Tuesday, May 31, 2011
Kitsap Mini Maker Faire
Attoparsec will be a last minute addition to the Kitsap Mini Maker Faire on June 5 in Poulsbo, WA. We will be displaying various projects, giving introduction tutorials on the use of jeweler's saws, and hopefully be selling the new EL wire interface circuit kits. Be there and be square!
Wednesday, May 4, 2011
April Tools Results
Last Saturday we took part in the April Tools Wooden Boat Challenge. Basically, we were given an unknown set of materials, 1 hour to plan and 3 hours in which to build a boat. Hand tools only (except for driving screws). It was a lot of fun!
This is what we had to work with. 1 and 1/8 sheets of plywood. 8 1x2s. 1 2x2. A roll of duct tape. 3 tubes of caulk. Some wood screws. And a meter of rope.
We got a nice curve for the hull by draping a string and tracing it out. This let us precisely determine the length of the curve ahead of time, very important when working with limited materials!
Then the sawing started!
Predictably (if you know any of the team) we brought far too many tools. Better too many than too few!
The side walls were screwed to cleats screwed to the bottom plate. A single thwart helped brace them during construction. We had a lot of problems with the cleats splitting until we started pre-drilling the holes using the hand brace. Of course, its chuck didn't go small enough for the tiny drill we were using. Luckily, we had a pin-vise on hand! And that's exactly why we brought far too many tools with us.
Getting the ends bent into place took a lot of effort. The final joints were okay, but we made heavy use of the caulk to get it actually water-tight.
Lots and lots of caulking.
It was only at this point that I could test if I would actually fit. I was chosen as the primary pilot, as I have by far the most small boat experience thanks to my 1500 km trip down the Mackenzie in 2007. Not that I've done any since then...
At the last minute, we decided it needed a dragon's head prow. At the last second, we decided it needed an eye hole bored out using an antique ship auger we had with us. We finished exactly as the tools-down buzzer sounded.
Our mighty craft, the Knorr! It wasn't the most elegant build, but we were all pretty happy with it. We accomplished exactly what we had planned 3 hours earlier.
As it turns out, though, what we planned had some serious problems. Namely, it had absolutely no primary stability, as the following video plainly demonstrates.
So, we didn't get very far in the race. But oh well! It was fun, we got to spend the day outdoors on a very lovely day on the very lovely Sunshine Coast. If we do it again next year, I expect we'll make a much better showing.
This is what we had to work with. 1 and 1/8 sheets of plywood. 8 1x2s. 1 2x2. A roll of duct tape. 3 tubes of caulk. Some wood screws. And a meter of rope.
We got a nice curve for the hull by draping a string and tracing it out. This let us precisely determine the length of the curve ahead of time, very important when working with limited materials!
Then the sawing started!
Predictably (if you know any of the team) we brought far too many tools. Better too many than too few!
The side walls were screwed to cleats screwed to the bottom plate. A single thwart helped brace them during construction. We had a lot of problems with the cleats splitting until we started pre-drilling the holes using the hand brace. Of course, its chuck didn't go small enough for the tiny drill we were using. Luckily, we had a pin-vise on hand! And that's exactly why we brought far too many tools with us.
Getting the ends bent into place took a lot of effort. The final joints were okay, but we made heavy use of the caulk to get it actually water-tight.
Lots and lots of caulking.
It was only at this point that I could test if I would actually fit. I was chosen as the primary pilot, as I have by far the most small boat experience thanks to my 1500 km trip down the Mackenzie in 2007. Not that I've done any since then...
At the last minute, we decided it needed a dragon's head prow. At the last second, we decided it needed an eye hole bored out using an antique ship auger we had with us. We finished exactly as the tools-down buzzer sounded.
Our mighty craft, the Knorr! It wasn't the most elegant build, but we were all pretty happy with it. We accomplished exactly what we had planned 3 hours earlier.
As it turns out, though, what we planned had some serious problems. Namely, it had absolutely no primary stability, as the following video plainly demonstrates.
So, we didn't get very far in the race. But oh well! It was fun, we got to spend the day outdoors on a very lovely day on the very lovely Sunshine Coast. If we do it again next year, I expect we'll make a much better showing.
Tuesday, April 12, 2011
April Tools
As I've posted elsewhere, I'll be taking part in this years April Tools competition on April 30 in Madeira Park, BC. Basically, we're given a pile of unknown materials and 3 hours to build a small boat, which we then race around the harbo(u)r.
