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Racks
Oct 2, 2020 10:02:08 GMT -5
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Post by djwolf on Oct 2, 2020 10:02:08 GMT -5
Hello all
I was wondering if anyone has plans on how to build wood racks for 1.3, 2 inch, 2.5 inch, and 3 inch tubes
I want them to be approved by the ERD, must pass tests
Thanks all
Djwolf
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Racks
Oct 2, 2020 10:53:06 GMT -5
Post by Aussie on Oct 2, 2020 10:53:06 GMT -5
Unfortunately that's something your going to have to research.
No display company is going to give you that information as there is too much liability
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Racks
Oct 5, 2020 11:32:43 GMT -5
pyrot likes this
Post by bigtop on Oct 5, 2020 11:32:43 GMT -5
Aussie is correct. It is doubtful that any company would supply you with plans to build racks. The liability is too great as supplying the plans says this works but there is no way of knowing if the racks will be properly constructed. I would not want to be in court explaining that I supplied plans to build a rack that complies with the regulations but the plans were not followed closely enough.
I have never built a wood rack. I highly recommend steel (which is what I use) or aluminum. If you are building lots of racks it can actually be less expensive to build steel grid racks. For instance I build a steel grid rack that holds 36 - 3 inch mortars for about $40.00 CAD in materials.
I understand that if you are building just a few racks wood costs less as you have to have a welder, a saw and maybe also a drill press depending on design of the rack. As well you have to buy steel in sufficient quantities to get a good price. Here in Manitoba you have to spend at least several hundred dollars at a steel distributor to get a reasonable price on the steel. You have to shop around as different steel distributors will have different quantity/pricing policies.
That being said I want pyros in Canada to be able to construct racks that are compliant with the regulations. It is good for all of us to not have accidents. So I will give some guidance on construction but you must test the rack design for yourself. This means a shell detonated in the mortar and the rack must remain standing with all the other mortars pointing up with the other mortars still securely held in position by the rack. Essentially the other mortars in the rack must remain functional as there can be other shells ignited by the explosion of the shell on the ground. For this reason once it is determined that the rack will survive a single shell exploded in a mortar the test should be repeated with all the mortars loaded as this is the way it will be used in shows. Needless to say attention must be paid to conducting testing safely. You do not know what will happen so your safety precautions should consider the worst case scenario of complete rack failure and shells being shot in any direction. I have used a shelter of 3/4" fir plywood with a 1/4" polycarbonate (Lexan) viewing window. You should video your test as proof that you tested your rack design and it works.
The first principal of safe rack design is you cannot hold an explosion in unless you do what the Japanese company Gunsmiths of Kunitomo did which was build all steel rack and mortar so heavy it needs to be moved with a forklift. So your design must not contain the mortar particularly where the shell sits and attention must be paid to eliminate pockets in the design that would hold or restrict the explosive gasses from escaping.
The second principal of safe rack design is the mortars must be far enough apart that the force of the explosion does not flatten or break into the adjacent mortars. If it flattens the mortar too much the shell in the adjacent mortar can't get out. If it breaks into the mortar it can ignite the shell or in some cases the shell in the adjacent mortar may be initiated by the shock of the explosion. If either of these things happen it can lead to many shell being initiated very quickly which can cause a very bad accident. This is achieved by separation. You probably do not want to go closer than 1"for 3" mortars and 1 1/2" is better as long as salutes are not fired out of the rack. for a 3" salute I would go a full 3" of separation at least. Any less even if the rack does not come apart you will probably flatten the adjacent mortars or initiate the adjacent shells from shock. Don't test a single rack by itself and then set up racks all up against each other as this introduces containment that you did not have in your test and may lead to a different result. separation of the mortars from the structure of the rack must also be considered. If you put a mortar too close to a part of the frame of the rack it can break from the force of the explosion.
There are some basic design principals that will help in designing a safe rack. Be certain to test any rack that you build. Use the most powerful shells that you are going to use in the rack to test it. I have found after doing quite a bit of rack testing that shells with higher metal powder content even if it is in the stars will produce a more powerful in mortar explosion. Silver wave for instance will produce a more powerful explosion because of the metal content in the stars. also be aware that shells may differ in the content of flash powder in the burst charge. This can make a significant difference in the power of the explosion. The third principal of safe rack design is the rack must be strong enough to withstand the force of the in mortar explosion without failing. This is where wood is really deficient as a rack material as compared to steel of aluminum. Good solid/strong wood must be used and it must fastened together very well. Fir plywood is a very strong wood material for rack construction. Hardwood pallet lumber can be bought from pallet manufacturers for a reasonable price. If using SPF construction lumber you have to be able to pick through the pile to find the solid fir or other more dense boards. The boards that are almost all white and very light will not work for you. Glue and screws are recommended. As an additional tip if you predrill just under the root size of the screw it takes much more force to pull the screw out. I used to work in design and prototyping and we did a test on this. Although there is variation because of the inconsistent density and grain structure of wood on average it takes more force to pull out a screw from a predrilled hole than if it is just driven into the wood.
