Ladies and gentlemen, I present to you:
The FIRST EVER (Free) COMPLETE GUIDE FOR CREATING YOUR VERY OWN FLOATING ARM TREBUCHET
Of this size, anyway. When i was looking for a good set of plans for a floating arm trebuchet, i couldn't find a single free one. I know that a lot of people share my frustration in not being able to find free plans- so I wanted to create the first one. This is a guide that will show you exactly how to build one. As always, let me know if there is anything I can do to improve it-and I will add a video after I figure out how to.
I had a school science project (not fun) so I wanted to make it fun by building something cool. My friend and I previously made a catapult that was 7 feet high, and threw a baseball 40 ft. It was pretty bad. So this is a way to make up for that. The height of the channels is 8 feet, But the arm rises higher than that in its resting position. The arm is 7 feet. The short arm/ long arm ratio is what I was testing, and the different ratios are 2:1, 2.5:1, 3:1 and 3.5:1. I won't tell you which one was the best yet, although you can probably guess. The counterweight is about 36 pounds, but the big, wide wood piece (the short arm) was probably around 20 lbs. I'm still not quite sure... The total cost for me was around 130$. I don't think it was more than that.
If you want more information on how a floating arm trebuchet works, there are plenty of videos on the internet.
I would visit Ron Toms's site, he's the inventor of this type of trebuchet.
I want to apologize for not having very many pictures of the building process, but I made sketchup models, so hopefully they will help. There are several things that could be improved, which are listed on the last page. The first good throw was about 206 feet, although the trajectory was way too steep, to the point where we could not see the baseball. So, I'm guessing that a baseball would go in excess of 300 feet! And that's with only about 50 pounds of counterweight. A 1 lb projectile would probably go about the same distance. Trust me, it's powerful. We just need to fix the pin and find the best sling length. The sling length is also probably not perfect. I'm still tweaking. Most throws went either straight down or backwards. The backwards throws were caused by a glitch in the guide system for the arm as it falls. The pin was also previously a double-headed nail and a keychain ring. The ridges in that ring would sometimes get caught on the two heads of the nail, which we think is the reason for the downward throws. So, you should include in this project the turnbuckle pin system, which is based off of this trebuchet: http://www.trebuchet.com/10101
.
The entire thing took me about 2 months to build, but I wasn't working on it every day.
The diagonal 2 X 6s that attach to the longer drop shannel diagonals were not included in this instructable because they were a lot of trouble to add to it and I don't think they were really needed or worth it.
Always be careful; never fire it around windows or people.
Also, be very careful with the trigger. When you pull it out, it tends to fly towards the person pulling the trigger very quickly. Always hold the rope at the very end and jump out of the way after you pull it.
Let's start...
Oh but wait before you do...Remember to look at EVERY SINGLE ONE of the picture notes. I'm sure they'll help you a lot...
Credits: (Yes I just had to)
My mom and dad for paying for (almost) all of it
and for putting up with a messy cluttered garage
My friend, Michael, for always helping me with the loading and firing.
My neighbor and.. older friend, Joe, (He's an adult) for giving me tips on building the thing, especially the trigger design. He always believed it would work, unlike my dad. But my dad payed for most of it so I can't complain.
Coby helped move the trebuchet back from school (His grandpa has a pickup truck) and also helped me load and fire on one of the testing days.
Thank you to everyone that helped.
The FIRST EVER (Free) COMPLETE GUIDE FOR CREATING YOUR VERY OWN FLOATING ARM TREBUCHET
Of this size, anyway. When i was looking for a good set of plans for a floating arm trebuchet, i couldn't find a single free one. I know that a lot of people share my frustration in not being able to find free plans- so I wanted to create the first one. This is a guide that will show you exactly how to build one. As always, let me know if there is anything I can do to improve it-and I will add a video after I figure out how to.
I had a school science project (not fun) so I wanted to make it fun by building something cool. My friend and I previously made a catapult that was 7 feet high, and threw a baseball 40 ft. It was pretty bad. So this is a way to make up for that. The height of the channels is 8 feet, But the arm rises higher than that in its resting position. The arm is 7 feet. The short arm/ long arm ratio is what I was testing, and the different ratios are 2:1, 2.5:1, 3:1 and 3.5:1. I won't tell you which one was the best yet, although you can probably guess. The counterweight is about 36 pounds, but the big, wide wood piece (the short arm) was probably around 20 lbs. I'm still not quite sure... The total cost for me was around 130$. I don't think it was more than that.
