Apachi

Apachi V 1.0
(Highlight text)
Year Of Creation	2019-2020
Versions
Current Version	V 1.0
Update Year	2019-2020
Wins/Losses	0/2
Information and Statistics
Weight Class	Hobbyweight
Weapon Class	Bent Bar/Overhead Bar
Combined Wins/Losses	0/2
Weapon Speed	Around 800?
Other	Won the 12lb rumble

Apachi is the first iteration of a 18 lb Bent Bar Shuffler. The purpose of this guide is to explain all of the reasoning behind the design decisions during the creation of Apachi. This guide will go in depth on why certain designs were chosen as well as explaining some of the calculations used to support those decisions.

Competitions

Motorama 2020

• Results:
  • Bracket Style:
    • [(Video Link) (result) vs (opponent)]
      • (notes)
      • (observations))

Version

Apachi V1.0

Created by: (Names of Builders/Group Members of aforementioned version of bot)

Drive Motors	Turnigy 540L V-Spec Inrunner 810kv
Drive Motor Controllers	HobbyKing Brushless Car ESC 2S-4S
Weapon Motor	Scorpion SII-4025-520KV
Weapon Motor Controllers	YEP 100A (2~6S) SBEC Brushless Speed Controller
Receiver	Hobby King 2.4Ghz Receiver 6Ch V2
Remote Control	Hobby King 2.4Ghz 6Ch Tx and Rx V2
Battery	2x Turnigy 2200mAh 4S 30C Lipo Pack
(OTHER:)	MS-05 Switch

Chassis

Design Overview

The chassis for Apachi had to solve a couple of problems. First, it had to be contained within the bounding circle made by the bent bar weapon. Second, the chassis needed to securely hold the weapon due to the high loads from our large moment arm. Third, we wanted to have easy access to the foot modules in order to troubleshoot problems.

Design Decisions

• For the first problem, the geometry of our feet had a large impact on our chassis shape. our feet were long straight lines that we wanted as far as we could get to the outside. We considered making a plus shaped chassis to maximize our space, but were concerned it would increase our wobble which would be especially bad because of our weapon hitting the ground. We chose a rectangular design.

• In order to secure the weapon, we added two steel supporting bars to hold the weapon shaft. We don't have much evidence that this worked because our weapon snapped every time we hit something full force, but these supports did not fail.

• In order to access our feet modules, we considered two options. The first option was to create a modular bounding box that could easily connect or be replaced. This would require a more complex interface between the module and the internal drive motor and geartrain. The main benefit of this is the plug-and-play nature leading to easy swaps. The second option, which we opted for, was to primarily focus on the side plates being easily removable and the feet accessible from there. While this meant the robot would be down whenever we needed to access the feet, it simplified the rest of the design and number of parts.

Evaluation

Some main chassis takeaways from our experience were:

• Pre-planning electronics could have saved a lot of pain
• Integrating a center bar with a shuffler heavily constrains design
• Using nonstandard dimensions to save a tiny amount of weight is annoying during machining
• It is worth double checking electronics hole dimensions

Drive Assembly

Overview

Apachi’s Drive system was a shuffler drive. This consisted of 2 symmetrical shuffler modules. Each shuffler module consisted of 6 HDPE feet with bearings pressed into them, and a hex shaft with aluminum cams clocked at 60 degree intervals. The feet were pressed onto the cams to create a cascading motion when the camshaft was rotated. The camshaft was driven by a spur gear and a pinion attached to an inrunner motor. Both sides were symmetrical such that there were always 2 feet on the ground at any given point in time.

Design Decisions

The decision to make a shuffler system was in order for Battlebots as a whole to gain more knowledge of this new drive and take advantage of the 50% weight bonus, along with the traction advantage of more ground surface area. The decision to make 6 feet per side was due to the thought that producing identical cams with hex profiles would be the easiest way to manufacture the system. The feet were made of HDPE, the cams were made of aluminum, and the shaft was made of steel. The cams were designed to be a failure point, the thought being that their hex profiles would be rounded by the turning of the shaft. Because of this, the shuffler modules were designed to be easy to assemble. By taking off the outer side plate, the shuffler module is accessible as a stack of feet/spacers on the 2 shafts.

Calculations

[Link to spreadsheet] Our calculations showed that a 4 foot design would be very slightly better, but we opted for the 6 foot design because we thought that the hex shaft would be easier to machine

Changes/Improvements

• (List of suggested improvements/changes, 1 per bullet point)

See also

• [(link to other bot made this year) (Name of other bot made this year)]

Notes:

(random joke, optional)

Naming Inspiration: It kinda looks like a helicopter

(Names of original builders)