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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: jackssmirkingrevenge » Thu Apr 19, 2012 1:10 am

The seam would be a problem though, it would preclude the fabrication of properly fitted projectiles.

Maybe some thick walled pressure rated PVC :)

Now that I've overcome the psychological barrier of reversing the jaws on my chuck, I'll stretch the maximum diameter out to 40mm if it makes it easier, so a 1.5" ID barrel would be feasible.
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Unread postAuthor: al-xg » Thu Apr 19, 2012 5:58 am

Concerning drag coefficient measurements, one could work it out using a chronograph and a level target. You can then measure how far it dropped at that known distance to the target and compare it to initial velocity to work out drag...


Or PVC inside seamed steel pipe...
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Unread postAuthor: jimmy101 » Sat Apr 21, 2012 3:27 pm

al-xg wrote:Concerning drag coefficient measurements, one could work it out using a chronograph and a level target. You can then measure how far it dropped at that known distance to the target and compare it to initial velocity to work out drag...
Or, probably more accurate to just fire more or less straight up and time how long it is from Bang to the round hitting the ground. With a chrono at the muzzle, and knowing the mass of the ammo, you have what you need to calculate the Cd.
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Unread postAuthor: al-xg » Sat Apr 21, 2012 5:33 pm

Yeah the measurement wouldn't need to be anywhere near as accurate especially for short range target. That's fine with some projectiles, but with a few of the ones discussed here, I'd want something pretty heavy to hide under with my stopwatch :D
Although the projectile would need to stay stable and have the same drag coefficient on the way back down.

In fact I'm sure this has been suggested before as a way to test range without loosing Miniboy,
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 2:37 am

al-xg wrote:In fact I'm sure this has been suggested before as a way to test range without loosing Miniboy


It would still be a "theoretical" measurement though...
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Unread postAuthor: MrCrowley » Sun Apr 22, 2012 3:40 am

jackssmirkingrevenge wrote:The seam would be a problem though, it would preclude the fabrication of properly fitted projectiles.

Maybe some thick walled pressure rated PVC :)

Now that I've overcome the psychological barrier of reversing the jaws on my chuck, I'll stretch the maximum diameter out to 40mm if it makes it easier, so a 1.5" ID barrel would be feasible.

The only issue is falling in to the same problem as we did with the MiniBoy; not making it large enough for tracking equipment. Granted, more projectiles means more chance of finding one but I could probably only shoot 5 projectiles within a 45 minute period as it takes about 5 minutes from loading to firing for each shot and I also have to wait for the track pump to cool down between shots.
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Unread postAuthor: al-xg » Sun Apr 22, 2012 4:44 am

It would still be a "theoretical" measurement though...

This was more as an alternative to the homemade windtunnel, but it may still be worth doing as, at least, you'd have a better idea of where to look for the second shot ;)


Well in that cas, the issue is more of a: who is going to get a tracking device and build a projectiel around it ? :D
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 5:03 am

Well in that case, the issue is more of a: who is going to get a tracking device and build a projectile around it ?


You and MrC make a good point. Making more "expendable" projectiles still leaves us with the problem of finding them to measure performance.

This needs some more thought...
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Unread postAuthor: MrCrowley » Sun Apr 22, 2012 5:54 am

I think meeting one of these three conditions would be suitable for launching a long range projectile:

1. The entire range is composed of a flat, moderately hard to hard substance. This could be a salt flat (not exactly hard but still suitable), desert sandstone, a field with short grass during the dry season or even a private rural road.

2. The projectile is aimed at a large, solid object in the distance which will terminate the projectile's flight upon impact. This could be a cliff, mountain side or similar.

3. Tracking device.

Obviously, #3 would be the best bet but it may not be a realistic option (such as in the case of the miniboy). #1 would also be quite good and would work well with a mark-on-impact device, but again it isn't always a realistic option. #2 is probably the least preferred option and even something as large as a cliff can be difficult to hit from 4000m away. The main benefit is knowing the extent of the projectile's range. The two main problems are aim and recovery; a mark-on-impact device would be required.


On another note, I should have about $100USD from YouTube ad revenue in a month or two. Assuming I'm not broke at the time, I would be willing to spend it on a reliable tracking device that fits MiniBoy.
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Unread postAuthor: al-xg » Sun Apr 22, 2012 6:34 am

Well then starting off with a 4k shot maybe isn't best way.

Might be better to start with much shorter ranges, increasing incrementally, build up on the data gathered from the shots, instead of risking it all on one shot and possibly getting nothing from it.
Predicting the landing point should get more reliable with every shot, increasing chances of success at longer ranges.
I'm sure that would also highlight quite a few possible improvements along the way.



EDIT:
http://www.starchase.com/howitworks.html :) We just need a cheaper one of these.

EDIT:
I know we've been here before, but it seems one of those small cheap android phones with GPS would be a much more cost effective way of getting good tracking capabilities, and would allow for quite alot of other information to be recorded such as flight time, an estimate of altitude, even video ???
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 10:22 am

al-xg wrote:I know we've been here before, but it seems one of those small cheap android phones with GPS would be a much more cost effective way of getting good tracking capabilities, and would allow for quite alot of other information to be recorded such as flight time, an estimate of altitude, even video ???


Still too expensive, and also fragile.

This looks like a much cheaper proposition, doesn't rely on GPS, assuming you could get to the general impact area.

What I would do is fire along a determined line and then drive along it with the ATV, the projectile definitely couldn't have strayed more than 100 metres to either side. Before firing though you would need to do some testing to determine how well it actually works, if being buried a couple of inches affects it and see if the electronics need to be hardened against the violent acceleration and deceleration.

This one seems like a better bet, 50 bucks or so but it comes with two tags and claims a much longer range. Tempting, I might get one to try it out.

The cheapest GPS tracker I could find is not much more expensive, but it requires a GSM simcard and also would need to hbe reconfigured to fit in a streamlined projectile.

This is interesting, cheap and stops beeping when you'r near the object but gives no indication of where to find it.

edit: screw it, ordered this. 30 euros posted and comes with two tags.
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Unread postAuthor: al-xg » Sun Apr 22, 2012 12:10 pm

£30 for a pulse mini android phone. But yeah, one shot, and more to go wrong. I might try one as a data logger/telemetry feed on a much less extreme project.


That last one looks ok, the emitter is relatively small too.
The alarm on the emitter could come in handy too.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 12:57 pm

I'll do some testing, see if the emitter still works well when buried a foot or so in the ground, and if it functions well when encased in epoxy because it would be best to have it potted to survive the shocks of firing and impact.
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Unread postAuthor: dewey-1 » Sun Apr 22, 2012 2:51 pm

JSR

When you receive the package take some pictures of the tag (transmitter) circuit board assembly and its dimensions.

It is possible to use only the circuit board to reduce the size considerably.
I can help out on the electronics if needed to reduce the size and possible rewiring.

Consider a conformal coating that is not as hard as epoxy. More like a rubber texture. I think it is Dow 1377. I will look it up.
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Last edited by dewey-1 on Sun Apr 22, 2012 2:54 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 2:52 pm

I was hoping you would chime in :) will do, possibly you can suggest how to enhance the transmitter aerial to increase range.
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