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mechanics-dat/mechanical-parts-dat/gear-dat/gear-dat.md
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@@ -28,11 +28,11 @@ For small-diameter wheels, the gear ratio is designed to balance pedaling effort
28 28
29 29
#### 1. Typical Tooth Counts by Wheel Size
30 30
31
-| Wheel Size | Front Chainring (Teeth) | Rear Cog (Teeth) | Gear Ratio | Purpose |
32
-| :--- | :--- | :--- | :--- | :--- |
33
-| **12-inch** | **24T - 26T** | **16T** | 1.50 - 1.62 | Maximum torque for toddlers/beginners. |
34
-| **14-inch** | **28T** | **16T** | 1.75 | Balanced ratio for neighborhood riding. |
35
-| **16-inch** | **28T - 32T** | **16T or 18T** | 1.77 - 2.00 | Higher top speed for older children. |
31
+| Wheel Size | Front Chainring (Teeth) | Rear Cog (Teeth) | Gear Ratio | Purpose |
32
+| :---------- | :---------------------- | :--------------- | :---------- | :-------------------------------------- |
33
+| **12-inch** | **24T - 26T** | **16T** | 1.50 - 1.62 | Maximum torque for toddlers/beginners. |
34
+| **14-inch** | **28T** | **16T** | 1.75 | Balanced ratio for neighborhood riding. |
35
+| **16-inch** | **28T - 32T** | **16T or 18T** | 1.77 - 2.00 | Higher top speed for older children. |
36 36
37 37
---
38 38
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@@ -46,6 +46,47 @@ For small-diameter wheels, the gear ratio is designed to balance pedaling effort
46 46
* **The Chain:** * Standard small bikes use a **1/2" x 1/8"** chain (wider than multi-speed chains).
47 47
48 48
49
+
50
+## bicycle gear
51
+
52
+
53
+| Feature | Freewheel (Old Standard/Budget) | Cassette (Modern/Performance) |
54
+| :---------------- | :--------------------------------------------------- | :------------------------------------------------ |
55
+| **Mounting** | Screws onto threads on the hub. | Slides onto a splined "freehub" body. |
56
+| **Mechanism** | Ratchet is inside the gear cluster. | Ratchet is built into the hub (freehub). |
57
+| **Replacement** | You replace the gears and ratchet together. | You replace only the gear cluster. |
58
+| **Axle Strength** | Higher risk of bent axles (bearings are further in). | Lower risk (bearings are positioned further out). |
59
+
60
+
61
+
62
+| Feature | **Freewheel (Live Flywheel)** | **Fixed Gear (Dead Flywheel)** |
63
+| :------------------- | :----------------------------------------------------------------- | :-------------------------------------------------------------------- |
64
+| **Coasting** | Can coast; pedals can remain stationary while the bike moves. | Cannot coast; if the wheels are turning, the pedals **must** turn. |
65
+| **Reverse Pedaling** | The pedals spin freely backward without affecting the wheel. | Used to reverse the bike or apply "back-pressure" to slow down/brake. |
66
+| **Mechanical Link** | Connected via a one-way ratcheting mechanism (clutch). | Directly "fixed" or bolted to the hub; no internal moving parts. |
67
+| **Primary Use** | Standard commuter bikes, vintage mountain bikes, most kids' bikes. | Track cycling (velodrome), "Fixie" culture, and some indoor trainers. |
68
+
69
+
70
+![](2026-03-01-00-53-41.png)
71
+
72
+
73
+## Cassette
74
+
75
+![](2026-03-01-00-55-32.png)
76
+
77
+
78
+
79
+## Common Freewheel Thread Standards
80
+
81
+| Standard Name | Metric Diameter (Approx.) | Imperial Specification | Common Application |
82
+| :----------------------- | :------------------------ | :--------------------- | :--------------------------------------------------- |
83
+| **Standard ISO/English** | **34.92 mm** | **1.375" x 24 TPI** | **Most bicycles (95%)**; this is the "34mm" you see. |
84
+| **BMX / Metric Small** | **30.00 mm** | **1.181" x 30 TPI** | Small freewheels (under 16 teeth) for BMX. |
85
+| **French Standard** | **34.70 mm** | **M34.7 x 1.0 mm** | Vintage European bikes (now obsolete). |
86
+| **Italian Standard** | **35.00 mm** | **35mm x 24 TPI** | Vintage Italian racing bikes. |
87
+
88
+
89
+
49 90
## ref
50 91
51 92
- [[motor-dat]]
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mechanics-dat/mechanical-parts-dat/wheel-dat/wheel-hub-dat/wheel-hub-dat.md
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@@ -1,7 +1,7 @@
1 1
2 2
# wheel-hub-dat
3 3
4
-- [[wheel-dat]] - [[wheel-hub-dat]] - [[bearing-dat]] - [[gear-dat]]
4
+- [[wheel-dat]] - [[wheel-hub-dat]] - [[bearing-dat]] - [[gear-dat]] - [[inch-dat]]
5 5
6 6
![](2026-02-28-19-59-13.png)
7 7
... ...
