Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 56 users online :: 4 registered, 0 hidden and 52 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

spudgun range, are we falling short?

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Unread postAuthor: CpTn_lAw » Mon Apr 04, 2011 6:13 am

MrCrowley wrote:
CpTn_lAw wrote:Why did anybody think about saboting a crossbow dart? Fit them with lumenoks and there you go : tracer spudgun round?
Imagine shooting them from a hybrid? Supersonic, very aerodynamic,fin stabilized....

Don't think they're heavy enough. I couldn't find a solid number on an arrow's Cd so I used 0.03 which I found some place and the range of an arrow improved from 1800m to over 4000m by increasing the weight from about 25g to 80g.


You can always find a way to increase the mass! and if i recall, you can use Cd= 0.0315 ± 0.001




_____________________________________________
I ran some numbers for a 0.25" diameter dart weighing 100g (using a tungsten core it would be shorter than a foot) fired at a very feasible (using a sabot) 850 feet per second and with an achievable CD of 0.1, and GGDT suggested a range of no less than 6207 metres - over three and a half miles!

Can we make this, please? Pretty please with a cherry on top? :D[/quote]
  • 0

"J'mets mes pieds où j'veux, et c'est souvent dans la gueule."
User avatar
CpTn_lAw
Brigadier General
Brigadier General
 
Posts: 987
Joined: Sun Sep 11, 2005 9:10 am
Location: France
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 6:27 am

MrCrowley wrote:Don't think they're heavy enough. I couldn't find a solid number on an arrow's Cd so I used 0.03 which I found some place and the range of an arrow improved from 1800m to over 4000m by increasing the weight from about 25g to 80g.


Arrows and bolts are hollow inside, what's to stop you packing it with lead shot or tungsten rods? A 0.040 x 7" rod costs 49 cents and weighs 2.7 grams ;)

Basically I'm wondering how to differentiate between a 20mm sabot-ed projectile in a 42.3mm barrel and, say, a 35mm sabot-ed projectile in a 42.3mm barrel.


I was using a virtual launcher in GGDT with a generic valve (Cv 100, opening time 1ms, dwell time 999, dead space 0, seat 3 inch), oversize chamber (10 inch diameter, 100 inch length) and 100 inch barrel.

All I wanted was performance data from the external ballistics calculator so the launcher specifications were irrelevant as long as I got the correct projectile diameter and velocity. I just put say for the 2cm projectile, 2cm projectile diameter and barrel diameter, and varied the pressure until I got the desired velocity (700 fps, 1000 fps etc.). For the full bore projectile, I just changed projectile and barrel diameter to 4.23cm and again played with the pressure until I got the desired velocity.

Can we make this, please? Pretty please with a cherry on top? :D


If I had access to a beach like that I would have made it already!

What I want to do is make some smaller scale version of this that will fit in a 3/4" bore with a steel nail for a body, and do some penetration tests with my hybrid against steel plate. If it can go through steel well, then it can go through air ;)
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: al-xg » Mon Apr 04, 2011 6:42 am

Edit: oh too slow

I wondered about the range estimations too.
With drag being 1/2*rho*Area*Velocity^2*Cd, if the drag coefficient incorporates the bore sized fins thats ok, but if the projectile is sub-calibre and supported by the sabot then the frontal area will be off.

Its really not that hard to make a separate basic range calculation tool, in fact I wrote one in Excel that is a least as accurate as GGDT's range calculator. (temperature, humidity, altitude, wind speed and direction, magnus effect are just for fun really or to be used as a correction factor unless of course you have a weather station and crazy accurate projectile models)
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 6:53 am

al-xg wrote:wind speed and direction


This definitely is going to affect results, make sure the wind is behind you!
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: MrCrowley » Mon Apr 04, 2011 6:55 am

jackssmirkingrevenge wrote:
al-xg wrote:wind speed and direction


This definitely is going to affect results, make sure the wind is behind you!

