Electric Flite Streak Powertrain Testing

Hi again,

I've been doing some testing and "What-ifs" for the electric Flite Streak. Numbers seem to match within an acceptable margin of error the Ecalc values. Ecalc is an electric flight prediction program.

I'm using the following equipment:
Motor: Typhoon 2912/10
Battery: ThunderPower 2100 Prolite 15C
Speed Control: Castle Creations Phoenix 35
Astroflight Whattmeter
TNC tachometer

Prop RPM Amps Watts

Master 9-6 9880 16.5 184
APC 9-6 9780 17.6 195
APC 10-6 8800 22.5 235
APC 10-8 8110 28.4 285
APC 12-6E 7000 35 357 this is scary!
APC 10-7 slo fly: too much load, RPM too high for safety

I would like to try an 11-7 APC electric. The 10-inch props may be too small and the 12-inch may give ground clearance problems. The slo fly props have wider and thinner blades and are for lower RPM. I think they are better used in park flyer BARFS. Regular gas props are overbuilt for electric. The electric props are considerably lighter.

I controlled this kludge with an R/C radio for ease of throttling. I was smart enough to run it outside and avoid the balsa blizzard effect. The plan was to try the motor on an R/C plane but after running it and feeling the blast of air.....We're going directly to the circles soon as we get the timer.

The motor is a PITA to mount. It is an outrunner, the whole outside of the motor rotates around the wiring. The wires come out of the front of the motor and have to pass by the rotating part on their way aft to the speed control. I think a motor that mounted from the rear would be more practical. On a profile plane this will work OK. See posts and pictures by Rick S of his plane. I asked Mikey if it would be okay to modify the plane for electric with the possibility that it may not be undone. He said to go ahead.

Weights as I found them:
OS 25 LA, stock muffler, tank, 9-6 prop, tank and lines 11.9 ounces.
Electric motor, 11 inch APC prop, speed control, battery plus fudge for the awaited timer 12.4 ounces.
Airframe without power components 16.6 ounces. It has been crashed and beefed up in the nose so probably is a couple of ounces heavier than the typical ARF Streak.
So we have 28.5 ounces for the gas, 29 for the electric.

To summarize, for the magic 150 watts per pound we're looking at an 11-7, 11-8.5 or 12-6 APC electric prop. This is about what Rick was saying already but I just had to find out for myself.

More later when we have some flight results.

LAST EDITED ON May-17-06 AT 05:44 PM (CST)
 
Andy Borgogna
The issue you have with the wires being near the prop is very clear in the last photo. The motor I looked at had a set screw on the prop shaft that allow you to bring the shaft forward from either end to avoid just such a problem. It was a very small torque screw in the rotor that you looslen up and with a small mallet you push the shaft in the opposite direction then retighten the set screw.

I will make that a must when I fianlly move to electric.
Andy

Hi again,

I found out that the motor shaft can be removed and then reversed. This way the prop and rotating magnets can be in front of the firewall. The wires will not have to pass over moving parts.

Also I have been playing with the governor function on the Castle Creations Phoenix 35. It works on the bench, but I won't be able to tell until we get the timer whether it will work at the field.

Hello John and Mikey, I would like to ask what is the cost of the
electric power package that you show; excluding the cost of the
TNC Tach, since I already have a tach?
Thanks; Tony G

>Prop RPM Amps Watts
>
>Master 9-6 9880 16.5 184
>APC 9-6 9780 17.6 195
>APC 10-6 8800 22.5 235
>APC 10-8 8110 28.4 285
>APC 12-6E 7000 35 357 this is scary!

The RPM may be down a little in that last test, but those numbers look pretty good to me.

I'm assuming you set up the Whattmeter between the batteries and the ESC. If so, you're reading input numbers, plus these are also static numbers. Your actual inflight RPM will go up a little and the amperage draw will go down. I routinely pull 45+ amps with my set up on the ground (45 amp ESC). The Castle handles it with no problems.

Looks like it should fly fine. Please keep us posted on your results.

