Several very hard breaking shells are now on the market. Always follow manufacturer recommendations. 

Some of the Consumer shells do not have the explosive force capable of a catastrophic failure of a HDPE Mortar or Rack. These tests were done with a shell that can cause this type of failure.

The most important quality of any Mortar rack is to ensure that the mortars are pointed upright at all times, even after a catastrophic failure.  If the adjacent mortars fall, they may send shells towards the crowd.

Our testing has determined that failure points must be built into the rack. The destructive forces of the larger breaking shells on the market WILL exit the rack, HOW they do it is key.

With a solid side, the blast will blow the side off, allowing the mortars to fall to the ground.

Adding fasteners does not prevent the sides from separating, it only forces the blast to destroy the side. 

(Yes, this was a CONSUMER fireworks shell)

It was found that using TWO pieces for the side allowed a open area for the explosive forces to escape the rack.

With a strip of plywood top and bottom, the results were better, but most were able to blow the bottom piece of plywood off. This rack preformed adequately, the remaining mortars remained upright.

As this test shows, in 1 shot, the bottom plywood was blown off completely on one side, mostly on the other. 

The sides of the rack is reinforced with a piece of 1/2" plywood to prevent the 2X material splitting in half.  If the side board fails, the rack WILL fall into 2 pieces without this added reinforcement.

When a piece of OSB is used as the bottom slat, the force of the blast breaks the OSB locally while leaving most of the OSB at the bottom intact and not transferring as much force to the rest of the rack as when plywood is used.

This picture was after 1 failed shell, the only damage was a blown out section of the bottom OSB slat.

After the 2nd shot, the same type of damage resulted.  The exlposive force was able to quickly leave the rack and not transfer to the sides to cause extensive damage.

Next, 3 more shells were blown at the same time.

After 5 shots, the rack is badly damaged, but the mortars are still upright, and no mortars are pointing towards the audience.

The above picture shows how dangerous Chain Fusing can be.  Any type of finale/fusing should be performed by an experience and licensed pyrotechnician.  

NOTE TO CUSTOMERS WITH SOLID SIDE RACKS:

Your racks can be modified to better hold up to a catastrophic failure of a shell.

4" from the base, cut a 1/2" deep groove with a circular saw.

Remove the top 2/3 of the OSB. 

Cutting a horizontal cut will make it easier to remove the OSB

Add a new 3/4" plywood slat to the top portion of the rack as shown in the picture.

On each side, a piece of plywood is attached to prevent the side board from breaking and splitting the rack in half.

If you do not have the available lumber to make these modifications, contact us at Pyrogear and we will ship you 2 new top slats, 2 side boards for reinforcement and necessary screws for installation.

Screw on a new 3/4" plywood slat to the top using 3 - 2 1/2" or 3"  #8 screws (decking screws work well).  Although not necessary, it is easier to drill a 1/8" pilot hole first.