A few months ago Aaron and I made a nice maple cutting board. It turned out well, and therefore deserves a blog post. I haven’t really done much woodworking, this was definitely my first real woodworking project since high school.
All woodworking starts from an average-looking wood blob. However, this block started out special: it was curly maple, which will give the final cutting board a very interesting 3-d looking pattern. Additionally, this wood was special, coming from a tree grown on the farm owned by John Quincy Adams, which is cool.
The boards were cut to length and then jointed on three sides.
The boards were then planed to 1.750″ thick, TO THE THOU!
Next up was deciding on the arrangement of boards. Two of the boards had slightly darker areas, and some of the boards had particularly curly areas or knots. The knots were aimed down and the darker wood put on the outside. Once we were satisfied with the layout, it was time for some glue.
I used a bit too much glue, Aaron’s glue application technique was perfect tho. Then we clamped the board.
While the glue was drying, Aaron and I finished up a great experiment which we had prepped before. We had two different sourdough starters, made in different states (his in MA, mine from VT). The two starters smelled quite different, Aarons smelling somewhat like apples and mine smelling more like vinegar. Using these starters, we made two identical loaves of sourdough, kneaded in the same way, for the same amount of time, from the same flour, etc. We did a taste test once the loaves were done.
The results: The two loaves tasted the same, but were ever so slightly different in both texture and smell. It was possible that the texture differences were due to slightly stronger kneading by Aaron, however the smell was ever so slightly noticeably different between the two loaves.
Once the glue had finished drying, the board was squared up on the table saw. We went for some vague dimensions which Mike had texted us as the biggest board which would fit on our countertop. The board was pretty big though. Nice and heavy because it is maple. We then routed the edges and sanded the whole board. Once the board made it back to my apartment, it was time for a liberal layer of mineral oil. The oil revealed the board’s true color, which was excellent.
And, the curly maple became clearly visible! It doesn’t really show in photos too well, but it looks beautiful.
A quality project. The cutting board made it to the lake for the great MITERS Boating Adventure.
Yeah…. I sawed a lithium battery in half. With zero fires. Pretty insane. I’m basically a ballr.
The need for sawing a battery in half arose while working on the electric moped. FSAE had several 1.6kWh packs which had weird issues, namely that they *occasionally* would short out to their cooling plates. Not hard shorts, just a few hundred kohms- but this is enough that they would slowly discharge, and more importantly, fail the rigorous isolation tests in FSAE rules. Therefore, these packs were not suitable for racecar duty, which meant that they were generously donated to the slums of MITERS.
Despite the shorting problems, the cells in these packs are really good cells which are barely cycled. Unfortunately, these packs are somewhat of a strange aspect ratio. They are only 60V but have 27AH of capacity. I could have opted to build some other pack out of A123s for the moped, but these packs are really, really good, incorporating features like fused busbars and temperature sensors on top of very high quality cells. Ultimately these packs were too good to not use. A few options existed for converting them to useful moped battery, which ideally needs to be at least 200V.
Somehow dissolve the epoxy out of the packs and reuse the cells.
Somehow re-terminate the pack to make it into a 180V pack.
Get good at power conversion- build the infamous boost converter!
Boost converters are notorious for exploding at MITERS. But, they are cool and posed an interesting challenge, so I decided to go with option 3.
The original battery plan involved a single moped pack and a 4x voltage booster, for a final bus voltage of 240V. Geometrically, this fit pretty well within the moped.
After looking at this setup for a while I realized it might not actually be enough battery. The electric bike does 30 Wh/mile, and at higher speeds the moped will probably need about 40-50 Wh/mile. With only a single 1.6 kWh pack, 50 Wh/mile only results in a weak 32 miles of range. Additionally, I looked longingly at the pile of FSAE batteries destined for the trash, and felt I needed to “save them”. So I came up with option 2, which uses a second battery to boost voltage a bit and a significantly smaller voltage doubler booster. This solution saves money, is more efficient, and will have longer range.
