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A place to ask general spud cannon related questions.
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Unread postAuthor: Scimitar » Thu Feb 07, 2008 5:00 am

Gday, My name is Damian, and I live in Brisbane Australia. I found your site by accident whilst trying to do research on building a gun for my scale tank.
Peoples I am new to spud guns But not to weopans, and so I have taken a fair bit of a look around the site trying to find what I need. I have to compliment so many people on their injinuity, but theres so many so Ill just say a hearty well done to every one.
Down to Buisness, I need to construct a gun for my scale tank. My scale tank is a 60% scale scimitar tank. It will be used in Tank on tank combat, but this feature has only just been introduced to our forum. http://www.scaledtanks.com/news.php

Here is my Scimitar, as it stands at the moment.
Image

And here is one that a good freind has built.
Image

Now to my ideas and request fro help in design.
I need a gun that uses compressed air only that can be air compressor filled. I would like it if the aircompressor can stay connected as well.
Id like the gun to lob a paintball of about 18mm diameter over 500 ft (Possible?). That would be the desired maximum distance but will rarley be used at that range, but more importantly accurate to at least 100 meters.
The air tanks I would like to make from steal round tube, and be mounted in boxes on the out side of the turret, to allow for any mishapps with high pressure air.
The breach must allow reloading, Ie not to keep putting paint balls down the barrel, so it needs to have a breach and if its possible to self reload using expent air?

If any of you guys can help with design or ideas for me to desgn it I would very greatfull.
Cheers Damian
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 07, 2008 5:18 am

Very nice mate!

I'm assuming the finished result will look something like this (though with a big Aussie banner of course :D )

Id like the gun to lob a paintball of about 18mm diameter over 500 ft (Possible?).


very - with a good valve, long enough barrel and decent pressure this is a realistic target.

if its possible to self reload using expent air?


It depends on your level of expertise really - if you can replicate a mechanism like this (or variations of it, there are several designs on the site) on a larger scale then you're sorted. If not, a simple hole in the barrel covered by a sleeve will allow for easy manual reloading.

As regards to your air supply, since this is vehicle mounted have you considered a SCUBA tank or similar coupled to a regulator?

A modified 1" solenoid valve on a 3/4" barrel at 150 psi should be sufficient in terms of power, but beware, at those sort of velocities even a paintball is not something you want to hit a person with, this paintball versus water jug video should give you an idea of the power potential.
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Unread postAuthor: Scimitar » Thu Feb 07, 2008 5:52 am

Thanks fro the quick reply. Yes the tank will look like sismilar to that but more tlike this,
Image
In Australian cam colours

The Scuba idea is good buy Im thinking of the cost I could build a steel cylinder fairly easily as I have the materials at hand.
I like your concept on the Syringe but have a question does the spring on it slow down the expelled air? and presumably using a slide thing me jig to push the amo, and would this damage the paint ball before its fired?
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Unread postAuthor: Ragnarok » Thu Feb 07, 2008 5:54 am

Interesting hobby you've got there - and that's not "interesting" said in anything other than a genuine manner.

Lobbing a paintball 500 ft isn't too hard. The difficult part is making it accurate at that sort of range.
You're going to need to start to define accurate here. If accurate means able to hit a largish tank replica most of the time, that shouldn't be too hard, but don't expect pinpoint accuracy. However, a hop-up (back spin) system on the launcher will help flatten the projectile trajectory, and improve range and accuracy.

Autoloading launchers are a bit more complicated, but as JSR suggested, there is nothing to stop you building something like a blow forward loader. They're not too complex, and are perfectly fine for spheres like paintballs, although the tolerances will need to be reasonable, or you can expect a lot of chopped balls. There are other options if you want them though.

Now, an important word (or really, a short novel) of warning. Spudguns can be very powerful - and there may be problems that arise if you're firing at another "tank" which presumably has someone sticking his head out to see. If you have a launcher that can fire that 500ft, you'll have to know that you won't be able to use it at close range without turning the velocity down a lot - that's basic safety.
The other thing is I can see these "tanks" are made from wooden panels, but again, if the velocity stays up, I have seen launchers put holes through that sort of thing at short range. And I'm sure people don't want holes or dents in their hard work.

