OSEPP tank chassis any good?

Looking for something a little larger and more robust than the ActivityBot chassis w/ the tank treads. The goal is to mount one of Bill Henning's RoboPi boards w/ the Propeller, a Raspberry Pi3, and a small Lider unit on the body.
Fry's has this chassis on sale the next few days for $69, wondered if it was halfway decent, or if someone can point me to a better/stronger one?
https://www.osepp.com/robotic-kits/4-tank-mechanical-kit

Thanks for any thoughts.
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  • 31 Comments sorted by Date Added Votes
  • The tread kit uses the popular Tamiya rubber tracks, which are prone to stretching, and in turns, can (not necessarily will) pop off when driving over high friction surfaces. This is not as big a problem with plastic (or metal) tracks, or rubber tracks that are reinforced. I'm not clear what the treads of the Osepp kit are made from, but they look like plastic or rubberized plastic, so it has the advantage there. That said, it all depends on what you're driving over.

    An advantage of any robot that uses the Tamiya rubber is that replacements are cheap and easy.
  • The tread kit uses the popular Tamiya rubber tracks,

    Are you sure about this? Does Tamiya make more than one kind of track?

    The tracks on the OSEPP bot don't look like they're the same as the tracks on the Arm Crawler erco recently told us about.

    If you want to go for a larger treaded vehicle, you could use the treads made by Vex. Here's a thread on the topic of Vex treads.

    I like my robots to have encoders. I like the Tamiya Arm Crawler but it doesn't lend itself to easily add encoders.

    Dagu sells a Rover 5 treaded vehicle which can be purchased with included encoders. Here's a thread with some discussion about this option.

    I'm adding one the pan/tilt mechanisms described in this post to my Arm Crawler. Those pan/tilt mechanisms are pretty inexpensive but often the tilt part of the mechanism isn't needed so just a bracket to attach sensors to a servo is all one needs.



  • DrPopDrPop Posts: 61
    edited March 10 Vote Up0Vote Down
    Sorry, my question probably should be, what are some good "next step up" chassis to consider? ;)
    The tank tread kit was the first thing I've bought from Parallax that left me going hmmm... (And that's out of lots of stuff so their hit rate is very good!) I can confirm what Mr. McComb said, the pieces are from a model, as in a plastic model of a tank I would have built when I was young. My issue with it, is that it seems easy for the treads to slip past the gears, the tracks aren't very straight, (and possibly because of this?) it wants to track slightly to the left, instead of straight like it does with the ActivityBot wheels. But we keep in mind it was only $30; I didn't have big expectations. More of an experiment.

    I like the idea of tank treads, but I can see where it's easier and more practical to have a bot with wheels, especially when it comes to fine tuning movement. So I'm open to a chassis with 4 wheels too, if that's better.
    For my next bot (my first one beyond the three ActivityBots my daughter and I built), would be nice to have something a little larger than the ActivityBot so that it can pack a somewhat larger payload. I'm not thinking Arlo huge yet. Maybe something 1.5 to 2X the ActivityBot in size.
    Payload so far will be:
    Bill Hening's RoboPi w/Propeller for motor & real time sensor control
    Raspberry Pi3 for running the LIDAR and hopefully ROS or something similar
    Scanse Sweep LIDAR
    Raspberry Pi camera module
    Any other sensors needed for redundancy like Ping))), Sharp IR, etc.

    With all that in mind, would those of you with more experience recommend a tank tread, 4WD, or maybe even a 2WD base with a round top? Some of those look like they could hold a bit of weight for their size.
    Heck, maybe I should steal a page out of Erco's book and repurpose an old 4WD radio control truck. :D haha

    Thanks for any discussion on the differences or what I should look for in a more robust chassis!
  • MikeDYurMikeDYur Posts: 1,986
    edited March 10 Vote Up0Vote Down
    Heck, maybe I should steal a page out of Erco's book and repurpose an old 4WD radio control truck.  haha

    He also has another saying, just add more power.

    With that anodized aircraft grade aluminum, your not going to get much stronger vs weight. Titanium, but your not taking it into battle. There looks like some room to make some form of tread guide, a channel or even rims around the wheels, providing the track is thick enough. Or replace the track with some custom wheels. And do what I mentioned above.


    BTW: That sale price sounded very reasonable.
    800 x 533 - 38K
  • ercoerco Posts: 18,073
    edited March 10 Vote Up0Vote Down
    DrPop: erco has another saying: Man up to mecanum if you want an amazing 4WD robot! VEX wheels are awesome.

    "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
  • @Erco - that looks intense. Is that pretty hard to code? Looks sweet, wonder what the difficulty would be compared to tank treads? :D

    Anyone have comments on these two (compared to the OSEPP kit for $69 in the OP?)

