{"id":907,"date":"2025-10-01T13:25:03","date_gmt":"2025-10-01T20:25:03","guid":{"rendered":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/?page_id=907"},"modified":"2025-10-16T15:01:05","modified_gmt":"2025-10-16T22:01:05","slug":"the-drivetrain","status":"publish","type":"page","link":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/the-drivetrain\/","title":{"rendered":"The Drivetrain"},"content":{"rendered":"<div  class='flex_column av-8pujf-1673edd11c84b53d189e01eaa9289422 av_one_full  avia-builder-el-0  avia-builder-el-no-sibling  first flex_column_div  '     ><section  class='av_textblock_section av-mg8fqqe7-3aa99fbe8dde1136ef21464b59091865 '   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/CreativeWork\" ><div class='avia_textblock'  itemprop=\"text\" ><h1>The Drivetrain<\/h1>\n<hr \/>\n<h2>1. Introduction<\/h2>\n<p><span style=\"font-weight: 400;\">The drivetrain is the most important part of your robot. It determines how fast you can move, how much you can push, and how reliably you can execute your strategy. Getting the right motor setup, speed, and build quality first makes everything else easier. This section will cover the essentials to help you design a drive that is fast, strong, and consistent.<\/span><\/p>\n<h2>2. Power &amp; Motors<\/h2>\n<p><span style=\"font-weight: 400;\">Your V5RC robot is <\/span><b>limited to 88W of power<\/b><\/p>\n<ul>\n<li aria-level=\"1\"><b>Use all 88W! <\/b><span style=\"font-weight: 400;\">Motor power is vital, and since the drivetrain is the most important part of your robot, give it as much power as possible while still leaving enough for scoring mechanisms. For most teams and seasons, a 66W drive provides a good balance.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">VEX motors come in <\/span><b>11W<\/b><span style=\"font-weight: 400;\"> and <\/span><b>5.5W<\/b><span style=\"font-weight: 400;\"> versions. For drivetrains, you should almost always use <\/span><b>11W motors<\/b><span style=\"font-weight: 400;\">\u00a0<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Avoid stacking many 5.5W motors instead of using fewer 11W ones. More motors = more weight, friction, and complexity.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Below are some possible configurations:<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><b>Drive Wattage<\/b><\/td>\n<td><b>Motors<\/b><\/td>\n<td><b>Notes<\/b><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">66W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">6 \u00d7 11W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Standard; fast, reliable<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">44W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">4 \u00d7 11W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Slower; less common for competitive\/experienced teams<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">55W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Mixed (4 \u00d7 11W, 2 \u00d7 5.5W)<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Rare; niche<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">88W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">8x 11W<\/span><\/td>\n<td><span style=\"font-weight: 400;\">Rarely viable, leaving no motor power for scoring mechanisms.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th><b>Think<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Before deciding on motor count or drive wattage, consider:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Research past games:<\/b><span style=\"font-weight: 400;\"> How much drive power did competitive robots use? Did they rely on pneumatics or other systems to have this drive power left over?<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Complexity check:<\/b><span style=\"font-weight: 400;\"> If you think you need more than 22W left for other systems, is your design too complicated?<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Power sharing:<\/b><span style=\"font-weight: 400;\"> Can mechanisms serve multiple purposes to save motor power?<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Prioritize the drive:<\/b><span style=\"font-weight: 400;\"> The drivetrain is the most important system. How can you keep it powerful enough to maneuver quickly and score efficiently, while still leaving enough power for manipulation and occasional defense?<\/span><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>3. Gear Ratios and Speed<\/h2>\n<h3><b>3.1 How Gear Ratios Work<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Gear ratios control the tradeoff between speed and torque in your drivetrain. The ratio is written as <\/span><i><span style=\"font-weight: 400;\">driving gear teeth : driven gear teeth.<\/span><\/i><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-912\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Ratios-Img.png\" alt=\"\" width=\"235\" height=\"154\" \/><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">If the driven gear is larger (fewer rotations), you get <\/span><b>more torque, less speed<\/b><span style=\"font-weight: 400;\">.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">If the driven gear is smaller (more rotations), you get <\/span><b>more speed, less torque<\/b><span style=\"font-weight: 400;\">.