Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 59 users online :: 4 registered, 0 hidden and 55 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

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!
Sponsored 
  • Author
    Message

Unread postAuthor: saefroch » Fri Oct 07, 2011 4:50 pm

Ah yes, the freefall problem... as mentioned above. I think personally that if Crowley can just find a highly reliable way to trigger the cake, or more simply a circuit, on an acceleration in the negative x direction (assuming that the initial acceleration is in the positive x), that'd be sufficient.
  • 0

User avatar
saefroch
Major General
Major General
 
Posts: 1679
Joined: Mon Jun 08, 2009 8:47 am
Location: U.S.A.- See Map
Country: United States (us)
Reputation: 0

Unread postAuthor: ramses » Fri Oct 07, 2011 5:22 pm

The mini boy experiences 9.8m/s^2, but so do all the components of the tilt switch. It is, effectively, in a weightless enviroment.

This is why people experience weightlessness in orbit; they are not away from gravity, they're just in continuous free-fall. The Mini-boy, is, in essence, orbiting the earth for a brief period of time. It's orbit intersects with the earth, though :D :D
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: al-xg » Fri Oct 07, 2011 6:20 pm

Yes but free fall is FREE of other forces. In air that pretty difficult unless you are going slow enough or are streamlined enough to make those forces negligible.

The lack of deceleration is what would have to be measured, it only gets weaker as the projectile slows and as gravity begins to help on the way down (the resultant force does any way).

Well that is, if you want something triggered before impact.

It sounds a lot better when shooting a spud gun becomes putting an object into orbit ;)

Trigger on impact is good unless the projectile get buried too deep.
Shoot sand bags as a test ? :D Box-o-truth style just bigger.

Not very practical shooting at night but I think it would be very cool to use a powerful laser as a tracer beam from the rear of the projectile :)
Mmmm, even size wise this isn't practical but it would be amazing.
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Unread postAuthor: Ragnarok » Fri Oct 07, 2011 6:47 pm

al-xg wrote:...are streamlined enough to make those forces negligible

We're talking about a heavy, dense, pointy and stabilised projectile. It probably has a terminal velocity most of the way to the sound barrier.

It would have to be going pretty fast for drag to be enough to activate the sensor, and would be insensitive to the direction of "up" (as it is in fall) - so, if it goes off at all, it means it'd go off shortly after launch (as the water rocket video says), given that's when it'll be moving fastest.

Useless for detecting apogee, only really useful for detecting launch - and that's only if you are very careful about how you load it to stop it going off as you do.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: MrCrowley » Fri Oct 07, 2011 7:36 pm

Not very practical shooting at night but I think it would be very cool to use a powerful laser as a tracer beam from the rear of the projectile
Mmmm, even size wise this isn't practical but it would be amazing.

Could land me in hot water. The beach is within 100km of Auckland International Airport and would be close to the flight paths for Fiji-and-Japan-bound planes.

I'm liking this discussion, lots of input from many members. The success of this launch doesn't rely solely on Le Maudit's projectile and my cannon :wink:
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: ramses » Fri Oct 07, 2011 8:04 pm

MrCrowley wrote:
Not very practical shooting at night but I think it would be very cool to use a powerful laser as a tracer beam from the rear of the projectile
Mmmm, even size wise this isn't practical but it would be amazing.

Could land me in hot water. The beach is within 100km of Auckland International Airport and would be close to the flight paths for Fiji-and-Japan-bound planes.

I'm liking this discussion, lots of input from many members. The success of this launch doesn't rely solely on Le Maudit's projectile and my cannon :wink:



Shoot with your back away from the airport.

I think some testing is in order. Go to the beach with some high sectional density projectiles. Put 000 steel inside something like a soup can. If this works (and it probably will), you need to modify the sabot so the steel wool is exposed to the combustion gasses.

Having the steel wool on the back would create excessive drag, but if you used it to ignite visco, it could be discarded with the sabot and you would have a time delay, and then some flare comp inside the round.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

Unread postAuthor: al-xg » Fri Oct 07, 2011 8:21 pm

as the water rocket video says
that's because it is a rocket and is still accelerating, I know you know that but in this case it isn't really a good example. I have the feeling my post was maybe misinterpreted (probably not very clear :roll:), I am talking about measuring the loss of deceleration.

I'm pretty sure there would be a measurable difference between deceleration at muzzle exit and in the flight past the apogee.

The merit of this discussion is I guess to point out that it is to theoretical, I doubt anyone is going to get around to calibrating what basically is a home made accelerometer.

