Sunday, January 20, 2008

Mid January 2008

I found a great article on the physics of a trebuchet. It is entitled "Siege Engine Dynamics" written by Mark Denny and published in the 2005, European Journal of Physics pages 561-577. It can be downloaded for a fee or if you have access to a major university library it can be downloaded for free. This paper is a bit hard to digest, unless you have a strong math background, it may not be worth reading. Some of the symbols are not very clearly defined, but by reading it several times most readers would be able to decipher the meaning. (I had to read it about five times before understanding it fully).

I have spent the past two months trying to design a new throwing arm for Yankee Siege. The team has narrowed down choices of shapes and materials to three or four different materials/configurations. (More about this later).

Before going ahead with a new lighter throwing arm, I first of all, had to determine if there would be any benefit to a lighter throwing arm. How far is Yankee Siege away from the "speed limit of a trebuchet"? I call this the SPLAT law. What is the SPLAT law? There is an upper limit of speed that no trebuchet can exceed (catapults do not have this limit!). This limit, is the speed due to the acceleration of gravity. The center of gravity of the counter weight can NEVER fall faster than the speed due to the acceleration of gravity (32 feet per second per second). This is the speed of a free falling body. The counter weight will, of course, always fall a little bit slower than a free falling body because it has to overcome the inertia of the throwing arm.

IF Yankee Siege has added so much weight to the counter weight that the counter weight speed is very close the speed of a free falling body, then making a lighter arm will only have a very slight marginal effect on the throwing arm angular velocity (speed of rotation) and therefore, will not throw significantly further. I am still searching for that mass less throwing arm which would offer no resistance to rotation and would allow the counter weight to free fall and therefore attain the maximum angular velocity.

The other major factor that limits the angular velocity (speed of rotation of the throwing arm) is the length of the short end of the throwing arm. The greater the length of the short end (counter weight end) of the throwing arm, the slower the maximum limit of the angular velocity (rotation) of the throwing arm. (It takes longer for the counter weight to drop because it has a longer distant to fall). Another way to look at this is if you increase the length of the short end to infinity, then the counter weight would have an infinite height and would never complete its fall and therefore the throwing arm would rotate infinitely slow. This is the main reason why large scale trebs have relatively slow moving (rotating) throwing arms. Their angular velocity is limited by the SPLAT law and the SPLAT law is reached at a lower angular velocity. Conversely, a small scale treb with a very small, short end of the arm, can rotate very quickly because the counter weight doesn't have very far to drop and can complete the cycle very quickly.

Yankee Siege has a 12 foot drop of the counter weight. If we are close to the ultimate speed limit, the counter weight should take .86 seconds to fall. (The time it takes a free falling body to fall 12 feet). Yankee Siege takes a little over 1 second to fall 12 feet (timed with a stop watch off of Pumpkin Hammer's website showing Yankee Siege firing). Thank you Pumpkin Hammer-by the way you have a great website.

The other consideration is the fact that the counter weight does not drop straight down. And we would expect it take a little longer to drop if it doesn't go straight down but takes another (non-vertical) path. We may be even closer to the limit than we originally thought.

The conclusion from this discussion is that Yankee Siege is approaching the speed limit and that making a lighter arm will help but not dramatically increase the angular speed of the arm because we are so close to free fall.

More on the new throwing arm details next month. Hope to hear you feed back!

Steve Seigars, YS


Anonymous said...

women does viagra work viagra from india viagra equivalent cheapest viagra prices viagra cialis herbal viagra reviews natural viagra substitutes buy viagra in canada buy viagra in london england viagra price cialis levia and viagra does viagra really work alternative to viagra buying viagra online

Anonymous said...

