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The Atomic Bomb of the Middle Ages
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Other F.A.T.s in the world.

I get a lot of requests for plans for the FAT, and you can some them here - These are not the same as the fat on this page. I didn't write anything down when I built it and I don't remember the details. The machine was lost to vandalism outside my warehouse in Los Angeles many years ago.

Having said that... Here are some examples of projects that other people have completed based on the pictures and descriptions I published for my Original F.A.T. page. Pretty impressive stuff here, and proof that with a little mechanical skill and a good set of tools, everything you need to know to build your own machine is already here!

I've heard of many more than these, but I've only posted the ones that sent me visuals. You can build one too! And if you do, please send me photos so I can add them to this list! Be careful, and have fun!

-- Ron Toms

John Purchard

Hi Ron,

Finally got some pics of the FAT2K I built after finding your site back in the spring of 2001. I used sixteen 34" oak staircase rungs that are 1.125 inches square. The rails are 1" by 1/8" angle iron. I used rollerblade wheels with a rollerskate axle. Roller-skate ballbearings were user for the end of rail roller. The arm is a hockey stick. The current ratio is 2.1:1. CW shown is 15 lbs. and is my usual charge, golfballs go about 150'. The CW axle is 3/8" and it bent when a charge of 72 lbs. was loaded, but the cricket ball went 200 feet.

I used your trigger design but used 5/16" square bar instead of angle iron. This change simplified the trigger construction and mounting. The release pin is "U" shaped and fits into holes drilled in the iron bars. A safety pin fits into a smaller hole that goes through the iron bar and one end of the "U-pin". The design is simple and I have planned to increase the axle to 1" and double the height (tallness) of the towers. With variable pin angle and wheel position I can have lots of flexability and fun.

Earl Tyler

Ron -

Sometime back in the Fall, for reasons that I still don't understand, I decided to build some sort of catapult-like device. Fortunately for me, I decided to see what information was available on the net , & I ended up at I was immediately infatuated with your FAT design & soon began building one with the assistance of my neighbor Mark Pierce.

We used the same basic dimensions as yours: 9' beam, 2:1 ratio, 4.5' to rails, 5.5' drop. We made 12"x12"x8" CW buckets out of 1/4" steel from the junk yard. To fill the buckets we used cast iron bottle molds I also found at the junk yard. The frame is all made of 2x4 spruce. The beam is 2x6 yellow pine, tapered to 3" at the pin. The CW end of the beam has an additional 2x6 & a piece of 1" oak screwed & glued to each side. This lamination extends beyond both axles.

Attached are a couple of pictures of the machine. The first one shows us getting ready to haul the weights up. As you can see, we still use prison labor here in the south. In the second picture the machine is cocked, & we are preparing for a shot. Note the 5/8" steel safety rod extending through the frame. I would not be leaning over the beam without that safety!

So far we have launched mostly small mellons that weigh about 6 lb. using CW up to 500 lb. I measured the distance to the farthest melon piece at about 570'. We were throwing slightly downhill though. Allowing for the hill & the splatter effect of the melons, I guess we were coming close to 500'. After about 25 throws, there was noticable bending in the 5/8" mild steel axle.

We have plans to replace the wheels & axle with more substantial ones. Also we left the vertical CW guides tall enough so that we can convert to F2K (if that is the proper term) at some time in the future.

Thanks for the inspiration!

Josh, Chris, and Adam - Connecticut
Hey Ron,

In the end of September 2001 my friends and I Decided to build another trebuchet. We built a FAT this time. I my self have built 3 swinging counterweight types in the past but never a FAT. We knew that we wanted to fling far.

Are all 15 years old except for Adam who is now 16. We didn't do it for school or anything, just for the heck of it. It took about a week to complete and 70 dollars. Up in New England we get rain frequently so we just recently coated it in waterproffer and stain, so it looks very nice. Currently we use 250lbs of counter weight and fling about 3 lbs objects 325 ft, but we havent had much time to test it all. In late december we are going to try a new weight bar and more weight to see what this thing can really do.