    DFRobot Devastator Tank: $73 on Amazon

    Intelligence RC Tank Mount Car Truck Robot Chassis $165 (this thing looks pretty killer, not sure how real life application would be though?)
  • ercoerco Posts: 18,073
    Chicks dig mecanums:



    Some neat interplay witrh three mecanum bots:

    "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
  • Thanks, those were both cool videos. Any mecanum wheeled chassis were a bit more than I was looking to plunk down for a chassis at this stage, though. :) Not sure if you know any good ones for decent price?
    Guess I'll just have to sleep on it and figure out what I'm really after. Maybe even something like this would work: DFRobot 2WD Mobile Platform
    Just wanted a chassis that's somewhat bigger and able to move around good with the extra payload.
  • Duane DegnDuane Degn Posts: 10,000
    edited March 10 Vote Up0Vote Down
    It's tough to beat the two wheel drive setup for easy of programming.

    If you haven't seen it, make sure an watch this video sometime.



    It's long but really good.
    DrPop wrote: »
    Any mecanum wheeled chassis were a bit more than I was looking to plunk down for a chassis at this stage, though. :) Not sure if you know any good ones for decent price?

    IMO, the Vex Mecanum wheels are the best for the money (about $60 for a set of four).

    I added a set of Vex Mecanum wheels to a Rover 5 after learning about the wheels from erco. Here's a link to my Mecanum wheeled Rover 5 project on Hackaday.io.

    There's also information on my this project in this thread but the thread is not well structured.

    I believe I posted control algorithm in the last thread I linked to. If you don't find the algorithms there, I'm sure I could find them.

    The Rover 5 works well enough with the Mecanum wheels but I intend to make another version using more powerful motors. I'll likely use motors similar to the motors used in my Vex treads project.

    Vex makes a lot of cool wheels. Before using their Mecanum wheels, I used their omni wheels.

    Here's a video showing a bot with omni wheels.



    I like the three wheeled omni bot since at first glance it looks like it should should just spin in place. People always like the omni bot when I show it off but the Mecanum wheeled robot is even more popular than the omni bot.

    There are lots of practical applications for these omni wheels. They can be used in conjunction with normal wheels to reduce the skidding which occurs with deferentially powered wheels.

  • your
    erco wrote: »
    DrPop: erco has another saying: Man up to mecanum if you want an amazing 4WD robot! VEX wheels are awesome.


    That is awesome. So that is what you have been working on in your secret lab.

    Duane's Omnibot is cool too.

    Are these wheels strictly smooth floors and low pile carpet?
    I want to make a house robot about the size of a Heathkit Hero, and that would be perfect for mobility, maybe.
    How does it handle human or dog hair? Are the wheels cleanable, the more axles and wheels, the more to get dirty. And the bigger the chassis, the less I want to have to upkeep something like that.
  • GordonMcCombGordonMcComb Posts: 2,997
    edited March 10 Vote Up0Vote Down
    Duane Degn wrote: »
    The tread kit uses the popular Tamiya rubber tracks,
    Are you sure about this? Does Tamiya make more than one kind of track?

    I'm talking about the Activity Bot tread kit. The Osepp robot looks like it already has its treads, and those are not a separate kit.

  • DrPop wrote: »
    I like the idea of tank treads, but I can see where it's easier and more practical to have a bot with wheels, especially when it comes to fine tuning movement. So I'm open to a chassis with 4 wheels too, if that's better.
    ...

    Heck, maybe I should steal a page out of Erco's book and repurpose an old 4WD radio control truck. :D haha

    RC cars tend to be a little fast, and if that's what you want they're fine, but be sure you're not looking for a robot with a more traditional travel speed.

    You can get make some nice tracked robots using a toy tank. The one in the picture was especially nice, with unitized parts that permitted easy modification. I just took the top off, unclipped the wires to the IR sensor and turret motor (used for something else), and bolted on a plastic platform for my electronics and circuits. I found this at an independent toy reseller in the Los Angles wholesale district. (Many of these are also cash-and-carry so you don't need a resale licence to buy them).

    Like the Tamiya treads, though, these are all-rubber, and they lasted only a few years. The best is rubberized plastic, plastic with rubber cleats, or fabric reinforced rubber.



    1000 x 750 - 120K
  • xanaduxanadu Posts: 2,995
    edited March 10 Vote Up0Vote Down
    DrPop wrote: »
    Looking for something a little larger and more robust than the ActivityBot chassis w/ the tank treads. The goal is to mount one of Bill Henning's RoboPi boards w/ the Propeller, a Raspberry Pi3, and a small Lider unit on the body.
    Fry's has this chassis on sale the next few days for $69, wondered if it was halfway decent, or if someone can point me to a better/stronger one?
    https://www.osepp.com/robotic-kits/4-tank-mechanical-kit

    Thanks for any thoughts.