Ron King

Costs and cautions

First the bad news. I shorted the output of the Astro charger to ground. The hot lead from the Deans connector touched the hood latch of my truck. A SNAP and the old familiar "I burnt up another component" smell. I've been an electronic hobbyist for 50 years and know that odor very well! The charger rattled so I took it apart. I had blown apart one of the output transistors and the extra piece was loose inside. It doesn't charge now! The discharge function works still.

I would just use another charger in a trickle charge mode if these were NiCads but LiPoly batteries are charged on a constant voltage mode. I have an old 12 volt power supply that I can regulate to 12.3 volts and charge that way but should get a "battery Bunker" to be safe.

I also blew up my CBAII battery capacity tester when I shorted the USB plug to the fan guard when the battery was plugged in. I consider it a design flaw that the metal fan guard is at battery positive potential.

Costs for you who asked:

Typhoon 2912/10 53
ThunderPower 2100 pro lite 70
Castle 35 speed control 65
APC prop 4
Prop adapter 6
Connectors 3
total 201
Astro 109 charger 110
Extra battery 70
Realistic total 381

Use a dedicated LiPoly charger. The Astro works great but watch the hot lead. The convention in electronics is to have the female plug on the power source and the male on the load. Look at the back of your computer at the AC plug if you need an illustration. This means that the charger leads are male and exposed. Maybe the Sermos/Anderson Power Poles would be a better idea. I have them on everything else. I thought the Deans would be more compact.

Since I don't have the timer either looks like flying is put off a week.

Governor mode testing

I loaded the latest CastleLink software into the computer and have been playing around with the governor mode. This is supposed to keep the rotor speed constant for a helicopter. I believe somebody on this forum tried it for controline and had “issues” with its operation. The Phoenix 35 off the shelf does not have this latest “Beta” 1.51 IIRC, version of the software.

I tried the speed control out of the box and it worked okay, just as it was supposed to. Most people would just leave it at that and go fly. My test pilot is still in high school so while I was waiting for the weekend I decided to do some experimenting. The constant speed feature sounded intriguing.

You really need either a servo tester with digital pulse width readout or a programmable R/C transmitter and a receiver on the same frequency.

My setup used an Airtronics Radiant TX and a Hitec 555 receiver. The throttle was on channel 3. Rest was the aforementioned Castle Phoenix 35 controller, ThunderPower 2100 Prolite battery, typhoon 2192/10 motor. I finally found some appropriate APC electric props. Don’t use “Slow Flyer” props; they aren’t designed for the higher RPMS. I still need a 12-6; the 12-8 I suspect is too much.

Here’s how it works. First set up the speed control governor mode using the software. I didn’t try to program it with the transmitter counting the beeps; that’s a PITA. I don’t know if one would want to try this at the field, as you would need a laptop with an USB port. My old one doesn’t have this and at any rate it you can’t see the dim screen except indoors.I just ran into the house, changed setups and then back outside. I think that once you have everything set there wouldn’t be a need to change stuff at the field, except to set the governor speed, which is done through the timer high speed adjustment and a tach.

Settings I used:
Throttle mode governor low speed*
Throttle response hi
Governor response hi
Spool up speed max
Voltage cutoff 9 volts
* Note: the governor hi speed setting caused the motor to start up and run away instead of smoothly gaining speed.

Here we go:
1. Put a “smaller than you intend to fly with” prop on the motor.
2. Put the transmitter into the endpoint adjust mode on the throttle channel. You need to be able to adjust it dynamically while the motor is turning.
3. Set the transmitter to low throttle.
4. Plug in the speed control to receiver channel 3. Make sure the antenna wire is out of the way!
5. Set up your tach to read the prop. I have the tach rubber banded to a spacer so it is off the ground. Point the tach towards the prop and far enough away so that it won’t get hit. The TNC tach locks on very well in all sorts of flight conditions and even with the gray props. You will need to read the tach upside down. I rubber banded the resolution switch on for better… resolution.
6. Turn on the transmitter. Remember: low throttle! If you don’t start at low throttle and low trim it will not work at all.
7. Plug in the battery. The speed control will go into its startup mode with a series of beeps.
8. Hold the motor. You need to make up some kind of fake firewall or something so that you will be able to hold it tightly when it starts moving. Safety first! I suppose you could use the airplane for a test stand. Just remember you need to be able to read all the instruments. Three people or more may be best. One to adjust the throttle, one to hold the plane/motor, one to read the tach, one to read the Whattmeter, one to write down the readings. How did I do this by myself? I dunno.
9. Advance the throttle and adjust for the desired RPM. Don’t be too greedy. The motor will spool up to the set speed. Adjusting the throttle endpoint high end on the timer will change the RPM.
10. The governor will try to keep this RPM the same under varying loads. I found out that the RPM would STAY THE SAME even as the battery ran down! The speed control would just put more juice into the motor to make up for the drop in voltage. This is just what we want for controline!
11. Go fly. This is where the experimental fun begins. Play with props, RPM, whatever.

