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Old Feb 08, 2006, 09:56 PM
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Park Jet Guru
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Seattle, WA
Joined Jun 2002
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Little Screamers Park Jet Special Motor

Bob at Little Screamers was kind enough to give me one of his new Park Jet Special motors to test last week, so I thought I’d post a quick review here. The Park Jet Special is a special wind (8 turns) of the Little Screamer (LS) outrunner motor, and is specifically intended to provide high speeds on park jet-type models.

To test it, I put the motor in my T-38 park jet, replacing my favorite Himax 2015-4100/4.4 gearing/9x6 prop setup (see pics below). Since the LS motor came with a standard 3/8” stick mount it was a quick drop-in replacement. Flight testing left me VERY impressed with the LS motor --the performance meets or beats the Himax setup in just about every measure. Here’s the synopsis:

* Thrust/Speed – This motor was designed for speed, and it didn’t disappoint. Bob recommended an APC 6x5.5 prop, and in level flight speed runs with that prop I’d estimate my T-38 was doing around 70 mph! MUCH better than the 50 mph top speed of the Himax setup. Thrust/weight with this prop was slightly under 1:1, though, at 15.5 oz AUW. The model could easily climb out of sight after a high speed run (due to inertia), but at slower speeds it couldn’t sustain a vertical line. There was still plenty of thrust available for maneuvering, though. To see if I could trade a little of that top speed for more low speed thrust, I then tested an APC 7x4 prop. The results were much to my liking. Top speed dropped to about 60 mph (still faster than the Himax) and thrust/weight was well over 1:1, with unlimited vertical performance (similar to the Himax). For my kind of flying style (lots of aerobatics) the 7x4 was the better prop, but it’s nice to know the model can be quickly converted into a speed demon with the smaller prop! However, note the test bed here was my 100% T-38 park jet—which is a really large and draggy model for this little motor. Because of the very low weight and high power of the LS motor, I think you could scale the T-38 down to perhaps 75% and get significantly higher speeds while still maintaining very good low speed performance. Bob claims speeds close to 100 mph with this motor on smaller lower-drag airframes, and I believe it.

* Current draw – I put the motor on the Wattmeter with both props and a fresh TP 1320 11.1V Pro-lite pack. The results were (static wide open throttle):

APC 6x5.5: 14.0 amps, 140 Watts
APC 7x4: 15.3 amps, 150 Watts

These amp draws are similar to the geared Himax setup, and are easily within the capability of a TP 1320 pack (which is nice since it keeps the weight of the model down). Bob said not to exceed 18 amps with this motor, and I found that both props stayed well below that limit.

* Weight – In my opinion, this is one of the best things about this motor. The RTF weight with mount, connectors, and prop is only 1.5 oz. That’s HALF the weight of the geared Himax setup, even though the LS motor has BETTER performance! The AUW on my T-38 dropped from 17.0 oz to 15.5 oz, a very nice decrease. But while the weight savings itself is nice, it’s even more important for a park jet since it makes the model much easier to balance. Although my T-38 didn’t require ballast to start with, I had to move the battery aft about 8” to restore balance, from the very front of the fuselage to under the aft canopy. For all of you that are flying with ballast in the nose, simply switching to an LS motor may allow you to save 1.5 oz of motor weight PLUS the weight of the ballast! Another thought that occurred to me is that the LS motor would make an ideal motor for an F-14 Park Jet with twin motors. Two LS motors would provide TWICE the thrust of a single Himax yet weigh the same. Plus, the small 6” or 7” diameter props could easily clear each other.

* Prop diameter – Because the LS motor swings a little 6” or 7” diameter prop, I found that prop torque effects were MUCH less noticeable than with the 9” prop on the Himax. This was especially so at launch, but also noticeable during aerobatics. Plus, the smaller diameter prop is safer to hand launch (more clearance from your hand) and may even be less likely to be damaged at landing (since it doesn’t stick out as much). At first I was worried about the efficiency of a small diameter prop at the back end of a long and blunt fuselage, but I was glad to see this wasn’t a problem on the T-38. Whether it would be a problem on park jets with wider aft ends (like the F-18 or F-15) I’m not sure, but I have a hunch they’ll work fine as well. The larger 7” prop will help this.

BOTTOM LINE – Compared to the previous Himax 2015-4100 setup, the LS Park Jet Special motor provides 10-20 mph higher top speed, similar low speed thrust (with 7x4 prop), similar current draw, significantly lower weight (especially if the model needs ballast with heavier motors), and lower cost ($50 for the LS versus $67 for the Himax). I also found the build quality of the LS motor to be excellent, and it comes with both a stick mount and a firewall mount. Thus, I highly recommend this motor! They aren’t listed for sale yet on the Little Screamers web site, but Bob said you can send him an email to order one.

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Last edited by jetset44; Feb 08, 2006 at 10:02 PM.
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