Knowledgebase: Pyro 101
WASP Stinger
Posted by Jason Musselwhite on 16 January 2012 04:58 PM

Gummed kraft-paper tape is used in the WASP shell-taping system.
35 lb tape will lay down a lot easier and create a smoother paste job.
Of course you will need slightly more 35 lb tape to provide an equal level of containment compared to 60 lb tape.

These sizes are designed to work with the shell files provided with the WASP3 software. It also possible to use sizes other than those indicated in the above chart. For example, if you intend to use 1” tape on an 8” shell, you would want to reduce the “tape spacing” variable and increase the “wraps per layer” variable in the specific shell file you are working with.

Safety cautions about your WASP machine:
Locate the power supplies and the controller away from the WASP machine and any live materials.
When the motors of the WASP are turning, the wires and extension cables are carrying significant DC current.
THESE WIRES WILL ARC VIGORIOUSLY if crossed or cut. All cables and wires must be protected from physical damage.
The shell should be completely sealed before it is placed upon the WASP machine.
If the shell leaks during machine operation, it must be removed and sealed properly.
Strain relief must be provided for the cables coming out of the two motors and the connecting extension cables.
Locate the controller so that the on/off switch is easily accessible during operation.
If the machine labors during operation, the bearing blocks may be located too close to each other, causing the shell to bind on the bearings. Pause the machine, and adjust the bearings blocks so that they are only lightly touching the shell.
Never connect or disconnect any cables to your WASP machine or the controller or your computer while the unit is powered up. Always remove power to the power supplies before changing any cables.

Maintenance:
Before and after each days use, the (4) transfer bearings should be sprayed with a lubricant such as WD-40.
Check all wires and connections before each days use.
Drive wheels can be cleaned with soap and water if required.
Tape return wheels should be lubricated with light machine oil at the axle, to ensure that the tape is traveling freely to the WASP machine.

Preparing Shells for WASPing:
I’ll show the original method of preparing a shell for taping on a WASP: installing a passfire tube leading to the center of the shell from a punched hole in the casing, with the hole being plugged with a magnet which is taped over on the outside of the shell with masking tape.  The shell is taped on the machine, the magnet is found with another magnet, and the damp machine-applied gummed-tape is carefully cut with a razor knife and removed in a circle where the casing-magnet is. The magnet is then removed, and the inside of the passfire tube is exposed, ready to accept a glued-in time fuse once the shell is dry.

Jim has developed a system where the magnet can be held in place with a plastic “cap plug”. This prevents any possibility of a spark being produced when the gummed-tape over the magnet is sliced away with a razor-knife.
But, recently there have been some alternative methods of assembly, and finding the pass fire tube, in use by some WASP users.

With some small shells, the pass fire tube is plugged and small knot of masking tape is placed on the outside of the shell casing and protruding just a bit from its surface. The machine can handle taping a shell with a small knot on its surface just fine. After the machine-taping, the bump is apparent and the opening can be opened with a razor knife as described above.

Some folks punch a hole in the shell casing large enough for the pass fire tube to pass through it completely, and protrude just a bit, which creates a bump in the tape layers as described above.

Other folks are using sawed off aluminum gutter spikes, the shaft of which slides down into the pass fire tube, and the head of which stays outside the casing and creates the necessary bump in the tape layers.

In some cases with small shells, the gutter spike process is employed, but the pass fire tube is eliminated. When the taped layers are carved away from the bump, and the gutter spike is removed, a recess in the shell’s inner star and burst construction remains, and the cross-matched time fuse is inserted into this recess and is glued in place.

And in other cases, folks are just assembling small shells without a pass fire tube or bump at all. After machine-taping, a little round section of the tape layers is carved out, and once the shell is dry, a sharp awl is used to carefully pierce the casing and create a recess into which a cross-matched time fuse can be inserted.

Removing the Casing Magnet and Opening Up the Pass Fire Tube:
While the tape is damp, the stack of magnets is used to find the magnet in the shell’s casing. A mark, about 1/8” bigger than the magnet all the way around, is made to identify the magnet’s location.

Note: The process which is described next, is just one of the options for finding the pass fire tube end, and removing the tape over it, as described in the section on assembling the shell. These actual shell construction processes are left up to the individual builder, and this process is described simply to point you in one possible direction. The possibilities are up to your imagination.

A very sharp-bladed utility-knife is then used to carve out a plug of the damp tape, while carefully avoiding hitting the magnet with the knife. The plug of damp tape is removed, and the casing-magnet is pulled from its hole with the stack of magnets. The hole is immediately covered with masking tape to protect it from sparks until shell-fusing is to be accomplished.

Fusing and Finishing the Dry WASPed Shell:
A piece of ¼” time fuse, of your desired duration/length, is cross-matched on its inside-end. A mark is put near the outside end where the cross-matching is to go once the shell is fused.

The masking tape covering the open pass fire tube is removed. It’s a good idea to pierce the tissue paper at the inside end of the pass fire tube, and any tissue paper layers from the shell assembly which obstruct that end, with a long bamboo skewer or something similar.

Some long pieces of black match should be put into the pass fire tube to transfer fire from the time-fuse cross-match to the shell’s center.

Then the cross-matched end of the time fuse is inserted into the pass fire tube. Keep about ¾” of the time fuse, between the shell casing and the outside-cross-matching mark, outside the shell.

Tuck a little twisted tissue paper into the pass fire tube, around the time fuse, to prevent glue from dripping down into the tube when the fuse is glued in. The idea is to block the gap in the pass fire tube around the fuse, while leaving all of the casing and taping surfaces exposed for glue to adhere to.

Alignment:
The drive-wheel motor-mounts should be sitting square to the cross member.
The tape-application wheel should sit centered between the left-side ball-bearings when it is lowered all the way.
The spine should be square to the cross member.
The right-side bearing-block should be sitting level.
The tape-application-arm tensioning spring-bracket should be sitting square to the upright.
These alignments should be checked regularly as the machine is used, and after it has been transported to a different location.

General Maintenance:
It has already been mentioned that the steel ball-bearing guides need to be sprayed with WD-40 after every taping session.
Avoid cross-threading or over-tightening bolts and nuts.
Some light machine oil, such as 3-in-1 oil, should be applied lightly to the axles of the tape-application wheel and the tape guide rollers.
Keep the Stinger covered to prevent dust from accumulating on the oiled surfaces and the rubber wheels.
Do not use a WASP with dangling jewelry, pony tails, or open loose-fitting clothing.
As with any machinery, there is a risk of such things becoming entangled in the moving parts.

 

The WASP Owner’s Group:
A Yahoo discussion group, called the WOG for short, has been created to foster creative discussions between WASP owners.
The group can be found at: http://groups.yahoo.com/group/WaspOwnersGroup/

You have to be a member to access the discussion, though. For information, contact:
Jim Widmann at widpyro@charter.net or Tom Dimock at tad1@cornell.edu

 

 

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