Home :: GUIDE - #35 Sprocket Sizing and Gearing

GUIDE - #35 Sprocket Sizing and Gearing

GUIDE - #35 Sprocket Sizing and Gearing

 

GUIDE - PROJECT GEARING SELECTION

GEARING UP

#35 Gearing Explained

 

INTRODUCTION - About this guide

When customers choose #35 pitch gearing (which we highly recommend for projects due to the 2-piece split sprockets and removable link chains – see our chain guide for more information) I am often asked the question “What is the inside diameter of your split sprocket?” and “What is the outside diameter of an x tooth sprocket” so I’ve decided to write this informative but straight-forward guide focussed on explaining what needs to be done to fit our standard race kart sprockets and gearing your project.

Generally, when gearing your project, you have 3 problems to overcome.

1.       Fitting the sprocket to your axle

2.       Ensuring the overall sprocket size does not foul on the ground or chassis

3.       Selecting a practical starting gear ratio

This guide will run you through the decision making process as well as provide technical details on the products so that you can decide if #35 race kart gearing is suitable for your project.  I’ll run through these three sections quickly but informatively in the hope I don’t bore you, but that you have easy access to the information needed to get it right the first time.

PART 1 - Fitting the sprocket to your axle

Our #35 sprockets are a split sprocket which is ideal in situations where the sprocket is driven ‘inboard’ on the axle (ie: between the axle bearings).   They are easy to remove and install making gearing a breeze to get correct, or to change out a worn sprocket.

 

You can find our full range here: http://www.cutpriceracing.com.au/store/home.php?cat=351

 

The centre bore size A is 116mm.

 

The PCD Diameter(B) is (6x) 132mm (centre of 6mm holes on opposite sides of sprocket)

 

All standard race-kart sprocket hubs will accept our sprockets.  We can supply sprocket hubs to fit most metric shaft sizes – 25mm, 30mm, 35mm, 40mm.

You can find sprocket hubs to suit here (Click your axle size and keyway width to find your hub):

 

25mm/6mm, 30mm/6mm, 30mm/8mm, 35mm/6mm, 35mm/8mm, 40mm/8mm

 

The hubs will accept the sprocket perfectly.  All you need to do is slide it onto your shaft.  Select the correct size shaft version of the sprocket.  If you have an imperial size shaft, we cannot offer a solution, but some people have successfully adapted the metric hubs to an imperial shaft.

PART 2 – Ensuring the overall sprocket size does not foul on the ground or chassis

Your new #35 sprocket will differ in sizing depending on the number of teeth you have chosen.  Circumference will determine the number of teeth you will have.  The reason the size differs is because the pitch of the chain determines the length required for one full link or tooth.

 

For those uninterested in the math, please skip this paragraph.  #35 pitch is 9.525mm, so for every tooth, the circumference must be increased by 9.525mm.  In addition, the height of each tooth is about 5mm so we need to add approximately 2.5mm extra from the centreline of each tooth (or approximately 5mm to the diameter)   This means we have a formula #TEETH x 9.525mm = Pi x Diameter.  Or we could write it as #teeth x 9.525mm divided by Pi = Diameter plus 5mm.  Translating back to diameter, our smallest sprocket (53T) has a diameter of   53 x 9.525 / Pi (3.141592) = 166mm. 

 

Your chain will sit around 3mm proud of the tip of each tooth, so you’ll need to add approximately 6mm to the diameter of the sprocket to get the correct clearance amount.

 

Here’s a table of diameters:

#Teeth

Dia mm

Dia w/chain mm

53

166

172

54

169

175

55

172

178

56

175

181

57

178

184

58

181

187

59

184

190

60

187

193

61

190

196

62

193

199

63

196

202

64

199

205

65

202

208

66

205

211

67

208

214

68

211

217

69

214

220

70

217

223

71

220

226

72

223

229

73

226

232

74

229

235

75

232

238

76

235

241

77

238

244

78

241

247

79

244

250

80

247

253

81

250

256

82

253

259

83

256

262

84

259

265

85

262

268

 

PART 3 – Selecting a practical gear ratio

Once you’ve determined your limitations in relation to ground and chassis clearances, the next step is to determine the best gear ratio.  There are several things to consider, including:

-          Desired Acceleration

-          Desired Top Speed

-          Minimum operating speed

o   One of the most important considerations is the minimum ‘fully engaged’ clutch speed.  Most stock clutches engage around 2000rpm.  With a governed 4-stroke engine, that means you have a working range of somewhere between 2000 and 3500rpm.  If you select too tall gearing, and you constantly operate the kart at speeds which bring the motor close to or below the 2000rpm engagement point, you will encounter clutch problems as the clutch is continually slipping.

