ME/EE 72: Airboat Proof of Concept

Purpose:

The goal with this build was to prototype a flat bottomed RC boat with as little investment of resources and engineering time as possible. To that end, this boat features a 3D printed hull (low time commitment to fabricate), with propulsion hardware scavenged from a team member’s quad-copter, and a controller borrowed from the shop. Although less polished than most of my projects, the payoff in terms of [lessons learned] / [time invested] was fantastic.

ME72: This is the first in a series of posts about ME72, a design capstone course in which 5 person teams compete to build 3 robots then can to fit that year’s competition. This year, the course is amphibious in nature, with a strong emphasis on ball manipulation.

Design:

I choose an air-boat for our first prototype, largely on the grounds that it is by far the simplest and cheapest motion system to build. The thrust-tower is designed to support at most an 8 in prop, with provisions made in the model for increasing the height as needed. This provided adequate power for hull-testing, and is most likely what I would use for future hull-tests as needed.

Using a half-height (4in) steering fin reduced print time, and made the model easier to assemble. However, it did result in a noticeable decrease in overall control authority relative to a full-height fin. This was most noticeable at high speeds, but was an issue throughout the power curve. In the future, this could be addressed with a taller fin, or by increasing the maximum turning angle of the fin beyond it’s current 10 degrees.

Although the hull doesn’t have any water-tight compartments, it does feature a sealed deck. This allows it to swamp, but not sink, when taking water over the sides. Although this proved unnecessary in normal operation (no water was taken over the stern), it did prove useful when a friend accidentally drove the vehicle through a fountain.

The control fin (see below) is actuated by a single servo, and has a 10 degree travel arc. This is sufficient for general locomotion, but would likely be insufficient for operation during the game. The fin pivots on two 1/4in steel dowel pins pressed into the motor mount and motion tower base. Both pins were heated and then inserted into nominal size holes. The fin’s pivot hole is 25 thou above nominal, and produced an adequate low friction fit after some working back and fourth.

The thrust and control tower without linkages. Overall it performed well, with the sacrificial motor mount working as expected.

The completed assembly in Solidworks.

3D printed hull:

In the interests of time, and as a bit of an experiment, I decided to 3D print the entire hull as a single piece. This was largely successful, with a few fairly major caveats. The print took about 100 hours on one of the library’s CR10s. The lower hull was printed 5 layers thick, the deck was printed 3 layers thing, and the internal ribs were printed 2 layers thick. The boat was printed with layers perpendicular to the spine, with 105% flow and a perimeter speed of 30mm/s.

The first major issue I ran into was under-extrusion. Even running at 30mm/s, this print really pushed the CR10’s limits. As a result, the hull came out a lot weaker than I would have liked. Slowing down the print mid-way through helped, but seemed to deteriorate even more late-print. I am not clear on why, but plan to do some exploratory disassembly to find out.

The bigger issue, is that as a result, the boat leaks leaks like a cive. This was most pronounced in the early and late print where the under-extrusion was worst. Rather than printing a second hull, I decided to seal this one with spray paint. That required 4 general cotes across the whole hull, and 3-6 more in the worst areas. This fixed the leaking, thought it did nothing for the structural integrity of the hull more generally.

The control fin, motor mount, and thrust tower were printed without issue on my own machine.

Lessons:

• 3D printed parts cannot be assumed to be water-proof unless the filament is significantly (and consistently) over-extruded.

• Spray paint makes a good sealant, but requires a large number of layers and has a poor $/in^2 ratio.

• Slant sided, flat bottomed, hulls are very vulnerable to weight imbalance.

Project materials:

• Solidworks: [CLICK HERE]

• STLS: [CLICK HERE]

Video:

ME14 Transmission - Fabrication

Overview:

Our transmission design calls for 36 machined parts, generally held to 2 thou tolerances, with the majority being either rotary table or lathe parts. We were generally able to machine exactly to spec. However, in a few cases we had to modify the design slightly to accommodate issues with tooling or available stock. 

Note: In the interests of completeness I have included a summary of how we fabricated each part in the transmission. However, I spent the vast majority of my time working on our rotary table parts and as a result those are described in much greater detail. 

General Reflections: 

• By far the biggest lesson I learned from this project is that there is a very large per-part learning curve. Even completing operations I had done the same day the time to re-cut a part was generally about 1/2 to 1/3 the time to cut it the first time around.

• reamers and boring bars should be checked for wear before use. One of the big issues we had throughout the project was discovering that many of the shop reamers cut substantially oversize. Testing beforehand would have caught this and eliminated some re-work.

The inner face of an outer alignment plate. Note the transfer shaft pocket and 6 tapped holes.

Alignment Plates: 

The alignment plates hold our gear shafts in alignment, and are our most complicated rotary table parts. All three plates are largely identical. However, there are some substantial differences in terms of mounting hardware and shaft fits (see below). 

Since this part is internal, we decided to go with a finishing wheel polish. We had originally used a sand blasted finish, but found it to delicate for internal parts.

Before starting machining of any kind we first set up the rotary table. The table itself, chuck plate, and chuck all had to be centered to +0.5 - 0.5 thou. Fortunatly, we were able to keep the fixture set up throughout the project.

For the most part the alignment plates were machined according to plan. However, we did open up the center plate's alignment holes to a clearance fit in order to ease assembly. 

Notable Features: 

• Groove for a -145 compression fit o-ring.

• Slip fit holes for the alignment shafts.

• Press fit holes for the IO shaft bearings.

• Press fit pockets for the transfer shaft bearings (ends).

• Clearance hole for small transfer shaft gear (center).

• 1/4 - 20 countersunk holes for tension screws (ends).

• 1/4 - 20 tapped holes for tension screws (center).

• 4-40 tapped holes for end plate screws (ends).

Machining Process: 

These parts were machined in two parts. First, the rough shape was marked, sawed, and ground out of sheet scrap. The rough center of each piece was then drilled and reamed to accept a 1/2" arbor. This allowed us to turn the parts to their final dimensions and add the o-ring groove. Once the part was at it's final dimensions, we moved it to the rotary table. We then machined all of the various holes, threads, and pockets on the mill. For the end plates one of the alignment holes was used as a reference to ensure consistent angular dimensioning between sides. 

We had a huge amount of trouble with the shop reamers for this project. In particular, we found that most of both the 5/8 and 1/4 shop reamers run several thou large. For the reamed 1/4" holes we used a 1/4" nominal reamer and sanded the holes to size. The damaged 5/8 reamer was only used for one hole, and in that case we press-fit a plug in place, and re-drilled/reamed the hole using sharper tooling. 

Stock

That time we needed a smaller hole so we pressed a plug in place and re-drilled it. (Worked fine, would do again). 

Outer Casing: 

The outer casing was machined from a piece of 3.5in aluminum tubing with 3/8in walls. The ID and OD were then turned to ensure they were concentric, and the ID was taken down to comply with the requirements for a -145 compression fit. Once the housing stock had been fabricated six 4-40 holes were trilled and tapped in each side of the part using the rotary table. To ensure good alignment the entire inner module was assembled along with both end plates, and the second set of holes were located using a center punch (with the rotary table to enforce circle diameter and angular spacing). 

