Where chunky_milk has been

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Tuesday, July 28, 2009


I'm lazy and have not had anything interesting to write about becuase I have not done anything notable since May.

New address:

I switched because blogspot is poorly organized and just doesn't run very well. The new website it much easier for me do and requires a lot less effort.

Thursday, April 9, 2009

Formula Hybrid Testing

The car has been out for 4 hard days of testing and a few more quick runs behind our building. The purpose of these tests is to run the car hard so that anything that can break will break here where we can fix it, instead o fin the middle of a real race. The car weighed in at around 500lbs with a full fluids and ready to race tires. With a little care we could weigh in 400's which is somewhat competitive in the non-hybrid races, and unheard of in the hybrid competition. Another benefit to our minimalist hybrid drivetrain is that we might have one of the most powerful engines in this competition. Our drivers have been training for months in one of our older cars while waiting for the new one to be ready to run. We've been tweaking the spring stiffness, anti-roll bar stiffness, tuning the hybrid controller, and checking for sound levels. Ok I have to go now, but here are some videos:

Failing the sound test by 1db, but it's an easy fix

A quick video of us driving on internal combustion engine only. With the electric system entirely shut off it should still be faster than the winner last year.

Formula Hybrid Assembly

Me and the Texas A&M 2009 Formula Hybrid car

We (the Formula Hybrid team) spent the entire Spring break wrapping up the build of the car. Building takes forever because there are a million little parts, welds, and little details that were overlooked during design. Multiple parts had to remade because they didn't fit, didn't work, or interfered with other parts. There were no major screwups, but a whole lot of little ones.
A 3d model of the hybrid powertrain
By Wednesday the build room had been converted into a paint booth, and the car was painted. The paint dried for a few days, and Friday at 5Pm we started assembling everything. While the rest of my peers were partying it up on Spring Break, we were busting our butts on this project.
The steel space frame chassis being painted
Assembly started at 5PM and by 3AM the car was assembled and on the ground rolling. The next week was spent wiring the engine, electronics, high voltage electronics, motor, and batteries. We had a deadline of Friday, March 27th to have the car assembled. That Friday was the rollout presentation in front of a board of engineers who reviewed and critiqued our design. We were ahead of schedule, and even took the car on a test drive the night before. We were the first design team in A&M Racing's history to have a car driving under its own power at the rollout presentation.
The car at the rollout presentation
This left us with just over a month to test and tune the car. Our theory is that winning teams have 1) a reliable car 2) a fast driver 3) a fast car. By getting out to drive a full month before the race day, everything that could break during competition will have already broken and fixed. The drivers will have hours and hours of experience driving this type of car and get the feel for it. So far we've had 4 hard days of testing and tuning with only 1 problem. A wheel speed sensor, which is a small metal ring resembling a gear, unbolted itself from the motor. The manufacturer right hand bolt hole in the end of the motor shaft, but it needs a left hand because the motor spins in a direction that tries to constantly unscrew the bolt. Loctite (superglue) solved the problem. Also, the carburetor keeps trying to fall off because the junky connector is plastic. It has been amazingly reliable, fast, and easy to drive considering we were all inexperienced in this and certainly none of us have ever tried to build a hybrid car before. Nobody knew for sure how it was going to perform as a hybrid because of unplanned interactions between the electric motor and the internal combustion engine. It works just as planned, despite what some of the more vocal engineers on the advisory committee thought. Next week we will be practicing for the design event and bossiness presentation, which means I still have alot of work to do. We will be driving to New Hampshire from College Station, which is a 6-day, 4,000 mile round trip. We have to tow the car, 3 sets of wheels and tires, a spare engine and motor, tire machine, full set of tools, and the welder, so we will be towing a monster trailer.

The car and the team completely assembled

Here is a little video of the assembly of the car:

Monday, March 2, 2009

Climbing at Reimer's Ranch

There's not really a whole lot to say about this trip. I went rock climbing at Reimer's Ranch near Austin TX for the ~50th time with my friends Les, Natasha, and Bookout (Steven Bookout- "like check a book out" as he always explains).

Reimer's Ranch is a very small county park that caters to limestone climbing and Mountain Bikers. On a busy day you might see 20 or 30 cars in the gravel parking lot. It costs $8 per car, and there is no camping allowed. There are well over 100 climbing routes, all bolted, and all very short. An average climb is around 40ft, and some might get up to 90. It's the best climbing that can be done in a day trip from home, so I'm here as often as possible.

