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| cfrehr |
 Posted: 06/22/2008 7:52 AM Post subject: Spud Shot Distance |
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Private
Joined: 21 Jun 2008
Posts: 2
14.13 Spud Bux
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| hi, i want to build a spud gun with a chamber made of 4" pvc 5 feet long, converting to barrel of 2" pvc 10 feet long.....shooting a potato and using hairspray as fuel, how far do you think my potato would go???
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| bigbob12345 |
| Posted: 06/22/2008 8:40 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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Why didnt you just post this in the other topic?
But you still didnt provide enough information. Chamber fan? What are you using for ignition?
But I would expect the potato to go roughly 150-200yards but that is probably overestimating.
There are ballistics calculators out there that would give a more accurate answer.
And I would highly reccomend you cut your chamber down to 2ft and keep your barrel the same...that would give you a nice C:B
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| SpudFarm |
| Posted: 06/22/2008 9:57 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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bob: his ratio is 1:1.. (i atleast think so)
i think it will get about 300yards if you put some effort into it.
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| bigbob12345 |
| Posted: 06/22/2008 10:18 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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| Quote: | bob: his ratio is 1:1.. (i atleast think so)
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4in pipe does not have twice the volume of 2in pipe, it has about 4x the volume.
4in pipe has an ID of 3.998, so 3.998/2=1.999.....1.999*1.999=3.996
3.996*60(in)=239.76*3.14=752.846ci
2in pipe has an ID of 2.049, so 2.049/2=1.0245....1.0245*1.0245=1.0496
1.0496*120(in)=125.952*3.14=395.489ci
which gives a ratio of 1.9:1, not excactly ideal
but shorten that chamber two 2ft and look what happens.
3.996*24(in)=95.904*3.14=301.138ci
And it comes out with a ratio of 0.76:1, ideal
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| SpudFarm |
| Posted: 06/22/2008 10:22 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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oh dude..
i allways talk before i do the maths 
what he can do is make the barrel longer and keep the chamber and get more performance
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| bigbob12345 |
| Posted: 06/22/2008 10:26 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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| spudfarm wrote: | | what he can do is make the barrel longer and keep the chamber and get more performance |
Im not sure that he wants a 20ft barrel 
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| SpudFarm |
| Posted: 06/22/2008 10:29 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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i uses it 
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| bigbob12345 |
| Posted: 06/22/2008 10:34 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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Doubt its much fun to lugg around though 
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| SpudFarm |
| Posted: 06/22/2008 10:36 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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| not that bad if it is of PVC so you can acctualy lift it by your self
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| bigbob12345 |
| Posted: 06/22/2008 10:41 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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just out of curiousity...How heavy is your hybrid barrel(in lb's)?
If he put together a gun with a 5ft 4in chamber and a 20ft 2in barrel it would weight around 100lb's or more. Im thinking cfrehr's gun wont be a handheld 
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| starman |
| Posted: 06/22/2008 10:54 AM Post subject: Re: Spud Shot Distance |
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Big Daddio
Joined: 11 Dec 2007
Posts: 1755
3637.09 Spud Bux
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| cfrehr wrote: | | hi, i want to build a spud gun with a chamber made of 4" pvc 5 feet long, converting to barrel of 2" pvc 10 feet long.....shooting a potato and using hairspray as fuel, how far do you think my potato would go??? |
If you're planning to shoot spuds only, you're wasting your time and materials on such a large gun. If the potato doesn't vaporize, you won't get significantly more distance than if you built a more standard size. Also, if you did use a chamber that big, you should put a fan or 2 in there just to circulate the fuel evenly.
Consider scaling things down to say a 2' chamber and 5' barrel. That's still considered a large gun and it will be much more portable....and you'll get the same distance performance with a potato...and a respectable 1.6:1 c:b ratio.
Last edited by starman on 06/22/2008 10:58 AM; edited 1 time in total |
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| SpudFarm |
| Posted: 06/22/2008 10:54 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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60 kilograms = 132.277357 pounds
i bet the PVC barrel is lighter than you said
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| bigbob12345 |
| Posted: 06/22/2008 10:59 AM Post subject: |
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Experienced n00b
Joined: 01 Dec 2007
Posts: 1515
370.57 Spud Bux
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Wow, quite heavy.
I bet it weighs atleast 200lbs with a the chamber and fuel meter and everything attatched though.
And I meant the entire PVC gun put together including the chamber.
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| SpudFarm |
| Posted: 06/22/2008 10:59 AM Post subject: |
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Hybrid Guy
Joined: 04 Nov 2006
Posts: 2094
1180.73 Spud Bux
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| ok. but we stop talking about this. i talk to you on msn
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| jimmy101 |
| Posted: 06/22/2008 13:57 PM Post subject: |
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Major General
Joined: 28 Mar 2007
Posts: 1762
7467.36 Spud Bux
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| bigbob12345 wrote: | ...
which gives a ratio of 1.9:1, not excactly ideal
but shorten that chamber two 2ft and look what happens.
3.996*24(in)=95.904*3.14=301.138ci
And it comes out with a ratio of 0.76:1, ideal |
Yes, and the 0.76 CB gun will probably have a lower muzzle velocity than the 1.9 CB gun, if the spud survives. HGDT says (guessed at some things about the gun) the 1.9 CB gun will have a muzzle velocity of 670 FPS, the 0.76 CB gun 520 FPS.
If you want to increase the performance of the gun it needs a longer barrel. Making the chamber smaller will decrease performance.
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