Cheap robot chassis that can hold oversized motors?

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:
5607459948262403260%253Faccount_id%253D1
David
PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation

Comments

  • 22 Comments sorted by Date Added Votes
  • ePVC reinforced with light metals is easy to work with and can hold a lot of weight. Thin wood works well. Sometimes searching a scrap pile is best. For instance a small computer case has enough metal to make a chassis, with some cutting and some corner braces.
  • GordonMcCombGordonMcComb Posts: 3,098
    edited July 4 Vote Up0Vote Down
    Like Xanadu sez, expanded PVC is a good material for lightweight but strong robot bodies when you want some permanency. It's been my go-to material for 20 years. It cannot be cut by a laser, though. You need to either hand-cut it, or use a mechanical CNC router.

    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.
  • Like Xanadu sez, expanded PVC is a good material for lightweight but strong robot bodies when you want some permanency. It's been my go-to material for 20 years. It cannot be cut by a laser, though. You need to either hand-cut it, or use a mechanical CNC router.

    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:
    3144572XPSL._SL500_AC_SS350_.jpg

    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?
    David
    PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation
  • ercoerco Posts: 18,319
    Most any chassis material can work. I'd worry more about making strong wheels, a lot of 3D material can warp or melt (PLA) under load. What's the gear ratio on your motors? Hopefully over 100:1, or you'll need small wheels to avoid a squirrelly, too-fast baseboard missile.

    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:

    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • GordonMcCombGordonMcComb Posts: 3,098
    edited July 4 Vote Up0Vote Down
    DavidZemon wrote: »
    Not sure where to actually find ePVC.

    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.)





  • DavidZemon
    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.

    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 :) Make good use of those motors :)


    Novel Solutions - http://www.novelsolutionsonline.com/ - Machinery Design • - • Product Development
    "Necessity is the mother of invention." - Author unknown.

  • I've always wondered about using a sturdy round trash can, like this one for $14 - https://www.walmart.com/ip/Honey-Can-Do-1.3-Gallon-Round-Step-Trash-Can-Stainless-Steel/19247024

    You could make a mini-R2D2. 2WD, with a small front and rear caster.
  • ercoerco Posts: 18,319
    edited July 5 Vote Up0Vote Down
    I'm a fan of plastic trash cans. Also laundry baskets, which have a neat wireframe appearance to them. I have hoarded a stash of various baskets & trash cans. I'm waiting for a snow day when I can get to them.

    lb2.jpg




    355 x 317 - 43K
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • I forgot all about that one, it's probably where I got the idea. Now I'm checking out everyone's trash cans for possible chassis ideas.
  • xanaduxanadu Posts: 3,086
    edited July 6 Vote Up0Vote Down
    DavidZemon wrote: »
    I don't have many cutting tools: wire cutters, a drill, dremmel, hack saw, and big ol' hand saw along the lines of this:
    3144572XPSL._SL500_AC_SS350_.jpg

    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?

    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.



  • Trash cans are good for the "skin" of the robot, but how are you going to mount all the things inside? Never mind that most stuff you put in a robot are square or rectangular (circuit boards, batteries, etc.). Have you ever tried to furnish a house that didn't have parallel walls? And finally, unless you have skinny arms, you'll be able to only use the bottom 1/3 of the can before you run out of working room (or else cut off the top, and lose structural integrity).

    Sometimes, what looks cool, isn't.
  • ercoerco Posts: 18,319
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • Trash cans are good for the "skin" of the robot, but how are you going to mount all the things inside? Never mind that most stuff you put in a robot are square or rectangular (circuit boards, batteries, etc.). Have you ever tried to furnish a house that didn't have parallel walls? And finally, unless you have skinny arms, you'll be able to only use the bottom 1/3 of the can before you run out of working room (or else cut off the top, and lose structural integrity).

    Sometimes, what looks cool, isn't.

    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...



  • A plastic trashcan doesn't add much weight, but if the "dressing" of the robot basically makes it heavier without providing any real benefit, it's probably time for a rethink.

    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.
  • ercoerco Posts: 18,319
    My take is that small/medium size robots needn't be heavy (or topheavy) any more. Small motors, LiPo batteries, 2-3 lbs max. Everyone loves R2D2, which could easily be a lightweight hollow shell (like a trash can) with most everything in the base to keep the CG low except for a head motor, some sensors & LEDs.

    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!



    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • If you're not even sure you're going to be using the motors for very long, it's hard to beat a piece of plywood or (if you prefer something waterproof) a polyethylene cutting board as a bare chassis. You can mount the motors with pipe clamps just by drilling some holes for the clamps to go through. You'll need a swivel caster to serve as the third wheel, and possibly some nuts and bolts to give it the right elevation. Fix electronics and such to the top of the board. If you like the performance, go for something more elaborate.
  • localroger wrote: »
    If you're not even sure you're going to be using the motors for very long, it's hard to beat a piece of plywood or (if you prefer something waterproof) a polyethylene cutting board as a bare chassis. You can mount the motors with pipe clamps just by drilling some holes for the clamps to go through. You'll need a swivel caster to serve as the third wheel, and possibly some nuts and bolts to give it the right elevation. Fix electronics and such to the top of the board. If you like the performance, go for something more elaborate.

    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.
    David
    PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation
  • Ah ha! I figured out what I'm going to build. It's finally time for me to have a balancing robot! Exciting! I'll have to pick up various hardware of course for the chassis, battery + motor driver, and an accelerometer. But I should have everything else.
    David
    PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation
  • ercoerco Posts: 18,319
    edited July 16 Vote Up0Vote Down
    Nice, but don't forget the gyro!

    super2(3)-1200.jpg
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • What's that for??? Just kidding :) have one already
    David
    PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation
  • ercoerco Posts: 18,319
    edited July 19 Vote Up0Vote Down
    You'll want several gyros, otherwise it will be a PITA to control your pitch and yawgurt! Watch your eyes and protect your retsinas. Right, Nikos?

    combo-giro.png
    900 x 600 - 826K
    "When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."

    - Pablo Picasso
  • I'm reading this at 10:30am local time. I am suddenly very hungry for an early lunch.
    David
    PropWare: C++ HAL (Hardware Abstraction Layer) for PropGCC; Robust build system using CMake; Integrated Simple Library, libpropeller, and libPropelleruino (Arduino port); Instructions for Eclipse and JetBrain's CLion; Example projects; Doxygen documentation
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