This plan was bad. A full battery wouldn’t fit in front of the motor without hitting the front wheel, so it would need to be sawed in half. Bring in the bomb squad. Let me repeat: I would need to saw a lithium battery in half. Any person with access to the internet knows that this is a recipe for an extremely large fire. Even the smallest puncture of a cell can lead to a fire, not to mention sawing one in half. However, it was not as bad as it could have been. The pack I wished to saw was an 18650 pack potted in epoxy, so it was hypothetically possible to saw around the individual cells without compromising the whole pack. Hypothetically.
So, onward!!!
I located a battery from the pile which was already compromised. This battery had a fault on one cell, so the row that cell was in had been cut up. Also, the bridges between the cells were cut for whatever reason.
It turned out that this pack was perfect for what I needed. First of all, the connections between the cells were cut, so this battery presented no high voltage hazard, and could not be shorted as easily. The compromised cell was in the 11th row, meaning that a 10S pack would be left if the battery was cut at that location. Therefore, with the other battery inline for a total of 26S, the total pack voltage would be about 100 volts, easily doubled to a happy 200V. For big high speed power, this could even be tripled for a bus voltage of 300V, but with my gear ratio that would push base speed up past 50, which is overkill for daily driving. So, 200V it is. Also, just a single doubler is easy to make, easy to package, and very efficient.
First up, I ripped off the baseplate of the battery. All the issues of this battery stemmed from the thin epoxy bond between the bottom of the cells and the baseplate. Hypothetically, removing the baseplate should simply remove the problem! Removal of the baseplate was accomplished with large effort through a combination of slow rocking, prying, and yelling.
The battery was placed on the chopping block.
The original plan was to use a very fine coping saw to saw in between the cells. However, the epoxy proved to be incredibly abrasive and would dull the saw after just a few strokes. So, time for plan B….. saw straight through the cells themselves, which are softer than the epoxy.
What?
Yep. This battery is worth destroying several cells to use. One cell in that row was already compromised anyways. But, how to saw through cells? Cells usually explode when you do this, because all the stored energy in the cell is released at once when the cell shorts. I just soldered some resistors to the cells and let them discharge overnight. In the morning I resumed sawing. I first sawed into the edge cell. Sawing the cell proved to be very bad, but with some amount of force the cell was excavated.
I then decided to try drill the cells. This worked great. It was a little challenging but was eventually accomplished. When all the cell cores were removed I then sawed through the thin layer of epoxy between the cells.
Once it was mostly sawed I just cracked the rest.
Less bad than I was expecting!! Just one night of cell discharging and one night of drilling and sawing.
The “freed” 10s pack.
In summary: this pack had a dead cell anyways, and was headed for the trash. By careful drilling and sawing, the bomb was diffused and this pack will hopefully propel me on my moped. Stay tuned for more moped shenanigans!!!
Once or twice a year, something special happens. Something you don’t normally see. Something so incredible, its worth writing a blog post about: The members of MITERS go outside.
Hear Ye, Hear Ye: its time for the legendary, certifiably insane, MITERS BOATING ADVENTURE. That time of year when we use our big brains to make magical machines which defy physics by not sinking and occasionally exhibiting forward motion.
Usually, every boating adventure revolves around a “main event” of Dane’s creation, such as the Doom-Winch or the boat named Three Wave Rectifier. However, this year a different scheme was proposed: the MITERS Air Mattress Speedboat Regatta. The rules were simple:
Primary flotation must be provided using at least one air mattress.
Bus voltage is limited to a maximum voltage of 72 V.
Only a few things were banned, mostly due to noise concerns:
Leaf blowers
External combustion engines (pulsejets, we’re looking at you Mike)
Everything else is allowed: sails, oars, underwater bicycles, hydrofoils, etc.
Anyways- LET THE BUILDING COMMENCE!
