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A place to ask general spud cannon related questions.
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Unread postAuthor: KineticAmbitions » Sat Aug 15, 2009 4:39 pm

But I was remembering this lecture a cop gave me as a juvenile about some kid who had put a pipe b*mb inside one, electrically ignited it,
got hit in the head with a cinderblock chunk and was drooling and wears a helmet all the time...


Are you sure he wasn't drooling and wearing a helmet before he did that? Because that's quite the level of mental retardation you're talking about there...

Lets keep the smart level down shall we?


That sounds more than a little dangerous, given the discussion topic. A rephrase, perhaps? :lol:

I have a question for Pat: How were you stabilizing the nail for flight? Did you cut slots into the back to fit fins, or did you just drill out a large amount of material from the back of the nail? I can't think of how you'd make it work without using a lathe, if the nail's diameter was 1/4" smaller than the bore, and I can't think of why you'd use a nail if you had a lathe.
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Unread postAuthor: pat123 » Sat Aug 15, 2009 6:00 pm

The nail was about 3/8" diameter. I got it at lowes. I used a sabot made out of aluminum foil and it worked fine(except for one shot where the foil went around the nail and the foil went through one sheet of plywood. :shock:)
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Unread postAuthor: c11man » Sun Aug 16, 2009 9:59 am

Ragnarok wrote:
c11man wrote:So I think you have a slight math problem.

I could say the same of the number you churned out.

You shouldn't give an answer to more significant figures than the inputs. One s.f. more is acceptable in some cases, but still questionable.

... you gave an answer of 6 s.f. more than the inputs.


i just copied the figure that my spreadsheet gave me. is .73inches better for you? or do i have to go realy far and just say 1inch to make you happy?
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Unread postAuthor: Ragnarok » Sun Aug 16, 2009 10:39 am

c11man wrote:Is .73 inches better for you?

Yes, because it's of a valid 2 significant figures.

Or do I have to go really far and just say 1 inch to make you happy?

No, that would just be plain wrong. I'm talking about significant figures, not decimal places.
0.73" is perfectly valid, 0.7" would be valid (if losing precision it could have), but 1" certainly wouldn't be.

Mr.Sandman wrote:Let's keep the smart level down shall we?

If anyone finds basic mathematical principles which I was taught before my age had even advanced into double figures too smart for them, might I suggest they're in the wrong hobby?

I should warn you, spudguns may contain small parts, and should not be given to unsupervised children under 36 months, due to risk of choking.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: c11man » Sun Aug 16, 2009 11:08 am

rag, i was just kidding about the 1inch. you just have to be as precise as is called for in the problem
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Unread postAuthor: Ragnarok » Sun Aug 16, 2009 11:31 am

c11man wrote:rag, i was just kidding about the 1inch.

I'm aware. I just chose to treat it as if you weren't.

Also, I needed enough to make up a post - else I wouldn't get to do my "Spudguns may contain small parts" bit.
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Unread postAuthor: c11man » Sun Aug 16, 2009 1:10 pm

damit rag, stop being so tricky! (maybe i should stop being clueless)

anyway back on topic, so the chamber was 2 feet of 1.5inch sch 80 inside of 2inch? and just a single igniton with no fan? guessing map too
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Unread postAuthor: velocity3x » Tue Aug 25, 2009 11:03 pm

pat123 wrote:estimated 2000ft/Lbs and 400fps with a 19oz 10" long steel nail.


I'm confused about your projectile. A 10" x .375" nail contains approximately 1.1 in^3 of steel. Mild steel weighs about 4.44oz per 1in^3. The nail you fired weighs substantially less than 19oz. It weighs approx 4.8oz.

A 4.8oz nail at 400fps = approx 745lb/ft

If you had in fact launched a 19oz projectile at 400fps, it would have generated about 2,950 lb/ft of energy.
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Unread postAuthor: c11man » Wed Aug 26, 2009 9:37 am

this has already been covered, he did NOT fire a 19oz projectile
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