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Frankengun

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Griff

Griff

Certified SCUBA Rider
May 7, 2002
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why should we build the frankengun

i can think of 100's of no so serious answers, but i'll restrain myself and tell you what i would like to get from it.
if you can build a long gun that shoots say 15m, then i want a short version that shoots 7m. i would be cool to dive with a gun thats less than 1m long, but with the clout of a 1.4

otherwise, you'll be bored in joburg and you know what they say about idle hands...:D
 
S

SASpearo

Desk Driver
Dec 6, 2001
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Aahh ....

So, power versus maneuverability should be better than it is now.

What about accuracy? Or are you hoping to get that with higher power / more speed?

And I won't be that bored in Jo'burg (Pretoria actually) - There's a nice little 7m dive tank about 2 minutes drive from my house - yes the infamous 'poker under water next to the restaurant' dive tank .... grin
 
Griff

Griff

Certified SCUBA Rider
May 7, 2002
557
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hmmm

Originally posted by Iyadiver

must check the DU specific gravity,

Lead 11.34
Steel, cold-drawn 7.83

if so then why arent we all using lead spears?;)

but you are right about tungsten being a killer metal. not only is it heaver than steel, its got higher unlimate strenght and greater stiffness too.
but maybe tungsten has got some other properties that make it unusable, like trying to machine it. SASpearo, you're the metal guru.

and with regard to the frankengun. accuracy is paramount. it will be useless shooting 15m without accuracy. if it isnt accurate, x-gun would be lotto-gun "tatta ma chance, tatta ma tuna" :D

and about this dive tank, can you elaborate. does it have a window onto a resturant? that could be a lot of fun. "waiter, waiter! i think that man has drowned, he's been sitting there on the bottom for over 2 minutes!"

Mark

ps, jay, maybe you should try the forums newest feature
[SARCASM] your text here [/SARCASM] :eek:
 
S

SASpearo

Desk Driver
Dec 6, 2001
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Dive tank ...

It's a 7 m deep training pool for bubble blowers, 'inside' an outdoor shopping complex-type-thingy ... I used to play poker with the scubadoods in there, it's got several (6cm or so thick) windows to the outside world.... and it's right next to a coffee shop called Het Mannekin ... with the cutest waitressess you can think of. They will take my order through the window, after holding the menu up to the glass for a minute or so.

Of course, it would be toasted tuna mayo sarmies ... he he he ....

but maybe tungsten has got some other properties that make it unusable, like trying to machine it. SASpearo, you're the metal guru.

It's not that it's too difficult to machine, it is quite a mission. It's the fact that you rarely get tungsten in unalloyed form - it's fairly expensive. And in it's pure form it's brittle (apparantly - I've never played with pure Tungsten before)

I'd much rather go for some form of Titanium alloy ... it's cheaper than Tungsten. But why limit ourselves to metal? I know some good polymerists (Sounds like a dirty family secret ;) ) that might come up with a teflon / nylon breed that might be usefull ....

Hope U get yer fins soon !
 
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Griff

Griff

Certified SCUBA Rider
May 7, 2002
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good idea?

I know some good polymerists that might come up with a teflon / nylon breed that might be usefull ....

usefull for getting through airport security?:hmm
 
I

Iyadiver

Mr. Long Post
Apr 22, 2002
998
74
0
SA,


Is this good enough for a spearshaft, I mean strong and "springy" enough not to break ? Doesn't look too expensive. Imagine the end tip honed and sharpened to perfection, man we have a spearhead as sharp as a surgeon tool.




Tungsten Carbide/Cobalt
WC 94/Co 6

Diameter 6.35mm rod. Length 1500 mm.

