Monday, January 24, 2011

Mega Review: Motors

Here are my motor reviews from EMRR.

AeroTech G77R (updated!)
AeroTech G79W (updated!)
Quest D5-0 Plugged
Ellis Mountain SU J110 (out-of-production)
Ellis Mountain SU J228 (out-of-production)

AeroTech G77R

This is a brief review of Aerotech’s G77 Redline reload kit for the 29/120 case.

The reload kit contains the typical components: Nozzle, liner, two propellant grains, forward and aft O-rings, forward and aft fiber insulators, ejection charge adhesive disk, FirstFire igniter, ejection charge container/cap, delay element, delay insulator, delay O-ring, delay spacer, and forward delay washer.

The assembly is straightforward and typical RMS, so I won't go into any detail. You can view the full instructions by going to the Aerotech web site, selecting 'Resources', then 'Instructions', and scrolling down to the 29/120-180R instructions. You will need to lube the O-rings and it will of course require the 29/120 hardware.

Here are the salient specifications:

Total impulse 105 N-sec
Burn time (calculated) 1.36 sec
Propellant type Redline
Delays 6 and 10 sec**
Propellant weight 55.4g
Loaded weight (including case) 155g
Length (with case) 5.9 inches
Retail (as of 5/7/05) $13.95

** - Can be modified for other delays. See document on Aerotech site under Resources/Instructions/Reload Delay Kit (RDK) and Delay Modification Instructions/RMS Delay Modification Instructions.

The down side to this motor is that is had a bit less total impulse than the G79 or a G80. However, it has one distinguishing feature--that bright red flame! My thanks to Randy from TRF, aka 'Rocketmaniac', for the launch photo!

When I bought the 29/120 case, AeroTech was claiming that the Redline propellant couldn't be used in the 29/40-120 Hobbyline case.  IIRC they stated that the red flame wouldn't be as visible and there may have been pressure issues (the Hobbyline case is thinner walled and has fewer threads on the closures).  So, I bit.  I can't  say that I wasn't very, very happy with the G77R.  I was and I flew a bunch.

However, AeroTech since released the G71R.  This motor had more average impulse and a lower price point.  I then felt like I had been tricked since I basically stopped using my 29/120 cases.  At least the closures can be used on the 29/180 (an others).

About a year ago, production of the G71 was stopped because of delay issues.  I haven't experienced any but I still have a couple, so it's not too late.  I guess you once again need the 29/120 if you want a 29mm Redline.  Unless you buy the higher priced single use or Loadable Motor System (LMS) version.  I personally will probably just go for the H148R or 38mm G67R for my red fix.

AeroTech G79W

This is a description of Aerotech’s G79W, including the 29/120 RMS case.

Although this product was introduced at LDRS 23 in July 2004, my casing (S/N 037) has a manufacturing date of 1/8/02. This product was obviously in the works for a while. The case is new and is not interchangeable with the 29/40-120, but the closures are the same as those used with the 29mm high power cases.

The reload kit is a typical AT reload so I won't go into the details--liners, insulators, O-rings, two slugs, etc. Here is a comparison between the G79 and the G80:
G79 ¹ G80 ²
Total Impulse (N-sec) 115 120
Burn Time (sec) 1.5 1.5
Propellant Weight (g) 58.6 57.4
Propellant Type White Lightning Blue Thunder
Delays (sec) 6, 10, 14 4, 7, 10
Igniter First Fire Copperhead
Loaded Weight (g) 158 120
Length (in) 5.9 4.88
Retail (as of 07/20/04) $11.95 $18.95
Notes: ¹ per AT
           ² per NAR

The main trade-offs include:
* You have to build the motor instead of just slapping the single use G80 in.
* Loaded motor is slightly heavier and just a hair less oomph than the G80.
* Longer than the G80, which is a problem if you used a (evil) motor block.
* The longer delays may or may not be beneficial to you. I'd rather have a -4 than a -14. (I overbuild, what can I say?)
* Much better igniter with the reload. I'll be dipping fewer igniters than before.
* The reloads are much cheaper. I hear the G80s are headed up in price again.

