How to Build a Fire-Extinguisher Cart:

There are a lot of designs out there for fire-extinguisher carts, but we have had a number of requests for the details on ours, so here they are.  The most important things that you need for a good fire extinguisher cart are:

(1)  Good wheels.  The wheels that you use should be as frictionless as possible, since the harder they are to turn, the faster the cart will slow down.  Our cart is built using 22 rollerblade wheels (72 mm), since they are specifically designed to be low-friction:

(2)  The cart.  Our cart is made out of wood and painted blue.   It should have somewhere for the fire-extinguisher to attach.  This is important; if the fire-extinguisher isn't attached well, it could fly off and hurt someone.  It should also have somewhere to sit, either built in or separate.   Our cart has a separate plastic stool to sit on.

(3)  Point of attachment.  The fire extinguisher should have something secure to attach to the cart.  You could probably build one of these with the tank permanently attached, but it would make it harder when you need to refill the tank.  Being able to detach the tank also helps if you're concerned with making it portable.

(4)  Fire-extinguisher.  The bigger a fire-extinguisher you get, the more use you will be able to get out of it before filling it up again.  Our fire-extinguisher is filled with compressed carbon dioxide gas and weighs 38 pounds when full (vs. 29 pounds empty).  One full tank of carbon dioxide is good for about 6-10 good rides.  You can get compressed carbon dioxide from your local fire equipment supply store.  (Ask your local fire department if you don't know where this is.)   Remember, though, this is a real fire-extinguisher with contents under pressure!   Make sure it has a safety catch on the handle and have the tank checked professionally every year or so.

(5)  Gas exhaust.  There's two ways to go about this.  The first way is to point the extinguisher away from the person riding the cart.  This will keep the exhaust from hitting the rider in the face.  But it will probably mean that the cart will have to be ridden backwards.  (The first picture here is of our old cart, which was designed this way.)  We didn't like this much, so we use a semi-complicated system of valves and a hose to move the exhaust opening down to the bottom of the tank.  The gas actually gets shot out from under the stool that the rider sits on.

Put it all together and you get an awesome cart that's a lot of fun to ride!  It is a bit loud, though, so you may want to cover your ears.  And be weary of any loose items like papers near the exhaust, since they may be sent flying!