I've wanted to do this for years, and I'm getting quite excited about it. My team is registered under the very appropriate name The Archimedes Screwballs, should you be in the area (ha!) and want to stop by to cheer. As you almost certainly will not be in the area, I'll be posting pictures afterwards. And very possibly a video of one of us (me, I'm thinking) getting quite wet.
I've wanted to do this for years, and I'm getting quite excited about it. My team is registered under the very appropriate name The Archimedes Screwballs, should you be in the area (ha!) and want to stop by to cheer. As you almost certainly will not be in the area, I'll be posting pictures afterwards. And very possibly a video of one of us (me, I'm thinking) getting quite wet.
Wednesday, April 6, 2011
Lightbox
(This was actually a December project, but it was only recently permanently mounted, so you're hearing about it now.)
So, Lauren was living in a basement room. No windows. This made getting up in the morning quite difficult, as it was always pitch black in there. As I have a predilection for elaborate technological solutions, I suggested we should make a lightbox disguised as a window, lit with daylight bulbs. I've always enjoyed how psychologically powerful the trick of daylight-colored light coming through fake windows is. So that's what we did.
We found a nice antique stained glass window at an architectural salvage store. Originally I planned on adding drapes, but that was before finding such a gorgeous window to work with. It's mounted on a simple wooden box I made, with hinges at the top and a latch at the bottom.
The electronics are hidden inside. I probably should have gone with 4 banks of tubes, but even the really cheap units were a bit pricey. The box was finished with some ebony stain, which nicely matched the weathered, mildewed window frame.
I'm quite happy with the result, for such a simple build. It's hooked up to a power strip with a built-in programmable timer, so it turns on 15 minutes before the alarm goes off.
One caveat: It was recently discovered that napping in the evening with the lightbox on can really, really mess up your Circadian rhythms. You have been warned.
So, Lauren was living in a basement room. No windows. This made getting up in the morning quite difficult, as it was always pitch black in there. As I have a predilection for elaborate technological solutions, I suggested we should make a lightbox disguised as a window, lit with daylight bulbs. I've always enjoyed how psychologically powerful the trick of daylight-colored light coming through fake windows is. So that's what we did.
We found a nice antique stained glass window at an architectural salvage store. Originally I planned on adding drapes, but that was before finding such a gorgeous window to work with. It's mounted on a simple wooden box I made, with hinges at the top and a latch at the bottom.
The electronics are hidden inside. I probably should have gone with 4 banks of tubes, but even the really cheap units were a bit pricey. The box was finished with some ebony stain, which nicely matched the weathered, mildewed window frame.
I'm quite happy with the result, for such a simple build. It's hooked up to a power strip with a built-in programmable timer, so it turns on 15 minutes before the alarm goes off.
One caveat: It was recently discovered that napping in the evening with the lightbox on can really, really mess up your Circadian rhythms. You have been warned.
Tuesday, April 5, 2011
Full-scale hydraulics
As I've mentioned elsewhere, I'm giving up on the hexapod as a project for this year. It's just too complicated and expensive to pull off in that time. Instead I'm going to spend the summer working on the Kalamazoo, hopefully getting it into much better shape for the Burn this year.
That doesn't mean I've stopped working on the hexapod, however, just that I've changed the schedule. Prototyping of the hip joint continues with decent, if slow progress. Most recently I've switched out the teeny tiny hydraulic test platform for something a little bit beefier.
It was sold for powering dump truck bed lifts, with basically no documentation. I'm not sure exactly how many amps it wants, but it's a lot. It works well enough, though. Should be capable of about 1.3 gallons per minute, which is conveniently close to 1/6 the number I've calculated as being required for the entire system. So if a single leg can move at speed being run off this pump, that will be very promising.
The hip joint is really the key to the entire project, as far as I can see. The mechanical design is the trickiest, as unlike the other two leg joints the forces are all parallel to the pivot, making it want to bind. And this is where the top speed of the final device is determined. During a normal stride, the other two joints will only move through maybe 10 degrees, while the horizontal hip joint will travel through upwards of 90. It needs to be a low friction and fast moving.
When dealing with hydraulics, speed is a matter of flow rates. A pump can only move so much hydraulic fluid at pressure per unit time, and that determines how fast a given cylinder will move. The volume a cylinder needs to actuate is simply the area of the bore times the length of travel. The faster the pump can provide that volume, the faster the cylinder moves. Of course, the smaller the bore is, the less force it will apply. And the shorter the travel, the worse the lever moment will be for pivoting something. No free lunch, here or anywhere. Luckily, however, the force being applied by even a very narrow cylinder is much more than I should be needing!
