75mm reload instructions.

Assembly procedure 75mm R&R Reloadable motor

1. General order of assembly: Install nozzle first.  Do that by
following these steps first:

2. Install a snap ring on one end of the motor casing tube, into the
further groove inside.  The thrust ring end if there is one.

3. Install a snap ring spacer (short pure cylinder) on that end of the
motor casing tube, against the further snap ring.

4. Install a second snap ring pressing the snap ring spacer against the
first ring.  Be sure all snap rings are seated.

5. Slide the nozzle compression ring from the bulkhead end of the tube
(nozzle = nipple), the one with a rectangular ridge on it, with the flat
side toward the nozzle snap ring.

6. Put grease all around an o-ring and slide it in place against the
nipple side of the nozzle compression ring and seated all around against
the motor casing tube.

7. Slide the liner onto the base of the nozzle and check for snug fit. 
If it is not snug use a layer of masking tape smoothly wraped on the
nozzle base to get the proper fit.  If the fit is too tight with no tape
use 320 grit sandpaper to eliminate any burr on the ends of the tube.

8. Slide the nozzle and liner assembly into the bulkhead end of the case
all the way through the case and snap rings and snap ring spacer until
the nozzle seats against the compression ring and o-ring.  Twist to
seat.  If the liner is tight in the casing, sand the outside surface
with 320 grit until it fits correctly.  This tube sometimes has external
surface imperfections.

9. Insert a propellant grain into the liner.  If you deburred it, it
should fit smoothly but with small tolerance.  Insert another grain one
after another until all the grains are installed.  If one grain has a
bigger core hole, it goes toward the nozzle and MUST be inserted first. 
Biggest holes nearest the nozzle and first.

10. Insert the igniter grain into the bulkhead.  Check for snug fit so
it does not pop out.

11. Insert the bulkhead into the motor case, seated into the liner end,
with the igniter grain facing inward and the smaller cap facing outward.

12. Put grease all around an o-ring and slide it in place against the
bulkhead and seated all around against the motor casing tube.

13. Install the bulkhead compression ring (narrow flat top after the
bevel) and press in place with the wider flat side facing outward.

14. Install a snap ring on the deepest groove, pressing the bulkhead
compression ring in place.

15. Install the snap ring spacer.

16. Install the final snap ring.

17. The igniter must be located at the head end of the motor. Most
people use through the nozzle igniters and this can be done manually or
as an element of the step when inserting the igniter grain itself if
doing so at the firing site.

18. There are also options with delay trains that pass through and
ignite an ejection charge or a version of bulkhead that has only a head
end igniter installed, purely plugged bulkheads with no igniter grains
or other features, and even special staging systems.

19. When the motor ignites and comes up to pressure the compression
rings all seat and the motor becomes more sealed as pressure increases.

20. When the motor is fired and expended, dissassemble it the same day
for best results and wipe down all metallic surfaces with a baby wipe or
solvent cloth.  Remove the liner and paper remnants of the propellant
liners, delays or igniter grains and any igniters.  These parts are not
reuseable.

21. Scrape any slag off the base of the nozzle with a knife or dowel. 
Be careful, the graphite nozzle and throat are fragile.

22. If the motor will be refired right away, place the casing (only) in
cold water to lower its temperature for best reliability during
ignition.  If any portion of the nozzle is placed in water make sure it
is the thick aluminum base but not touching the graphite.  Where
possible cool nozzles by air and not by water except perhaps a light
spray bottle.

Report variances or errors in these instructions and report any
experiences good or bad to us for product development purposes.