SpudFiles

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A focus on small bore (1" or less) accuracy using "off the shelf" barrel components? Find a way to rifle it, etc. whatever you can dream up.

Shifts the focus and limits the size and cost of materials. Ammunition developement and consistancy of fill/valve opening become paramount.

Best grouping.(c.t.c.)...5 shots @ 10m or more on video.

That could be an idea, though you're also adding the human element of marksmanship, some people can't aim with a professionally made and consistent weapon, let alone a home built one though you could have the launcher clamped in place.

The point is however that energy-based contests will usually mean that "biggest", not "best" man wins, so exercises based on compactness, consistency, sound vs power, autoloading etc. are a better idea to make the contest accesible to all.

Still, on the other hand, nothing wrong with a contest for the "elite" that have the space, time and resources to build massive powerhouses

SpudBlaster15 wrote:Over the past couple of years, the focus of this community has shifted away from innovative design and the pursuit of high energy launchers, and more towards the construction of the same recycled cannon configurations.

I think we should concentrate more on building a cannon with a good design and better usability..
I believe that the appearance and functionality, combined with the normal spudgun power, are a better alternative than a very powerful gun that is just a high-pressure pipe with valve !

Spudguns should be a fun and safe to use and build.

spudguns can be effective, of course, but then they should be made and used so that they are safe. anti-tank gun in your backyard is not very safe ..

I am machinist. building a high-pressure guns.
but I also build a low-pressure guns with a focus on comfort, small size, light weight, trigger and handle

To give you an example of "high pressure gun" and "fun and safe cannon" both are my designs

here is a golfball cannon that was build for easy use and fun shooting:
http://www.spudfiles.com/forums/files/sawn222_895.jpg

AND
here is a high pressure cannon that I have designed, and now building:
http://s972.photobucket.com/albums/ae20 ... 20Express/

I hope you understand what I was trying say

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I am going to say something : I agree

On a more serious note, energy density is good; mach 1,5 is good ; but, can people with barrel <1" participate? I usually use 1/2" to 3/4" but not superior to that, i believe I'm not the only one.

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Finally someone kicked it off! I have been dying for something like this for a long time!
This should be a fun contest as it isn't insanely expensive so some trial and error can be done.

Is the volume restrictments still in action? Shouldn't be a problem as we judge upon volume/energy ratio.

For the problem with authentic info on the shot I would like if someone came up with an option to a chrony since not all members have that.

I think it would be easy to have a scale to film when the projetile is sitting on, then you show yourself loading it. Then set up your camera to capture the shot without any cuts. After the shot you get the camera to film the chrony (if you have one)

That should be a pretty fool proof setup.

SpudBlaster15 wrote:...Which is why I proposed a contest based on energy density. Based on the proposed judging criteria, a 50ft PVC pneumatic will have no advantage over a 6mm airsoft launcher operating at the same pressure. You can't win this simply by going big.

Hmmm... That would put a 1mm hybrid in with a chance

I was a big fan of the "Best shot on video" contest held back in Late '07/Early '08. In fact, if this falls through, it would be interesting to have a second installment of that event. It certainly made for some very entertaining video, and I especially enjoyed being selected as a judge and helping to narrow down the field.

With the proliferation of cheap high speed cameras, it should be more interesting this time round

matti wrote:here is a high pressure cannon that I have designed, and now building

Interesting, a helium powered QDV... going for the sound barrier?

For the problem with authentic info on the shot I would like if someone came up with an option to a chrony since not all members have that.

A chrony is cheaper than an average digital camera, even less if you make your own and there are various tutorials on how to use a laptop, microphone and free software to get a reasonable result. A serious spudder *should* have one

jackssmirkingrevenge wrote: With the proliferation of cheap high speed cameras, it should be more interesting this time round A serious spudder *should* have one

Hehe, I think a serious spudder should have both!

But I doubt I would buy a chrony just for this competition if I didn't already have one. The microphone method can be a easy way of cheating.

Gippeto wrote:A focus on small bore (1" or less) accuracy using "off the shelf" barrel components?

Well, I'd be interested in that.

However, as my primary interest is launchers I can actually hand fire, the main subject of this topic (being launchers that will probably not be suitable for hand firing, one way or another*) just doesn't grab me enough to get at my scarce spare cash.
*As D_Hall says, it's machined parts (which I can't afford) or other parts pushed to their limit (which isn't safe).

So, no as far as involvement in an energy contest, but I would probably get involved if an accuracy contest came up.

~~~~~

Also, one question. If defining it as energy/volume, how would volume be determined for electrothermal cannons?
If you don't include the capacitor bank, they'll win easy. And if you do, they don't stand a chance.

I'm not an expert, but IIRC, the energy density in even the best capacitors is left seriously wanting by the amount of energy that can be packed into a hybrid mix.

Two divisions is fine I guess. I think the stuff like ETC's will correlate with those with machine tools.

Does an ETC count if some of the energy contributors are kept 'under wraps'?

jackssmirkingrevenge wrote:Interesting, a helium powered QDV... going for the sound barrier?

yes 8)

I used solidworks to design it and i have run some stress simulation and flow simulation tests..and its looking very good.. max pressure 200bar
some changes will be made to the valve, but nothing big.
I start posting pics here when i have something ready.

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SpudBlaster15 wrote:Good point. I hadn't really considered this, but to be fair, one would need to include the actual energy source in some way. I'll have to think about this one.

I think the issue is that the volume of a capacitor is both storage space and structure.

While a 100 cc pneumatic vessel would just be its internal volume, and not include its walls (however thick they might be), a capacitor's volume is its total volume - making its energy storage density appear much more fixed.

But evaluating launchers on "total" volume wouldn't solve the problem. I'm not sure that working by simply barrel volume would fix the problem either, because you'd just get ridiculous C:B ratios which wouldn't really do much to further development. Weight wouldn't really help either (honest reporting could be an issue).

Ultimately, I think you'd probably need to divide launchers off into categories, so that they were only competing against launchers which were working from similar constraints.
The problem with that is that it means that lone ETGs haven't anyone to compete against.

hmm... perhaps convert the energy store in a capacitor to a volume of propane at atmospheric pressure. Or some other standard.

Another possibility is to standardize everything and go for the most thermodynamically efficient launcher. Then we have to decide if we want to consider compression adiabatic or isothermal. Expansion is adiabatic regardless.

So maybe
This would favor small, High pressure launchers, because they tend to be more efficient than LPHV guns.

for electrothermal, it would be a simple KE/PE. Would we have to factor in the energy of combustion of the capillary tube and/or fuse wire?

I'm also torn over considering a welder a basic tool. For something like this, it could well be more effective than a lathe. Perhaps divide all entries by the cost of tools required?