End Caps: 

The endcaps serve two purposes, they protect the internals from contamination, and they prevent the inner transmission assembly from spinning relative to the casing. Fundamentally though they are mostly an aesthetic component. Each blank was first roughed to size on the bandsaw and then turned to size on the lathe. The socket head pockets and bearing relief were then cut and the parts were polished to a mirror polish. 

Alignment Rods:

The alignment rods stretch from one end-plate to the other suspending the central alignment plate between them. The rods are made of O1 tool steel, and were machined to length on a lathe and then sanded slightly to a firm slip fit. 

Spacers:

The spacers hold the axial spacing of the plates. They are composed of 5/8in aluminum and were cut on the lathe in two groups, both internally consistent to about 0.5thou. The ID was taken up to 9/64ths in-order to ease assembly. 

IO and Transfer Shafts: 

The IO and transfer shafts were cut out of 0-1 tool steel, and were designed to fit snugly between their constraining plates. The retention clip grooves were cut with an appropriate carbide groove cutter, and the overall length was turned on a lathe. Small flats for each set screw were cut using a collet block and machinists jack on a vertical mill. We found that the use of a sharp (new) endmil was non-optional for cuttiong O-1 with good tolerances. 

Base Plate: 

The base plate was fabricated out of the same 7/16in stock as the base plate clamps. It was squared and then the holes were drilled. The dimensions for this part were largely constrained by the size of our clamp stock, and the hole pattern specified by the test apparatus. Once fabricated, all of the base and clamp components were sand blasted. 

Base Plate Clamps:

The base plate clamps were one of the most fun parts to create. First the shape was sketched on scrap with a compass. Then, they were clamped to a rotary table and the curved sides (OD and ID) were cut. We had originally planned to use superglue for that process, but after speaking with the shop foreman decided to use two different clamping setups instead. 

Once the outer profile had been milled, we clamped the parts in one of our Bridgeport clones, and used the rotating head to cut the two angled pockets. After a bit of debate, we ended up using three setups per part with a work stop, rather than moving the head for each part. That worked well, and I would use that approach again. 

Clamp Riders. 

The clamp riders were cut with a pair of bolt cutters and then sanded/hammered to length. This worked well enough, but if I were to do the project again I would try to hold both the hole depths and the clamp rider lengths to tighter tolerances. 

ME14 Transmission - Design

What is this? 

The ME14 Transmission project is the first design and fabrication project in the caltech Mechanical Engineering curiculum. The idea is to work in teams of three to design and fabricate the best fixed ratio transmission possible.

Once built, the transmissions are tested using a known motor and load.  The test apparatus tracks a number of parameters, but the two critical values are "Seconds to reach 250RPM" and "Maximum speed reached in 250 seconds". The latter divided by the former provides a final score for the competition in the form: 

Score = [Max Speed] / [Time to 250]

Team Goals:

Before starting our design process, we got together to talk about our priorities as a team. Based on that conversation, we came up with three guiding attributes (below) for our transmission design. We also decided that although we're very willing to work outside the box we don't have any interest in creating something groundbreaking for it's own sake. Design innovations should decrease fabrication time, improve reliability, or increase professionalism/polish.

Projected score as a function of gear ratio

• Completely functional. 
• Highly Reliable.
• Built to a high standard of professionalism and polish. 
• *NOT* groundbreaking for groundbreaking's sake. 

Gear Ratio: 

Estimated time to 250 RPM as a function of gear ratio

One of my big projects this first week was drawing up a comprehensive model of the transmission's motion systems. I first defined moments of inertia for all of the rotating components of the system, and then used standard values for spurr gears and angular contact bearings along with the drag model we were given for the test apparatus to determine the parasitic torque as a function of speed. That, along with the stall torque, operating voltage, and max speed of the motor let me predict the gearbox's performance across a range of different gear ratios. 

Within our allowed ratio range (5-7) I found that performance improved slightly for smaller values. However, difference in scores was small enough to be dominated by secondary factors like shaft alignment and bearing efficiency. With that in mind, we went ahead and selected a pair of high precision stainless steel gears from SDP. Our large gear has 52 teeth, and the smaller gear has 20 teeth. That gives us a stage ratio of 2.6 and an overall ratio of 6.76.

We expect a score of 8.04

An early draft of the central module using placeholder gears. The model is fully parametric, and shifts to accommodate different gear ratios. 

General Structure: 

Traditionally ME14 transmissions are built as a series of vertical walls, screwed to a base-plate and connected with rods, or another plate, on top to provide rigidity. This structure has the benefit of being easy to CAD, and fairly straight forward to machine since all the components are rectangular. However, it also seems relatively weak, difficult to adequately align, and fairly inelegant in that it's really only applicable to this exact competition. 

The transmission casing and transmission stand. The number of screws was later reduced to 6 per circle in deference to our budget. 

I choose instead to design our transmission as a series of stacked circular plates, separated by spacers and aligned by 1/4" steel rod. The gear shafts are held between the rods, and the entire assembly is kept under tension by four 1/4-20 cap screws. This module then slots into a larger aluminum cylinder with end-caps to keep it isolated from dust and damage. Jack then designed stand to hold the cylindrical housing in place and interface with the test apparatus. 

If successful we will be the first team to substantially deviate from the standard design in the history of the course. My hope is that this structure will prove more rigid, more reliable, easier to assemble, and more compact than the traditional framework. It should be noted that this design will be substantially more difficult to machine. However, we decided it was better to spend time making things correctly once, rather than spending time aligning the components by hand. Since everyone involved has a fair amount of machining experience, we have the luxury of making that choice. 

Materials Selection: 

ME14 transmissions have historically been fabricated out of acrylic. Both because it is easy to use, and because it is provided by the shop. We decided to use aluminum. Working in metal means being able to hold much tighter tolerances, take heavier cuts (without worrying about chipping), and achieve a much higher level of overall polish. The one drawback to using aluminum for the main casing is that it means you cannot see into the transmission. Since our goal is polished, and strong, this is not an issue. 

For gears, we choose stainless steel. High carbon steel would have been preferred. However, there were none available from an allowed supplier in the size range we wanted. Using 316 stainless, we have a factor of safety of around 9.6, well more than sufficient. 

The drive shafts, alignment rods, and transfer shaft are all composed of O-1 tool steel. This was to accommodate our high-precision bearings, and because we wanted experience with the material. (4140 would have been a few cents cheaper and would likely have worked just as well). 

Shaft Retention and Damping: 

Our gear train and shaft retention system. Note that while all relevant components are included and accurately positioned the gear collar diameters are not true-size. 

One of our big focuses for this design is minimizing vibration. With that in mind, we have decided to use o-ring spacers and retention clips to constrain each of the shafts axially. This lets us dampen any axial vibration we might get from shafts. It also allows us to easily and repeatably pre-load our bearings. This is important for ensuring the bearings wear in reliably, and is very important for the kind of high-precision bearings we have chosen. 

To provide additional vibration isolation, the alignment plates will be connected to the outer housing with press fit o-rings. The housing structure, with it's nylon riders should also help isolate the entire structure from the base of the test fixture (which tends to vibrate when the wheel runs). 

