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spudgun range, are we falling short?

A place to ask general spud cannon related questions.
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Unread postAuthor: ramses » Wed Apr 06, 2011 3:34 pm

One issue I see with the shorter wavelength radio transmitters is the ability to transmit through the earth.

I wonder if we could come up with a method to suddenly destabilize the projectile a few vertical feet from impact. That would ensure that it didn't bury itself, and only reduce range by a bit.
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Unread postAuthor: SpudFarm » Wed Apr 06, 2011 3:41 pm

I would like to suggest a glass ampule on the back of the projectile with luminous liquid.
When it lands you will get a pointer to it's location.

Another option is a ampule of female dog urine (quite big of course but it could be the drag stabilizer) and a male dog, possibly a hunting dog.

The last option is to just use a flare, nothing deadly about a fire-man's flare.. Just don't give details on the location method and it should be fine.

This thread is about brainstorms basically so that's my contribution, might be a bit odd though.
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Unread postAuthor: LeMaudit » Wed Apr 06, 2011 4:04 pm

SpudFarm wrote:so that's my contribution, might be a bit odd though.


Thinking about female dog urine is not odd... it's weird :shock:
But it might work better than sausage meat, sadly... :D

[edit] Afterthought... I will NOT be the one who collect it!
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Unread postAuthor: MrCrowley » Wed Apr 06, 2011 4:20 pm

LeMaudit,
Lead or tungsten rods, I can do either. :)


On another note, let's just say that I haven't buried the smoke idea entirely yet. Hopefully I'll find time to run a few tests and I'll let you guys know the outcome of those tests (smoke powder in a very enclosed space, how easy smoke powder can be ignited with steel wool etc.).
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Unread postAuthor: LeMaudit » Wed Apr 06, 2011 4:38 pm

Cool MrCrowley! Good news, less weight to snail mail!
Now give me this tungsten rod diameter, will you? ;-) Because you'll hate me if the rod doesn't fit the hole :lol:

About diameter, what do you want for the sabot? You said the barrel is 48.5mm... that's an exact size? If I do a plug that is 48.4, you'll be able to slide it in? My dimension will be exact, maybe +-0.05mm. I intend to make a plug in UHMW say 48.4 so you'll have a very nice low friction sabot, and cover it with a thick aluminum piece maybe 48.2 mm, just to give a bit of clearance and avoid melting the plastic. Please confirm me that you're okay with those sizes. And I'll start cutting maybe this week-end.

[edit] about magic powder, I was just thinking that for the time you reach the impact point, smoke may be completely gone :?
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Unread postAuthor: MrCrowley » Wed Apr 06, 2011 4:49 pm

Now give me this tungsten rod diameter, will you?

I can get them in either 1.6mm or 2.4mm diameters.

I was just thinking that for the time you reach the impact point, smoke may be completely gone

I was also thinking this, I thought maybe if I used enough steel wool I could delay the ignition and if the cavity the powder was in was long and thin, there would be less surface area for the reaction to take place, slowing it down.

Even if the smoke showed me the general direction the dart was heading (woods, sand dunes, beach or sea) it would help a lot.

I will confirm the precise diameter of my barrel for you today.
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Unread postAuthor: SpudFarm » Wed Apr 06, 2011 5:16 pm

http://www.weldcraft.com/parts-accessor ... lectrodes/

Good source of tungsten.


The dog urine idea isn't that bad, if you use something else to roughly estimate where it landed a dog would find it very easily for you.
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Unread postAuthor: LeMaudit » Wed Apr 06, 2011 5:18 pm

I can get them in either 1.6mm or 2.4mm diameters.


It's that small!? :shock: Then my question was stupid, I was thinking it was more like 10 or 15mm... :lol: I really know nothing about welding!

Great then, You'll stuff the hole with as many as you like :wink:
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Unread postAuthor: Hotwired » Wed Apr 06, 2011 7:24 pm

Ragnarok wrote:anything actually fast and aerodynamic enough to be worth discussing in this thread will not obligingly stick tail out of the ground.


I'm thinking that any projectile fired for maximum range is likely to be something you have to write off as single use.

Stopping it from drilling for the core would require it to change shape on impact and that kind of deceleration is going to wreck it anyway.

The critical thing is to be able to find the impact point so whatever is to be tracked has to survive to be trackable irregardless of the vehicle.
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Unread postAuthor: MrCrowley » Wed Apr 06, 2011 7:40 pm

It's a shame I can't do these testings on a large concrete runway, I'm not even sure if the sand will leave any trace of where the projectile has landed.
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Unread postAuthor: ilovefire » Wed Apr 06, 2011 7:54 pm

i still think the dye idea would work well, so then you just look for a coloured bit of sand, would probably have to hit wet sand to work though
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why make it if it dosent shoot?
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Unread postAuthor: MrCrowley » Wed Apr 06, 2011 10:00 pm

Got my calipers out, seems I was right. 48.5mm is the inside diameter of my barrel.

[edit] These two photos are to give an idea of how hard it would be to track a long-range projectile in the air.

From where this photo is taken to the tallest building in the city is roughly 4,000m:
Image

From where this photo is taken to the base of the volcanic island in the background is roughly 4500m:
Image

There is just no way an LED will help track the projectile in flight and I worry if smoke would even be visible after 2000m. Although a transmitter would be the best solution I doubt one can be made or bought that has a short (3") antenna, can transmit while possibly buried in sand, small and light enough to fit inside the projectile, has a range of ~500m and costs less than $50USD (incl. receiver).
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 07, 2011 5:43 am

Regarding the concerns of the projectile burying itself in the ground, why not add a central failure point that would cause it to break apart on impact? The nose would be free to burrow to its tungsten hearts' content, while the tail complete with buzzer/LEDs would snap off and stay visible on the surface.

The projectile would of course have to survive the shock of firing, so the sabot must be designed to adequately support it without allowing lateral forces to affect the failure point.

I think we might be overcomplicating things, because we know what the direction of firing is going to be, and assuming that the projectile is reasonably built and there isn't much wind to affect it sideways, it is safe to say that the projectile is going to land in a 10-20 metre wide strip along this vector. We will also know the approximate range thanks to ballistic calculators, so one should start searching around the predicted impact point.
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Unread postAuthor: MrCrowley » Thu Apr 07, 2011 6:11 am

Not sure how big of a difference 0.02± for a Cd is (would it be noticeable if a projectile's Cd was changed by ±0.02) but with a 20mm diameter, 100g projectile at a muzzle velocity of 360ms, a Cd of 0.1 ±0.02 can equal 1000m difference in distance. Is there an easy way to calculate a projectile's Cd value (from what I recall, there isn't)?

I also thought about a projectile that would deform on impact to prevent deep penetration or one that broke in half. This is probably a bit too complicated for what it's worth but I was thinking along your idea of a lead piston inside the projectile. Instead of dye one would fill the inside cavity with water. I was thinking that upon impact the lead piston would fly forward and try to compress the virtually incompressible water which would *somehow* force the tail section (or have the nose section detach from the body, which could be easier?) to fly off backwards (assuming the tail section had only a friction fit on the projectile). Anyway, you get the idea :D

Or do my physics fail me?
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Unread postAuthor: Crna Legija » Thu Apr 07, 2011 6:18 am

What if you had a rod the the main Projectile would slide over and the antenna of the transmitter/receiver thing is connected to. So when it hits the ground the rod will hit the sand first then the main part will begin to slide down and absorb some of the shock and not bury its self down to far, the rod will stick out to transmit. You could color it bright orange to help see it aswell. it might kill the aerodynamics, its complicated aswell.
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