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Old 10-24-2012, 04:02 PM   #1
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Default Hacker A30-12XL V2 with 2 cell battery?

So I started messing around with this prop calculator:

http://www.s4a.ch/eflight/motorcalc_e.htm

A setup I was looking at was having a:

Model weight: 86 oz
Field elevation: 200 ft
Battery: Lipo 2500mah - 25/35C , 2 cell with 4 in parallel
Controller: max 40A
Motor: Hacker A30-12XL V2 (700)
Propeller: Carbon-fold-prop, 13x7 2 blade

According to the calculator, this setup has a mixed flight time of 66 minutes and draws 100 Watts at full throttle (if I'm reading it correctly). For what I'm trying to build, this is perfect.
When I look up the specs of the A30, however, it says to use between 3S-5S batteries.

So is the calculator wrong in thinking a 2 cell battery can power this motor? I'm not looking to fully max out the motor, I'm trying to just get enough thrust to lift off and then maintain cruise flight (a slowflyer). Because if not, I'll have to use another motor. But if 7.4 V is enough to start the motor and give me the thrust it states in the calculator, this is exactly what I'm looking for.

P.S. I'm using 2 cell batteries because of the setup I'm making would be more complicated with 3 cells.
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Old 10-24-2012, 08:25 PM   #2
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the motor will run on two cells but it just wont produce much power. you could increase the power a bit by putting on a bigger prop but you wont be using the motor to it's full capability.

With a 86oz model and only 100W of power I'm afraid that you wont even get off the ground. If the plane is a sailplane type design with outstanding aerodynamic efficiency it might just about be able to maintain altitude on 100W but if it's a more typical design it wont even be able to stay airborne even if you hand launched it.

You would typically be looking at more like 300W+ of power minimum if you expected to be able to take off from the ground and even then it's going to be pretty sluggish and need a good long runway.
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Old 10-24-2012, 11:18 PM   #3
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Originally Posted by DannyShadow View Post
So I started messing around with this prop calculator:

http://www.s4a.ch/eflight/motorcalc_e.htm

A setup I was looking at was having a:

Model weight: 86 oz
Field elevation: 200 ft
Battery: Lipo 2500mah - 25/35C , 2 cell with 4 in parallel
Controller: max 40A
Motor: Hacker A30-12XL V2 (700)
Propeller: Carbon-fold-prop, 13x7 2 blade

According to the calculator, this setup has a mixed flight time of 66 minutes and draws 100 Watts at full throttle (if I'm reading it correctly). For what I'm trying to build, this is perfect.
When I look up the specs of the A30, however, it says to use between 3S-5S batteries.

So is the calculator wrong in thinking a 2 cell battery can power this motor? I'm not looking to fully max out the motor, I'm trying to just get enough thrust to lift off and then maintain cruise flight (a slowflyer). Because if not, I'll have to use another motor. But if 7.4 V is enough to start the motor and give me the thrust it states in the calculator, this is exactly what I'm looking for.

P.S. I'm using 2 cell batteries because of the setup I'm making would be more complicated with 3 cells.
Lets see.
You've got a model that weighs in at 86 ounces, or 5.3 pounds. IMHO, minimum power requirements for a reasonable acrobatic model is 100 watts per pound, or about 550 watts. This would be pushing the A30 motor a little bit. By the way, typical flight times for these electric models is on the order of 5 to 10 minutes.

Again, IMHO, a Hacker A40 motor would be much more appropriate for your model. The A40-10S, or similar powered motor would provide sufficient power to get your model off the ground quickly, and perform well.

Another computer program for determining flying capability is www.motocalc.com, free for 30 days, then $39. Its well worth it.

I've got the Hacker A40-12S motor in one of my models, it flys very well on a 6S1P (Six series, One parallel) 2300 Mah A123 battery. Or a 5S1P LiPo of around 3000 Mah.

What you do not want is an underpowered electric model. These electric systems, properly setup can compete very favorably, or even exceed the performance of the same model with glow engine power.

Here is some reading info for those larger models:
Thread on 70 size glow engine conversion to electric
http://www.wattflyer.com/forums/showthread.php?t=45222

Hacker 6S2P A123 powered Models
http://www.wattflyer.com/forums/showthread.php?t=44686

AEAJR's Site on Electric Power
http://www.wattflyer.com/forums/showthread.php?t=18521

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Old 10-25-2012, 01:13 AM   #4
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Originally Posted by JetPlaneFlyer View Post
the motor will run on two cells but it just wont produce much power. you could increase the power a bit by putting on a bigger prop but you wont be using the motor to it's full capability.

