Wednesday, May 28. 2008Closer to leaving the ground...
Tried really hard today, but never made it off the ground.
Today I did a lot of math regarding the lift of a non-airfoil wing. From the math and review of the videos, my best bet is that we aren’t properly maintaining the right angle of attack during takeoff. The leading edges aren’t near strong enough either, but that’s something I can’t fix (if anyone knows where to get thin wall aluminium tubes I would love to purchase two…) In any case, I will be in NJ at the end of this week. I have a couple ideas as to increasing the angle of attack. I’ll be sure to post pics, and with any luck video of some flight! Sunday, February 17. 2008Radios Radios Everywhere
I got my pretty new radio a few days ago. My Motorola XTS 2500 is quite nice, I have to say. It’s the second to most epic handheld Motorola makes. In addition to the things my HT1250 does like MDC signalling and whatnot, the XTS series supports APCO Project 25. This standard, P25 for short, is a digital protocol for signalling and voice over radio. It’s mostly used in the public safety bands, since digital works better than analog covereage (in general: if the packets can be pulled out of the noise at all, the original audio is maintainted). Kurt, N1PFC came by and helped me program the radio for all my various Ham things in the area (I didn’t own a VHF handheld before so this list is pretty extensive) as well as his P25 Ham repeater not far away.
In other news, I finally got around to doing my Extra class ham license. I got a new call sign while I was at it, and as such I am now NA1C. Thursday, January 24. 2008Talking to Space
In an effort to promote radio and space to other WPI students and staff, Theo, KC2RMJ and I (KB1OZL, now NA1C) put together an event with WPI Wireless to talk to the International Space Station during a particularly good pass last November. I found the pictures of the event and thought they were nice.
I put together one of our (WPIWA’s) smaller towers for the event, and kept it outside my apartment for a few days leading up to the event. Also, I built a 2 meter J Pole antenna since it had pretty good gain at the horizon to help lengthen our window. I modified it a bit from what hams generally use (I used much larger tubing), but as I expected it made the antenna much more wideband. We got about 6 dBi, at <1.5 SWR across the band. Nice! Unfortunatly, the ISS was speaking packet that day, and we were expecting voice. It was certainly fun to hear a space station transmitting, but it still would have been nicer to get voice. Monday, January 14. 2008Our network has pretty lights
A while ago I posted regarding the network when I moved into my apartment. This winter break we finally got around to working on things and taking it from a cluster of gross to a pretty little network of lights. Internally, we have 3 separate IP segments, bridged by our Cisco 2500 routers. Additionally, we now have VPN tunnels to a few friend’s apartments as well. Since the Department of Defence network is not routable publically anyway, we chose to implement our main backbone on the 11.0.0.0/8 network, with other segments on 172.20.10.0/24, 10.0.0.0/8 and 192.168.0.0/16. I suppose it isn’t strictly neccesary, but at least it was worth implementing since we learned a lot about routing in the process.