Oil Proofing: 

Early in our discussions, we debated making the transmission fully water-tight. That only requires slight modifications to the IO bearings, and the addition of some shaft seals. However, we decided it was inadvisable to pursue that kind of feature without more time for testing. Despite that, we have taken care to keep the design as close to water-tight as possible. 

Depending on the final transmission performance, we may take advantage of this to fill the inner housing unit entirely with oil. This would be a performance hit, but could also prove invaluable if we end up running in the transmission. If the transmission were ever to be used for serious torque transfer, oil filling would be required to protect the gears and wick away heat. It should be noted, that since we are using shielded rather than sealed bearings, we expect the unit to leak slowly. Fortunately, the rate of loss should be low enough to be inconsequential for out purposes. 

Belt Grinder: Project Goals

What is this?: 

When I start a new design project I always record my general design goals for the project before starting out. I find this helps keep me on track and cuts down on unnecessary feature creep. This is mostly recorded here for my own benefit during future design revisions, but may 

Overview: 

This is a medium length (40 hour) project intended to expand my repretwar of knife making tools and give me a bit of machinery fabrication experience before tackling something CNC.  A belt grinder is a device used to remove metal, or other materials, from a part through the use of an abrasive belt. This particular grinder is being designed with knife making in mind, and as such will use the 2" by 72" belts standard to that pursuit. 

This unit will be designed to live in the Caltech Student Shop during the remainder of my time here, though I will likely take it with me when I leave. Since my future housing is not known, power and space requirements will be dictated by what is available in the Student Shop.

Learning Objectives: 

• Become comfortable using the Water Jet.

• Become comfortable using the Haas TM1.

• Get experience designing belt tracking systems.

• Get experience using solid works modal analysis.

• Get experience using GD&T.

Product Objectives: 

My product objectives are broken down into three categories as follows. Items in category "need" are required for a design to be worth considering. Failing to fully realize this category is a no-go check for the project. Items in the "want" category are things I feel dramatically improve the base functionality of the grinder. The goal is to incorporate all of these features, though some may be ignored if need be. Items in the "dream" category are things I feel would expand the functionality of the grinder. The goal is to incorporate a few of these, though likely not the majority.

Need:

·         1.0hp motor.

·         Interchangeable attachments.

·         Square workpiece supports.

·         Adjustable tracking.

·         2x72

·         Platen, slack, and small wheel grinding.

·         120v

Want: 

·         1.5hp motor.

·         Adjustable speed motor.

·         Self-contained unit.

·         Interchangeable workpiece plates. 

·         Identical platen edges.

·         Direct drive. 

Dream:

·         Tilting grinder.

·         Adjustable workpiece plates.

·         Portable.

·         Speed readout.

·         One handed belt change.

·         Mist coolant.

Project Completed When: 

• The grinder unit is fabricated, calibrated, and tested.

• Either a platen or large wheel attachment has been installed.

• Fabrication and assembly plans have been compiled into a cohesive document.

[Knife Making] BUSH-CRAFT Prototype

My third knife! 

This is my take on a British woodcraft knife. It's made from 1095 high-carbon steel, with brass pins and a cocobolo handle. The blade is 3.8" with a 4.2" handle, and a 0.3" scandinavian grind for the bevel. 

The profile, bevel, and handle scales were ground to shape on a 2x42 belt grinder, and then hand finished up to 2400 grit by hand. The wood, brass, and spine were then sanded to an additional 12,000 grit. This knife was quenched in salt water, tempered twice for 2 hours at 325 degrees F. 

Build: 

Note: You'll have to forgive me for the lack of pictures. I was running a small knife making workshop concurrently with this build, and ended up not taking as many pictures as I might have liked. Well worth it though, I'm hoping to do another session again next term. 

Learning Goals: 

This knife is the first in - hopefully - a series of very similar knives based on a traditional British woodcraft design. The idea is to winnow down the number of design variables in play, so I can work on tweaking my build process and on getting a sense for what goes into good ergonomics. The learning objectives for this knife can be found below: 

• Practice sanding up to the reasonable limits of conventional sandpaper without leaving scratches.

• Experiment with 3d profiling of the knife handle.

• Experiment with handed finger grooves.

[Hell Lighting] Control Board V1

Overview:

Hell Lighting is controlled by a MEGA ADK mounted at one end of the hallway, adjacent to purgatory, where the power supply is stored. This is a custom "shield" to sit on top of the mega and provide IO terminals as well as basic control elements for the system. This pcb replaces the prototype unit used during Hell Lighting's trial period and, with the new pattern system now online, represents the last component required for us to declare the system fully operational. 

Although this shield is primarily intended as a control board for Hell Lighting provisions were made for it to act as a generic pattern controller. With that in mind, the board can run up to 670 LEDs, split between the four outputs, directly off of the power input terminals. For more information about independent operation and system current limits see the testing section below. 

Note: Although this board is installed and working there are two required reworks in order to use the board with the interrupt based version of our firmware. In particular it is necessary to connect Pin 15 to Pin 19 and Pin 16 to Pin 18 all effected pins should be set to inputs. 

Features: 

• Pattern Switching: One encoder to switch between patterns, with a built in button for resetting the current pattern. 
• Pattern Control: One potentiometer connected to an ADC input, and a button connected to an interrupt pin. 
• Screw Terminals: Four terminals for connecting patterns (GND, DATA, 5V), and one power input terminal (GND, 5V). 
• Display: One monochrome 8 bit bar graph for displaying the current pattern or debug info, and a power indicator LED. 
• Sensors: I2C temperature sensor with 1 degree accuracy and 12 bits of precision, front mounted. 
• System Control: Reset button, programing jumpers to issolate the arduino from power and ground. 

New board right before installation/cleaning. 

The old board... We don't talk about the old board. 

Firmware: 

Although this board is mostly just a cleaner version of the V0.1 board we were already using. There were a few features which needed to be enabled in firmware. A brief description of how each of these was handled can be found below. If you want additional details, please don't hesitate to reach out. 

All the best things come in parts bags.

Encoder: 

The encoder is responsible for controlling pattern changes, and is handled by an interrupt triggered on it's "B" pin. Each interrupt determines the direction the encoder is moving by comparing the values on A and B, then records a CW move if they are the same and a CCW move if they are different.

Even with hardware de-bouncing it is worth implementing some kind of bounce management in software. I found it sufficient to wait 80ms before allowing another tick to be recorded. 80ms is fairly responsive, but tends to give false direction reversals. To combat that, I set the wait time before registering a change in direction to 100ms which seems to have pretty much eliminated the issue. 

Interrupt time on a 2560 running Hell Lighting is at something of a premium since interrupts must be disabled when writing to LED strips with a 3 wire bus. With that in mind, I found that using the interrupt to record, but not act on, pattern change requests and then updating the pattern at the end of each frame worked far better than directly updating the pattern in the ISR the way we did when pattern change was handled by button. 

Pattern Output:

One of the new features this board incorporates is an LED bar graph to show the current pattern number. Since there were no conveniently located digital IO pins I connected it to port K on the atmega2560. This port can be set to output using the DDRK register. The correct values can then be written to those pins using the PORTK register.

