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Post by londonfan on Aug 13, 2020 5:34:27 GMT -5
I like the 2x6 outer legs. The racks look strong and the joinery looks very clean.
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rosafi
Junior Pyro Member
Posts: 82 
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Post by rosafi on Aug 14, 2020 16:10:56 GMT -5
How did the destruction testing on these go? I am always very curious with wooden racks, especially when the mortars are close together
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Post by pyrot on Aug 15, 2020 3:15:40 GMT -5
Looks good. For 1.3g product I have never really been a fan of wooden racks though. The amount of abuse being tossed around loading and unloading for set-up, and the fact that they are flammable (rarely a show goes by anymore that there isn't at least one small fire to put out, thanks mostly to cakes!) have always made me partial to metal ones. The last few shows I've worked on, we had the "Jericho' rack system, and let me tell you - those are SWEEEEEET ! otherwise, I've used the racks that Sunset fireworks used to make/market, and homemade ones similar. We had some wooden ones the first year I started shooting, and they lasted 4 shows before we went completely to metal ones. I've got a bunch of 3"and 4" ones that were made back in 1998, and other than needing new paint, they are still in great and use-able shape. I'll try to find some pictures of them.
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Post by bigtop on Aug 15, 2020 13:19:58 GMT -5
There is a lot of containment of an in mortar explosion in that rack design. I think you would be very surprised by the result of filling all the mortars with shells and then causing an in mortar explosion to the mortar in the center of the rack. This is what would be required to properly test the the rack. With 3" salutes it is likely that there would be some propagation of the explosion to shells in adjacent mortars. Propagation could also occur with 4" shells if they have a high metal powder content. It is the containment and the mortars being as close together as they are that would cause the propagation of the explosion.
The question is if you tested the rack would all the mortars except the one with the shell exploded in the mortar be intact and pointing up.
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Post by bigtop on Aug 16, 2020 13:02:34 GMT -5
I want to add that propagation of an explosion occurs 2 different ways in a group of mortars. The first is by the shock of the explosion initiating shells in adjacent mortars. The second and more likely type of propagation is when the explosion breaks into and deforms the adjacent mortar lighting the shell in that mortar. That shell then explodes in its mortar because it cannot shoot out of the deformed mortar. This can occur very quickly to several mortars in the group in a chain reaction.
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Post by fireworks4u on Aug 17, 2020 0:39:37 GMT -5
How did the destruction testing on these go? I am always very curious with wooden racks, especially when the mortars are close together Each mortar is separated by 1" plywood so these racks are more than safe |
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Post by fireworks4u on Aug 17, 2020 0:50:16 GMT -5
There is a lot of containment of an in mortar explosion in that rack design. I think you would be very surprised by the result of filling all the mortars with shells and then causing an in mortar explosion to the mortar in the center of the rack. This is what would be required to properly test the the rack. With 3" salutes it is likely that there would be some propagation of the explosion to shells in adjacent mortars. Propagation could also occur with 4" shells if they have a high metal powder content. It is the containment and the mortars being as close together as they are that would cause the propagation of the explosion. The question is if you tested the rack would all the mortars except the one with the shell exploded in the mortar be intact and pointing up. These racks are over built and every tube is safe from the other with 1 inch board separating each mortar I think I'm safe |
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Post by bigtop on Aug 17, 2020 11:39:52 GMT -5
At 1" a 3" salute will break into the adjacent mortars and initiate the shells in them by shock or ignition. 1" is usually enough separation for 3 and 4" color shells to not severely damage adjacent mortars or cause propagation by shock or ignition. This can change with containment. That is one of my concerns with your rack design because the mortars in the center of the middle row have quite a bit of containment around them The other problem caused by the containment is it will cause much more of the force of the explosion to act upon the rack. This is the most likely thing to go wrong. I see only staples and I do not know if you have used adhesive. The force of an exploding 4" shell will quite easily pull staples out. This could result in the rack coming apart to some degree and the possibility of mortars pointing in the wrong direction. I have found that racks that pass testing usually have very little containment around the mortars. The picture below shows the force exerted upon a steel rack by a 2" shell. Most of the force was able to escape and not act upon the rack but as you can see even a small part of the force of a 2" shell is equal to a really hard blow from a sledgehammer. the more containment you have the more force acts upon the rack.  After seeing the results of many rack tests I have learned you never know what will happen until you blow it up. I have built racks with the same approach you have used of trying to build a really sturdy rack only to have my design proved faulty because containment caused too force to act upon the rack causing too much damage to the rack or caused dangerous shrapnel. I would never use a rack I thought was safe. I want to know for sure it was safe before my error in design caused a bad result for me and my audience. Test your rack. Then you will know you are in compliance with section 2.2.6 of the Display Fireworks Manual |
