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by Moonbogg
Sat Jan 18, 2020 4:58 am
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Re: "In the world of spuds today"

JSR let me know if you want me to make you some drawings. It would be fun to help you with one of your projects. Not that you need it or anything, but it would still be fun. The main benefit is you can see the assembly before machining it to make sure nothing interferes and everything fits together ...
by Moonbogg
Wed Jan 22, 2020 1:48 am
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Describe the ultimate potato cannon

Describe what you feel would be the ultimate potato cannon. Bore size, pneumatic or combustion, power class, features such as spud cutting and breach loading, ease of use should be very important as well, etc etc. Consider all you have seen and learned from this hobby over the years and use your min...
by Moonbogg
Wed Mar 11, 2020 11:02 am
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Re: JSR's workshop chronicles

JSR, could it be an option to apply an abrasive polishing paste between the rough parts and work them back and forth, allowing them to polish themselves in a natural way? Just a thought. I'm sick with jealousy by the way. SICK! Not coronavirus sick, but still quit green with machine envy :mrgreen:
by Moonbogg
Wed Apr 22, 2020 6:50 pm
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Re: "In the world of spuds today"

I like that RGB switch and the fantastic barrel choice :D Nice website also. Enjoyed browsing it.
by Moonbogg
Tue May 26, 2020 2:27 am
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Re: Propane failing to ignite reliably.

I saw your other post. I see the oxygen bottle sitting there. I also see the igniter right next to the cannon with a short wire, meaning you have to be close to fire it. You are going to die. You can't use propane and oxygen in a PVC cannon. You are going to die or someone else is going to get mangl...
by Moonbogg
Thu May 28, 2020 7:08 pm
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Re: Propane failing to ignite reliably.

The first good combustion cannon that I built was powerful enough to make me crap my pants and it worked reliably. I made it out of ABS plastic pipe, but many use pressure rated PVC. The way I did it was I first researched the designs here and asked a bunch of questions. Take a look at over-under de...
by Moonbogg
Sun May 31, 2020 1:11 am
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Re: Extra powerful homemade weapon.

That thing is an absolute monster. It's amazing.
by Moonbogg
Sun May 31, 2020 12:17 am
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I bring you some cannon performance data

I wanted to get more data but I ran into issues with the chrony giving error codes and getting knocked over from high winds. I also ran out of limes that fit the barrels too early because I was embarrassed to go into the market with my calipers. Next time I will bring the damn calipers and they can ...
by Moonbogg
Tue Jun 02, 2020 6:28 pm
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Re: Calculations related to pneumatic cannon.

It seems that Bernoulli's equation is typically used with incompressible fluids such as water, or gases where a constant density can be maintained which allows Bernoulli's equation to remain valid and useful. How can Bernoulli's equation be useful for a compressed air system where the potential ener...
by Moonbogg
Fri Jun 05, 2020 3:12 pm
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Re: Question regarding fueling, fan, and ignition.

I'd install the propane inlet at the end of the chamber where there is double thickness from the coupling as shown below. http://www.burntlatke.com/lp.html I'd put the fan at the far end as shown below. http://www.burntlatke.com/jpg600/fan-frictionmounted.jpg As far as the ignition, I'd install that...
by Moonbogg
Tue Jun 09, 2020 2:30 pm
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Re: New to this all

Can't believe I missed this post. JSR (guy above) covered it all. Welcome to the forums and keep us posted.
by Moonbogg
Fri Jun 12, 2020 4:00 pm
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Re: Port size vs performance

Fantastic replies. Thanks for the interesting thought experiment, D_Hall. That gives me something to mentally chew on. I feel 1 3/8" is where it will probably end up for this one. An interesting thing I noticed is that giant (2 5/8" dia) potatoes break apart at 4X and I'm wondering if the 1" port is...
by Moonbogg
Fri Jun 12, 2020 10:22 pm
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Re: Short question topic

I don't know what the percentage is. I think It depends on the opening pressure of the piston. Since the work is being done with pressurized gas to open the piston, as soon as it opens all of that working gas suddenly goes to work on the projectile and sends it into orbit. So, it may seem as though ...
by Moonbogg
Sat Jun 13, 2020 9:39 pm
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Re: Short question topic

I wonder if the shape of the B version could also have something to do with it. At least you can solve it by making up for it with more fuel and air. The A version is more like a burst disc configuration. I'd like to have two identical cannons, one using a burst disc and the other using a piston, an...
by Moonbogg
Tue Jun 30, 2020 6:17 pm
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Re: Confused. Cylinder chamber to barrel ratio for compressed air.

If you have the same air volume and the chamber is 1/3 the volume, the pressure will increase by 3x.

https://www.omnicalculator.com/physics/boyles-law