Final Weight Estimation

With the CAD model completely finished, we were able to do a final estimated weigh in. All of the electronics have been wired and soldered, and could do with significant wire length shortening to cut even further weight. All weight is accounted for except for the spacers that will be used between each weapon tooth. Additionally, we counted out all of the hardware that will be needed to assemble the chassis and also added that to the weight. Currently, based on the current estimate the bot is 1.3 grams over weight, but we believe we can more than cut that with the re-wiring that will take place after fabrication. If absolutely needed we can go down to 4 weapon teeth instead of 5 which would cut 30 grams. Currently the weapon assembly makes up 20% of the weight, and will be able to spin up to ~8-10k rpm. We plan on probably not running weapon at full speed just because it's usually more effective to have a bigger bite.

This is the final bill of parts and their expected weights. Parts that do not have a volume and only a weight we weighed on a gram scale to get an accurate weight of the part with all of the wiring that is currently attached to them. We think we can significantly cut weight though as currently there is an excess of wires inside of the chassis.

Honeycomb 3.0

Rough Fitting, Weigh In, and Improvements to Make On Honeycomb 2.0

Rough Fitting

All of the main structural components finished printing on Thursday evening and were available for pickup on Friday morning. In the final design we plan on switching out the bottom, top, and side plates for 6061 aluminium and increasing the infill for the mid and back plate to 100%.

We did a rough fitting, not screwing in all screws, but just checking to see if parts and electronics are lining up the way that they should be and to check the clearance's of the holes.

The electronics look messy, but we plan on cutting down and re-soldering all the wires to appropriate lengths to cut weight and free up some of the clustered space in the internals.

Below is a list of components used in the build

Component	Name
Drive Motors	720 RPM Planetary Gear Motors
Weapon Motor	Turnigy 2836 Brushless 450-Size Heli Motor 3700kv
Drive ESC	Scorpion Mini ESC
Weapon ESC	Hobbywing X-Rotor ESC - 40amp
Battery	Turnigy Graphene 1000mAh 3S 75C Battery Pack

Weigh In

For the weigh in we went into Autodesk inventor and found the volume of all the custom parts (excluding the drum and side armor), then calculated the mass of the parts based on material density and the volume. We also had a scale to weight out all of the components IRL to account for their weight plus the weight of wires and connectors. In total the weight came out 1170 grams, which leaves about 200 grams for drum and side armor which isn't enough. This weight account for the bearings, shaft, gears, and shaft collars that will be used on the weapon assembly leaving the weight for only the drum.

Places to cut weight from:

1. Midplate, instead of a 8 way cross hatch, cut it down to 6 way (diagonals and vertical only). Cut down the material between the holes to mount the top and bottom plate.
2. Sideplate, instead of a 6 way cross hatch, cut it down to 4 way (diagonals only). Maybe, add some holes behind the bearing mount to cut more weight.
3. Backplate, instead of a 8 way cross hatch, cut it down to 6 ways (diagonals and vertical only). Cut down the material between the holes to mount the top and bottom plate.
4. Bottomplate, maybe double the honeycomb design to the bottom plate may present structural issues for mounting ESCs, battery, and radio receiver.
5. Electronics, clean up wire lengths to whats needed. Currently a lot of extra wires present in the build can probably cut 30+ grams.

Out of all the places to consider cutting weight my most hesitant place to cut weight from is the bottomplate and sideplate behind the bearing mounts as this might negatively effect structural integrity. We think the most drastic weight cut will be from the plating since those will be the largest amount of material removal.

We will also weight out all of the potential hardware that will be needed to hold the bot together (screws, nuts, washers, etc.) This weight will probably be even with any weight we cut with electronic's clean up

Improvements/Changes

1. Increase hole size for all 6-32 screws to a .144" clearance holes.
2. Move the centers for the top and bottom plate holes and mounts on the plate to be 5/32" instead of 1/8", idk why I didn't do this to start since a 6-32 nylock nut is 5/16" not 1/8" wide
3. Increase hole size for weapon motor mount to m3 clearance holes
4. Increase hole size for weapon motor shaft to clearance hole for a 3.17mm shaft
5. Increase hole size for drive motor shaft to clearance hole for a 4mm shaft
6. Taper the connection between the plates by 1-2 degrees to allow for easier slotting.
7. Change the tolerance on the shaft connection for the drum so that it is a close slide fit, not a interference fit.
8. Change the tolerance on the bearing mount to be a soft interference fit.
9. Add slot for weapon motor wires to clear to allow flush fit.

Fabrication of Honeycomb 2.0 Prototype

Once again to fabricate we used the IU 3D Print Lab. Currently we have the top, bottom, and side plates printed. The rest of the bot is currenlty on the printer and is set to finish up this Thursday around 8PM if I did my estimate correctly. This time we used the Ultimaker 3s instead of the makerbots, this allowed us to use dual extrusion to print some of the more intricate parts on the build.

This time true to form the top plate is now indeed Honeycomb.

The bottom plate finished up cleanly.

Don't know if you can see it here, but we had some issues with warping on the edges of the side plates. For prototyping this shouldn't really matter, but we wish it looked better :(

Redesign of Honeycomb 1.0

When approaching the redesign, there were a few things that we had to consider that we feel like we learned from our first design of this bot.

1. The clearance between my drive motors was just a little too close, so we wanted to widen the chassis by .25"
2. We originally had designed the weapon to be a dead shaft much like in the design of Radii V2 (http://hkim702.blogspot.com/2018/02/radii-v2.html). However, this presented a few issues especially when converting power from the weapon motor to the drum, so we decided to switch to a live shaft to allow the use of some VEX Pro motion items to more easily power the drum.
   
   Also, we have made the change to chain, such little is used we figured the reliability outweighs the added weight plus the team behind Radii made it clear that they had issues with belts and having consistent tensions fight to fight.
3. Due to the change in availability in Banebots t40 2-7/8" wheels (no longer in production) we had to make a change in the design to accommodate the 3" precision wheels from servocity which are about .2" wider than the banebot wheels. Additionally this also meant we had to make a change with the height of the skids that hold the weapon off the ground.
4. Added a new weapon motor mount to support the weapon motor more fully and still allow it to have proper clearance from the outer wall.
5. Increased the length of the chassis to accommodate all the electronics, after putting together the last version it quickly became apparent that there was not enough room in the design to accommodate the weapon motor and esc.

Prototype Fabrication of Honeycomb 1.0 and Review

For the first prototyping we used the IU Bloomington 3D print lab to fabricate my pieces. All the pieces for this round were fabricated on the MakerBot Replicator. Not pictured below are the top and bottom plates. The drum would be set on the 2 dead shafts on bearings and run via a belt through the notch in the mid plate support. This gave us the chance to put in all the electronics and see how it all fits together, and there definitely has to be some changes going into the next round of iteration being that everything was a little too cramped and could use a little more room within the chassis.

Honeycomb 1.0 Design

For the design of Honeycomb 1.0 a lot of inspiration was drawn from Radii V2 (http://hkim702.blogspot.com/2018/02/radii-v2.html). This was a tried and true drum spinner, and the authors of this blog made sure to highlight some of the issues that they had related to design and materials that they used in the fabrication of their robot.

Going into the design of Honeycomb 1.0 we're going to list the thoughts of some design aspects.

1. Interlocking outer chassis to improve strength and rigidity.
2. Outer wheel covers to protect from getting hit.
3. Invertible design.
4. Dead shaft to mount the weapon motor.
5. Easily replaceable outer layers that are designed to take a beating.
6. Have the side plates made from aluminum and the center plates 3d printed to cut weight while not sacrificing too much rigidity.