Instead of writing alot, I'll just show you a bunch of pretty pictures.

I don't suggest trying to lead a 5.12c at the end of the day when you are already tired. We both made it a little farther than this past , but kept falling back down below the hard part. After each doing the hardest part of the route a couple of times, , falling, and repeating, we gave up and got cheap greasy burgers in town.

Natasha's first lead!

No feet required

Les getting ready to climb the hard stuff

Monday, January 26, 2009

Honey Creek Cave

The four Aggie Cavers deep in Honey Creek Cave, the Longest Cave in Texas

Honey Creek Cave is the longest cave in Texas, with more than 20 miles of passages. The entrance is on private property, and cavers are permitted in the cave on rare occasions, so it was a special to invited on the trip. I've made it to two of the three trips that occurred since I joined the Texas Speleological Society. Honey Creek Cave has been actively explored since 1984. Most of the passages have been pushed, but one ends in a sump, which is a water filled tunnel. On the first trip I attended last year, we hauled scuab gear and a diver swam the ~1500ft sump and esstablished that it continued as a dry passage. There is rumour that it may connect to nearby caves, making it a giant network of wet and dry tunnels. The purpose of the most recent expedition was to send two divers through the sump to continue exploring the new dry passage.

Drew cools off in the water because his 9mm wetsuit is way too hot

The cave entrance is on local property outside San Antonio, Texas. In 1984 a few Texas Cavers discovered the cave, and located a good place to drill a second manmade entrance to make it easier for cavers to access the cave. The deal was that the cavers would go in the cave, locate a spot, and drill a well for the owners allowing caver access. The well shaft was enlarged to 30" with dynamite, and a telephone pole structure was installed to allow a tractor to lower cavers down on a cable. The manmade entrance shaft puts cavers near the middle of the cave, cutting the round trip down to one long day instead of an overnight ordeal.

Krishna being lowered down the manmade entrance shaft by the tractor and cable

Most of the cave is wet and requies you to wear a wetsuit to stay warm. Cavers also need a helmet, headlamp, kneepads, harnesses, carabiners, knee and elbow pads, and a day of food and water. This cave is the "Ironman of Texas Caving." It requires virtually every caving technique there is: diving, swimming, vertical, crawling, stoop walking (which sucks btw), mud crawling, and "salamandering." Salamandering is floating on your stomach and using your hands and feet to push yourself throught he water. A Honey Creek Cave specific technique is also mud sliding.

We also volunteered to bring two suba tanks to the dive site at the sump. Each tank weighs >30lbs, and is a major PITA (Pain in the ASS) to carry. We had to carry tanks in addition to our own personal gear. There may have been 20 minutes in the whole trip where I could stand upright at all. You can't wear it like a backpack because you are constantly getting up, getting down, or crawling. On dry land where you are belly crawling, you have to push it ahead of you, or drag it behind you. Teamwork was needed to pass them over obstacles and to protect the delicate brass valve, which would be extremely dangerous if it failed. They are not such a PITA in the water because they float (due to foam padding). You can swim and push them ahead of you with your face, like a giant 3olb water polo ball.

Me with the Scuba tank (wrapped in foam to protect it)

This is one seriously tough cave. Even though it's one of the greatest adventures of caving in the Southwest, few actually sign up for trip of this magnitude. 21 cavers in total made it to the sump, each carrying loads such as Scuba tanks, Buoyancy Compensators, or cave radio pieces. Cavers came from all over, including Oklahoma, Alabama, Louisiana, Missouri, Florida, and I think Alaska too. The whole trip lasted from 9AM to nearly 2AM, or much later for the slowpokes. The trip actually went much quicker than expected.

The secondary purpose of our trip was to map the cave accurately, and to propose a location for a new entrance shaft that bypasses diving through the sump. Very few people have the gear, experience, or balls to dive a sump a days crawl away from safety. This sump is even more dangerous because of the silt, which makes the visibility just a few feet. Also, the walls of the cave are confining, making it a tight fit with all the scuba gear. We borrowed a Cave Radio, which a very low frequency closed-loop transmitter encased in rugged PVC (homemade of course) housing. It transmits one frequency, and can be received on the surface very accurately, within inches. Cavers set up the radio, and transmit for a specified period at a scheduled time. People on the surface wait for the signal on the surface, near the spot they suspect the cavers will be transmitting from. The hand measured and plotted map was used as a reference point, and the received radio point was only 60ft off! Very impressive mapping skills from the Texas Cavers. Only two of four transmissions were received well because of interference such as metal fences and barns.