The FAT is 6 ft at the top of the runners and 6 ft long. The arm is 8 ft long. The entire thing is comprised of 2x4's. We will be entering this one in a contest in late May, but in April we plan on building a much larger one, which plans are being made for. This current one has very detailed plans on how to construct it which I made just by looking at yours.
Any ways here are some shots of it.

Mark Denlinger
About a year ago Ken Dulaney, a friend at work, asked me if I wanted to build a machine to launch pumpkins and enter a local contest. I knew instantly that I wanted to do it. So Team Punkin'Air (4 engineers) set out to build the machine in the Fall of 2000 to enter the Raleigh, NC chunk. We found and happened to see the Nova special on the authentic trebs in Scotland at the same time. We decided to build a straight drop treb but we added a twist to Ron's floating axle design: we used a cam instead. That was Ken's idea. The cam is the most important part of our machine. It allows a straight CW drop which allows the CW to pick up some momentum before having to lift the pumpkin off the ground, and - most importantly - offers a graduated lever arm which really kicks in near the end of the throw to accelerate the sling. The arm rolls across the cam - there is no axle. We tuned the shape of the cam and the overall design on the computer using Working Model 2D based on a 400 lb CW and a 10' drop. (see the .avi file here)

The machine worked from the first throw. That still amazes me. We use Olympic-style weightlifting plates for the CW which slip onto a 6' long 2" diameter solid steel bar. The bar/weight assembly is attached to the arm by passing the 2" bar through a slightly larger sleeved hole in the CW end of the arm.

We did 350' for the 2000 Raleigh chunk. The 2001 revisions were mounting the machine on a dedicated trailer, longer vertical posts for an 11.5' CW drop, more CW for a total of 540 lb, a 13.5' arm made of LVL, a better trigger (so we didn't have to climb a ladder each throw to set it) and a campaign to reduce friction. All of which resulted in about 4 months of successive weakest link failures. In the fall of 2001 we got off about 20 throws at the Funk's Farm chunk in Lancaster, PA. We did 647' in the 2001 Raleigh chunk and 614' at our first appearance in Delaware. I am completely hooked on throwing pumpkins through the air. Our motto is "You Grow 'Em, We Throw 'Em".

Tim. C. Lubcke, Australia
Hi Ron,
This first picture:
followed my first design where the arm fell first and slid on a back post which acted like a fulcrum point to the end of the load arm- giving the effort maximum potential to gain momentum before the wheels landed and thus extended the load arm- giving the arm a good chance of gaining some serious speed. Alas, I could not make a wheel axle that could handle that much impact.

After that, I changed it as so the wheels in this pic:

never left the rail. The final floating arm trebuchet-
had to be raised off the ground by around 200mm as so the arm could be drawn back further and the slide section for the counter weight lost a good 500mm. I'm still in the testing stage and has too much friction to call it very efficient but will cut back a bit and maybe use a touch of graphite here and there..... -Thanks for all your support and interest Ron, you have helped me out a lot and is a regular visiting for me!

Keep on encouraging the enjoyment of building these fascinating machine and all the great work!!!

Jim G.
I hope we have not infringed on your rights by copying one of your trebuckets. [editor's note: The FAT design is free to use, copy and modify for non-commercial purposes only. --Ron Toms] It will be entered in a northwest Kansas youth group pumpkin throwing contest October the 13th. I think this machine will do very well. As practice ammo we were using gallon jugs of water but soon ran out of jugs as they do not survive the landing well. A better choice was a old basket ball with about 5 pounds of sand in it (one pumpkin weight) with 350 pounds of weight we can through the ball a consistent 290 feet. This machine is made from junk lumber and using tractor wheel weights

Brent Burton
Using Ron's pictures as a guide, I started building a FAT a couple weeks ago, and tonight launched the first projectiles. This treb works very well, but a few of the changes I made are simply wrong (not tall enough, arm too heavy and not long enough). Sometime I'll correct it, but modifying a built treb won't be easy.

I made a web page with pictures and a video. Sorry, but the page is a bit large (350K with pictures). The video is almost 6MB but is high quality.

At this stage, the treb needs tuning but is working well.

Chuck Shriver:
Ron my name is Chuck I'm a welding instructor in Ohio. We built one like your wooden one but out of metal. We threw 432.5 with 900lbs Cw. We are going to try some modifications to try to get 600 to 700 ft. My kids in my senior class had a fun time with this.

