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Anyone ever build a CATAPULT in their yard?

Melensdad

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Some call it a Trebuchet, others a Catapult or Mangonel, but has anyone ever built one? There are different versions. Swinging weight, fixed weight, bow tension, arm tension, etc. But in any form, its a big wooden machine used to lob boulders into your neighbors Castle walls.

I'm looking for a fun project I can build with my daughter. I'm not thinking of a full scale War-Wolf like used in England, but I would like something that could hurl a 12# bowling ball about 100 yards! :eek:

We've been watching the history channel too much, but honestly its been in the back of my mind for quite a while.

Any help would be appreciated!

And I'm not suggesting you send psychiatric help. :tiphat:
 

bczoom

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B_Skurka said:
And I'm not suggesting you send psychiatric help.
Too late.

I just used mine to launch a 16# bowling ball to your coordinates. It'll be there in 4-5 minutes. When it bonks you on your head, you'll come to your senses.
 

Dargo

Like a bad penny...
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Two years ago my oldest daughter needed to do a project on a catapult for school. She and I spent a weekend out in my shop and built a darn nice one, for a quickie. It was only to scale to toss golf balls. However, the design and function must have really been intriuging to the teachers; they still have it at the school! :mad: We've asked for it back a couple of times, but have now given up. They used it so much that they wore the paint off of it and had to repaint it. It's now part of their science exhibit. I'm also told that unless it is used in their gym, it is great for taking out the overhead lighting. :thumb:
 

Spiffy1

Huh?
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:coolshade
Any pictures Dargo?
What type?

The best I ever made was about marble size projectiles, and loaded with a rat-trap spring. Got some pretty nasty velocity though!
 

Melensdad

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DaveNay said:
Ummmm....why aren't you thinking that? :whistle:


Dave my main reason for scaling it down to bowling ball size ammunition is due to ease of loading. The War Wolf was reported to have hurled a 250# stone about 200 yards (a longbow shot off the castle wall would travel just under 200 yards). I see no reasonable way to gather 250# projectiles, and handling and loading them would be a chore. But it would be fairly easy to buy used bowling balls from the bowling alley, and be easy to load them into the catapult too. So its a matter of being practical.
 

DaveNay

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B_Skurka said:
I would like something that could hurl a 12# bowling ball about 100 yards! :eek:

:eek: is right!!

I just did some very quick calculations, and your little "toy" has roughly 4,250 ft-lbs of energy at launch.

For comparison, a 325 Gr .50 caliber Desert Eagle has approx 1,825 ft-lbs at the muzzle.

:applause::applause: I say go for it!
 

Melensdad

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I'm guessing this thing may be roughly 12' tall (depending on the design I choose). But as you know where I live, you are welcome to come out for the first throw.

BYOBB (bring your own bowling ball)
 

Dargo

Like a bad penny...
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Spiffy1 said:
:coolshade
Any pictures Dargo?
What type?

No picture. It had a 6" steel channel (legs down) for the base and side support. It was about 18" tall and used an old hood spring out of a '70 Chevelle for launching. I was concerned about someone getting hurt because I had to weld in a lateral cross bar to stop the cauapult at a certain position in order to have it actually launch the golf balls at the right angle. Without the stop, it simply slammed them into the ground a couple of feet in front of the catapult. If someone had their finger on that crossbar when someone else launched, it would at minimum break a finger.
 

Dargo

Like a bad penny...
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B_Skurka said:
I'm guessing this thing may be roughly 12' tall (depending on the design I choose). But as you know where I live, you are welcome to come out for the first throw.

BYOBB (bring your own bowling ball)

Bob, that sounds like something my kids want me to make to launch kids into the lake. I'd bet it would be one wild ride! It would kind of suck if it launched someone onto the island though... :pat:
 

TOMLESCOEQUIP

Just Plinkin Away the $$
Dargo said:
Bob, that sounds like something my kids want me to make to launch kids into the lake. I'd bet it would be one wild ride! It would kind of suck if it launched someone onto the island though... :pat:
You could test it with some of the owners of heavy tractors (some present company excepted of course) till you got the bugs worked out on the range & amount of spring tension.
 

Mith

The Eccentric Englishman
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Bob, this is a video of the Barley Pickers trebuchet they built to throw a mini. They were a ledgendary team from Scrapheap Challenge (Junkyard wars), farmers from down south.

Video --> Scroll down to 'The annihilation of the Barley Picker's Car-Throwing Trebuchet' in the videos section

Needless to say, they shoulda built it bigger :D


Many years ago some freids and I built a trebuchet out of 2 prefab roof trusses, a couple planks to hold it together and a smallish tree trunk for the main arm. I cant remember what we used for a weight, but it was very heavy, the arm was about 20 foot long, about 1/3 on the weight side and about 2/3 on the throwing side.
As with the Barley's trebuchet, the damage sustained on its first throw rendered it firewood :a1:

Cant wait to see it done! :tiphat:
 

Melensdad

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Mith, got any photos?

I'm looking to build something with roughly a 10' arm, probably making the arm out of triple-laminated 2x8 lumber.

Also, based on the TV shows and research I've seen, mine will be on wheels as opposed to on a flat base. The catapults that have wheels actually throw farther than the ones without wheels because the whole catapult rolls backwards slightly while the weight is falling, this allows the weigth to attain a much straighter drop path and reach higher velocity, thus allowing a farther throw. It also seems to take some of the stress off the unit.
 

DaveNay

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B_Skurka said:
Also, based on the TV shows and research I've seen, mine will be on wheels as opposed to on a flat base.

I'll bet a can of soda that you watched Nova on Tuesday night, huh Bob?
 

Melensdad

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Safe bet.

But scoured the internet and even took a visit to the library.
 

