Bruce
That looks like a good test stand mechanically, however DATAQ has greatly expanded their product line, so the specific data acquisition recommendations in the plans might be outdated.
Check out
https://www.dataq.com/ for the latest product and pricing info.
The load cell selections will depend on the size of the motors. Bob Fortune of
https://www.aeroconsystems.com/ has a variety of load cells, amplifiers, and electronics packages for sale at good prices. It's also worth checking out
https://www.aeroconsystems.com/ts_pics/ts_pics.htm to see other folks test stands.
Rocketmaniac
You said
I want to get into EX more for two reasons. One, it is cheaper and it will allow me to burn more AP for the same amount of money.....
I agree with Bruce and don't condone most EX activities. I know many EX folks will disagree with our opinion, but it's not cheaper to do EX APCP than it is to buy commercial APCP motors, at least if you do it safely. The knowledgable EXers know this, but many EXers cut corners and depend on luck to keep their finger and toes attached. The cost of the AP and other raw chemicals in a motor is at most 20% of the retail price of the motor. What you are not factoring in is the cost of the equipment required to safely mix and compound the propellant and process it into a finished propellant grain. A finished APCP fuel grain is pretty safe, however certain steps in the manufacturing process are quite hazardous. That's where the substantial investment is, at least if you want to make commercial quality APCP motors safely.
The professional hobby rocket motor industry developed NFPA 1125 which lists the minimum requirements for safe propellant manufacturing practices. Few EXers manufacture their propellants in this manner. Is it because they know more than the experts? I don't think so. It's just the opposite. They simply don't believe that making propellants is hazzardous. All of the big boys have had accidents, and in principle, they took all reasonable efforts to prevent the accident. In my opinion as a professional chemist and as an emergency HazMat responder, it's a bit cavalier for the EX community to do what they do the way they do it.
Propellant chemicals start out as finely powdered metals and oxidizers. Handling fine powders represent a potential fire/explosive hazzard simply due to the very high surface area to volume ratio, and represents an inhalation hazzard as well. All it takes is a spark from static electricity to set a dust explosion. (Even common everyday powders can and do expode. Ever hear of a grain elevator or flour explosion? This does happen with some regularity in agricultural areas. It's rather impressive to see the residual powder in a coffee can going off.)
It also difficult to these chemicals as fine powders. Since they have large surface areas, they naturally absorb humidity (water) from the air. Water is detrimental to the formulation and compounding of the propellant grain. It causes clumping, polymerization problems and voids in the propellant grain. The main problem with the early Ellis manufactured AeroTech propellant grains was the lack of environmental controls in the manufacturing process which are necessitated by the high humidity conditions in Texas. A lot of those motors CATOed destroying casings and rockets.
The additives, plastizers, polymerizing agents and rubber monomers used in APCP motors include some rather nasty chemicals and present a chemical hazzard. Most EXers are probably unaware of the long-term hazzards associated with some of these chemicals, and don't use the right personal protection equipment.
You may also have to core the grain, or slot it, or cut it to length. These operations can be dangerous and can result in a fire or explosion if not done properly, particularly if waste propellant shaving are present. It was the improper operation of a finishing machine that caused the AeroTech fire.
Manufacturing of propellants should be conducted in a separate isolated building that insures the safey of the general public. All equipment should be grounded and explosion proof where required, not simply the household variety of mixers, etc. The facility should be well ventilated and very clean. You also have to have all the personal protection equipment such as dust masks, gloves, face shields, etc, and a clear way out of the building. The one item you don't need or want is a fire extinguisher. You don't try to fight a propellnt fire, you get out immediately.
Fine powders need to be kept dry. This means several vacuum ovens and/or dessicator. All polymers should be degassed to reduce the probability of voids in the fuel grain. You need lots of other rather expensive equipment and a test stand.... I could go on, but it's time to eat dinner.
The bottom line is that you need to spend many thousands to tens of thousand of dollars to make commercial quality APCP rocket motors safely. I doubt, that most EXers are willing to make that kind of financial committment. Although the probability of an accident is not very high if reasonable precautions are taken, the personal cost can be very high if you or your family or friends are injured or killed by an accident. Each individual has to determine for themselves if it's worth it.
Bob Krech
) heaps of money.
