AM14U2 Upgraded to 6″ VEXpro Traction Wheels

The Recycle Rush Scoring Platform features one of the sharpest approach angles in recent FRC history.  If traversing this short but challenging bump is part of your team’s strategy, then proper drivetrain analysis, design, and testing are crucial to ensuring a smooth transition.

With a few minor modifications, the 2015 Kit of Parts drivetrain can be easily adjusted to use VEXpro 6″ Traction Wheels and belts. This upgrade allows your drivetrain’s wheels to maintain full contact with the ground through its entire journey, reducing the risk of frame damage or becoming stuck.

Click here to download a CAD file (ZIP, 21 MB) of the upgraded drivetrain to visualize the changes, and keep an eye out for detailed instructional drawings and BOMs coming soon!

What is the -Simplest- Way to Move a Tote?

The goal of Build Blitz is, and has always been, to provide educational resources for medium-level or inexperienced teams who may need some additional help to get going.  The concepts explored thus far (4-bar stacker, linear elevator, and pinch claw) are solid subsystems that can combine with a variety of other systems to form a complete robot.  These are intended for teams looking to seed or be a solid pick by a seeded robot.

However, we wanted to know if we could go even simpler.  For teams just getting started with absolutely minimal resources, how can literally a few pieces of hardware be attached to a basic robot frame and still create a solid contributor to a qualification or playoff alliance?

The Passive Hook

Theory: Drag a Tote from the top using a passive hook.  The robot can drive up to a Tote in the Landfill and use its natural lip to drag it across the field.  To dislodge, the robot can either drive over the Scoring Platform (if its drivetrain allows) or just turn sideways and slide the hook off.  Angled sides of the rake will assist with this dismount.

Simple Tote Puller (top)  Simple Tote Puller (close)  Simple Tote Puller (front)

Testing: The prototype was built using three pieces of VEX EDR metal clamped to an existing drive base.  It ended up working very well, dragging the Tote along with ease when in the “long” orientation.  The “short” orientation did not work as well with this initial prototype; this will be something to work on for the next iteration.

The Plastic Slider

Theory: Slip a plastic sheet underneath the Tote and drive away with it. Since the Tote is sitting on top of the sheet, it now moves with the robot! To get the tote off, pull the ‘rug’ from underneath the tote.

Plastic Tote Slider

Testing: Similar to the hook, this was accomplished by clamping a spare Delrin sheet (though Lexan would also work) onto a pre-built drivetrain.  (Fans of FRC Team 148 may recognize the X009 concept used here). This test worked, but not as well as we would’ve liked.  The sheet actually had a smaller footprint than the Tote, meaning that the Tote occasionally caught the carpet and slipped off of the sheet.  The next version will feature a larger sheet (#MeasureOnceCutTwice), and we’ll also see how this theory applies to a Recycling Container.

These concepts are true applications of the KISS principle to Recycle Rush.  Admittedly, these robots (by themselves) will probably not be the highest-scoring robots at an event.  However, consistency is key in a helpful alliance partner, and the simplicity of these robots will be a primary contributor to that consistency.  This is a mindset that will help all teams (rookies or veterans) in their quest for Recycle Rush success.

Pinch Claw – Final Testing

We have our first functional prototype – the Pinch Claw! This morning the Pinch Claw group was finished building and ready to test their mechanism. First, the claw was tested grabbing a Tote and placing it on another Tote. Every time this was tested, the claw was successful.

Next, the claw was tested to grab a Container and place it onto a Tote. The initial tests were unsuccessful because the Container was too slick for the grabber to lift up. After adding friction material (in this case, black gum rubber) to the sides of the claw, there were no issues lifting and placing a Container on top of a Tote.

The complete Pinch Claw was made out of all VEXpro parts and weighs 4.5 lbs. The only complication the group ran into was having to add friction material (in this case, black gum rubber) to grip the Container. Prototyping is very important for every team – your mechanism doesn’t need to be attached to a fancy robot to see if it works or not. This Pinch Claw is very versatile, and can attach to almost any other mechanism to complete a robot.

Linear Elevator Concept

Tonight we got a chance to sit down and talk with Lead Engineer of the Linear Elevator group, Art Dutra. Take a look at how a linear elevator is an efficient way to score in Recycle Rush, and get a sneak preview of some NEW VersaFrame parts being created to help teams create an elevator of their own!

