Brief:
The Animal Motor Works (AMW), which has recently merged with Cesaroni Technologies, M2500 Green Gorilla is a high power rocket motor reload for AMW's giant 75-7600 motor casing . This 40.9 inch motor casing fits 3 inch motor mounts and the reload is the most powerful commercial 3-inch motor reload in our hobby. You must be Level 3 certified (as recognized by NAR and Tripoli, Level 4 for CAR) to purchase and use one of these reloads. The motor isn't cheap. For the entire case assembly, the list price is $375. The reload costs $400. However, this motor (266oz total weight, 150oz propellant weight) provides impressive performance and gives even hot research loads a run for their money.

Construction:
The reload includes the following parts:

• 1 phenolic liner
• 5 propellant grains
• 2 aft O-rings
• 2 forward O-rings
• 1 tracking smoke grain

Other items needed:

• AMW 75-7600casing with the forward closure, graphite nozzle, fore and aft internal snap rings, a metal nozzle washer, and an external snap ring used as a thrust ring
• Synthetic grease
• paper towels
• clean work area

Perhaps the most important thing to do when assembling the motor is to have the right tools and a dirt free workspace to avoid contamination of your O-rings. To insert the internal snap rings during assembly, I would highly recommend that you follow AMW's suggestion and purchase snap ring pliers from McMaster Carr. For the AMW 75mm cases, order PN 7131A21 with 0.108 inch tips. As for the kind of lubricant to use, AMW suggests high service temperature synthetic grease. I use Amsoil Multi-Purpose Synthetic Grease #2 Lithium Complex. It has a service temperature of 500 degrees Fahrenheit, is easy to clean, and protects the casing and your lining as well as your O-rings. None of my liners have burned through after I used this stuff so I heartily recommend it.

Assembling the reload is fairly straightforward. Grease two of the O-rings and place them into the grooves of the graphite nozzle. Lightly grease the inner diameter of the case on both ends. With a twisting motion, install the nozzle assembly in the end of the case with the external snap ring. The nozzle is oriented where the flat face faces out the rear to accept the nozzle washer. Install the greased steel nozzle washer against the nozzle then use your snap ring pliers to install one of the internal snap rings in front of the nozzle washer. Be sure to wear eye protection whenever you use the snap ring pliers to protect from the ring hitting you in the face.

Now install the five propellant grains and the tracking smoke grain into the phenolic liner. The order of the grains is important to ensure that the motor performs properly. The longest grain should be marked as #5 and placed next to the nozzle. The smallest grain should be marked as #1 and placed just below the tracking smoke grain. Disregard the instruction diagram that indicates the tracking smoke grain fits into a cavity in the forward closure. In reality, the forward closure does not possess such a cavity. Instead, the tracking smoke grain is placed at the top of the grain stack with the white end facing out. Lightly grease the outside of the liner tube and install the entire assembly with grain #5 down into the motor casing from the top and seat the assembly against the nozzle. Then place two greased O-rings into the slots on the forward closure and use a twisting motion to install the forward closure assembly into the casing until it's seated against the liner. Finally, insert the final internal snap ring to lock the forward closure in place.

Now, don't be too surprised when you try to heft the assembled motor and nearly keel over. The entire assembly weighs nearly 17 pounds so you know that you've got your hands on a real motor!

Finishing:
Due to the error in the instructions concerning the tracking smoke delay/forward closure diagram, I would take off half a point in my construction rating.

Construction Rating: 4 out of 5

Flight:
A 12V launcher is required to ensure that there is a strong enough charge to fire the igniter. However, once it's lit, watch out! The Green Gorilla motor produces an impressive green flame for its exhaust that, for the life of me, called to mind the "Flame of Life" from H. Rider Haggard's classic novel, She, as well as fabulous white tracking smoke. The motor sent my 14 pound rocket hurtling into the sky at better than Mach 1.6 as evidenced by the awesome sonic boom it left in its wake. The rocket flew to 18,313 feet and returned safely from its fabulous flight. Although RockSim had the flight pegged at 16,800 feet, the motor easily outperformed expectations. Indeed, after discussing its performance with the manufacturer, he admitted that he tends to underrate his motor's performance characteristics to ensure the consumer gets a bigger bang for the buck.

Recovery:
The forward closure is plugged on this motor so there is no delay time for this reload. You must use a timer or an altimeter to fire your ejection charges. Since this is a M motor, most people will use dual-deployment for recovery, particularly considering the awesome performance of this motor. I can vouch for the fact that if anything, the manufacturer has understated the performance of this reload and you'll need a large recovery field or a very heavy rocket to keep the rocket close to the launch pad.

After recovery, wait for the motor to cool down before you disassemble it. Remove both internal snap rings then remove the forward closure. Once that's done, put on some latex gloves to keep your hands clean and use a long rod or stick to carefully push the nozzle up through the casing until you can grasp the liner and twist it carefully out of the casing. Once the casing is clear of the liner and the nozzle, use white vinegar to clean the exhaust off of all your metal parts and to clean the interior of the motor casing.

Flight Rating: 5 out of 5

Summary:
The AMW M2500 Green Gorilla is a wonderful 3-inch motor that performs as well as a lot of the best research motors out there. However, it isn't cheap, and if you fly a lot of M or N motors, you may decide that the prohibitive cost forces you to choose to make your own reloads. However, for anyone looking for a motor to achieve their Level 3 certification or for those who only fly M motors once or twice a year, this reload is an excellent choice for anyone who wants to go high or fly a big, heavy rocket on top of a really cool green flame.

PROs:

• It's the most powerful 3-inch commercial motor you can buy.
• It has a fantastic green flame for an exhaust.
• It has straightforward construction of the reload.
• Its performance exceeds its specifications.

CONs:

• The motor hardware and reload are expensive (MSRP is $375 for the motor hardware and $400 for the reload).
• It takes about a half an hour each to assemble the motor and to clean up after use.

Overall Rating: 4 out of 5