<\/span><\/li>\n<\/ul>\n<table>\n<thead>\n<tr>\n<th><b>Example<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">A 12T gear driving a 36T gear = 1:3 ratio. The output turns slower, but has 3\u00d7 the torque.<\/span><\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-913\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Input-Output-Diagram.png\" alt=\"\" width=\"501\" height=\"228\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Input-Output-Diagram.png 501w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Input-Output-Diagram-300x137.png 300w\" sizes=\"auto, (max-width: 501px) 100vw, 501px\" \/><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Flip it: A 36T driving a 12T = 3:1 ratio. The output turns faster, but has only 1\/3 the torque.<\/span><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th><b>Note<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><b>Gear Direction: <\/b><span style=\"font-weight: 400;\">Gears can reverse rotation, so make sure all wheels on your drive spin the same way. A common solution is to alternate motor-driving gears and wheel-driving gears along the drivetrain.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-999\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Direction-Diagram-1.png\" alt=\"\" width=\"1030\" height=\"335\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Direction-Diagram-1.png 1030w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Direction-Diagram-1-300x98.png 300w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Direction-Diagram-1-768x250.png 768w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Gear-Direction-Diagram-1-705x229.png 705w\" sizes=\"auto, (max-width: 1030px) 100vw, 1030px\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th><b>Resources<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">(See this resource for a deeper dive into the math behind gear ratios.)<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a href=\"https:\/\/wiki.purduesigbots.com\/hardware\/design-fundamentals\/gear-ratios\"><span style=\"font-weight: 400;\">Gear Ratios | Purdue SIGBots Wiki<\/span><\/a><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th><b>Remember<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">A drivetrain that\u2019s \u201ctoo fast\u201d overheats and stalls. A drivetrain that\u2019s \u201ctoo slow\u201d can\u2019t keep up in matches.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><b>3.2 Wheel Size and Linear Speed<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Wheel diameter also affects speed. Larger wheels = more distance per rotation (faster linear speed), but less torque. Smaller wheels = less distance per rotation (slower linear speed) but higher torque.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-917\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Wheel-Size-Diagram.png\" alt=\"\" width=\"569\" height=\"356\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Wheel-Size-Diagram.png 569w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Wheel-Size-Diagram-300x188.png 300w\" sizes=\"auto, (max-width: 569px) 100vw, 569px\" \/><\/p>\n<table>\n<thead>\n<tr>\n<th><b>Best Practices (Opinion)<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Target speed for a 66W drive: 5.1\u20137.2 ft\/s<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Your drivetrain should be as fast as possible while still meeting key goals:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Support the weight of your robot + this season\u2019s game objects<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Survive a full match without overheating (even with defense\/contact)<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Remain controllable with limited driver practice<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Why this range?<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Faster than ~7.2 ft\/s \u2192 motors overheat regardless of how light you build (even minimal robots weigh 9+ lbs). Control also becomes unrealistic without extreme driver practice.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Slower than ~5.1 ft\/s \u2192 you\u2019ll be outpaced. VEX games favor offense, so overly slow robots lose opportunities.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">This range comes from the common competitive weight range (9\u201318 lbs) and the limits of what gearings are realistically achievable with VEX parts. It isn\u2019t restrictive, it covers the full spectrum of successful drives, while filtering out extremes.