I have flown this motor several times. It generates lots of white smoke like my beloved G80FWLs. I have two observations:

1. The delay components all fit together easily, whereas on the 38mm RMS it takes some effort (very little, but some) to get it together. A good example is the delay spacer--this one fell right in. On the 38mm RMS I have to work them in.
2. The threads of the forward closure were the dirtiest I've ever seen in an RMS (post flight, of course). Also, there was lots of gunk between the liner and the case on the forward end. The aft end was not unusually dirty.

Although the price of this motor compares favorably with the SU 'G' motors, it doesn't compare well with the Hobby-Line/29-40-120 motors. I like the G64 just as well and it can be purchased for under $10 from discount suppliers. The G64 also provided a little more total impulse (118.8Ns).

Quest D5-0P

This motor is a 20mm, long burn, plugged D that is suitable for rocket gliders, saucers, monocopter, and light conventional rockets. You may see its designation listed as D-0P. The motors packaging is marked -0 even though they are plugged. I guess something was lost in translation. These were reportedly mainly produced for FAI competiton. D5-4 and D5-6's are now also available.

Because it is a non-standard diameter, you'll either have to adapt to 24mm tubing or roll your own. Quest should be releasing kits soon, Semroc has promised 20mm tubing, and Art Applewhite has a 24mm adapter, and is working on some kits.  These motors are packets one per pack and come with two Q2/G2 igniters.

Here are the details:

* MSRP $5.00
* A great RC glider motor. 4 seconds of gentle burn time. Clay plug with no delay or ejection.
* Total Impulse: 20 Ns
* Max Thrust: 11.5 N
* Avg Thrust: 4.93 N
* Burn Time: 4 seconds
* Initial weight: 38g
* Diameter: 20mm
* Length: 88mm
* Propellant: Black Powder

As I mentioned above, this motor comes with two "Q2/G2" igniters. These are really nice. They have flexible, insulated leads and nice blob of pyrogen. Shortly after their release, Quest received reports that the continuity check on some 12V launch systems would fire them, so they issued an alert to test your launch system, pointing out two igniters were provided with each motor.

I flew numerous D5s at NARAM and used the spare igniters on other rockets. There was no premature ignition and they worked fine. BTW, the long flexible leads make clustering really easy!  I flew them in Art Applewhite prototype Helix monocopters and Qubits.  These motors have thin walls which, combined with their long burn, caused severe burn-throughs in the Helices and even in the Stealth Qubit!  The long burn was generally pretty cool, the the spinning Qubits arced badly and sometime were headed down under power.  As a result, these kits were never produced.

Ellis Mountain SU J110 (out-of-production)

The Ellis J110-P a 54mm single use motor that provides 751 N-s total impulse (~17% J) with a burn time of 6.8 seconds (Tripoli Motor Testing’s numbers, the photo shows the EM numbers).

This motor is only about 9.5" long, including the plugged aluminum closure. It has a medusa nozzle, but only the center port is drilled. It does not come with an igniter.

I flew this motor in a beta version of an 18" saucer and lit it with a large Magnelite igniter. This did the trick, but the motor took a long time to finally come up to pressure and get going. It provided a nice long burn, but because of low average thrust and a regressive profile, the saucer arced over and was still under power after apogee. It then aerobraked down and continued to spew large amounts of smoke, causing the LCO some concern. It landed in a outcrop of brush that was damp so there was no risk of fire.

Ellis Mountain SU J228 (out-of-production)

The Ellis Mountain J228 38mm single use motor provided a total impulse of 1104 N-S (72% J), giving a burn-time of 4.8 seconds. It was about 22 inches long including the turned-aluminum forward closure.

I flew the motor in a beta test 18" saucer and it gave some ride. No igniter was provided so I supplied a large Magnelite home dipped igniter, installed about half way into the core. Ignition started with some flame spewing out of the nozzle then the motor immediately roared to life. I wouldn't consider it hard to light or all that slow to pressurize. That Magnelite is good stuff. It sputtered a bit at burn out. Way cool flight!

PROs: Long burn, fire, smoke, and noise.
CONs: Cost ($75)