Loki Research - 38mm Reload System {Motor}

Contributed by Douglas Gardei

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Manufacturer: Loki Research
Loki Research 38mm high power rocket motors

Loki's line of 38mm reloadable motors. Cheapest of the 38mm reloadable options for both hardware and reloads. Currently, only the H144, I405, and J528 loads (Loki White propellant) are available for these motors, but more formulas and motor designations are coming out soon.

Currently available is the Loki 240, 480, and 740 motor. Each motor comes with a quality case with external snap ring (thrust ring), graphite nozzle, nozzle washer, forward bulkhead, and snap rings. If you buy the system package, you will get a forward closure for each motor. You don't have to share the closure.

A typical Loki reload comes with a spiral wound phenolic liner, propellant grains, delay grain, two large O-rings, six small O-rings, and a red cap (or vial) that contains 1.5 grams of black powder.

An interesting thing about the Loki reloads is the number of grains in the reload kit. The H144 uses 4 ~30 gram slugs, and the I405 (naturally) uses 8 ~30 gram slugs. The J528 breaks the trend, using six ~60 gram slugs. Loki's goal was to create loads that can be shipped parcel post, so they made the grains 30 grams. However, interesting things happened when the motors got too large using the smaller slugs, so this was not an option with the 740 motor.

Loki Research 38mm high power rocket motors Assembling the Loki motor is very similar to Kosdon and AMW motors. This is the order that I build them. I start out by greasing the two large O-rings and placing them in the slot in the nozzle and bulkhead. Of course it is important to make sure you use the correct nozzle for the load you are using. The nozzle conveniently has a number scratched into the side that corresponds to the reload instructions. Set the closures aside so they don't get dirty, damaged, or lost.

Then it is time to build the delay column. Simply stack the six smaller O-rings over the delay element then place it on a flat surface and press the forward bulkhead onto it so the delay grain goes into the delay well. I then use a blunt tool to push the O-rings in all the way.

Once this is done, you have the option of trimming the delay. It is a good idea to use the Loki-DAT tool for this. The Pro38 DAT tool would work also. Leaving the delay grain untrimmed will yield a 17 second delay. The DAT tool will allow you to trim it to 13, 10, 8, or 5 seconds.

Insert the forward part of the nozzle into the liner. Then stack in the propellant grains followed by the rear end of the forward closure. Grease up the inside of the case, and the liner tube. This will make the next step easier, and you will be thankful for the grease when it comes time to remove the spent components, trust me. Press the assembly into the motor case (nozzle should be at the end with the thrust ring) until the nozzle is about a quarter inch from the snap ring slot. Insert the nozzle washer, followed by the snap ring. Make sure the snap ring is in the groove by lightly squeezing the pliers and rotating the motor.

Turn the motor over and press down on the forward closure to press the nozzle and washer onto the snap ring. Install the final snap ring, making sure the snap ring is in the groove. Finish the motor construction by installing the ejection charge (if you want to use it). The forward closure gives you generous space for the ejection charge, so pour in as much as you need. Then take some wadding and place it on top of the charge. Then press on the red cap to hold everything in place. The wadding is there to hold the powder against the delay column.

Construction Rating: 4 out of 5

Loki in PML

To ignite the motor, I used a Magnelite igniter with a single fold. Ignition is quick and the motor produces a bright white flame and tons of white smoke. Of the two motors I flown, the I405 was my favorite! I had the pleasure to see several I405 flights, and it has a loud and unique sound to it! After a launch of a Big Brute with one, Carl Tulanko asked me, "What was that?" I told him a Loki I405. Later on during the day, I had my PML Aurora loaded with one and asked if he wanted to come to the flight line and watch it fly. He said "No way! That motor is scary." It's a very impressive motor. I only got to see one J528 flight up close. If you like the J350 and the J570, then you would love this motor! Lots of umph!