If you want more information on how a floating arm trebuchet works, there are plenty of videos on the internet.
I would visit Ron Toms's site, he's the inventor of this type of trebuchet.
I want to apologize for not having very many pictures of the building process, but I made sketchup models, so hopefully they will help. There are several things that could be improved, which are listed on the last page. The first good throw was about 206 feet, although the trajectory was way too steep, to the point where we could not see the baseball. So, I'm guessing that a baseball would go in excess of 300 feet! And that's with only about 50 pounds of counterweight. A 1 lb projectile would probably go about the same distance. Trust me, it's powerful. We just need to fix the pin and find the best sling length. The sling length is also probably not perfect. I'm still tweaking. Most throws went either straight down or backwards. The backwards throws were caused by a glitch in the guide system for the arm as it falls. The pin was also previously a double-headed nail and a keychain ring. The ridges in that ring would sometimes get caught on the two heads of the nail, which we think is the reason for the downward throws. So, you should include in this project the turnbuckle pin system, which is based off of this trebuchet: http://www.trebuchet.com/10101
.
The entire thing took me about 2 months to build, but I wasn't working on it every day.
The diagonal 2 X 6s that attach to the longer drop shannel diagonals were not included in this instructable because they were a lot of trouble to add to it and I don't think they were really needed or worth it.
Always be careful; never fire it around windows or people.
Also, be very careful with the trigger. When you pull it out, it tends to fly towards the person pulling the trigger very quickly. Always hold the rope at the very end and jump out of the way after you pull it.
Let's start...
Oh but wait before you do...Remember to look at EVERY SINGLE ONE of the picture notes. I'm sure they'll help you a lot...
Credits: (Yes I just had to)
My mom and dad for paying for (almost) all of it
and for putting up with a messy cluttered garage
My friend, Michael, for always helping me with the loading and firing.
My neighbor and.. older friend, Joe, (He's an adult) for giving me tips on building the thing, especially the trigger design. He always believed it would work, unlike my dad. But my dad payed for most of it so I can't complain.
Coby helped move the trebuchet back from school (His grandpa has a pickup truck) and also helped me load and fire on one of the testing days.
Thank you to everyone that helped.
trebuchetcurrent~.skp227 KB
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Signing UpStep 1: Materials
This list of materials is copied directly from my science fair project. It includes what I used at the time. The lumber list is really long, but I think I bought somewhere around 20 8' long 2 X 4s, I'm not sure... This still does not include the 2 X 6 pieces or any other pieces of plywood. I would still recommend that you read through the list, and buy the lumber as you need it to avoid wasting wood. Buy 15 2 X 4s to start off with, then buy more later. Also, if I mention anything else in the instructable that I didn't mention here, let me know.
Materials
Lumber
2 segments of 6 ft. (1.8288 m) long 2 X 4
These are the horizontal beams that are used as the track.
2 segments of 6 ft. (1.8288 m) long 1 X 6
Long sides of the base
2 segments of 2 ft (0.6096 m) 1 X 6
Short sides of the base
*It would be better if the two previous 1 X 6 pieces were 2 X 6, I'll explain later.
2 segments of 6 ft., 2 in. (1.8796 m) long 2 X 4
2 segments of 5 ft., 10 in (1.7272 m) long 2 X 4
The two previous segments are diagonal supports. Cut at least 3 inches longer unless you are very good at cutting angles accurately (A miter saw would help)\
2 segments of 8 ft (2.4384 m) long 2 X 4
These will be the drop channels
*look at the last step: improvements. This may need to be changed.
8 segments of 3 ft., 6 in (1.0668 m) long 2 X 4
Main track supports
look in improvements, may need to be changed
4 segments of 4 ft., 5 in. (1.3462 m) long 2 X 4
These are the pieces of wood directly on either side of the drop channels.