The following table gives approximate speeds for gearing.  It is recommended not to use gearing in the orange sections, and red sections will almost certainly result in mechanical failure. 

 

 Tall gearing (lower ratios) may struggle to gain rpm if the power of the engine is not enough to overcome the torque of the axle.  This is more pronounced the larger the wheels are, so bear this in mind. 

 

Always select the shortest gearing (highest ratio) first and work your way down with rear sprocket sizing to ensure you do not damage your clutch and that you can ensure your project will get mobile initially.

 

Senior rear rims & slicks 11x7.10-5 265mm dia 832.52  
Sprocket Sprocket Final 2000 3500 7000
Clutch Rear Ratio Min Max Max
12 53 4.42 23 40 79
12 54 4.50 22 39 78
12 55 4.58 22 38 76
12 56 4.67 21 37 75
12 57 4.75 21 37 74
12 58 4.83 21 36 72
12 59 4.92 20 36 71
12 60 5.00 20 35 70
12 61 5.08 20 34 69
12 62 5.17 19 34 68
12 63 5.25 19 33 67
12 64 5.33 19 33 66
12 65 5.42 18 32 65
12 66 5.50 18 32 64
12 67 5.58 18 31 63
12 68 5.67 18 31 62
12 69 5.75 17 30 61
12 70 5.83 17 30 60
12 71 5.92 17 30 59
12 72 6.00 17 29 58
12 73 6.08 16 29 57
12 74 6.17 16 28 57
12 75 6.25 16 28 56
12 76 6.33 16 28 55
12 77 6.42 16 27 54
12 78 6.50 15 27 54
12 79 6.58 15 27 53
12 80 6.67 15 26 52
12 81 6.75 15 26 52
12 82 6.83 15 26 51
12 83 6.92 14 25 51
12 84 7.00 14 25 50
12 85 7.08 14 25 49
           
13 53 4.08 25 43 86
13 54 4.15 24 42 84
13 55 4.23 24 41 83
13 56 4.31 23 41 81
13 57 4.38 23 40 80
13 58 4.46 22 39 78
13 59 4.54 22 39 77
13 60 4.62 22 38 76
13 61 4.69 21 37 75
13 62 4.77 21 37 73
13 63 4.85 21 36 72
13 64 4.92 20 36 71
13 65 5.00 20 35 70
13 66 5.08 20 34 69
13 67 5.15 19 34 68
13 68 5.23 19 33 67
13 69 5.31 19 33 66
13 70 5.38 19 32 65
13 71 5.46 18 32 64
13 72 5.54 18 32 63
13 73 5.62 18 31 62
13 74 5.69 18 31 61
13 75 5.77 17 30 61
13 76 5.85 17 30 60
13 77 5.92 17 30 59
13 78 6.00 17 29 58
13 79 6.08 16 29 58
13 80 6.15 16 28 57
13 81 6.23 16 28 56
13 82 6.31 16 28 55
13 83 6.38 16 27 55
13 84 6.46 15 27 54
13 85 6.54 15 27 53
           
18 53 2.94 34 59 119
18 54 3.00 33 58 117
18 55 3.06 33 57 114
18 56 3.11 32 56 112
18 57 3.17 32 55 110
18 58 3.22 31 54 109
18 59 3.28 30 53 107
18 60 3.33 30 52 105
18 61 3.39 29 52 103
18 62 3.44 29 51 102
18 63 3.50 29 50 100
18 64 3.56 28 49 98
18 65 3.61 28 48 97
18 66 3.67 27 48 95
18 67 3.72 27 47 94
18 68 3.78 26 46 93
18 69 3.83 26 46 91
18 70 3.89 26 45 90
18 71 3.94 25 44 89
18 72 4.00 25 44 87
18 73 4.06 25 43 86
18 74 4.11 24 43 85
18 75 4.17 24 42 84
18 76 4.22 24 41 83
18 77 4.28 23 41 82
18 78 4.33 23 40 81
18 79 4.39 23 40 80
18 80 4.44 22 39 79
18 81 4.50 22 39 78
18 82 4.56 22 38 77
18 83 4.61 22 38 76
18 84 4.67 21 37 75
18 85 4.72 21 37 74
Not Recommended       
(either gearing too tall, or sprocket diameter too close to ground)
Certain damage to drivetrain (too tall gearing or sprocket fouls)
           
