Part Two of Phase Dock LIVE featuring Walker Archer for a wide-ranging conversation about RC robots, electric wheelchair bases, motor controllers, and “terrorizing children” at Faires and Halloween.
Walker is an systems engineer for the Ford Motor Company. He is an avid software programmer and recent electronics hobbyist. In 2014, he organized the Thunder Ops Makers as an informal “learn by doing” group that has displayed projects for years at Detroit-area Maker Faires.
It has been edited for length, clarity and readability.
We’ve split the transcription into two parts for readability. (See Part One) Occasional time stamps are shown in square brackets [4:52] so you can watch the action and animations as they are described in the video.
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CHRIS: Show us the remote-control unit. You’ve got some pretty cool stuff with that too. You had to reflash that guy, didn’t you?
WALKER: [23:30] It’s OpenTX.
Turnigy 9X Radio
This is a Turnigy 9X which is not a very expensive radio in terms of how expensive these things can be. It’s eight channels. For robots, the more channels the better, if you want to control a lot of things. Eventually, I want to do a lot of motion with the arms. Basically, this was about $50. It might be cheaper now because it’s getting to be quite an older radio.
You can take a radio like this. Flash it with a product like OpenTX (Open Transmitter) and make it have some of the features more expensive radios have on them by downloading open-source firmware and flashing it.
It’s kind of weird because there are eight channels and something like 13 different switches on this thing. Why would you have 13 switches when you can only send them over eight channels?
The reason is because inside the firmware you can do things like change the curve of acceleration. So, for instance, I’ve got one switch here [25:09] which changes the curve for the forward/left/right movement. And if I change this, it will flip into different speeds. This is a way to program the radio to do more with the robot, rather than putting all of that control inside the BeagleBone.
CHRIS: That’s extremely helpful. I can see using that kind of control on a CNC machine. You’ve got a joystick essentially. Sometimes you want to move a little…sometimes you want to move a lot…for every bump of the joystick. I can see dialing in a safety like that if you have a younger operator, where you may want to throttle back the speed. That’s cool technology in itself, right there.
WALKER: For me, sometimes you get in a crowd and you want to throttle down. And sometimes you’re moving between positions and you need to cover more ground, so you can turn up the speed.
CHRIS: Speaking of which, we would love to see Lefty.
WALKER: Lefty is in the wings. [26:37 Lefty enters]
Lefty the “left shark”
He embodies another thing that I want to do with TARA and that is…oh, oh…what am I running into?
CHRIS: He’s pretty strong. I like that.
WALKER: Lefty is also not much more than a remote-control car with some spring-loaded motion.
CHRIS: That is surprisingly lifelike. And pretty scary. Even knowing what it is…it’s still unsettling.
WALKER: Exactly. He’s so “jointy.” People really enjoy him at the Faire.
CHRIS: Do you have a clip of him at the Faire? I remember him. And I remember people running!
WALKER: [27:46] [Plays video clip]
Lefty the shark at Maker Faire
BARBARA: We have a comment from our audience here. Steve F from California says that Walker must have an amazingly patient and tolerant wife.
WALKER: [laughing] That is the truth!
People at Maker Faire seem to be a pretty unique crowd too. They are very patient with these types of projects even when we come over and annoy them.
CHRIS: That’s true. I think people come looking for things like this, so they respond pretty well.
Do you have a picture of how you built Lefty? It’s both cool and amazing how simple it is.
WALKER: So…cosplayers, please be kind.
Lefty’s PVC “skeleton”
This was my first shot at PVC construction for the skeleton. I didn’t know until I tried this project that you can just use a heat gun on PVC pipe, bend it into shape and it will hold that shape.
It was just a matter of building this frame with all the articulation that I wanted. You can see again that it is just this spring-loaded mouth. [29:48]
The body is skinned with foam. You can get it in sheets. There happens to be a place not far from us where we can buy rolls of the stuff. It’s not very expensive. But cos-players use it to make armor and all kinds of things. I won’t get too close, because the joints that I made to put it together are terrible.
CHRIS: How long ago did you built Lefty?
WALKER: It’s just two years old.
I had another robot. He just could not be used any more. He was a semi-realistic person in a wheelchair and I swore that if anybody got offended by him I would take him apart and build something else. Lefty was the result of that.
CHRIS: Is Lefty a “she”? I can’t tell my sharks apart.
WALKER: I don’t know. It’s a play on the Super Bowl “left shark” [with Katy Perry]. Who would know?
CHRIS: The reason I asked the age is when you showed us the skeleton, it is amazingly simple. I don’t usually think of PVC as being that strong. It works really well, and looks like it is holding up really well.
WALKER: And it’s lightweight and that’s a good thing.