No access to MITERS this time made construction slightly more challenging than normal. However, we all made do in our various back yards. Mike decided to make, of all things, a CATAMARAN SAILBOAT. He utilized CAD (Cardboard Aided Design) to make the pontoons, which were spaced exactly to straddle an air mattress. Fred came over to help construct everything.
We also converted an old RF dish into a solar cooker, using several sheets of aluminum foil. The aluminum foil was only vaguely flat though, so it didn’t focus very well. The focus area was about 6″ around, so sadly a hotdog only gets about 10-20% of the incoming solar radiation.
Savva found some nice 6″ ducted thrusters on the loading dock. I did some scoping to determine if they were brushed or brushless, and eventually the proper phase wires were located.
We both made semi-legitimate 2×4 frames to attach them to air mattresses.
Savva and I went shopping at Market Basket. They had some cheap ribs and watermelons.
ONWARD! We rested well and waited for the day to come….
Aaron and I got to the lake a little later than planned, at around noon. Surprisingly we fit all of this stuff in the tiny Honda Fit.
My air mattress contraption was horrendously slow on the 4s battery I brought, so I was forced to accept a tow by Aaron. Luckily, the motor controller could take a 6s, so we upgraded later in the day.
The others began to arrive and finishing touches were added.
Miraculously, Mike’s catamaran floated, even without an air mattress. But we added it anyways just in case.
After a brief tow out to sea, Mike’s thing actually, wait- is he actually sailing?
Mike’s thing ACTUALLY VAGUELY WORKED. A catamaran sailboat made in literally 12 hours. NOT BAD, MIKE!
Dane’s aluminum and strapping thing also worked pretty well. He was quite content.
Birkel made this simple trolling motor contraption. Look how happy he is!!
ONWARD!!! TO THE ISLAND!!
Aaron’s boat, as usual, was the workhorse of this adventure. However, this is unsurprising, as it was an actual off-the-shelf product propelled by an actual off-the-shelf gas moter. No points for creativity, but points for reliability and usefulness. This was the designated “lifeboat” of the regatta, despite at least three leaks on the hull required a few pumps every minute or so. Shows you how much confidence we have in our vehicles.
Fred came prepared. This vehicle had a trolling motor attached and somehow drove backwards quite well. More on this later.
More on Fred’s thing later.
A base was established, and sausages were cooked. About a month ago, our neighbors gave us a cast iron pan. We used it to cook bacon here with about a 50% success rate. The fire got really hot!!
Group photo!! 😀
The solar cooker provided entertainment for the weak-minded individuals (just kidding mike)
Someone made some potatoes which inevitably tasted as though they had been heavily seasoned with ash. Some brave souls ate them though.
Lotsa boats!!!!
The sacrificial hotdog. After about 2 hours the hotdog was warm to the touch, but I ate it anyways. Next time, better aluminum foil.
Fred brought this WONDERFUL contraption which was the bucking bronco of boats. It was a trolling motor with a contactor and some dodgy pedal steering device. On a massive boat, I’m sure this trolling motor could move you from point A to point B at maybe half a mile per hour. However, on the air mattress, this thing RIPPED. It also could steer, so it would pretty instantly throw off the rider when on setting 5, the maximum setting.
And finally, THE RACE OF THE MATTRESSES!!!
Savva and I both had used the bad thrusters which really lacked enough thrust to actually move an air mattress, so rather than failing independently, we attached both thrusters to the same air mattress and decided to commit to failure together. We all badly maneuvered into position:
And we’re off!!
I don’t know who won, but I do know that Savva and I finished dead last, no questions asked. We were beaten even by Cairan, who’s motor had broken and resorted to paddling. Lol.
Anyways, we enjoyed the rest of the day, humbly admitting defeat. We attached two air mattresses, end to end, to make a NIMITZ CLASS BATTLESHIP:
I brought my nice cutting board and we cut up the watermelon. Yum!
A quality day!!! Stay tuned for the next boating adventures!!!
Wow this post is SUPER LONG- if anyone actually read this far, let me know why you read this whole post lol.