@@ -10,6 +10,21 @@
10 10
- 16 x 2.125
11 11
12 12
13
+
14
+## The "2.4" — Tire Width
15
+
16
+
17
+When you see a tire size labeled as **12 x 2.4**, it is using the Imperial system (inches). Here is the breakdown:
18
+
19
+
20
+The second number represents the **Width** of the tire at its widest point when inflated.
21
+* **Measurement:** 2.4 inches.
22
+* **Metric Conversion:** $2.4 \times 25.4 = \mathbf{60.96\text{ mm}}$ (approx. 61mm).
23
+* **Significance:** A 2.4-inch tire is considered a "Wide" or "Fat" tire. For your **human-carrying scooter**, this is excellent because:
24
+ * **Stability:** A wider contact patch provides better balance.
25
+ * **Cushioning:** Larger air volume acts as a natural shock absorber for a smoother ride.
26
+
27
+
13 28
- 12~20 inch
14 29
15 30
## 14-inch wheels == kids bike
... ...
@@ -59,6 +74,11 @@ in almost all modern bicycles, the axle itself does not rotate.
59 74
4. When you pedal, the **sprockets** push the hub, and the whole wheel spins around that fixed center axis.
60 75
61 76
77
+
78
+## 塔基 / 卡式 花鼓 / 旋式花鼓
79
+
80
+![](2026-03-01-01-07-01.png)
81
+
62 82
## ref
63 83
64 84
- [[wheel]] - [[wheel-hub]]
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mechanics-dat/mechanical-structure-dat/Shaft-dat/2026-03-01-01-14-56.png
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mechanics-dat/mechanical-structure-dat/Shaft-dat/Shaft-dat.md
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@@ -98,9 +98,18 @@ How to make it safer
98 98
冷却后恢复尺寸，形成非常牢固的过盈配合。
99 99
100 100
101
+## jack shaft
101 102
103
+![](2026-03-01-01-14-56.png)
104
+
105
+== 中间轴
106
+
107
+![](2026-03-01-01-16-55.png)
108
+
109
+![](2026-03-01-01-20-20.png)
102 110
103 111
## ref
104 112
105 113
- [[rod-system-dat]]
106
-![shaft-connection-dat/2025-12-30-14-08-06.png](shaft-connection-dat/2025-12-30-14-08-06.png)
... ...
\ No newline at end of file
0
+
1
+- [[m]]
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\ No newline at end of file
mechanics-dat/mechanical-structure-dat/chain-dat/chain-dat.md
... ...
@@ -8,13 +8,30 @@
8 8
![](2026-01-08-13-45-31.png)
9 9
10 10
11
-## chain types ?
11
+## chain types
12
+
13
+| Chain / Model | Pitch (in) | Pitch (mm) | Internal Width (W) | Avg. Tensile Strength | Typical / Best Use Case |
14
+| :------------------------------- | :--------- | :--------- | :----------------: | :-------------------: | :---------------------------------------------- |
15
+| **Bicycle Standard (410 / 415)** | 1/2" | 12.70 | — | — | Standard bicycles, most electric bike motors |
16
+| **#25 (1/4")** | 1/4" | 6.35 | 3.18 mm | ~4,000 N | Small, high-speed motors; miniature robotics |
17
+| **T8F (8 mm)** | — | 8.00 | 4.80 mm | ~6,000 N | Heavy-duty scooters; higher-torque small drives |
18
+| **#35 (3/8")** | 3/8" | 9.525 | 4.77 mm | ~9,500 N | Go-karts, high-power motors, heavy-load DIY |
19
+
20
+Notes:
21
+- Pitch is the most critical parameter — chain and sprocket must share the same pitch to mesh correctly.