If you set the speed too close to the maximum output at the start of the flight you will run out of “headroom” for the governor. The battery must have excess capacity for the whole flight for this to work correctly.

DATA

TRANSMITTER SET AT 72 PERCENT THROTTLE ENDPOINT
Prop AMPS WATTS RPM
APC 9-6 7 85 7290
APC 10-6 10.1 128 7290
APC 11-7E 23.6 235 7290
APC 11-8E 27 280 7290
APC 12-8E 35 374 7000*
 SPEED CONTROL AT MAX

It didn’t seem to matter which prop I used. They all gave the same RPM for the same throttle (pulse width) setting.

I thought I had a 12-6 prop, it really was a 12-8. With this prop the speed control could not drive it at the desired speed. There is a red LED on the speed control that comes on when it is at full throttle. Now, when the plane is in the air it may unload the motor and the RPM may reach the governor setpoint. Lots of room for experimenting.

Note: The prop takes quite awhile to spool up, just like a full sized helicopter rotor. I estimate about 10 seconds. I emailed Bernie at Castle Creations and he said that it was supposed to be that way. It’s very intriguing to hold the motor, slam the throttle on and listen for it to come up to speed slowly. If you let go of the plane at the right time it would make for a very smooth takeoff run.

OTOH, when you throttle down the motor stops smoothly and quickly. Like someone just chopped the power. Apparently the spool up feature does not have a spool down delay function. There is no brake in the governor mode.

The soft start and stop may enable one to build lighter airframes.

Ain’t this neat? The proof is going to be in the flying. As they say, “Money talks, BS walks.”

LAST EDITED ON May-19-06 AT 04:14 PM (CST)
 
Thanks for the report.

I may have been the person you mentioned who had "issues" with the governor mode. It works okay, but you cannot use the brake with it and I learned that my controller gave more precise control than the governor. I now use the Fixed throttle instead.

If you don't have my controller, then the governor mode is probably best, except for the lack of brake. The windmilling prop will hurt your glide at the end of the flight, but that's only important if you are competing.

My starting speed is between 75 and 76 percent of full power. Your 72 percent sounds perfect for your plane, prop, and battery.

Safety advice: Please try to find something better to hold that motor. I use a B&D Shopmate, but anything is better than your hands. Let's all be careful out there.

EDIT - CSS

Ron King

>My starting speed is between 75 and 76 percent of full
>power. Your 72 percent sounds perfect for your plane, prop,
>and battery.

>
>Safety advice: Please try to find something better to hold
>that motor. I use a B&D Shopmate, but anything is better
>than your hands. Let's all be careful out there. :+

Ron:

Thanks for the safety tip. For once I quit before I hurt myself. Now to install the whole mess in a plane. I'll shoot for about 7K on the 11-7 prop and adjust up and down from there.

I was able to find a power supply to charge the batteries, Adjusted it to a conservative 12.3 volts and got about 1.98ah out of the battery, which should be good enough to fly. Think I'll keep the charger for now as it is the only discharger I have. Replaced the mosfet in the CBA but it still doesn't work.

Hi John,

I've been off line the last couple of days and just now was able to review your postings on this thread. I was surprized at the beginning when you mentioned pulling 35 amp with an APC 12/6...I have been using this prop on my Flight Streak right from the beginning and pulled an average of 30 amps which is well within the capacity of the motor and battery. In a later post you mentioned it was really a 12/8 and yes, that would pull around the 35 amp you were getting. I found I liked the 12/6 as it achieved a very constant pull through all maneuvers and averaged a 5.1 second lap time. I have no problem with ground clearance since I had added my own 2 wheel landing gear to my Flight Streak. This gear was made long enough to swing a 12 inch prop. The 11/7 APC should also work fine and it should give a faster lap time if thats what you desire.