Note that the design decision was made only to connect the graph only to the K register. This means that although it is a 10 piece bar graph we are only able to support 256 distinct patterns. At time of writing, we have roughly 16, so I do not anticipate this being an issue in the near term. Never the less it will likely be modified in the next rev. 

Temperature Sensor: 

The temperature sensor for V0.1 is the backed by two classes. One is a generic Temperature Sensor class, and the other is specific to the TMP175. These will form the first two classes in the new HAL for hell lighting. The TMP175 is an I2C device, but none of our end users will ever need to know that. A (very) abbreviated breakdown of the two classes can be found below:

SensorTemp - The high level temperature sensor class is responsible for keeping track of the last read temperature as well as the minimum and maximum possible temperatures for that sensor. It also exposes a set of functions to return the current (read new) and previous (return last) temperature in a variety of common formats. 

TMP175 - The TMP175 class fully implements the chip's features, including: variable read precision, low power mode, and extreme temperature interrupts. It also overwrites a function from the SensorTemp class to actually get data from the device and invisibly handle setting OS when the device is in low power mode. 

Verification: 

For the most part when it comes to PCB specs I am pretty happy to take board houses at face value (plus or minus a generous safety margin of course). That said, when it comes to questions like "Will this catch fire" I really prefer to do actual testing whenever possible. With that in mind, I decided to destructively test main power traces on the PCB by connecting the control board to a variable powers supply and slowly increasing the current until a failure point was reached. Temperature data was gathered with an IR thermometer (calibrated at 24c). 

Conclusion: Ultimately, the board "failed' at 21A when the board reached 165C and the solder melted. In order to keep temperature rise to a more reasonable 80 degree increase I would suggest limiting current through the on board power distribution buss to 17A (this limit has no bearing on systems like Hell Lighting that have external LED power). 

RESOURCES:

• Gerber Files
• Arduino Pinouts

Battering Ram

What: 

Sometimes you really just need to make a door go away... 

Grond and Aeglos are a 35lb battering ram and an 18" steel spike respectively. Both were built with Jack Caldwell and Max Debbas as part of Blacker's annual Hackathon.  The Battering Ram (Grond) is based on modern police rams, and is intended to be used by a single person. It's made out of an old drive shaft we found while dumpster diving. The spike is likewise made out of an old drive shaft, albeit a much smaller one.

Why: 

The house has long had a battering ram (affectionately nicknamed "Basher"). Unfortunately, it's made of wood with a concrete head, and even with 6 people Basher is almost impossible to use. We wanted to create something smaller, and more practical to replace Basher. After a bit of research we settled on a 35lb dead-blow ram with an interchangeable head. Grond is designed to work with sand, water, and Lead as the dead-blow shot. 

In practice, we don't really have all that many doors we need to bash in, so Grond and Aeglos are most likely to see use during either deconstruction or hell-ride. With that in mind, the idea is to use Grond for breaking metal parts, and Aeglos for punching through plywood waterproofing. 

Grond - Destroyer of Doors.

Aeglos - Poker of Holes

Our drive shaft turned out to be hardened steel, so we used the smelter to soften the steel before drilling/tapping.

Drilling the handle hole. This was a lot easier the second time around... (After removing the heat treat)

The buisness end of the handle. The pipe plug and elbow are welded in place, but the handle itself is not.

[Interhouse] Stairs - 2017

Story:

I have always wanted to work on the interhouse stairs, and when stairs team ran into personnel issues (through no fault of their own) I got a wonderful chance to put together our front staircase on the night of the final safety inspection. The experience itself was rather surreal -  the only other person avaliable to help had never worked on stairs either, but ultimatly succesful.  

Documentation:

To hopefully make he build process a bit faster next year, included below, is my solidworks model of the staircase we actually ended up building. As of now, the only significant design change I would make, would be to use three stringers in place of the two stringers and the 4x4 supports. Although the latter option is stronger, and marginally cheaper using pre-made stringers, it is also much slower to build and significantly less elegant than the three-stringer build.  

Model Files

Purchasing Note: 

The home depot in Pasadena has expressed a willingness to loan us stringers for tracing as long as we also purchase the wood we use in the final project from them. Since we buy all of our wood from them regardless, that seems worth pursuing. 

3d printed model: 

One of the great things about having a CAD of interhouse is that it becomes easy to print 3D models of parts of the build. This is especially useful for projects like stairs that are a bit harder for new folks to visualize. With that in mind, I decided to print out the individual parts and glue them together to make a 1/20th scale model of last years staircase. 

Build photos can be found below. Each stage was glued using CA glue with no kicker (to keep it clear), and then allowed to dry for 12 - 18 hours before the next glue stage. All parts are 1/20th scale. 

[Hell Lighting] Wiring

It lives! The past few days have been a tiny bit hectic, but the main power and signal wiring for the system is now fully installed and operational. We still have a lot to do on the system control and safety certification elements, but for now the lights are up and running with a temporary controller (linked in the project page) and the final power supply. 

Layout:

Hell lighting V2 is composed of four sections, each containing approximately 300 LEDs. Each section is powered by a single 5V 26A rail of the main Cosel ACE650F modular power supply.  The control unit runs off the final 5v rail of the power supply, though it can be moved to one of the main lighting rails if we make the decision to add a 5th lighting section in purgatory. Power for the four LED sections runs through 14 gauge UL 1316/1452 THHN black copper wire in twisted pairs. While the control unit is powered off of similarly rated 18 gauge black wire wire. Power for each section is provided at a single point in the center of that section. We have found this to be sufficient, in practice, to prevent visible color aberration under normal use. Additionally, each power supply rail has been seperately adjusted to ensure a steady 5v at the point of use. 

Signal for each section is provided to the start of that section through an 18 guage ground-data twisted pair. This means that all rails share a common ground, and that arduino ground is the nearest thing to a system wide reference voltage as can be found. Note, that like the power wiring, all data wires are black. My suggestion is to use a 1.5v battery and multi-meter to identify which wire is which at both ends should it ever become necessary to make adjustments. For additional calrification, please refere to the diagram provided or feel free to get in touch. 

Mounting:

Power/Signal bundle mid-hell. Note the spacing to ensure LEDs are vissable

After our disastrous attempt to use nails frosh year, we decided to zip tie mounts and zip ties to hold the wires up this time around*.  For aesthetic reasons, we decided to keep the wires, zip ties, mounts, and heat shrink black to match the LED strips.  One thing to note is that most of the black zip tie mounts sold on amazon are of very poor quality. We had much better luck spray painting good quality white mounts black. 

Above the purgatory couch, Internal corners like that should be put up carefully

To keep the process simple, we routed each twisted pair one at a time. Doing it this way involved a lot of wasted zip ties (even being careful to re-use them when possible), but meant that only one person was needed to make progress on the system. Unless you are heavily restricted in terms of your zip-tie use I would strongly suggest a similar approach. 

We spaced out zip tie mounts about one every 2.5ft, with double mounts at every corner. That spacing was hugely overkill in terms of weight, but just about right in terms of preventing the mounts from getting pulled off over time.  We also cleaned the wall with a dilute acetone solution where possible, although I have no data to support this as an effective practice. 