Wednesday, November 14. 2007Capacitor Array
I’ve been playing with capacitors for a long time, but I just recently began getting ones large enough to make REALLY cool sparks, not just nice snaps. After the “toy” caps I played with for a month (see farther down the page), I bought 16 400v 1500 uF caps on eBay. Those made some nice sparks, and were a huge step for me. It turned out however that I had bid on two auctions and won both of them, so 5 days later 8 150v 15000 uF caps arrived. [pics missing]
Since the voltage directly affects the temperature of the spark and the over all energy stored (1/2 Cv^2), the more the better. Thus, the array is connected as 2 sets of 4 150v caps in parallel, in series. Thus the whole bank can go to 300v. (Click on any image for full size) The 400v caps are connected by thick copper wire between the terminals. You can see the balancing resistors on the 150v bank. These primarily balance the voltage on the two parallel so as not to overvoltage one set (overvoltage==boom==bad) and leave the other at a smaller charge. The resistors basically create a classic voltage divider. With all current connections, the bank holds 2430 Joules at peak. I’m planning to get 4 more 150v caps, which will let us bring the bank to its peak 400v, this increasing the max energy to 3520 Joules. That’s easily enough to cook your average garden squirrel. What do we do with these caps, you ask? Melt things. Among the favorites are aluminium foil (which instantly sublimates and creates a huge shock wave due to the instantaneous heating of the air) and softdrink cans. The latter instantly ruptures and boils the drink, which then comes out the holes at high speed… Here is a great video I put together of several soda cans being punctured (that’s Ken doing the puncturing): capfun-small.wmv (6.2MB), capfun-big.avi (153MB) Frames from the video: Before I had any “real” caps, I collected first 16 then 64 camera flash capacitors and wired them together to create some nice ize sparks. Nothing like what I have now, but nice nonetheless. The old array is 64 120 uF, 330 volt capacitors wired in paralell. This stores 424.7 joules of energy. If you grabbed the terminals with two hands, you would be pretty done. We enforce the “pocket rule” vigerously, wherein you keep one hand (usually the left) in your back pocket anytime you’re near the caps.The videos are here: Video 1, Video 2. You can see all of these files in a directory structure here. Props to Nick and his camera for the photos and video! My old cap collection with two other large but low voltage caps I scrounged from the trash at MIT. The lab and charging circuitry. You can see Ken turning on one of the power supplies to charge the caps. We used 5 such supplies at 2 times 30v each, all linked together. The cap array is at the left of the picture, in front of me. The first test: two pennies. Note the scorch mark on the table. Whacking a sprite can with a penny produces interesting holes. We melted a peice of copper to a penny. Note the edges of the penny… same one we had used on the can. A pattern left by a ball of molten copper bouncing across the table. One of the first few sparks, a frame taken from the video. A few frames from the second video: Sunday, April 8. 2007Current Happenings
Over the past few days I’ve been working on a z80 computer. It’s on breadboards, and includes 2M flash, 32k static ram, and 3 IO ports. It’s quite interesting, and is clearing up lots of my low-level computing knowledge. More on that in a few days.
Today I put much larger motors on the X and Y axis of the mill, having already put a larger motor on the Z axis. The new motors looked great and ran equally as great for about 3 minutes… The new motors pulled much more current than the previous, and I couldn’t remember the ratings on the NPN transistors I used. Turns out its less than what i need. When I get around to it I’ll make a new driver board with Mosfets rated at 50 amps, should take care of it. The supply I’m using is 5v at 50 amps, so I don’t think any single line can exceed its rating. The new mill is very slowly coming along… I can’t wait until I can make huge things though. Monday, April 2. 2007New Z Axis Motor
Tonight I finally got around to putting on a new Z-axis motor. It’s about 5x the torque of the previous, plus 4 times as many steps per revolution (so 4 times as accurate). Since there is more torque, the rapid in the Z-axis is now 11 ipm, up from about 1.5 ipm with the previous motor. Yay!
Sunday, March 25. 2007CNC Explosions and Rockets
I’ve been using the mill succesfully for a few weeks now making several PCBs. It’s really been great being able to design a board and have it in my hand within an hour. Unfortunatly, the Z-axis motor appears to have bit the dust. I came back from the other side of the shop to some bad-sounding noises, and the bit was quite embedded in the pcb… so no boards until I can take a look at that.
I made a few boards for my friends MQP (a kind of senior thesis project at WPI). His team is making a large rocket with an onboard computer and needed a wireless control. I designed and built him a transmitter and receiver from Lynx chips. They seem to work amazingly… more on that after the launch. Ryan and I just after testing the range. We look oh-so-happy: Very slow progress continues on the new 44″x22″ mill, but what little time I’m not doing school work I’m doing the rocket project. Hopefully things will clear up a bit soon. Tuesday, January 23. 2007CNC Machine Works!