    WHAT!? Fry's of all places. Unreal. They have that chassis for $130 at my Fry's, because everything at my Fry's starts $30-$300 over retail for their fake sales at MSRP pricing. At $130, I'd buy a chop saw and some aluminum square tube!

    The chassis is great, I've seen many at maker events. There are a lot of configuration options, like erector set. It's also very pretty, if you're into that (and paying for it). You didn't mention what battery you plan to use. If you can fit everything on there, you'll love it. Considering you're getting it at a low price, you could probably sell it for the same price if it doesn't work out.

    If you want to build something simple, a couple of gear motors, two tires, and a plywood slab with a caster is tough to beat!

    Edit - I just noticed there are different versions of the track kit. I thought you were getting this for $70 - https://www.osepp.com/robotic-kits/3-triangulartank
  • ercoerco Posts: 18,073
    edited March 10 Vote Up0Vote Down
    Triangular tank is kinda funky. High CG, I can see it rolling over backwards on tall obstacles. I'd lay odds that a parallelogram or low flat triangle would be more stable and climb better.

    It's neat to see Osepp's website, never seen it before. I bought some CR servos off Ebay from some funky vendor which were Osepp, the only other time I heard of them.

    treads.jpg
    475 x 400 - 18K
    "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
  • ercoerco Posts: 18,073
    "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
  • DrPop wrote: »
    Looking for something a little larger and more robust than the ActivityBot chassis w/ the tank treads. The goal is to mount one of Bill Henning's RoboPi boards w/ the Propeller, a Raspberry Pi3, and a small Lider unit on the body.
    Fry's has this chassis on sale the next few days for $69, wondered if it was halfway decent, or if someone can point me to a better/stronger one?
    https://www.osepp.com/robotic-kits/4-tank-mechanical-kit

    Thanks for any thoughts.

    Yeah, that is a good price on the OSEPP Tank Kit and it looks very much like the Makerblock Starter Kit minus the controller board and sensors and such, but that would be replaced with a Propeller anyways.
    makeblock.com/starter-robot-kit

    I believe with the OSEPP Tank you have to provide your own controller board (A Propeller or BASIC Stamp or Bill's RoboPi would be an awesome choice). It would be interesting if an Activity Board or a Propeller BOE would drive these.

    Looking at the specs for the OSEPP Tank kit, the motors are 9V DC motors so that is something to keep in mind.

    I've tried Tamiya tank trends similar to the ones that Parallax offers but they are really only good on flat surfaces and not very durable. The Tank Tread Kit would be a great addition to a BOE-Bot or Activity Bot though and is only $34.

    The other option is to get a Radio Controlled car with trends and change out the guts with something else to make it Zigbee or Bluetooth controllable.

  • @Duane - thanks, that video is great stuff for me to consider, I'm halfway through it now. From his perspective, hard to beat the 2WD w/ castor wheel and round platform. I can see why from the geometry. I was initially thinking tank treads for the stability, but he makes a good point.

    @Gordan, erco, and the others - that makes sense, I think what I'm looking for on this next bot is the ability to have it just "'be there" without me having to mess with it much, i.e. not worrying about it getting stuck a lot, etc.

    In your opinions, which is more stable for an indoor bot: a tank tread chassis like the OSEPP, etc, or a 2WD w/caster wheel and a round chassis?
    I really appreciate all the help, this is great stuff for me to learn and I will finish the second half of that video this evening.
  • ercoerco Posts: 18,073
    I got two of these chassis for $22 (best offer) a while back. One-piece rubber treads with spring-loaded bogies. Pretty nice for $11 each, except there's not enough gear reduction (too fast at minimum voltage). PWM might work to give more scale speeds, but I'll prefer to hack in a lower gearmotor or CR servo when I get a chance.

    http://www.ebay.com/itm/Light-Damping-balance-Tank-Robot-Chassis-Platform-DIY-suspension-tank-/272563860079

    s-l1600.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
  • All kinds of ways to implement tank treads that go beyond tanks. Here's one where the tank can flip over and continue going upsidedown. Or is that rightsideup? IMO, the tank standard configuration is interesting all of about 20 minutes. So try to get a system where you can add to the links, or already has a fairly large tread loop.

    1280 x 960 - 277K
  • ercoerco Posts: 18,073
    edited March 10 Vote Up0Vote Down
    On random terrain, I give that high-CG tank a 50% chance of flopping on its side, stuck like a dying fish. :)
    "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
  • ercoerco Posts: 18,073
    edited March 10 Vote Up0Vote Down
    erco wrote: »

    "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
  • erco wrote: »
    On random terrain, I give that high-CG tank a 50% chance of flopping on its side, stuck like a dying fish. :)

    Ever heard of batteries? Slung underneath they dramatically lower the CG.