Entrance to purgatory, the E-Stop line has not yet been connected. 

It probably goes without saying, but it is very important that signal/ground pairs be twisted tightly to minimize interference from the signal lines (which will generate some noise whenever the LED colors, and thus power use, change). This can be done by hand, but is much easier with the aid of a hand drill. Cut lengths to 120% of final to deal with shrinkage. 

* Safety has suggested that they may want us to encase our wiring in conduit (which would be fantastic, that would make the system much more permanent), so this may end up being a temporary setup. 

Tips: Although the adhesive strips that hold up the zip tie anchor perform very well in tension they tend to peel and fail in shear. We found that as a result it really helps to put 2 or more anchors on every corner to help take the stress.

Zip Tie cutter

Summary:

This is my take on a dedicated zip-tie cutter. The idea was to make a blade that was strong, and extremely sharp, but also really short so that the user has as much leverage as possible. The design I settled on is intended to be used for slicing work, the sharp angle of the blade helps keep the user's hand moving perpendicular to there body when cutting, and the curve is sized to fit my thumb for more control when pulling the blade. 

I used 1/8" 1095 steel, ground down to 3/32" and peanut oil quenched. It was then tempered for 1:20 at 500 degrees. The patina is the result of that process, and the blade was then re-ground to give it a bit of definition. The spine of the knife is 4-3/4" long with the 7/8" blade set at a roughly 30 degree angle. 

Reflections:

For a second knife I'm quite pleased. I had never really used a belt grinder before and found that to be something of an education. It sharpen's easily, and cuts well.  I also think that for cutting zip ties 1/8th was the correct choice. It mean's the blade is essentially indestructible. That said, I would increase the angle of the blade to make prying a bit easier. 

Inspiration: https://www.youtube.com/watch?v=mFDIV4bynDE

---

My First Knife

Summary:

This is a knife that I made, hopefully the first of many, as a collaboration between myself and my father.  I made the blade, and he made the handle. Both the blade and handle were completed almost entirely using metal files and a hacksaw. The one exception being an unsuccessful attempt to put the final polish on the blade with a handheld belt sander. 

This knife is based on a very excellent video (below) by Walter Sorrels and is composed of 1/8" 1095 steel. Which I quenched in peanut oil and then subjected to two, one hour, 350 degree (f) tempers in the oven. It remains to be seen how well the knife holds an edge in practice, but it is extremely sharp, which I find to be encouraging. 

Build Pictures:

Cutting the steel to size. The hacksaw made supprisingly quick work of it. 

Failed attempt to do the final polish on a handheld belt sander. 

It's all about that edge...

Peanut oil quench. 

Magnet glued to a steel rod to test for temp.

It's a barbecue... A very hot barbicue...

Knife post-hardening. I almost wish I could keep the black. It's not a bad look.

Note: Drilling hardened 1095 is a no go.

Sanding to 400grit for a satin finish.

Time to put on the scales, olive wood is very oily, so it's important to clean both the knife and the wood with acetone.

Clamped, Epoxied, and ready for handle shaping. 

In addition to my own reflections above, my father also had some reflections which I have included below: 

1.      We drill the holes for the brass pins before we harden steel.  That is an obvious from our last experience.

2.      When selecting precut scales, we inspect both sides of the scales and pick the most aesthetic pieces of wood for the external side of the scales.  I do not know whether you did this or not, but it is an aesthetic that we want to incorporate.

3.      If we are cutting scales from a block, we use the sides of the cut pieces which should be similar or even mirror images unless we make a conscious decision that for aesthetic reasons we want to use a non-matching piece.  In addition, I think we should sand and pre-finish the two exterior sides of the pieces preliminary to see that we like the look before committing these pieces to the exterior and discovering after they are pinned include that we do not like the look.  This will make for a little more work, but the actual finishing of the sides is the least time-consuming part of making the handle. 

4.      We precut the scales closer to the actual dimensions of the knife handle.  The advantage of this is that we can do more hand sanding which is finer work and be more precise than having to grind it down with either the power sander or a file.  I think this will give us a better more precise handle fit and less likelihood of a "mistake" that requires a redo.

5.       By using the stir stick and a light amount of epoxy I think we can avoid the situation we just experienced where the epoxy expanded out of the glue area.

6.      I am still undecided as to the best way to finish the knife handle.  I am going to research this further but I have reservations about only a 220 finish sanding.  The question is whether (1) we stop at 220 and apply the oil (2) sand to the 220, apply oil, and then proceed to finish to a 400 grit or (3) finish to 400, apply the oil and then re-sand and buff accordingly.  Each of these has a theoretical advantage with the first choice perhaps getting a better oil absorption and the risk that the finer sanding will result in wood that is harder for the oil to penetrate, but I also think that the 220 finish may not be as durable or hard as the 400 grit finish.  I am going to do some further research and we can discuss this later.

[Metal Working] Deconstruction Hammer

Story: 

Every year for pre-frosh weekend* my house, Blacker, holds an event called "deconstruction" during which we destructively disassemble a pair of unusable bad pianos.  The pre-frosh are given a selection of sledge hammers and crowbars, while the current students are restricted to whatever we can find lying around the courtyard and on our persons (this is less of a handicap than it would seem, "pulies and a tree" both fall into that category). I was originally planning to use my machinist's hammer, since I have been carrying it around campus as part of that project. However, I was worried that it might not hold up all that well to prolonged use against cast iron. This then is a slight iteration on that design explicitly intended for use smashing pianos. 

Hammer:

The head is composed of a single piece of 304 stainless steel (the hardest, toughest material readily available on campus) while the hammer handle I turned from the same piece of 2025 aluminum that I used for my first machinist's hammer. One of the big lessons from that project was that a screw-on head is not the way to go. People like to see if they can unscrew the two pieces, and I have a feeling that the threads are getting very slightly beat up from the pounding. Given the amount of use that hammer has been getting, that's fine for a prototype machinist's hammer, but less fine for something intended for rougher use. I had originally planned to press-fit the handle to the head using LN2, but after a bit of experimenting it seems like an aluminum-steel press fit isn't likely to hold up (at least given my current skill set), so I ended up using a brass pin to hold the head to the handle, and then peaning it into place. 

Although I like the way the knurled handle performed on my last hammer, I decided to go with something a bit different for this one just to play around. The three larger gaps are positioned to fall under my thumb, middle, and ring fingers as they rest on the hammer. I am not yet sure how much I like this setup from an ergonomic standpoint, it may be that ridges hurt the hand under prolonged use, and I will update this document as I get a feel for that. 

Update: The handle design does not seem to be an issue with light use. I am pretty sure it would be if I spent the day driving nails, but the soft (relatively) stainless steel head means I'm not planning to use it that way in any case. . A bit more research (and some help from the wonderful people on the hobby-machinist forums) suggests that wood might be a better choice for that kind of pounding in any case. 

Build Pictures:

[Smelting] Propane Torch

More Fire...

I have been smelting using charcoal and forced air for a little while now. Charcoal is great, because it's cheap and very easy to set up (All you need is charcoal and a hair drier). That said, it can be difficult to get coal fired furnaces up above 700c. Now that I have a bit of time (it's summer, yay!) I have converted my smelter to run on a propane torch, the construction of which is detailed below. 