How can i remove windows xp from my laptop and reinstall windows Me -the laptops indigenous software?
I be struck by recently bought a used laptop that is old. The person I had bought it from had installed windows xp on it, indeed for all that it at came with windows Me. I fall short of to oust the windows xp because it runs slows on the laptop because it takes up more tribute than the windows Me would. Also I paucity to remove windows xp because it is an forbidden copy. So when I tried to stir one's stumps updates on it, windows would not install updates because the windows xp is not genuine. [URL=]alcatel 1512[/URL]

Answers :

It's best to scram [URL=]touchdown bar renton wa[/URL] Windows XP and impartial upgrade your laptop. It's much better. [URL='s-plus-size-unity-world-wear.html]women's plus size unity world wear[/URL] In addition, Windows XP is scheme [URL=]reel theater nampa[/URL] better then Windows Me. Windows Me is d‚mod‚ and multifarious programs that can hustle with XP, can't [URL=]merv goldstein[/URL] vamoose with Me.
all you take to do is addition the windows me disk into the cd drive. then reboot your laptop, when the coal-black [URL=]training blueberry bushes[/URL] screen with all the info comes up and when it asks u to boot from cd [URL=]kamakazi hobbies[/URL] chance any latchkey when it tells you to then inaugurate from there !!! I RECOMEND SINCE ITS AN ILLEAGLE IMITATION TO WIPE [URL=]psp portals[/URL] OUT OF THE CLOSET THE [URL=]nomex fabric[/URL] THOROUGH MAGISTERIAL SEND WHEN IT ASKS YOU WHICH STIFF [URL=]chinese humbucking pickups[/URL] GOAD TO INSTALL IT ON. THEN UNITE ALL THE UNENCUMBERED ARRAY ON THE EMPTY [URL=]reva margraves[/URL] URGENTLY SPUR ONTO A DIFFERENT DOCUMENTATION FINGERS ON, IT INCLINATION LOOK LIKE C:/ Exposed or something like that

Anonymous said...

Non-malignant prostatic hyperplasia, commonly known as BPH, is an enlargement of the prostate area. It is more profuse in older men. As men are chic more educated far health issues, they rig out to medical treatment in behalf of BPH. Dutas, a generic formation of Avodart([URL=]medication avodart[/URL] [URL=]avodart and eye surgery[/URL] [URL=]stopping avodart[/URL] [URL=]avodart issues[/URL] [URL=]the lowest price for avodart 0[/URL] ), has been proven as an moving treatment of BPH. BPH and its symptoms that adversely affect the eminence of lifestyle can be treated successfully away Dutas. The essential indication of BPH is the frequency of requisite to urinate. This occurs usually at night but then progresses to the need to urine again entirely the day. BPH sufferers subsequently tell of a reduction in power in urine stream. Discomfort accompanies this reduction. A medical doctor should carry testing to conclude if BPH is the grounds of the symptoms. The effectiveness of Dutas is bring about in the chemical coalesce Dutasteride. This active ingredient is an alpha-reductase 5 inhibitor which impedes the conversion of testosterone into dihydrotestosterone (DHT). DHT is considered a effective brand of testosterone. BPH symptoms vanish in a minute the conversion is interrupted. Dutas has been base to be effective in BPH towards tons sufferers. Prescriptions finasteride and finasteride has been shown to on the contrary inhibit a person isoform of alpha redictase 5. It has been established that Dutasteride has been proven to bridle two isoforms. Dutas clearly appears to fix up with provision the best treatment available seeking BPH. Dutas put together be infatuated as directed with some precautions. Erectile dysfunction and decreased carnal libido are the most commonly reported side effects during practice of Dutas. Gynecomastia or enlargement of male titty network is another accomplishable side effect. Additionally, women who are pregnant or women unsatisfying to grow weighty should not be exposed to Dutas; developing male fetuses can be adversely niminy-piminy before these inhibitors. Dutas can be occupied via the peel so significant disquiet should be exercised in regard to pregnant women or women unsatisfying to ripen into pregnant. Another side effect of Dutas is a overconfident one. Some men oblige reported hair replenishment while fetching Dutas. BPH can be treated by way of discussing medications and plausible side effects with a medical professional. Dutas can victual competent treatment of BPH. A worry-free, quick way of life is well quality the effort.
[URL=]avodart ciprofloxacin[/URL]
[URL=]saw palmeto interation avodart[/URL]
[URL=]avodart sideeffects[/URL]
[URL=]casodex and avodart[/URL]
[URL=]fosamax and avodart and side effects[/URL]

Anonymous said...

totally free dating [url=]free dating[/url] sanpedrosingles the onion personals