2 segments of 2 ft., 11 in. (0.889 m) long 2 X 6
3 segments of 3 ft (0.9144 m) long 2 X 6
More diagonal supports. These Are not included in the instructable because I did not think they were necessary. I might include them later. If you really want to include them, they should also be cut about 3 inches longer, until you know what to cut.
2 segments of 1 ft., 0.5 in. (0.3175 m) long 2 X 4
lateral supports
2 segments of 2 ft. (0.6096 m) long 2 X 4
extra lateral support
4 segments of 1 ft., 5 in. (0.4318 m) long 2 X 4
4 segments of 1 ft., 5 in. (0.4318 m) long 2 X 6
diagonal supports, lateral and track-supporting
2 segments of 3 ft. (0.9144 m) long 2 X 4
6 segments of 2 ft., 5 in. (0.7112 m) long 2 X 4
These make up the short arm
May need to be shortened, look at improvements
2 rectangles of 3/4" in. (2.54 cm.) thick plywood, 2 ft., 5 in. X 3.5 in. (0.7112 X 0.0889 m)
Plywood also included in the arm
1 segment of 7 ft. long 2 X 4
the arm itself
2 rectangles of 3/4 inch (1.905 cm) thick wood, 1.5 in. by 2 in (0.381 X 0.0508 m)
The two bits at the open top of the cut channel..keeps the drop channel from "opening"
*look at the last step, improvements. This may need to be changed
4 rectangles of 3/4 inch (1.905 cm) thick wood 9.5 X 5.5 in (0.2413 X 0.1397 m)
4 rectangles of 3/4 inch (1.905 cm) thick wood 9 X 4 in. (0.2286 X 0.1016 m)
4 rectangles of 3/4 inch (1.905 cm) thick wood 9.5 X 9 in. (0.2413 X 0.2286m)
Threee previous sections are for the counterweight boxes. This might change depending on your weights setup. This is what fit for me. Also, 1 inch thick wood would would be stronger.
Hardware
about 250 2.5 in. (6.35 cm.) wood screws, phillips head drive, #8
I would get more in case some of their heads strip...
if you buy pt lumber make sure they are approved for use in it..
8 .5 in. (1.27 cm) wood screws, phillips head drive, # 8
16 1.5 in (3.81 cm.) wood screws, phillips head drive, #8
3 ft. (0.9144 m.) long 5/8 in. (1.5875 cm.) diameter threaded rod, coarse thread
NEEDS TO BE MADE THICKER: LOOK AT IMPROVEMENTS
2 segments of 2 ft. (0.6096 m.) long 5/8 in. (1.5875 cm.) diameter threaded rod, coarse thread
May need to be made thicker
20 5/8 in. (1.5875 cm.) nuts, coarse thread
for the threaded rod
24 5/8 in. (1.5875 cm.) washers
again for the threaded rod
10 1/4 in. (0.635 cm) diameter, 5.5 in. (15.24 cm.) long carriage bolts
For the arm assembly
6 1/4 in. (0.635 cm) bolts, matching thread
for the carriage bolts
6 1/4 in. (0.635 cm) washers, matching carriage bolts
for the carriage bolts
3/8” X 4” eye bolt (Including bolts)
8 matching cut washers
these will be used in the trigger
2 1/2” X 10” eye bolts
these are the trigger pins
Wheels, weights
3 3 in. X 1.5 in. (7.62 X 3.81 cm) diameter wheels, 5/8 id bearing load rating of 200 lbs (90.71 kilos) or more
May need to be hanged if the diameter of the threaded rod is changed
excellent site for cheap, strong wheels http://www.thecasterguy.com/
2 hand weights, 10 lbs (4.54 kilos)*
2 hand weights, 8 lbs (3.63 kilos)*
*must be able to fit inside counterweight boxes
Sling
Approx. 50 ft. (15.34 m) of 3/16” (0.47625 cm) braided polyester cord
The sling lines, I bough 50 ft because i needed to cut the right lengths for each ratio, you probably wont really need more than 15 ft.