Order Code
436-678-04 Price : British £ 60.00 1 pc British £ 86.00 2 pc


Tungsten Carbide is a hard, brittle ceramic which, when combined with 6% to 10% Cobalt, forms a tough Cermet (Ceramic-Metal). This material was developed for use in cutting tools, having hard ceramic crystals of a few microns in size within a ductile metal matrix. The resulting material can withstand the high compressive stresses imposed during cutting, as well as having good wear and oxidation resistance at the high temperatures reached. Tungsten Carbide/ Cobalt has a high resistance to thermal shock, so is able to withstand the rapid temperature fluctuations. Also, this has found a use as electrodes for Electrode Discharge Machining.


Electrical Properties
Volume Resistivity @25C ( Ohmcm ) 2x10-6


Mechanical Properties
Compressive Strength ( MPa ) 5300-7000
Hardness - Vickers ( kgf mm-2 ) 1550
Tensile Modulus ( GPa ) 600
Tensile Strength ( MPa ) 1440


Physical Properties
Density ( g cm-3 ) 14.95


Thermal Properties
Specific Heat @25C ( J K-1 kg-1 ) 200-480
Thermal Conductivity @20C ( W m-1 K-1 ) 60-80
Thermal Expansivity, 20-1000C ( x10-6 K-1 ) 4.6-5.0
 
S

SASpearo

Desk Driver
Dec 6, 2001
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Might be a little hard ....

The Vickers scale (I'll explain a little just now) is used to measure relative hardness - like most hardness tests. It is NOT, like most people think, always a good thing to have a very hard material. The way this works (in principle) is that the harder a material is, the smaller the crystals that forms the material. Which, in turn, makes it brittle. Having a 1550 on the vickers scale is a litlle to high imho - this is proven by the tensile strength - not a lot, once agin just my opinion.

The Vickers test uses a pretty nifty (although the technology is almost 40 years old) machine, that puts a ball - shaped load onto the material to be teted. You pre-stress the load, and then apply the final load, and by looking and comparing this microssopically you get a 'relative' hardness. In the days before Vickers, they used to file a metal / material, and if the material wore out, it was deemed 'soft'. On the other hand, if the file wore out, the material was deemed 'hard' ... how's THAT for simple??

The polymers would be strong enough - think of it this way: Kevlar is a polymer, interlaced by a honeycomb 'cloth', much the same way as fibreglass works. If that's not strong enough for you, hell, it's never gonna be strong enough. The main problem would more than likely be keeping the tip sharp - you won't be able to sharpen it yourself. The 'never-needs-sharpening' polymers is WAY too expensive to use for something as simple as a spearshaft. So, a slip - tip would more than likely be made out of Titanium or the like.

I'll go chat to a few techies, see what they think. It's been (urgh I feel old) 7 years since I studied mettalurgy / polymers. I'll need to refresh some memory here.
 
S

SASpearo

Desk Driver
Dec 6, 2001
515
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Re: good idea?

Originally posted by Griff
I know some good polymerists that might come up with a teflon / nylon breed that might be usefull ....

usefull for getting through airport security?:hmm

Uhm ... in a word .... Hell yeah. Especially if you're stuck with something as short as 20 or 30cm ... grin.
 
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Abriapnea

Abriapnea

New Member
Jan 16, 2002
678
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Hi Riaan...aah Kosi , Leven ... music to my ears :p
Might go back in March for the cricket World Cup ;) Will definitely let you know .Can probably organize some trips out of Sordies
 
S

SAFishShooter

Waiting for Summer!!!
May 28, 2002
72
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Hi

What would hapen if you looped the rubber underneath the gun ?
Wouldn't the recoil be canceled out ? This is just an idea. Not big into this engineering stuff.