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div><\/section><br \/>\n<div  class='togglecontainer av-mg9omhyh-100abcfcdca28aa467bb71d224c26854  avia-builder-el-2  el_after_av_textblock  el_before_av_textblock  toggle_close_all' >\n<section class='av_toggle_section av-mg9omgfe-4630fe0d8a1c153d7adc36ae2076ca36'  itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/CreativeWork\" ><div role=\"tablist\" class=\"single_toggle\" data-tags=\"{All} \"  ><p id='toggle-toggle-id-1' data-fake-id='#toggle-id-1' class='toggler  av-title-above '  itemprop=\"headline\"  role='tab' tabindex='0' aria-controls='toggle-id-1' data-slide-speed=\"200\" data-title=\"Further Reading\" data-title-open=\"\" data-aria_collapsed=\"Click to expand: Further Reading\" data-aria_expanded=\"Click to collapse: Further Reading\">Further Reading<span class=\"toggle_icon\"><span class=\"vert_icon\"><\/span><span class=\"hor_icon\"><\/span><\/span><\/p><div id='toggle-id-1' aria-labelledby='toggle-toggle-id-1' role='region' class='toggle_wrap  av-title-above'  ><div class='toggle_content invers-color '  itemprop=\"text\" ><p><b>Weight prediction\/testing<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Test method:<\/b><span style=\"font-weight: 400;\"> Build a basic drive and add weight until it matches your needs (e.g. push X lbs without overheating for a match). Record ratio of weight \u2192 speed.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>CAD method:<\/b><span style=\"font-weight: 400;\"> Use a part weight spreadsheet + your test data to estimate max viable speed.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">This isn\u2019t perfect (friction varies), but it\u2019s practical for early validation.<\/span><\/p>\n<p><b>One Key Issue<\/b><b><br \/>\n<\/b><span style=\"font-weight: 400;\">If you CAD your whole robot before choosing a drivetrain, you risk designing around wrong speed\/torque assumptions. Because the drivetrain sets the foundation (size, motor placement, gearing, layout), a bad choice can force redesigns later.<\/span><\/p>\n<p><b>Takeaway<\/b><b><br \/>\n<\/b><span style=\"font-weight: 400;\">For most competitive robots, a <\/span><b>66W drive at 5.1\u20137.2 ft\/s<\/b><span style=\"font-weight: 400;\"> balances power, control, and weight. Start here, then optimize after your first tournaments.<\/span><\/p>\n<p><b>Why this range works<\/b><b><br \/>\n<\/b><span style=\"font-weight: 400;\">It reflects the real weight of competitive robots (9\u201318 lbs) and the tradeoffs between overheating, driver control, and pacing. It\u2019s broad enough for flexibility but avoids speeds that are clearly too fast or too slow.<\/span><\/p>\n<\/div><\/div><\/div><\/section>\n<\/div><br \/>\n<section  class='av_textblock_section av-mg9olrs2-0885cd0a4ed0215acbb9aaa839971ecc '   itemscope=\"itemscope\" itemtype=\"https:\/\/schema.org\/CreativeWork\" ><div class='avia_textblock'  itemprop=\"text\" ><table>\n<thead>\n<tr>\n<th><b>Resources<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Use this<\/span><a href=\"https:\/\/docs.google.com\/spreadsheets\/d\/1S0xQm0eDGq3fbDsam8x4ZP_xMLXirXvMVMGXvjNWbxc\/edit?gid=639035874&amp;utm_source=chatgpt.com#gid=639035874\"> <span style=\"font-weight: 400;\">Drive Speed Calculator<\/span><\/a><span style=\"font-weight: 400;\"> to <\/span><b>check your designs linear speed before building<\/b><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Basic catalog of drive possibilities (5.1\u20137.2 ft\/s = 61.2\u201386.4 in\/s): <\/span><a href=\"https:\/\/www.vexforum.com\/t\/catalogue-of-drive-gearings\/109498\"><span style=\"font-weight: 400;\">https:\/\/www.vexforum.com\/t\/catalogue-of-drive-gearings\/109498<\/span><\/a><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Part Weights: <\/span><a href=\"https:\/\/docs.google.com\/spreadsheets\/d\/1tbYlvjHXo4a-BVfLfPR7c9ei_yfzVoc1QQSPSKcCb7E\/edit?gid=1556734328#gid=1556734328\"><span style=\"font-weight: 400;\">https:\/\/docs.google.com\/spreadsheets\/d\/1tbYlvjHXo4a-BVfLfPR7c9ei_yfzVoc1QQSPSKcCb7E\/edit?gid=1556734328#gid=1556734328<\/span><\/a><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th><b>Important Note<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">The recommended <\/span><b>5.1\u20137.2 ft\/s speed range<\/b><span style=\"font-weight: 400;\"> applies to <\/span><b>66W drives<\/b><span style=\"font-weight: 400;\">. A 44W drive is a possible alternative, but it requires a different approach:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">You accept slower movement, either because you\u2019re new to driving or the field has limited open space.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Your design needs more than 22W for other systems and you don\u2019t have pneumatics.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Your clever mechanisms require prioritizing motor power elsewhere.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">These are all valid design considerations, but they are not the norm and should be justified. The 66W drive remains the standard for experienced teams.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>4. Chassis Layout &amp; Dimensions<\/h2>\n<h3><b>4.1 Drive Gap<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">The <\/span><b>drive gap<\/b><span style=\"font-weight: 400;\"> is the spacing between the inside and outside C channels that support the wheels and gears in between.<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td>\n<h3><b>Recommended<\/b><\/h3>\n<p><b>1.5\u20132 inches<\/b><span style=\"font-weight: 400;\"> (3\u20134 holes wide)<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">1.5\u201d is the minimum possible with anti-static omni wheels.