Timing clarification of Mortar Racks

[R. Derrick]

After spending the last hour searching (and finding other rabbit holes to go down) I'm still not sure...

The finale will be a single fuse lit by an initiator. This single fuse will light all 100+ shells (in several racks) and I want them to go off spaced out enough so as not to create sky puke. I'll risk that timing but if you guys wanna give any insight into that, I'll listen.... however, my real question is next.

Assuming everything is on my racks is fused correctly and all of my shots will go off as expected (within the variance of 1.4)... my only concern with timing would be how long it takes the initial shell to lift? For some reason, I can't wrap my head around the math (if any). Give me a pool table and I'm fine but this math is frustrating.

My brain wants to make this complicated.


I guess what I'm trying to figure out is I know there is the long Visco (I think that's what it is - the green fuse going into the artillery shells from the factory) fuse that leads to the shell but I don't have to be concerned with that timing for all of the shells, right? Since each one has that green Visco, do I need to add time for each shell?

I feel like all of the timing doesn't "Stack" but is rather absorbed by the delay on the first shell. The faster fuse will continue to go down throughout the rack lighting the next shell (or row of shells) as it burns but the only delay is the initial shell, right? So I should fire the finale cue about 5+/- seconds (I will probably poke the first canister to use my own fuse, so I can be more precise rather than using the preexisting fuse but I think you understand)

Am I making sense here? Please correct me on anything or provide info wherever your heart leads. I'm new to a lot of these details but have been shooting for quite some time and any info will be of help.

Thanks you guys!

[ssmith512]

It's an easy thing to be confused with.

You only need to figure into your timing delay the burn time of the leader fuse of the first shell (green visco attached to the shell) and lift time of the first shell (time it takes for the shell to rise after it leaves the mortar tube and burst).

Assuming all leader fuses are the same length and all leader fuses burn at the same rate and you are attaching the leader fuses to the main fuse at identical distances, then the burst time between each shell is determined by the time it takes for your main fuse to burn between each shell.

Example:

Lets say you have cut all the leader fuses to the same length - lets say 7". You have determined that fuse at 7" will take 5 seconds to burn to ignite the lift charge of the shell. You have also determined that once the lift charge ignites, the shell will travel upward for 2 seconds and then burst. SO, if you want that shell to burst at a specific time during a program, you need to light the leader fuse 9 seconds before the time you want the shell to burst (7 seconds of leader fuse burn time + 2 seconds of lift time). This is the calculation for the first shell.
Following along?

Now you want to string along more shells. Let's say you want each shell to burst at 1 second intervals. What you now need is the burn rate of the main fuse you are going to use. Let's say you have Pink Perfect fuse. That fuse burns at 10seconds per foot or 1.2" per second. So if you want each shell to burst every second, you need to attach the leader fuse of each shell to the pink fuse every 1.2". So after the first leader fuse is lit, the pink fuse is also lit, the fire burns along the pink fuse and lights each leader fuse every 1 sec (if you have attached each leader fuse every 1.2"). You dont need to worry about each leader fuse in your calculations, IF each leader fuse is the same length and burns at the same rate. Each leader fuse could be a mile long, and take 3 hours to burn to get to the shell, but if each leader is attached to the pink fuse at 1.2", then the shells will burst at 1 second intervals after the first shell bursts, but it will take 3 hours before the FIRST shell bursts.

Hope that make sense.

[WithReport]

Not all green visco off shells/canisters perform the same and they are not all the same length. Based on measurements I've collected over the years here is what I have (image attached) and I wouldn't be surprised if others have varying results.

Visco delay: Min: 4.7 sec , Max: 6.3 sec, Average: 5.25sec
Lift Time: Min: 1.4 sec, Max: 2.2 sec, Average 1.6

5770

And if your leader fuse is faster, you will burn up some of the time where you overlap the fuse to transfer fire. Years ago, I did some testing and created a spreadsheet to calculate it all down to the milliseconds. However it was fairly pointless. Besides the variation across brands, they will also vary from year to year. So I wouldn't try to be two specific with the fuse timing.

As for your question - on a string of shells, that you want to go off at a consistent rate (same intervals), you only need to account for the delay's leading into the first item on the string. ssmith512 provided some good examples.

[R. Derrick]

Smith -

Thanks so much for clarifying and the insight. This is how I was thinking it would work. Thanks for the detailed response :) Maybe it was a typo, but would it not be 7 seconds? The 5 seconds for fuse and 2 seconds for lift time? Or what did I not understand? The rest of it makes perfect sense to me!

THAAAAANK YOOOU!



With Report -
My brain tends to work like this. It would be like me to create such an algorithm for it to only be pointless lol. And the good thing is, these aren't timed like the rest of my show. That spreadsheet is great! I had timed out the excal at 1.75 lift time. it varied greatly between 1.5 and 2 so I rounded it. Of course, it could different years or batches.

Thanks for your graphic and response too! :)

[ssmith512]

Smith -

Thanks so much for clarifying and the insight. This is how I was thinking it would work. Thanks for the detailed response :) Maybe it was a typo, but would it not be 7 seconds? The 5 seconds for fuse and 2 seconds for lift time? Or what did I not understand? The rest of it makes perfect sense to me!

THAAAAANK YOOOU!

OOOPS. Yes typo.........5 seconds + 2 seconds is indeed 7 seconds and not 9 seconds. Good thing this wasn't a test, I would have failed LOL!! (My excuse is that it is Saturday and I turn off on the weekends - that is my story and I am sticking to it! ;) )

[Scotty Rockets]

My experience with racking and fusing shells it’ll never time perfectly. Only thing you have control over is the fuse you use the chain them with. For me I just rack them and fuse them for finales.

