Why in the world are we doing this?
Google Image Like most things it is no longer clear who came up with the idea. Sally and I will just share the blame.
It was late September and time to start thinking of what we were going to do for Christmas for the kids. For the past couple years Sally has crocheted something and she decided it was time for me to go to work for a change. We are a blended family with Grandkids all over the place. We had 25 (including grands and great-grands) last time we took an inventory. Some samples of birthday and Christmas presents can be found here:
http://www.grangerlandrfd.com/birthday-dilemma
She told me that it was well established that I could drive the car to Hobby Lobby for her to pick up yarn. I also had done a pretty good job of sitting on the computer while she crocheted. Other than that she didn’t think I had been pulling my share of the load. Much as I would have liked to I couldn't refute that charge.
Once upon a time I knew how to do a lot of things with wood; I had even taught a shop class. Some time has passed since then so if I was going to be the guilty party it needed to be something simple. When going through some ideas we came across some desktop trebuchets.
It was late September and time to start thinking of what we were going to do for Christmas for the kids. For the past couple years Sally has crocheted something and she decided it was time for me to go to work for a change. We are a blended family with Grandkids all over the place. We had 25 (including grands and great-grands) last time we took an inventory. Some samples of birthday and Christmas presents can be found here:
http://www.grangerlandrfd.com/birthday-dilemma
She told me that it was well established that I could drive the car to Hobby Lobby for her to pick up yarn. I also had done a pretty good job of sitting on the computer while she crocheted. Other than that she didn’t think I had been pulling my share of the load. Much as I would have liked to I couldn't refute that charge.
Once upon a time I knew how to do a lot of things with wood; I had even taught a shop class. Some time has passed since then so if I was going to be the guilty party it needed to be something simple. When going through some ideas we came across some desktop trebuchets.
Google Image Well actually, I came across them. When I showed her the pictures she let out a whoop (ladylike and subdued) and shouted “that’s it”. We (she) decided then and there that it would be really neat to have some competition among those branches of the family with kids (and parents) that were the right age.
Now I cannot say for sure that this trebuchet firing an old VW isn’t staged. I can say that it has happened. Google trebuchet on you tube and you can see a number of things being hurled. Better yet, just go here:
https://www.youtube.com/watch?v=CyCJ69GU974
The original trebuchets were siege machines and hurled heavy boulders, flaming stuff or maybe even dead livestock through or over castle walls. They were something you just did not want to see outside the wall if you were setting in a castle somewhere. They were too big to come down the road. These castle busters were built on site. The wheels were there just to compensate for the energy loss from the swinging movement when the weight dropped. Wheels make your trebuchet work better.
We definitely needed to come up with something simpler and smaller if we expected anyone to actually take one home. We also wanted to have some money left in the bank account after we finished building them. We started out thinking we would build something that would fit on a desktop. That turned out to be a good idea if we wanted to shoot marshmallows. Not much else.
Now I cannot say for sure that this trebuchet firing an old VW isn’t staged. I can say that it has happened. Google trebuchet on you tube and you can see a number of things being hurled. Better yet, just go here:
https://www.youtube.com/watch?v=CyCJ69GU974
The original trebuchets were siege machines and hurled heavy boulders, flaming stuff or maybe even dead livestock through or over castle walls. They were something you just did not want to see outside the wall if you were setting in a castle somewhere. They were too big to come down the road. These castle busters were built on site. The wheels were there just to compensate for the energy loss from the swinging movement when the weight dropped. Wheels make your trebuchet work better.
We definitely needed to come up with something simpler and smaller if we expected anyone to actually take one home. We also wanted to have some money left in the bank account after we finished building them. We started out thinking we would build something that would fit on a desktop. That turned out to be a good idea if we wanted to shoot marshmallows. Not much else.
Terminology and Science
This was more like it but still too big. It’s plenty ugly which is something I always like. However, the base here looks very big and I didn't want to buy a bunch of dumbell weights. There are a bunch of variables. We went out looking for the ideal projectile and built around that. The projectile dictates the specs.
Making trebuchets looks simple. I guess if you just copy someone’s work, it is. I assure you I have already done more math than I normally do in a month. I was hoping for something big enough to be fun and small enough to take home and store indoors. That may be what we accomplished. Depends on how much room you have indoors. I once built one in a classroom at New Caney High School. We mounted it on a trailer and fired it in the parking lot. Later on I fried my hard drive and lost the evidence, but I didn’t want that again anyway.
