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long range ammo MiniBoy Mark I

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: ramses » Tue Jul 12, 2011 7:56 am

I got 1700 PSI to open with 300psi in the pilot. This makes no sense. A leak into the pilot would only keep the valve from opening. A leak out the barrel would do very little.

I'm still thinking.
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Unread postAuthor: LeMaudit » Tue Jul 12, 2011 10:59 am

Finally got off my ass and sanded down the sabot to fit the barrel.

8)


At the same time I inspected my piston, what a mess! Shocked
Sealing face is a bit munted.
Washers are a bit bent and one is loose.


Nah nah nah ...
The ploy : "jeez my canon is broken I cannot fire the MiniBoy sorry'bout that..."
... is way too obvious :wink:
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Unread postAuthor: MrCrowley » Tue Jul 12, 2011 10:23 pm

I did say it should work once I put it back together :P
I've been trying to keep my distance from MiniBoy, trying not to play with it so I can disassociate myself from it and shoot it without feeling sad :D


Edit: Although the back washer for the front o-ring is loose and allows some 'play' for the o-ring, I'm thinking it will just make it a floating o-ring while the back one will still function as normal. My only worry is that the front o-ring will have too much play and come loose.
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Unread postAuthor: noname » Tue Jul 12, 2011 10:35 pm

I just glanced through this whole thing and I have to say it looks amazing! Great job on that MiniBoy LeMaudit and awesome plinker Crowley. I'll be waiting on some insane results!
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Unread postAuthor: Fnord » Wed Jul 13, 2011 6:31 pm

Hey Crowley,
Try removing the pilot valve seal/rod and plugging the pilot port. I don't see how the math could be that far off, so it it may have something to do with the rubber deforming when a certain pressure differential is reached. The same effect could apply to your piston face, though probably with less likelihood.
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 13, 2011 10:05 pm

LeMaudit wrote:The ploy : "jeez my canon is broken I cannot fire the MiniBoy sorry'bout that..."
... is way too obvious :wink:


Indeed.

MrC, you know you could easily throw in a burst disk and be done with it ;)
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Unread postAuthor: Insomniac » Thu Jul 14, 2011 2:00 am

Yeah, but imagine if he had a burst disk failure while the gun was pointed, say, out to sea? I don't imagine many members would be happy with him!
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Unread postAuthor: jackssmirkingrevenge » Thu Jul 14, 2011 2:27 am

Yeah, but imagine if he had a burst disk failure while the gun was pointed, say, out to sea?


He could just as easily have a pilot failure ;)

I don't imagine many members would be happy with him!


Whichever direction the barrel is pointing in, the instant he loads it into the barrel with the intention of shooting it, hatred is inevitable regardless. No pressure MrC ;)
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Unread postAuthor: MrCrowley » Thu Jul 14, 2011 2:52 am

Whichever direction the barrel is pointing in, the instant he loads it into the barrel with the intention of shooting it, hatred is inevitable regardless. No pressure MrC

F**k this, I'm fleeing to Mexico! :D

In other news, I'm working on a new YouTube channel with the goal of it attaining 'partner' status. I would apply for partner using my old account but too many videos have copyrighted material I've decided to start new. I'm going to focus more on how-to videos to try lure in the n00bs out there on YouTube. Wish me luck :wink:
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Unread postAuthor: Mr.Tallahassee » Thu Jul 14, 2011 5:16 am

I decided to give a go at finding the Cd of the MiniBoy. I would guess based on shape, if it were polished very well, the Cd would be ~.06 ±.004. I'm no expert at math/physics but my guess is based on numerous pages on Drag Coefficients, this should be a very good guess. Based on shape, the body would be around .05 and the fins would be around .002-.003 each (and I count 4 of them). I guess you can slap those numbers in hgdt and see what it comes up with.

EDIT: In my boredom, I decided to try out hgdt myself. It puts golf balls at 371 meters at 10 deg elevation while it puts MiniBoy at 1503 meters at 10 deg with a Cd of .06 which cant be real. That would be ungodly for a spud cannon of any kind. :shock: I bumped it to .1 and got 1090 meters.
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Unread postAuthor: MrCrowley » Thu Jul 14, 2011 7:28 am

Mr.Tallahassee wrote:EDIT: In my boredom, I decided to try out hgdt myself. It puts golf balls at 371 meters at 10 deg elevation while it puts MiniBoy at 1503 meters at 10 deg with a Cd of .06 which cant be real. That would be ungodly for a spud cannon of any kind. :shock: I bumped it to .1 and got 1090 meters.

I'd be disappointed with 1503 meters even at only 10 degrees elevation, I guess you're not using my cannon's parameters for HGDT :wink:

Using the figures for my cannon, I get a muzzle velocity of over mach 1 including sabot (where proj. + sabot = 150g).

Using GGDT to model the projectile at the same velocity as given in HGDT but with the barrel diameter matching the projectile diameter (no sabot) and projectile weight down to 100g and using Tallahassee's Cd value of 0.06, I get a range estimate of 7100m at a 41 degree angle and 4700m for a 15 degree firing angle. :shock:

Thanks for the Cd calculation estimates Tallahassee, hopefully some other members will be able to affirm those figures.
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Unread postAuthor: Gun Freak » Thu Jul 14, 2011 8:52 am

Good luck on the partnership, I've applied too. I already have a huge AdSense account :lol:
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Unread postAuthor: clemsonguy1125 » Thu Jul 14, 2011 1:14 pm

Lol, you could probably get a few hundred thousand fews just with a slideshow of pictures from your instructables. I heard most people start getting accepted with about 400 subs.
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Unread postAuthor: Mr.Tallahassee » Thu Jul 14, 2011 1:52 pm

I actually used the parameters from the video for the gun. Everything matched up. The only issue was that I didn't adjust the weight for the sabot. I completely forgot about that(3am does that to you). :sleepy3: I don't know what went wrong other than that. It was worth a shot though.
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Unread postAuthor: MrCrowley » Thu Jul 14, 2011 5:18 pm

Mr.Tallahassee wrote:I actually used the parameters from the video for the gun. Everything matched up. The only issue was that I didn't adjust the weight for the sabot. I completely forgot about that(3am does that to you). :sleepy3: I don't know what went wrong other than that. It was worth a shot though.

Ah my apologies.
Did you calculate the range for the projectile without the sabot? For calculating the range for a projectile that is fired with a sabot in a hybrid, we've found out it is best to use both HGDT and GGDT. We use HGDT to calculate the velocity of the projectile + sabot and then use GGDT to construct a fake cannon that matches the same muzzle velocity from HGDT except the barrel diameter and projectile diameter now match that of the projectile (no sabot) and projectile weight is excluding the sabot weight.

If you calculate the range in HGDT, it will include the sabot weight in the calculations and the diameter of the sabot as the projectile diameter. Because sectional density would be quite crap in a 4.8cm diameter projectile with a Cd of 0.06 compared to one 1.8cm in diameter, the range calculated will be much less.

Anyway that's the only reason I can think of why the results would be far off. The only other thing I've changed is an extra 15cm of chamber length.

Lol, you could probably get a few hundred thousand fews just with a slideshow of pictures from your instructables. I heard most people start getting accepted with about 400 subs.

Yeah, I had about 250 subs or so. Now I have zero on my new channel :(
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