Update 2012: I ended up purchasing real steppers so that I can actually get things done in a reasonable amount of time. After the controller I made melted again, I ended up purchasing an $80 chinese model that has been working well ever since. I have the mill at the shop and still use it to make parts for work. That said, this was the FIRST thing I ever machined myself, so yes, it looks horrible. It does work though.
I’ve wanted to build a CNC machine for about 2 years now (since I found out what one was). Mostly I wanted one to make robot parts and such, since I always had problems machining them by hand. This year I finally had the tools available to me to fabricate the parts neccesary to convert a standard mill to CNC. I got a wicked small Proxxon MF-70 for christmas (thanks parents!), and went about the process. My friend Ken had 3 matched unipolar stepper motors from Cannon scanners that he donated to the cause (to be fair, I agreed to make him PCBs with the mill). I first built a controller that converts steps and direction signals from the parallel port to stepper control signals. First, the direction and step signals are converted to the correct stepper high and low states for the stepper motors by 3 L297 chips from ST Micro. I really do love these drivers, and use them in pretty much any project involving a stepper. Since the logic of these chips can’t sink or source 3 amps, I use 12 TIP102 transistors (4 per motor, 1 per coil wire) to provide switching to the motors. Each motors’ common line is hooked to the +12v supply from the board, and each control line is ground-side switched by the transistor. The only other things on the board are a giant filter capacitor (stepper motors are very spiky things), a 5v regulator, a P3 fan to cool the transistors, and some pretty LEDs to a) let me see which liens are changing in order to debug things and b) look cool. (Click on any picture for a larger view) The whole unit is currently powered by a giant 12v lead acid battery. I guess I’ll eventually have to find a way to charge this thing or build a power supply, but I had this sitting around and didn’t feel like making a supply. I’ve used the mill quite a bit so far and it hasn’t noticably discharged. Update 2012: Still using that lead acid So… here it is And yes, that is my bed. Note that a CNC mill in your bed makes it not very condusive to sleeping… but some things can be sacrificed. Close up of the front: (Yes, that's a ball tool for a dremel.. don't worry I did eventually learn how to machine things properly) The X-axis controller: Y-axis: Z-axis: I got this sweet 2.5 horsepower 2.5 gallon shop vac. It fits right next to the spindle and moves up and down with it, so it sucks up all the aluminium, as well as cools the bit fairly well. It effectively keep aluminium off of my bed. This is really the best thing I’ve made so far, but I hope to get time to work on some cooler projects shortly in the future. Tuesday, November 28. 2006H4x0ring Price Chopper
Forewarning: I may or may not have participated in any of the events listed herein. This may be pure fiction, take from it what you will. That said, it was pretty awsome…
If you’ve ever been to a supermarket in a city (like Worcester), you’ll have likely noticed a locking mechanism on one of the front wheels. It’s designed to lock the cart so that it won’t roll when you try to take it off the lot, so that people don’t steal them. Around the perimeter of the parking lot, there is a wire acting as an antenna, transmitting an 8 khz square wave gated at 30 ms. This is the locking function. Using two LM555 timers, a few capacitors and resistors, and a coil of wire, a friend and I made our own transmitter. The transmitter was in my pocket with two switches: to select between lock and unlock, and to active the coil. Since the coil was down at my ancle, this waranted a wire up my pants. We headed down to the supermarket in the middle of the night, and walked past a line of carts outside: click click click click click click click. They were all locked. The transmitter worked the first time. We went inside and locked a few carts while they were moving as well, which obivously confused the people moving them. If you’ve ever been to a supermarket in a city, you’ll have likely seen a lock on one of the front wheels of the carts to prevent people from stealing them. A friend and I managed to make a transmitter so that we could the carts would lock when I walked by with the transmitter in my pants. Friday, November 24. 2006MIT Splash '06
I taught two classes at Splash this year: Moderate Electronics: Breaking Things for Fun and Profit, and AI: Genetic Algorithms and Neural Networks. The former was simply lecture, however the latter has the following files available:
GAs and NNs Presentation (PPT) xor.c - Single-file NN implementation to solve nonlinear problems (xor) nn.tar.gz - Very simple NN lib used in the class Feel free to get in touch with me with questions! Saturday, October 7. 2006Neural Nets, Genetic Algorithms, and Cellular Automata
I read a book about biological computing recently, which got me interested in neural nets, genetic algorithms, and cellular automata. Perhaps I'll write up some science about each of them soon, but for now here are a few test codes I wrote to play with this stuff.