Approx 25 ft. (7.62 m)1/2” braided nylon rope
(This is actually for the trigger)
15 in. X 6.5 in (38.1 X 16.51 cm.) denim fabric
for the sling
Just find a pair of old jeans
Approx. 10 ft. (3.048 m ) of gorilla tape
for the sling
1 keychain ring
A solid metal ring of any kind would work better.
One thick nail.
This is the pin.
I don't know what gauge mine was, I found it in the trash Buy one that is at least 4 inches. The thicker the better to prevent it from bending. You should also cut off the head if you keep getting downward throws no matter how you adjust it.
If you want a better pin system, look at the turnbuckle pin system here.
(third picture on the right) RLT industries trebuchet.com
Tools
erm...
common tools
hacksaw if you don't have a METAL CUTTING BLADE FOR YOUR JIGSAW,
jigsaw the one I used here
circular saw (The one I used here) OR miter saw AND table saw
you need to miter, rip, and crosscut.
drill (The one I used here came in a kit here) with a varied drill bit set, for pilot holes, etc. One drill bit MUST be the size of your threaded rod (Mine was 5/8", it should be thicker) Ideally, the drill bit would be a foot long, or 6 inches, so that the holes in the arm don't become misaligned. I'll explain later...
also screwdriver bit driving in your screws.
coping saw and orbital sander (The one I used here)
Socket wrench for your threaded rod
speed square
...I'm kinda adding these as I think of them..
Tape measure, ruler
rubber mallet
claw hammer
um..
I think that's it
OK onto step 1
the base...
the beginning...
Materials
Lumber
2 segments of 6 ft. (1.8288 m) long 2 X 4
These are the horizontal beams that are used as the track.
2 segments of 6 ft. (1.8288 m) long 1 X 6
Long sides of the base
2 segments of 2 ft (0.6096 m) 1 X 6
Short sides of the base
*It would be better if the two previous 1 X 6 pieces were 2 X 6, I'll explain later.
2 segments of 6 ft., 2 in. (1.8796 m) long 2 X 4
2 segments of 5 ft., 10 in (1.7272 m) long 2 X 4
The two previous segments are diagonal supports. Cut at least 3 inches longer unless you are very good at cutting angles accurately (A miter saw would help)\
2 segments of 8 ft (2.4384 m) long 2 X 4
These will be the drop channels
*look at the last step: improvements. This may need to be changed.
8 segments of 3 ft., 6 in (1.0668 m) long 2 X 4
Main track supports
look in improvements, may need to be changed
4 segments of 4 ft., 5 in. (1.3462 m) long 2 X 4
These are the pieces of wood directly on either side of the drop channels.
2 segments of 2 ft., 11 in. (0.889 m) long 2 X 6
3 segments of 3 ft (0.9144 m) long 2 X 6
More diagonal supports. These Are not included in the instructable because I did not think they were necessary. I might include them later. If you really want to include them, they should also be cut about 3 inches longer, until you know what to cut.
2 segments of 1 ft., 0.5 in. (0.3175 m) long 2 X 4
lateral supports
2 segments of 2 ft. (0.6096 m) long 2 X 4
extra lateral support
4 segments of 1 ft., 5 in. (0.4318 m) long 2 X 4
4 segments of 1 ft., 5 in. (0.4318 m) long 2 X 6
diagonal supports, lateral and track-supporting
2 segments of 3 ft. (0.9144 m) long 2 X 4
6 segments of 2 ft., 5 in. (0.7112 m) long 2 X 4
These make up the short arm
May need to be shortened, look at improvements
2 rectangles of 3/4" in. (2.54 cm.) thick plywood, 2 ft., 5 in. X 3.5 in. (0.7112 X 0.0889 m)
Plywood also included in the arm
1 segment of 7 ft. long 2 X 4
the arm itself
2 rectangles of 3/4 inch (1.905 cm) thick wood, 1.5 in. by 2 in (0.381 X 0.0508 m)
The two bits at the open top of the cut channel..keeps the drop channel from "opening"
*look at the last step, improvements. This may need to be changed
4 rectangles of 3/4 inch (1.905 cm) thick wood 9.5 X 5.5 in (0.2413 X 0.1397 m)
4 rectangles of 3/4 inch (1.905 cm) thick wood 9 X 4 in. (0.2286 X 0.1016 m)
4 rectangles of 3/4 inch (1.905 cm) thick wood 9.5 X 9 in. (0.2413 X 0.2286m)
Threee previous sections are for the counterweight boxes. This might change depending on your weights setup. This is what fit for me. Also, 1 inch thick wood would would be stronger.
