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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: LeMaudit » Mon Apr 04, 2011 1:52 pm

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


Oops... missed it :? (much better than to think I forgot it...)
I'm going to look what I can find at local electronic store, hobby store, RadioShack and the like.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 5:20 pm

JDP12 wrote:Personally, I'm more tuning into this discussion as much of the sabot projectile discussion is applicable for designing High penetration projectiles as well.


A projectile that goes through the air efficiently will also cut through targets, at least in terms of shape and density. Add projectile hardness and you have a winner :D

By the way, I triedthis sabot again but with the last disk made of 1/4" balsa instead of foam - no luck at 15x, it just blew out as splinters before the projectiles. Obviously it needs to be thicker :roll:

I'm not too interested in distance shooting, but I really believe a radio transmitter/buzzer is your best bet.


If it has to compete with the ocean, I don't think the buzzer is really going to cut it.

There have been some really simple radio beacon designs posted, this one seems particularly simple and attractive - anyone with basic soldering experience should be able to put it together for very little $$$ and a dip in epoxy should ensure it survives launch and impact forces.
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Unread postAuthor: JDP12 » Mon Apr 04, 2011 5:31 pm

yea I don't think even thicker balsa wood would work. I would use a durable plastic, perhaps something like thick plexiglass.

And why are you shooting spherical projectiles!?!?!?! inefficiency.. it pains me!!!!!

But for a dart projectile, a balsa sabot with a good plastic backing should work fine. the plastic disc in back will protect the main balsa sabot.
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Unread postAuthor: LeMaudit » Mon Apr 04, 2011 5:35 pm

jackssmirkingrevenge wrote:If it has to compete with the ocean, I don't think the buzzer is really going to cut it.

Damn... good point... didn't think about the waves noise...

MrCrowley, do you fell up to the task to make this baby and try it?
The seller is in Aussie land, not so far from your Kiwi spot ;-)
I could make an internal cavity that fit it. My choice would have been to fill everything with silicone caulk but don't tell JSR ;-)

I'll check tomorrow in town anyway if I can find a loud and miniature buzzer for cheap, like those little portable alarms keychains.

[edit] How can't you love caulk after seeing that :shock: 8)
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Last edited by LeMaudit on Mon Apr 04, 2011 5:57 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 5:46 pm

JDP12 wrote:And why are you shooting spherical projectiles!?!?!?! inefficiency.. it pains me!!!!!


I want to do some APFSDS type projectiles but as I said in 24 hours I'll be away for work and it will be another two weeks before I can get anything done.

For $12 the tracker kit seems worth it.

My choice would have been to fill everything with silicone caulk but don't tell JSR ;-)


It's a free country mate, if you love caulk it's your choice ;)
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Unread postAuthor: JDP12 » Mon Apr 04, 2011 5:55 pm

interesting.. well have fun on your trip. I'm looking forward to see some APFSDS projectiles from you when you get back.... we'll miss you.
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Unread postAuthor: MrCrowley » Mon Apr 04, 2011 5:57 pm

I guess I probably could make it, you know it has an 80cm antenna though?
If the projectile buries itself in the ground, how will it transmit by the way?
Even if you had the antenna at the very end of the tail, would it be able to transmit out of the hole?

Assuming there are no problems there, I can look for some suppliers and get to work on it.
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Unread postAuthor: LeMaudit » Mon Apr 04, 2011 6:05 pm

Good point too MrCrowley :-) I personally have no idea about those potential issues but that make sense.

Are the waves particularly noisy at this location you spotted? The cheap and easy would be the noisy thing if I can find one (after all it is used by DIY rocket hobbyist for exactly that purpose so it can't be completely wrong), the over the top non-magical solution is the dye bomb / pressure design (which I kinda like for its overthetopness).
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 6:07 pm

MrCrowley wrote:I guess I probably could make it, you know it has an 80cm antenna though?


Hadn't seen that. Well if it's loose like this it might actually provide drag stabilisation instead of fins :D though probably a bit too much drag.

Yeah, the buzzer is looking more practical now...
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Unread postAuthor: MrCrowley » Mon Apr 04, 2011 6:09 pm

The other problem is wind noise. The ocean is quite loud but hopefully you'll be able to hear a high frequency buzzing over it. Even if it means I can only hear the buzzing from 30m away, it could still help a lot.
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Unread postAuthor: Zeus » Mon Apr 04, 2011 6:55 pm

A radio transmitter should work under that circumstance, radio waves aren't so feeble that a little soil stops them. Actually that's how the 160M amateur radio band works.

As long as it isn't totally submerged it should work to an extent, make sure the antenna has thick insulation (so capacitive coupling is decreased when it's beneath the ground).

If you want to use sound, try a powerful piezo and run it off expensive batteries (lithium), it should last fifteen minutes. The run time can be determined by a little bit of maths, if you know the power comsumption of the piezo and the amp-hour rating of the batteries, it's quite easy.
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Unread postAuthor: Ragnarok » Mon Apr 04, 2011 7:25 pm

Zeus wrote:run it off expensive batteries (lithium)

Expensive they may be, but lithium batteries are crazy.
I bought a set for my camera for doing a time-lapse (after the lessons learnt from earlier ones, where a cheaper set went dead on me halfway through). All in all, I got well over 6000 photos out of them on the day - and they then lasted another 8 months of normal use. :shock:
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Zeus » Mon Apr 04, 2011 7:29 pm

Jeez, you did do well out of them, I rarely use batteries so I don't have much experience with them. They'd be cheaper in the long run anyway, any you get some lithium once they're flat.

Perhaps I should edit my post to say 15 hours, not 15 minutes.
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Unread postAuthor: Hotwired » Mon Apr 04, 2011 10:53 pm

Ragnarok wrote:
Zeus wrote:run it off expensive batteries (lithium)

Expensive they may be, but lithium batteries are crazy.
I bought a set for my camera for doing a time-lapse (after the lessons learnt from earlier ones, where a cheaper set went dead on me halfway through). All in all, I got well over 6000 photos out of them on the day - and they then lasted another 8 months of normal use. :shock:


I'm in the market for a lithium battery'd camera personally.

Not that fussed by the spec but I'm dying to have something better than this lousy Samsung D75.

I'm telling you. One video clip of about 5 mins and it drains two brand new alkaline batteries as if they've been shorted.

It is a fault of the model, every review not done by a moron complains of battery life. I thought it was an exaggeration given how short the life they were claiming was. But no, it is really that bad.

Borrowed an ixus which has a lithium pack the other day, took about 2 hours of video (had to swap the memory cards) and its still saying full charge...


The radio trackers I'm looking at atm use lithium button cells, the cheapest one has a claim of 40 days transmission on a CR2032 - with a 40 mile line of sight transmission range. The more expensive ones trade off transmission time for a stronger signal it seems.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 04, 2011 11:50 pm

Hotwired wrote:The radio trackers I'm looking at atm use lithium button cells, the cheapest one has a claim of 40 days transmission on a CR2032 - with a 40 mile line of sight transmission range. The more expensive ones trade off transmission time for a stronger signal it seems.


In our case no one's going to look for a projectile for more than a day, it's better to have a strong signal for 40 hours than a weak one for 40 days.
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