Red-Rx7
Senior Heliman
Location: Olathe, KS - USA
| Lots of updates....
Update #1
I recieved the new main shaft on April 2nd, after giving them the specifications and a 3' O-1 Oil Drill Rod. Here is how it came out:
Side-By-Side shot:
Hole Placement:
A few of the notable changes were the 4mm head Jesus bolt (was 3mm), and the additional length. One other thing you might notice with the hole placement picture, I didn't quite measure correctly the gear hole placement. I quickly measured 1.25" between the center of each hole, but in reality, it is something more like 1.215". It is off a tad, but doesn't cause a problem when installed.
On attempt of inital installment, I found that it didn't fit into the bearings. The shaft was a perfect 10mm, and the bearings measured out at some 9.97mm. I ended up putting the shaft in my drill press and used 180 + 320 grit sand paper to get it down to 9.97mm. Which, it then dropped right in.
Update #2
I set the initial electronics into the frame. As you can see, I am running JR 8717 servos for Aileron, Elevator, and Pitch; with HiTec 425BB for throttle and the CarbSmart.
The JR 8717 servos are quite hefty, and it took some squeezing to get them to fit into the frame.
Elevator
Aileron
Aileron & Pitch from the top
Update #3
I completed the CarbSmart sensor and servo installation. I used Arctic Silver Thermal Adhesive to secure the sensor on the OS 50 Hyper head. As per CarbSmart instructions, I placed the sensor on the fins with the closest to the cylinder wall.
Adhesive
Epoxy
Head Bolts still have access
Servo and Linkage
Update #4
After getting the servos installed and the linkage at a good 90o mechanical angle, I moved onto securing the head to the shaft. This step I wanted to get the phasing and linkages all completed. I had many questions going into this step, and ended up going down the wrong path at first.
I went at this with the old-school mentality of getting everything dialed in mechanically first, then applying electronics on top of it. Well, if I would have simply looked at the documentation of the HeliCommand unit, I could have saved a few hours! In speaking with Butch (bwellmaker), he simply asked if I was running electronics and why I wasn't letting the electronics phase the head.
So, if I ever go backwards in technology, I sure know how to use my JR 9303 Swash Mixing and mechanical throw setup now. :laugh: The first thing out of the HeliCommand manual states:
| Quote |
| All the mixer functions for elevator, aileron and tail rotor must be disabled: always set single-servo (H1) mode, as the HeliCommand is designed to use its own internal mixer exclusively.
|
Which resulted in me resetting the radio once again.
ANYHOW...
I went through all of the setup procedures with the HeliCommand and think I have it close to being "phased". Within the HeliCommand, I can adjust the travel of the servo collection. I adjusted these to get the following figures:
- I am able to put the main tracking blade over the tail boom, apply Elevator, and it does not move at all.
- I am able to put the main tracking blade 90o from the tail boom and apply Aileron, and it does not move at all.
- 50% collective stick, the blades reside at 4o pitch.
- I set the pitch curve to be 73% on the 100% collective point, giving me +9o pitch
- Leaving the 0% collective stick point of the pitch curve alone, I have -4o pitch
- When applying full Aileron at 50% collective, I am achieving + / - 7o of pitch from the initial +4o (becomes +11o / - 3o).
- When applying full Elevator at 50% collective, I am achieving + 5o / - 7o of pitch from the initial +4o (becomes +9 / - 3)
To make the Century Follower work, I had to relocate the the swash ball to an empty position on the other side. Else, it would have binded against the links. I actually got pretty frustrated and was thinking about how I was going to leave a nasty message with Century for Monday. Yet, I noticed there was another hole on the other side of the swash, which the follower sits between the linkage just fine there.
Full Collective, no Aileron/Elevator
Full Collective, Full Aileron/Elevator
Swash Picture
Moved Follower
I am still working out some final details with the phasing and pitch throws.
Update #5
After running all of the mathmatical calculations and research that I could, I have selected a brushed motor and gearbox for the on-board starter unit.
A great guy by the name of Mike (mjws) took some measurements for me with a Dynatron starter spinning an OS 50 Hyper motor. The starter was spinning at 4000 RPMs under load, drawing 21 AMPs, running at 11.1 volts. This measurement was the averaged values after a few seconds of running. Based on those figures, I did some reverse calculations:
Input Watts: 233.1 (21 amps X 11.1 volts = 233.1 watts)
Output Watts: 209.8 (90% efficiency X 233.1 input watts)
Torque Required to spin the motor: 70.59 oz-in
(Watt = Torque (Nm) X RPM (Radians per Second)
(209.8 = ??? (Nm) X 4000 RPM (.10472 radians X 4000 = radians per sec))
(209.8 = ??? (Nm) X 418.88)
(Torque = 209.8 / 418.88)
(Torque = 0.49847211611917494270435446906035 Nm)
(Torque = 70.59 oz-in)
In addition, I have found that the Torque specifications for the Hobbico TorqMaster 90 is 3100 RPMs under load, at 310 oz-inch stall.
Using these data points, I plan on using the following:
540 Size Johnson Motor:
Speed : 16,000 rpm @ 12V
Angular velocity constant: 1560 rpm/V
Amps @ nominal: 1.2 Amps
Efficiency: 71.4%
Peak Power: 0.36 hp
Stall current: 91.8 A
Stall torque: 78.7 oz-in
Weight: 7.50 oz (213 grams)
RC4WD 4:1 Gearbox:
Overall diameter: 36mm
Legth: 18mm (.7 inch)
Output shaft diameter: 3.17mm (with a flat surface for mounting standard RC pinion gears)
Total metal gears: 6
Total Parts: 11
Based on the motor charts, I am calculating the following:
Based on the charts:
Maximum Power (RPM crossing Torque)
4:1 Gearbox
50% Efficiency
951.56 mN-m // 134.67 oz-in
2475 RPM
~35 Amps
Getting closer to Stall:
4:1 Gearbox
25% Efficiency
1400 mN-m // 198.25 oz-in
1250 RPM
~50 Amps
At this point in time, my plan is to use a timing pully and a timing belt to spin the one-way clutch based starter shaft. I have complete horizontal access to the starter shaft, and figure this would give me most flexibility for adjustment.
One thing I intend on doing is keeping the starter hex coupling, in the event that the starter doesn't turn the engine over (dead battery or whatever). To do this, I think I am going to have to machine a new starter shaft to lengthen the upper-most part of the shaft to allow a pulley and hex coupler to attach to the shaft. Currently, I don't think there is enough room for both.
Anyhow, thats all the updates I have right now. My fingers are tired.
Mike |
Thanks for the vote of confidence!
