# Belts & Pulleys

## Belts and Pulleys Basics

### Common Terms

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FSG1cAHzxagNI655oP4lx%2FPulley%20Anatomy.svg?alt=media&#x26;token=34979089-d8e1-4fe0-9715-a0bdd747b027" alt=""><figcaption></figcaption></figure>

{% tabs %}
{% tab title="Pitch Diameter" %}
**Pitch Diameter** also known as **PD** is the circle that is formed while the belt and pulley are meshed together and which the belt rotates around. If you wish to find the PD, reference the formula below.

**(Pitch x Number of T) ÷ π**
{% endtab %}

{% tab title="Outside Diameter" %}
The **Outside Diameter** also known as **OD** refers to the outside diameter of the pulley.&#x20;
{% endtab %}

{% tab title="Pitch Length" %}
**Pitch Length** also known as **PL** is the length or circumference of a belt. If you wish to find the PL, reference the formula below.

**T x Pitch**
{% endtab %}

{% tab title="Number of Teeth" %}
The **Number of Teeth,** **T,** is simply the amount of peaks that are around the pulley. If you wish to find T, reference the formula below.

**PL ÷ Pitch**
{% endtab %}
{% endtabs %}

### Calculating Center to Center

#### How to Use WCP 's Belt Distance Calculator

WCP now offers a built-in calculator to provide all our customers with piece of mind when designing with belts and pulleys. If you are interested in viewing our calculator or knowing how to use it, see below for more information.

{% hint style="info" %}
Use this calculator to find the correct center to center distance for belts ([WCP Belt Calculator](https://wcproducts.com/pages/calculator-belt))
{% endhint %}

You will need a few pieces of information when using the WCP Belt Calculator:

1. Belt pitch to be used
   1. 3mm for GT2/GT3 belts
   2. 5mm for HTD Belts
2. Number of teeth for both pulleys
3. Approximate distance between centers of the two pulleys

The Output from the calculator will give you the belt center to center as well as the tooth count for the closet belt to the values entered. It will also give you the information for one belt size higher and lower.

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FGaHS6QCGTCKCniEH3Xxx%2FBelt%20Calculator%20Example.svg?alt=media&#x26;token=9c570bc8-8759-4eee-9e59-b8700d1bcd2e" alt=""><figcaption></figcaption></figure>

#### Center to Center Equations

The equation below shows the minimum center distance that should be used.&#x20;

$$
CC=\frac{Tooth Count\_{1}
+Tooth Count\_{2}}{2π}{x Pitch}
$$

The equation below shows the center distance for equally sized pulleys.

$$
CC=\frac{ Belt Tooth Count
-Pulley Tooth Count\_{}}{2}
$$

The examples below are places where a looser belt may be beneficial. Subtracting center distance can help reduce the overall load of the system which in turn reduces motor load and power consumption.

* First Stage Reduction: -0.000 to -0.003
* Intake Rollers: -0.015 to -0.020
* Conveyor System: -0.015" to -0.020"

### Recommended Applications

#### GT2 Belts

* First stage reductions
* Motor to flywheel
* Low load&#x20;

#### HTD Belts:

* Intake or conveyor systems
* Drivetrains
* Medium load

## GT2 Belts and Pulleys <a href="https://wcproducts.com/products/gt2-timing-pulleys-belts" class="button primary" data-icon="list">Product Page</a>

GT2 timing belts are intended for lower load applications such as the first reduction in a gearbox, or motor to flywheel. GT2 belts use a smaller pitch than HTD belts, which means you can use larger reductions in those tight fit areas of your robot.

{% hint style="info" %}
All GT2 Pulleys will now be clocked and engraved. An alignment notch has also been added to help with clocking multiple items together during assembly.
{% endhint %}

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FdCnUg31e2bK1LYdnzw3i%2FGT2%20Comparison.svg?alt=media&#x26;token=446bcf60-5e26-4fe2-91e7-f390e6f6cde1" alt=""><figcaption></figcaption></figure>

### GT2 Pulleys

<div data-full-width="false"><figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FkVkpVS3nzVzivVYXHgcy%2FGT2%20Pulleys%20Width.svg?alt=media&#x26;token=0da3c3b4-9782-4ea4-afbc-807ea0fe7617" alt=""><figcaption></figcaption></figure></div>

<table><thead><tr><th>Bore</th><th>Width</th><th># of Teeth</th><th data-hidden># of Teeth</th><th data-hidden>Width</th></tr></thead><tbody><tr><td>8mm SplineXS</td><td>9mm/15mm</td><td>16</td><td>16</td><td>9mm/15mm</td></tr><tr><td>8mm Key</td><td>15mm</td><td>16</td><td></td><td></td></tr><tr><td>Falcon Spline</td><td>9mm/15mm</td><td>16</td><td>16</td><td></td></tr><tr><td>RS550 Motor/RS775 Motor/BAG Motor</td><td>9mm</td><td>12</td><td>12</td><td></td></tr><tr><td>1/2" Hex</td><td>9mm</td><td>24, 36, 48, 60</td><td>24, 36, 48, 60</td><td></td></tr></tbody></table>

