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Rubber tracks for Robots

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  • Rubber tracks for Robots

    Okay guys---We talked about this last week. Domestic sourcing. I have been engaged by a company to design a lightweight service robot that weighs about 400 pounds. I need to find a source for steel reinforced rubber tracks. The tracks look kinda/sorta like very small army tank tracks only they are only about 1 1/4" to 1 1/2" wide, are molded in one piece with no mechanical splice, and have ribs on the outside to enable them to climb stairs (in a house). They also have to have some feature that will let them engage with cast in "ribs" on the outer diameter of a 4" to 6" outer diameter wheel to provide a positive "drive engagement". The robot has to travel around inside buildings without damaging floors, so the tracks have to be rubber, or something very similar to rubber. The robot will have two of these tracks, similar again to an army tank configuration and the tracks will be about 3/16" to 1/4" thick. I just spent all afternoon Googling "rubber tracks for stair climbing robots" and every other combination of words to that effect. Alibaba which sells straight out of mainland China seems to have them (and about 100 very similar things) on their website---7 days delivery. Nobody in North America has them. I can find North American sources for Bobcat tracks, snowmobile tracks, and all terrain vehicle tracks, but NOBODY in North America is selling what I need in the size range I require. Here's your chance to be patriotic!! Find me somebody in USA or Canada who can sell me such things.---Please!!!---Brian
    Last edited by brian Rupnow; 03-06-2015, 09:26 PM.
    Brian Rupnow

  • #2
    Timing belts like some 3-d printers use?


    • #3
      How many tracks are we talking about, and what price range do they need to fit into? If you only need a pair that's a problem, if we are talking a bunch that would help.



      • #4
        Look up double-sided timing belts, from Gates and other suppliers.


        • #5
          I can't wait !!!!!!!! I love the robot thing, and having you build one is going to be
          great ! Your one of those guys Brian, that anything you can imagine in your mind,
          you can have it sitting on the table in short order.
          John Titor, when are you.


          • #6
            As in many things I design/build, I need two tracks and 2 drive wheels, and two smooth idler wheels for the prototype. However, there is so much work and design time goes into the prototype that I want whatever track and wheel system I use on the prototype to be identical to what gets used on the production run to prevent having to design and source things twice. My customers get real ugly when, after building a successful prototype I tell them that it will take an additional 50 hours to redesign part of the system because the components used on the prototypes are "one ofs" and are not commercially available for the production run.--And rightly so!! Prototypes are expensive things to make, and the design can easily run into many thousands of dollars, so I always try to design using components readily available on the world market. As far as how many will get built---tens, hundreds, thousands? I have no idea. I don't sell nor market the things I design. I design them, source purchased components, design components which must be fabricated, and do the project management with machine shops, fabricators, and sub trades, i.e. pneumatica, hydraulics, etcetera. How many actually get built depends on how large the market is, how good a sales team my customer has, and whether or not ne can build the things I design economically enough to sell them competitively and make a profit. I will look at the double sided timing belts but I doubt they will be long enough. the distance between the front and rear wheel sets is about 44".---Brian
            Brian Rupnow


            • #7
              I don't know where they get them but Foster-Miller here in the US builds a similar robot system for the military and might be able to help you source some tracks.
              My company, supplies the radio control links for their robots.
              I cut it off twice and it's still too short!


              • #8
                I'm going to go out on a limb here and suggest that what you want is not available. Not as a standard part, at least. Not yet.

                There ARE some similar robots, and ATV-type wheelchairs that do climb stairs. But so far I believe they are small-production, and almost certainly the tracks are specially-made for the application.

                If you think about it, stair-climbing is pretty much what those folks sell, so they are not making products to sell to competitors. They may well have patents (at least design patents) or the like on their in-house developed IP, which would be the form of cleat etc to do the job.

                So it looks like you yourself have to do the design, which I normally see done by a 3 to 5 person team. Sounds like fun, but maybe not the type you want. We have turned down jobs where the downside was too large. Including anything to do with medical or amusement parks, etc.

                There is no such standard thing as "stairs". There are a very large number of TYPES of stairs, though, and there are BOCA etc standards, I believe, on the rise and run. If you limit the function to that shape of stair, your problem is easier. But that might not fly for a general purpose item, a lot of stair types have been put up in the last century or two.

                Now, if the robot does not need to carry anything valuable, like a person, or expensive stuff, and it is unlikely to tumble back down and crush anyone/anything, then you may be OK. At 180 kilos or so all-up for the robot, that's probably not applicable though.