I have a launcher that can easily put paintballs over the 500 ft you want, but at short range, it has torn holes in plate steel - so I hope you can see my point that power is going to need to be controlled. Never one to shy away from self promotion, you can see the very launcher doing that sort of thing with paintballs alongside other ammunition in this Youtube video.

Don't get me wrong, I'm not saying it shouldn't be done, but it needs to be done carefully.

However, this control should be easily if you use a reliving regulator to feed the main chamber. Have a high pressure setting for long range, and turn it down for short range, and because of the reliving design, the regulator will bleed off excess pressure.
(Another reason for the hop-up is that you can still maintain a good range with a lower velocity, making it safer)

Now, for this, you'll ideally need a valve type where you can fill from the chamber, otherwise, relieving pressure from the pilot will only fire the cannon when you don't want to.

The best known variety of valve like this is known as a Sprinkler valve. Now, I'm not sure how easily these are found in Australia, the main reason being I'm British, but here, they're not too common.

It's going to take a little work, but as I can see, you're hardly short on construction skills.

Well, I hope that's given you a couple of ideas and facts.

But, I have one important question - will your replica come with the built in water boiling facilities to allow your tank to make tea and coffee?
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 07, 2008 6:07 am

does the spring on it slow down the expelled air?


Not really, it actually allows pressure to build up in the breech allowing for a more powerful shot.

presumably using a slide thing me jig to push the amo, and would this damage the paint ball before its fired?


I can see how this might be an issue, but if you design it in such a way that the bolt tube has a relatively large contact area with the painball, and the paintball is already in contact with the bolt when it starts moving forward, you should be fine.

But, I have one important question - will your replica come with the built in water boiling facilities to allow your tank to make tea and coffee?


That's a quintessentially British design feature, the Aussie variant probably has a beer keg :D

A SCUBA tank would much more compact, but if you made a reasonably large air tank (50 litres or so, as much as you can manage) at compressor pressures, say 120 psi, should give you enough shots to last a tank battle :)
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Unread postAuthor: Carlman » Thu Feb 07, 2008 6:10 am

Ragnarok wrote:The best known variety of valve like this is known as a Sprinkler valve. Now, I'm not sure how easily these are found in Australia, the main reason being I'm British, but here, they're not too common.


they are very common in Aussie land, Bunnings and any plumbing store will have heaps.

Ragnarok wrote:But, I have one important question - will your replica come with the built in water boiling facilities to allow your tank to make tea and coffee?


More like a bar fridge to keep those yeasty drinks ICE COLD :D


that tank is coming along nicely mate :)

Good to see another aussie on this here forum, even if you are making this for another hobby you may make some 'infantry weapons' too :D

What will be the driving the tracks on this beast?

EDIT: your damn right about the beer keg jack :D
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Unread postAuthor: Scimitar » Thu Feb 07, 2008 6:24 am

Guys thanks so much for the info and warm welcome. Erm.... No tea and coffee as said plenty of the amber nectar and ice cold too its ny on 28 C at the moment and its just after 9 pm.

Carlman you bring up an interesting point, If JSK could perfect his auto loading gun then thers the provision to add a Coaxial gun, FIRE frozen pees or something!

Re the drive mechanisum it will be sprocket driven, just tike the real tank, and is powered by 2 nine and a half HP engines driven through a specialy designed gearbox.
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Unread postAuthor: Scimitar » Thu Feb 07, 2008 6:35 am

Ragnarok wrote:Interesting hobby you've got there - and that's not "interesting" said in anything other than a genuine manner.

Lobbing a paintball 500 ft isn't too hard. The difficult part is making it accurate at that sort of range.
You're going to need to start to define accurate here. If accurate means able to hit a largish tank replica most of the time, that shouldn't be too hard, but don't expect pinpoint accuracy. However, a hop-up (back spin) system on the launcher will help flatten the projectile trajectory, and improve range and accuracy.

Autoloading launchers are a bit more complicated, but as JSR suggested, there is nothing to stop you building something like a blow forward loader. They're not too complex, and are perfectly fine for spheres like paintballs, although the tolerances will need to be reasonable, or you can expect a lot of chopped balls. There are other options if you want them though.

Now, an important word (or really, a short novel) of warning. Spudguns can be very powerful - and there may be problems that arise if you're firing at another "tank" which presumably has someone sticking his head out to see. If you have a launcher that can fire that 500ft, you'll have to know that you won't be able to use it at close range without turning the velocity down a lot - that's basic safety.
The other thing is I can see these "tanks" are made from wooden panels, but again, if the velocity stays up, I have seen launchers put holes through that sort of thing at short range. And I'm sure people don't want holes or dents in their hard work.