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Post by FireworksFX on Aug 17, 2020 14:27:06 GMT -5
Hi Jamie, your head is in the right space with your attention to building substantial racks, good for you. I'm afraid I'm with Big Top though, when it comes to racks minimalist is a good way to go. When using wood as a material you have to build the proverbial brick chicken house, that generally means air gap between mortars, joins are made with glue and screws and steel banding to give added strength. (we switched to metal racks over 30 years ago after an in mortar malfunction blew the rack to pieces and sent fragments and shells all over the place. They were very similar to yours but we had used screws. And it was only a 75mm that did the damage) A few Canada Days ago we needed more 50mm racks and didn't have time to have our normal design made up in metal so we made a prototype in wood. I swore nothing would touch it but our team said I test everything else so why not test this as well? So we did an upside down test and blew it up. The rack kind of passed the test as the remaining mortars remained in their original position but that might not be the case with another malfunction. We were so shocked by the damage from just a 50mm that we scrapped the idea and waited for our metal racks to be made. And this was 2x6 frame with glue and screws!   CERL (Canadian Explosives Research Laboratory) did some testing of racks and sandboxes a few years ago and that video is a shocker. You will never look at wood racks or sandboxes in the same way again. And when a rack fails it can be disastrous, here is a show in Simi Valley California, one shell malfunction took out multiple racks and injured dozens in the audience. None of us want to go there. Now on to liability and insurance. Our insurance provider is not our best friend, our broker may be but he/she is only selling the product, we're only a number to the insurance company that actually has to pay the claim and they will look for any reason why they do not have to. So if a rack fails and it comes out that the operator was aware of the possibility but failed to take steps to prevent it (ie by testing the rack and documenting the results to show that the rack can withstand an in mortar explosion) my guess is that the insurance provider will walk away from the claim and leave the operator open to charges of criminal negligence.    Once again good for you for putting a lot of effort into your racks, but since they are a critical piece of kit you need to be absolutely sure they make the grade. If you add screws in addition to the staples and steel banding your racks could very well be as safe as houses  |
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Post by bigtop on Aug 17, 2020 15:09:16 GMT -5
Thanks to Fireworks FX for the additional information and great pictures. There you have it Rosafi (Archangel Fireworks) asked about the destruction testing, Big top also suggested you should do the testing and Fireworks FX gave further information about the failings of wood racks and the legal implications. That is 3 established Canadian fireworks companies giving you advice. No one wants to rain on anyone's enthusiasm and we can all see you have good intentions in creating a well constructed rack. We just know that you never know until you blow it up. Just to add some info on the power of salutes pictured below is a mortar after a 3" salute exploded in it. The mortar is DR17 HDPE pipe and was 18 inches long before the test.  |
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Post by pyrot on Aug 18, 2020 0:10:47 GMT -5
There is a lot of containment of an in mortar explosion in that rack design. I think you would be very surprised by the result of filling all the mortars with shells and then causing an in mortar explosion to the mortar in the center of the rack. This is what would be required to properly test the the rack. With 3" salutes it is likely that there would be some propagation of the explosion to shells in adjacent mortars. Propagation could also occur with 4" shells if they have a high metal powder content. It is the containment and the mortars being as close together as they are that would cause the propagation of the explosion. The question is if you tested the rack would all the mortars except the one with the shell exploded in the mortar be intact and pointing up. These racks are over built and every tube is safe from the other with 1 inch board separating each mortar I think I'm safe Your last comment here. This is one I NEVER want to here when discussing explosives!!!I'm not trying to put you down, or discount the racks you built, or anything like that,BUT, this is a business/hobby where "you think you're safe" doesn't cut it !!!! Canada already has some of the worlds strictest fireworks regulations and requirements of the world, and every accident/incident just means they(NRCan) will make them even tighter. PLEASE, don't just "think" you're safe - KNOW for sure you are safe. it's not just you, that you are putting in jeopardy, it's all of us! |
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Post by fireworks4u on Aug 18, 2020 12:16:44 GMT -5
These racks are over built and every tube is safe from the other with 1 inch board separating each mortar I think I'm safe Your last comment here. This is one I NEVER want to here when discussing explosives!!!I'm not trying to put you down, or discount the racks you built, or anything like that,BUT, this is a business/hobby where "you think you're safe" doesn't cut it !!!! Canada already has some of the worlds strictest fireworks regulations and requirements of the world, and every accident/incident just means they(NRCan) will make them even tighter. PLEASE, don't just "think" you're safe - KNOW for sure you are safe. it's not just you, that you are putting in jeopardy, it's all of us! Bye bye |
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Post by felix on Aug 26, 2020 14:00:10 GMT -5
I am confused by the "Bye bye" comment.