13" Off-Road wheels 13x5.00-6 290mm dia 911.06  
Sprocket Sprocket Final 2000 3500 7000
Clutch Rear Ratio Min Max Max
12 53 4.42 25 43 87
12 54 4.50 24 43 85
12 55 4.58 24 42 83
12 56 4.67 23 41 82
12 57 4.75 23 40 81
12 58 4.83 23 40 79
12 59 4.92 22 39 78
12 60 5.00 22 38 77
12 61 5.08 22 38 75
12 62 5.17 21 37 74
12 63 5.25 21 36 73
12 64 5.33 20 36 72
12 65 5.42 20 35 71
12 66 5.50 20 35 70
12 67 5.58 20 34 69
12 68 5.67 19 34 68
12 69 5.75 19 33 67
12 70 5.83 19 33 66
12 71 5.92 18 32 65
12 72 6.00 18 32 64
12 73 6.08 18 31 63
12 74 6.17 18 31 62
12 75 6.25 17 31 61
12 76 6.33 17 30 60
12 77 6.42 17 30 60
12 78 6.50 17 29 59
12 79 6.58 17 29 58
12 80 6.67 16 29 57
12 81 6.75 16 28 57
12 82 6.83 16 28 56
12 83 6.92 16 28 55
12 84 7.00 16 27 55
12 85 7.08 15 27 54
           
13 53 4.08 27 47 94
13 54 4.15 26 46 92
13 55 4.23 26 45 90
13 56 4.31 25 44 89
13 57 4.38 25 44 87
13 58 4.46 25 43 86
13 59 4.54 24 42 84
13 60 4.62 24 41 83
13 61 4.69 23 41 82
13 62 4.77 23 40 80
13 63 4.85 23 39 79
13 64 4.92 22 39 78
13 65 5.00 22 38 77
13 66 5.08 22 38 75
13 67 5.15 21 37 74
13 68 5.23 21 37 73
13 69 5.31 21 36 72
13 70 5.38 20 36 71
13 71 5.46 20 35 70
13 72 5.54 20 35 69
13 73 5.62 19 34 68
13 74 5.69 19 34 67
13 75 5.77 19 33 66
13 76 5.85 19 33 65
13 77 5.92 18 32 65
13 78 6.00 18 32 64
13 79 6.08 18 31 63
13 80 6.15 18 31 62
13 81 6.23 18 31 61
13 82 6.31 17 30 61
13 83 6.38 17 30 60
13 84 6.46 17 30 59
13 85 6.54 17 29 59
           
18 53 2.94 37 65 130
18 54 3.00 36 64 128
18 55 3.06 36 63 125
18 56 3.11 35 61 123
18 57 3.17 35 60 121
18 58 3.22 34 59 119
18 59 3.28 33 58 117
18 60 3.33 33 57 115
18 61 3.39 32 56 113
18 62 3.44 32 56 111
18 63 3.50 31 55 109
18 64 3.56 31 54 108
18 65 3.61 30 53 106
18 66 3.67 30 52 104
18 67 3.72 29 51 103
18 68 3.78 29 51 101
18 69 3.83 29 50 100
18 70 3.89 28 49 98
18 71 3.94 28 49 97
18 72 4.00 27 48 96
18 73 4.06 27 47 94
18 74 4.11 27 47 93
18 75 4.17 26 46 92
18 76 4.22 26 45 91
18 77 4.28 26 45 89
18 78 4.33 25 44 88
18 79 4.39 25 44 87
18 80 4.44 25 43 86
18 81 4.50 24 43 85
18 82 4.56 24 42 84
18 83 4.61 24 41 83
18 84 4.67 23 41 82
18 85 4.72 23 41 81