PREMIUM – Ask Adam: Airplane on a Conveyor Belt

Every week, Adam takes a question from the Tested Premium Member community in the comments section below or on social media (tagged #AskAdamSavage) and answers here. This week, Adam talks about one of his favorite myths to bust, and why the results were so unbelievable for viewers.

Comments (21)

21 thoughts on “PREMIUM – Ask Adam: Airplane on a Conveyor Belt

  1. Adam, have you ever received critique on a build or project that knocked you for a loop? How did you recover?

    – Kevin


  2. That’s a good description of the aeroplane on a conveyor belt. Basically the ground is irrelevant in a plane’s motion, even when it’s taxiing.

  3. Thank you so much! I can’t tell you how happy this made me.

    Plane on a Conveyor Belt is absolutely one of my favourites as well. Instead of trying to explain basic physics to the innumerate, I could now point to the episode and say, “There! It’s solved. This is no longer a ‘thought exercise’, but an observed fact about planes.”

    Of course, the usual suspects immediately started yesbutting the result: “All right, yes, but the conveyor belt imparts a tiny little bit of drag on the plane, as it’s uselessly spinning those wheels around, so if you just move the belt fast enough…” To which I could only facepalm and think, “Did you bother to run the numbers, even in the vague ballpark of what would be required for that to work? You’d need a belt running at an appreciable fraction of light speed, so it would have to be made of some kind of indestructible, yet still flexible ‘unobtanium’, with a friction so high that it still retains traction with the wheels even at those speeds, yet so little friction that it doesn’t heat-weld itself to its own drive mechanism. You’d need the power output of a handy nuclear plant to drive it — and at that point the wheels of the plane have exploded into rubber confetti from the strain of spinning so fast, and the landing gear has been ripped off the plane because it wasn’t built to withstand an opposing force, equal to that of a plane taking off.” *sigh*

    As for the effect of the bacteriological testing episodes, I can completely understand that. (Beware the Horrors of the Kitchen Sponge!!!) I, too, wouldn’t want to blithely grab a handle that was used by previous, possibly less conscientious, users of the bathroom. I learned a lot from Kari’s techniques during the “simulated runny nose” dinner experiment in the Flu Fiction episode. That one was particularly helpful, because it not only showed how one can protect oneself from infection, but also how to act responsibly and not infect others. Thank you for suffering through that one on our behalf!

    And thank you again for answering my question! It absolutely made my week.

  4. Hi Adam!

    Do you have any tips for we, as makers, stop perfectionism from getting in the way of our making and hampering our progress?


    – Matthew Morgan.

  5. Once a person exits a bathroom, that person does not stop using door handles and doorknobs, nor does that person stop touching everything else. Should we wear gloves 24 hours a day in that case? There are poop germs everywhere, yet after 200,000 years, humans are still here. I think we might just be OK.

  6. Ravengael As someone who also stopped using my hands to open bathroom doors after seeing those Mythbusters episodes, I’d like to note that there is a significant difference between the inside knob in a public bathroom and other doors.

    The germs in question thrive in a wet environment, and because the bathroom is heavily trafficked wet zone, which also happens to be where these bacterias “come out”, they can stay alive and well much longer there.

    Normal door knobs are much more likely to be fine, because they are dry, and only a small minority of people who touch them recently also came into close contact with fecal coliform bacteria. For the bathroom door half the people who use it have washed their hands and not dried themselves properly, and the remainder haven’t washed their hands since using the bathroom.

    I know which one I’ll take my chances with. :p

  7. it depends on the landing gear. we take for granted that with the plane the landing gear is already facing the direction of movement for both the plane itself and the runway so the landing gear can spin freely and not appreciably effect the plane. with a helicopter if it has wheels usually the back two are fixed angled forward while the front one swivels. it might also just have skids. so the problem with either set up is that if it were on a giant turntable neither regular wheeled landing gear or skids would be able to “freewheel” against the moving turn table and thus would cause the fuselage of the helicopter to turn along with it. if the fuselage turns as fast as the blades then the net movement of the blades is zero . of course we’re assuming the turn table is even able to spin as fast as helicopter blades spin but in reality it would be hard to not end up chucking the entire helicopter off the turn table as a result (especially with the tail rotor going full speed in an attempt to counteract the rotation). so realistically you’d only be able to spin the copter slow enough not to throw it off the turn table in which case as long as the remaining speed of the blades is enough to achieve lift you might be able to take off. you’d just be lifting a rapidly spinning helicopter which might make for nearly impossible control. now if all 3 wheels in the landing gear were the swivel type, or the wheels were able to be set perpendicular to the spin of the turn table, then you’d take off no problem as the tail rotor would keep the fuselage steady in one place while the main rotor operated as normal.

    so… realistically? no. the turn table would spin the fuselage which would either counteract the main rotor and overpower the tail rotor or just throw the entire aircraft off the turn table in the attempt. in order for it to be able to take off you need to be able to isolate the turntable from the fuselage like a plane is with the runway. if you could do that via swiveling wheeled landing gear then you’d absolutely take off no problem.

  8. #AskAdamSavage is there any advice you have for a introductory item or things to build to start a out as a new maker. Such as certain mediums and how to obtain the items to do so.

  9. Re: doorknobs, I heard there was a movement to get hospitals to switch away from standard stainless steel knobs over to silver or copper as they’re more antimicrobial. Maybe bathroom doorknobs (which are more-used in a more microbial-friendly environment) need to be made of copper or silver in general.

  10. Airplane on a Conveyor Belt was the most frustrating episode EVER, and a good example of the importance of asking the right question correctly. If you’ve got a good education in science you learned in physics class to conduct proper thought experiments, employing things like massless pulleys and frictionless planes. In this case if you consider a frictionless axle on the airplane (and disregard the effect of air drag on the belt,) you could run the conveyor up to ten thousand miles and hour and the airplane would just sit in one place, until you run up the engine and have a normal takeoff using the thrust from the propeller. So the right question would be, is the real friction in the airplanes landing gear axle enough to overcome the thrust generated by the airplanes propeller. That’s already been proven because; Airplanes can take off! The whole question is silly when you frame the problem correctly. Stay in school. Pay attention in science class!

  11. I met the buster duo back stage in Seattle years ago, I asked, “What project have you been involved in, that has not been documented yet, that you are most proud of?” The answer was “” I then asked if they would ever tackle a helicopter on a turntable, and got a look that I still am unsure the meaning of, and a “Thank you.” Fast forward here we are on tested, talking about it. I imagine if Adam reads this, the same look. Listening to him talk about the right question, adding your list of landing gear possibilities above, I understand why airplanes. 🙂 Unrelated: If failing is always an option, best to be in the position to define failure.

  12. Isn’t the “Being happy vs. being right” theory just a con to promote acceptance of being wrong?

  13. What are some of your methods for keeping your Workshop clean and Keeping the Dust build up to a minimum?

  14. @BClark1004 i think it would have a harder time taking off even with landing gear that allowed the turn table to move isolated from the fuselage. with a normal helicopter you have the tail rotor keeping the fuselage in place but with a Chinook there’s no tail rotor. i don’t feel like you could effectively use the counter rotational force of one of the rotors to keep the fuselage in one place so it would end up spinning with the turn table and not be able to take off.

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