With Spring-like weather hitting this neck of the woods, my thoughts are shifting from building, to flying. Not to mention, I am also excited about the approaching mountain biking race season. I guess that's the closest I get to "flying" around the woods. With that said, I will probably start to have some posts that may cover either subject.
I ran another motor test on the 36mm motor. I wanted to re-evaluate the perfomance of the 5S battery with a 8x6 prop. This was a quick test, because as soon as the throttle was increase beyond ~75%, the motor was pulling 100 A, and the ESC cut power. I definitely want to look at a 7" prop with the same setup. Should be a possible solution for the Stryker.
On Saturday I went riding with Josh, Andy, and Dan Knudsvig. Fun ride, but I couldn't keep up with the group. I guess I have some work to do... We went for a good 26 miles through, and around, beautiful Afton. I hope to get over there a few more times before the first race in May. A lot of big hills for training.
Monday, March 22, 2010
Tuesday, March 16, 2010
Control Surfaces
I picked up a DU-BRO hinge pocket cutter for $10. I started using it last night, and was very happy with the results. It has a self-centering fixture that aligns the cutter blade. I should have all the hinge grooves cut out tonight.
Tomorrow, the airframe wil be ready for paint. I wanted to allow the water-based PU to cure before covering with lacquer. I am afraid that if there is any water in the PU, it will make the spray paint bubble. Maybe I will hold-off until this weekend...
Tomorrow, the airframe wil be ready for paint. I wanted to allow the water-based PU to cure before covering with lacquer. I am afraid that if there is any water in the PU, it will make the spray paint bubble. Maybe I will hold-off until this weekend...
Sunday, March 14, 2010
On more thing...
I was playing around with the flex of the Stryker airframe yesterday, and wasn't really happy with the rigidity of the single layer of 3/4 ounce fiberglass over foam. Since I was in the process of cutting out the elevons (balsa) and glassing them, I thought I would add another sheet of glass to the underside of the airframe. It is going to add a little weight, but after playing with the final product this morning, I am very happy with the results. The airframe is very rigid now, and will be able to handle those high G turns expected.
The only thing I am re-evaluating is the motor selection. With the added weight, it might be nice to have a motor that can produce more torque (i.e. 36 mm). I guess I will have to get this thing in the air to final make that decision...
The only thing I am re-evaluating is the motor selection. With the added weight, it might be nice to have a motor that can produce more torque (i.e. 36 mm). I guess I will have to get this thing in the air to final make that decision...
Friday, March 12, 2010
Motor Testing
After quite a bit of messing around, I finally came up with a solution for testing the two motors for the super-Stryker. I actually had to do some machining to make the Custom RC Parts mounts to fit the Turnigy motors. I was then able to bolt the two mounts to a ¾” piece of pine I use as a hobby cutting board. With the motors securely attached to board, I could run through the different setups I wanted to test.
First off, the motors I tested:
• Turnigy 2836 – 3200kV outrunner with shaft mount
• Turnigy 3648 – 1450kV outrunner with shaft mount
The ESC I decided to run is a Castle Creations ICE 100 amps BESC. I also picked up an 85 amps Turnigy as backup. After some initial range finding, I determined that only 2 batteries were able to deliver the amount of power needed to break the 100MPH mark. The two batteries tested were:
• 5 cell, 2200 mAh, 40C (85 amps continuous)
• 4 cell, 2650 mAh, 40C (106 amps continuous)
The test consisted of running the motor at WOT for ~20 seconds. During the run, Vmax, Imax, and Watts were recorded using a Turnigy watt meter. The results are as follows:
Prop / Motor / Batt Vmax / RPM Imax Watts Prop Speed (RPM*pitch in.*.00095)
8x4 / 36mm / 5S 16.2 / 23490 87 1428 89 MPH
8x6 / 36mm / 5S 16.5 / 23925 83 (70% WOT) 1373 136 MPH
8x6 / 36mm / 4S 13.1 / 18995 86 1163 108 MPH
4.75x4.75 / 28mm/4S 13.5 / 43200 72 1008 195 MPH
4.1x4.1 / 28mm / 5S 17 / 54400 66 1150 212 MPH
4.75x4.75 / 28mm / 5S 16.6 / 53120 97 1647 239 MPH
This is merely a sampling of the best runs, and I may look into trying a 7” prop on the 36mm motor. Let’s just say, I am not going to publicize my final choice until race day. I want to keep some of the suspense for my competitor.
On a side note, the Turnigy 28mm motor is one tuff cookie. It got pretty hot with that 97 amp run, but never blew a coil or smoked itself. That might be an inkle to where I am headed with the build…
First off, the motors I tested:
• Turnigy 2836 – 3200kV outrunner with shaft mount
• Turnigy 3648 – 1450kV outrunner with shaft mount
The ESC I decided to run is a Castle Creations ICE 100 amps BESC. I also picked up an 85 amps Turnigy as backup. After some initial range finding, I determined that only 2 batteries were able to deliver the amount of power needed to break the 100MPH mark. The two batteries tested were:
• 5 cell, 2200 mAh, 40C (85 amps continuous)
• 4 cell, 2650 mAh, 40C (106 amps continuous)
The test consisted of running the motor at WOT for ~20 seconds. During the run, Vmax, Imax, and Watts were recorded using a Turnigy watt meter. The results are as follows:
Prop / Motor / Batt Vmax / RPM Imax Watts Prop Speed (RPM*pitch in.*.00095)
8x4 / 36mm / 5S 16.2 / 23490 87 1428 89 MPH
8x6 / 36mm / 5S 16.5 / 23925 83 (70% WOT) 1373 136 MPH
8x6 / 36mm / 4S 13.1 / 18995 86 1163 108 MPH
4.75x4.75 / 28mm/4S 13.5 / 43200 72 1008 195 MPH
4.1x4.1 / 28mm / 5S 17 / 54400 66 1150 212 MPH
4.75x4.75 / 28mm / 5S 16.6 / 53120 97 1647 239 MPH
This is merely a sampling of the best runs, and I may look into trying a 7” prop on the 36mm motor. Let’s just say, I am not going to publicize my final choice until race day. I want to keep some of the suspense for my competitor.
On a side note, the Turnigy 28mm motor is one tuff cookie. It got pretty hot with that 97 amp run, but never blew a coil or smoked itself. That might be an inkle to where I am headed with the build…
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