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a barel that goes inside the chamber

A place to ask general spud cannon related questions.
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a barel that goes inside the chamber

Unread postAuthor: LosBuenos » Sat Mar 10, 2007 7:22 pm

how do you do that thing where the barrel comes down to the bottom of the chamber where you put the fuel in?!? it looks cool and useful. please help me! :cry:
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Unread postAuthor: LosBuenos » Sat Mar 10, 2007 7:22 pm

muzel loading takes too long!
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Unread postAuthor: Hotwired » Sat Mar 10, 2007 7:31 pm

You're talking about a coaxile but I've never seen one used for combustion.

I think you actually mean you want breech loading?
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Unread postAuthor: willarddaniels » Sat Mar 10, 2007 8:20 pm

please help us help you...
draw a picture or do a thorough search on the matter (google or browse on spudfiles / wiki) and please try to explain a bit better. Use the keywords provided by Hotwired to do your search.
Coaxials are used all the time in combustions... rarely in hybrids.
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Unread postAuthor: experament-u2 » Sun Mar 11, 2007 1:25 am

i think he is talking about somethig like this

Image
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Unread postAuthor: fom » Sun Mar 11, 2007 1:27 am

I think hes talking about breech load, search if you want to know how.
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Unread postAuthor: Killjoy » Sun Mar 11, 2007 1:32 am

Joel at spudtech made a combustion coaxial launcher as i recal....
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Unread postAuthor: LosBuenos » Sun Mar 11, 2007 1:43 pm

yeah i'm talking about what experament-u2 said. like, when you open up the clean out cap and the barrel is right there. do you have to take something off of the adapter part to make the barrel go all the way through?
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Unread postAuthor: A-98 » Sun Mar 11, 2007 2:11 pm

yes, you have to file/sand/dremel off the "stop" inside of the reducer.. the "stop" is a ridge of plastic inside the fitting that stops the barrel from going thru.
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Unread postAuthor: LosBuenos » Sun Mar 11, 2007 2:56 pm

thank you so much a-98. :P does the reduced size of the chamber also reduce the power of the cannon? :?:
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Unread postAuthor: noname » Sun Mar 11, 2007 3:00 pm

It'll be fine, just measure the volume and make it bigger. For a regular hairspray/WD40/deodorant combustion, a 1.5:1 ratio is optimal.
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Unread postAuthor: LosBuenos » Sun Mar 11, 2007 3:10 pm

is the ratio different for propane?
:? sorry for all these questions. i think i'm finished
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Unread postAuthor: A-98 » Sun Mar 11, 2007 4:33 pm

i believe its .79:1, but ill check the wiki
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Unread postAuthor: Bluetooth » Sun Mar 11, 2007 4:56 pm

There is no certain ratio, 1.5:1 is for the most power (according to Burnt Latke) and I believe its .8:1 for the most efficient.
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Unread postAuthor: Pete Zaria » Sun Mar 11, 2007 4:57 pm

.8-1:1 is considered optimal for a metered propane/mapp gas gun. However, I lean towards the chamber-heavy side. It can't reduce performance, it just wastes extra power (because the barrel isn't long enough to harness the excess energy from the combustion chamber) and makes more noise. .8:1 is supposedly the most efficient. I like things to go boom, so I tend to go for closer to 1.5:1.

When measuring the chamber volume, calculate the volume of the outer (chamber) pipe, then calculate the volume of the length of barrel that will be inside the chamber, and subtract that volume from the chamber volume. Here's a handy "volume of a cylinder" calculator: http://www.online-calculators.co.uk/vol ... volume.php

I'd definitely use multiple spark gaps or one long spark strip in a coaxial combustion. An 80mm fan probably won't fit between the chamber wall and barrel, so you might need to find a couple smaller fans - like the ones off of a graphics card or chipset cooler. I'd just use several small fans on one circuit....

Good luck with this project. Keep us informed and give us pics when you can.

Peace,
Pete Zaria.
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