The Elebee Project Phase II

The Goal

If you've read earlier posts that you may know that the goal of the elebee project was to make my elebee fly faster than a Parkzone Stryker C (which is an awesome plane - my ambition is based out of respect, not out of any sense of dispargement).

The Power Plant

Although some have expressed doubts about the ability of the elebee airframe to handle this speed I wasn't terribly worried. I thought the main problem was getting enough power at a reasonable price. To that end I settled on an align brushless engine and speedie.

So, the final parts for the Elebee Project (or at least I hoped they were the last parts) were an Align 430L Brushless Motor 2800kv (I think they use them for their T-Rex helicopters) and 35A Align speed controller. Kit came from nitrodude. All up damage - $133. That seems pretty cheap given the result I got, but more on that later.

The 430L is an outrunner in a can design (meaning the outer shell doesn't rotate), making it easier to mount, with similar dimensions to a 400 speed brushed. It can handle 23A continous and up to 260 watts. Because I am running a 4s I cannot push 23A through, as that would be about 340 watts.

I bought a 35A speedie because I wanted to make sure that I had enough headroom to abuse stuff a bit if necessary to reach the speed I needed to.

The motor was secured in the tail of the elebee using cable ties - exactly the same mounting method as the stock brushed 400 speed motor. Although I was somewhat concerned about the motor slipping the ties, when you think about it the motor will drive a small prop, and although it will have significant thrust, it wont be have a lot of torque, and the thrust will not be that much more than say the weight of the aircraft twice.


The previous motor managed to actually slightly melt the "canopy" (a brushed 380 that really wasn't up to the job - rest in piece). So, I went for the simple choice and used just a little bit of balsa to prop the engine up (I don't like making things more complicated than I need to).

Given I was planning to run the motor pretty hard (at least at the 260 watts previously mentioned) I was keen to give the engine (and speedie) as much help in cooling as possible.

To this end I bought a motor heat sink. However, to make good contact with the engine I had to trim it so it fit between the cable ties (so it is only about 2/3 as long). Also, to fit in the space in the canopy I had to trim the bottom fin of each side of the heat sink.






With this done I turned my attention to the canopy. I extended the V in front of the motor mount (to allow greater airflow) and also cut holes in the motor mount section to allow the canopy to fit over the heatsink.





Once this was done the canopy fitted over the heatsinks on the engine. The heatsink of the speedie was also positioned in the v slot so that it could benefit from the airflow.

The prop was fitted using a 3.17mm prop adaptor and is an APC 5x2.5.

With the prop fitted I busted out the clamp meter to check how many amps she was drawing. Initially I didn't want to exceed the engine's ratings so figured the maximum amp draw was about 17.3A (~260w/14.8v). I tuned the JR TX on the up throttle throw so that at top position it drew about 17A. This translated to limiting the up throttle throw to 50%. Needless to say I had someone (Paul from nitrodude) holding the model for me whilst I was configuring the throttle throw. A few moments of me tuning convinced me that this was going to be a weapon, and that it was too loud to hang around for long.

Like all home built world speed record kit, the canopy is of course secured with tape...


The Test Flight

At Curtin this morning DJ watched with a mixture of bemusement and interest as I did the awkward running throw to get "Santa's Little Helper" airborne. I got a nice wing level launch, and opened the throttle. She quickly began building speed as dog walkers and golf putters looked up to see what that high pitched rackets was.

Once she had speed she was just phenomenal - trully unlimited vertical - a lack of rudder means she will normally fall of straight up, but it seemed like when I put her on her tail from level flight she put on 100metres altitude in no time at all.

DJ's bemusement was gone. Two giggling little boys (DJ and yours trully) watched as the elebee screamed, figuratively, and literally, around the field. Surprisingly, despite the speed she felt so solid in the air, responding perfectly and quickly to instructions. I pulled a wide 25 metre diametre loop - no problems.

I didn't want to use too much of the battery as there was more flying to do at Lyneham, so I brought her in after just a few minutes. Given the change has been weight neutral she still glides exceptionally well with a nice long slow speed glide curve.

Even after a couple of minutes of stuffing around, mostly at full throttle she had only used 400mAh or so, so I knew that I would get decent flight time out of the 2200mAh battery.

The Race

So we headed of the Lyneham for the usual "club" get together for non-club park flyers. Fortunately not only did we have a Stryker C there, but also a custom Stryker with 400w of power.

After generating some interest with the first elebee flight at Lyneham we put all the deltas up at once.

Of course, at altitude it is really hard to tell what speed is, but urging the other pilots for WOT we got all the Delta's running in the same direction at once.

Here is the result...

The elebee ("Santa's little helper") is faster than a Stryker C in stock trim.
It's velocity was indistinguisable from the custom stryker.

Wow - I didn't think it would be quite that easy, given the Elebee's heavier airframe. We seem to have hit a sweet combo with the 5x2.5 prop although we will try some others later.

So..., would you like to see the video. There are three options - a .mov version (quicktime - about 800k), a small avi version (should play on anything - about 8MB) and a larger avi version (13MB). The video isn't great, being taken from my digital camera, but it should give you some idea of the sound and speed of this plane. I'm stoked - this has worked out so well.

.mov (800K)
Small .avi (8MB)
.avi (13MB)

Final Note on Heat

The cooling and working within the engine's limits seems to work quite well. Even after a couple of full throttle runs the engine was cool enough to hold within about 60 seconds of landing.