Cooking up a little something...

[MrCrowley]

Cool design! As Jack said, it's a good option to avoid the hassles of needing to dump the pilot chamber each shot. Though I guess you may still need to do this after the shot to help clear the chamber of any leftover gasses.

Hard to believe it's 10 years already but the compression on your avatar definitely gives it away

[Moonbogg]

Gasses will be dumped with a separate valve so the pilot stays pressurized. I was wondering what you thought about piston durability since you have some experience with that. This will be 4x max. Can you see this piston getting shook apart from the violence? Or do you expect it would hold up?

[jackssmirkingrevenge]

I could actually use some help with understanding the best way to do this. I'm not electrically savvy and I've heard that you can ground the spark plug to the chamber and the electricity will just flow through the entire cannon until making it's way back to the stun gun. Is that right? There is no concern with shocks or a lack of electric flow? How do you hook this thing up, lol. It's embarrassing to admit, but I don't understand how spark plugs work very well.
The electricity flows through the top and jumps the gap at the bottom, returns through the outside shell where the nut is, then gets transferred into the aluminum of the cannon? What's the best way to wire up the electric current for this thing?

You have it right.

Most spark plugs are M14 metric threads, not a tap you would typically use so you might have to purchase one.

Here's one of my hybrid cartridge prototypes, you can see one of the igniter contacts is just touching the metal body:

[youtube][/youtube]

Can you see this piston getting shook apart from the violence? Or do you expect it would hold up?

Here's a modification you could make to the rear of the piston that would create an air bumper in order to avoid a hard impact:

[Moonbogg]

I fixed the piston. I feel really good about it now being strong enough. All I need to do is just add some beefier washers and that should be it. There are two 1/4" nuts on both sides with an aluminum spacer on the front to capture the UHMW piston between itself and the step in the back. I shortened the rubber as well and will use a hard rubber, like 75A hardness, like a typical o-ring. If any experimenting needs to be done regarding the piston, it should be with rubber hardness and not the piston design itself. I can't imagine why this piston wouldn't function.
First box of parts came in. Aluminum for chamber, end caps, brackets & tube plugs. With the piston situation feeling more solid, I am feeling more optimistic. The success of the entire project depends on that piston NOT sucking.

[jackssmirkingrevenge]

The success of the entire project depends on that piston NOT sucking.

Luckily, it's the cheapest and most easily replaceable component

[Moonbogg]

That's true! It's a relief to hear it pointed out like that.

EDIT: Ordered a great spark plug. Small diameter (10mm) and long reach (26.5mm). It's perfect. It even has a threaded terminal instead of those smooth ones, so I can wrap the wire around the threads and shrink tube it with a nice looking blue colored shrink tube.

https://www.ngk.com/product.aspx?zpid=9881

EDIT: Ordered almost all the rest. Just need to get the seals and hardware. Things are happening FAST. Woohoo! Hope I don't screw it all up.

[Moonbogg]

What do you think would be cooler? A trigger button on top of the handle that you push with your thumb or on the tube itself that you pull with your finger like a traditional trigger?

[jackssmirkingrevenge]

A trigger button on top of the handle that you push with your thumb

That's something I think most would associate more with an automatic weapon...

unless you're going for the Raketenwerfer aesthetic:

[Moonbogg]

Some stuff came in...

The only tragedy here is the pipe is out of round at the bottom end, so they are shipping me a new one. This was their last piece I think so hopefully it just got banged around a lot and smashed by the rest of them and the new one will be good I hope. The golf ball barrel looks pristine and beautiful. Wish I had a golf ball to test.

EDIT 3-21-19
Submitted RFQ for waterjet for all the clamps and stuff. So long as I can afford the price, I'll deliver the material straight to them (which is sitting right here).

Incase anyone is interested in what a water jet layout looks like. Those are the 5/8" thick parts. I have 1" and 3/8" parts as well as some rubber also going to be cut.




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[Moonbogg]

I just got off the phone with the guys who machined my last special project (Cobra Venom cannon). They are doing this one too. Unless something unexpected happens, and there can always be something, this project appears to have all green lights and is a full go. Everything is funded, negotiated and all deals sealed. Design is 99% with only fine tuning of a couple small details.
Check out the revised piston apparatus. I feel much better about this. No plastic in the housing. If anything breaks, wears down or simply doesn't work, it should be the piston itself and not the housing design. I wonder if the rubber can take the punishment. If not, I will go with a harder rubber. Worst case, this cannon allows for a complete replacement of the entire piston housing/piston components if it for some reason is a complete functional failure. At least the cannon itself will not be scrap. I like this. Check it out.
I also designed the golf ball barrel as an insert so it can easily be taken out and put back in quickly. I am still making the entire set of brackets in case I want just the golf ball barrel installed. If the barrel insert idea somehow fails, I still have the brackets, so nothing is scrapped. I got backup plans. This is too expensive and has demanded way too much of my energy and effort to permit any major design failures.

[jackssmirkingrevenge]

Sweet, looking forward to see this shoot. Out of interest, how much is the waterjet work costing you?

[Moonbogg]

I got two prices. The guys down the street quoted me $470. The guy I've known for about 8 years quoted me $275. I'm going with one of these quotes and ignoring the other. Brownie points if you can guess which one! It's more than just the parts you see in the image above that's getting cut.

[farcticox1]

When this is up and working everything else will be obsolete, I'll get my coat

coat.jpg (21.3 KiB) Viewed 9302 times

[jackssmirkingrevenge]

It's more than just the parts you see in the image above that's getting cut.

That's not so bad and worth it for the professional finish.

[Moonbogg]

I just bought some golf balls to test the golf ball barrel's size, and OMG. This couldn't be more perfect if they had honed it to fit. The golf ball fit so perfectly, that it touches the inside of the pipe just barely enough so it stops rolling after a few inches. It fits gently enough so you can BLOW into the tube with your mouth and easily cause the ball to roll all the way through. It's the definition of a perfect fit and I had to do nothing to it.
It's feeling more and more like the spud-gunning gods have actually smiled down upon this project and given it their nod of approval. Things are looking very good.