Last time I was there it was very strong but in the right direction, down the beach :wink:

When you said if you had a beach like the one I do that you would've made that dart already, would you just fill an arrow with tungsten rods or get someone to make you one?
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 7:15 am

MrCrowley wrote:would you just fill an arrow with tungsten rods or get someone to make you one?


As I said I would be more inclined to make "my" design with the full bore fins. It is not the ideal aerodynamic shape, because in order to contact the bore the fins are somewhat longer than they need to be, increasing drag, however the ease with which a sabot can be made more than negates the disadvantage in my view.

An arrow packed with heavy material would be a better projectile, and really in spite of my concerns it shouldn't be that hard to make a suitable sabot.

Something like this, basically two short cylinders, one of which has a central hole for the arrow shaft and is then cut into three or four "petals" that separate once the projectile has left the muzzle.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LeMaudit » Mon Apr 04, 2011 8:22 am

MrCrowley wrote:Just thinking it might leave a rough trail on the beach,

I don't think it would make anything visible either. it's a very small quantity of dye stretched on a very long distance.
As I said in a previous answer, the only viable solution with dye I can think off would be to make it expel at the impact point. But because the shell will most certainly bury itself in a deep hole, I'm afraid the dye will stay inside the hole, without any visible effect at all from a distance. But it is worth thinking... hmmm...


jackssmirkingrevenge wrote:Something like this, basically two short cylinders, one of which has a central hole for the arrow shaft and is then cut into three or four "petals" that separate once the projectile has left the muzzle.

I have nothing against making the sabot simpler than my design because right now it's far more complicated to build than the shell itself :D But we have to solve one way or the other the retrieval problem, because with a sabot design that push a disk from behind, the gas will not reach the shell before it is outside the barrel.

And making smaller and denser the missile will most certainly improve the distance, I fully agree with every suggestions in that direction, but I'm afraid will make the retrieval quasi impossible without homing equipment... which is not that small on a reachable price, have a fair chance to break, and anyway too expensive unless one make its own... but that's a hobby in itself I think ;-)

[edit] I'm currently pursuing the idea of making a missile with dye expelled at impact. And without magic powder, only compressed air as it should be ;-)
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: LeMaudit » Mon Apr 04, 2011 11:09 am

Okay, here's some more food for thoughts.

You have a plunger (this little rod with 2 o-rings) that I expect to be kept in place by pressure, then dislodged at impact.
The internal cavity contain some bright liquid dye that can go through the holes in the tail if the plunger is moved.

To fill it, You unscrew the nose, drop the plunger inside (push it in place), fill with dye, then close and add some compressed air. I expect the plunger to stay right where it is, just by pressure alone.

At launch, centrifugal force will keep the plunger in place.

A impact, the plunger will sink close to the nose, opening the tail slits for a powerful dye spray. because the opening is just below the fins, I expect a widespread spray range.

What do you think?
  • 0

Attachments
miniboy3.png
Air-liquid-Tire-Valve.jpg
This could be used as a valve that you can unscrew to fill the cavity. The cap would be replaced by the brass heavy nose
Air-liquid-Tire-Valve.jpg (7.6 KiB) Viewed 421 times
User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: JDP12 » Mon Apr 04, 2011 11:18 am

JSR... I think smalls aboted projectiles have a lot to offer energy wise.. just look at the Steyr IWS 2000.

Just make sure the projectile is extremely hard so it doesn't bend... I could easily see a .25" or .325" diameter saboted dart have extremely good penetration results.
  • 0

"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 11:41 am

Interesting thoughts... How about using the impact itself to spread the dye through a piston as per the attached diagram, which forces the dye out by popping the rubber bungs. Maybe the bungs should be moved more towards the tail in case the nose is buried in the sand.

Still, how easy is it going to be to spot a patch of dye on a sprawling beach?

I think small saboted projectiles have a lot to offer energy wise... just look at the Steyr IWS 2000.


