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  • Pods...to print or not to print

    Once you start down this making your own stuff malarkey you can be forgiven for believing you don't need manufactured parts any more...or do you?
    I like my chassis, the one I did for the studebaker with a slot it sidewinder its a ruddy marvel.
    The flexy pod chassis I made were a great learning exercise and saved a few quid on pods but no matter what I do I'm never satisfied with the durability of my 3D pods. So I thought let's draw up a separate SW pod myself with drop in spherical bearings and adjusters, the idea works but sadly there are very thin sections of plastic that just snap when forcing the motor in or out.
    I'm coming round to the idea that buying a slot it pod is a headache saver. The strength and accuracy of the motor and rear axle relationship is crucial to a good handling car, some things are best bought or made in brass.
    I like brass, it's easy to work with and lasts forever, maybe a hybrid is needed.

  • #2
    Think about why the piece snapped, and mitigate for that. Sometimes changing the orientation of the print will fix it... and sometimes it will just cause the print to break more easily elsewhere.
    While it's nice to have a thing be all one piece, there's nothing wrong with it being more than one piece. If you don't like to CA glue parts together, you can design screw holes, pockets, and printed threads or captured nuts or even heat set inserts and such, in order to assemble parts that were printed in their own, optimum printing orientation. There's also chemicals for every material type that will do a proper material bond, such as acetone with ABS, or Dichloromethane for PLA.
    The point is, you can't always design something for printing the same way it's designed for injection molding, or vice versa, but that doesn't mean it can't be done.

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    • #3
      I'm a firm believer in superglue, I use loads of it.

      The size of some parts we print often means making do with less detail whilst keeping the integrity of the part itself. The other answer of course is a smaller nozzle which is OK with some filaments but absolutely no chance with others.

      Comment


      • #4
        True, not to mention different materials and temperatures, annealing, etc.
        I probably wouldn't bother trying to print a pod to go into a slot.it chassis. A chassis that fits slot.it (or whatever) pods, probably OK, but if I'm going to print the pod, I'll probably design it along with the chassis so that they work well together, and are designed with 3D printing in mind as the method of manufacture.

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        • #5
          The part causing headaches are the motor fixing screws and the distinct lack of material between the 3 holes. I may try a minimalist approach that requires gluing the motor in once gearmesh is set, much like a metal chassis.

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          • #6
            So what material are you printing your motor pods in? If it is PLA no wonder you are suffering breakages. Not to be a broken record here, but I'd strongly suggest you try printing your motor pods in PETG.

            But why would you want to print a SlotIt motor pod in the first place? Are said pods that expensive? At a guess I'd say the SlotIt pods are injection molded nylon, and there are dang few materials better than that for mechanical properties. Injection molded parts will always be stronger than printed. Packing a mold to 10,000 psi or so does tend to obviate internal adhesion issues.

            You started out with the right idea. The whole point of printed parts is to design and create parts that nobody else is making. And especially parts that cannot be made by any other process.

            You've seen the sidewinder motor pods I have created. They are designed in two pieces (plus optional shims) and assembled with 0-80 threaded screws. I print undersize holes for those screws. One half of the pod gets its holes drilled to size and tapped, the other half has its clearance holes drilled to size. The assembly is shimmed -- with printed shims having drilled clearance holes -- to set the armature-to-axle centerline spacing.

            These parts were originally designed and printed in PLA. i had a few breakages trying to snap in the motor. Once I discovered PETG I changed their material and I've had no more breakages.

            I have assembled and raced cars with these motor pods. They work fine and I've had no structural failures despite some hard bumps on the track.

            I'll edit this post to add images of my motor pods. Not convenient at the moment.

            Ed Bianchi
            Last edited by HO RacePro; 10-14-2020, 06:21 AM.

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            • #7
              I've not tried PLA on this printer, CF Petg, Nylon and recently bog standard Petg.
              Petg is definitely better than Pla, Nylon is definitely the layer adhesion king.
              What you say is exactly my thinking also, do I print my own just for the sake of it when they're cheap enough and don't break.
              Maybe I'm enjoying the challenge, maybe I need to stop wasting time and get chassis drawn up for cars waiting patiently.