cells.c: A quick cellular automata simulation to play with different edge conditions and such. The linked version has my setup that allows a colony to continue living: neural-backprop_g.c: Flat neural net model with back propagation. The important stuff is in main() if you want to play with it. I plan to write a proper library with this soon, so look for that. Thursday, April 27. 2006Electric Gokart
Update: Now that I actually know how to machine things, I’m going to revamp the Kart next time I’m home. Real bearings for the steering assembly, pedals and a floorboard, etc. Should be interesting…
I built this “Kart” basically because I wanted to see if I was good at building large (or larger than normal) things, and to satisfy a “project” requirment for my physics class. While most people built small electronics projects on breadboards, I built this. People were pretty surprised. Update to the update: The frame got turned into a trike for the hang glider, and the motor got imported to a scooter. Both were epic. Frame The frame was designed (in my head, since I can’t draw) to be very light, but hopefully still fairly strong. Four 1″ square aluminum stock bars run the length of the frame as 4 edges of a box. Each side of this “box” is then held the proper distance apart by perpendicular flat stock and held rigid by 2 opposite-direction diagnals of either flat stock or square stock. The cross peices that go between the frame sides in the front are 1/2″ inch steel square stock. It is absolutly key that these side sections stay the same distance apart, as they control the cambre of the wheels. The steel is held in place by threaded rod. (I would have used aluminum, but Home Depot is terrible at restocking and never had enough.) The front wheels are lame garden wheels from Home Depot (about $8 each) with built in bearings. It remains to be seen how long the bearings will last, but they haven’t fallen out yet… Steering The steering idea was conceived by Sean Manix and Joe Gage in a gravity-powered car we built long ago. I modified the design somewhat to work here. Basically, the system works as a rack and pinion system does, minus the rack and the pinion. The tierod keeps outward tension on the steering arms so that they stay the proper distance apart and the wheels stay parallel; the wire pulls the whole sytem to one side or the other to steer while at the same time keeping tension on the steering arms so they stay on the tierod. Yes, the steering arms are made of plumbing equipment. Inside those plumbing T’s, bolts come in from both square sections of frame. Roller skate bearings (that I had around and just happened to fit) go over the bolts and space the plumbing to sit in the center. I then put the T’s on the drill press and put the 1/2″ holes in them. Let me tell you, that was scary. The bit has a tendancy to catch coming out the other side, so the whole T arm unit spins around the bit fast enough to break your arm. As inaccurate as this looks, it actual is very smooth and tight. The steering feels nice while youre driving. …don’t ask, it’s a school thing somebody wrote. But yes, that is the “steering plank”. Drive Train The motor is from an electric scooter. It’s 750 Watts… in pure energy, 1 horsepower = 746 Watts, but I think here the 750w describe amount of power the motor pulls from the batteries, not the mechanical energy put out. Since the motor is likely only moderatly efficient, I’d say it’s in the half-horsepower range. My girlfriend Erica is building a kart on the same design as this one. I helped her get her motor… hers is 1200w. I think I’ll still be able to beat her once I figure out how to put some sort of transmission on this thing. The chain and rear cog are from the scooter too. The bain of my existance… the blocks holding the rear sproket are badly made and thus wobble. The axle (1″) has a keyway in it, and the sproken has a 2″ hole. Logically, we’d make spacers to simply hold it in the center, and the spacers would fit the keyway to spin it. I built two of these out of hard wood. I cut the 1″ and keyway with a coping saw (which was a hard process), screwed the whole thing together, and slapped the chain on. It looked perfect. As soon as I touched the throttle, the keyways sheared off (wood doesn’t deal with shear stress very well) and the whole unit simply spun. Despite efforts to make some sort of key, each time something would slip or shear off as I don't have access to any sort of metal shop. Thus, the steal cable goes through