The design I settled on is a stripped down version of a build by "Turner Forge" on youtube (resources). This is definitely not the highest efficiency build, for starters the air intakes are not in line with the flow, and the 1/16th drill bit I used was about 3 times larger than ideal. The way I built this was also epoxy heavy which will make modification a bit hard. That said, if you are looking for a simple, very low cost, build then this is for you. 

Results: After playing with the torch for a bit there's no question propane is the way to go. A crucible of aluminum melts in about 7 minutes. Copper takes a lot longer, with a crucible taking a bit over an hour, but on the other hand it's possible and the process takes less than a quarter of a 5 gallon propane tank. I did find that for longer burns it helps to place the tank in a bucket of water, to keep it from frosting over. 

Build: 

All told, this build takes about 30 minutes plus however long it takes your epoxy to dry. Note that in addition to the parts listed here I also added a ball valve to shut off the torch, and an upstream T section which I may in the future use for pilot light or the like. I already had those parts, but if you included those as well it would add about 5 or so dollars to the build cost. If you do not already have them, you will also need a high pressure (30 PSI) propane regulator, which can be gotten on amazon, and a 5 gallon propane tank. 

The nail, copper sheet, washer, and 1/8" drill bit were for use making an inlet cover. WIth a 1/16th drill bit that ended up not being necessary since the torch functions best with the hole almost fully open. 

Materials: 

• Brass Fittings: 1/2" by 3" extension, 1/2" endcap, 
• Steel Fittings*: 
• Adhesives: Epoxy, Plumbers tape

Tools: 

*What size/type you use isn't important, but it's best to avoid galvanized. 

• 1/16th (or smaller) drill bit. 
• 1/2 inch drill bit (and smaller to step drill)
• Power Drill (or mill). 
• grit (or similar) sand paper. 
• Metal File. 

Resources: 

• Turner Forge
• Home Depot

Use the 1/2 inch drill bit to create a hole in the steel end cap. Use smaller drills to step up the size of the hole as appropriate (1/4" and 3/8" would work well). 

File hole and sand the extension until the two fit. Then wrap one side of the exntesion in plumbers tape and attatch the step-up fitting. 

Insert the extension into the steel end-cap such that 7/8" is exposed on the other side of the cap. Use epoxy to seal any gaps between the extension and endcap (this is optional). 

While the epoxy sets, use the 1/16th drill bit to make a hole in the center of the brass end-cap. de-burr the hole if practical. This will be the propane nozzle. 

Wrap the threads on extension and screw on the nozzle. Then, connect the three pieces of steel pipe. Those connections do not need plumbers tape. 

Finally, screw the steel end-cap into one side of the T-Section and the steel pipe into the other side. The torch is now ready to be connected to propane for testing. 

Before using the torch for the first time, make sure to check for leaks. There are a number of ways to do this, but the one I have found easiest is to take some household cleaner product (Windex works well) and spray it over the torch. Then turn the torch on and watch for bubbles. If there are any forming, that tells you that you've got a leak. Patch with plumbers tape or epoxy as appropriate. 

Airflow to the torch can be controlled by partially blocking the air intake with a piece of tinfoil or other metal (It will get too hot for tape, but not too hot to use paper or wood). The goal is a nice blue flame. 

Water Feature Auto-Fill

The lazy option...

Front View

This post details my process for creating a level-triggered filling line for the water feature by my parent's front door. In the grand scheme of things filling the water feature is a process which takes maybe 5 minutes every few days, but if you have every found yourself standing in front of a fountain holding a garden hose and wondering if there is a better way, this post is for you. 

Note: In large parts of the US tap water additives (notably chlorine and chloridimine) will kill goldfish and other complex organisms. Not relevent in this case, but something to keep in mind. 

Design: 

There's a full parts list below, but really this project is about connecting three things: A water level sensor (relay), a sprinkler solenoid, and a 24v AC power supply (transformer). The rest of the parts are there to either neck down the valve to fit hose/tubing, or to dress up the outside a bit. I also used some wire sheath to hide signal wiring and fill tubing. That's definitely window dressing, but I'd strongly recommend looking into it, you can get the stuff at home depot and it really takes the apparent professionalism to the next level. 

Diagram 1

The actual wiring and plumbing setup is really simple (See Diagram 1). The solenoid valve sits between a pressurized water source (hose) and your desired output. While the fill sensor completes a circuit between the transformer and solenoid. Note that this only works if the sensor also functions as a relay. If it provides a voltage output, or variable resistance an arduino would be needed to activate the relay. 

Materials:

Water level Sensor

Solenoid Valve

24v AC power supply

Wire (18+ gauge)

Fittings and tubing as appropriate. 

Plumbers Tape

Zip Ties

Build: 

Connect the fittings to valve - making sure to use Teflon tape where appropriate. This is easier before the wiring has been attached. 

Then measure the distance between power and the solenoid as well as the distance between the solenoid and the water output/sensor locations. 

Connect (solder) one lead of power supply to one sensor lead. Then connect the other sensor lead to one lead of the solenoid. Finally connect the remaining solenoid and power transformer leads. I found it cleanest to make all connections at the solenoid and hold them in place with zip ties and electrical tape. 

Note: Depending on your measurements from the previous step it may be necessary to splice or shorten some of the leads. 

Using your measurments from step 1, cut your plastic tubing to length (If appropriate). Then, cover both the tubing and sene wires with plastic sheaths. Zip tie the sheaths to the solenoid acording to your own sense of asthetics, and use the electrical tape to make a uniform shell (note: The electrical tape is a poor choice if water is inolved, if you expect the solenoid to get wet cosnider gurilla tape). 

At this point, the system should be fully set up and ready for testing. After doing a few worktop tests, set up the system in it's final spot and let it sit for long enough to get a sense for if things are working as you expect. (This is optional if you are confident that everything will work)

If the aesthetics work the install is complete. Otherwise, move on to fashioning a more permanent fixture. 

[Hell Lighting] Bugs

For the most part Hell Lighting has a small enough team to make bug reports easy to manage through messenger and github. That said, I have included a few of our more notable issues below. My hope is that they will prove useful in helping others avoid our mistakes, or at the very least amusing. 

Red 255 (Resolved)

Description: If Red was set to more than 80% brightness all LEDs switched to randomized changing colors.

Cause: All system elements were grounded at the power supply. Signal wires run as part of the power bundle were picking up interference from the power lines and each other and transmitting it to the lines where signal shaping circuitry served to turn the noise into random colors. 

Resolution: Re-ran signal wires as twisted pairs with ground lines. Isolated power supply grounds, and used control board as common reference (so the only common ground point between the rails was at the control board). 

Reset on Bright (Resolved)

Description: Patterns with sudden changes of brightness cause system resets on the low to high transitions. 

Cause: Sudden changes in current draw from the supply caused momentary drops in voltage below the reset value for the arduino. 

Resolution: Switched controller power from strip 4 to the reserve power supply rail. 

Gesture Control (Open)

Description: If someone rubs there hands on the carpet and then waves them in front of the control box, it will reset. This occurs about about 2% of the time, but has been repeated a few dozen times successfully. 