You made a post on a public fireworks forum, which opens the doors for comments. You have several very experienced industry experts giving their opinion, which is based on facts and testing.
Rack building is a very touchy subject in Canada. I would suggest that you utilize their expertise in a positive way.
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Post by londonfan on Aug 26, 2020 15:34:01 GMT -5
I have found this to be one of the most educational threads that I have read. I was almost embarrassed with my initial comments on structure and joinery.
The design advice given here goes to explain some of the construction that I have seen in cakes that I did not understand. I thought it was often "padding" to make the cake look bigger and badder.
Hmm. Safety. Who'd a thunk it.
This thread also made me look at my own rigs with new eyes and also re-think about new ones that I was still designing "in brain".
Thank you to those with the experience and training that know a lot more than me! Sharing that knowledge keeps all of us safer.
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Post by bigtop on Aug 27, 2020 11:08:24 GMT -5
If I give some information to someone that makes fireworks safer then it is a good day.
The ERD through the directive of the Display Fireworks Manual and the Explosives Regulations Part 18 section 436 (2) (b) (the mortars and mortar racks must be assembled, arranged and secured in a manner that minimizes the likelihood of harm to people and property if there is a premature explosion of a shell;) requires that in the case of an in mortar explosion of a shell the rack must remain standing with the mortars in their original orientation (usually that means pointing up with the exception of nautical shells).
This regulation by the ERD has made Display Fireworks shows safer. By comparison in the USA where the knowledge about constructing racks that do not fall over and blow apart is not as widespread, after every July 4th if you search the news there will be usually anywhere from 1 to 4 of these incidents. Some years have been worse when a batch of poorly constructed shells has been sold.
No matter what you do if you shoot enough fireworks a shell will blow up in the mortar. Why? because no one is perfect in executing their work and everyone is capable of making a mistake. The most common cause is a shell loaded upside down. All it takes is a moment of distraction while loading and the string or ring at the top of the shell breaks inverting the shell and in the mortar it goes. The guy that inspects hundreds of mortars has looked at so many shell tops while inspecting the loading that he misses the one that is upside down. This can happen to anybody. The second cause is the worker in the factory fails to perfectly seal the time fuse on the shell which causes the fire from the lift charge to ignite the shell before it leaves the mortar. These are very rare incidents but they will happen so you need to operate your fireworks show so that if it does happen everybody is safe.
To be safe you need to have racks that will not fall over and blow apart. If you have an incident like this and your racks do not comply with the regulations here is the punishment from the Explosives Act.
-"General punishment
22 (1) Every person who contravenes any provision of this Act or the regulations, for which no punishment has been provided, is guilty of an offence punishable on summary conviction and is liable
(a) for a first offence, to a fine not exceeding fifty thousand dollars; and
(b) for each subsequent offence, to a fine not exceeding one hundred thousand dollars."
Summary conviction means a criminal offence so your insurance company has no obligation to cover the damage, injury or loss of life caused by your criminal offence. You will also have a criminal record and be subject to the punishments above.
You also need to be away from the fireworks when it fires so the shooter is not injured or killed by an in mortar explosion. Even when hand lighting it is possible to be away from the firework when it fires by using time delay fuses. Shells should have a safety fuse (usually Green Viscoe Fuse) because in the Guidelines for Authorization of Consumer and Display Fireworks GENERAL REQUIREMENTS FOR DISPLAY FIREWORKS section 4.1 fusing it says "The part of the fuse to be ignited should be a safety fuse and should have a fuse cover that will protect the fuse from accidental ignition." This was introduced in the 2016 edition of the Guidelines for Authorization of Consumer and Display Fireworks so after the existing inventory of shells with black match on the shell fuse is used all shells should have the safety (time delay) fuse.
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