Hardware
about 250 2.5 in. (6.35 cm.) wood screws, phillips head drive, #8
I would get more in case some of their heads strip...
if you buy pt lumber make sure they are approved for use in it..
8 .5 in. (1.27 cm) wood screws, phillips head drive, # 8
16 1.5 in (3.81 cm.) wood screws, phillips head drive, #8
3 ft. (0.9144 m.) long 5/8 in. (1.5875 cm.) diameter threaded rod, coarse thread
NEEDS TO BE MADE THICKER: LOOK AT IMPROVEMENTS
2 segments of 2 ft. (0.6096 m.) long 5/8 in. (1.5875 cm.) diameter threaded rod, coarse thread
May need to be made thicker
20 5/8 in. (1.5875 cm.) nuts, coarse thread
for the threaded rod
24 5/8 in. (1.5875 cm.) washers
again for the threaded rod
10 1/4 in. (0.635 cm) diameter, 5.5 in. (15.24 cm.) long carriage bolts
For the arm assembly
6 1/4 in. (0.635 cm) bolts, matching thread
for the carriage bolts
6 1/4 in. (0.635 cm) washers, matching carriage bolts
for the carriage bolts
3/8” X 4” eye bolt (Including bolts)
8 matching cut washers
these will be used in the trigger
2 1/2” X 10” eye bolts
these are the trigger pins
Wheels, weights
3 3 in. X 1.5 in. (7.62 X 3.81 cm) diameter wheels, 5/8 id bearing load rating of 200 lbs (90.71 kilos) or more
May need to be hanged if the diameter of the threaded rod is changed
excellent site for cheap, strong wheels http://www.thecasterguy.com/
2 hand weights, 10 lbs (4.54 kilos)*
2 hand weights, 8 lbs (3.63 kilos)*
*must be able to fit inside counterweight boxes
Sling
Approx. 50 ft. (15.34 m) of 3/16” (0.47625 cm) braided polyester cord
The sling lines, I bough 50 ft because i needed to cut the right lengths for each ratio, you probably wont really need more than 15 ft.
Approx 25 ft. (7.62 m)1/2” braided nylon rope
(This is actually for the trigger)
15 in. X 6.5 in (38.1 X 16.51 cm.) denim fabric
for the sling
Just find a pair of old jeans
Approx. 10 ft. (3.048 m ) of gorilla tape
for the sling
1 keychain ring
A solid metal ring of any kind would work better.
One thick nail.
This is the pin.
I don't know what gauge mine was, I found it in the trash Buy one that is at least 4 inches. The thicker the better to prevent it from bending. You should also cut off the head if you keep getting downward throws no matter how you adjust it.
If you want a better pin system, look at the turnbuckle pin system here.
(third picture on the right) RLT industries trebuchet.com
Tools
erm...
common tools
hacksaw if you don't have a METAL CUTTING BLADE FOR YOUR JIGSAW,
jigsaw the one I used here
circular saw (The one I used here) OR miter saw AND table saw
you need to miter, rip, and crosscut.
drill (The one I used here came in a kit here) with a varied drill bit set, for pilot holes, etc. One drill bit MUST be the size of your threaded rod (Mine was 5/8", it should be thicker) Ideally, the drill bit would be a foot long, or 6 inches, so that the holes in the arm don't become misaligned. I'll explain later...
also screwdriver bit driving in your screws.
coping saw and orbital sander (The one I used here)
Socket wrench for your threaded rod
speed square
...I'm kinda adding these as I think of them..
Tape measure, ruler
rubber mallet
claw hammer
um..
I think that's it
OK onto step 1
the base...
the beginning...
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Now, to attach it:
Imagine the pouch itself. It has two ropes coming off it, one in either direction.
-----------(pouch)-----------
One end is tied through a hole that's drilled in the end of the arm. You do not want this side to come undone, so make sure it's tied tightly to the end of the arm however you can.
