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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: Goats spudz » Tue Oct 18, 2011 5:02 pm

MrCrowley wrote:Yup, even an AA battery wont fit (perhaps the diameter is actually less than 14mm, I can't remember). Something the size of a sim card but longer would probably work great.
wouldn't it be possible to create your own Gps that size? micro-circuit board?
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Unread postAuthor: ramses » Tue Oct 18, 2011 5:18 pm

aah, I forgot how small it is. Somehow, I got it in my head that it was like 40mm OD or something. Oh, wait... That's the OD of the sabot.

:oops: :oops:

I guess we'll just have to go with the cake.
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Unread postAuthor: MrCrowley » Wed Oct 19, 2011 12:14 am

Tried to cook some cake today, it was raining all day so I had to go in the garage. I pussied out. We have some black paper like material lining the garage roof and I didn't want to risk it catching fire if the mix ignited (I realise this is an extremely unlikely scenario). I didn't really trust using the heat gun either.

Tomorrow I might cook outside and caramelise the sugar first, remove it from the heat, add the self-raising flour and then give it a stir over the heat for a little bit longer.
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Unread postAuthor: Insomniac » Wed Oct 19, 2011 2:06 am

Caution is always admirable, but how much cake exactly were you cooking? If you're only talking the amount that's going in the miniboy, you're unlikely to get enough flames to scorch the ceiling. Have you ever baked before?

I believe the Mythbusters created a similar dessert which they overdid, that might help you guage the consequences.
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Unread postAuthor: CpTn_lAw » Wed Oct 19, 2011 2:09 am

Something I don't get...
Cake is used to produce smoke, right? Same cake as in Rocket-cake, right?
Then, even without a nozzle, it will produce some thrust, right?
If it is the case... if the cookie crumbles in flight, then you'll definitely distabilize it.
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Unread postAuthor: MrCrowley » Wed Oct 19, 2011 2:46 am

Insomniac wrote:Caution is always admirable, but how much cake exactly were you cooking? If you're only talking the amount that's going in the miniboy, you're unlikely to get enough flames to scorch the ceiling. Have you ever baked before?

Only 60g :D

Never baked before, I'm sure confidence will come with experience. It's like putting 120PSI in a PVC chamber when you first start spudding, you sort of feel unsure even though the pressure rating is 280PSI.

Tomorrow, cake will be made (assuming it doesn't rain again).

CpTn_lAw wrote:Something I don't get...
Cake is used to produce smoke, right? Same cake as in Rocket-cake, right?
Then, even without a nozzle, it will produce some thrust, right?
If it is the case... if the cookie crumbles in flight, then you'll definitely distabilize it.

We did discuss this before although I can't remember the outcome of the discussion. Perhaps this is a 'pro' for the 'ignition upon impact' argument.
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Unread postAuthor: Insomniac » Wed Oct 19, 2011 3:54 am

I will have no part of this project if food is served in-flight! It just seems to defeat the purity of the test, so I'm putting my foot down. Yeah, you'd better listen! Somehow I feel this won't be taken seriously... :D

Funnily enough MrC, I still wouldn't feel comfortable with 120 psi in PVC... I've never pressurised a PVC pipe, never solvent welded PVC or ABS, and indeed have never built any large bore, 'traditional' spudgun. My eternal fear of Australia's firearms laws means I now exclusively fool around with launchers that can barely penetrate paper. :lol:
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Unread postAuthor: Zeus » Wed Oct 19, 2011 4:14 am

MrCrowley wrote:Only 60g



By cake I take it you mean potassium nitrate and sugar?

That won't start a big fire, I wouldn't be too worried if that started in a garage, it'd smoke out the garage though.

Just have a tray and bucket of sand nearby, <b>don't</b> use water.
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/sarcasm, /hyperbole
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Unread postAuthor: Insomniac » Wed Oct 19, 2011 5:07 am

Zeus, out of curiosity... Why not water when aborting cake (Yes, that cake)?

I know why water can't be used for oil fires, and I know cake fires can sustain underwater... but will water on cake have a negative effect as in an oil fire, or will it just be ineffective? I can't imagine a small amount of cake managing to keep alight if a bucket of water was dumped on it.
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 19, 2011 5:34 am

Insomniac wrote:I will have no part of this project if food is served in-flight! It just seems to defeat the purity of the test, so I'm putting my foot down. Yeah, you'd better listen! Somehow I feel this won't be taken seriously... :D


I chuckle at your manner of presentation but also firmly concur with the sentiment.

My eternal fear of Australia's firearms laws means I now exclusively fool around with launchers that can barely penetrate paper. :lol:


Damn shame if you ask me.
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Unread postAuthor: Zeus » Wed Oct 19, 2011 5:39 am

I personally wouldn't use it, if it's still burning, then the water will start to boil, which may spit, whereas sand will just stop it setting anything else on fire.

With cake and any other desserts, I treat them like all of the most reactive chemicals and compounds all rolled into one. The cake may shatter, which would dramatically increase the surface area, then the burn rate skyrockets, then a face full of steam.

I've have one accident with desserts, and I never want to have it happen again. I'm too careful.
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Unread postAuthor: al-xg » Wed Oct 19, 2011 7:29 am

also firmly concur with the sentiment.


Ideally, I'd have the smoke start delayed after projectile impact to get the most amount of burn time while someone is likely to see it.

Just thinking, the projectile may not actually bury itself that much if it lands at a shallow enough angle, but will make quite a crater... which would be good.
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Unread postAuthor: ramses » Wed Oct 19, 2011 3:52 pm

You must realize that cake does not need air to be eaten. It would likely be eatable even under water.


We did discuss this before although I can't remember the outcome of the discussion. Perhaps this is a 'pro' for the 'ignition upon impact' argument.

The other side of this is that the holes are positioned pretty well for base-bleed :D :D
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Last edited by ramses on Wed Oct 19, 2011 7:20 pm, edited 1 time in total.
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Unread postAuthor: al-xg » Wed Oct 19, 2011 5:05 pm

Smoke being stopped by a load of sand on top of it may be an issue tough...


A pitty miniboy doesn't have a base, eh ? ;)


You'd just be left with the turbulent airflow and higher adverse pressure...
Image

Pressure drop in a widening section only happens past mach 1
Image
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Unread postAuthor: MrCrowley » Wed Oct 19, 2011 9:06 pm

Had trouble getting it all to turn to a paste so I chucked it away, melted 20g of sugar and then added 30g self-raising flour. The mix had already cooled and it was difficult turning it to a paste again with all the flour on it but after 10min or so I managed to get a 'nutty' peanut butter texture, not perfect but good enough for now.

Tried it out at the beach, lots of food was produced and a surprising amount of fire. Tried to bury it once ignited but I couldn't tell whether the sand completely smothered the food or the food had stopped being produced. Lasted about 10 seconds in total.

Next time I'll try adding some baking soda (not a food metaphor this time) and stuff the mix in a 15mm pipe nipple to get a rough idea about how it would work in the MiniBoy.

I think this has cast a little doubt on the 'ignition upon impact' idea as well as the 'ignition upon launch/mid-flight ignition' ideas as it would probably produce too much thrust.

Is there anyway of roughly calculating how far the MiniBoy would penetrate in to the sand? Velocity could be about 150m/s or so (just a guess), angle would be quite acute (maybe around 30 degrees?) and the sand quite soft.
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