TARA is super heavy. One of the things that not many people know is that TARA started out life as FRED. FRED was another acronym that started with Ford, even though this is not a Ford project. One of the guys…the woodworker I mentioned before…he was a truck driver and was at a shop. And this lady said, “I’ve got this mannequin in the back. Do you want it?” He thought “Well, maybe we could use it.”
We ended up getting this. [32:27 – female mannequin hips to neck] It was very unexpected. We all said, “It’s too good not to use.” So that’s how TARA became TARA.
So maybe Lefty is a “she.”
CHRIS: I seriously love the mechanical build on Lefty. It’s cheap, accessible materials. I’m amazed on the tight bends you got in the PVC and it’s holding up. As it moves it’s very, very lifelike. It just really works.
WALKER: Yeah. I was very happy with how it came out. I really struggled because I wanted to electrify all the motion. But I couldn’t get it done in time for Maker Faire so I ended up spring-loading it. Now I’m like, “Why would I ever put a motor on this?”
Maybe the term robotics is not exactly correct for this. I use that term because First Robotics uses driven robots. There is no autonomy on them. I do want to do some autonomy. But at this point I can’t see my autonomy project being let loose in a crowd.
CHRIS: You may recall that one of our customers has a Boston Dynamics Spot. BD will tell you that “yes, it’s an autonomous robot” but they don’t let people around it. It’s not safe. It’s got some pinch points that can really do bad things. If it falls on you, that’s 75 pounds accelerating pretty hard. They have more development resources than you or I do.
WALKER: Yes. We’ll get there someday.
CHRIS: To that point, the compute resources are out there today. The Jetson Nano, boy, that’s a lot of power and you can get one for like $140. The materials are at hand.
But I think you are taking the right approach. And it is just so effective.
WALKER: Yeah. Definitely. I’d like to do some work with Machine Learning too. There are so many hot things. I really like the way technology has enabled people to do more with less equipment, less money.
CHRIS: I have to say, for someone who’s background is software oriented, you show a tremendous amount of natural talent for using things that are at hand and repurposing things and putting them together very, very effectively.
WALKER: [36:05] It’s really where I like to work—at the low end. I like doing things that are cheap. I almost regret every time I go to Lowes when I’m looking for PVC parts because somebody always comes up to me and says “What’s this for? What are you doing?” And I have to say, “I’m building a robot.” Then their eyes glaze over and they walk away.
CHRIS: We have an Ace Hardware about two miles from here where they have a very well stocked small hardware section. So, for my one-offs, I’m always over there looking for an M3 pan-head screw or whatever…and they ask “What do you want to use it for?” and I’m just “Please…just don’t ask. Don’t ask that question.”
CHRIS: Is there a particular hardware direction you want to go in?
WALKER: My initial goals were to make this something that I could share. Make it low cost, as low as possible. The beauty of wheelchairs as a base is that it can be fairly inexpensive.
Both of the wheelchair frames that I build TARA and Lefty on were $50 each. That’s amazing for a platform made out of medical grade motors. It’s really hard to kill this kind of hardware.
If you look, there’s lots of different places you can get them. On Craig’s List. Garage sales sometimes. I saw this one just last week [37:49 – screen capture of an online ad]. The bid starts at $5. This one ended up going for $110. And this one has good batteries.
That is crucial because the batteries are the most expensive part when you buy like this. This is very similar to Lefty.
CHRIS: If you do need to replace the batteries, are they pretty easy to get at?
WALKER: Yeah. They are built to be replaced. They are lead acid, so they are a little bit heavy. They used to be a little bit cheaper than they are now. For a pair of batteries for either of these robots it would be about $300. That ends up being expensive. If you can find a base that has good batteries already, it saves you a lot.
We put an Arduino into the first version—that spiderbot—that was just an Arduino.
My goal is to keep the costs low. Again, for safety, I made some tradeoffs where I’ve used a motor controller to replace the existing controller. That cost a little bit of money.
It’s gotten a little bit more expensive. I’d rather it was a project that could be published and people could do it all for $50. [39:22]
CHRIS: Well, that’s a noble goal but I still think that what you are doing, even at the price range you are talking about, it’s really accessible. Especially if a couple of people get together, both to share the load of building but also you can use it in so many different ways and places. That’s a great communal project.
BARBARA: We have a question, Walker. Are wheelchair batteries similar to batteries for UPS back-up units?
WALKER: You could use UPS batteries. Like a lead-acid gel. Typically, they come with lead-acid, like an AGM-style battery which would be more like a golf cart. Those are easy to find. The nice thing about those is that they are very durable. They’ll last for three or four years.
If you replace the batteries, you may be better or worse distance or speed of power. Which is another good reason to use a motor controller like I’m using to replace the motor controller that comes with the wheelchair. Because the motor controller that comes with it will limit the amount of current you can put through the motors.
