How do I choose a pulley and belt?

Picking the Perfect Pulleys | GrabCAD Tutorials

Here’s a comprehensive guide to assist you in selecting suitable timing belts and pulleys for your robot. This tutorial is authored by Jacob Greenwood, one of the technical leads for the BattleBots program at UCLA under ASME.

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1. Step 1: Introduction to Pulleys

   Within the context of BattleBots, the use of timing belts and pulleys is prevalent. When selecting pulleys, several aspects need consideration, including the material type, tooth design, number of teeth, and belt width. While these specifications might appear complex, the key factor is ensuring compatibility in tooth style and belt width between both pulleys. Metal pulleys present a lower risk of stripping or breaking compared to plastic ones, although lightweight plastic options may also be beneficial.

2. Step 2: Where to Source Pulleys?

   Explore the SDP-SI website for a diverse range of pulleys.

   You will find various options, but for our specific needs, pulleys featuring one or two flanges are particularly advantageous. The flanges act as rims to keep the belts secure, although they do add to the overall radius of the pulley.

   Pulleys can be fastened to shafts using either set screws or Fairloc hubs. Fairloc hubs typically provide better security for round shafts, while set screws are ideal for D shafts. If you are directly connecting your pulley to your bearings (as in a shell spinner), opt for set screws instead of pulley-driving. However, the motor pulley should utilize a Fairloc hub. Only HTD and MXL pulleys are constructed from metal, equipped with double flanges and Fairloc hubs.

   Tip: Most vendors provide SolidWorks models for their components, so be sure to download the CAD files for integration into your final assembly. To open these files with SolidWorks, right-click and select ‘open with,’ then choose SolidWorks.

3. Step 3: Selecting the Right Pulleys

   You'll need two pulleys: one for the weapon motor and one for the weapon shaft.

   Typically, it's advisable to reduce the gearing by opting for a smaller motor pulley in comparison to your weapon. Selecting the smallest pulley available is a viable option, but if a larger one is chosen, ensure it's still smaller than the motor's canister. The diameter of your larger pulley should not exceed that of your weapon's inner diameter. In essence, the pulley must be completely hidden by the weapon when viewed from the side, to protect both the belt and pulley.

   Keep in mind that there are limited pulley sizes, and you should aim for one that is slightly less than your intended radius.

4. Step 4: Determining the Belt

   After finalizing the pulley sizes, the next task is to select the appropriate belt. Since your pulleys will likely differ in size, calculating the belt length can be tricky. Fortunately, there are online calculators available to simplify this process.

   Use this link to access 成钢.

   With the calculator, enter the specifications of your pulleys and your desired center distance. It will calculate a fitting belt that meets or exceeds your provided center distance. It is advisable to also check for the next smaller center distance which may suit your design better than the next larger option. Evaluate both belt choices to determine the most logical fit for your structure.

   This website is particularly helpful as it provides direct links to purchase the specific parts and also includes SolidWorks files for the belts. However, do not incorporate these files into your assembly since their design won't stretch around your virtual pulleys, potentially complicating your assembly. Remember to include them in your materials list for calculated weight and cost.

5. Step 5: Addressing Common Issues

   One frequent problem encountered with belts and pulleys is achieving proper tension. Constructing a system without a tensioning mechanism can lead to challenges, particularly in maintaining accurate tolerances. Ideally, you should attach the belt while at least one, and preferably both, pulleys are fixed in place. The belt should be placed over the pulley flanges and then made taut. This can be accomplished through two primary methods: applying pressure externally to the belt, or applying both internal and external pressure. The latter is generally more suitable for our needs, as it requires a mechanism that allows the motor to move back and forth while remaining stationary during operation.

   Additional details on this topic will be provided later...

6. Step 6: Brief Summary

   In summary, the steps outlined above provide a path for selecting two pulleys and a belt to effectively drive your robot's weapon motor system. Here are critical resources referenced throughout this guide:

   Pulley Vendor: https://www.sdp-si.com/products/Timing-Belt-Pulleys/index.php

   Online Belt Length Calculator: https://www.bbman.com/belt-length-calculator/

Essential Tips: Selecting the Optimal Belt for Your Pulleys