At the sump. Believe or not, he is standing in water. Unlike mountaineering, the best view is not at the end of the journey!

The trip was not a complete success. One of the Scuba tanks developed a slow leak, possibly from rough handling while being dragged though miles of rocky cave. By the time everyone reached the sump, the tank was empty. Only one diver swam the sump, so that we could at least send a radio transmission from the other side. We had to wait for hours to wait for a few cavers who had missed a key turn and gotten lost to bring the buoyancy compensators. The room where we waited in for a few hours was what most sane, claustrophobic, or clean-freak people would consider muddy hell, if hell were cold and smelled like caver farts. Wetsuits are only warm if you're moving, otherwise they are frosty! I caught a quick nap in one of those foil emergency blankets and ate four of my six powerbars. With 21 people in one crowded room, the air quickly turned bad, and I suffered from a stout headache and nausea. It took every ounce of my willpower to get over my exhaustion, headache, and weak stomach to get moving away from the bad air. An old caver trick to test the air is to watch a lighter burn. The distance the flame is away from the lighter tells you the air quality. I don;t know what the normal distnace is, but the wasn't too bad, unless you were breathing it for 5 hours. Half an hour later after I got moving all my symptoms subsided and it was a sprint to the finish. Only me and one other person had trouble with the bad air. I had a lingering cold and he was devoloping the flu, so that is likely a contributing factor.

I think the worst part of the whole trip was the 34 degree weather outside. The bottom of the cave was filled with a thick fog where the "warm" (read warmer) air met the cold air. My hands froze so quickly that I could barely get my harness on or tie knots in the rope. Once I got to the surface, someone in a down coat had to help unscrew my carabiners and untie knots. I felt pretty ridiculous wearing a caving helmet, a wetsuit, and a rock climbing harness, and holding a scuba tank in the freezing weather at 2AM in the middle of the Texas plains. Cave Diving is the perfect sport for the caver-diver-mountaineer-climber who can't decide which sport is best, and settles for just looking confused to regular people. This was a pretty tough trip, but definitely one I will never forget, although I was dumb enough to do twice.

Monday, January 19, 2009

Building the Formula Hybrid Car

The chassis team leader putting the 4130 steel frame on the jig

This is the 1st post on building the Formula Hybrid car, there will be more if I am not busy building the car to write about building the car. The only reason I have time right now is because I managed to get myself sick by working all day every day instead of sleeping. Hopefully tomorrow I will be back in the machine shop, making the motor mount on the mill.

CNC (robotic) milling a block of aluminum to make the motor mounting plate
The team has spent nearly 6 months designing thing son paper, and just two weeks ago we made the first cut of metal. Since this is a hybrid car, and none of us had any experience with hybrid drivetrains, the motor and control tea started working on this last January when the construction of the 2008 car was just beginning. Now 1 day shy of 1 year later, we got our hybrid drivetrain to run this morning, Hurray! The design team is composed of 7 teams:

-Suspension, brakes, wheels, and tires
-Chassis, cockpit, and body
-Motor and Controls
-Batteries and High Voltage
-Low Voltage and Data aquisition

The engine is mostly stock (if Nascar is "stock" than so is this) so there is not too much work to do there. Our car will also have onboard engine, motor, temperature, and battery monitoring sensors as well as wheel speed sensors, GPS data logging, 3-axis accelerometers and suspension travel measurements. The software we use plots all of these on a GPS acquired map of the course, and allows us to tune the cars suspension, engine, and motor.

A 3D model of the front suspension and steering allows us to test for structural integrity based on spring compression, tire friction and roll stiffness during high g corners.

