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 Post Posted: Tue Jul 22, 2003 12:00 am 
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Originaly posted by taimaishu1103,
If one were to modify Cchant's PVC projectile to contain a medium-grade model rocket engine (B-size maybe) by wedging one inside the pipe, one could replace the electric ignitor for a potassium perchlorate plug which would ignite upon combustion of the cannon. The momentum attained from the explosion along with the sustained acceleration by the rocket engine firing could lead to extreme velocities (perhaps supersonic with a d or e engine!!!)

a vertical range of 1500+ meters would be very easily attained. A horizontal max range could be well beyond 1000 yards. HEHE this sounds good.......


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 Post Posted: Tue Jul 22, 2003 12:00 am 
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Originaly posted by Rex_R,
using mini-engines and conventional model rocket build (with sabot). have to buy some supplies. wouldn't want to be under a 'spudrok' on its way down. one problem is making sure the spudrok is stable before you launch, an unstable non-powered projectile is not a big prob, one that is powered can be nasty as the center of mass changes as the engine burns its fuel. you really don't want a rocket suddenly getting stable when its pointing at you with the engine still producing thrust


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 Post subject: Re: rocket stability
 Post Posted: Tue Jul 22, 2003 11:00 am 
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Originaly posted by taimaishu1103,
Hmm, well the problem is that you need to impart a spin on the rocket to reduce the effect of an lopsided center-of-gravity. you could do this with fins, but those are a bich and a half.

Possibly, you could get Joel to make a Sch80 2 inch rifled barrel. If you made the rocket out of 1 1/2 sch80, it is a near perfect fit (only a .0065" space between the rocket and barrel) The rifling should impart a good enough spin on the rocket for it to become stable.

I thought rockets would be farely stable if launched from a spudgun. Think about it, if you made a good enough ignition plug (potattium perchlorate plug) the rocket would ignite almost immediately, so porobably several inches down the barrel. It would be trapped on both sides bythe barrel so it would be very well stabilized. This meqans whenit leaves the barrel it should be flying almost perfectly straight, and any difference in center of gravity by this point probably cant overcome air resistance, so the rocket will continue in a straight path.


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 Post subject: SCH80 rifled
 Post Posted: Tue Jul 22, 2003 12:00 pm 
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Originaly posted by andeh,
http://www.spudtech.com/detail.asp?id=10

Also, you wouldn't need sch80 1.5". All 1.5" PVC has the same OD, its the id that changes. Thinwall would produce the highest muzzle velocities, while thick SCH80 would produce the highest amount of energy. I'd guess 1.5" SCH40 would be ideal, but I don't know much about rockets and such. Testing would be the best thing to do first I suppose.


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 Post subject: About 1.5" sch80
 Post Posted: Tue Jul 22, 2003 1:00 pm 
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Originaly posted by taimaishu1103,
If you look at the harvel plastics sch80 pvc specifications, the OD is greater than the sch40 variant. The OD and ID change when you go from sch40 to sch80. 1.5"sch80 and 2"sch80 are a perfect match, soooo perfect : )


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 Post subject: About 1.5" sch80
 Post Posted: Tue Jul 22, 2003 1:00 pm 
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Originaly posted by taimaishu1103,
If you look at the harvel plastics sch80 pvc specifications, the OD is greater than the sch40 variant. The OD and ID change when you go from sch40 to sch80. 1.5"sch80 and 2"sch80 are a perfect fit, soooo perfect : )


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 Post subject: They shouldn't..
 Post Posted: Tue Jul 22, 2003 1:00 pm 
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Originaly posted by andeh,
My 2" SCH80 fits SCH40 fittings..


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 Post Posted: Tue Jul 22, 2003 2:00 pm 
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Originaly posted by taimaishu1103,
ok, all pipe, sch80 or sch40 has the same OD relative to the size. However, sch80 has thicker walls, so the ID of sch80 is smaller. Therefore, a 2 inch sch80 will fit in the same fitting as a sch40, however, its 1.91" ID fits VERY tightly around a 1.9" OD sch40 OR sch80 pipe.


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 Post Posted: Tue Jul 22, 2003 9:00 pm 
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Originaly posted by andeh,


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 Post subject: Onboard Propulsion
 Post Posted: Wed Jul 23, 2003 12:00 pm 
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Originaly posted by cchant,
I've thought about putting a rocket engine in one of these projectiles a while back. No doubt, they would probably be the coolest thing to ever leave a piece of PVC. I was thinking about having a cheap mechanical switch that would be activated during the inital firing that would start a timer for a couple seconds. Then once the rocket in well on it's way in the air, the engine kicks it and it really takes off. You'd probably need some kind of fins for stability there.

I was planning to shoot these just barely sub-sonic (I know, it would have been a big gun) because of ballistic problems with the sound barrier, but even at that velocity, a probable range is between 1 and 2 miles. WITH a rocket, you could add at least another half a mile or mile, maybe more. I don't have much experience with horizontal rockets so I don't have a good estimate on range. But again, I'll probably never be able to test anything like this because I don't have access to 2 miles or more of flat, open land.


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