I have a launcher that can easily put paintballs over the 500 ft you want, but at short range, it has torn holes in plate steel - so I hope you can see my point that power is going to need to be controlled. Never one to shy away from self promotion, you can see the very launcher doing that sort of thing with paintballs alongside other ammunition in this Youtube video.

Don't get me wrong, I'm not saying it shouldn't be done, but it needs to be done carefully.

However, this control should be easily if you use a reliving regulator to feed the main chamber. Have a high pressure setting for long range, and turn it down for short range, and because of the reliving design, the regulator will bleed off excess pressure.
(Another reason for the hop-up is that you can still maintain a good range with a lower velocity, making it safer)

Now, for this, you'll ideally need a valve type where you can fill from the chamber, otherwise, relieving pressure from the pilot will only fire the cannon when you don't want to.

The best known variety of valve like this is known as a Sprinkler valve. Now, I'm not sure how easily these are found in Australia, the main reason being I'm British, but here, they're not too common.

It's going to take a little work, but as I can see, you're hardly short on construction skills.

Well, I hope that's given you a couple of ideas and facts.

But, I have one important question - will your replica come with the built in water boiling facilities to allow your tank to make tea and coffee?


Thanks mate, Yes I was aware of the need to turn down and on our tank site this a major saftey issue.
The pannels of the tanks are in the main 15 mm thick and anytank battle will be commenced buttoned up (no heads out the top).
I saw the HEAl gun before on YOTUBE this was the reason I found the site, If its not to forward, can you may be emial me some ideas baced on the this gun!
As I said I would like a semi automatic though and again if you have any ideas then please advise me. I realize your time is valuble so ther is no hurry Ill just appreciate the help.
PS loved the music on the video too great stuff!
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 07, 2008 6:44 am

Scimitar wrote:If JSR could perfect his auto loading gun then thers the provision to add a Coaxial gun, FIRE frozen pees or something.


For a coaxial you could easily build a cloud BBMG firing 6mm airsoft BBs that feeds off the same air supply as the main gun, though the ammunition might be hard to locate in Oz.
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Unread postAuthor: Ragnarok » Thu Feb 07, 2008 6:58 am

jackssmirkingrevenge wrote:That's a quintessentially British design feature, the Aussie variant probably has a beer keg

Of course, how silly of me.
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Unread postAuthor: Scimitar » Tue Feb 12, 2008 4:23 pm

here is a bit od a build video up untill present day.
http://au.youtube.com/watch?v=zJrwiAmZu20
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Unread postAuthor: Ragnarok » Tue Feb 12, 2008 4:52 pm

Nice.

Somehow, I completely missed your previous post... I'm sorry about that. But if you still want me to provide some ideas, I'm completely happy to do so - I've got a reasonable amount of free time, so something to do with it is always appreciated.

I'm a little busy tonight, but I might be able to fire off an e-mail in the next couple of days.
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Unread postAuthor: Scimitar » Tue Feb 12, 2008 4:57 pm

Thanks mate, Yes I would appreciate any thing you can help me with. Ps your avtar looks like my dog!
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Unread postAuthor: Infernal Maveric » Tue Feb 12, 2008 7:14 pm

You mentioned semi-auto?

It is possible to have fairly efficient gravity fed semi-auto that would be pretty air efficient.

The valve would be a Quick Exhaust Valve (AKA: QEV) and would be piloted by a blowgun (manually), or by a safety release valve (automatically).

if you like, I could draw you up a simple diagram as to how it would work, and on the mounting of the gravity fed hoper if need be? I get kinda bored at college now-a-days

EDIT: Meant Blowgun, rather than Ball valve
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Last edited by Infernal Maveric on Tue Feb 12, 2008 7:22 pm, edited 2 times in total.
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Unread postAuthor: thespeedycicada » Tue Feb 12, 2008 7:16 pm

The valve would be a Quick Exhaust Valve (AKA: QEV) and would be piloted by a ball valve (manually),

why not a blowgun?
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S.P.E.C.S update mk 1 construction begining in febuary all the maths for it are done plans are drawn up and parts are listed.
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