BoneheadNW

New member
DaveNay said:
I'll bet a can of soda that you watched Nova on Tuesday night, huh Bob?
Nothing gets past you Dave! I'll bet you that it will be the Steelers vs the Seahawks in the superbowl! :tiphat:
Don't mind me, must be hypoglycemic. Time for lunch!
Bone
 

humor_me

New member
B_Skurka said:
Some call it a Trebuchet, others a Catapult or Mangonel, but has anyone ever built one?

Any help would be appreciated!

And I'm not suggesting you send psychiatric help. :tiphat:

Bob,
When my oldest boy was in elementary school, we built a small catapault with sevral bungee cords as the power for a science project. All together, it was around knee-high as it needed to be portable enough to send to school with him. It could launch golf balls and tennis balls fairly respectably. But not necessarlily as a weapon.:thumb: Most of the fun, was the trial and error of making the arm.
 

Melensdad

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Well I found a scale model catapult plan that I am going to purchase. It has a catapult that has a 4' arm. I'm planning on scaling it up to an 8' or perhaps a 10' arm. If I understand the logic correctly, doubling the length of the arm increases the power by 100 times??? Is that possible? It doesn't seem logical to me. Anyway that should be a good summer project for me.
 

DaveNay

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B_Skurka said:
If I understand the logic correctly, doubling the length of the arm increases the power by 100 times??? Is that possible? It doesn't seem logical to me.

Doesn't seem right to me either. Do you have a link to someplace that you read that little bit?
 

Melensdad

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I don't remember if it was stated on Discorvery or History Channel or if I was reading something.
 

Melensdad

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The catapult plans arrived!

I sent a copy of the CAD drawings and instructions to DaveNay for some quick engineering assessments and he proclaimed "That is totally completely awesome!!!"

So with that expert validation from a fellow I consider to be as big a nutcase as myself, it only seems reasonable to enter the realm of becoming a medevil warlord.
 

Spiffy1

Huh?
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B_Skurka said:
If I understand the logic correctly, doubling the length of the arm increases the power by 100 times??? Is that possible? It doesn't seem logical to me. Anyway that should be a good summer project for me.

I'm thinking 4 times the power, and that's assuming you have so much tension on it that the extra lengh doesn't reduce the rotational velocity.

Regardless...:weneedpic:thumb: :thumb: :thumb:
 

DaveNay

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Spiffy1 said:
I'm thinking 4 times the power, and that's assuming you have so much tension on it that the extra lengh doesn't reduce the rotational velocity.

Hmmm....without getting too deep into the physics, doubling the size means you are increasing the mass by eight times. :eek: This means the arm will have a whole lot more inertia, and will be much more difficult to get moving in the first place, harder to get up to launch speed, and harder to stop without destroying the support structure. Whatever you are using for an energy source (suspended weight = potential energy, transfered to kinetic energy when you let it fall) will also need to be increased significantly when you double the size. I don't know if the weight will need to double, or if it will need to be 3x, 4x or whatever.

What material are you looking to build the arm with? Since this machine is based on the fundamental priciple of leverage, the biggest improvement to power come from increasing the length of the throwing arm. If switching materials will allow you to increase the length and minimize the effect on the mass, you will get better results. Perhaps an LVL beam?

And what makes you think I'm a nutcase?! Something in my eyes perhaps?! :657::657:
 

Melensdad

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DaveNay said:
And what makes you think I'm a nutcase?! Something in my eyes perhaps?! :657::657:
Or perhaps the lack thereof!:eek:



As for the materials, etc:
In the scale drawings, the main arm is 35" by 1.25" by 1". I plan to scale it up about 100%. So my main arm beam should be 70" by 2.5" by 2". I'm thinking I may have to rip down some 4x4 stock for that? Before getting the plan, I actually figured the main arm would be much stouter than that.

Actually, it strikes me now that it might be easier to build it with some heavy wall 2" by 2.5" (or close to those dimensions) rectangular steel tube. I would think the flex of the rectangular steel would be far less than that of similar size wood. The weight might be heavier on the steel arm, but that should not pose any real problem in the grand scheme of things. Heck it might be easier to make a large portion of this out of metal and weld it up.
 

OkeeDon

New member
I was thinking some flex might be a good thing. Think of a willow branch whipping at you as you walk through the woods. The final bit of spring-loaded energy imparted through th eflex of the arm might heave the projectile a bit farther and faster? It might cut down the accuracy.
 

Melensdad

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Don, I was thinking more of a golf club. The more advanced players use less flexible shafts and hit the ball farther.

But I suppose the ultimate answer will never be known. As I'm not planning to make multiple units of differing materials to do head-to-head comparisions. One major flaw I see in the CAD drawings is that the unit is a stationary unit as opposed ot a rolling unit. Putting the catapult on wheels will increase the thrown distance because it allows for the swinging weights to drop at higher velocity in a more vertical path by moving the entire catapult while the weight is falling. And from a practical standpoint, putting it on wheels makes it much easier to get out into the field too!
 

Melensdad

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:a1:
OK guys, I've found a copyright free set of plans so you can all make your very own CATAPULTS in your own back yards. (Get ready DaveNay, I'm aiming your direction!)

Here is a link to the plans in the PDF portion of the Photo Gallery: Trebuchet/Catapult Plans
 

Mith

The Eccentric Englishman
SUPER Site Supporter
Bob, it would be easier to make that out of box section steel dont you think? Just cut and weld, especially on the bandsaw to get the angles.
Do you think then it could handle lead in the weight? Fire much much further.
I will be getting about 82 foot of 1x1x1/8'' box steel soon to make some work benches, maybe a bit could be used to make one of them, very tempting.

I cant help but think that the sling would be very hard to make well, have you tried any of these things out?
 
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