I like to know, how big a trebuchet you would need to huck a one ton van a quarter mile? It's a function of counter weight and arm length right? It was radar tracked by two destroyers and a guided missile cruiser. I'll trust 'em on the measuring.

Saw it done off a steam catapult on the Connie. While it did have an 83 foot elevation advantage, it started on a flat trajectory. And that hollow body design would make it a poor first choice as a distance projectile.

__________________
Gimme a minute to read through Jay's latest observations...

Rule of thumb is a minimum of 40:1 mass ratio, counterweight to projectile. 100:1 is more optimum. So your one ton van needs something like 40-100 tons of counterweight.

As for size, I'll have to do some scaling. Trebarbaric is 60 feet tall and runs 6000 pounds of CW. (And throws 10 lb pumpkins really far. They've a bit overdone the mass ratio!) Anyhow, let's say your van hurler would have around 60 tons, or 120000 pounds. 2000 times Barbaric. Linear size scales roughly as the cube root of mass. Cube root of 2000 is around 12.6 so figure 60 * 12.6 = 756 feet tall. That's a bit unreasonable!

Vehicles HAVE been flung, but certainly not as far as that. Typically they're lacking the aforementioned mass ratio and are flung by machines roughly the size of Barbaric. There was a VW commercial a couple of years ago in which they were going to "unpimp the ride". They did hurl a car, but it didn't go far. Video subsequently turned up on the web of the first attempt, during which the trebuchet collapsed.

__________________
Cum catapultae proscribeantur tum soli proscripti catapultas habeant.

BigDon, you've tickled my memory cells. There's a tradition that the last cat shot of a cruise is a pair of boots. I just can't remember whose. Is it the Skipper, the CAG, or someone else. I do remember that during my three-day tiger cruise on the Saratoga, it was the last shot ever; I don't know how far they went, but I never saw them hit the water.
BTW: The last trap was to be made by an Admiral in an S-3; he boltered, but made it on the 2nd try. The rumor was that the co-pilot (a squadron CO) actually made the trap.

__________________
"I want to write about people I love, and put them into a fictional world spun out of my own mind, not the world we actually have, because the world we actually have does not meet my standards." Philip K. Dick
No matter how strong, or brave, or pure of heart you may be; sometimes the dragon wins!

Scientific American did a piece on some English professors who built one capable of hurling a small car about 10-15 years ago. (Shortly after the article appeared, the professors were hired to build a smaller one for the TV show Northern Exposure.)

__________________
We want our children to go to the planets. Burt Rutan 6/21/04
Tuckers! Science! Automotive Oddities! Boycott Trek XI! Building my hot rod with the help of the intarwebs Those who would delay scientific progress for a little temporary prosperity shall have neither. MachineCast

Like this?

http://www.micom.net/oops/Catting%20a%20Ford.jpg

John

"This site does not support hotlinking."

__________________
Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

No need to shout, Kaptain.

After my initial response I realized I could run this through a simulator. To my surprise, it actually let me put in the huge numbers and run it.
Counterweight = 60,000 kg.
Projectile = 1000 kg.
Throwing arm mass = 5000 kg.
Short Arm length = 40m
Long Arm length = 120m
Pivot Height = 90m
Counterweight Link = 30 m
Sling Length = 90m
Resulting range: 4314 m. Beats the 1/4 mile by a bit. I'll have to play further to look for a smaller one.

Note: This was run in "simple" mode, with aero and friction turned off. That would likely reduce the range by half or so.

__________________
Cum catapultae proscribeantur tum soli proscripti catapultas habeant.

Well thank you for your time Treb!

I guess this means the Romans wished they had steam catapults.

__________________
Gimme a minute to read through Jay's latest observations...

No, BigDon, everyone wishes they had a nuclear-powered steam catapult.

The list of things you can throw is endless. I would start with my mother-in-law.

Thank you so much for pointing that out, KK.
(reaches for new eardrums)
My sincere apologies for expecting you not to know any other way of accessing a website. But someone like you will always want to learn. There are many ways to access a page, hotlinking being merely one. Another is to copy that URL into the address line of your browser and press return.