Making trebuchets looks simple. I guess if you just copy someone’s work, it is. I assure you I have already done more math than I normally do in a month. I was hoping for something big enough to be fun and small enough to take home and store indoors. That may be what we accomplished. Depends on how much room you have indoors. I once built one in a classroom at New Caney High School. We mounted it on a trailer and fired it in the parking lot. Later on I fried my hard drive and lost the evidence, but I didn’t want that again anyway.
Google image of penguinslab.com web site I guess it would help to get some terms down about now. For the immediate future the long arm that heaves the load is called the throwing arm. For the most part that term will be used to describe the arm to the right of the fulcrum (or center point). The weight that pulls the left side down is called the counterweight. If you want to look into this deeper, the website is obvious here on this screen shot. It was a very good site with a lot more information. It recommended a counterweight ratio of not less than 133:1. How much does stuff weigh?
The project actually started by settling on a projectile. An important consideration here is what will upset parents. A kid may be happy with something that will throw a Volkswagen but if mama isn't happy, nobody is. If the kid hurls a rock and breaks a vase from Mama's favorite aunt, I see storm clouds in your immediate future.
This is a youth practice tennis ball from Academy. It is under inflated and in my opinion basically worthless for anything but teaching kids to play tennis. We picked up a bag of them that are apparently identical and will work fine for Christmas day. A golf ball would be a much better projectile. It is about the same weight (I think) but with much less wind resistance. We designed the trebuchets around the safer of the two.
This is a youth practice tennis ball from Academy. It is under inflated and in my opinion basically worthless for anything but teaching kids to play tennis. We picked up a bag of them that are apparently identical and will work fine for Christmas day. A golf ball would be a much better projectile. It is about the same weight (I think) but with much less wind resistance. We designed the trebuchets around the safer of the two.
We used our food scale for measuring the projectile. Since this is dry, I am going to round up the math and use 2 ounces as a working weight.
To determine the counterweight requirement: 2 oz multiplied by 133 equals 266 ounces. Divided by 16 one gets 16.625 lbs. Well, what’s compact and weighs 16.625 pounds. I really didn't know but thought I would see what a brick weighed.
To determine the counterweight requirement: 2 oz multiplied by 133 equals 266 ounces. Divided by 16 one gets 16.625 lbs. Well, what’s compact and weighs 16.625 pounds. I really didn't know but thought I would see what a brick weighed.
Pre-production work.
This is a leap of blind (and mis-assigned) faith. It did fit and that was good.
How much does a brick weigh. If you put it on a digital bathroom scale it won’t actually read. If you weigh yourself and then repeat the process holding the brick, it seems to weigh just over six pounds.
I put this contraption together to do test runs with various weights but I actually should have run them through the calculator before I butchered any wood. After all an 18-wheeler won't do much with a Briggs and Stratton lawnmower engine.
Google is your friend. Lets look at concrete.
How much does a brick weigh. If you put it on a digital bathroom scale it won’t actually read. If you weigh yourself and then repeat the process holding the brick, it seems to weigh just over six pounds.
I put this contraption together to do test runs with various weights but I actually should have run them through the calculator before I butchered any wood. After all an 18-wheeler won't do much with a Briggs and Stratton lawnmower engine.
Google is your friend. Lets look at concrete.
This container was the first thing I thought of for the concrete. I suppose I could have exercised my duct tape mastery and combined two of them.
It’s a big hassle doing the concrete for just one at a time. I started looking for something that would let me mass produce.
I ran across this pipe at McCoy’s in Cleveland (TX). I cut off this 18” length to see if it would fit in the machine. It has a 4" diameter and according to sources on Google, a 12” x 4” pipe will hold 12.9 lbs of concrete. Actually it says concrete weighs 150 lbs per cubic foot and I did the math.
What will fit? Since I can also add weight to the thick end of the throwing arm if I am wrong, I am going to go ahead and make some 16” weights.
According to my calculator that should be just over 17 lbs. The rebar used for hooks makes it just a little more. Should work.
What will fit? Since I can also add weight to the thick end of the throwing arm if I am wrong, I am going to go ahead and make some 16” weights.
