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Need Help Persuading ASME

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Need Help Persuading ASME

Unread postAuthor: rcman50166 » Fri Aug 14, 2009 10:52 pm

Hey all, been a while since I've posted. Anyways I need help persuading ASME (The American Society of Mechanical Engineers) New Haven chapter to build a pumpkin cannon as opposed to a pumpkin trebuchet. What points should I bring up? This is my argument as far as now goes:

rcman50166 wrote:Well me and Ken have discussed this via e-mail already. My vote is for a cannon. I know more about that than trebuchets/catapults/ballistas.

I support my decision with size as well. The trebuchet will be very large and heavy. What I see in my mind is having a close to 12 ft throw arm which means the base needs to be around 6ft tall, 12ft long, and 12ft wide at the least. We would definitely need the trailer to haul the monster. If made of wood I don't see how we are going to move it around either. Wheels are an option but we still need to get it out of the shop somehow once built. A cannon on the other hand is relatively small. It would have a 10 ft+ barrel but can be taken apart in smaller sections. The width and height would be a minimal issue. This would make it easily transportable.

Another issue brought up is safety. Both machines have its dangers. The trebuchet is large and heavy. It has a giant throw arm that has a long projected travel. Along with this it has a counterweight that will probably be close to 200+ lbs. The cannon does not have any exposed moving parts but it would be under pressure. A bit under 300psi. The only threat with this is not an exploding chamber, most pressure rated vessels have a safety factor close, if not exceeding 2. The main issue is an exploding barrel. If the barrel isn't perfectly straight the mass of the pumpkin traveling down it would whip the barrel causing it to shatter.

I have a few plans for the cannon if it is decided to be used. But that can be discussed another time
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Unread postAuthor: inonickname » Fri Aug 14, 2009 10:57 pm

As a point, I wouldn't bother arguing about size in relevance to punkin chunkin. Even the smallest possible cannon will be huge.

I'd talk about safety (you sort of have), performance and aesthetics. I assume cost isn't that much of an option. Also, you could show some plans that will blow their socks off.
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Unread postAuthor: THUNDERLORD » Fri Aug 14, 2009 11:05 pm

...What points should I bring up? This is my argument as far as now goes:...


Tell him to build his "trebuchet" while you build the cannon and then engage in a pumpkin battle. :P
Personally I'd feel little or no threat on a "trebuchet"'s business end... :twisted:

Seriously the inaccuracy, weight issues and release mechanism of the trebuchet seem more dangerous than a pneumatic cannon IMO.
You brought up goos points it seems. 8)
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Unread postAuthor: rcman50166 » Fri Aug 14, 2009 11:11 pm

Well lets try to brainstorm the pros and cons of each under the following categories:

price
size
safety
construction materials
build time
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Unread postAuthor: inonickname » Fri Aug 14, 2009 11:41 pm

Pro: You have a slight chance of winning with a cannon.
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Unread postAuthor: Moonbogg » Sat Aug 15, 2009 12:08 am

Well performance isn't a valid thing to bring up as they both would enter under their own categories. Talk about how you feel that there is more room for improvement in the cannon area than the trebuchet and you feel your team can exploit that and increase the team's chances of winning in the cannon category rather than in the trebuchet category.
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Unread postAuthor: THUNDERLORD » Sat Aug 15, 2009 12:53 am

rcman50166 wrote:Well lets try to brainstorm the pros and cons of each under the following categories:...


-price: Donated, scrap, salvaged parts(?) (Dang, I found a large welding tank but I got too much junk already)

-size: a cannon could be designed for take down and no matter what size will give better range than an equal size/weight trebuchet (IMO).

-safety: the trebuchet is inaccurate, even shooting backwards at times, large swinging parts (that are also under pressure stress), has cables that can snap or fly loose, trickier triggering, more pinch-points/smash-points...and more dangerous to transport/set-up as well etc.

-construction materials: I much prefer working with metal over the PITA woodwork can be. and a trbeuchet needs plenty o'metal and cable parts.
(Seems like there are far more modern engineering materials on a cannon too).

-build time: It seems like it would be much more smooth going from a well designed pumpkin cannon to assembly than the bugs to work out on a trebuchet.

BTW, maybe you could rocket sled the pumpkin...like a tray and a nitrogen or helium tank behind the pumpkin and knock the valve off the cannister...My late, late night idea anyway...
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Unread postAuthor: D_Hall » Sat Aug 15, 2009 12:54 am

As an organization, the ASME's bread and butter is pressure vessels. What does it say about the ASME if it chooses the option that avoids the technology that it is supposed to be The Authority on?
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