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We need to launch sandwiches! Baby ones that is.. its an 8" sandwich cut into 3rds, about 2.5" wide x 3" tall, they are wrapped in paper and can't explode! Similar to Tshirt launching cannons. Budget for materials is $300, deadline is 2-3 weeks. Looking for any and all help with advice, materials, blueprints, and ideas.. and will compensate if this thing gets cleared for the event. Thanks guys!
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how far do you want it to go ?
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I can make a combustion cannon for the sandwiches, that way they can be toasted before landing in the laps of your hungry audience.
My advice is to use a larger chamber than normal and lower pressure with a high flow valve such as a 2 inch sprinkler, butterfly, or ball valve.
The reason for this over a small high pressure chamber and small valve is to reduce damage of the launched sandwitch.
For example my Marshmallow cannon with the 3 foot tennis ball barrel will toss shirts 200 feet into the stands. The initial acceleration is high, but quickly drops off due to the small chamber and 1 inch valve restriction. Moving to the 2 inch cannon with the large tank can do the same distance shot on less than 30 PSI, but the acceleration is more spread out along the length of the barrel as the flow doesn't drop off rapidly.
With your budget and time limit, pick up a 2 inch sprinkler valve, modify it, build a 4 inch chamber 3 feet long and add a 3 inch barrel about 3.5 to 4 feet long. Use 15-30 PSI depending on distance needed.
Due to the difficulty in obtaining pressure rated 4 inch PVC and fittings, 4 inch ABS Cellular Core DWV pipe is recommended. See my ABS cannon in my sig regarding pressure in this DWV pipe. It does not explode like PVC. PVC, even pressure rated is not rated for air pressure due to it's failure mode.
This cannon should be able to be completed for less than $200 not counting support gear such as a paintball tank and regulator or compressor.
Edit, a good mod would be a breech load for rapid deployment of sandwitches when using a CO2 beverage tank or 40 CU ft Nitrogen tank and regulator. The launcher in the video is using a 3 gallon tank, a 3 inch barrel 4 feet long, and a Nitrogen tank and regulator for supply. This shot in the video is at about 35 PSI. High flow rocks.
Last edited by Technician1002 on Mon Nov 01, 2010 5:08 pm, edited 3 times in total.
and, crucially, do you want the sandwiches to arrive intact on landing?
What will be in the sandwich? That would vary the impact results
An onager type thing (SP?) might be better for the job.
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Google the sponsor of the event. They are deli sub sandwitches.
I can't believe I'm saying this, but just use a ball valve. You don't want sandwiches to be exposed to several hundred gee's that a modded sprinkler valve or QDV would accelerate it with.
With 100 psi and a 2.5-3" barrel even a 3/4" ballvalve should work. A 3 foot barrel should let you use fairly low pressure.
(I've used a 1/2" bvalve on a 1.5"x2' barrel, for comparison. It will send a potato perhaps a hundred yards.)
In regards to the several hundred gee's, at low pressure this is controllable. At one event I was tossing unbroken raw eggs over 200 feet. Low pressure, high flow, and a long barrel will get a raw egg up to some pretty wicked speed without breaking it. A sub sandwich can be tossed with the same care.
I must admit the sudden deceleration at the far end was more damaging to the eggs than the launch.
A largeish, low pressure ABS pneumatic seems like the best bet. The large volume means less Gs for a given velocity, with the low pressure contributing to this gentle acceleration.
The use of low pressure means that the ABS will not fail under any normal use, and any minor abuse such as knocks and drops again shoudln't be nearly as dangerous as they would be with a high pressure PVC cannon. I'd be very wary of using anything approaching high pressure in anything but a full metal cannon, as I assume it's likely to see some somewhat rough handling.
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Thanks for all the help guys.. I'm going to be trying to put this thing together in the next 2 weekends.
I'm hoping we can toss the samples a few hundred feet, it will be on a football field so it would be nice to get them up into the stands.
Technician1002, where would you recommend purchasing the DWV pipe from?
And if anyone can help on a rough parts list that would really help me at least know where to get started. And I'm hoping a power saw and power drill are really the only tools required right?
Look for ABS Cellular Core pipe in a Home Improvement store such as Home Depot or Lowes. The Black sewer pipe in the larger stuff is it. Look for 4 inch for your chamber and a cap and reducer. Reduce to 2 inch. Add fittings to fit your valve, a fill valve, a gauge, and you are done on the chamber end. A 3 inch piece for a barrel and reducer to fit the valve and you are done.
Use the right cement. Don't use PVC cement and primer on ABS. Use ABS cement only.
Were you able to find a 2 inch valve?
A couple hundred feet is within reach.
Rough parts list mostly from the breech to the muzzle
1 can of ABS Cement
1 4 inch ABS pipe cap (If you can't find a cap, use a coupling and plug)
1 4 inch to 2 inch ABS reducer
1 short section of 4 inch ABS Pipe
1 Tire valve ( or other suitable fill arrangement )
1 pressure gauge
1 short piece of 2 inch ABS pipe
2 Male 2 inch threaded adapter (to fit the valve)
1 2 inch threaded sprinkler valve
1 blow gun ( to modify the valve
1 1/4 inch close nipple ( to attach the blowgun to the valve )
1 short section of 2 inch ABS pipe
1 3 inch to two inch adapter
1 short section of 3 inch ABS pipe for the barrel
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Last edited by Technician1002 on Sat Oct 30, 2010 5:33 pm, edited 1 time in total.
While the ABS whould be safe for this purpose, if you ever feel like shooting something else out of the cannon I wouldn't want to take the pressure too much higher.
Finding 4 inch pressure rated PVC parts in a local big box home improvement store is not likely. ABS is much easier to find. Often you can buy short lengths instead of the entire 10 foot length of pipe. 2 or 3 feet lengths can save money if that is all you need.
Last edited by Technician1002 on Sat Oct 30, 2010 5:57 pm, edited 1 time in total.
I imagine pressure rated ABS is quite hard to find over there (unlike for me ), I just wouldn't recommend anyone taking a DWV cannon much higher than 80PSI or so. I'd be worried about the socket depths on DWV fittings more than anything else.
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