Wednesday, October 17, 2018

Experiments with STRIX Free Flight Electric Motor Timer

In the past few weeks I have been experimenting with using a small electric motor timer that I purchased from the RMRC company for under $7. An online friend had sent me a link to this and I ordered a couple of the timers. After receiving the timer I discovered it used the larger JST 2.0 plug in connecting to the battery, so another order was placed for a couple of batteries and a charger that fits this connector. The connector is slightly larger than the connector used on the Eflite planes I have.  In the future I want to replace the connector on the timer with the more standard connector on a sample timer. This would make it possible to use batteries and chargers that many people already have.

Electric Powered Guillow's Cloud Buster

STRIX Timer, motor, and battery
My first test aircraft was an injected foam glider the Guillow’s Skyraider, the motor was mounted on a pylon I constructed out of balsa, everything held together with low temperature hot glue.  The total weight was 56 grams which is too heavy for much of a climb. For a propeller I used one from an Aero Ace biplane I had, it did not overheat the motor like when trying an E20 size propeller. The specifications of the timer call for 6 mm or 7 mm motor, I used 7 mm motors from RMRC which come for in packages of four motors, two wired for clockwise and two counter-clockwise. 

Robbed the Propellers

Comparison of Plug Sizes

Charging Board and AC Power Supply, can use Lipo Battery 3S or 4S

The foam glider might be great if it were lighter, the first flights it only got maybe 20 feet high. I removed some foam from the glider and it started climbing higher. The stability was just okay, it tended to wander around in the sky but it always survived a hard landing.

Electric Foam Glider

For the next plane I wanted to try a balsa plane with a really simple structure, I found a Super Dart in my basement which is similar to Sig Thermal Dart, flat pointy wings. A real short test fight with timer a battery taped on showed that this will climb better with a total weight of 23 grams. The weather has turned windy all the time which is bad for test flying. After another flight in the wind the second flight resulted in the fuselage breaking in multiple places. In the future would like to try this with a basswood fuselage as I would like to find really simple planes for the electric setup.

Super Dart Crash Damage

As I see this timer/motor setup, it would be good for kids flying in a schoolyard, the maximum run is only 10 seconds. You can select between 5,8, or 10 seconds very easily. With the battery that I found to fit the connector  at 220 mah it will give many flights on a single charge. The battery is rather heavy at 6 grams, timer 3 grams, and motor at 3 grams. The increased weight over a rubber motor would explain why crashes on models designed for rubber power would be more damaging. 

Cloud Buster Electric

The last model I have tried was a Guillow’s Cloud Buster built a long time ago. I think this model will work well but again I tried to fly it in way too much wind. First short flight it went too much right but recovered. I added too much weight on left wingtip to correct on second flight and it hit the ground in a left spiral dive breaking the pylon. I started building a new pylon that I can mount the timer and battery inside and have the wing held on by rubber bands. This type of model I have to believe should climb high enough to glide around for an additional 30 seconds or more. Kids do not even have to wind the rubber which should not be a big deal but I find some have trouble. I am looking for other sources of motors and propellers at an inexpensive price. I will write another article as I progress with this farther.

Crash in Progress

Rebuilding Pylon
Update 10/18/2018

It was relatively calm this morning as the sun was coming up but there was frost in the grass. I was determined to get in more test flights on the Cloud Buster I rebuilt the pylon for with the wing now held by a rubber band before work.  First flight at 5 seconds looked alright so went to 8 seconds. The plane had too much right turn, adding clay to wingtip had it going straight with a series of small stalls, taking a small amount off it was better but it seemed to easily circle either direction.  The plane climbs but not very steep, I think more wing area might help. Someone suggested the AMA Maxi Jr might work which I have and will probably try, it has a constant chord wing. The Cloud Buster tapers to thin at the tips.  If I used a lighter battery I think that would help too.

Cloud Buster with New Pylon

12/11/2018 - Sig Cub Electric

Bill Kuhl

Related Links  Link to Timer  
Foam Guillow's Glider   Guillow’s Cloud Buster

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