Yes, the Typhoon shaft can be reversed and I had previously done this modification with one that I have in a R/C 3D model. Since my goal with the original electric Flight Streak was to develop a plane and power system combination which would be relatively low cost and a very easy "start" for someone just entering electric control line I tried to keep it simple and left the shaft "stock". The speed control unit velcroed to the body is forcing the wiring away from the rotating case and I have not had any problems with rubbing.

Congrads on all your experimenting and I'm sure you are seeing just how enjoyable it is and self satisfying with a reward being a great feeling of accomplishment and gaining of knowledge.

Please keep us informed regarding the flying of your Streak. Like Ron confirmed in an earlier post..."it has the right numbers"...I agree, I've been super pleased with mine and it probably has well over 50 flights on it, (by me and probably 10 others) since last August.

Hi John,

Some pictures for clarification of the powertrain mounting on my Flight Streak... (1)close up of the nose area... also shows added 2 wire landing gear made long enough to swing a 12 inch prop... (2)side view... the timer is located on left side of front of body..under black valcro and easily accessible.....

Hi Rick,

OK, now I get it. Thanks for the pics. You made up a firewall at the front of the plane for the motor to mount behind. Looks like about 3/16. I did the same for my test setup except I made a balsa cowl with the motor semi-enclosed with 1/8 lite ply fore and aft.

I found out that the motor came apart when I was running it backwards and the whole assembly moved forward and started rubbing. I was too lazy to reverse the wires. Turns out there was a setscrew in the rotating case that was not tight. Wondered what the wrench that came with the motor was for. Good thing I didn't lose it, probably a metric size. I know the mounting screws are metric, 3mm IIRC.

Another way to mount the motor would be to cut the nose off and make a firewall for a rear mount. This is a common thing to do for the BARFS. Hobby Lobby even sells plastic mounts for this purpose. I think the front mount with the motor behind would provide more protection for the motor. I intend the 1/8 lite ply firewall to be frangible (right word?) like the ablative coating on space capsules for reentry.

All the testing may seem overkill. I’ve always wanted to be an engineer; and for awhile I was a genuine rocket scientist. Guess it shows. Real world testing with my own equipment and the all-important watts per pound tell all. As usual I burnt up some equipment. I think everybody who plays with this electric stuff has burnt something up.For once I didn't cut myself, yet.

Anecdotal evidence can be suspect. I remember when Astroflight came out with their first motor back in 1973 or so. RCM gave it a glowing review but the system was only good for a glider to maintain altitude after you got it in the air with a high start. Bob Boucher said electric was the wave of the future and he was right thirty some years later. It took the brushless motors and LiPoly batteries to make all this practical.

This is not to knock what you and others have done here on this forum. I believe you guys but just had to see for myself.

I have seen the electric controline stuff hanging up at T & A hobby shop but they were small can-motored fly indoor 1/2A-sized airplanes. At the IMS show they would fly around in circles perpetrating the rock-on-a-string myth. Never saw a with regular sized controline stunter fly. It’s ironic that Tony is going out of business at this time. He and his Mom were the pioneers in the electric airplane field.

We are getting spoiled with the Internet online ordering. The motor took one day to get here, speed control and batteries two days. I ordered a timer from Windy snail mail with a check and it’s been a week. Since I ordered a video at the same time it’s probably going by stagecoach instead of First Class. Since I had all the other stuff why not try it out while I was waiting? I wasn’t going to cut up the plane until I could see for myself that it had enough power.

I even designed my own timer for a backup and to see how complicated it was. I’m old analog guy so used 555 timers instead of a PIC. What I came up with has 4 IC’s, 3 diodes, 9 capacitors, 2 pots, 9 fixed resistors, an LED and a switch. It sends a low throttle pulse to the speed control then when the button is pushed goes to high throttle for a time, then back to low to cut off the motor. This abrupt start wouldn’t be practical except the speed control has soft start and adjustable brake functions. I’m not about to build this; electronics WAS my hobby when I was a kid. Now I build model airplanes.