16 replies to this topic

[teaboy]

I'm looking into replacing/updating our racking system, and need a bit of help on the 'perfect' angles for fanned mortar tubes. Obviously the middle tube is straight (eg set at 90 degrees), but what angles should the other tubes be at? I'm looking at 3", 4" and 5" shells fanned in 3's, 4's and 5's. I want the bursts to just touch.

Can anyone point me to the information?

[Arthur Brown]

IMO its far to dependant on the particular shells. Some break bigger than others. Upright with +/- 10 and 20 is a fair guestimate, up +/- 15 and 30 would be extreme unless you could be absolutely sure of the safety area being wide enough.

[teaboy]

IMO its far to dependant on the particular shells. Some break bigger than others. Upright with +/- 10 and 20 is a fair guestimate, up +/- 15 and 30 would be extreme unless you could be absolutely sure of the safety area being wide enough.

Would that range cover all shell sizes? Or would I want wider 5" than 3"?

[Arthur Brown]

With bigger shells rising higher and bursting bigger I'd guess that the same angles should work for all sizes.

[seymour]

Assuming you are commercial, you should easily be able to afford a few shells for testing.

Try out a few angles.

But as Arthur pointed out, not all shels of the same size burst the same size. Both shell type and quality affect this hugely.

[Mixologist]

I have used the same angles for all. As people have said some shells do overlap with bigger bursts.

I have just done a 6" rack and simply guessed it pretty much, it comes out at about 20 degrees i think, looks fine when fired. As i didnt have a protractor in my shed i just measured equal distance both sides from the central tube on the top rail of the rack and secure the tube there.

It would be ideal is someone had a table or something?!!

[gunpowderplot]

we have a dinner table if that helps

[Spyrotechnics]

I have a folding table that I use to pop the firing system on, will that help

[dogsbody]

that reminds me....my usual pallet of bricks has gone!!! must get a table or similar!!!!

[Mixologist]

we have a dinner table if that helps

I could do with some nice cheap wood

[teaboy]

I have used the same angles for all. As people have said some shells do overlap with bigger bursts.

I have just done a 6" rack and simply guessed it pretty much, it comes out at about 20 degrees i think, looks fine when fired. As i didnt have a protractor in my shed i just measured equal distance both sides from the central tube on the top rail of the rack and secure the tube there.

It would be ideal is someone had a table or something?!!

Something like this?:



I know it doesn't cover angles, but it's not a bad guide. Just got some simple(!) maths to do now...

Note: I can't claim credit for finding this, but I NEVER reveal my sources...

[pyromaniac303]

Note: I can't claim credit for finding this, but I NEVER reveal my sources...

Hence the label saying Data Source: Vulcan Fireworks in the top left corner?

[teaboy]

Hence the label saying Data Source: Vulcan Fireworks in the top left corner?

Ah yes, but how did I find it?? It certainly wasn't a lucky guess!

[teaboy]

Right, I have the height and burst diameter, and now I've found this.

So, with a bit of typing I have the following angles required between tubes:

Inch mm height diameter Angle
2 50 164 43 15
2.5 65 230 49 12
3 75 263 66 15
4 100 328 98 17
5 125 410 148 20
6 150 492 197 23
8 200 656 361 31
10 250 820 426 30
12 300 984 492 28
16 400 1050 984 50

This should make the edge of each shell burst meet, but not overlap. Does this look right? Anything over 6" looks VERY wide, but I don't need to worry about those at the moment!

Edit:
If anyone knows how to make the numbers line up, you're a better man than me!

Edited by teaboy, 31 July 2009 - 04:41 PM.

[Arthur Brown]

My reason for suggesting 10 - 15 deg as spacing was more for some spread but a sensible fallout area if a side shell in the fan fired blind. You'd have a kilo (+) lump about to travel 100m sideways. There are few firing sites in the home counties with 100m fallout area each side. Probably not many in the whole country!