Enjoy a video by clicking HERE

Cleaning of the Loki motor is identical to that of the AMW and Kosdon motors. Remove the snap rings, and press on the bulkhead to press the components out of the case. Suggested tool to use is a wooden dowel to push out the closure (or nozzle, if you to use the other end). If you are fortunate (and remembered to generously grease the liner), everything should come out with minor effort. However, if the rocket had an impact of any kind, one of the bulkheads would mash itself into the liner, making removal a chore. I used Baby wipes to clean mine, which worked surprisingly well.

Flight Rating: 4 out of 5

I am really pleased with the Loki 38mm product. I mentioned that it is cheaper than other brands. Let's compare with this simple chart. Prices are retail list and comparison is done with Aerotech White Lightning, Pro38 standard, and Loki loads.

AeroTech Pro38** Loki
240 motor $92.95 $32.95 $49.99
240 reload $19.99 $30.75 $19.99
480 motor $106.95 $49.15 $59.99
480 reload $35.95 $43.95 $29.99
720+ motor $116.95 $57.15 $69.99
720+ reload $47.95 $57.15 $39.99

** - Pro38 motor hardware is just a tube. There is no closures. In a sense, Pro38 motors are disposable motors that are held together by the case.

Another interesting comparison is the total impulse of the loads for the cases and how much they cost to fly per total impulse. This comparison based off data from the NAR/TRA/CAR combined list. All numbers have been rounded to nearest whole cent.

Motor Total Impulse
Cost per Ns
Aerotech H123 236 8 cents
Loki H144 239 8 cents
Pro38 H153 258 12 cents
Aerotech I211 435 8 cents
Loki I405 493 6 cents
Pro38 I285 510 9 cents
AeroTech J350 697 7 cents
Loki J528 741 5 cents
Pro38 J330 694 8 cents

In the near future, Loki will be offering new loads for their motors. If you like fast burning, "kick 'em in the butt" loads, then you will enjoy their Blue Formula which will debut with a H294, I605, and my soon to be favorite, J1001! Also in the works are two moon burning loads that utilize their White formula. I can't wait to try out their I124 and J192 loads! Those loads have close to a 4 second burn!

What I would like to see in Loki's 38mm line is a 360 and 600 motor. I can imagine a 360 load priced at around $24.99 and a 600 load being a reasonable $34.99. I would also love to see Black and Spark loads introduced too. I would have the problem deciding which loads to buy!

Overall Rating: 4 out of 5


J.P.C. (July 17, 2005)
I have one word to describe Loki's J528... Awesome! I have flown this motor twice and both times I was amazed at how fast it lifted an 8 1/2 lb. rocket to 2800+ feet. Beautiful white smoke and nice long flame. Jeff Taylor has a winner here.
J.M. (December 13, 2005)
Simply put, the Loki I405 has the look, feel and sound of a AT J350W (one of my favorites). Just a little shorter burn. What does this mean? Very loud, huge 4' flame, lots of smoke. Great motor at a reasonable price with no HAZMAT fees as well. An awesome level 1 motor.
L.A. (April 24, 2006)
Important note for anyone who wants to use the I110 reload in the 38/480 case: You MUST have the #16 nozzle (which is the same nozzle as what is used with the 38/240 casing) when using this long burning, single grain reload. This information is clear in the I110 reload instructions but isn't well documented on the Loki website. With the right nozzle though, the I110 is as impressive as any other Loki motor!
R.J.K. (October 30, 2006)
I have flown the H144 four times so far and have great results. The rocket weighs 3.5 pounds and has an estimated altitude of 2100'. All flights have been nominal and I got my level 1 cert with this engine and rocket. I had one bad experience with the J528. On my first flight with it in a PM Black Brant X it literally blew up, blowing the casing apart at the aft snap ring groove. The rocket fortunately went up about 50' and the engine went through it which deployed the chute. The engine mount changing adapter was destroyed but for the most part the rocket survived. Jeff at Loki was very interested and also supplied me with a new motor and reload under warranty. I had to wait 8 months but flew the Black Brant and J528 to my level 2 cert at the Freedom launch in September 06. Beautiful flight to 3200' and recovery 20' from launch control. I also have his I series in the 110 and 405 configurations and hope to fly them soon. Unfortunately getting Loki stuff down here in Florida is difficult as the local supplier closed up.

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