22
+- Inner width (W) and tooth thickness must match or be compatible with the sprocket.
23
+
24
+
25
+## 1/2" Circular Pitch (CP) / #40 Sprockets
26
+
27
+If the gear is designed for a 1/2" spacing (common in ANSI #40 roller chains or 1/2" CP spur gears), the following tooth counts are industry standards:
28
+
29
+| Category | Common Tooth Counts ($N$) |
30
+| :----------------------- | :----------------------------- |
31
+| **Small (Drive/Pinion)** | 9, 10, 11, 12, 13, 14, 15 |
32
+| **Medium (Idler)** | 16, 17, 18, 19, 20, 24, 25 |
33
+| **Large (Driven)** | 30, 32, 35, 40, 48, 54, 60, 72 |
12 34
13
-| Chain Type | Pitch (P) | Internal Width (W) | Avg. Tensile Strength | Best Use Case |
14
-| :------------- | :-------- | :----------------- | :-------------------- | :--------------------------------- |
15
-| **#25 (1/4")** | 6.35 mm | 3.18 mm | ~4,000 N | Small, high-speed, lightweight. |
16
-| **T8F (8mm)** | 8.00 mm | 4.80 mm | ~6,000 N | Heavy-duty scooters (High Torque). |
17
-| **#35 (3/8")** | 9.53 mm | 4.77 mm | ~9,500 N | Go-karts / Heavy loads. |
18 35
19 36
20 37
## main specs
... ...
@@ -61,6 +78,52 @@
61 78
- Minimum sprocket tooth count: Too few teeth increases bending fatigue on the chain; typically choose ≥ 12 teeth when possible.
62 79
- Mounting alignment: Shaft diameter, keyway, and bolt pattern must match the sprocket mounting method.
63 80
81
+
82
+## chain modify
83
+
84
+
85
+To modify a chain for a bike, you need a specific tool called a **Chain Breaker**.
86
+
87
+---
88
+
89
+### 1. Opening the Chain
90
+
91
+First, identify if your chain has a **Master Link** (a link that looks different and is designed to be removable).
92
+
93
+#### Method A: With a Master Link
94
+* **Action:** Use master link pliers (or needle-nose pliers) to squeeze the two pins together.
95
+* **Result:** The side plates will slide and unlock, allowing the chain to pull apart.
96
+
97
+#### Method B: Without a Master Link (Standard Link)
98
+* **Action:** Place any link into the **Chain Breaker** tool.
99
+* **Process:** 1. Align the tool's driving pin with the chain rivet (pin).
100
+ 2. Turn the handle to push the rivet out.
101
+ 3. **Important:** If you intend to reuse the pin, **do not push it all the way out**. Leave it hanging slightly on the outer plate.
102
+
103
+---
104
+
105
+### 2. Modifying the Length (Shortening)
106
+
107
+To make the chain fit your specific motor-to-wheel distance:
108
+
109
+1. **Measure:** Wrap the chain around your **Drive Wheel** (motor) and **Driven Wheel** (rear hub) to determine the required length.
110
+2. **Determine the Cut Point:** * If using a **Master Link**: Both ends of the chain must be **Inner Links**.
111
+ * If joining via a **Pin**: One end must be an **Inner Link** and the other an **Outer Link**.
112
+3. **Remove Links:** Use the chain breaker to push the pins out completely on the excess section of the chain.
113
+
114
+---
115
+
116
+### 3. Reconnecting the Chain
117
+
118
+1. **Threading:** Guide the chain through your frame and over the sprockets.
119
+2. **Joining:**
120
+ * **Using a Master Link:** Insert the two halves from opposite sides and pull the chain apart until you hear a "click."
121
+ * **Using a Pin:** Use the chain breaker to push the pin back through the links until it is centered.
122
+3. **Fixing Stiff Links:** If the connection point is stiff, gently bend the chain sideways at that joint to "set" the plates and ensure smooth rotation.
123
+
124
+
125
+
126
+
64 127
## ref
65 128
66 129
- [[power-transmission-dat]]
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mechanics-dat/physics-dat/inch-dat/inch-dat.md
... ...
@@ -0,0 +1,6 @@
1
+
2
+# inch-dat
3
+
4
+8 inch == 8 x 25.4 == 203.2 mm
5
+
6
+