    In tests I don't think it ever tipped over. It had a very wide stance, almost a square-shaped footprint.

  • ercoerco Posts: 18,073
    Yeah, OK, sure, fine. Batteries on the bottom=lower CG. Nice, beautiful, perfect.
    Here's one where the tank can flip over and continue going upsidedown. Or is that rightsideup?

    But isn't the bottom the top now? No matter, Lipos don't weight nuthin' these days anyhow.

    "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
  • Hmmm...looks like tomorrow is last day of the sale on the OSEPP tank treads kit. Still can't figure out if treads will be better than round chassis 2WD and caster combo. I'll watch the second half of that video and see if I have a better conclusion in an hour... :)
  • DrPopDrPop Posts: 61
    edited March 11 Vote Up0Vote Down
    Just finished the full David Anderson video. Huh. He makes some good points for the 2WD round chassis. Hard to refute that for an indoor bot. I can also see why you really want encoders after watching that. Tank treads just look so cool...but maybe not "better" until you get to more outdoor obstacle type stuff.

    I can see why some of the ROS crowd re-purposes roomba / iRobot vacuum cleaners for their base. Makes a lot of sense after watching that video. Anyone here ever done a larger bot off one of those bases or considered the pros/cons of it?
  • I'm talking about the Activity Bot tread kit.

    I think I must not have read the post carefully. Thanks for clarifying.
    DrPop wrote: »
    I can see why some of the ROS crowd re-purposes roomba / iRobot vacuum cleaners for their base. Makes a lot of sense after watching that video. Anyone here ever done a larger bot off one of those bases or considered the pros/cons of it?

    Not too long after I started experimenting with robots, I purchased a Roomba. This was a time before I made videos of my robots in action so I don't have any video showing the robot. Here's the thread where I describe my attempts.

    The way the Roomba serial protocol describes turns makes navigating with a Roomba a bit trick. Turns with a Roomba are described with by diameter (or radius I don't recall which).

    I hope to revisit my Roomba project in the near future sometime but I've been saying this for five years.
    xanadu wrote: »
    If you want to build something simple, a couple of gear motors, two tires, and a plywood slab with a caster is tough to beat!

    Agreed.

    I used the advice offered by David Anderson when I built my robot "Cleaver". The Parallax aluminum wheel kit really looks nice but it's also a bit pricey. Fortunately I received the cool hardware in exchange for porting the Eddie firmware (and improving it some) for use with the Propeller Activity Board.

    Cleaver and the robot with Vex treads both use expanded PVC (ePVC). A material I learned about from Gordon McComb. It looks like the treaded vehicle Gordon recently posted uses ePVC. This is a great building material for robots.

    Speaking of Gordon, if you don't have the latest edition of Robot Builder's Bonanza, you should seriously consider purchasing it. It's full of great stuff about building robots. I wish I had purchased the book (not that it was available at the time) when I first started making robots.

    It's really not hard to put together a very basic robot. I posted some ideas of making cheap bots in this thread.

    When I went looking for cheap wheels, it turned out Vex's small wheels were a pretty good deal.

    Make sure you check out HobbyKing. They have great prices on lots of robot related gear.

    DrPop wrote: »
    I can also see why you really want encoders after watching that. Tank treads just look so cool...but maybe not "better" until you get to more outdoor obstacle type stuff.

    Yeah, I like treaded robots. I think they look cool. They do burn up batteries faster than wheeled bots. Treaded bots aren't as good at odometry as wheeled robots but I think encoders are still really useful on a treaded bot.
  • GordonMcCombGordonMcComb Posts: 2,997
    edited March 12 Vote Up0Vote Down
    erco wrote: »
    But isn't the bottom the top now? No matter, Lipos don't weight nuthin' these days anyhow.

    Actually the robot was designed to have no top or bottom, and to equalize the top weight with that on the bottom. It's CG was exactly in the middle. I don't know many people that use their small tracked robots over outdoors "rough" terrain -- this one was designed to do a Donald O'Conner and roll up a wall when it encountered one. In testing it never tilted over because of its wide stance. (Because of the wide track distance, the actual amount of tread touching the ground had to the reduced, or else it could have trouble in a turn over a high-stiction surface like a recentty waxed kitchen floor.)
  • ercoerco Posts: 18,073
    "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 just wanted to say thanks to everyone for the eye opening chat and the videos. For once I managed not to just blindly go buy something on sale! :D I will play around with the activitybot more, and then when I get the robopi board from Mr. Henning, I will hopefully have some more ideas about where to go with the project. Just undecided on which chassis style I want yet, which means to me I need to do more playing around with what I currently have and more thinking about where I want to go with it.
  • erco wrote: »

    That's awesome! That looks like an easy mod to any servo powered bot to get much better traction.

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