The second length of rope is tied to a small ring- like a loose keychain ring.
On the end of the arm, there will also be a nail, or some sort of strong metal pin. This metal loop goes around the pin, and as the centrifugal force increases as the arm swings, the ring slides off the pin to allow the pouch to open.
so its looks like this... if you can use some imagination :P
and if it doesnt get messed up once i post this
(======arm=======--)(----------rope------------)(sling)(----------rope------------)0
^that's the pin tied to sling ring tied to end of rope^
I realize that wasn't an awesome explanation, let me know if you still don't get it.
And send me some pictures :D
How much will this cost?
And, I'm not looking to chuck this 200yds. I will be launching this in a range 200yds and I'm looking to toss under that because I will be demonstrating my trebuchet about 50yds or so from a football field and I will be tossing the weight towards the field and at the other end is a parking lot. So if I could toss the weight a 100yds would be perfect.
If you need to beef things up, like the counterweight bolt and wheels, it might cost more. But make sure you go to the website for wheels that I recommended in the Instructable to avoid paying too much for wheels.
And as for tossing a weight that far, you would need to change the ratios on the arm yourself and work with different sling lengths. If you could find a simulator that would be great, but I never could. It takes awhile to calibrate the different lengths and ratios to reach optimal firing capabilities.
Can the trebuchet launch a 2-lb dumbell?
Can the trebuchet launch a 6-lb shot?
If I need to bring the scale down, what would the dimensions be?
The main problems would be the extra weight needed to really make the 6 pound weight fly, which would put extra strain on the wheels on the arm and the bolt holding them, the counterweight bolt, the counterweight boxes, the sling, the sling lines and the trigger assembly. Oh, and the arm itself. I haven't noticed any cracking with a 1 pound weight being fired at full speed, but a 6 lb weight will exert much more force on the arm because of its higher inertia..
Essentially, beef up the arm assembly. And do lots of testing, with a realllllly long trigger string.
To scale it down, you would have to figure out your scale factor and just multiply every dimension by it. Alternatively, you could download the sketchup model, highlight the entire thing, scale it down and get the dimensions directly from there.
Although the trebuchet will work so small, it might be better to increase the arm ration. Give it more of a flicking action than a long drawn out flinging.
I don't really know what I'm talking about.
Do some experiments, that part is the most fun.
Here is a floating arm that two other students and I from FRC team 11 MORT designed for punkin chunkin in Delaware. As far as we know, its the largest floating arm ever built by youths, and the largest wooden floating arm trebuchet in existance.
The arm is 18 feet long, we use a 1.5 inch steel bar, and can load it up to about 800 pounds.
http://mort11.org/pumpkin
also be sure to check out the rest of our website, FIRST is a great program for anyone interested in engineering!
I only figured it out after i screwed everything together..
I actually didn't draw up ANYTHING for this before I started (BAD idea)
and realized that the short arm was...too short.
I'm a very lazy person, so I just let it be.
Eventually , I WILL fix it; it's just that I have no time over the weekdays and have limited time over the weekends (I wake up really late- like a sloth).
...Anyway...
I'll either make the short arm longer or just lower the tracks like you suggested...
still pondering. If you have ANY better ideas, let me know.
I revere you.
The program you're in looks AMAZING!
and, of course, the trebuchet does, too...
In fact, it was trebuchet like this yours that inspired me to make a trebuchet for my science project.
AND I had seen the MORT treb before this (on youtube). You guys really get around, huh?
Now, i have a few questions for you, mr gills, sir man.
WAS the steel bar hardened?
DID it bend at all?
and last ut not least...
HOW long did it take you to make?
...that's it.
GOOD LUCK in the punkin chunkin contest...I'll be watching it on Discovery.
-nico
Sadly no, our steel bar was not hardened. We did special order it and it was very high grade steel so it did not bend for a while, but yes it bent after our 800 pound throw. To send it out to get heat hardened would have taken about two weeks that we needed for practice throws.
If you include planning, we started in August, and started actually build in September. And we were done by November 3 for Delaware, which already passed. The TV people need about a month to edit and such.
We had a few problems such as throwing at the wrong angle and having friction on our bar that kept us from winning. We came in third to a smaller floating arm trebuchet.
