PLC controlled spud-gun

boneless
When I was a young teen looking for trouble we poured a large can of carbide into a creek that led onto a culvert. After a minute we threw a match into it and it produced the appropriate noise. What we failed to think about was what was on the other end of the culvert.
The people sitting on the crowded beach were not impressed with the amount of mud that we cleaned out of that culvert.
 
So, I realized today that I didn’t update this post. It’s been over a year since I first posted anything about my spud gun and while it worked “ok” at Summer Solstice I did have some problems with getting the correct fuel load. With the first version of the gun the fuel was loaded through the breach which involved holding a propane nozzle over the open breach for a timed amount and then installing the breach. The problem turned out to be with as windy as it gets in Ellensburg when I would be loading the fuel with amount and temperature of the air going in with it was changing. This led to a lot of misfires. So, this year (2018) I redesigned the gun with a bigger combustion chamber (you can’t go with the same bang as last year! It has to get bigger) and a fuel injection system that allowed me to pipe the propane in with the potato loaded and the breach closed. The meant that the air in the chamber for each fuel load was much more consistent. After each shot I would pull the breach and use a fan (an old hair drier running off 12VDC) to clear the exhaust out and load fresh air in. This time I only got about a 5% misfire average and a much louder shot. The video is at my father in-laws on the 4th of July when no one will notice the noise of the gun going off. I did do a rough measurement for fps and it comes out at around 128fps which is just under 90 mph. I must confess though, I took the PLC out of the equation this time and went with just an oscillating relay which was always there, it was just controlled by the PLC in the first version.
https://www.youtube.com/watch?v=Y1JnlnuqLxE

https://www.youtube.com/watch?v=tlxyf0KrPSI
 
Very nice (y)

I just realized what new toy I need :)

Most of the time when I create something, the actual design and build is a majority of the fun. This time, firing it is still second but a very close second. The only problem I have is I can't use it at home. When I was testing it (at home) I could only take one or two shots before I'd have to put it away so that when the cops would roll through the neighborhood they wouldn't see that it was me. The video's don't do a good job of showing just how loud it is.
 
A side story,
When I was at my father in-law's this year (where the last two videos were taken) the neighbor came home with one of his two 8 year old boys (he has twins). They came over to the fence line to watch and I invited them over. With all of the other fireworks going off (LOTS of aerial "big boom" stuff in this neighborhood) the 8 year old (and the dad as well) were fixated on my spud gun. I asked the 8 year old if he wanted to fire it and he just about passed out with excitement. I loaded the gun and handed him the trigger box (which is at the end of a 20' extension cord) and we did a count down. The shot he took was one of the louder one and the look on his face was priceless. They watched for a few more shots and then Mom arrived with the other son. His brother (who had just fired the gun) went running over to him and inside of two seconds explained the whole story to Mon and his brother, four times. They came over and of course I offered to let the other 8 year old take a shot as well which he did and he also had a priceless look after the shot. The grownups (and I) chatted for a few minutes and then they (Mom and Dad) thanks us and took the boys home and shortly after back out to wherever they were going for the fourth.
That made not only my fourth but most of my year and was/is the absolute best part of making this thing. I'm convinced that 5 to 10 years from now those two boys will be in their garage figuring out how to build a potato gun like the one they got to fire that year and hopefully I'll be around to give them some pointers.
To put a PLC spin on this (and justify it being on this site) While we were chatting Dad asked how I came up with some of the equipment I was using (a pilot light on the trigger box to indicate it was live, an industrial button for the actual trigger, etc...) and explained what I do and a little bit about the automation industry. Hopefully some of that rubbed off on the boys and they will have an interest as they get older in the industry.
 
Not the same but the videos reminded me when I was a kid we would build a fire in a 55gal drum put a 3 inch pipe in the fire about 6 foot long and have it leaning just a bit... drop a spray paint can down the pipe, you would have about 60 to 90 sec before the can would get hot enough to blow... man the stupid **** we did when we were kids, it did shoot a 20 foot flame
 
When I was “younger” I saw a tennis ball cannon that had a 4’ piece of pipe with legs holding one end up off the ground about a foot. That end was also pinched so that the tennis ball couldn’t fit through it. Underneath this an M-80 was lit sending the tennis ball flying. However, I decided that it was very inefficient, so I set out to improve the design. I worked at a muffler shop and I took an 18” piece of 2.5” pipe, opened one end up so that a tennis ball would fit snuggly in it, welded legs on the other end and made a plug-in breach that would hold the M-80. The breach was sealed with a large rubber O-ring, held in with a pin and had a small hole for the fuse. In short nearly all the explosive force from the M-80 went up and out where the tennis ball was. The first time I fired it I was at my old elementary school’s open field and I thought the tennis ball disintegrated because long after the thing went off there was no sign of it. However, a little over 15 seconds later the tennis ball finally came back down. I was planning on making a golf ball version knowing that golf balls store much more energy than a tennis ball does and it’s much more aerodynamic, so it should travel much further. But first, we decided to see what would happen if we tilted the cannon on its side and pointed it at the brick wall of the school. Ok, side note, I was younger and a lot dumber back then. The field was 50 yards wide, we were at the center with the cannon pointed at the wall (25 yards away). In the opposite direction was an undeveloped property with a bunch of trees. When the shot went off we could hear the tennis ball ricocheting off the trees across the street which means the tennis ball travelled approximately 85 yards in less than a second (or over 170mph) and when we went and looked at the brick wall there was a 3” wide 1” deep divot in it. At that moment I decided that I didn’t want to accidently shoot down an airplane, so the golf ball version was out.
Yes, the stupid **** we did, I’m lucky to still be here.
P.S. My rough math (and I mean very rough math) tells me that the Tennis ball went as high as 1000’
 

Similar Topics

My boss has come up with the idea of renting machines and charging on a per use / per hour basis, so I'm looking into it - just getting my feet...
Replies
14
Views
3,913
I have an emco lathe I have retrofitted for a new control (mach4) and electronics. I have saved this turret for last because I knew it was going...
Replies
77
Views
29,857
Need help with designing and test a PLC-controlled pneumatic system that conveys manufactured parts and loads them on a packing machine. I am...
Replies
8
Views
2,592
Hi all! I can't seem to figure out what I'm doing wrong. I have wired up my stepper motor, control, and uploaded test programs and nothing...
Replies
2
Views
1,841
Imagine, if you will, a series of custom built modules (building size). Each module is setup with standardized control/automation equipment...
Replies
12
Views
5,583
Back
Top Bottom