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| Newton's third law problem. |
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| Nominal Animal:
Electrodacus, I have proven your assertion wrong, and proven a vehicle constructed as I described, works. I constructed a simple vehicle with a thread spool and a worm gear on a vertical axis, and a pinion gear and driving wheels on a horizontal axis. I also created a LeoCAD model of the vehicle, so that anyone with Windows, Linux, or Mac, can examine the vehicle in 3D, and build one or a similar one with whatever parts they may have handy. Just save the attached trike.txt as trike.ldr, and it will open in LeoCAD. It only uses parts that are available in LeoCAD by default, I believe. When the spool turns clockwise, the single wheel is the rear wheel. When the spool turns counterclockwise, the single wheel is the front wheel. Using strong, non-springy polyester thread (that I normally use for sewing buttons back on), configured either way, pulling the thread off from the spool makes the vehicle move; even when you are pulling the thread in the opposite direction. Specifically, if the two wheels point left and one wheel right, and the thread comes off the spool counterclockwise and through a hole in the black holder, pulling the thread right makes the vehicle travel left. Conversely, if the thread comes off the spool clockwise and through a hole in the gray holder, pulling the thread left makes the vehicle travel right. In other words, this works –– so that pulling the thread makes the vehicle travel in the other direction –– in both directions and configurations; all you need to do is swap the direction the spool turns when you pull the thread off it. Because this is a worm gear drive, there is absolutely no energy storage. When you stop pulling the thread, the vehicle stops, because the wheels cannot turn the spool (as a pinion cannot drive a worm, only the worm can drive the pinion). The spool axis has minimal inertia, too; when you stop pulling the thread, the spool does not unwind on its own. I can take video of it tomorrow if you insist –– I need to make some kind of a holder for my phone and get better lighting, because my hand-held video was horrible ––, but I'd prefer you yourself build and test a similar vehicle. It does not need to be exact same, just make the gearing ratio small enough so that there is sufficient stiction for the wheels to drive the vehicle forward. Note that I had to use a worm gear because I didn't have pinions of different sizes in this set, and because the driving wheels are so much larger than the spool, I'd have needed a large reduction anyway to get the surface speed ratio below 1:1. I seem to have misplaced my Lego tubs, but I did have one unopened set, Lego Technic 9395 "Pick-up tow truck", that I got as a present from a friend. This limited the types of gears I had available. As the set has no chain elements, the best I could do was a thread spool and a single worm-pinion reduction. I would have used spur gear reduction gearbox if I had suitable gears; alas, this set does not have sufficient gears to do that. But it does have the worm and pinion. To turn this into the original treadmill model I described, I would need a Lego chain, two sprockets for it, and replace the spool with a sprocket at the bottom of the trike. Two idlers for the chain on the trike, so that the chain makes an Ω-shaped loop around the sprocket, would help ensure the chain does not slip. If you don't want to run the chain vertically, you need to replace the worm and pinion with spur gear reduction instead. Remember, the reduction has to get *surface speed ratio* below 1:1 for stable running to be possible, but that does *not* limit the ratio of how fast the vehicle travels compared to the thread or treadmill speed (see \$v_c\$ and \$v_t\$ in my earlier post, and how they relate via \$\lambda\$, the surface speed ratio.) The smaller the ratio, the easier it is to get movement without losing traction. Remember, *any* movement of the driving wheels moves the vehicle away from the direction you're pulling the thread or the treadmill surface travels, so something like a 1:10 reduction just makes sure you're not tripping on insufficient traction/stiction and such issues. I do not think anyone should trust my word for it if they truly doubt this is possible (and nothing out of the ordinary, just a trivial mechanism). This is why I show the CAD model of the exact vehicle I built and verified works as I described –– and Electrodacus claims is impossible ––: so that you can examine it and build it or your own version of it, and prove it yourself. There is absolutely no trickery here. |
| IanB:
Nominal Animal, you have fallen into the trap laid by Electrodacus. He is not interested in truth, he is only interested in persuading other people to spend (waste) their time making things or constructing things in an attempt to prove him wrong. If you spend your time on such fruitless endeavors, you are simply encouraging him. He is a sociopath, whose only interest is in manipulating others. He feels a sense of power and control when he gets other people to do what he wants. |
| electrodacus:
--- Quote from: IanB on November 22, 2022, 01:28:20 am ---Nominal Animal, you have fallen into the trap laid by Electrodacus. He is not interested in truth, he is only interested in persuading other people to spend (waste) their time making things or constructing things in an attempt to prove him wrong. If you spend your time on such fruitless endeavors, you are simply encouraging him. He is a sociopath, whose only interest is in manipulating others. He feels a sense of power and control when he gets other people to do what he wants. --- End quote --- You have not answered me to the last few comments. I asked if your model can show a vehicle with a 1:1 gear ratio moving 2 squares to the left while the treadmill is not moving at all. If you agree with that let me know how a non moving treadmill can power the vehicle ? If you disagree let me know how ? |
| Nominal Animal:
Trap or not, we have physical proof now. Besides, the subject is something that others may wonder about. It is one thing to argue with math and diagrams and even animations, but a completely different thing to show a model one can build and examine, and build the proof with their own hands. I hate the idea of others stubling on this thread, and not having any way to determine the truth. I want to provide a way they can verify for themselves. Plus, I like to show that when I provide some math, I can also provide physical examples to back it up. You don't need to trust me, but ignore me at your own peril. As of right now, it seems that the cheapest way to obtain sufficient parts would be one 42133 set, and one or two 42132 sets. The first one has the worm and structural parts, the second has drivable wheels (but alas only one of each size) and even a chain (but alas a short one), so two sets of the second are needed for a robust trike model similar to mine, but using a chain. The sets cost 10€ apiece here right now, so 30€ total. I won't be spending more effort on this, unless someone wants me to build the treadmill/chain model with build instructions using one 42133 and two 42132 sets (LeoCAD can be used to make Lego build instructions), and is willing to cover the price of the three sets for me, though. It might be an interesting hands-on device and experiment on why intuition might fail here (thinking that it would be impossible for the vehicle to travel in the opposite direction of the treadmill surface or chain or pulled thread), so might have some educational value. |
| IanB:
--- Quote from: Nominal Animal on November 22, 2022, 02:11:39 am ---It is one thing to argue with math and diagrams and even animations, but a completely different thing to show a model one can build and examine, and build the proof with their own hands. --- End quote --- Someone built a model before, but Electrodacus simply rejected it and said it couldn't possibly work without including energy storage in the explanation. |
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