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About Davidz90

  • Birthday 01/09/1990

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  1. Davidz90

    My mechanical clocks

    Ken Kuo has many excellent animations of various escapements: https://www.youtube.com/channel/UC2h07cGBpJs8bF3OkgtJICg Other than that, there are many other animations. As for books etc, unfortunately I don't know any good references. The Arnfield, while conceptually a bit more advanced than other escapements, is actually pretty easy to pull off. The critical part is making sure that unlocking the escape wheel takes less energy than the wheel delivers by lifting the gravity arm back up. Basically, the escapement tuning is like this: gravity arm fails to lift? -> it has to be lighter or more torque is needed gravity arm jumps erratically? -> less torque or heavier arm is needed escape wheel fails to unlock? -> needs heavier gravity arm or less unlocking friction pendulum works for a while then stops? -> needs heavier gravity arm or less unlocking friction I have done recently an instruction for my Arnfield escapement:
  2. Davidz90

    My mechanical clocks

    Another design in microwatt power range. Combines very long period pendulum with "spring" made of carbon fiber strip.
  3. One thing comes to mind: Everything worth doing is worth overdoing Interesting idea and great build!
  4. Thanks! Limb strength is a major problem here. Ideally, they should be a single piece - a connection in the middle of a limb is just asking for trouble. Keep in mind that while the string has 5 kg pull, this is after the compound system - the limbs hold some 15-20 kg. I'm thinking about something like Ravin R15 crossbow - I'm arleady pretty close to it in overall dimensions, and the limbs are short.
  5. Congratulations @MegaRoi, @Didumos69 and @Anto! That was a very fun contest
  6. New version, with double power. This is what "giving up on safety margins" means
  7. 24: 10 25: 6 15: 4 9: 3 3: 2 10: 1 Good luck everyone!
  8. Great design! Yes, the COG is in proper place. That panel is pretty much blanketed by front anyways and contributes very little to lift. Moving wing back is a good idea - You could unload the front a bit. Moreover, the current front design has pretty significant area and might generate lift on its own.
  9. @agrof, great pictures and explanation. You are right, both configurations are viable. I'm no aerodynamics expert either, but my worry is that the stabilizer, as pictured, would not act as a smooth wing. Instead, it would just shove the air in one direction, like this (sorry for butchering Your sketch :D): img by David_Z1, on Flickr Anyways, lifting tail is a more tricky configuration - when the tail stalls, nose goes up and tail stalls even more. With stabilizer pushing downwards, stall causes the nose to drop - aircraft dives, accelerates and restores proper airflow over the tail.
  10. COG is still far too aft - it should be slightly behind the leading edge. I'd suggest adding a beam at the front, and then adding weight at the end of it - this way You can shift cog without adding much weight. Moreover, the tail has to generate a force pushing it down - it might need some inclination. Maybe use a thin string to connect tip of vertical stabilizer and front of an airplane? That way You can bend the tail up a little and make it more rigid at the same time. Lastly, since dihedral is not an option with this construction, moving COG downwards (like in a hang glider) is a good idea too.
  11. Maybe something like this would do? Russian Yak-15. The tube would be at the front. YAK-15 by Stewart Callan, on Flickr It would be interesting to see what glide ratio can be achieved. My bet is 1-2, so that angle of descent would be something like 40 degrees.
  12. The plane has far too much mass aft. The planes centre of gravity should lie about at the leading edge of the wing and the horizontal stabilizer should be inclined a bit. Like in the image below, the stability is all about balancing forces: Balans1 by David_Z1, on Flickr
  13. 2kg on a pulley, so 1kg per single support point. Here it is:
  14. Lots of good advice sir! This contest was a lot of fun for me, and Your clock inspired me to try studless construction in the contest entry. If I may add something, the Arnfield escapement is definitely worth a try. It is very power efficient - on my last big clock, 48h on 144 cm string (actually 72 cm with pulley). And most importantly, the pendulum is 100% separated from escapement wheel torque.
  15. Davidz90

    [TC13] The Click Counter

    Incredible! Looks a bit like a steam engine, especially the escapement part . Soo many clever solutions here. I have never seen planetary windup mechanism like that and the constant torque converter is a very interesting design. In clockmaking, such mechanism is commonly called "remontoire". I was actually trying to incorporate one into my entry, with no success. Great job!