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Smaller gap = stronger structure + more compact robot = better maneuverability.<\/span><\/li>\n<\/ul>\n<p><b>Where to add a diagram:<\/b><span style=\"font-weight: 400;\"> Show CAD examples of a 1.5\u201d vs. 2\u201d drive gap.<\/span><\/p>\n<h3><b>Important<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">The drive gap should align with C-channel holes in 0.5\u201d increments. This ensures cross braces fit perfectly across the width of the drive, keeping the chassis square. Avoid arbitrary spacing that prevents full-width bracing.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Example of a drive with a 3 hole (1.5\u201d) wide drive gap <\/span><b>(see red rectangle)<\/b><span style=\"font-weight: 400;\"> on this 450RPM 3.25\u201d drive CAD:<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-919\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Layout-Diagram.png\" alt=\"\" width=\"1000\" height=\"438\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Layout-Diagram.png 1000w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Layout-Diagram-300x131.png 300w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Layout-Diagram-768x336.png 768w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Layout-Diagram-705x309.png 705w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/h3>\n<h3><b>4.2 Cross Bracing &amp; Rigidity<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">A drivetrain that flexes will skip gears, become un-square and lose consistency. To prevent this:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Use <\/span><b>at least 2 full cross braces<\/b><span style=\"font-weight: 400;\">, placed apart for maximum strength.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Be sure to apply the Boxing building technique (see previous tab)<\/span><\/li>\n<\/ul>\n<table>\n<thead>\n<tr>\n<th><b>Attention<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Without bracing, your drive can twist in matches or even during assembly. Once it bends, it\u2019s nearly impossible to fix mid-season, so add full cross braces from the start.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<tbody>\n<tr>\n<td><strong>Example of a well braced chassis:<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-920\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Part.png\" alt=\"\" width=\"585\" height=\"434\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Part.png 585w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Chassis-Part-300x223.png 300w\" sizes=\"auto, (max-width: 585px) 100vw, 585px\" \/><\/p>\n<p><b>Image Credit:<\/b><span style=\"font-weight: 400;\"> Harvard West Lake. (2022, July 24). <\/span><i><span style=\"font-weight: 400;\">1 <a href=\"https:\/\/www.youtube.com\/watch?v=BgPrhM-p79w\">ChassisPart1 Video YouTube<\/a><\/span><\/i><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>5. Build Practices for Reliability<\/h2>\n<p><span style=\"font-weight: 400;\">Here\u2019s how the core build concepts apply to drivetrains:<\/span><\/p>\n<h3><b>5.1 Screw joints<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Use <\/span><b>screw joints instead of shafts whenever possible<\/b><span style=\"font-weight: 400;\">. Shafts should only be used for gears\/wheels directly powered by a motor. Shaft joints = sloppy, high-friction, and unreliable.<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><i><span style=\"font-weight: 400;\">WATCH THIS VIDEO: <\/span><\/i><a href=\"https:\/\/youtu.be\/K218QdJ-IAs?si=5z1P4We7aYF-T5_c\"><i><span style=\"font-weight: 400;\" data-rich-links=\"{\">VEX Build Masterclass #1 &#8211; Screw Joints<\/span><\/i><\/a><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><i><span style=\"font-weight: 400;\">Drive relevant part of the video starts at 8:10<\/span><\/i><\/li>\n<\/ul>\n<div class='avia-iframe-wrap'><iframe loading=\"lazy\" title=\"VEX Build Masterclass #1 - Screw Joints\" width=\"1500\" height=\"844\" src=\"https:\/\/www.youtube.com\/embed\/K218QdJ-IAs?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h4><span style=\"font-weight: 400;\">Non-Structural Screw Joint<\/span><\/h4>\n<p><span style=\"font-weight: 400;\">If you have a long shoulder screw (2.25\u201d or 2.5\u201d), you can omit the first bearing as shown on the right image below. Both the <\/span><b>bearing<\/b><span style=\"font-weight: 400;\"> and a <\/span><b>shoulder <\/b><span style=\"font-weight: 400;\">help <\/span><b>center the screw<\/b><span style=\"font-weight: 400;\"> to <\/span><b>perfect spacing \u2192 improves friction.<\/b><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-923\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-scaled.png\" alt=\"\" width=\"922\" height=\"237\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-scaled.png 2560w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-300x77.png 300w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-1030x265.png 1030w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-768x197.png 768w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-1536x395.png 1536w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-2048x526.png 2048w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-1500x385.png 1500w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/Non-Structural-Screw-Joint-705x181.png 705w\" sizes=\"auto, (max-width: 922px) 100vw, 922px\" \/><\/p>\n<h4><span style=\"font-weight: 400;\">Structural Screw Joint<\/span><\/h4>\n<p><span style=\"font-weight: 400;\">Nuts are tightened on both sides of the inner channel. This way the screw joint is also a <\/span><b>structural <\/b><span style=\"font-weight: 400;\">support, though it is <\/span><b>heavier <\/b><span style=\"font-weight: 400;\">and <\/span><b>harder to assemble<\/b><span style=\"font-weight: 400;\"> or find room for the nuts.