Linear Elevator on Field Linear Elevator Close-Up

A Simple Stacker Begins to Take Shape

This morning we got an update from the Simple Stacker group. They have been busy working on a 4-bar system to complete this crucial task. The goal for this mechanism is to be able to stack two totes on top of the step – ultimately using this to assist in gaining the Coopertition points.

Initially, a 4-bar was compared to a linear elevator system, but 4-bar required less precision alignment.  Additionally, even though both styles achieved the same goal, a 4-bar would be much simpler to design and construct.  As highlighted in Karthik’s Strategic Analysis, this is always an important factor to consider.

To reach this goal, the 4-bar stacker needs to be able to lift itself 19 inches from the ground up to reach the height of 2 Totes on top of the Step. It achieves this in early calculations.

Lift lowered grabbing bin  Lift Raised stacking on step

After completing the 2D prototype, the group decided on using a Mini CIM and a VersaPlanetary Gearbox to power this stacker. After some quick calculations, it looked like a Mini CIM would work perfectly.  Thanks to its compact size and ease of use, the VersaPlanetary Gearbox was the natural interface between the motor and the linkage.

Gearing calculations

The next step for the Simple Stacker group will be to turn their 2D “Crayola CAD” into a 3D CAD model for more testing. We can’t wait to see how their process continues to grow!

 

Day 1 – Great Strategy, Upgraded Drivetrains, and a Claw!

Day 1 of Build Blitz has come to a close, and we have some great beginnings to share.

Karthik’s Strategic Analysis

Karthik spent his first few days of this build season creating a strategic priority list for Recycle Rush.  His analysis weighs the difficulties of key tasks against their rewards – and the results may not be what you expect.

He then took to the internet in a live Google Hangout, where he and fellow Build Blitz team member Paul Copioli broke apart the game even further.  They even had time to answer some questions from the FRC community.

 

AM14U2 UpgradesAM14U2 3 CIM Ball Shifter Concept 1

This year’s Kit of Parts drivetrain, the AM14U2, provides a solid foundation for teams to get started with.  We’ve started developing some ways to take this drivetrain to the next level.  Our first version incorporates our most popular shifting gearbox, the 3 CIM Ball Shifter, and some 6″ wheels to help traverse the Scoring Platforms.  Guides and CAD models will be coming soon!

Drivetrain Design Guide & Philosophy

Today’s work on the Drivetrain Design Guide focused almost entirely on the Scoring Platforms.  This is the first game in a long time to have a bump in the field, especially one of this magnitude (16 degrees). It does a great job of bringing several key design requirements (like angle of attack or ground clearance) into the spotlight – teams need to be very careful about taking these into consideration when designing their drivetrains.

Recycle Rush Bump Transitions Recycle Rush Bump Clearance

Pinch Claw Design

Earlier today we posted a video of the first pinch claw prototype test.  By the end of the day, the initial CAD for that simple claw design had been completed.  It now picks up both Totes and Containers, using a linkage to lock into place when holding a game piece.  Tomorrow, we hope to build one out of VEXpro parts (other than Versa2x4) for final testing.

CAD Pinch Claw (Iso View) CAD Pinch Claw (Top View, Open) CAD Pinch Claw (Top View)  CAD Pinch Claw Holding Tote CAD Pinch Claw Holding Container

Check back tomorrow for updates on the Linear Elevator, the 2015-Specific Drivetrain, and some information on Simple Game Piece Manipulation!

 

Pinch Claw Test #1 – Keeping it Simple!

The Build Blitz team is hard at work on their seven areas of focus to help teams succeed at Recycle Rush.  The first to have a working prototype was the Claw group!

Simplicity and reliability were the overarching mentalities that drove this claw design. The goal for this particular test was to determine a jaw angle that would acquire Totes in an imperfect orientation. Simulating real-world conditions whenever possible can help to avoid a common frustration: seeing a prototype that worked excellently in a perfect lab environment fall short in the field.  This particular prototype succeeded in its goal of acquiring (and stacking) a misaligned Tote!

Wooden Claw Prototype - Surgical Tubing     IMG_0607 Claw Prototype 1 - Engineering Drawing

In its current design (which, to be fair, is three 2×4’s bolted together), the pinching claw can only pick up Totes.  However, with slight modifications, the team is confident that it will be able to pick up Recycling Containers in future versions.