{% hint style="info" %}
These pulleys are compatible with GT2 and GT3 belts.
{% endhint %}

### GT2 Belts

<table><thead><tr><th width="144">Width</th><th># of Teeth</th></tr></thead><tbody><tr><td>9mm</td><td>45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 140, 150, 160, 170, 180, 190, 200</td></tr></tbody></table>

## Plastic HTD Timing Pulleys <a href="https://wcproducts.com/collections/belts-chain-gears/products/plastic-htd-timing-pulleys" class="button primary" data-icon="list">Product Page</a><a href="https://app.gitbook.com/o/jQ1oA79yIGzA6fO0uMWk/s/xDLhjhfYDC5WTf4NxNpL/" class="button primary" data-icon="book-open">Manual</a>

The WCP Plastic Pulleys are designed to minimize weight while maintaining strength and performance. Individual pulley slices can be combined with a 9mm pulley to create a 15mm wide pulley, giving teams added flexibility when configuring belt-driven mechanisms.

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2Fat7JkuBG5qm00wmiNjRs%2FPlastic%20HTD%20Timing%20Pulleys.svg?alt=media&#x26;token=a81760e4-b9f6-41c9-8948-dd08020cb2d7" alt=""><figcaption></figcaption></figure>

<table><thead><tr><th width="249">Width</th><th width="249">Bore</th><th># of Teeth</th></tr></thead><tbody><tr><td>9mm</td><td>1/2" Hex</td><td>24</td></tr><tr><td>5/16"</td><td>1/2" Hex</td><td>24</td></tr></tbody></table>

## HTD Belts and Pulleys

Synchronous timing belts are lighter and more efficient than chain. Once set up, they require no tensioning or adjustment. The HTD profile is ideal for *FIRST* ® Robotics Competition applications - its deep tooth profile allows it to better handle high reversing loads, such as those found in an *FIRST* ® Robotics Competition drivetrain.

{% hint style="info" %}
All HTD Pulleys will now be clocked and engraved. An alignment notch has also been added to help with clocking multiple items together during assembly.
{% endhint %}

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FbogTQfUqwGnKOH08CTon%2FHTD%20comparison.svg?alt=media&#x26;token=cc7f971e-6905-4482-9b4a-eda22af46523" alt=""><figcaption></figcaption></figure>

### HTD Pulleys <a href="https://wcproducts.com/collections/belts-chain-gears/products/htd-timing-pulleys" class="button primary" data-icon="list">Product Page</a>

<figure><img src="https://1911150060-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FByQLBt0bw4wTa9DDV1kH%2Fuploads%2FEDKRC541UP0hwH9sqQtl%2FHTD%20Pulleys.svg?alt=media&#x26;token=205de79b-1e83-426f-b057-cdad55df2beb" alt=""><figcaption></figcaption></figure>

<table><thead><tr><th width="249">Width</th><th width="249">Bore</th><th># of Teeth</th></tr></thead><tbody><tr><td>9mm/15mm</td><td>8mm SplineXS</td><td>12, 14, 16, 18</td></tr><tr><td>9mm/15mm</td><td>8mm Key, Falcon</td><td>12, 18</td></tr><tr><td>9mm</td><td>1/2" Hex</td><td>15, 18, 20, 24, 30, 36</td></tr><tr><td>15mm</td><td>1/2" Hex</td><td>15, 18, 20, 24, 30, 36</td></tr></tbody></table>

### HTD Belts <a href="https://wcproducts.com/collections/belts-chain-gears/HTDBelts" class="button primary" data-icon="list">Product Page</a>

<table><thead><tr><th width="249">Width</th><th># of Teeth</th></tr></thead><tbody><tr><td>9mm</td><td>30, 35, 40, 43, 45, 50, 53, 55, 60, 64, 65, 70, 75, 80, 85, 90, 95, 100, 104, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 210, 220, 225, 230, 240, 250, 260, 270, 280, 290, 300</td></tr><tr><td>9mm Double Sided</td><td>100, 125, 150, 175, 200, 250, 300</td></tr><tr><td>15mm</td><td>30, 35, 40, 45, 50, 55, 60, 64, 65, 70, 75, 80, 85, 90, 95, 100, 104, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 210, 220, 225, 230, 240, 250, 260, 270, 280, 290, 300</td></tr><tr><td>15mm Double Sided</td><td>100, 125, 150, 175, 200, 250, 300</td></tr><tr><td>18mm</td><td>34ft</td></tr><tr><td>15mm Rubber Coated</td><td>30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300</td></tr></tbody></table>


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