And last but certainly not least, yes, FIRST is a great program and I can say with confidence that it is the best thing i have done with my life thus far. Im sure there is something in the terms and conditions about not asking where you live so i cant say which teams are near you but yo should be able to check here and maybe start a team of your own. Its hard work but you wont regret it.
http://www.usfirst.org/roboticsprograms/frc
That means a 1 inch bar should be fine for me...
My trebuchet almost always fired at the wrong angle because the pin I used was a double-headed nail. The ridges were large, and caught on the ring.
Usually, it would throw the ball straight down.
I also had the same problem with friction. A lot of the time it would actually stop halfway down. If one side was rubbing more than the other, the bar would tilt and pull the channels together. Luckily, nothing ever broke.
Third is impressive. For a NATIONAL competition. And I'm sure you'll be better next year.
Also, I live in Coral Gables (near miami).
Yup, that's a ways away from you.
I'm in SECME, which is just..ehhh...
It's O.K...not great. It's more doing than learning and doing. (No knowledgable counselors, etc.)
I'll look into starting or joining a team.
-nico
ANYWAY
I do think this design would be capable of throwing a 5 lb pumpkin 200 yards. The drop towers should be made stronger, because the CW weight needed to throw a projectile weighing 5lbs a distance of 200 yds is going to be a lot. Right now, I'm making the towers stronger and lengthening the arm... although I haven't been working too diligently on that.
The arm would also have to be strengthened, as it may break with such a high load. (Maybe, I'm not sure) Rectangular aluminum tubing might work better than wood, but i can't vouch for that so don't take my word for it. It could be something to try, considering a hollow aluminum tube may also be lighter.
The sling lines would have to made of thicker rope and a better design for the pouch would have to be created.
as for the distance of 200 yards...if you optimize the CW/ projectile weight ratio and the short arm/long arm/sling length ratio, you may be able to throw a pumpkin 200 yards.
My design is by no means optimal, so I would recommend using it as a design template and not strict dimensions, especially for the arm and sling.
Other than that, you WILL need a thicker CW bolt. Depending on what weight you use, I would recommend something at least 1 1/4" to be on the safe side. (Just in case, that might be overkill. If anything, it will add weight to the CW.)
Reinforce the bolt holes, too.
If you have any other questions please ask me.
The total length of the arm with the extension was about 9 ft, 1 inch.
I would recommend using this full length, but make sure that the arm will be strong enough and light enough. The longer it is, the more important it is that the tip be light. If the rm is longer, the forces on it will also be larger.
For the arm assembly, I don't think the carriage bolts need to be necessarily thicker, as the object of them is to spread out the force over a larger area. If you make the short arm longer, just use more carriage bolts. Most of the force is taken by the plywood and 2X4s, so the shear force should be small. If you really want to be sure, just use more than you think you need. (Maybe 1/2"?) If anything, they'll add more weight.
Now, I'm pretty sure you're not talking about the counterweight bolt, but if you are, make yours VERY THICK
It should be hardened steel along the lines of 2 1/2" thick
Remember, some parts of the structure will probably have to be reinforced. (Especially the trigger system)
If you have any other questions please ask me.
good luck
there are many factors which influence the success of each launch.
on this one, the pin was a nail with two heads. These ridges would catch on the ring, causing downward throws.
Or, the arm would hit the guide blocks on its way down, right before the wheels on the arm contacted the track. this made it throw backwards.
this trebuchet launched a baseball only 206 feet.
The trajectory, however, was way too steep (we had no idea where the baseball was until it came down) and the arm was too short.
It does work well and it can launch farther than 200 feet (probably around 400 with a lower trajectory) but it requires tweaking.
please comment if you need help.
hopefully you'll build it.
with a smaller treb, you need to make sure the arm is extremely light so it can move quickly.
let me know how it goes!
I'm on vacation right now (had no Internet for the past week, sorry it took me so long to respond to your comment) and I don't have access to the file. I might be able to get it in about a week from now. When do you need the plans?
If you need them before sunday, reply and. CN try getting them to you before then.
