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Submited anonymously to Short Fuse Pyro The Webmasters have NOT tried this particular motor, so procede with caution.


1 Paper tube 5/8 IDx 5 1/2" walls-1/8. It would be a good Idea to have the walls of this tube to be rolled with a fire resistant adhesive like Sodium Silicate.

Durham's rock hard putty(for the nozzle)

A drill with bits sizes 1/8" and 11/64"

Thin speaker wire about 8" long

1-2" of nichrome wire(take apart a old hair dryer)

Propellant(see formula)

Igniter comp.(see formula)

Nitrocellulose Lacquer (40% or so)

mixing bowl

mixing spoon or something of the similar

a scale accurate to 1/10 of a gram

4 1/8" nails

A curing chamber

1 hour epoxy

Nozzle preparation:

First take your tube and drill 2 1/8 wholes all the way through the walls about 1/8 form the base. Put the nails in the wholes you just drilled. It should look like this ( . . ) when ( is the walls and . is the drill wholes. Take a pair of wire cutters and cut the ends of the nails off that are sticking out from the tube. Next mix up the water putty to the constancy of a thick plaster. Holding the engine nozzle up side up, use your fingers and get a fair amount of putty in the nozzle area. Important: make sure that the nail's are covered with putty at least 1/8" on both sides. The nozzle should be aprox. 1/4" long inside of the tube. Let sit on a piece of wax paper (nozzle end on the paper)for 1-2 days at room temp (70F)or higher. Then drill out a whole for the gasses to escape. The whole should be small to start out with, then as you go, you can decrease the size to give you more thrust(but not to small!). You should start with a nozzle throat diameter of 11/64".

Propellant Manufacturing:
Note that this is only propellant that I have tried in this particular motor. there are many others that can be used, but I have not tried them. This one worked well for me. I used the following with success,

AP200m sph. 75

DER-331 2.75

PBAN 13.5

Fe2O3 1


TBA .75

Al 2m sph* 1

*The Al is used to preheat the propellant when burning. It is not mandatory to have it included in this composition. Also beginners should avoid using such fine Al because of the dangers of it. This fuel burns cooler than most AP composite fuels because of the lack of metallic fuels. This allows the use on Water putty as a nozzle material. Weigh then Mix together all of the liquids including the curative until homogeneous(2-3min) in your mixing bowl. Then add the Fe2O3 and Al(optional). After the liquid is uniformly red, start poring in the AP and mixing it together for 10-15 minutes. Your propellant is ready. It will not cure at room temp so don't worry about it curing on you as you continue with the next steps. Take a piece of paper(binder paper will work for all of us "pov's" as Lindsey would say) and roll it into a tube with your hands that is smaller that the Id of the tube that you are using. Put the tube into the engine. Once it is in the engine, let go of the tube and it will straighten out into the right size of the propellant liner. simply place a piece of tape so it don't unroll. You may want to put some stick glue on the last wrap of paper once it is out of the motor so it doesn't unravel. This is what you are going to cast your propellant into. Cut the liner to the length of your tube to 5" long.

Casting the propellant

You propellant liner is what you are going to be using cast your propellant in. take your spoon out of the propellant in your mixing bowl and put it aside for now. Take the tube and press it against the propellant in the mixing bowl. You are going to be loading it from the bottom up. Keep doing this until the liner is full to the top. Once it is full, place a piece of tape over both ends and set it aside for a little bit.

The curing chamber:

PBAN propellants need a higher temp in order to properly cross link(cure). The temp to cure this propellant is 130-140F. You need a toaster oven and a accurate thermometer. It is important that you never use your propellant oven as a food oven because of poison reasons. Let the oven run for 10 min or so and check the temp. Against the nob until the temp is about 135F. You may want to mark where the nob is so you don't have to find where the ideal temp is every time you make a propellant. Place the oven in a spot away form any structures (especially your work shop) and put a gallon of water or more near the oven. Plug it in and place your propellant in. Now comes the hard part-the wait. You must wait at least 2 days until you take your propellant out of the oven.

The core

These motors must have a core to supply the surface area needed for usable thrust. take the fully cured grain and drill out a whole in the exact center of the grain. The rule of thumb on core diameters is 3x the nozzle throat diameter. So on these motors you need a __________ diameter Core. To make the core in this motor, you will drill it out. But first, cut the propellant into three equal pieces. Then drill out the propellant. It is best if you go slowly in order to retard heat build up.

Finishing the motor

Now take the three propellant grains that you made and slide them down the motor tube. There should be a 1/2" empty space at the top of the tube. If there is more than 1/2" cut some propellant off of the last grain until it is 1/2". If there is less there isn't much that you can do. Put 1/2 of a Kleenex into this whole and compact a little. now poor in some 1 hour epoxy until it is full to the top. Depending upon the propellant, you may want to put in 1-2 nails through the walls to keep the rear closure from flying off while thrusting. Wait until the epoxy has dried (give it one day or so) and you are done with the motor!

The igniter(e-mach)

This is one of the most important items that you will be making. You can use a commercial e-mach or make your own. To make your own you need to take your speaker wire and peel the two wires off each outer for about 1". Cut one wire off at 3/4" and take 1/4" of the insulation off of it. On the longer wire, cut 1/4" of the insulation off. now take your nichrome wire and solder one end to the shorter end. Wrap the nichrome around the insulation until you reach the exposed wire on the longer piece. Solder the outer end of the nichrome to the exposed end. Now making igniters is a real pain, so you may want to make more that one at a time (I make 50 at a time). A good igniter comp. is:

KNO3 70

C 7.5

S 5

Al 200m 5

Mg 100m 5

Mg 200m 2.5

Dex 5 {ABW NOTE: add in a few %'s of H3BO3 to stop any rxn btween the Al and KNO3}

The KN,Dex,C, and,S are ball milled together for 3 hours. Add the metallic fuels and moisten with Isopropyl Alcohol. Then dip in the leads into the slurry. You may want to dip them twice to get the wright girth. Once dry, dip them in Nitrocellulose lacquer(ping pong balls in acetone) and let dry. Test them for resistance and you are ready. If you use Hair dryer Nichrome wire, you need 12 volts to get them to work.

Static firing I recommend that you static fire your engine at least 2 times to make sure that it won't go BOOOMMM.

To make a static firing set up, you can use a piece of 1/8 Al sheet that is about 6x4. The size doesn't matter that much as long as it won't tip over during firing. Find a piece of Al or Steel rod that is just shorter than your motor and weld it to the base. Now get 4 hose clamps and attach your motor to the rod. Drive to your launch/test site and put the igniter in the motor. You should be at least 150 feet away from the motor when you push the button. I also recommend that you video tape the static fire so you can get the burn time, the amount of chuffs(if any), flame plume est...