"Learning? I'll learn'em!" - Toad of Toad Hall

John

Slight correction 120,000/6000=20 times Barbaric, cube root is 2.7144, so 2.7*60 feet is about 160 feet or 50 meters, much more reasonable.

Now imagine that one chucking a bag of 500 4-pound stones at an advancing army of orcs
Now imagine the bag splitting in mid-throw

__________________
And the "driving on the freeway on a scooter" analogy still holds true because the pilots are sitting in 7 to 30 ton aircraft o' doom and you are running around them in your very own Meatbody, Mark I. Beep, beep.
Trying to make sense of computers, The Error Log.

Thanks for the correction. I always did have a problem with getting those pesky decimals in the right place. And I had to go to school in the age of slide rules!

Regarding the bag of stones, the final throw for the day at Burlington always involves hurling candy. They used to do that in bags which were prepared to split open in flight, just about as you describe. Last year, however, they put it in hollow pumpkins. After the last one lands, the kids take the field!

__________________
Cum catapultae proscribeantur tum soli proscripti catapultas habeant.

Quick Trebuchet question, for the knowledgeable around here. What mechanism is used on those to release the intended projectile at the right angle? I see slings being used, and it almost looks as if one end of the sling becomes undone at the release point.

__________________
Currently conducting pre-deployment training, shortly followed by mobilization to Iraq. Note that PMs may take a long time to be responded to.

Slings are perhaps the least understood part of catapulting to the uninitiated, leading to the not-historically-accurate use of cups on the arms of catapults in movies. Yet they are very simple, no complex release mechanism involved.

One end of the sling is permanently attached to the end of the arm The other end has a loop or ring which is placed over a pin on the end of the arm. As the arm rotates, the sling swings out until it reaches a point where the loop comes off the pin and the projectile is off. The actual release point is determined by the length of the sling and the length and angle of the pin. For a classic trebuchet, a sling about 3/4 the length of the arm is a good starting point.

It is entirely possible, with the wrong sling setup, to throw backward!

__________________
Cum catapultae proscribeantur tum soli proscripti catapultas habeant.

That's the big difference between catapult and trebuchet, isn't it? A catapult relies on the flexing of the main spar, and a Trebuchet relies on a smoothly rotating arm with a counterweight. Right?

__________________
Currently conducting pre-deployment training, shortly followed by mobilization to Iraq. Note that PMs may take a long time to be responded to.

I think a catapult is something that throws stuff. That includes BigDon's nuclear steam powered ones! A trebuchet is a specific type of catapult, using a long beam with a counterweight for power.

I don't know of any off hand that actually flex the throwing arm. The type you're probably thinking of is the mangonel or onager, which gets its power from a bundle of twisted rope at the base of the arm. See www.onager.net for a great example. I've built a small one like that. The power is amazing.

An onager, by the way, is really a type of wild jackass. The name got applied to the catapult because of the tendency for the back end to kick up!

__________________
Cum catapultae proscribeantur tum soli proscripti catapultas habeant.

Is it possible to build a mechanism into a trebuchet that pulls the sling throught the end of the arm during the throw, decreasing the length of the freely swinging sling. Would this accelerate the projectile even further? For example attach the sling to a shuttle that travels along the arm and have the shuttle move towards the counterweight end by means of a spring or another counterweight.

I think what the Kaptain is trying to say, is that it is against the board policy to allow hotlinks to an image. You can do it, but it's discouraged, something to do with stealing bandwidth etc.

I wonder if there is a way to use multiple weights in a sort of compound-bow type trebuchet. Multiple weights and a transmission, or something.

__________________
Currently conducting pre-deployment training, shortly followed by mobilization to Iraq. Note that PMs may take a long time to be responded to.

One of the best tricks for something like that was to have the counterweight connected to the arm through a pivot with movement limited so it wouldn't turn once the arm had been pulled partway down, as you can see in the attached (admittedly primitive) sketch.

The advantage is that the counterweight acts through a longer arm for the first part of the throw which adds power, while the different swinging frequencies of the various parts in the free-swinging part of the action, if correctly designed, can lead to significant dampening of the post-release swinging.
It is also my impression that it could keep traverse forces to the point were a fairly large trebuchet could be mounted in a tower without tearing said tower about.