              Comment


              • #8
                Originally posted by Kevan View Post
                The part causing headaches are the motor fixing screws and the distinct lack of material between the 3 holes. I may try a minimalist approach that requires gluing the motor in once gearmesh is set, much like a metal chassis.
                That kind of thing would have to be printed flat on the plate. You could then use a printed L bracket to glue it to the chassis.

                Whatever the solution, I'm sure you can find something to accomplish what you want with the printer.

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                • #9
                  Originally posted by Kevan View Post
                  What you say is exactly my thinking also, do I print my own just for the sake of it when they're cheap enough and don't break.
                  What kind of sacrilegious talk is that?!? You can turn your "maker" card in right now, mister! You, too, Ed! :P

                  But seriously, I love printing things I could get at the store. Sometimes my print is better than the mass produced one. ;-)

                  I'm on a Facebook group called "F%@K That, I'll just print it!" that's all about printing things, even when the thing you're printing is readily available in mass produced form. Usually when that thing is terribly overpriced, but often enough when it's cheaper to buy than print. Because we CAN!

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                  • #10
                    Well, this is a subject I know absolutely nothing about. So of course, I feel compelled to comment ...

                    That there motor pod should provide not just a 'fit' accommodation for the location of the motor, gears, and axles, but it's the most essential part of the build, in some respects. That's why we see companies such as Slot.it manufacturing different pods from different materials, in order to affect stiffness. Some manufacturers (particularly the heavy duty 'long can' / boxer types) actually do use brass or other exotic metals sometimes.

                    If that essential drive-train - from securing the motor solidly, and in the optimum orientation for the balance of the car, through the precise configuration of the gear mesh, to the precise location of the rear axle per whatever bushings are used - seems important, it's because this is fundamental to building a good race car.

                    Pods aren't that much of an expense, compared to many replacement parts of a slot car. Unique, they are not. So, why on earth is anybody motivated to 'manufacture' them via a 3D process?
                    Last edited by Wet Coast Racer; 10-14-2020, 08:56 PM.

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                    • #11
                      Clearly, you do not have a 3D printer. :P

                      Comment


                      • #12
                        Wet Coast Racer,

                        My motivation for printing motor pods is to provide features that no commercially-available pods have. The sidewinder pods I have been designing allow me to adjust the axle-to-armature centerline spacing using printed shims, so I can install different gearsets and adjust their meshes to within thousandths of an inch. I've never seen anything like that for sale anywhere.

                        Another feature I have added is a way to continuously adjust the wheel-well clearance without shims. That will compensate for variations in tire diameter.

                        And then there is the fact that my motor pods don't fit into a chassis. They mount to the body itself -- a monocoque design. The front axle and guide get their own pod, also mounted to the body. So who needs a chassis?

                        Oh, and that front pod pivots in the 'roll' direction, so all four wheels stay in contact with the track, and the guide stays square versus the slot.

                        Once I heard, second-hand, someone had commented I didn't just think outside the box -- I didn't know there was a box! That made me smile.

                        Ed Bianchi

                        Comment


                        • #13
                          There's something satisfying about drawing something from a blank page, transferring the file to a printer and waiting for the finished product to take off and inspect.
                          I'm warming to the idea of modifying bodyshell files next using Blender, it's not something I know anything about at the moment but there's help out there.

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                          • #14
                            Thanks, guys.

                            I gotta admit, it's been amazing to see how this whole 3D discussion has taken off on SCI.

                            Comment


                            • #15
                              Originally posted by MrFlippant View Post
                              Think about why the piece snapped, and mitigate for that. Sometimes changing the orientation of the print will fix it... and sometimes it will just cause the print to break more easily elsewhere.
                              While it's nice to have a thing be all one piece, there's nothing wrong with it being more than one piece. If you don't like to CA glue parts together, you can design screw holes, pockets, and printed threads or captured nuts or even heat set inserts and such, in order to assemble parts that were printed in their own, optimum printing orientation. There's also chemicals for every material type that will do a proper material bond, such as acetone with ABS, or Dichloromethane for PLA.
                              The point is, you can't always design something for printing the same way it's designed for injection molding, or vice versa, but that doesn't mean it can't be done.
                              This is what I've been working on tonight, a two piece pod, motor glued in, axle height adjustment... this could easily accept an FF050 motor too

                              Comment

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