chillman,
I had an alternate assignment on my days off from being a SDFD fireman and it involved mounting hardware, tools, equipment, and much more in fire trucks for years. Many times, we did not use the supplied bracketry that came with fire extinguishers. Sometimes we did but, not always. What we used in lots of circumstances was what's known as "B/A" brackets. That's "Breathing Apparatus" brackets. They are a spring loaded clamp that simply grabs hold of the air cylinder for the breathing apparatus and holds it in place.
When it's needed, you just give a good pull and it's off the bracket. There's no mechanisms or locks or manipulations to get them out of the bracket, just pull on it. And, they do exactly what we asked of them, THEY HELD. We used the same brackets on Fire extinguishers too. Not one ever dislodged from that type of bracket.
Those brackets can be purchased at any fire equipment supply store. There are many throughout the country. They are extremely simple to mount. Just two 1/4"x20 bolts with large washers and nuts (or in our case, "Nut-serts" on the interior walls of the fire trucks compartments. That's it. Now, one thing here, they do come in different sizes for different sized air cylinders. So, you'd have to know the diameter of your extinguisher before getting one.
And, as has been stated, try to mount it low so that it's supported by the floor in the compartment. We created supports so hold the weight so that we could mount them higher on a compartment wall and utilize space below it. Good luck.
Scott