A timed trigger would certainly be simpler in my opinion. The only real point in triggering is to insure that enough smoke or whatever it is is produced to be visible for long enough after the shot, otherwise it could be set off on leaving the barrel ?

I have the feeling this has been mentioned before, but how about making some castings from Miniboy, Epoxy and lead for example to be able to make some calibration shots ?
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Insomniac » Fri Oct 07, 2011 10:40 pm

Yes, the water rockets are rockets, BUT they have a fairly short duration of thrust. Neglect that part of the flight, and you have very similar situation to the miniboy. However the water rockets are quite draggy while the miniboy is not, meaning the mercury switch has even less of a chance of activating in flight for the miniboy. In my mind this is good, however... It will leave the most likely point of activation at impact, removing the chance of the cake upsetting the flight.

Another thing to note is that even given a smoke trail in flight, it's going to be very, VERY difficult to pin down where it lands. I've crashed RC planes in fields before, and not moved my eye from the point of impact... yet still had to search for ten minutes to find it. Smoke upon landing would probably be better, provided someone can get to the expected impact zone quickly enough.

Another thought... MrCrowley, do you know any experienced RC hobbyists? Do you know anyone with a GoPro or similar lightweight, HD camera? A reasonably high altitude aircraft with a wide angle HD camera could capture a large area, perhaps a kilometer squared, with probably a good enough resolution to detect any sizeable smoke cloud... Comparing this with google maps for better resolution could really narrow down the search area, and if it doesn't prove useful it shouldn't jeopardize any other aspect of the experiment.


Also, @al-xg... The forces on the projectile due to gravity are identical at the muzzle, at apogee and at the moment before impact. The ONLY differences are due to air resistance. These are that at the beginning of the flight, the velocity and thus the drag will be higher, meaning the deceleration will be stronger. As the projectile slows, the deceleration will ease off. Finally, when terminal velocity is reached the force the interals will 'feel' will be 1G as the body of the projectile is no longer accelerating.
  • 0

I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
User avatar
Insomniac
Major General
Major General
 
Posts: 1297
Joined: Mon Dec 18, 2006 3:47 pm
Location: Australia
Country: Australia (au)
Reputation: 0

Unread postAuthor: MrCrowley » Fri Oct 07, 2011 11:22 pm

Insomniac wrote:Another thing to note is that even given a smoke trail in flight, it's going to be very, VERY difficult to pin down where it lands. I've crashed RC planes in fields before, and not moved my eye from the point of impact... yet still had to search for ten minutes to find it. Smoke upon landing would probably be better, provided someone can get to the expected impact zone quickly enough.

Another thought... MrCrowley, do you know any experienced RC hobbyists? Do you know anyone with a GoPro or similar lightweight, HD camera? A reasonably high altitude aircraft with a wide angle HD camera could capture a large area, perhaps a kilometer squared, with probably a good enough resolution to detect any sizeable smoke cloud... Comparing this with google maps for better resolution could really narrow down the search area, and if it doesn't prove useful it shouldn't jeopardize any other aspect of the experiment.

Ok so I'll concentrate my research on getting the MiniBoy to ignite upon impact and I'll try do some tests at the beach when I get the cake mix to see how well the smoke can travel through sand.

As for the RC thought, I don't know anyone who is in to RC let alone RC planes, unfortunately. Do you have any recommendations about a cheap and easy way to dye the smoke? I've read a little on the matter and it seems like you need a particular chemical.

ramses wrote:Having the steel wool on the back would create excessive drag, but if you used it to ignite visco, it could be discarded with the sabot and you would have a time delay, and then some flare comp inside the round.

Think I mentioned before I couldn't get my hands on any visco in the foreseeable future although I probably can make some homemade if it comes to that. My plans for the steel wool was to have a little bit in each of the 6 holes with a little more at the base of the projectile by the holes, that way it wouldn't effect aerodynamics.

As a side note, I assume you guys are aware I can superglue MiniBoy together just before the launch so as to discard the internal bolt and create more room in the cavity.

al-xg wrote:A timed trigger would certainly be simpler in my opinion. The only real point in triggering is to insure that enough smoke or whatever it is is produced to be visible for long enough after the shot, otherwise it could be set off on leaving the barrel ?

I have the feeling this has been mentioned before, but how about making some castings from Miniboy, Epoxy and lead for example to be able to make some calibration shots ?