According to my calculator that should be just over 17 lbs. The rebar used for hooks makes it just a little more. Should work.
Panic time as forty pounds of concrete filled 4 pipes. I have to think that it weighs more when constituted. There is also the weight of the pipe (not much) and steel rebar which apparently is three times the weight of concrete.
If this isn't big enough I just may go back to the drawing board for projectiles. This gives me five. Original plans were for the first one to be used as the development model but Mama soon said we needed five gifts. It will all work.
If this isn't big enough I just may go back to the drawing board for projectiles. This gives me five. Original plans were for the first one to be used as the development model but Mama soon said we needed five gifts. It will all work.
On the right is the first attempt to build a frame. It's wide enough to hold the 16" weight but flimsy and too short. Thats a landscape timber nail that I have for an axle.
The upright on the left is made from treated 2x4. I had a couple problems. The 2x4 tried to burn up my table saw when I tapered it. I don’t know if it is because the saw was purchased about 1998 or because the blade (original) was dull. Those facts could be related. I wanted to taper it because it looks better. I had 3" at the bottom and one 1" at the top.
There is also the problem that I set the two uprights far enough apart that the axle was suddenly too short. No problem. We'll come up with something else.
You can see an early iteration of the throwing arm in the background. The ratio of the fat part which holds the counterweight and the skinny part that whips the projectile is recommended at between 5:1 and 4:1. The cord that holds the projectile should be about 80% the length of the throwing arm.
The upright on the left is made from treated 2x4. I had a couple problems. The 2x4 tried to burn up my table saw when I tapered it. I don’t know if it is because the saw was purchased about 1998 or because the blade (original) was dull. Those facts could be related. I wanted to taper it because it looks better. I had 3" at the bottom and one 1" at the top.
There is also the problem that I set the two uprights far enough apart that the axle was suddenly too short. No problem. We'll come up with something else.
You can see an early iteration of the throwing arm in the background. The ratio of the fat part which holds the counterweight and the skinny part that whips the projectile is recommended at between 5:1 and 4:1. The cord that holds the projectile should be about 80% the length of the throwing arm.
This is how you tell that someone has been using Gorilla Glue. It will not come off with soap and water. WD40 is pretty much wasted also. Wear it off or use sandpaper are the only solutions I have found. Gorilla Glue and staples would probably hold your house or car together.
This is the first sling. I made it just to check the ratios and the working model wound up performing pretty well. This design had the additional advantage that it could be salvaged and all the pieces used again.
I have some larger pieces of sheet leather for the gifts. With four cord connections in a diaper carry (parents understand this). I think we will have some good slings that, unfortunately, look far less rednecked.
I thought the sling was the most important part but found that it isn't. The pin on the end of the throwing arm changes the projectile arc from grounder, to line drive, to fly ball, to pop fly. Fine tuning with a pair of pliers seems to be all it takes.
I have some larger pieces of sheet leather for the gifts. With four cord connections in a diaper carry (parents understand this). I think we will have some good slings that, unfortunately, look far less rednecked.
I thought the sling was the most important part but found that it isn't. The pin on the end of the throwing arm changes the projectile arc from grounder, to line drive, to fly ball, to pop fly. Fine tuning with a pair of pliers seems to be all it takes.
This is the final design for the slinging (hurling) arm. The weight on the projectile end is only about 3-4 ounces including the sling. This 1X2 arm is plenty strong enough for that. This butt end is secured with Gorilla Glue and staples.
The axle is 1/2" electrical conduit. It gives me a lot of flexibility on the width of the unit. When you stick the axle through the uprights a single sheetrock screw on each side keeps it from rotating. Spacers hold the swing arm in place. The conduit is plenty strong enough to hold the arm and weight. if it gets used a lot and eventually bends, it can be easily replaced.
This is called a spade bit or a paddle bit because of it’s resemblance to either of them.
If you use 1/2" electrical conduit you need a 3/4" bit. The half inch is an internal dimension and the conduit won't fit in a half inch hole. If this seems obvious I can only say that you're smarter than me..
If you use 1/2" electrical conduit you need a 3/4" bit. The half inch is an internal dimension and the conduit won't fit in a half inch hole. If this seems obvious I can only say that you're smarter than me..
Production
This is what we finally came to for a frame. We did not use furniture grade wood and I think anyone that would has forgotten what they are trying to make.