So for this joint I wanted a narrow cylinder, with as short a travel as possible. After poking around online for awhile, I finally found one that was 1" bore by 4" travel. Tiny, but it should still be big enough to do the job. I don't really know, of course, but that's what empirical testing is for! And last night I started on that, hooking up the new pump to the old control valve and electronics and the new cylinder, mounting it for the first time on the prototype hip joint, and giving it a spin. And I managed to do it without either losing a finger or spraying gallons of hydraulic fluid around the garage!
In short, a very real success. That's a full-scale joint running with full-scale hydraulics at a reasonable speed. (Would result in a hexapod walking speed of 3+ mph, depending on the leg length. Though without the other two cylinders running, it's not a very fair test.) I need to get it running using the Arduino PID controller next, to get a sense of how bad the momentum effects are going to be. Assuming that looks good, it's on to prototyping the rest of the leg. Which probably means switching to cartridge valves, which means making a manifold, all kinds of fun stuff. But there are several smaller projects clamoring for my attention this month, so most of that will have to wait.
That doesn't mean I've stopped working on the hexapod, however, just that I've changed the schedule. Prototyping of the hip joint continues with decent, if slow progress. Most recently I've switched out the teeny tiny hydraulic test platform for something a little bit beefier.
It was sold for powering dump truck bed lifts, with basically no documentation. I'm not sure exactly how many amps it wants, but it's a lot. It works well enough, though. Should be capable of about 1.3 gallons per minute, which is conveniently close to 1/6 the number I've calculated as being required for the entire system. So if a single leg can move at speed being run off this pump, that will be very promising.
The hip joint is really the key to the entire project, as far as I can see. The mechanical design is the trickiest, as unlike the other two leg joints the forces are all parallel to the pivot, making it want to bind. And this is where the top speed of the final device is determined. During a normal stride, the other two joints will only move through maybe 10 degrees, while the horizontal hip joint will travel through upwards of 90. It needs to be a low friction and fast moving.
When dealing with hydraulics, speed is a matter of flow rates. A pump can only move so much hydraulic fluid at pressure per unit time, and that determines how fast a given cylinder will move. The volume a cylinder needs to actuate is simply the area of the bore times the length of travel. The faster the pump can provide that volume, the faster the cylinder moves. Of course, the smaller the bore is, the less force it will apply. And the shorter the travel, the worse the lever moment will be for pivoting something. No free lunch, here or anywhere. Luckily, however, the force being applied by even a very narrow cylinder is much more than I should be needing!
So for this joint I wanted a narrow cylinder, with as short a travel as possible. After poking around online for awhile, I finally found one that was 1" bore by 4" travel. Tiny, but it should still be big enough to do the job. I don't really know, of course, but that's what empirical testing is for! And last night I started on that, hooking up the new pump to the old control valve and electronics and the new cylinder, mounting it for the first time on the prototype hip joint, and giving it a spin. And I managed to do it without either losing a finger or spraying gallons of hydraulic fluid around the garage!
In short, a very real success. That's a full-scale joint running with full-scale hydraulics at a reasonable speed. (Would result in a hexapod walking speed of 3+ mph, depending on the leg length. Though without the other two cylinders running, it's not a very fair test.) I need to get it running using the Arduino PID controller next, to get a sense of how bad the momentum effects are going to be. Assuming that looks good, it's on to prototyping the rest of the leg. Which probably means switching to cartridge valves, which means making a manifold, all kinds of fun stuff. But there are several smaller projects clamoring for my attention this month, so most of that will have to wait.
Monday, March 14, 2011
Horizontal Hip Joint Prototype
I've been (slowly) working on the prototype design for the horizontal hip joint. This is by far the trickiest joint of each leg, as the ~500 pounds it needs to support will be torquing the bearing instead of being a clean radial load. It's also the limiting factor in the overall speed of the hexapod: in a normal walking gait, the other two joints will only move very slightly, while the horizontal hip joint will swing through 90 degrees of travel. The smoother the action is here, the faster the top speed is likely to be.
I decided to use car wheel hub bearing assemblies, as they are cheap and robust. After playing with one under very moderate load, I decided that I just didn't like the torque it was being put under. So I went with two, stacked one top of the other. Now all that torque is converted into a much nicer radial load within each bearing. You can get an idea of the arrangement in this rough sketch. (Except I grew the bearing support frames upside down, oh well.)