Cause: ?????? Best current guess is that highly charged hands have an effect on one of the reset lines on the board and trips it. No idea how that would work though. 

Resolution: ??????? Don't charge your hands right before using the system? 

Shock on pattern change

Description: One user reports a consistent, light, shock when pressing the pattern change button. 

Cause: Have not been able to re-produce. Low priority unless it persists past the 1.0 control board.

Resolution: See above.

[Interhouse] River - 2017

My guess is that if you are reading this then Blacker has decided to do a river for interhouse and you were foolish enough to volunteer (It's actually an easy project aside from the paperwork). This page outlines how we did the river for Blacker's 2017 "Japan Through Time" interhouse, but the design is modular, so you should be able to use it for whatever setup you want.  For the pump system and waterfall I have included notes from our postmortom design review with things to watch out for or possible improvments that could be made to the system. 

River Sections:

The river itself is composed out of 8ft sections (see right). Which can be built before hand and then raised to height and connected when needed. These units are intended to be single-interhouse and so emphasize cost over durability. That said, they should be good for a few short uses. 

The assembly procedure we used for each 8ft section runs as follows:

• Cut the two 6" lengths, two 4' lengths, two 22.5" lengths and the 18" by 8' plywood section.

• Lay out two 2.x3s 18" apart (from outer edge to outer edge) and check that they are parallel (if bowed, place so the center bulges).

• Put a continuous line of glue down each board (this acts as a last ditch sealant).

• Place the plywood on the two boards and fix it in place with a screw at each corner. As far as we can tell it is safe not to drill pilot holes if the house is out of bits.

• Add a screw and washer every 6-10 inches down both of the two 2x3s.

• Measure 33 inches from opposite corners of the structure and secure the two 6" sections with two screws. It is important to drill pilot holes.

• Connect one 4' sections to the main structure 36" inches in from the ends using a single screw. It is important to drill pilot holes.

At this point the structures can be moved into place, lifted, and then the legs can be fixed in place using an additional screw at their pivote points and two screws where they cross eachother. I find it also helps to add two braces connecting the sides. Once the structures are in place, make sure to use hot glue (or simiilar) to seal any remaining cracks. This is best done last since moving them will open up new leaks.

Note: During our post-party design review we determined that the seal between plywood and the 2x3s would be improved by the presence of a 1x3 underneath providing additional support. This board should be pre-bent so that it can be used to compress the plywood against the 2x3s. This should help prevent the small leaks that sprung up on 3 of the 4 sections we deployed. This design can be found in the V2 version of the uploaded documentation. 

Unit Cost: 15$

Unit Time: 30 min

Materials: 

• [4.5] 2x3 soft wood.

• [40] 1.5" Deck-Mate screws (go torques).

• [5] 1cm diameter sticks of hot glue

• [1/12] of a medium sized bottle of Elmers wood glue.

• [1] 18in by 8ft section of thin plywood or press-board.

Documentation: 

• PDF V1

• PDF V2

• CAD ZIP

Water Reciculation

Water for the river is pulled from the catch basin, down a length of 3" pipe, and into the pump. It is then pushed up to the waterfall, where it runs out a series of holes drilled in the bottom of the pipe. It then falls down the waterfall, entering the river. The remaining water is then piped back to the collection basin to be re-circulated. Of particular note, the pump sits at the bottom of the waterfall structure and below the level of the water in/out takes. This allows the pump to be primed by poring water down the intake until it begins to overflow back into the basin. 

By far the hardest part of this project was getting the pump system to play nice without giving party-goers an impromptu shower. The pump is significantly more powerful than we had anticipated, and left to it's own devices, was more than happy to project the waterfall a good 3-4ft beyond the catch basin that feeds the river. To lower the pressure, we ended up having to add another stretch of pipe returning unused water to the collection basin. This is clearly not the ideal solution, it would have been nice to pump that water into the river itself instead, but it did work and kept safety happy. 

One thing to keep in mind is that the pressure on fittings after the pump seems to be much greater than on fittings before it. It is well worth clamping or gluing any right-angle fittings or the like on the water return run. On a similar note, it is worth watching the system for a bit after starting it up, because temperature effects from the cold water will change the fit of any press-fit fittings during the first 5 or so minutes of operation. 

If you end up using one of the houses's large sump pumps it is worth thinking about how you are planning to prime the pump before building the system. In our case we found that placing the pump below the water intake level, and then not gluing one of the fittings so the intake can be trivially turned up and used to fill the lowest foot of the system was sufficient. However, what works will depend on how your system is constructed. The important thing is that you have a way to flush bubbles out of the path from the intake to the pump. 

Notes: 

• 3" pipe is much more expensive than 2". Make sure to do flow tests to determine which you need before purchasing your piping (3" is probably overkill).

• Placing "spoilers" or some other mechanism to slow water passing over the holes should help increase flow.

• Make sure the pump is below both the intake and the outtake to the system. That will make it much easier to prime.

• Any fitting which changes the direction of water such that the flow pushes against it should be glued or clamped in pace.

• Having at least one flexible fitting in each straight run to reduce the risk of cracking is well worth the extra cost.

Water Fall

After a bit of back and forth, we decided to start the river off at a waterfall and end with a catch basin (vs flat with recirculating water). That helped us hide the pump mechanism, and gave us an impressive backdrop to the left for folks entering the North Gate.  Ultimately, we ended up building a platform, and then using a single contiguous piece of thin plywood to form the upper basin for the river. That worked reasonably well, but I'm not totally happy with the solution we came up with, so rather than post a detailed build log, I have included a few lessons/ideas that we picked up along the way below.  In a similar vein, you will also find - below - notes from our post-project design review detailing how we think the the waterfall could be done best, and with as little pain as possible in the future. 

The general design that we settled, more as the result of time than anything else, was an 8' by 8' by 4' frame made out of 4x4s and braced with 2x4s. We then used 2x4s of varying heights to bend a single sheet of 1/4" plywood so that it would direct water over the intended edge. The water itself was provided by a 3" pipe with holes drilled in the bottom. The waterfall overflowed into a 2' by 8' by 1' catch basin and from there into the river proper. 

Notes: (Design Review)

• Check the waterfall distance/behavior before building a catch basin for it, could be it needs to be larger than you expect.

• Screw a line of 2x4s 3 '- 4' below the top of the platform where they can be used as scaffolding (a built in ladder is really nice as well).

• Using an upper basin with the water spilling over a lip will help create a nice even sheet of water.

• Creating the upper basin and structure desperately may make it easier to maintain the basin and keep it rigid.

• Make sure the Calk you use is rated for water (oops) and that you finish early enough to let it dry for 2 days before the party.

• Building a ladder and some scaffolding 2x4s to allow easy access to the entire structure (would recommend a single line running 4' below the top) would make maintenance and assembly much easier.

Notes: (During Construction)

• Calk not hot glue!

• The top of a tall structure like the water fall will flex enough to break wood to wood calk bonds when picked up and moved.

• Black plastic can be pained, although it stops being waterproof if you use staples.

• Plywood bends way way better when wet (soak for 2-4 hours in warm water).

• Surface tension means that getting a uniform sheet of water from a flat surface is hard. If you need even distribution it can help to build a small lip and then cut channels through it.