The teams are 2-3 people, except chassis which has 4 (and needs 7). There is an 8th team, called the "architecture team" that decided how our hybrid car would be put together. I am on the motor and controls team and the architecture teams. We are the hybrid part of the hybrid car. I am the only mechanical engineer on the electrical side of the design. There are really two architectures of a hybrid car- series and parallel. A series car is essentially an electric car that has a gas powered electric generator. It is efficient because the engine can always spin at its optimum speed, but heavy because it must have big batteries and a generator. Most Formula Hybrid cars, including every winner, has been this design. A parallel hybrid car is like a regular car, except that the electric motor is much smaller, and only helps out the gas engine when it is not powerful enough. The motor and batteries can be much smaller and lighter to achieve the same power. Decreasing weight is a great goal for a racecar, and the reason we chose this method. The drawback is reduced fuel economy. We don't care about fuel economy because we are racing against the clock, not the gas tank. Lighter is faster, and that's what really matters (in racing, not highway driving). This method is more complex to pull off in terms of electronics and many times more difficult to design around. The engineer must balance the weight of the motor and batteries and motor against the power gains to select just the right size and configuration.

The Yamaha WR 250 engine, still in the bike for early tuning, with titanium exhaust

Our design will use a 250cc Yamaha dirt bike engine. It's small, but can put out plenty of power for its size. It will also have a very nice titanium muffler kit and an autoclutch. The electric motor we are using is actually an industrial forklift motor. We will be using two boxes full of powerdrill battery packs to power the motor. To recharge the batteries we are going to use the drill companies chargers plugged into our car. We will carry about 30lbs of batteries compared to nearly 300lbs that other teams have used. Also, we modify the battery packs to get nearly 5x more power out of them. A very fancy electric part called a GFI senses if there is a short circuit or someone touching the wires, and automatically shuts down the batteries to prevent injury.

One of the welders uses tungsten-inert-gas welding to put together the frame

The team is working steadily, and we hope to get done in about 10 weeks. That's a tight schedule. Most teams spend a few months designing and a year building, not the reverse. However, no matter how well constructed your car is, you can't win with a bad design.

Formula SAE Driving

Me driving the 2006 1st place Formula SAE car, converted to stock

The Formula Hybrid team has been busy 24/7 since just after the new year working on the new car. Just for a relaxing day, we took the old car out for a fun day of driving. Last semester a small handful of the team took the task to fix the 2006 Formula SAE car, which won the 1st place in the competition, and won the Road&Track magazine's Triathlon trophy. It previously had a supercharged single cylinder ATV engine , custom exhaust and intake, with an $5,000 aftermarket engine controller that mapped the ignition and injection timing by reading the manifold pressure, speed, and throttle position sensor. If that didn't make any sense don't worry, it was really cool, really powerful, and really unreliable (surprised?) We removed the siezed engine, and replaced it with a stock engine, stock exhaust, and a carburetor. After that we tore out the entire wiring harness and started over. After fixing the shifter and suspension, it was time to drive.

Suited up and ready to drive

I got the opportunity to drive the course first yesterday. It is a very tight autocross style course that limits your speed to less than 60mph, but can require turning at ~1g. Our practice "track" is actually a crappy old runway covered in dirt and grass, oh well. Driving one of these cars requires special safety equipment: a thick engine firewall, five-point safety harness, fireproof suit, gloves, and shoes, a helmet, and arm restraints. The arm restraints tether your arms to the car so you don't break them when the car flips. Rolling the car is pretty unlikely, because the roll center is only about 10.5" off the ground, nearly even with the center of the wheels. The car would have to lean nearly 90 degrees before it would roll over! This leads to very good cornering performance. We also took this opportunity to familiarize the car to potential drivers for the future. A few people we know through various connections who are not on the design team have Formula and Kart racing experience, and may be driving for us. Most of the design team members are engineers, not drivers. Our only experienced driver is about 6'4" and 300lbs, which means he just won't fit. At 6' even, and 170 lbs, I am at the very limit of what fits in the car. It was designed to fit only one driver, and he was much smaller (and faster) than me.

Patrick wondering why the clutch won't work, turns out the cable snapped

The clutch cable snapped after a dozen laps, but we brazed a new connection on the old one with a blowtorch, and got back to driving. I left early that day but a few hours and many laps later the differential threw a few bolts, resulting in some destruction and complete loss of fluid in the drivetrain. by evening the problem was diagnosed, a snapped bolt had punched a hole in the custom made differential case. By 4:00AM the drivetrain team had the parts out of the car and on the operating table. We will have to manufacture a new case for the differential and refill it with fluid, which is the best we could have hoped for. These racing differentials cost $2,700 apiece, plus a few more k for CNC machined mounts, bearings, and joints.