I figured I would start a new thread about my project. The previous one was too specific (Solenoid, How Much Force).

Don't scold me about wasting money and time on this project. I know it's way out there. But hey, I'm retired so I can waste as much time as I want.

I'm working on a cannon that will lure a mouse down the barrel, then fire him across the room, hitting a wall and then falling into a bucket. I've already designed and built one that won't work. It's powered by a 6" spring (52 lbs at 4" compression) and a motor/gearbox for a wench to get the thing pulled back and cocked. Only I can't find the right spring (the one I bought was too strong) and the winding mechanism has got the best of me. This one, when pulled back about 3" will propel a 0.6oz weight 27 feet. Since I've come to a dead end on that one I've put it on the shelf for now and have undertaken a new design using magnetics. Here's a 3D of the spring cannon:


And what's been built (most parts with a 3D printer):


Now I plan to make a linear solenoid with a stroke around 4" in length. The solenoid will push a piston inside the barrel which launches the mouse. A weak spring or rubber band will return the piston to it's initial position after firing. The trigger is a baited wire on the inside of the barrel that when disturbed, touches another wire which instantly charges a small capacitor across the gate/source of a power MOSFET. The cap will keep the FET on until the piston has completed its movement. Initially I plan to power this with a 9v battery charging a 22,000uF capacitor. My gut feel is that 22,000uF discharging thru 15 ohms of coil will generate enough power to propel the mouse (0.6oz) against a wall about 10' away. The cap is rated at 25v so if needed I can always go up in voltage. The armature of the coil will be a 3" x .5" (dia) neodymium magnet inside a thin wall PVC pipe; the coil will be 4" long, wound around the pipe. I calculated 1600 total turns in 11 layers of 22 ga magnet wire. I'm thinking I may want to enclose the coil (and armature) in an iron pipe with caps on each end and a hole drilled into one end for the armature-to-piston shaft. That should enhance the magnetic circuit from coil to armature. Or would it?

Comments/suggestions/ideas are welcomed. I don't want to have to undertake a 3rd design. Let's make this work!

 

 

A "ratapult"?

 

I think it will just go "clunk."

 

I think it will just go "clunk."

What the plural of "it?" I am surprised his first thread is still around.

 

Hallo,

I think you might know the user agreement by now.
In there the following information is given :

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1. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:
   
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Bertus