Cannon Design and Construction- Suggestions Welcome

I have never seen or been able to mentally visualize the workings of a negative pressure cannon based in the limited information I have come across on them. I was looking for some info on them last week and got sidetracked by cool naval photos that I tripped over while searching......

 

I think I also drilled and tapped the end of the brass rod 2-56 for these cannons. I made a brass washer/ spring retainer to go on the end. I will be posting those photos soon. I agree that the #5 die is probably a better choice to get a sharper thread... I think I used 6-32 because it was more readily available.

 

If you could get anywhere near that price it would be awesome!! As far as a problem from being chemically welded.... I think its not truly going to be much issue,the price point is cheap enough to not have to worry a bunch about serviceability, and most Indiana cannons - which were way more expensive - had the accumulators glued to the ball valves as well.

Kotori and Gascan can give a better idea on accumulator size, I think the rule of thumb is around 2 cu in per barrel, but I could be wrong.

 

This would be awesome if you could get them that low.

I might be interested in three sets.

Beaver

 

I know nothing about chemical welding but the idea gives me cause for pause.

 

Traditional Indiana cannons use PVC bonded to PVC with PVC cement. I believe that is basically the same as chemical welding: one part cleans the surface, the other part is solvent and filler to join the parts. I have often seen small leaks that need to be plugged with super thin CA and a vacuum pump, but have yet to see one end blow out. Still, that indicates that the weld is not perfect, which is why I try to maximize the bonding surface on the valve body and accumulator end caps on my cannons.

 

I *have* seen endcaps let go. Well, almost. It slid out about 1/8" before I reached the safety switch, relieving pressure. That was one failure out of about 20 PVC cannons I have built, most likely due to assembly error (failed to twist the endcap during installation, per procedure). Stephen has also reported some difficulties with chemical welding plastics, possibly for similar issues. However, I have no idea how that will apply to 3d printed ABS, or even ABS in general. The only way to know is to try it.

 

I am new to his hobby and very interested in your gun design. Do you have a set of cad drawings? I have been designing and inventing machinery for manufacturing close to 30+ years now as a mechanical engineer and there is not much to improve on your design. It is a well thought out and designed. Why reinvent the wheel when you have executed brilliantly. Please let me know.

I am a machinist as you are but with to many hobbies, I was into rc boats over 40 years ago and have come full circle with a thirst for combating ships.

 

Thanks Tugboat,

I agree with the journey. I have been into HO trains for over 20 years. a work in progress I guess. I can tell this sport is very addicting, like shooting sporting clays. you can not stop. As a mechanical engineer, making a model and adding in the working extra's is a passion for me. I have been working in 1:87 scale and to make things work and hiding the mechanics, a big challenge, such as a working scale, and operating hump yard with retarders, etc. This hobby is much more suited for me when I can hide all the guts under the deck, and ho ya, shoot at something moving. My brain is on fire with ideas and can wait to get started. I am in the information collection mode right now, hopefully for a short time.

If there is anything CAD wise anybody needs, Just let me know. In my business (I design mines) I use many programs and convert many documents to AutoCAD format, even PDF's.

 

I do have some partial cad files on this cannon. In their current form they would probably be of very little use (or even make sense) to anyone other than myself. I have an issue of starting the cad drawing to get far enough along to get all the important features placed, then I make the part and rarely finish the drawing. I am stating to build this cannon in solidworks since I am redesigning some of it. You (or anyone interested) would be welcome to the files once I get them done.

This design is really a compromise between the standard issue Indiana cannon and a boat that really isn't big enough to hold one. Many compromises were made to keep the units as short as possible, and as small diameter (magazine wise) as possible. It would have been much easier to make from all abs or the like, but to keep thicknesses to a minimum, I went with aluminum to insure nothing would blow apart.
These we far more labor intensive than I would have liked.

The other down side to this design is I cut everything to near the bare minimum (including airflow space). This has limited power a bit (they will still demolish balsa well enough) I have a couple plans to get more power from them.

@Tugboat. I'm super psyched about your printer, I hope it turns out to be a viable alternative to machining to get the big gun side of the hobby more open to the masses!! Any progress on the cannon front yet?

 

Hello Engineer, I'm always impressed with people that can do CAD work. You said you wanted something that would give you an idea as to how a big gun cannon works.
These are the four main plates to a big gun cannon that Kotori87 designed for some laser cut cannons.
http://rcnavalcombat.com/Portals/0/Users/Kotori87/WWCClqt_Cannon%20four%20main%20plates.pdf

Here is the link to the thread for the cannons: http://rcnavalcombat.com/Forum/tabid/58/aff/535/aft/441794/afv/topic/afnp/476297/Default.aspx

Beaver

 

Thanks Beaver!

 

Mines (If it can't be grown it has to be mined type of mines...)
or
Mines (We don't call them mines anymore we call them area denial munitions...)

The engineering side is why I'm in this hobby as well, plenty of chellenges to work on in the evening if I dont get to do enough real engineering at the office....

I think the past few years has been really exciting for the hobby since enough of the fun tech (microcontrollers, CNC machines, Laser cutters, 3D printers, etc) have become significantly more accessible to the average person. Most of those have only made small impacts on the hobby up to this point but they all hold plenty of capability yet to be tapped. You'll find plenty of projects to work on and areas to tweak which will keep the hobby engaging even if you aren't one of the types that builds a new ship every year. And you get to test your ideas out in the crucible of actual combat.
Best Hobby Ever!