1241 THEORY6 2016 CAD and Prototype Resources Release

[Karthik]

Originally Posted by AdamHeard

Does anyone know of other vidoes/examples of such "low resource" full prototype robots this early in season?

Everyone knows about 254's 2014 presumably, but who else?

I found 1690's which was very good
https://www.youtube.com/watch?v=H49_6WVDT98

And also 5Poofs
https://www.youtube.com/watch?v=nrZVrQCQeqM

I've love to find some more, they're a great example of the process many teams should be doing.

Here are couple from 1114 in 2015.

https://www.youtube.com/watch?v=jH4n1X1Oz7c
https://www.youtube.com/watch?v=GkXFq2L5w1Q

[YawnYao]

You guys have an awesome robot this year. I have a few questions about the cad though.

How did you fabricate the camera mount? It looks like it's 3D printed but I can't tell how you printed it. Also, is the camera mount dampener rubber, and how did you make it?

Can you send me a link to the camera you use?

How did you mount the router? Was it just VHB taped up or did you use zipties to hold it up?

How did you make the pivot shaft inserts?

How do you guys accurately make long .5" tube axle standoffs? We ran into problems with making standoffs over 6" and had to use tape measures instead of calipers.

In the gorilla arm subassembly, I saw you guys use an extrusion bushing as a hub. Are extrusion bearings COTS or a custom made part?

Also in the gorilla arm, is the sprocket COTS or do you guys lighten it in-house?

With the pivot assembly, how do you keep the inside plate bushing in place?

The intake arm pivot versaplanetary gearboxes looks cantilevered and unsupported. Did it give you guys any trouble throughout the season?

How do you push the ball back into your intake? I noticed you had cylinders for it in your prototype but not in your final cad.

Can you please explain your bumper mounts to me? They all have a single clearance hole that I'm assuming allows you to bolt to the frame but I don't understand how they can stay fixed.

How do you mount your electronics? It looks like there's slots for you to ziptie your talons, VRM, and PCM, but I don't understand how you mount your PDP, roborio, solenoids, or kangaroo.

Your battery holder has 2 slots near the top. What do you use the slots for? Are they for securing the battery connection or for a strap around the battery?

How do you make the chassis skiis? Are they delrin or polycarb? Same with the big plastic belly.

Why do you power your drivetrain through a keyed shaft instead of hex? And how do you manufacture the drivetrain outputshaft with accurate key ways and tap holes?

At the top of your conveyer assembly, there's a part called "square disk". What's it for?

Your chain tensioners are really cool. I can see where the arm gearbox tensioners are sprung to, but where are the drivetrain tensioners sprung to?

Thanks a ton for posting your cad, it's an amazing resource for other teams!

[MalavyaS]

Originally Posted by YawnYao

You guys have an awesome robot this year. I have a few questions about the cad though.

Hi Yawn,

Thank you for the compliment, we worked incredibly hard this season!

Here are the answers to all your questions. I've categorized them in terms of the different systems, hopefully the answers explain everything you wanted to know.

Gorilla Arm (Intake Arm):
-Pivot Shaft inserts were made on the lathe using black ABS.

-For long standoffs/axles, we first end face the stock on both ends in order to have as close to a round number as possible (measured using tape measure). We then machine it to size accordingly using digital read out on our lathe, taking off necessary material after squaring up against a face.
-Extrusion Bushing was a custom made part in house. We first machined it on the lathe using black ABS, and then drilled the mounting holes using a vertical mill.
-Arm sprocket is a standard Vex Pro 54T 35 chain plate sprocket that we lighten in house using a CNC mill.

-The inside plate bushing is pressfit and secured using gorilla glue. During competitions as part of our pit checklist, we do push it back into place in case it is starting to pop out.

-Intake arm pivot veraplanetary gearboxes are cantilevered, but they held up throughout the whole season. The only issue we had was tightening the bolts too hard (Mounting the gearbox to the plastic extrusion). We fixed that by extending the aluminum gussets further upwards as you see in the cad, so that the aluminum supports the gearbox.

-We decided to omit the mechanism to push the ball back into intake. The idea was to push the ball out in case we wanted to score low goal, after it was in our popper. For weight reduction, and knowing that we can score in the high goal just as fast as low goal, we decided to remove this mechanism all together. That being said, if we did decide to score low, we simply closed our popper roll cage when intaking so that ball stays in conveyor area at all times instead of going into the roll cage area.