• Clear plastic drop cloth from home depot turns actually clear under water (whenever possible better than black plastic).

• You can soak thin plywood sheets and then bend them to get continuous water tight surfaces as needed.

• Water will stick to drop-cloth and adhere it to nearby surfaces, so if you have leaks you need to direct towards more productive destinations than the bricks, that can be a good way.

• Most leaks don't really show up until the wood and plastic have had a chance to saturate. That takes around 20 minutes, but once that's take place they don't seem to get much worse until the wood starts to warp (by which time interhouse is hopefully over).

Pictures: 

Because pictures are never a bad thing.

[Metal Working] My First Pen

Story:

A few days ago I found myself in the unenviable position of needing a pen - for the first time this term - and not having one. Now, this is a problem which is solvable in any number of ways, but since I had some spare brass stock and a left over Parker insert I decided to take the opportunity to try my hand at making one. 

Dimensions: 

The pen is 4.1" long and made from 3/8ths inch brass stock (filed a bit to smooth it out). The inner bore is 0.222" across and 3.5" deep with a 0.1" hole drilled to meet it from the other end and 0.7" of 1/4-20 threads on the cap side. The nose of the pen was hand filed to about a 7-8 degree slope and the grip is composed of 14 grooves at 0.050 spacing. The decorative groove by the cap is 0.164" distant from the top of the cap and the end of the pen has a 45 degree chamfer to smooth things out. 

Operations: 

These are a summary of the operations that I used to complete this project. I've recorded them since the pen is generating a lot of interest and I want to be able to provide some amount of guidance to others who are interested in making a pen as-well. That said, like all first attempts this one resulted in a fair few "learning opportunities" so if you are considering making a pen yourself please take the following with a grain of salt and be sure to check the notes for any updates. 

• Chuck and Face the piece. 
• Use the tail-stock to drill main 0.222" bore (peck drilling becomes really important here). 
• Tap the end of the piece. At this point you can also add a chamfer if you so desire. 
• Screw a screw into the end of the work piece and turn it till it is concentric (if you have the ability to turn between centers that would work to).
• Flip the piece around with 1" sticking out of these chuck and face.
• Use a center drill to make a hole for use with a live center. 
• Put a live center in your tailstock  and mount the piece with the screw gripped in the chuck and the front end on the center. 
• This part is a bit tricky, you want to measure out the location of your grip (and any other ornamentation ) and cut it. This is also a good time to do as much of the surfacing work as is practical. 
• Next, re-chuck the work piece with the end exposed. Face/cutoff the end till you are at nearly the final length of the pen. 
• Use a 0.1" drill (or similar) to make the pen-tip hole. 
• Use a file to make the taper and then sand to match the rest of the finish. 

[Metal Working] Marble Tower

Summary:

I first ran across this project while browsing google photo's for "machining projects" and it seemed like a great way to get some practice dealing with backlash on the mill. When I ran across 3 aluminum disks in one of the shop scrap bin, it was a no brainier second project.

For this project I wen't with with a simple 5x5 pyramid, but in principle one could cut a much more complicated base pattern. Spheres pack pretty well hexagonally as well. I still have 2 more disks, so at some point in the future I may make a variant of this project with a more complex hole pattern. 

Like any good second project, this one involved a fair number of "learning opportunities" along the way. Most will be obvious to a more experienced machinist, but I have included a short list below. 

Lessons Learned: 

• When making a super glue arbor it is important to cut grooves to hold the super glue. Otherwise, the glue tends to bunch up and prevent the piece from sitting flat. (If I was doing this again I would use soft-jaws instead of a glue arbor).

• Freshly cast aluminum is very "gummy" which makes it a bit tough to work with. Fine for making the arbor, but if other choices exist those'd be better.

• Double check that the end mill used is a ball nosed rather than a bull nosed.

[Metal Working] Copper Rose

In honor of Valentines day, I figured I'd take a shot at making a copper flower.  I used 28 gauge copper sheet for the petals and 1/4 inch brass round stock for the stem. 

This project is pretty well documented in a number of places online (see link in the process section) and from my experience seems to turn out a nice product even with a fairly large number of small mistakes along the way. If you are looking for a nice evening project, this seems like a great option. I chose to do this build mostly with hand tools (and the lathe) but it'd go a lot quicker if you used a water jet/laser cutter to shape and texture the petals. 

Process: 

I roughly adhered to the following instructable (click me) with a few notable modifications. 

• I cut each set of petals pretty roughly and used a belt sander to get the final shape. 
• I found it pretty hard to texture with a crow bar and used a chisel instead. 
• While texturing the sepal I introduced a few annealing steps on the stove to prevent the copper from tearing. 
• I turned down and threaded the end of my stem and used a nut to hold the petals to the stem. (I also used a file to round the end of the stem.)
• I used a small quantity of super glue to hold each set of petals in place.

Notes:

• Parts could be water jet instead of cut with tin snips for significant time savings. 
• The 40 Watt laser is probably capable of etching a lot of the texture lines. 
• The super glue worked fine and is a lot easier than welding/soldering. 
• Variations in petal size should be avoided where possible since that creates gaps between each layer of petals. 
• Cost: 12$ (Unit cost for multiples of 2)
• Time: 7h (4h petal and stem prep, 3h assembly and patterning)

[Hell Lighting] LED Installation

Summary:

The lights are up! There is still some work to do with wiring and splicing before we will be ready to add power and control, but the LEDs themselves are now fully installed. 

Details: 

We took a few design chances this time around. In particular, the purgatory side of hell is bridged as a triple arch (see picture) rather than a single arch, and the bathroom side of hell is now bridged with a straight set of lights running across the far wall. As a result, we ended up with a much larger lighting shortfall (10m) than we had  anticipated, but between Francesco, Brian, and myself we were able to make up the difference from personal supplies and the project now has a few meters of spare lights should repairs be needed in the future.

The strips are held to the ceiling with 1" strips of 3M outdoor double stick tape placed every 6 inches. What remains of the no-stick backing on the strips themselves was also removed, but it seems like strip adhesion is unlikely to be a significant factor in holding the strips to the ceiling (their adhesive is pretty bad). We ran a 2 month test with tape every 8 inches and got no hint of peeling, but if we run into issues during my time at Tech I will update this page. The process:

Installation:

One person was responsible for cutting strips of tape and placing them along the path of the lights. This took place over the course of 3 or so weeks with the last half being done today while the other groups worked. This probably does not need to be done beforehand.

One person was responsible for soldering together smaller strips into larger ones. This ended up not happening as fast as the other groups worked which meant some of the splicing had to be done on the ceiling. Not ideal, but actually pretty feasible. In future rounds, I would suggest this happen beforehand, even though it worked fine to do splicing concurrently.

Two groups of two people worked as teams to put up the lights themselves. It seems like the pattern that worked best was to have one person working ahead removing 2/3 tape backings in blocks of 16 or so. That let the second person roughly keep up while still being able to place the lights. It really helps if the people putting up the lights have long nails (or sharp knives) since the tape backing doesn't really want to come off.

The whole installation process took about 4.5 hours from start to finish with an average of 5 people working throughout.