30 replies to this topic

[Mortartube]

You could do a rocket with them but with no stars. Just stick a parachute on it like the model rocket fans. Strap a lance to the side and you can see where it comes down too if you fire at night.

Edited by Mortartube, 21 September 2009 - 10:14 AM.

[Sambo]

You could do a rocket with them but with no starts

Or you could add a big salute a shell would be wasted that high up anyway.
Hmm... big endburner anyone?

Edited by Sambo, 21 September 2009 - 10:17 AM.

[wjames]

well, i tested a peice of this tube today.....

Have yet to order more chems for this year, so was limited to some Fast (ish) BP.....Around 30g.

Used a large sledge hammer to ram a 2.5 inch clay plug, a card disk, 30g of bp, another card disk, then rammed another 2.5 inches of clay....When say rammed, i mean RAMMED. these things were rock solid. ended up with a 6 inch length of tube, which, when tested, remained intact - both plugs were popped out.

Good test. Good tube.

[Mumbles]

The odd thing about these big rockets is that they don't cause as much damage as one might think. A friend makes 3" ID whistle rockets. I think the videos have been posted here. They're so heavy they don't go up all that high, and they float down relatively slowly horizontally.

There is another fellow who makes 2" ID rockets. I can provide some contact details to anyone who is interested.

[wjames]

Hmmmmm.. take the casing as 500g ( including clay+stick)

or 0.5kg

say it reaches 2000 feet

My maths say( and theyre not that great), with a friction co-ef. or around 0.4, falling through average air, or density 1.3 kg/m3
Falling at 9.8 m/s, a 500g object will hit the ground doing aproxx

251 MPH.

That'll mean it'll have around 4900 Joules behind it when it reaches something solid.

Thats the same amount of energy, as a 50KG chunk of steel, being dropped from 10m.

That tube, doing 250mph, will be fairly certain to kill you....

Just a thought.

[wjames]

In all honesty, i'd bet there ARE people who would not consider the physics of that prior to lighting the fuse.

In terms of a shell, if it explodes, then great, the largest peice that falls to earth will be small enough not to worry about, and its friction co-efficent will mean it'll never gather any REAL speed

If a shell DIDNT go off.....well, doesn't bear thinking about really....



I'll consider making a rocket engine with a 1 foot section....and static testing it.....with a veiw to a sea lauching( sensible )

Think the rest will go to making a maroon repeater - what tube length would a 2 inch mortar normally require...By that i mean is there industry standard.

[CCH Concepts]

Hmmmmm.. take the casing as 500g ( including clay+stick)

or 0.5kg

say it reaches 2000 feet

My maths say( and theyre not that great), with a friction co-ef. or around 0.4, falling through average air, or density 1.3 kg/m3
Falling at 9.8 m/s, a 500g object will hit the ground doing aproxx

251 MPH.

That'll mean it'll have around 4900 Joules behind it when it reaches something solid.

Thats the same amount of energy, as a 50KG chunk of steel, being dropped from 10m.

That tube, doing 250mph, will be fairly certain to kill you....

Just a thought.

being that the tube would be top or bottom heavy. Would it not tumble or full flat there for increasing its co-ef of friction?

[wjames]

i took an average to calculate.......I used the standard sphere...

you bring an interesting point though.....

It would be heavy at one end.....you are forgetting there would more than likely be a stick on the rocket, which, one the rocket reached its terminal height, would fairly quickly be pointing skywards..... I forgot to equate the mass of the stick...given the weight of the rocket with no payload, the stick would be at least 200G - thus adding to the impact force !!!

Though, should the stick seperate, the nosecone would provide a rather aerodynamic shape to add a few MPH.

Regardless of how it fell, it'd be "be taching" when it reached 0m.


An interesting topic

[starseeker]

...





Think the rest will go to making a maroon repeater - what tube length would a 2 inch mortar normally require...By that i mean is there industry standard.

Approx 380mm.

[wjames]

Approx 380mm.

so my 8 tubes just became 16......

Interesting.....

[CCH Concepts]

i took an average to calculate.......I used the standard sphere...

you bring an interesting point though.....

It would be heavy at one end.....you are forgetting there would more than likely be a stick on the rocket, which, one the rocket reached its terminal height, would fairly quickly be pointing skywards..... I forgot to equate the mass of the stick...given the weight of the rocket with no payload, the stick would be at least 200G - thus adding to the impact force !!!

Though, should the stick seperate, the nosecone would provide a rather aerodynamic shape to add a few MPH.

Regardless of how it fell, it'd be "be taching" when it reached 0m.


An interesting topic

well i wounder if it would be possible to design the rocket, to have its center of gravity at a point that would make it fall in a way to give maxium surface area. therefore reducing terminal velocity

[wjames]

well i wounder if it would be possible to design the rocket, to have its center of gravity at a point that would make it fall in a way to give maxium surface area. therefore reducing terminal velocity

firstly, to do that, you'd have to find a way to remove both plugs - a break charge at the "plug " end would be easy enough, but at the nozzle end it may prove difficult - then youve still got a tube, which, is now hollow.....

In being hollow, its most aerodynamicly stable when air is flowing THROUGH it, rather than over it.....so as soon air passed over the mouth of the tube, it'd want to straighten up, and fall STRAIGHT down the way......


Parachute is the answer..easy to do, only needs a little puff to pop it out, or if your really good, a nosecone that is loose, and will "pull" the chute out.

all the model guys use parachutes, along with fireproof wadding - that would be the safest way IMHO

[digger]

Think about it chaps. If the stick stays on the drag will cause the rocket to come down nose first. If the stick comes off the tube will tumble.

If you must you could work out which would hit harder and faster. But needless to say it would injure anyone it hit.

I have seen a 6lb rocket come down and go straight through someones roof nose first. I guess one of these would end up in the living room.

I have some 3" tubes and they weigh 1.8Kg each (the same tubes that our American friend uses for his 3" motors). I guess his motors are pretty powerful as he puts up 12" shells on them if I remember correctly and they do tend to go a little high for the shell.

[MDH]

I would say that you should cut this tube into pieces and make fountains and mines out of it.