Best of luck in your contest!
if you have an email i can email it directly to you, unless you know by any chance how to post the sketchup file on the instructable.
otherwise, send your email address to my inbox. Don't put in in a comment or you might get spammed.
I'm not exactly sure why, but i havent been able to fix it.
There may be a few small errors in the sketchup version but they should be small, if any. It's been a little while since i last looked at it.
Thanks
wow...
If you're going to use this design, i would recommend being very careful with that weight...
Especially with the trigger...
I only used 50-60 ish pounds and the trebuchet has held up 100% ok...
No structural cracks or warping-
Remember, since the trigger is screwed directly onto the drop channels, you may need to thicken or reinforce the area where the eye bolts screw in--
Gradually add weight and test fire it several times with each weight.If you see anything go wrong, back off a bit.
Just be careful with that weight, check it after every fire.
Other than the trigger, the weakest part of the trebuchet is the CW bolt and axle.
-They need to be thickened if you're going to use 200 pounds.
One other guy (Gooches vfd) said the bottom of the drop channels cracked. Although it hasn't happened to me, add some reinforcement there too.
I got an A on my school project. With this, it's hard to go wrong.
Remember to add reinforcement, just in case.
PM me or comment if you need any help at all.
Good luck !
I'm sure I ask more than you.
well, it'll take a bit of time to fully explain.
Essentially, when you have a higher arm ratio, the short arm (the side with the counterweight) is much shorter than the long arm. (The side that the sling attaches to.)
So, we can think about the arm as a lever or a seesaw. When the short arm is much shorter than the long arm, a small movement on the short arm will be amplified on the long arm side. This effect is amplified as the ratio increases. Remember, as the ratio increases, the short arm gets shorter in comparison to the long arm.
So, a higher arm ratio will whip the arm faster, but more weight will be required becuase of the higher ratio.
Let's say we have a 2 to 1 ratio and a 3 to 1 ratio.
The 2 to 1 ratio means that the length of the short arm doubled (2) is the length of the long arm. (1)
A 3 to 1 ratio will have a short arm that is 1/3 the length of the long arm.
The wheel placement is what decides the ratio. The closer to the counterweight, the higher the ratio. The farther away from the counterweight, the lower the ratio.
A lower ratio requires less weight and can fling heavy objects better.
A higher ratio requires a bit more weight to fling something, but when it does the tip of the arm will move faster.
However, when the counterweight itself moves at the same speed in both ratios, the higher ratio will move the arm faster, but may require more weight to do so.
Remember, the ratio is decided by the wheel placement.
Experiment with different holes until you get the best distance for your payload and counterweight.
Hopefully that answers your question.
Please keep commenting- I like comments...
Let me know if you need more help!
Basically, the capacity matters more than the wheel size, but make sure the wheel size is right so that the arm rolls as smoothly as possible.
This website is a great one; it's where i bought my wheels: http://www.mandmsupplycasters.com/
My wheels can support 600 pounds if i remember correctly.
They have bearings, along with an adapter tube for the diameter of the bolt you will screw them on to.
And the best part is that each one was only 4$
that's dirt cheap for a wheel with bearings.
I would recommend getting around 5 inch-ish wheels and maybe 900 lb capacity with your weight, just to be safe.
my wheels are made of phenolic.
Remember: capacity is more important than size.
Get wheels rated way above your weight. A falling 200lb mass will exert more force on the wheels than 200 pounds, because of the speed the weight is moving at. The inertia and stuff...
good luck
how?
oohhhhh wait...
I forgot to write about the guide cute.
Wow. I feel really stupid. (Well now I have to add that)
anyway....
I'm glad to hear someone actually built this!
How tall was it?
How did you do in the contests?
The 2 X 4 drop channel cracking...well thanks for mentioning that. Luckily it hasn't happened to me. If you want to simply repair it, you could probably just glue it back together and add a reinforcing bit of wood across it.
Hmm...now I have to go check my trebuchet for cracks...
Also, if you could post pictures, that would be great!
i'd love to see what you've done
Thanks
(Sorry for the long reply)
especially if you didn't have many practice shots..
Ours should have gone farther, but the trajectory was too steep, the long arm too heavy and short.
The arm needs improvement.
Good luck in any future contests!