Went spearing this weekend. didn't see any any fish. Water to dirty. Dive for 2 hours Have to take girlfriend back to her house.
Decide to take a different route than the one I came by. The water on the other side of the point was so clear you could see the bottom 10 m deep. DAMM. She didn't want to wait... Damn

Cheers

Reinier
 

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Griff

Griff

Certified SCUBA Rider
May 7, 2002
557
60
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something fishy here

Nick: SASpearo
real name: Riaan
Occupation: Computer Geek
Location: Cape Town

and

Nick: SAFishShooter
real name: Reinier
Occupation: Computer Geek
Location: Cape Town

these profiles look very similar. either there are a lot of computer programming Spearo's living in Cape Town with names of Afrikaans origin beginning with R, or SASpearo has created a ghost profile in order to compliment himself and score free karma.

interesting...
:D

Mark
 
S

SAFishShooter

Waiting for Summer!!!
May 28, 2002
72
17
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there are a lot of computer programming Spearo's living in Cape Town with names of Afrikaans origin beginning with R

I've got another buddy that is also a computer geek and name is Riaan and is a spearo. He's Riaan Niewoudt.
I work for EDS and SASPEARO\Riaan Coetzee works for Idion.

I'll post pic some day to prove it.
Cheers
 
S

SASpearo

Desk Driver
Dec 6, 2001
515
61
118
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Grin ...

Nick: SASpearo
Occupation: Jobless Computer Geek and Frankengun builder
Location: Pretoria

Anyway ....

Frankengun is taking shape at the moment .... I'm affraid to say that my old rusty trusty 65cm cavegun is taking the brunt of testing. I managaed to shoot a 20cm x 10mm bolt I made on monday straight into a concrete wall - it went in about 10 cm - and this on a single 20 mm RA rubber ...... you can guess what I've done so far .... but it's looking good.
 
I

Iyadiver

Mr. Long Post
Apr 22, 2002
998
74
0
Keep experimenting boy. Keep us updated, a new Steve Riaan Alexander is being born....:D :D I like it !!!!

How about Jack SA Prodo ?

How the hell did you make a 20 cm bolt glide down on the +- 50cm groove/track of ur 65cm cavegun without jumping out ??

10mm not that big Riaan, Gerald Lim u know uses 11mm something.


IYA
 
Griff

Griff

Certified SCUBA Rider
May 7, 2002
557
60
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Re: Grin ...

Originally posted by SASpearo
I managaed to shoot a 20cm x 10mm bolt I made on monday straight into a concrete wall - it went in about 10 cm

the owner of the wall must have been very happy

keep it up :)

Mark
 
S

SASpearo

Desk Driver
Dec 6, 2001
515
61
118
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First off ...

I used something that Markeroony of the infinite witt has come up with - a 'guide tube' if you want. I just went one further than mark and made it slide ... he he he.

I built a new muzzle, out of 'gasp' square tubing, just to prove that rollergun idea would work. I added some frills on like the guide at the front, and voila. It hasn't even got rollers. It's just two 12mm bolts welded to the square tubing .... the rubber was around 50cm ... and was doubled underneath the gun almost back to the handle - about 10cm short.

And no, my dad hasn't found the spear yet. And he never will. Amazing what you can do with an angle grinder, some masonry discs and some polly filla and paint in 20 minutes :D

BTW, I'm going down to 7 or 8mm shafts now, and up to around 65cm length, I've had another idea .... will work on it over the weekend, you guys might enjoy it. Let's just say I'm building myself a .44 Magnum ... at least it's gonna look like it !!

Oh, and Mark ... guess which finger I'm waggin here ... :naughty :naughty :naughty :naughty :naughty :naughty :naughty
 
icarus pacific

icarus pacific

Human-in-training
Nov 7, 2001
2,880
212
0
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yeah.

Yeah, concrete walls all over the World are crappin' their pants.:hmm

sven
 
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Amphibious

Amphibious

Working Class Spearo
Mar 17, 2002
2,775
300
0
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Not a Frank'n gun per-say...

Years ago when I was but a tadpole doging bullets in the Arabian Gulf, some Philipino spear fisherman made a wicked little rig that fired 14" welding rods. looked like a ghetto crossbow, but with a much shorter spread.

WAS SO MUCH FUN! hunting little panfish and such in shallow water.

anyone ever made anything for the tiny fish?

Willer
 
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