5mm-24.5mm
12 Turn
128
31-32
24.5mm-25.0mm
Brushless
3.5 Turn Sintered Rotor
128
20-22
15.5mm-16.5mm
4.5 Turn Bonded Rotor
128
21-23
16.5mm-17.5mm
4.5 Turn Sintered Rotor
128
22-24
17.0mm-17.5mm
5.5 Turn Bonded Rotor
128
23-25
17.5mm-18.5mm
5.5 Turn Sintered Rotor
128
24-26
18.5mm-19.5mm
6.5 Turn Bonded Rotor
128
26-28
19.5mm-21.0mm
6.5 Turn Sintered Rotor
128
28-30
21.0mm-22.0mm
7.5 Turn Bonded Rotor
128
30-33
23.0mm-24.0mm
7.5 Turn Sintered Rotor
128
31-34
23.5mm-25.0mm
Novak SS5800 8.5 Turn Bonded Rotor
128
29-31
22.0mm-23.0mm
Novak SS5800 8.5 Turn Sintered Rotor
128
29-32
22.0mm-24.0mm
Novak SS4300 10.5 Turn Bonded Rotor
128
34-37
26.0mm-28.0mm
Novak SS4300 10.5 Turn Sintered Rotor
128
36-39
27.0mm-29.0mm
Novak SS13.5 Turn Bonded Rotor
128
35-39
28.0mm-30.0mm
Novak SS13.5 Turn Sintered Rotor
128
39-42
30.0mm-32.0mm
This example gives a Rollout of 20.6mm, meaning that this car will
travel 20.6mm per one revolution of the motor. Opposite of the Spur/
Pinion ratio, the higher the Rollout value, the higher the gearing of
the car. See Table 3 (Right) for suggested starting rollout values.
Tuning the Front End of the JRX-S Type R
Shock Location:
The
Type R
has three mounting locations on the front shock tower. Leaning the shocks in (moving them closer to the center
of the tower) will give a smoother transition as the car enters into the corner and improve consistency but will yield less total steering and a
slower reaction. This can be useful on high bite surfaces. Standing the shocks upright (moving them further out from the center of the tower)
will increase responsiveness and generate more total steering. This will also increase forward traction and on-power steering. This can be
helpful on tight, technical tracks where steering is vital.
64P Spur Gear
118
120
122
124
126
128
130
64P
Pinion Gear
21
10.28
10.46
10.63
10.81
10.98
11.15
11.33
22
9.82
9.98
10.15
10.31
10.48
10.65
10.81
23
9.39
9.55
9.71
9.87
10.03
10.18
10.34
24
9.00
9.15
9.30
9.46
9.61
9.76
9.91
25
8.64
8.78
8.93
9.08
9.22
9.37
9.52
26
8.31
8.45
8.59
8.73
8.87
9.01
9.15
27
8.00
8.13
8.27
8.40
8.54
8.68
8.81
28
7.71
7.84
7.97
8.10
8.24
8.37
8.50
29
7.45
7.57
7.70
7.82
7.95
8.08
8.20
30
7.20
7.32
7.44
7.56
7.69
7.81
7.93
31
6.97
7.08
7.20
7.32
7.44
7.56
7.67
32
6.75
6.86
6.98
7.09
7.21
7.32
7.43
33
6.54
6.65
6.77
6.88
6.99
7.10
7.21
34
6.35
6.46
6.57
6.67
6.78
6.89
7.00
35
6.17
6.27
6.38
6.48
6.59
6.69
6.80
36
6.00
6.10
6.20
6.30
6.41
6.51
6.61
37
5.84
5.94
6.03
6.13
6.23
6.33
6.43
38
5.68
5.78
5.88
5.97
6.07
6.16
6.26
39
5.54
5.63
5.72
5.82
5.91
6.01
6.10
40
5.40
5.49
5.58
5.67
5.76
5.86
5.95
41
5.27
5.36
5.45
5.53
5.62
5.71
5.80
Table 3: 64P Gear Ratio Chart
SETUP GUIDE
SETUP GUIDE