Indeed. It's going to have to wait a couple of weeks though, tomorrow I'm of to España and I'll be away from my workbench.
  • 0

Attachments
dyeprojectile.JPG
dyeprojectile.JPG (16.52 KiB) Viewed 401 times
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: LeMaudit » Mon Apr 04, 2011 11:55 am

I didn't though about using the plunger as a piston... hmmm....
it simplify a lot things for sure :D

But I still think the spray must be through the tail an upward to have a chance to be visible, not on the sides as the missile will certainly be fully buried. I'll try to incorporate that in the design.

I would avoid lead to keep the hope of reusing the thing. Lead will just splat I think, even on sand. Or at least badly deform. But maybe as a filler, depending of the final weight. Brass is quite heavy, and I have bronze for bushings, I think it's even heavier (can someone confirm that?)

Basically, we are now designing an over the top water bomb right? :D
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: Crna Legija » Mon Apr 04, 2011 12:10 pm

what if you use the same mech to ignite the powder thats in side of flares, if it can ignite from impact.

how about the key finder thing that when it hears you whistle starts to beep, might work if you have people looking to find the rough place it landed, then just whistle till you hear it beep.
  • 0

'' To alcohol... The cause of, and solution to, all of life's problems.”
--Homer Simpson

Add me on ps3: wannafuk, 8/11/11 cant wait
User avatar
Crna Legija
Major General
Major General
 
Posts: 2333
Joined: Sun Jul 20, 2008 5:14 am
Location: australia
Reputation: 0

Unread postAuthor: LeMaudit » Mon Apr 04, 2011 12:25 pm

Crna Legija wrote:what if you use the same mech to ignite the powder thats in side of flares, if it can ignite from impact.


Let's forget discussion about magic powder. It's against the rules and they have been bended enough I think. A challenge to do it without any burning spells is quite interesting too; and frankly much more difficult! ;-)

Crna Legija wrote:how about the key finder thing that when it hears you whistle starts to beep, might work if you have people looking to find the rough place it landed, then just whistle till you hear it beep.


:D the vision in my mind is quite surrealistic... people wandering around the beach, with nothing in sight for miles, whistling over and over like if they were calling an invisible dog... :lol:

Seriously not a bad idea, but it would involve cash (those things cannot be found at the dollar store) and I'm really not sure it would survive the impact! I have some serious doubt about brass and thick aluminum, so what it would do on fragile electronic components...
Really, I would not bet on this one.

Now if some mad electronic wizard could come with a cheap and sturdy solution to emit a loud bip at regular interval for an hour at least, I would be willing to grab my soldering iron :D

[edit] a tracking device don't seem to be that complicated after all:
http://www.talkingelectronics.com/projects/Beeper%20Bug/BeeperBug.html
http://www.talkingelectronics.com/projects/MiniTracker/MiniTracker.html
but I'd still vote for a lound beep... can't find a schematic or kit small enough... any link someone?
  • 0

User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 1:34 pm

LeMaudit wrote:Basically, we are now designing an over the top water bomb right? :D


:D

I think the dye option is a bit of a dead end, though it seems to work for 40mm practice rounds without pyrotechnic enhancement (though it is fired at ranges less than half a kilometre):

Image

I also think we're exagerating the vulnerability of electronic circuits. I posted this link for an acoustic beacon in the first post.

Image

Very cheap and surely if they could make 60 years ago electronic proximity fuzes that are essentially small radar transmitters/receivers that can survive being shot at several thousand feet per second, we can make a simple buzzer circuit that can be shot from a hybrid without disintegrating.

Those tracker designs look interesting, and coating the circuit board in epoxy and placing it in a padded housing as I suggested before should ensure it survives both the shock of firing as well as impact with the ground.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: JDP12 » Mon Apr 04, 2011 1:37 pm

To be honest, for these long range applications.. i believe a radio transmitter is really the best bet. Personally, I'm more tuning into this discussion as much of the sabot projectile discussion is applicable for designing High penetration projectiles as well. i'm not too interested in distance shooting, but I really believe a radio transmitter/buzzer is your best bet.
  • 0

"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

PreviousNext

Return to General Spud Cannon Related

Who is online

Registered users: Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'