[ And here are those modifications he mentioned.... ]

Ron this is Chuck from Ohio. We did some mods to the treb- raised the whole thing up to 7 and half feet to the tracks, 13 feet to the top, 15 foot arm (10 foot from pin to axle) and went to an aluminum arm with 1000 pounds of weight throwing an 8 pound bowling ball. We are throwing 800 - 850 feet! [ Good work Chuck! ]

Tim Prude wrote:

Ron: We went to the High School shoot off contest last weekend. The rest of the trebs were on average 20 ft. tall with a 30 ft. beam, capable of throwing 15 lb. pumpkins about 200 ft. Our little treb would shoot 5 lb pumpkins about 330 ft. (We were limited to 300 lbs counterweight.) We won the farthest throw and the fastest throw at 73mph. Great fun was had by all. The rest of the trebs were of conventional design, ours was the only floating arm design. Nobody else thought we had a chance, until our first shot. We really astounded them. Again, thanks. I have attached a 10 second video of one of our trial shots back behind my house in the alley. If you can make it work, you will see the launch, then the pumpkin flying through the air, then it disappears from sight, then you hear a loud thud, which is the pumpkin hitting the roof of the two story church bldg. about 300 feet downrange. No damage to the roof!!!

Eric Poll Wrote:
Here are some pictures of the Treb that Mark and I made for our engineering course. Everyone was VERY impressed with it and its performance. Our best result was with a 5lb Melon launching 80 meters (about 240 feet) using 200lb of counter-weight. Unfortunately, that launch split the arm at the attachment to the dowel. The whole thing took us about 2 days to build and test. We were slightly restricted as to how big we could build this thing. As such, we decided to build the treb in modules. The arm, the 2 rails, the weight buckets, centerpiece and dowels were put together independantly. Assembly took about 10 minutes (15 minutes if we are being fussy). We won the competition without dispute!!! There was another trebuchet in the competition and it worked VERY well. It was a standard treb but was a little small.. it could only accept 150lbs of counterweight.. they launched a orange 64m. There were two other catapults that didn't fair too well. Both were spring types but neither one of them could wind the coil up sufficiently to deliver an adequate distance. Neither one of them could reach 40 meters.

Here's what the competition was shooting with.....

Tell your friends!


Interesting Notes

Some Trebuchet History:

From the 13th century writing: "Itinerarium Peregrinorum et Gesta Regis Ricardi"

In June and July of 1191, Richard the Lionheart (the Duke of Normandy) laid siege to the city of Acre as part of the medieval Crusades.

The Duke concentrated on constructing siege machines and placing trebuchets [petrariae - literally, stone hurler] in suitable places. He arranged for these to shoot continually day and night. He had one excellent one which he called "Bad Neighbor" [Malvoisine]. Its continual bombardment partly destroyed the main city wall and shattered the Cursed Tower. On one side the Templars' trebuchet wreaked impressive devastation, while the Hospitallers trebuchet also never ceased hurling, to the terror of the Turks.

Besides these, there was a trebuchet that had been constructed at general expense, which they called "God's Stone-Thrower". A priest, a man of great probity, always stood next to it preaching and collecting money for its continual repair and for hiring people to gather the stones for its ammunition. This machine at last demolished the wall next to the Cursed Tower for around two perches' Length [11 yards or 10 meters].

The count of Flanders had had a choice trebuchet, which King Richard had after his death, as well as another trebuchet which was not so good. These two constantly bombarded the tower next to a gate which the Turks frequently used, until the tower was half-demolished. Besides these, King Richard had two new ones made with remarkable workmanship and material which would hit the intended target no matter how far off it was. . . . He also had two mangonels [traction trebuchets] prepared. One of these was so swift and violent that its shots reached the inner streets of the city meat market.

King Richard's trebuchets hurled constantly by day and night. It can be firmly stated that one of them killed twelve men with a single stone. That stone was sent for Saladin to see, with messengers who said that the diabolical king of England had brought from Messina, a city he had captured, sea flint and the smoothest stones to punish the Saracens. Nothing could withstand their blows; everything was crushed or reduced to dust.