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Spudfiles Kinetic Energy Contest

Comments, Suggestions, Questions, anything to do with the website or community it's self. This is a place to express thoughts about making this community better.
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Unread postAuthor: Gippeto » Thu Jul 29, 2010 12:17 am

x3


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.
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 29, 2010 12:24 am

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 :roll: 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 ;)
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Unread postAuthor: matti » Thu Jul 29, 2010 1:54 am

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 :wink:

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 :D
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Unread postAuthor: SpudBlaster15 » Thu Jul 29, 2010 2:00 am

ramses wrote:Perhaps modify it a bit and say " most KE given 2 minutes of loading and firing"


At the current time, I can achieve approximately six 3000ft-lb shots in that time period using one of my cannons, so although this would be directly inline with my current launcher pursuits (KE vs ROF), I don't think it would fit the spirit of this competition, which is to maximize energy density.

DYI wrote:Divide achieved muzzle energy by the launcher's total internal volume (barrel + chamber), highest number of joules/cm3 wins. It includes everyone, regardless of available testing area.


This would be a perfect system for choosing the winner. Energy/Volume is ideal, and more refined than my original proposal, which wasn't specific with regard to the launcher dimensions that would be used.

DYI wrote:My idea for the two necessary classes in such a contest are:

1. Off the shelf parts with no more modifications than are achievable by common tools (drill press, all hand tools, grinder, MIG/stick welder, etc...)

2. Parts requiring use of a mill, lathe, or other very expensive, uncommon equipment, whether using heavily modified fittings or machined from bar stock.

Everyone modifies their parts to some extent.


I'm also in agreement with this, and your excellent point regarding the direction of spudding technological development.

PCGUY wrote:Even though I don't fully understand how this would be measured in the first place accurately and honestly by each contestant. If someone could explain, I would be grateful.


DYI and I were tossing around around some ideas in the chat earlier today, and I'm quite fond of his proposal: Shots are to be fired over a chronograph, where after passing through the light gates, the round impacts a ballistic pendulum. This would give you a velocity reading, and eliminate the potential for the shooter to lie about the projectile mass, providing the mass of the pendulum itself is measured and recorded in the contest entry video.

It's not perfect, but I'm sure we'd be able to work something out.

PCGUY wrote:Most people do not realize the enormous amounts of details and rules and planning it takes to get a full contest in swing.


Yep, it requires a substantial amount of effort on the part of the organizers, but I'm willing to devote a significant amount of time to this if it takes off and some others agree to provide assistance.

This thread was intended to test the waters, and at this point, it seems there is reasonable interest.

PCGUY wrote:The past contests have not always been the best, as it can be hard to come up with ideas for the contest.


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.

D_Hall wrote:You've got two options....

1) Unlimited tech. This results in the familiar, "He with access to a CNC mill wins" that's already mentioned.


DYI's suggestion of dividing the contest into two categories would apply here. The members with access to machining equipment would be able to compete against each other, and this would surely result in the production of some very impressive and potentially groundbreaking launchers. That's essentially the purpose of the contest: Push the limits of spudgun design; it doesn't really matter if you use a 4 axis CNC mill to achieve the goal.

D_Hall wrote:2) Pushing limited tech beyond the normal boundaries.

Number 2 means safety margins go away. Number 2 means there's a very good chance that somebody gets hurt. Not good.


I believe that most of the people who would be attempting such designs would be more than capable of risk management, even when the safety factors start to decrease to dubious levels. For example, shoulder firing a 50X Sch80 steel hybrid would be akin to attempting suicide, but extending your ignition cables to 50ft and hiding behind a concrete wall while triggering the ignition would leave little room for serious injury.

jack'sragingbileduct wrote:I would tend to be in agreement with Mr. Hall here, the premise of such a contest immediately eliminates most spudfiles members by its very nature.


While this may be the case, we've never had more than 10 - 20 cannons entered in any previous Spudfiles contest. With a topic such as what this forum centers around, it's pretty difficult to find a concept that is both interesting, and doesn't naturally eliminate a majority of its potential applicants.

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


This is exactly the type of design direction I'm trying to steer away from with this contest idea. IMO, too much effort has already been placed on optimizing certain characteristics of small, low power designs. If this community truly wants to move forward, we need to shift the focus towards the launcher propulsion systems themselves.

jack'scompletelackofsurprise wrote:The point is however that energy-based contests will usually mean that "biggest", not "best" man wins...


...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.
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Unread postAuthor: CpTn_lAw » Thu Jul 29, 2010 2:11 am

I am going to say something : I agree :D

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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Unread postAuthor: SpudBlaster15 » Thu Jul 29, 2010 2:18 am

CpTn_lAw wrote: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.


Yes, of course. Any barrel diameter would work, as it's the overall launcher volume we'd be looking at. The cannon I would be building for the contest would likely fall into the range you mentioned.
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Unread postAuthor: SpudFarm » Thu Jul 29, 2010 2:52 am

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.
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 29, 2010 3:28 am

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 :D

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 ;)
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Unread postAuthor: SpudFarm » Thu Jul 29, 2010 4:27 am

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.
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Unread postAuthor: Ragnarok » Thu Jul 29, 2010 5:18 am

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.
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Unread postAuthor: inonickname » Thu Jul 29, 2010 7:02 am

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'?
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Unread postAuthor: matti » Thu Jul 29, 2010 9:10 am

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 :D
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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Unread postAuthor: SpudBlaster15 » Thu Jul 29, 2010 11:58 am

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


I believe the best way to go about it would be to simply judge based on energy/volume, with no restriction on the maximum volume.

Ragnarok wrote: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.


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.

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


Since 'magic powder' (Whether HE or otherwise) based propulsion systems are not legal to discuss or showcase on this site, I think you'd have a hard time convincing anyone that such a cannon design would be appropriate for a Spudfiles official contest entry. If it were my site and my legal responsibility, I would have no issue with it, but I don't make the rules.
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Unread postAuthor: Ragnarok » Thu Jul 29, 2010 12:25 pm

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.
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Unread postAuthor: ramses » Thu Jul 29, 2010 1:44 pm

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

Code: Select all
                      KE
 P*V + the energy contained in the fuel.


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?
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