Cheap robot chassis that can hold oversized motors?
DavidZemon
Posts: 2,973
in Robotics
Okay, I took advantage of Chris's sale a couple weeks ago and now I have motors! Oh boy! I can make things move. This is new to me, and I'd like to explore. But, I have no idea if I'm going to enjoy playing with these for more than a couple weeks, so I'm looking for some kind of robot chassis that can hold these giant motors for as little money as possible. I'm looking for something that can old at least the two large motors, and I'm trying to figure out what to do with the 6 steppers that I haven't come up with anything easy and cheap yet.
I don't personally have a 3D printer, but i have access to one through a public maker-friendly place, so I might just print some cheap wheels.
Here's what I bought:
I don't personally have a 3D printer, but i have access to one through a public maker-friendly place, so I might just print some cheap wheels.
Here's what I bought:
Comments
Wood is always good. I'd advise so-called aircraft-grade plywood, available at Michael's and most any good craft store.
On those motors: stepper motors do not make good robot locomotion motors, which I think you already know. Steppers are best for constant torque applications. The gear motors in your picture seem suitable, though their size suggests a fairly large chassis (10+ inches?) to support their weight. A 1/4" PVC or plywood material would be suitable, though you may also want to buttress the mount to make it stronger.
I don't have many cutting tools: wire cutters, a drill, dremmel, hack saw, and big ol' hand saw along the lines of this:
I have a soldering iron too... but probably shouldn't count that in my cutting tools :P
Planks of ePVC look good though. A hacksaw blade would probably make reasonably quick work of that, and I could make holes for mounting with relative ease it looks like. I suppose angle brackets and the like could all be found Menards, right? Not sure where to actually find ePVC. None of the home depot's around me have this, but at least they can send it for free if I'm patient. 1/8" would probably be the right thickness right?
IMHO every roboticist needs to build a nice big slow chassis for dead reckoning experiments. You have built-in encoders so you're mostly there! Here's mine:
You could always ask a shrubber (Roger the Shrubber: "Yes, shrubberies are my trade. I am a shrubber. My name is Roger the Shrubber. I arrange, design, and sell shrubberies.")
But probably easier to track some down at a shop that makes signs, especially if you're not a Monty Python fan. Many will sell their scrap for cheap, some even give it away if you ask them nicely (and don't say "ni!").
Actually, the stuff you pointed to at Menards fits the bill if you get the 1/4" thickness, though I detest working with the black material*. The (incorrect) "foam" moniker comes from how the gasses that expand the plastic create a kind of foam-like cross-section when it's cut. The plastic is not at all foamy or soft, though it is easier to drill and cut than wood.
(The *lighter* the color, the easier it is to work with, mostly because of heat when using motorized tools. The darker plastic melts faster from friction -- melt = BAD. See if you can find white or light yellow. You can always paint the stuff after cutting with any solvent-based paint. The color becomes permanent because of how the solvent of the paint actually melds into the plastic. The same thing happens with plastic models.)
Ya' know, I have always been designing stuff for as long as I can remember.... but my life really changed when I first combined stepper motors with the Basic Stamp. It can lead down an endless road of new adventures and creations. Design something and build it
You could make a mini-R2D2. 2WD, with a small front and rear caster.
I've found that lack of tools will only slow me down, not halt anything. For angle brackets I used angled aluminum bar and cut it into pieces. Lots of cutting, but worth it in the end. Here's the thread.
Also these brackets are cheap.
Sometimes, what looks cool, isn't.
https://books.google.com/books?id=FB-yg7s9bF0C&pg=PA159&lpg=PA159&dq=garcan+robot+jerry+rebman&source=bl&ots=6PTpSJdEjo&sig=yzwaVmtEjr3iL7jLjQygdCRUStg&hl=en&sa=X&ved=0ahUKEwjarJ-I1fPUAhUQx2MKHXW6CWAQ6AEIKDAA#v=onepage&q=garcan robot jerry rebman&f=false
I was thinking round plates cut out of wood with standoffs to stack the plates, maybe a hole in the middle of the plates to pass wires through. The bottom plate could have slots for wheels. I don't know about mounting arms to it, that would be tough. Another downside is that you'd want the batteries in the bottom, which means leaving them in there with some kind of charging jack. Everything seems easy after converting that PW chassis to AWD lol...
You want to be able to take the garbage can shell off, which means attaching the bulk of the robot's parts to some internal structure, the way that most have it anyway. What then, does the shell provide, that you couldn't do with lighter and easier-to-use materials? Does the solid shell raise the center of gravity and make the robot less stable? You need a way to take the shell off without a lot of disassembly, or else you'll seldom work on the thing. A neglected robot is a sad robot.
Mind you, a conversation piece robot has its own raison d'etre. I once made a small robot out of a L'eggs pantyhose egg. Great conversation starter, mediocre robot.
There was mostly empty space inside Heathkit's HERO 1 and Jr robots. They were great for their day, although crude by today's standards. Even a blue Scribbler 1 is a lot more robot than the HEROs delivered (except HERO 2000). But height commands attention. Just gutting a Scribbler 1, 2 or 3 and installing those parts in a foot-tall plastic trashcan (like the one below) would be a neat project IMO.
Hmmm. Somebody should ask Mr. Roboto about how to do that!
That's a great point. Clamps + nuts & bolts through holes in the board will work great! And that at least is hardware I'm familiar with. And two clamps per motor with a bit of wadded up paper under the gear train to keep it level with the board should work really nicely. I'm liking this...
Okay... now to figure out power. I can drive in small circles while tethered to a wall wart for a while. When I'm ready for battery power I should probably just suck it up and get a quality lithium pack + charger like the ones Parallax sell for the Elev-8.