Electrical System:
-The camera mount was 3D printed in 2 pieces, and then assembled together using gorilla glue (hot glue during competition repairs). 2 Pieces are the ring, and the camera holder. We went through a few iterations in order to make it structurally sound, paying attention to the grain created when printing, the infill, and making sure it’s printed accurately. Ring was printed with the lip facing up, base was printed as if the camera is looking down. The camera mount dampener was also 3D printed using a soft polymer TPU Filament (Company: Ninja-Flex, Material Name: SemiFlex)

-The camera we used was a Microsoft webcam: https://www.microsoft.com/accessorie...nema/h5d-00018

-Router was mounted mostly with velcro and zipties, initially we did create a mounting plate for it, but we ended up mounting it directly to one of our gussets near the popper.

-The talons were mounted closer to PDP compared to CAD, allowing the wires to actually go through the slots. All electronic components were mounted onto the lexan using mushroom cap Velcro.

-The slots on the battery holder had the intention of securing the battery connector from the main breaker/PDP. We didn’t end up using that method but we do ziptie our battery power connectors securely every match.

Chassis:
-Bumper mounts included 1/4 -20 bolts (not in CAD) which acted as threaded standoffs or studs. Once the bumper was placed down onto the chassis, we fastened them down using wing nuts on the 8 exposed standoffs (4 per bumper piece).

-The chassis skiis were machined in house on CNC mill using Chlorinated PVC (CPVC). This material was donated to use from a sponsor, and we found it to be very versatile in terms of its use, bumper mounts were also made out of this material.

-Plastic Bellypan is made of 1/16” thick ABS, CNC’d on our router table, and flanges were folded in house on our breakpress.

-We had major problems with using hex bearings in 2014 on our drive train with them exploding. Thus, we chose to use 1/2" round bearings in our bearing blocks on drive. We had to choose between keyed sprockets, or keyed on the wheel end (we went with this option). For machining these axles accurately, we first use hex stock on the lathe and machine the features. We then secure it onto the vertical mill, and using an edge finder, and 1/16” endmill, we machine the keyway. The tapped hole is machined with a hole drilled using the mill, and then tapped by hand.

-The drive chain tensioners are sprung to different gussets which attach the shooter assembly to the drive chassis. All drive chain tensioners push down on the chain. We used surgical tubing with all our tensioners.

Conveyor:
-The square disk part on conveyor assembly is to prevent the belt from popping out when ball is being funneled on a more extreme angle.

Please let me know if you have any more questions!

[Sudesh Sahu]

Originally Posted by Jash_J

Day 2:
- Determined detail requirements for each sub assembly of the robot
- Broke off into groups and brainstormed various ideas for each sub assembly
- These ideas were presented and voted for. Ideas with the most votes are prototyped
- Parametric analysis is conducted

In Day 2 you say that parametric analysis was done. What exactly does that mean and what specifically did it include for you this year? Also, around how many hours does your team work per day during the first week?

[MalavyaS]

Originally Posted by Sudesh Sahu

In Day 2 you say that parametric analysis was done. What exactly does that mean and what specifically did it include for you this year? Also, around how many hours does your team work per day during the first week?

Hi Sudesh,

For us, parametric studies include 2 aspects:
-Standard Kinematic calculations using excel spreadsheets
-Simple 2D sketches showing geometry of systems that can be manipulated easily to show valuable information

The parametric studies essentially give us a starting point for the prototype CAD and things to look out for once built. It gives us approximate dimensions for key features, while also telling us which features we have to experiment with/optimize using our prototype.

We completed parametric studies for all of our subsystems this year.

Shooter:
-Projectile Motion spreadsheet to determine wheel rpm, launch angles, height of shooter from floor.
-2D sketches outlining ball path through the popper and shooter, showing us pinch values, and dimensions for flywheels/shooter arch etc.

Variables to be confirmed using Protoype: Shooter angles, number of wheels, RPM

Inake:
-Complete 2D sketches showing pivot point and overall geometry of the system, including roller locations, and bumper height approximations.This helped us determine the dimensions/geometry needed to defeat the cheval, portcullis, sally port, and drawbridge
-Torque calculations for determining gear ratios in order to allow the intake arm to lift our robot (mix of both 2D sketches and excel spreadsheet)

Variables to be confirmed using Prototype: Make sure geometry works + Hooks for drawbrige + durability tests in terms of strengths (we ran our intake prototype into the wall approximately 1000 times to inspect damage)

Drive:
-Kinematic spreadsheet outlining gear ratios for achieving our desired acceleration and top speed
-2D sketches showing initial drivetrain geometry going over all the defences to check for lengths, clearances, and wedge angle.

Variables to be confirmed using prototype: Center to center distance between wheels: 11" vs 10" (which we ended up choosing)

Hours of work during Prototype Week:
Kick off Saturday/Sunday: Approximately 11-12 hours per day
Monday - Tuesday (Cadding Prototype): Approximately 8 hours per day
Wednesday - Friday (Building Protoype): Approximately 5-6 hours per day
Week 1 Saturday/Sunday (Testing): Approximately 8 hours per day

Let me know if you have more questions!