the hole in the sproket and get band clamped to the axle. The wood simply acts to keep the sproket in the right place, and the cable deals with transfering the torque to the axle. It’s ugly, and the chain pops off occasionally. I need to make some sort of mount from aluminum… This is basically just a large version of the electronic speed controller in a remote control car. Rather than having huge variable resistors, the “ESC” as its called simply pulses the motor very quickly, and by varying how many of these pulses are “on” and “off” we vary the speed. Ignition… because I can. The throttle from the scooter. Yes, it is taped to the side. I haven’t had a chance to fasion some sort of pedal yet. Three 7 Ah lead acid batteries power this 36v beast… they’re heavy. Final Thoughts In case you were wondering, there are no brakes. I haven’t gotten to that yet. But hey, when I get to the transmission and the throttle pedal, perhaps a brake might appear. Monday, February 13. 2006DCIR Renderer
Many people can go on and on about the “beauty of math”: everything fits, and that’s amazing. Personally, I think math is pretty handy, but not always that pretty. But hey, I suppose I proved myself wrong in this latest project.
DCIR is a program that renders pretty pictures based on a chaotic set of functions- the DeJong equations: x' = sin(ay) - cos(bx)Thus, starting with a random a,b,c,d,x, and y, we recursivly solve for an X’ and Y’ pair, then plug them back in while keeping a,b,c, and d constant. As opposed to your average function, such as f(x) = sin(x), these functions put out chaotic numbers. That is, they don’t follw any specific method, they simply hop around. But it turns out, they tend to hop into some areas more often than others. If you take a look at the images below, you’ll see what I mean. The brighter an area is, the more times an iteration “hopped” into that area. (Clicking on a picture will make it bigger, visualizations performed using Winfeild by Andrei Chernousov) You can get the source here: single machine (dcir.c), distributed (dcir_d.c) While this method is great, it’s outrageously slow. Thus, the name suggests, DCIR is going to be “distributed”, or cluster-ready. At the moment the single-cpu code works great, but the MPI version leaves something to be desired… It sucks about 80 Mb/s of bandwidth, then dies. (Hey, it LOOKS like it should work ) I would like to thank the developers of Fyre. Fyre is basically a better version of what I’ve made. We discussed originally how they had things set up, particularly how their clustering worked. Their version included some nice editing tools that DCIR doesn’t, as well as a built in visualizer, and an animation option. The reason I wrote my own was more of a personal challenge than a real reason, though it will be nice to have a version that runs on MPI, as opposed to running the Fyre rendering server on all the nodes of the cluster. For reference, here are some old images from the first version of DCIR, as well as some nice example I’ve made with Fyre (the antialiasing sure is nice): Trial 1 at different exposures: Trial 2: Fyre: Sunday, December 18. 2005Low Altitude Temperature Profile
This project is to make a mathematical model of the temperature at low altitudes, and how it changes as the sun warms the earth. I’m basing the model around the one dimensional heat equation. Here's the output from the model with cold boundaries and a hot initial center, linearly distributed along the left wall (time is to the right):
The actual writing of the model was about as exciting as coding usually is… pretty boring to hear about. Thus, I’ll describe that process and how it works when I get a little more time, but at the moment here are the stories of testing the model using the rockets. I started with 2 rockets, I currently have none. Thursday we went out and launched the first rocket without the computer in it to make sure it went where we wanted. It didn’t. In the past I’d used rockets with 4 motors and two stages, but separated, on either side of the body. As you can see here, this was not the case on the test rocket: Here the bottom two motors were taped together… this turned out to be a bad idea. Apperently the motors do not burn at the same rate exactly, so when one finished and ignited its other stage, it was cast off… while still being attached to the other. Thus the bottom motor ripped off before it had lit its upper stage, leaving the rocket underpowered. Besides that, the launch rod we used in the test