So there are some design principals to build a safe rack. I hope this helps.
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Racks
Oct 5, 2020 18:15:08 GMT -5
Post by londonfan on Oct 5, 2020 18:15:08 GMT -5
Fantastic post bigtop!
I have a question about materials.
When using steel to build a rack, has anyone used punched angle steel and bolted it together, or does everyone prefer angle iron welded. I would assume that angle iron welded together is stronger, but I have also seen some pretty crappy welds that look good and then fail over time. I have also seen some amazingly strong bolted together steel. I know... Build it and test it, but I'm not licensed for the good stuff. Just wondering.
Also, once a rack is tested and in service, is there a recommended lifespan / re-test period?
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Post by bigtop on Oct 5, 2020 22:05:00 GMT -5
Yes bolts can be used to assemble racks. I assembled hundreds of racks with bolts before I bought a welder. The main advantage of welding is that it is much faster than drilling or punching and then bolting a rack together.
However there is an additional possibility if a bolt is holding a part that could be blown off the rack. Bolts are much harder than the mild steel used to construct racks. As a result they do not absorb energy as well as the mild steel does by stretching under the force of the explosion. When they fail the head of the bolt breaks off after stretching very little. Now you have a very dense piece of shrapnel that could really do some damage Of course the key to this happening is that the part that breaks the heads off must be stronger than the bolts. I found this out before I understood that you cannot hold an explosion in (first principal). I built a band of 1/8" x 1" steel flat bar that bolted to the rack frame to hold the mortar. The one at the bottom of the mortar (where the shell sits in the mortar) blew off and I am sure the bolt heads left at a very high speed after being subjected to that much force. The problem was solved by using a much lighter steel band that absorbed the energy by stretching and is not strong enough to rip the heads off the bolts. So yes bolts can be used but in the wrong place they can be a source of shrapnel. This is another reason testing your own racks is so important. you may do something in the construction that creates a hazard you never thought of.
By comparison the 2 bolts I used at each corner of the rack because of their position and what they hold together are not in any way a shrapnel hazard.
As far as a lifespan if not damaged and not left outside uncovered a rack will last a very long time. Wood plugs and fiberglass mortars will deteriorate if left uncovered outside. The steel is very heavy and even if left unpainted or not galvanized will probably last a lifetime. It is more about visual inspection for cracks and dents or anything broken.
I really am not the person to comment about durability and lifetime of wood racks as I have never used them. I would be sure that good strong construction and storage inside would extend their lifetime.
As far as retesting as long as you are faithfully building your racks to the design you tested you should not have to retest.
The only scenario I could see for a retest is if you got some new product that had a much more powerful burst charge than the product that you initially tested your rack with. This can be applicable with color shells if you start to use shells with a burst charge that has a high flash powder content. The most powerful color shells with flash powder burst charges will typically burst loud and very large very fast but the burn time of the stars is short. If you tested with a 3" salute you have already used the most powerful shell that can go in a 3" mortar. If you are testing 6" racks there are no salutes in Canada that size so you should use the most powerful 6" color shell you will use in the racks
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Racks
Oct 6, 2020 16:27:47 GMT -5
Post by pyrot on Oct 6, 2020 16:27:47 GMT -5
As I have posted in another thread, metal is my preferred choice for 1.3g products. WAAAAAAAY back in the day (the 90's LOL) we used to use wooden racks. On average, they would last around 1 year, which was 4-5 shows for us. it was the constant handling of them - loading and unloading from the trailer, and the screwing/nailing and then un-doing them from the support boards that were the death of them. A wooden rack will only survive 2-3 drops off the trailer before they start to break apart, and after about 10 nail/screw holes for the support boards, the wood in that spot gets VERY weak! In about 2000, we started converting over to steel racks - some we purchased, many we had made at a welding shop. We are still using those same racks today - only needing to replace the mortar tubes as they get worn. The initial cost of metal may be higher at the start, but in the long run works out to be way cheaper.
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Racks
Nov 17, 2020 5:11:28 GMT -5
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Post by fireworks4u on Nov 17, 2020 5:11:28 GMT -5
Hello all I was wondering if anyone has plans on how to build wood racks for 1.3, 2 inch, 2.5 inch, and 3 inch tubes I want them to be approved by the ERD, must pass tests Thanks all Djwolf God this is a can of worms..... you can pm me if you want
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