This is the completed prototype. (The large shelf is only there for testing purposes.) The action is very smooth, and while a bit tedious, making 6 of these would not be a problem. I'm quite happy with it. Unless some major problems are discovered in later testing, I think this design will work nicely. Making just one of them is giving me a greater appreciation of just how big this thing is going to be.
Here's a closeup of one of the bearing assemblies. They're simply bolted to plates which are welded to the support frames. Everything is under compression.
And here it is with about 175 pounds of static load on it, which it handled quite nicely. Once I get a better test stand for it, I'm hoping to do some tests with it loaded closer to the design goal of 500 pounds. I'm running out of large chunks of steel to hang off of it, though.
I decided to use car wheel hub bearing assemblies, as they are cheap and robust. After playing with one under very moderate load, I decided that I just didn't like the torque it was being put under. So I went with two, stacked one top of the other. Now all that torque is converted into a much nicer radial load within each bearing. You can get an idea of the arrangement in this rough sketch. (Except I grew the bearing support frames upside down, oh well.)
This is the completed prototype. (The large shelf is only there for testing purposes.) The action is very smooth, and while a bit tedious, making 6 of these would not be a problem. I'm quite happy with it. Unless some major problems are discovered in later testing, I think this design will work nicely. Making just one of them is giving me a greater appreciation of just how big this thing is going to be.
Here's a closeup of one of the bearing assemblies. They're simply bolted to plates which are welded to the support frames. Everything is under compression.
And here it is with about 175 pounds of static load on it, which it handled quite nicely. Once I get a better test stand for it, I'm hoping to do some tests with it loaded closer to the design goal of 500 pounds. I'm running out of large chunks of steel to hang off of it, though.
Saturday, February 19, 2011
Hydraulics
As part of the investigation in the feasibility of the hexapod project, I've spent the last month playing with a small hydraulics test system. The final system will need 18 actuators, all moving simultaneously and quickly, controlled fairly precisely. Is this possible? (Or, more the point, affordable on my budget?) It's an open question.
The first step was the hook up a small electric motor to a small cylinder and control if from an Arduino. This was done with a solenoid valve interfaced through a basic solenoid driver circuit.
Control of the valve is only one side of the equation, however. To move the joint to a specific position, you need to know where it is, so you know when to stop moving it! This requires an encoder. Out of curiosity I tried using a flex sensor -- I don't recommend it. They're super noisy. Much more promising was the AS5040 chip, which is a non-contact magnetic system. A friend had a test board which I could borrow. It worked much, much, much better. With the addition of a PID library, it was all more or less working.
So, I'm sure I can control the hydraulics as needed. At a much higher cost than I would like -- the valves are going to be at least $100 each! The next step is to rigorously spec out the entire system using real components. Specifically, the horizontal hip joint needs to be able to cycle fast enough, using a real cylinder, driven by a hydraulic pump supplying a realistic volume. The big question is determining just how much force will be needed there. I'll be prototyping the joint and performing empirical measurements with full loading over the next few weeks. And once I have that answer, I'll have a pretty solid guess of just how much this is all going to cost -- and thus if I can do it this year or if it will have to stretch into 2012.
The first step was the hook up a small electric motor to a small cylinder and control if from an Arduino. This was done with a solenoid valve interfaced through a basic solenoid driver circuit.
Control of the valve is only one side of the equation, however. To move the joint to a specific position, you need to know where it is, so you know when to stop moving it! This requires an encoder. Out of curiosity I tried using a flex sensor -- I don't recommend it. They're super noisy. Much more promising was the AS5040 chip, which is a non-contact magnetic system. A friend had a test board which I could borrow. It worked much, much, much better. With the addition of a PID library, it was all more or less working.
So, I'm sure I can control the hydraulics as needed. At a much higher cost than I would like -- the valves are going to be at least $100 each! The next step is to rigorously spec out the entire system using real components. Specifically, the horizontal hip joint needs to be able to cycle fast enough, using a real cylinder, driven by a hydraulic pump supplying a realistic volume. The big question is determining just how much force will be needed there. I'll be prototyping the joint and performing empirical measurements with full loading over the next few weeks. And once I have that answer, I'll have a pretty solid guess of just how much this is all going to cost -- and thus if I can do it this year or if it will have to stretch into 2012.
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