I do have a delrin/nylon/one-of-those-plastics 'practice' MiniBoy originally intended to test the sabot. Although I initially pushed aside the idea, recently I've been thinking about doing small scale tests at a local field with a pneumatic just to make sure the sabot is working well.

I'll talk to my dad about some triggering mechs, he might have a suggestion.
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: Insomniac » Sat Oct 08, 2011 2:30 am

Not sure on how to colour the smoke, I really was never much of a cook so I have only very limited experience in baking cake.

And if you superglue it, be careful. Superglue can hold a lot of weight, yes, but it's an acrylic bond. It can crack quite easily and I'm not certain it would be up to the task of holding the MiniBoy together. You can get 90-second epoxy, though I'm not sure how long it takes to reach a useable strength.
  • 0

I wonder how much deeper the ocean would be without sponges.
Right now I'm having amnesia and deja vu at the same time. I think I've forgotten this before.

Add me on msn!!! insomniac-55@hotmail.com
User avatar
Insomniac
Major General
Major General
 
Posts: 1297
Joined: Mon Dec 18, 2006 3:47 pm
Location: Australia
Country: Australia (au)
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Sat Oct 08, 2011 3:07 am

MrCrowley wrote:I'm liking this discussion, lots of input from many members. The success of this launch doesn't rely solely on Le Maudit's projectile and my cannon :wink:


In other words, "If I screw this up, it's not just my fault"

Nice move, MrC :P :D
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Ragnarok » Sat Oct 08, 2011 7:01 am

al-xg wrote:I am talking about measuring the loss of deceleration. I'm pretty sure there would be a measurable difference between deceleration at muzzle exit and in the flight past the apogee.

Yes, if you could actually measure the deceleration from drag accurately, then most things would decelerate rapidly, reach their slowest deceleration at apogee, then start decelerating more rapidly as they picked up speed again.

However, that's a pretty subtle change to measure, and I expect any accelerometer accurate enough would get completely trashed by the thousands of G in the barrel.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: LeMaudit » Sat Oct 08, 2011 8:46 am

jackssmirkingrevenge wrote:
MrCrowley wrote:I'm liking this discussion, lots of input from many members. The success of this launch doesn't rely solely on Le Maudit's projectile and my cannon :wink:


In other words, "If I screw this up, it's not just my fault"

Nice move, MrC :P :D


Yes, that's quite nicely put. Smart guy... :wink:
  • 0

I HAZ A BANG!
User avatar
LeMaudit
Donating Member
Donating Member
 
Posts: 665
Joined: Thu Apr 16, 2009 2:48 pm
Reputation: 0

Unread postAuthor: al-xg » Sat Oct 08, 2011 9:44 am

This is past the useful point for this topic but
The forces on the projectile due to gravity are identical

I'm not saying gravity stops. The components on each axis change with orientation, if you hold a mercury switch horizontally it does nothing, unless you move it from side to side and induce acceleration or deceleration.


Mmm, can't really remember the discussed values, but assuming 80g, 20mm projectile, 0.06Cd, 380m/s and a 41 degree launch angle, there should be about 1.2N difference in drag alone between barrel exit and just before impact. 11.76Kg

Could land me in hot water.

Haha, firing laser projectiles in orbit crossing flight paths with airliners. :) Excellent !
The whole pointing lasers into plane cockpits is only really an issue on take-off landing because of the distance and well the cockpit being on top. But I would hate to have to explain that to authorities having been caught with an supersonic laser bullet canon :roll:


Are industrial made smoke bombs generally better than the home made option ? I've seen orange smoke pellets used to test out chimney draught, i'm pretty sure they're not that expensive.
  • 0

User avatar
al-xg
Colonel
Colonel
 
Posts: 643
Joined: Fri Jan 19, 2007 12:29 pm
Reputation: 0

Unread postAuthor: ramses » Sat Oct 08, 2011 12:41 pm

Colored smoke uses a dye, which would be a problem. If you're shooting this at night, keep in mind that the smoke will be hard to see. I'm thinking downrange observers and a "tracer" type projectile would be best.

Can anyone think of a good way to discharge glowstick juice on impact? It might be worth trying with something like a pop-can.

To replace the visco, you could use a "delay cake" (baking soda reduces burn rate)

If you wanted the smoke to come out during the day, ordinary cotton string burns very slowly. If you soaked some in nitrate, I'm sure it would burn a little more reliably and quickly.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

PreviousNext

Return to Construction Materials/Ammo Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Yahoo [Bot]

Reputation System ©'