With a 86oz model and only 100W of power I'm afraid that you wont even get off the ground. If the plane is a sailplane type design with outstanding aerodynamic efficiency it might just about be able to maintain altitude on 100W but if it's a more typical design it wont even be able to stay airborne even if you hand launched it.

You would typically be looking at more like 300W+ of power minimum if you expected to be able to take off from the ground and even then it's going to be pretty sluggish and need a good long runway.

Based on some testing I did last year with e-powered sailplanes, he might just be able to get by on 100 watts - barely.

I did some experiments trying to see just how low a power level I could get by with on an e-powered sailplane. My goal was weight savings. I wanted an e-sailplane that weighed no more than its un-powered version. I didnt want to mess with hi-starts or winches and my knees wont let me launch DLG's any more, so I needed enough power to climb to a reasonable altitude, but at absolute minimum weight.

I was surprised at how little was needed.

The lowest numbers I tested was about 20 watts per pound but that still gave about 300 ft/minute climb rate with careful climb angle management.

That power level felt a little to marginal though. With24 watts per pound I was up to 460 ft/min climb rate and that was much more comfortable - as long as the wind wasnt blowing I would not fly at that low a power level in much more than 5 mph winds.

If your not very careful managing the climb angle, you can spend a lot of time going no where On the other hand, keeping the model in the air was no problem.

Now - some critical details here:

1) The models I was using as test beds have very low wing loadings. The two sailplanes I used ranged from about 7 oz/sq ft to just under 5oz/sq ft. I am quite certain this would not work well at much higher wing loadings. The models I was using are very slow flyers that I lightened up structurally to the minimum I could get by with. Higher wing loadings require higher flight speeds and I just dont think you could get there with this low a power level.

2) In order to keep the weight down I was using very small packs, so even at these low power levels flight times were not long.

3) All my launches were hand launches into a small breeze. It required careful flight control during the initial seconds of launch until the model built up sufficient speed. Again, this is where a higher wing loading would make things that much more difficult.

So - I think he could just possibly get by with an 86 ounce model on 100 watt power system - maybe

However, it would be very iffy AND he would have to be flying a very efficient model with a relatively low wing loading and the ability to fly at very low speeds easily.

A much better approach would be to use a power system that had a significantly higher peak power that could be used during take offs and emergency's, then just throttle back in the air. Actually, once you are at altitude you can get by with even less power to keep it there.

Also, a motor like the Hacker A30 series is a poor choice for a low power setup. It will be running at a low efficiency at that low a power level. Id recommend you look for a motor that has a peak power level in the 200-300 watts range and just throttle back after take off. That smaller motor will save you an extra ounce or two as a bonus

Still, before you decide on a power system, you should give us some more details on the model - wing span, cord, wing area, planform, etc etc. Also, the flight profile or mission would be very helpful as well as where you intend to fly from - landing area, takeoff runway or hand launch etc.

The more details you provide, the more the experts on this site can help

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Old 10-25-2012, 04:59 AM   #5
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Thanks guys.

So I should begin with the fact that this plane isn't even a physical entity yet. I'm in a group trying to build a solar powered plane from scratch for our senior design project for our university. We're currently in the design phase for this semester and I was in charge of the propulsion of this RC.

What I can tell you is we're shooting for at most 7 pounds total weight. The airfoil is going to be modeled as E214. The wingspan is 10 feet I think. The chord length is 16 inches. And there are only enough solar panels to provide 200 Watts of power. We were planning on powering the plane with one of the batteries while the solar panels charges the other 3 batteries and just let it alternate battery pack. It will be hand launched and has a tractor configuration.

So if my configuration seems far-fetched, it's because of the difficult task of I was handed due to the above. So if you have any suggestions, I'm all ears!
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Old 10-25-2012, 06:43 AM   #6
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Originally Posted by DannyShadow View Post
Thanks guys.

So I should begin with the fact that this plane isn't even a physical entity yet. I'm in a group trying to build a solar powered plane from scratch for our senior design project for our university. We're currently in the design phase for this semester and I was in charge of the propulsion of this RC.

