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ME1-05H Stand w/ elevation adjustment.

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: Ragnarok » Wed Dec 23, 2009 3:32 pm

McCoytheGreater wrote:However 6' > 6'2".

Gorram it, you've broken maths.

~~~~~

Six foot somehow being more than six foot two aside, that is one beastly large cannon.
How exactly did you manage to measure the chamber volume to two decimal places though?
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: McCoytheGreater » Wed Dec 23, 2009 5:46 pm

Very very carefully. It should be 1492 +/- 3. theLesser figured it up for us. We're just sitting around waiting on the epoxy to cure before the spark gap gets tested and mounted. As to Artillerycreation's question, we are using clean out caps. We're modifying the end cap in the T to hold a chamber fan about 8 inches inside the T. Our propane inlet is mounted on the T. More stuff coming soon.
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Unread postAuthor: artillerycreations » Wed Dec 23, 2009 5:56 pm

Are you worried about blowing out the cleanout caps. I did it on my 6 inch chambered gun. It uses about 50 inches of 6 inch pipe and a 15 foot 3 inch barrel. Thank god i used small hex bolts to make electrical connections from inside the chamber to outside the chamber rather than just wires. The gun blew up and shot pieces of the cap and fan 10 yards into a brand new shed and made marks in the sheet metal. I dont want that to happen to you because i was lucky nobody was behind it. The shock wave that ensued after the mishap was really intense.
Your not planning on using a DWV cleanout are you? I havent ever seen a 6 inch pressure rated cap.
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Unread postAuthor: McCoytheLesser » Wed Dec 23, 2009 6:41 pm

The cleanout cap says "DWV" but it is schedule 40, along with the rest of the gun and schedule 40 is rated at 180 psi working pressure. None of the fittings or pipe are thin wall or cellular core. We won't have a problem with this gun. I look at it like this... I'd much rather an $8 endcap blow out than a fitting break and us be out of $200.
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Unread postAuthor: McCoytheGreater » Wed Dec 23, 2009 6:48 pm

Or at least we shouldn't have a problem with this gun. We figure the most problematic part will be having to assemble/disassemble all the parts that go with it. There's a tripod base, and a trough with our recoil adapters on it. If anyone has better suggestions that springs or pneumatic door closers for recoil absorbers, pleas speak up now. We can spare one more day. On a side note, progress has halted for a while. Our soldering iron has broken (it could be a sign), so we are unable to continue til we get a new one. The next phase of construction will be installing the chamber fan, spark gap (which has been tested and works like a dream!), and T fitting. supports and barrel attachment after that.
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Unread postAuthor: artillerycreations » Wed Dec 23, 2009 7:24 pm

McCoytheLesser wrote:The cleanout cap says "DWV" but it is schedule 40, along with the rest of the gun and schedule 40 is rated at 180 psi working pressure. None of the fittings or pipe are thin wall or cellular core. We won't have a problem with this gun. I look at it like this... I'd much rather an $8 endcap blow out than a fitting break and us be out of $200.


I conpletely agree with this statement. A sacrifical part is great to have in a gun so that if it blows, it does so (hopefully) in a way you have designed into it. I am just saying that it has happened to me when i got the propane mix just right and i have a feeling it wasnt just one bad cap. I wanted to warn you because if anyone was standing directly that cleanout if and when it blows, a trip to the ER will be paramount, that is if the ambulance can make it there fast enough. Safety first. The less bad publicity spudding gets the better.
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Unread postAuthor: SpudBlaster15 » Wed Dec 23, 2009 7:37 pm

McCoytheLesser wrote:The cleanout cap says "DWV" but it is schedule 40, along with the rest of the gun and schedule 40 is rated at 180 psi working pressure.


SCH40 is only a measure of wall thickness, not a pressure rating. Cleanout caps are usually not rated.

Personally, I have only had one fail, but I have strayed away from using them on metered fuel cannons. A threaded adapter/solvent weld endcap is a much stronger setup.

A properly constructed cannon should not need a weak point.
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Unread postAuthor: artillerycreations » Wed Dec 23, 2009 7:41 pm

SpudBlaster15 wrote:
McCoytheLesser wrote:A properly constructed cannon should not need a weak point.


I agree, but for me knowing where it will blow if it does is a nice feature, especially with large cannons where when conditions are just right, forces in the chamber can be massive.
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Unread postAuthor: jimmy101 » Wed Dec 23, 2009 9:38 pm

McCoytheLesser wrote:The cleanout cap says "DWV" but it is schedule 40, along with the rest of the gun and schedule 40 is rated at 180 psi working pressure. None of the fittings or pipe are thin wall or cellular core. We won't have a problem with this gun. I look at it like this... I'd much rather an $8 endcap blow out than a fitting break and us be out of $200.

McCoytheLesser

It is important to learn exactly what "schedule" means. It has nothing to do with the pressure rating. An SCH 40 part could be rated to 200 PSIG or it could be rated to 10 PSIG.

There is no pressure rating associated with SCH 40.

Cell core PVC is unrated for pressure but is still SCH 40.

All the schedule really means is that the pieces will fit together. All SCH 40 PVC pipe will fit into all SCH 40 PVC fittings. The pipe and fittings can come with different pressure ratings even for the same nominal dimension and type of part.

Pressure rated fittings and cell core "DWV only" fittings are both SCH 40. Only the pressure rated fittings are actually pressure rated (duh).

Sure looks to me like you've got several DWV only parts in the build.
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Unread postAuthor: McCoytheGreater » Wed Dec 23, 2009 10:10 pm

The only dwv parts we have are the end caps. Everything else is pressure rated from a pipe supply company. All the fittings and pipe came from recommendations from these guys...and they know pipe.

Gonna go finish the chamber now.

Pics to come!
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Unread postAuthor: artillerycreations » Wed Dec 23, 2009 10:35 pm

Im pretty sure if your cannon has any respectable power for its size its gonna blow those cleanout caps to pieces. Mine sure did in a hearbeat.
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Unread postAuthor: McCoytheLesser » Thu Dec 24, 2009 2:59 am

Just finished the chamber! The spark strip and chamber fans are in place and tested (I know the spark strip works because of the fireball that came toward me :D. ) All theGreater and I have to do is build the stand and carriage assembly, then glue in the barrel. Pics of the spark strip to come in the morning :)
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Spark Gap

Unread postAuthor: McCoytheGreater » Thu Dec 24, 2009 3:35 am

So here's a pic of the spark gap firing as well as the chamber with the T fitting installed. Would've saved this post till in the morning, but it already is morning. I just haven't gone to sleep yet. And it's a ballin' ass picture. With every new piece that goes on the cannon, the scale of this project becomes more and more real. It's friggin huge!
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Attachments
phpEZzFIcAM.jpg
Here's the spark gap firing in all her three sparkish glory.
phpZuMKf0AM.jpg
And the"slightly"Lesser. Yeah. It's a big build.
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Unread postAuthor: SpudBlaster15 » Thu Dec 24, 2009 4:13 am

Looks good; that's the same spark strip design I used on my first* advanced combustion launcher. It definitely works well.

*It was eventually used on the first chamber of said gun, but not the first version.
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Unread postAuthor: McCoytheGreater » Thu Dec 24, 2009 4:29 am

It's the first time we've used this design in any of our combustion guns. Normally we'd use a piezo igniter. We were fairly impressed when we saw that particular design simply because not only did it look easy to make, it also looked quite effective.
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