wasn’t nearly strong enoough, and the rocket ended up leaving the pad at about a 45-degree angle. This wasn’t so bad until the previously-explained stage switch, in which the sudden change in acceleration made the payload and thus the CG shift forward.This shifting mass caused the rocket to further rotate, and when the (single) upper stage motor fired, the rocket was pointed horizontally along the ground, about 200 feet up. The rocket continued missle-style for the last 3 seconds of the burn, then found its way into the trees at around 250 MPH. When we found it, there were peices strewn in a 25 ft radius of the actual payload. The payload was intended to split from the body at the end of the burn. Unfourtunatly it got stuck, and the pressue inside the fusalage went instead out a different way: through the sides. So the payload came down with a section of fusalage, parachute still stuffed inside. As it went through the trees, the fins were stripped off. The wooden nose cone must have hit a tree, because I’ve never seen dents like that in such a large piece of wood… This left us with 3 lessons to learn for the “real deal”: 1) Don’t strap the bottom stages together, 2) Make sure the payload detaches smoothly, 3) use a much stiffer launch rod. We did these things, and the first (and unfourtunatly final) launch went smoothly, though we had to knock it over about 30 degrees due to high wind. Thus the final altitude was around 2500 feet. As the rocket fell, the fusalage detached from the payload, and its wherabouts are currently unknown. However, the payload was succesfully recovered and read about 3/4 miles from the launch rod, near the intended landing spot: Taking into account the issues the previous models had, I built a new rocket that was meant to be the final, perfect launch. This time rather than having such a wide and heavy body with a full BX24 motherboard in it, I soldered my own board, which included an FM transmitter for tracking. It was predicted to use half the engines (3 stages, no clusters) and go 120% as high. As I was testing the board I built, I noticed an issue. The temperature sensor was probed every half-second, and the radio was pulsed every second. When the two happened to coincide (a reading while the radio was transmitting), the value read by the computer was very far off. I did not originally make this connection, and thought my board was simply bad. I hooked a probe up to the positive of my battery, and poked the pin that was reading the temperature sensor. This should have returned a full HIGH value, or a 1024. Instead, the chip crashed, and never came back. Woops… I had forgotten that the battery (9v) was going into a 5v regulator before the computer. Thus, the highest voltage expected by the chip was 5v. All the manuals with the chip indicate that reverse polarity will instantly kill a chip. When I applied the 9v, the comparator tested it against 5v, allowed current to flow backwards, and beasted the poor device. It was 3am on launch day, and I didn’t have another chip. I decided that I might as well launch the rocket, because rockets are cool. I was rewarded with the most awesome landing yet: Epic! Sunday, November 27. 2005Genetic Algorithms
I’ve been working on a code in C to solve the Travelling Salesman Problem using Genetic Algorithms. In the past this problem has been attacked using brute force, simply trying every possible passage. Yet as the size of a dataset rises, the computation time increases exponentially with this method, such that a thousand points can take a very long time to solve.
Genetic Algorithms try a few random solutions, then keep the best and generate new ones to fill in the holes left byt the old solutions. Therefore, if a great solution is stumbled upon, it sticks around unless a better solution is found. This is left a bit up to chance. Another method is to, at each iteration, split the solution stack in thirds, sorted by those which give the best distance: keep those at the top, create the middle third by using chunks from the top third, and randomly generate the bottom. In this manner, solutions that are very far from the intended result those close to that will never have to be tried, yet the random factor protects against finding a “local minimum” as opposed to an “absolute minimum”. Saturday, November 12. 2005Logic Probe
I built an interface to the parallel port for use as a logic probe. I found this program that, using its own port driver, can sample the port at up to 1MHz, on 8 channels.