                Keep eye on ball.
                Hashim Khan


                • #9
                  J Tiers You are right, to an extent. Most companies who build a proprietary robot will have a track manufacturer design and build a track to their specific needs. and that track will ONLY be sold to that specific company. That method works, and works very well, but is horribly expensive unless amortized over the sale of 200 units with treads being built and sold. However--thank goodness there is a second way. For people just entering the field and trying to build a prototype on a relatively low budget, you find a tread company that manufactures a tread and wheel combination very close to what you need, then modify your design to accommodate that tread and wheel combination. IF you can do this very early in the design process, you can cut out a tremendous cost factor in designing and building your own proprietary treads. Of course, the trick is to find a track supplier willing to work with you. The Chinese generally have no compunctions about doing this. It just ultimately means more money for them, as they don't have to build new molds and new processes from scratch. They don't really care who buys their product, as long as they sell more and make more money on it.
                  Brian Rupnow


                  • #10
                    Hi Brian
                    Don't know if they meet your needs, but they seem to be in the ballpark for length:
                    Last edited by RichR; 03-07-2015, 02:51 PM.
                    Location: Long Island, N.Y.


                    • #11
                      Most rubber tracks are used to spread the weight of the prime mover over a wide area (like on turf or snow) which is the exact opposite of what you're trying to accomplish. No one is going to have ready-to-go 1 1/2" wide tracks. Ths smallest ones I sell (for Toro Dingo loaders) are about 4.5 inches wide. They're about $600 US each.

                      You could build a steel linked track with rubber grousers (pads) for less that that.


                      • #12
                        Just throwing a suggestion or two- a urethane rubber compound would probably be the better thing to use to avoid marking flooring and treads, etc. While not cheap, it can be cast in a cold molding process. This means it's conceivable that you could make up a mold and cast pieces that could be assembled into a belt without having to use expensive machinery. Then the problem becomes how to make them such that they assemble into a loop.

                        Second idea that came into mind is to use chain for the inner 'drive' links, then add the outer urethane castings onto the chain for the outer links. Some chain has hollow links- some is made with cleats attached to the sides of each link, or each second link, something like that. Perhaps the outer 'drive dogs', or stair-climber links, could be attached to those in a serial fashion.

                        I realize this is making your own, as opposed to being able to buy a suitable product from the start- and it sounds like you want to avoid that. Perhaps there's a halfway point, where you could buy the 'drive dogs' or whatever you'd call them- already made- which you then assemble into a loop of desired length.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


                        • #13
                          Originally posted by brian Rupnow View Post
                          For people just entering the field and trying to build a prototype on a relatively low budget, you find a tread company that manufactures a tread and wheel combination very close to what you need, then modify your design to accommodate that tread and wheel combination. IF you can do this very early in the design process, you can cut out a tremendous cost factor in designing and building your own proprietary treads.
                          And, that's just the issue.

                          If you want "treads", you have a lot of choices. If you want "stair climbing" treads. with lugs/grousers/tread suitable for some given inclination and style of stairs, or worse, for a generalized "stair-shaped" incline, that may be *just a tad* more difficult.

                          I would not say it is impossible. And, if you DO end up doing a custom, you can get a mold made very cheaply in china. You might get by far cheaper than you think.

                          There is also the "segmental" molding process, as used for vacuum cleaner hoses and corrugated drain.... You have a section of mold made, and this is used to mold a "section. Then it is advanced LESS THAN the length of the segment, and another section molded, which will weld into the prior section. In principle, one could do this in such a way that the "front end" of the item is then fed into the rear of the mold, and the last shot molds it out to length and welds it together into an endless section.

                          Obviously not with pipe or tubing, but at least possible with a solid shape.

                          That could well be your best option, if a thermoplastic material is acceptable. There are rubbers that should work with this method, I believe. At least it was so represented when we were looking at a part that would be made that way.

                          A very nice part of this process, if it can weld-in the front to rear, is that it can make any length. Almost any number of the smallest repeating feature can in principle be molded up by changing the overlap.
                          Last edited by J Tiers; 03-07-2015, 03:11 PM.

                          Keep eye on ball.
                          Hashim Khan


                          • #14
                            Your client needs to understand that if they design something for prototype unless it is something already available off the shelf, there is going to time and cost involved period. If they don't like to hear that they need to learn to adapt or come up with more money for the investment.

                            'Hard' rubber tracks like you are asking will be a specialized process (youtube how tires are made for an idea). The mold must be made, shrinkage needs to be accounted for, the durometer of the rubber needs to be right and the curing process needs to be right.

                            They will choke on the cost of making a mold to make tracks and have them steel belted to boot. Even an aluminum mold you have a significant amount of money in aluminum then the machining and actual process in making them.
                            The idea of pouring urethanes into a mold is very reasonable except for the time making the mold (plaster/fiberglass/wood etc). You can get some very good and harder urethanes and make some good parts but expectations are always in play.

                            It is harsh but I think your request is unreasonable to think that this stuff is out there already, especially in the exact width, thickness, cog size, and length you need.
                            Needless to say I wouldn't touch this unless all money in up front and with an exact understanding of the limitations of the build. People are shocked by the cost of onesy twosy molds because there is no cost break. Designing/drafting in CAD is the easy part...manufacturing the part where it comes to haunt you. And yes I work on rubber, CAD/CAM, and molding. I may come off pompous but it is reality.


                            • #15
                              Last edited by MrSleepy; 03-07-2015, 06:58 PM.