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-925\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/structural-screw-joint.png\" alt=\"\" width=\"465\" height=\"202\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/structural-screw-joint.png 389w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/structural-screw-joint-300x130.png 300w\" sizes=\"auto, (max-width: 465px) 100vw, 465px\" \/><\/p>\n<h4><span style=\"font-weight: 400;\">Standoff Screw Joints<\/span><\/h4>\n<p><span style=\"font-weight: 400;\">If the gap between your channels is larger such as on a 4 wide drive gap with \u2d4e\u2d4e orientation, you may choose to use a standoff mounted directly to the outer drive channel, and another screw threaded into it from the opposite direction. An additional Keps nut to lock the standoff in place is optional.<\/span><span style=\"font-weight: 400;\"><br \/>\n<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-926\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/standoff-screw-joints.png\" alt=\"\" width=\"924\" height=\"168\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/standoff-screw-joints.png 924w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/standoff-screw-joints-300x55.png 300w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/standoff-screw-joints-768x140.png 768w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/standoff-screw-joints-705x128.png 705w\" sizes=\"auto, (max-width: 924px) 100vw, 924px\" \/><\/p>\n<h3><b>5.3 Squaring<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Use bearings, retainers, or shoulder screws to keep your drive straight. If your drive frame isn&#8217;t square, the gears may skip under load and introduce lots of friction.<\/span><\/p>\n<table>\n<tbody>\n<tr>\n<td><i><span style=\"font-weight: 400;\">WATCH THIS VIDEO: <\/span><\/i><a href=\"https:\/\/www.youtube.com\/watch?v=yC_6j7vawfk&amp;t=4s\"><i><span style=\"font-weight: 400;\" data-rich-links=\"{\">VEX Build Masterclass #3 &#8211; Squaring<\/span><\/i><\/a><\/p>\n<div class='avia-iframe-wrap'><iframe loading=\"lazy\" title=\"VEX Build Masterclass #3 - Squaring\" width=\"1500\" height=\"844\" src=\"https:\/\/www.youtube.com\/embed\/yC_6j7vawfk?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\" referrerpolicy=\"strict-origin-when-cross-origin\" allowfullscreen><\/iframe><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><b>5.4 Misc Build Practice<\/b><\/h3>\n<p><b>Spacing<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Keep about one washer of space between components on a shaft or screw joint.<\/b><span style=\"font-weight: 400;\"> Too little spacing adds friction, too much causes wobble or catching.\u00a0<\/span><\/li>\n<\/ul>\n<p><b>Gear-to-wheel connections<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Since your wheels are on screw joints, the gear beside it on the screw joint needs to directly attached to the wheel for the two to spin together<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Use at least <\/span><b>2 screws<\/b><span style=\"font-weight: 400;\"> when attaching a gear to a wheel on a screw joint. One screw will loosen; two will stay solid. More than two adds unnecessary weight.<\/span><\/li>\n<\/ul>\n<p><b>Bearings for Shafts<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Every shaft needs 2 points of support. If it goes into a motor, the motor counts as one bearing.\u00a0<\/span>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">For most drives this means bearing on outer drive channel<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<table>\n<thead>\n<tr>\n<th><b>Attention<\/b><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Cutting corners here doesn\u2019t just make the drive weaker, it makes it unpredictable. That\u2019s the last thing you want in a match.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>6. Control &amp; Performance Considerations<\/h2>\n<h3><b>6.1 Clearance<\/b><\/h3>\n<p><span style=\"font-weight: 400;\">Wheel gaps and gear placement affect barrier crossing. Large gears between wheels can hang below the chassis and catch, especially in games like <\/span><i><span style=\"font-weight: 400;\">Push Back<\/span><\/i><span style=\"font-weight: 400;\">. Using blue cartridges with external reductions keeps the large gear at the wheel and a smaller gear between wheels, improving clearance. Wheel count matters too: 4-wheel drives leave long exposed gear runs, while 6\u20138 wheel drives break them up, shielding gears and smoothing obstacle crossing.