The base came from a fence board that has been around for a while. There is nothing special about the 2x4s except the price. I loved the price.
The white stuff all over them is spackling compound. I used it to fill in the holes before I gave them a rough sanding. We wound up making five because we had five sons and daughters that we thought would be here at christmas with the appropriate age grandchildren. They are not quite identical. I thought we had the answer to everything when I did the first one. Then I realized that a couple of the families might well be throwing seashells or whatever. Four of them are just a little wider and two of them required the addition of S hooks because of the way I cast the weights.
The base came from a fence board that has been around for a while. There is nothing special about the 2x4s except the price. I loved the price.
The white stuff all over them is spackling compound. I used it to fill in the holes before I gave them a rough sanding. We wound up making five because we had five sons and daughters that we thought would be here at christmas with the appropriate age grandchildren. They are not quite identical. I thought we had the answer to everything when I did the first one. Then I realized that a couple of the families might well be throwing seashells or whatever. Four of them are just a little wider and two of them required the addition of S hooks because of the way I cast the weights.
There was some discussion on what colors to use. We decided on camouflage and this is the base green. I know it's ugly but there was no attempt at all to look good. The green lurks in the background when you camouflage.
This shot also shows the construction of the weight end of the throwing arm.
I bought this before I retired. If I remember right it cost me $100. That's a pretty good price for a small welder I thought. Then the welding teacher at the high school had problems making it work.
I went for a while thinking I had been stupid. Then I started reading and figured how welding electrodes were sized. I think the welding teacher just never worked with anything that small. Makes a lot of difference and it sure got a workout on this project.
This is the S hook that I mentioned earlier in the post. I used it because the rebar was cast crooked in the concrete. It turned the weight 90 degrees and kept the weight from hitting the uprights. It turned out to not be quite up to the job and spread when the weight was dropped.
I squeezed it back together and welded it. This rebar was a little bit bigger than some so I needed filler before I welded the bottom one. I stuck a nail in the gap and welded it.
I squeezed it back together and welded it. This rebar was a little bit bigger than some so I needed filler before I welded the bottom one. I stuck a nail in the gap and welded it.
I have had these channel lock pliers for about 20 years. When I bought them I could have closed the S hook with little effort. In the ensuing years I am afraid the pliers have become weaker. Now I need cheater bars for some things.
Luckily there is normally a collection of junk suitable for use as cheater bars laying around in my scrap heap. Leverage or mechanical advantage is good.
Luckily there is normally a collection of junk suitable for use as cheater bars laying around in my scrap heap. Leverage or mechanical advantage is good.
Nothing but the latest technology. This is the latest in firing pin benders.
 You may think these are just big nails. I prefer to think of them as the first step in the release pin of a trebuchet. Cutting the slices out of them makes it easier to bend without breaking. Obviously there is a welder in their future.  This is what we will start with when making the ring that the nail slips through. The same old S hook. |  These are going to become the sleeves that the release pins slide through.  These are the sleeves installed. Between the pin holders will be a small metal ring that is attached to the throwing arm. When the pin is pulled, the arm is released.  Next step in the production of release pins. |
 With the S hook cut in half and a nail for the base, I think this will work.  This is the complete (but unattached) trigger system. I think that if I were not so cheap I could have purchased most of this at Lowes. That probably wouldn't have been redneck enough for me. |  So far, so good. Now to cut them apart, and grind and paint them. Then they can hold the trigger pin.  It's functional as you see it here but I can't leave the twisted wire exposed. |
Tie a piece of leather to the pin. Yank it when you're ready to fire. Next project is to build 5 slings.
 Trebuchets need a sling to work. Ours started with a little bit of Hobby Lobby leather. |  And ended up with five things that looked like this.  Camouflage was the order of the day. Feed bags are a good start on a leaf stencil. |
 Duct tape stiffens it so it can be reused.  This was my pride and joy. Pink leaves for my granddaughters. That worked well until....... |  This allowed for some variety in the camouflage patterns.  ..... Mama decided that they looked better black. This is how they looked christmas day. We had been dodging wet humid (or rainy) weather and painted them on the porch on christmas eve. I think everyone had fun and I think there will be pictures on facebook soon. If so, I will add them. Merry christmas everyone. |
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