Benefits of jigs
- Faster construction
- Fewer errors
- Production of interchangeable parts
Drill Jig for LV2 18" tube modules
Part of the LV2 airframe is constructed from interchangeable modules. These are fashioned from milled-down 18" long, 5.25" diameter, 1/8" wall thickness, aluminum tubes. The modules couple together using a short, close fitting internal sleeve, which is attached to one end of each module. The modules are held together using screws threaded through each module into the next module's sleeve. During final assembly a smooth outer skin is slid over the assembled modules and attached using more screws at the module mid-points.
If the modules are to be interchangeable, the screw locations must be held to a tolerance of a few thousandths of an inch. The drill jig allows this by rigidly holding each module as it is drilled.
In operation the drill jig holds a module between several jig clamps which are precisely located on the jig plate. The module can be accurately drilled using an ordinary hand drill because of the drill guiding bushings (specifically Type-SF bushings from American Drill Bushing Company http://www.americandrillbushing.com ) Each clamp allows one hole to be drilled, then the module is rotated by either 1/8th or 1/16th turn until an index pin aligns with a previously-drilled hole. This continues until all the holes are drilled.
Slip fit (Type-SF) drill bushings can be changed quickly, allowing operations using different diameter tools through the same hole in the jig, so drilling and counter boring can be done rapidly without moving the work piece.
The drill jig is also designed to hold and align the outer skin while the holes for the skin-attaching screws are drilled.
- Jig-Clamp drawings
- Jig-Plate drawings
Because commercial clamps that could easily hold the modules in the jigs have been hard to get, we could make our own hold-down clamps. These would attach to the jigs using a single 1/4-20 thumb screw.
Fin Jig for LV2 Fin Canister
The first edition of LV2 used fiberglass fins. This was done essentially for scheduling reasons. However we believe that fiberglass layup is too hard, and that fiberglass fins are too hard to straighten or repair. Therefore we want to move to welded-on aluminum fins. This requires a jig to hold the fins during welding, and to index each successive fin to its proper angle.
The propose design is very similar to the drill jig above. Instead of a module, the fin jig holds a slip-on fin can which slides over the bottom section of the rocket. In part this is done for modularity. Also the bottom section is all motor, and welding to the pressure casing would require heat treating and inspection.
The holding mechanism for the fin can is sectioned into two parts. This supposedly means it's easier to make, but the piece could certainly be made as a single unit. The two pieces are the tube clamp, which holds the actual fin can, and the bracket that connects the tube clamp to the fin jig plate.
- Fin Tube Clamp drawings
- Fin Jig Bracket drawings
Some of these drawings are in DXF format. Many CAD programs can read DXF files. One open source CAD program that can is available at http://www.qcad.org