If you want to do something like a lawn mower, or something that will plow the snow off your driveway, the original controller is not as good. But if you replace it with a Sabertooth or Basicmicro motor controller like I am using here, you’ll get a lot more power and a lot more speed.
CHRIS: If you keep the center of gravity pretty low, can you use one of these mobile wheelchairs off of the pavement, so you can go on grass for example?
WALKER: You can. Typically, the wheels that come with it are medical grade, so they don’t have the best traction. You can buy off-road-style wheels. They are black rubber as opposed to a gray or a tan. [42:12] They definitely stick a lot better. Even for going up ramps, they are better. But they don’t last as long. And they might mar floors.
That’s also a nice thing about the wheelchair base when you are using it for robotics it can go anywhere a wheelchair can go. It’s important to me. It always rains at Maker Faire. So I love to be able to go inside when it started to rain.
CHRIS: What do you think is the total weight on TARA?
WALKER: She’s probably about two hundred, maybe two hundred and ten pounds. You would not be able to lift it. I had her in the back of a car and brought her over to this building for testing in the parking lot.
A couple of friends came over and we were going to just play around like an RC car. I had a ramp and they said, “Oh, we’ll just lift her out.” They were very surprised. Two guys trying to lift just the base. It’s the batteries. There’s so much lead in them.
BARBARA: Steve (in chat) says “It’s rude to ask a gal’s weight.”
CHRIS: We hope she was sleeping.
WALKER: [laughing] I’ll reset her. She’ll never know.
CHRIS: That was my thought. Transporting her is not trivial. I can just see so many possible uses for that base aside from robotics. You can make a useful machine.
WALKER: Yes, there are projects online if you search for “wheelchair robot.” People who have just put a platform on top, then use it to carry concrete bags or whatever.
I would recommend people not do RC lawnmowers or snow-clearing. They are totally OK for that. They will do it, but it’s sooo boring. You’re going to do it once or twice and then never again. That’s a good project for autonomy.
One of the things I’d like to build is an autonomous lawn weeder.
CHRIS: You could sell that.
WALKER: I don’t think I would go up against Black and Decker. If you had the algorithm you could do it. The nice thing about broad-leaf weeds is that they have a pattern. They all have leaves that come into a central point. So, if you find a central point of radiating lines, you know where to target.
CHRIS: That is an interesting computer science problem.
Is there an online community for people who build wheelchair robots? Are there resources out there?
WALKER: I haven’t found any. There are lots of people who have published their own projects. A lot of things on YouTube that are interesting to see. But I haven’t seen a community just for wheelchair robots.
The sad thing about these wheelchairs is that they tend to get dumped into landfills and they are such great hardware. Typically, if you’re getting a wheelchair, you’re getting it through the insurance company. Insurance companies want to buy everybody a new one. Once they are done…a lot of states have laws…Michigan, where I am, has a law that you can’t reuse it because it’s a medical piece of equipment. You can’t use it for another person.
[47:16] TARA had a noble goal at first, and she’s become a clown. She’s more entertainment than anything else.
CHRIS: Well, there are so many directions you can take her. Particularly when I see her interact with children, I see a lot of possibilities.
Show us the skeleton. [47:37 video is a Halloween animation]
WALKER: This is Halloween at my house. [the skeleton dances]
CHRIS: That’s a great way to terrorize kids. Even adults.
WALKER: That’s actually Lefty’s base.
CHRIS: Well, this has been a tremendous amount of fun. Not just the technology, but the story of how you came to this point and where you can take it from here. Thank you for sharing with us.
I hope that this has inspired some of our friends at Phase Dock to take this up. I love the platform.
Thank you, Walker, not just for your time today, but also the time to prepare and set up from where you are broadcasting.
WALKER: Any time I can get these bots out and have fun with them, I do.
Lefty and TARA
CHRIS: Drive them around just a bit more!
[49:06] Lefty is amazing and fast! I think you are right. The spring-loaded parts are perfect.
Is TARA going to come say “Hi”? There she is!
What’s the deal with the rocket?
WALKER: TARA’s rocket backpack is a subwoofer.
CHRIS: When you upgraded your speakers, that’s where it went?
WALKER: I hope she’s not still mad at me.
CHRIS: Walker, thank you so much.
TARA: Would you like to dance?
Would you like to dance?
CHRIS: I would love to dance!
CHRIS: Thanks again Walker. I hope the next time we meet it is out behind the Henry Ford Museum at the Detroit Maker Faire.
Our next Phase Dock LIVE is on March 13. We’ll be talking to our good friend, Guido Bonelli, the founder and inventor of Dr. Duino. Guido and I will be talking about what it takes to launch a hardware product business. If you’ve ever thought about that, we’ll try to talk you out of it.
Until then…happy making!
End Part Two. See Part One.