Make your trebuchet throw farther

12 марта 2015

Для корректной работы сайта в вашем браузере должны быть включены файлы Сookie

Мы ценим ваше мнение. Оставьте отзыв о том, как проходит обучение.

Наведите на предложение, чтобы увидеть перевод

Рекомендуемые слова

Make your trebuchet throw farther

0:03Hello and welcome to this video on trebuchet physics, design, and tuning. Keep watching and I'll not only teach you trebuchet physics, I'll show you how to make an efficient trebuchet and improve the distance of your throws.
0:14So, how should we view a trebuchet? Many people see it as an uneven teeter totter, with a fat guy on the short end and a baby on the other. With a ratio of roughly one to four, the larger guy will somehow launch the other high in the air. You see this in plenty of movies, but a trebuchet operating purely as a lever won't throw very far.
0:25I'll show you several tricks or energy transfer mechanisms that will allow you to throw farther. It's probably best to start with a review of conservation of energy. Let's say that I have a stationary counterweight on a frictionless ramp. This counterweight is height h above the bottom of the ramp and has mass m. It will have energy, mgh. At the bottom, it will have kinetic energy, 1/2mv2.. By conservation of energy, E=mgh=1/2mv2.
1:01We can add a second object to represent the projectile and accelerate it from velocity a of 0 to v2. We do this by somehow transferring energy from the falling weight to the projectile. This adds the projectile's Kinetic energy to our equation Now, we have to divide the energy between the counterweight and the projectile. In other words, the projectile is fastest if the weight is stationary. This creates a very simple rule to judge success.
1:33If your arm and counterweight are moving fast at the point of release, you are doing it wrong. I am going to show several energy transfer mechanisms. Together, these will transfer most of the energy from the counterweight to the projectile. I'll start with the lever, which is an important feature of all trebuchets. Levers provide a fixed movement ratio between the projectile end of the arm and the CW end of the arm. However, as I said earlier, a 1:4 ratio arm isn't going to throw anything very far on its own. To do better, you'll want a sling. Contrary to popular belief, slings are not just a convenient release system. They are an impressive energy transfer mechanism. Don't believe me? Watch this slow motion clip.
2:31Here, the sling unfurls, stalling the arm and the counterweight. Most of the energy is in the projectile, making this a good release point. The multiple rotations trebuchet is an extreme example that relies almost entirely on sling stalls. As shown in this simulation, the trebuchet undergoes several sling stall points. Since sling stall position is a major factor in trebuchet efficiency, here are some sling stall tuning tips:
3:03If you want an earlier sling stall, shorten the sling. If you want a later sling stall, make the sling longer. In conclusion, sling length determines sling stall point. Before discussing the ideal sling stall point, we have to address an issue on the other end... A counterweight fixed directly to the arm is an energy hog.
3:23It's big, heavy andusually retains a lot of energy at the bottom... Medieval engineers had a very elegant solution. They would hang the counterweight from the arm... Here's another slow motion clip... The beauty of this mechanism can be seen when I plot the motion of the arm and counterweight.
3:44The counterweight falls almost straight down, stops, makes a sharp turn and gets pulled parallel to the ground. This creates a counterweight-arm stall point. Here, the hanging counterweight mechanism transfers almost all of the energy from the Counterweight to the arm. Syncing the sling stall point with this counterweight stall point, results in a very efficient throw. Note how still everything is at the end.
4:06Be warned, past our counterweight stall point, the counterweight actually pulls against the arm. While it's ok to release slightly after the stall point, don't release too long after. With this in mind, knowing how far to hang your counterweight is important. Here's how to find the stall point for a given hanging counterweight length. Hold the counterweight at the launch position...
4:28Then pull it straight down. When you can't pull down any further without moving side to side, you are at the stall point. This is an OK length... For reference, here is one that is way too short. You're not going to get a good release off of this. Of course, the hanging CW trebuchet sacrifices counterweight fall distance for this efficiency. This means that it isn't viable for height constrained competitions. Here are several modern designs that you should look into. The floating arm trebuchet uses rails to constrain the counterweight vertically and to allow the arm pivot to move horizontally.
5:03This has a counterweight stall when the arm is vertical, but doesn't trade off fall distance. I highly recommend this design. Multiple rotations trebuchets are actually surprisingly efficient if you can get the sling stall points right and have a certain novelty factor... They are very unforgiving. Here is an interesting twist on hanging counterweight trebuchets...
5:28From what I've seen, the nicest ones have wheels or a floating arm. There are countless other variations, but I won't discuss them. If this video was useful, please like, subscribe or check out some of my others.

teeter totter

«Teeter totter» — это детские качели (качели-весы) в виде доски с сидениями на обоих концах.

  • Children like teeter totter very much. — Детям очень нравятся качели-весы.


Американский и британский английский имеют некоторую разницу в словарном составе. Так, например, слово «movie» (фильм) — это американский вариант, в Британии говорят «film».

  •  She loved reading about movie stars. — Она любила читать о кинозвездах.

at the bottom

Основной смысл выражение «at the bottom» очень прост: «внизу», «на низу» чего-либо. Но в зависимости от контекста, перевод немного меняется.
at the bottom of a page — внизу страницы,
at the bottom of the stairs — на нижней площадке лестницы,
at the bottom of the pocket — в глубине кармана,
at the bottom of a table — в конце стола,
to be at the bottom of the class — быть последним учеником в классе.

  • Only the page marked September 29 had space at the bottom. — И только на странице, относящейся к 29 сентября, оставалось внизу свободное пространство.

falling weight

«Falling weight» можно перевести как «падающий груз». Слово «falling» имеет форму причастия настоящего времени (Participle I) и в данном случае играет роль определения к существительному (какой?), классический пример: «smiling girl» (улыбающаяся девочка).

  • He reeled back, arms flopping, already falling. — Он отшатнулся и замахал руками, уже падая.


Слово «judge» можно перевести не только как «судить», «выносить приговор», но и как «оценивать», «определять».

  • The age of a good wine can be judged from its colour, smell, and taste. — Возраст хорошего вина можно определить по его цвету, запаху и вкусу.


Слово «provide» очень полезное, его основной перевод: «снабжать», «доставлять», «обеспечивать», «предоставлять», например: «provide with goods» (снабдить товарами), «provide a car with a radio» (устанавливать в машину радиоприёмник), «provide housing» (предоставлять жилплощадь).

  • There is no way that we can provide another teacher for that class. — У нас нет никакой возможности пригласить ещё одного учителя в этот класс.


Основное значение слова «arm» — это «часть руки от кисти до плеча». В нашем тексте «arm» переводится как «рычаг», «плечо рычага», так как видео посвящено технической тематике. А вот, например, в военном деле «arm» могло бы переводится как «род войск», «крыло», «вооружение».

  • With a single turn of the arm, the optical fiber ferrules are released. — Одним нажатием на рычаг производится освобождение волоконно-оптических наконечников.

on its own

Идиома «on one's own» переводится как «сам», «самому», то есть мы что-то делаем самостоятельно, без помощи других. Следует упомянуть, что выражения «on my own» и «myself» обозначают совершенно одно и то же, отличие состоит лишь в конструкции написания.

  • The young girl has been on her own since she finished high school. — Молодая девушка живет сама по себе с тех пор, как она окончила школу.

Вы используете устаревшую версию браузера. Чтобы в полной мере использовать все возможности сайта, установите последнюю версию одного из браузеров: