Saving Money By Making
Your Own Motors & Reloads
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One of the great myths of high power rocketry is that you do not save any money making your own motors and reloads. The truth is that the savings are there starting with the "G" class motor and the savings become more dramatic as you move up in motor class. The best way to show this is to actually cost out a particular case.
First, there are a couple of items that you will need to buy on a one time only basis regardless of what size motor or how many you plan to make. The first item is a good laboratory balance. A mechanical triple beam balance with extra weights can be bought for about $125 new. There are a few electronic balances with adequate accuracy for the same amount or a little more. The second item you will want is an electric mixer. While you can mix the propellant by hand, it is really nice to use an electric mixer for propellant batches a half pound or more. A simple "egg beater" type mixer will work, but the best mixer is the low end Kitchen Aid mixer. Its mixing action gives the best quality propellant. For our example, we bought a lab balance for $125 and a Kitchen Aid mixer for $180 for a total cost in equipment of $305.
- Lab Balance = $125
- Electric Mixer = $180
Total Cost For One Time Only Items = $305
The cost of the propellant is about $5 per pound plus or minus $2 depending on what formula you use. Now, lets look at a typical "J" motor, such as the 54mm Aerotech J90W. It sells for $63.95 (Major discount dealers price on Oct. 14, 2002). It contains 0.861 lbs of propellant. The kit also includes nozzles, o-rings, sleeves, etc.
You could make a J motor out of 1.25" PVC pipe and fittings where you cast the propellant into 1" PVC pipe cartridges that slide into the 1.25" PVC pipe chamber. Using the construction techniques in our bookset "How To Make Amateur Rockets" the motor cost is as follows:
- Propellant cost ($5/lb * 0.861) = $4.31
- PVC fittings = $1.75
- PVC pipe for chamber = $1.50
- PVC pipe for propellant cartridges = $1.50
- Water putty for nozzle = $0.75
- Phenolic insert for nozzle = $0.75
- Glue and primer consumed = $0.25
- Silicone rubber consumed = $0.25
Total Cost For A J90 Motor = $11.06
You Saved $52.89 By Making Your Own J90
Motor Rather Than Buying A Reload Kit!!!
But what about the cost of the mixer and balance? Well, after you've made only six J90 motors instead of buying them commercially, you've saved enough to cover the cost of the mixer and balance. From that point on, the savings are yours to fly more or to spend on other things.
If you want to make your own reload, the cost will be about $20 higher as you have to buy OEM parts from RCS motor parts. In this case, it will take about 10 homemade reloads to cover the cost of the balance and mixer.
You Saved About $33 By Making Your Own
J90 Reload Rather Than Buying A Reload Kit!!!
The Savings Are Real When You Start Making
Your Own Motors and Reloads!
CP Technologies is making it easy for you to get started with our bookset "How To Make Amateur Rockets" and our motor & reload design page. So, what are you waiting for? The sooner you start making your own motors or reloads, the sooner you will start saving your hard earn money.