I built a pretty interface into a box with switches for the ground bus, plus I made some 2 conductor probes and some singlle conductor probes. Unfortunatly I couldn’t find any of those handy circuit clips, so I just have lame aligator clips on the probes. While looking for something to actually do with the probe, I built a simple square wave oscillator with an LM555 timer. It was almost cool… and everything is cooler when it goes faster. So I started messing with the circuit to make it go as fast as possible. I don’t have very small capacitors, but with what I had I got the thing to 675.68 kHz. I think that’s pretty good. I poked around and got it to go a little faster, but at that point the probe began aliasing because it couldn’t sample any faster, so I couldn’t test how fast it was going. I’m going to try to use this to reverse engeneer chips, ie monitor the memory bus and see what a particular chip is doing, but with only 8 channels and up to 1 mHz (usually about 800 kHz) it’s unlikely that I’ll find something simple enough to use it on. But hey, maybe I can still get linux on my toaster. Wednesday, November 9. 2005MIT Splash, Nov. 19-20. Come!
Every year the ESP program at MIT hosts classes for highschool students. Splash is held in the fall, at a time generally assumed to be thanksgiving break. I’ve attended the last 3 years, and loved it. This year however, I’m teaching a class with a friend entitled “The Calculus of Physics”. It will be awsome, and you should come. If you’re interested, see the site here.
Saturday, October 29. 2005nBody Simulations
I did a project in CS at school to simulate the movement of free bodies with gravity.
At each timestep, each body's force is evaluated with respect to every other body, vector summed, then applied. No sense writing out all the gory details here since I wrote this in a paper for class! Here's the source, and a video clip of the simulation. Note from 2012: don't judge my physics or writing by that PDF! Leaving it for posterity, but I've learned a bit since then... Tuesday, October 18. 2005The Hovercraft
A while back Mike Pontecorvo (Cornell ’09) and I built a hovercraft. It had major issues, but nonetheless could be ridden down one’s driveway.
Just recently, I decided that I needed to make a new hovercraft that had better lift and real propulsion. I started with a peice of 3′ x 4′ 1/2″ plywood. I cut a 24″ hole in the middle for my prop, and mounted the motor. The previous version had a leaf blower, but I figured that a prop would be better. This worked in the small test versions. Yet, after I had attached a good skirt and fired up the prop, it simply sat there, despite my prodding. I found that the model versions worked because the props spun very fast. Yet this version – a 24″ prop on a tractor starter motor – hardly acheived the same speed. Thus, my prop hoverfraft failed. I wasn’t quite done yet though. I had designed my skirt much more efficiently than the previous version, hoping that I could use left energy for the lift fans. When I arrived at Mike’s house with this new version, we strapped on the leaf blower and gave it a run. It floated right out of the garage! Mike hopped on, and began cruising down the driveway. He probably reached 15 mph, until I heard a large POP then “Ahh!”. Apperently the un-reinforced skirt couldn’t take the pressure, and exploded. As you can see, it ripped right up the corner. What’s was our answer to that issue, you ask? More Tape. In the end with the tape, we took the hovercraft for a run in the pouring rain down a bit of a hill. This was quite interesting, becuase rooster tails of water and vapour came out both sides, and the ground behind was dry. But asphalt is abrasive, and we soon had more skirt holes. Perhaps this didn’t turn out to be the great project had originally hoped, but nonetheless it was quite entertaining.
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jack {@} crepinc.com Recent Projects: Analog HF Transmitter Audi ECU Reverse Engineering Dual DAC QAM Modulator FPGA QAM Modulator Geiger Counter Gyro-Stabilized DSLR Platform Hybrid Rocket Engines Turbocharger Controller WWVB Rx and Tx Older Projects: Balancing Bot Capacitor Array CNC Mill DCIR Renderer Electric Gokart Hovercraft Low Alt. Temp. Model Shopping Cart Locker Trebuchet My Twitter occasionally shows projects I'm working on. My GitHub has code from a few projects on it. Quicksearch |