[upNdown]

One thing that I've noticed is the more shell visco you have overlapping with your main fuse, the worse your timing will be.
If you run your main fuse across the tops of the tubes, the 3ish inches of shell visco will actully be overlapping with each other, if you run their whole length across the main fuse. And for some reason, that just tends to mess up the timing. So if timing between shells is important to you, trimming off as much extra visco at the end of each shell as you can, will help that.

[Greenville Pyro]

One thing that I've noticed is the more shell visco you have overlapping with your main fuse, the worse your timing will be.
If you run your main fuse across the tops of the tubes, the 3ish inches of shell visco will actully be overlapping with each other, if you run their whole length across the main fuse. And for some reason, that just tends to mess up the timing. So if timing between shells is important to you, trimming off as much extra visco at the end of each shell as you can, will help that.

Seconded on that. Trimming and individually securing takes far more time than braiding with whatever colored fuse you are using, but the spacing is much better. But, accept from the get go that shells will never be perfect and that’s ok.

[Rick_In_Tampa]

Figuring out the exact timing of anything tied together with visco is like trying to define the singularity on the other side of a black hole. It's just not going to happen.

I usually use 300 cans fused with .4 sec fast fuse and it's pure sky-puke. This year I'm going to use multi-break ball shells with 1.4 sec fuse to slow things down a bit. I gave up on trying to figure out how long it will burn. I figure when it stops, people will go home.

[WithReport]

If you are able to, reserve some extra cues for your finale and split it up. This does two things. 1) It provides redundancy if one cue fails and 2) it improves timing by removing some of the fuse variability.

For example, if you wanted chains of shells to run for 30 seconds, run two 15 second chains and ignite the second one 15 seconds after the first.

I remember my first scripted show with 48 cues and I had a lingering cake that went on forever at the end - ugh :(.

In the image attached, there are highlighted events within the last 30 seconds - these are all the consumer canisters at the end. There are chains of six shells followed by flights of shells (e-fired in parallel), and then I'll try to put an explanation on the end with 3 e-fired shells at the very end. In total ~ 60 of them.

(The image is a scripted show that will be automatically fired, but the concept is the same even if manually firing)

We'll see how it works this year.

5772

[ssmith512]

I figure when it stops, people will go home.

Unless it's your useless brother-in-law who sticks around afterwards and proceeds to tell you what you did wrong, what you should have done and what you "need to do" next year to make it better (even though he doesnt brains enough to tie his own shoes). :D

[R. Derrick]

My experience with racking and fusing shells it?ll never time perfectly. Only thing you have control over is the fuse you use the chain them with. For me I just rack them and fuse them for finales.

Exactly right! :) Thanks!


One thing that I've noticed is the more shell visco you have overlapping with your main fuse, the worse your timing will be.
If you run your main fuse across the tops of the tubes, the 3ish inches of shell visco will actully be overlapping with each other, if you run their whole length across the main fuse. And for some reason, that just tends to mess up the timing. So if timing between shells is important to you, trimming off as much extra visco at the end of each shell as you can, will help that.

Yes! I plan on doing that and trimming will happen. But I don't expect perfect timing, just overall timing to be accurate as possible. Thanks for your reply!




Seconded on that. Trimming and individually securing takes far more time than braiding with whatever colored fuse you are using, but the spacing is much better. But, accept from the get go that shells will never be perfect and that?s ok.

Absolutely! I do accept that lol - I learned last year but I know it can be done a bit better than my first attempt. Thanks for your input and seconding the trimming. I've never tried braiding but I've seen videos that have them braided.


Figuring out the exact timing of anything tied together with visco is like trying to define the singularity on the other side of a black hole. It's just not going to happen.

I usually use 300 cans fused with .4 sec fast fuse and it's pure sky-puke. This year I'm going to use multi-break ball shells with 1.4 sec fuse to slow things down a bit. I gave up on trying to figure out how long it will burn. I figure when it stops, people will go home.

Holy cow 300 cans with .4 secs fuse. I have both .4 and 1.4-2.3sec. What I'm considering is using a 1.4 running down the long side, and then the .4 going across the short side (3 and 4 shells across). It's more fuse for sure but more timely maybe?


If you are able to, reserve some extra cues for your finale and split it up. This does two things. 1) It provides redundancy if one cue fails and 2) it improves timing by removing some of the fuse variability.

For example, if you wanted chains of shells to run for 30 seconds, run two 15 second chains and ignite the second one 15 seconds after the first.

I remember my first scripted show with 48 cues and I had a lingering cake that went on forever at the end - ugh :(.

In the image attached, there are highlighted events within the last 30 seconds - these are all the consumer canisters at the end. There are chains of six shells followed by flights of shells (e-fired in parallel), and then I'll try to put an explanation on the end with 3 e-fired shells at the very end. In total ~ 60 of them.

(The image is a scripted show that will be automatically fired, but the concept is the same even if manually firing)

We'll see how it works this year.

http://www.pyrotalk.com/bulletin/attachment.php?attachmentid=5772&stc=1

That's a great idea! I do have extra cues leftover but was going to use them for an after-show event. Having random cakes ready and loaded to fire. I'm sure some of the people would like to hit the button! But... I like the idea of using the cues for more finale and timing in case. Last year, I too had the lingering cake - and then the delayed cake - and then and then and now I want "no and then!" I hope it works out for you this year! I don't understand your script - I'm new to scripting and have only seen cobra.
I know there are others and I know all it takes is a CSV file made in excel but I need all the gimmicks, bells, and whistles for now lol... Thanks for your input!