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Example: a 333RPM green-cartridge drive with large gears protruding between wheels shows poor clearance.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-927\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/clearance-diagram.png\" alt=\"\" width=\"614\" height=\"149\" srcset=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/clearance-diagram.png 614w, https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/clearance-diagram-300x73.png 300w\" sizes=\"auto, (max-width: 614px) 100vw, 614px\" \/><\/p>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">If the game requires clearance, avoid oversized gears between wheels (Use blue cartridges and gear down!) and consider wheel count to minimize gear exposure.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><b>6.2 Cartridge Choice<\/b><\/h3>\n<p><b>Cartridge choice can directly affect drivetrain efficiency<\/b><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Friction:<\/b><span style=\"font-weight: 400;\"> Cartridges closer to the motor\u2019s native 3600 rpm have fewer internal reductions \u2192 less friction. The 600 rpm blue cartridge is lowest-friction compared to green (200 rpm) and red (100 rpm).<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Slop:<\/b><span style=\"font-weight: 400;\"> Slop is the \u201cwiggle\u201d before the motor engages. External gearing down reduces slop, while gearing up amplifies it. Blue, usually geared down, minimises this slop. Green\/red often needs gearing up, which adds play within the gearing and worsens autonomous consistency.<\/span><\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-928\" src=\"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-content\/uploads\/sites\/35\/2025\/10\/cartridge-choice-img.png\" alt=\"\" width=\"130\" height=\"136\" \/><\/p>\n<table>\n<tbody>\n<tr>\n<td><span style=\"font-weight: 400;\">Blue is usually best, it minimizes friction, reduces slop, improves clearance, and gives reliable autos. Green or red make sense only for very low rpm or packaging\/materials constraints.<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3><b>6.3 Maneuverability vs. Stability<\/b><\/h3>\n<table>\n<tbody>\n<tr>\n<td><b>Compact base (narrow, short wheelbase)<\/b><\/td>\n<td><b>Wider base (larger wheelbase)<\/b><\/td>\n<\/tr>\n<tr>\n<td>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Fast turning, small footprint, more maneuverable, easier to move around quickly.<\/span><\/li>\n<\/ul>\n<\/td>\n<td>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">More stable, harder to tip, better at resisting defense.<\/span><\/li>\n<\/ul>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>7. Conclusion<\/h2>\n<p><span style=\"font-weight: 400;\">A competitive drivetrain comes down to four main factors:<\/span><\/p>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Enough power<\/b><span style=\"font-weight: 400;\"> \u2013 Typically 44\u201366W, most often 6 \u00d7 11W motors.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Balanced speed<\/b><span style=\"font-weight: 400;\"> \u2013 Target linear speeds of 5.1\u20137.2 ft\/s for typical robot weights with a 66W drive.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Strong, rigid construction with minimized friction<\/b><span style=\"font-weight: 400;\"> \u2013 Screw joints, cross braces, and proper squaring ensure durability and consistent performance.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Challenge-specific considerations<\/b><span style=\"font-weight: 400;\"> \u2013 adjust your drivetrain for game-specific factors like clearance over barriers or fitting key game objects.<\/span>\n<ol>\n<li style=\"font-weight: 400;\" aria-level=\"2\"><span style=\"font-weight: 400;\">EX: Clearance to go over the barrier in push back and space to fit a mobile goal in high stakes<\/span><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<div style=\"background-color: #2358ad; color: white; padding: 7px 15px; border-radius: 4px; margin-top: 15px; text-align: right;\">The content for this page was provided by <strong style=\"color: white;\">Zane Radawiec.<\/strong><\/div>\n<\/div><\/section><\/p><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":9,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"tags":[],"class_list":["post-907","page","type-page","status-publish","hentry"],"publishpress_future_action":{"enabled":false,"date":"2026-04-15 22:45:20","action":"change-status","newStatus":"draft","terms":[],"taxonomy":"post_tag","extraData":[]},"publishpress_future_workflow_manual_trigger":{"enabledWorkflows":[]},"_links":{"self":[{"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/pages\/907","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/comments?post=907"}],"version-history":[{"count":20,"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/pages\/907\/revisions"}],"predecessor-version":[{"id":1028,"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/pages\/907\/revisions\/1028"}],"wp:attachment":[{"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/media?parent=907"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.comoxvalleyschools.ca\/robotics71\/wp-json\/wp\/v2\/tags?post=907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}