What I can tell you is we're shooting for at most 7 pounds total weight. The airfoil is going to be modeled as E214. The wingspan is 10 feet I think. The chord length is 16 inches. And there are only enough solar panels to provide 200 Watts of power. We were planning on powering the plane with one of the batteries while the solar panels charges the other 3 batteries and just let it alternate battery pack. It will be hand launched and has a tractor configuration.

So if my configuration seems far-fetched, it's because of the difficult task of I was handed due to the above. So if you have any suggestions, I'm all ears!
Interesting project.
With this info, methinks you are going to need a motor that can turn a large diameter propeller at a fairly slow RPM. And that motor will have to be very efficient, ruling out a lot of the cheaper motors.

Note that all of the human powered airplanes that were built years ago also used a large, slow turning propeller. APC-E has a lot of electric only propellers, up into the 20 inch diameter plus area that might be useful.

www.motocalc.com has a lot of useful calculating ability, but don't know how accurate it would be on a very large, lightly loaded model in your project. What motocalc will do is allow calculations and thrust output on various motors, propellers and battery systems that might be useful.

I think one of the Hacker A40 series motors would be the way to go. Hacker motors are known for being very efficient, and they do perform per their specifications. Note the motocalc spreadsheet shows the Hacker motor running at 90% efficiency, a very good number. (I've got 8 of them, from an A30 to two A40's, three A50's and two A60 power houses.)

Just ran the numbers on a Hacker A40-12L motor with a direct drive, with a 5 cell LiPo battery. With a 16X6 prop, it will provide about 900 feet per minute rate of climb. Take a look at the motocalc file attached. A lot more info is available from motocalc than shown on the attached JPG.

This looks to be a very interesting project. Be sure to keep us wattflyer readers posted on your progress and results!

http://www.apcprop.com/SearchResults.asp?Cat=24

http://www.aero-model.com/Hacker-Bru...By-Series.aspx


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Old 10-25-2012, 09:41 AM   #7
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Denny, he only has a max of 200 watts to power the motor - they are using solar power. The batteries are just for temporary storage. Actually, it sounds like they want to use 1/2 of that 200 watts to re-charge 1/2 the pack while the other half flys the plane, switching back and forth. So in reality, they only have a 100 watt budget to fly with.

I think they could 'cheat" a little bit though. If they are careful with the design, the plane just might cruise at something under that 100 watt level. That will, hopefully, leave them some excess energy from the initial charge on the packs to use during the take-off and climb out.

On second thought, they will have both halves of the pack fully charged on the initial take off, so they do have extra energy they can spend. That can be used to make the take off and climb, then drop to cruise power levels and start the charge cycle at that point flying 1/2 the pack at a time.

Danny - I think you guys are going to have to stick to your guns when it comes to weight savings. Build in as much "lightness" as you possibly can at every step in the design process and resist all temptations to add "just a little bit more" of anything!

I also think you need to look at a motor that will be efficient at lower power levels. if you try to run a hi power motor at low power levels, the efficiency drops off dramatically.

I agree with Denny's comments about swinging a big prop. Bigger props are more efficient. The problem is that smaller, lower powered outrunner motors generally have to hi a kV to swing large props at low power levels. Id suggest you look at a geared inrunner motor instead.

Again, which exact motor you choose will depend entirely on your final all up weight. Thats a critical piece of data you need before you can do your final power budgeting. The lower that weight numbers is, the better your chances of success are.

Seriously, I cant emphasize that enough - weight is going to be your #1 enemy on this project.

For example, if you end up at 7 pounds instead of the 5.3 you initially mentioned, your 100 watt number is almost certainly not going to work. At 7 pound you only have 14 watts per pound to fly the plane. Your wing loading works out to 8.4 oz/sq ft roughly, which isnt bad but is still significantly above the numbers I was working with on the very low power loading experiments. If you double your take off power to 200 watts, you just might make it work - if the model is very well built as far as low drag, clean airfoils etc.

However, your taget of 120" span with a 16" cord and an all up weight of 7 pounds is going to be a real challenge to build. Let me clarify that.

Im certain you could build a model that meets those specs - if you were a careful builder - but - that would be WITHOUT the solar cells!

How much do your solar cells and all their associated wiring, power management/charging hardware and mounting hardware weigh all by themselves?

I assume you are planning to cover the entire wing with these cells? Will the cells conform to the airfoil you've chosen? Have you thought about what it will take to incorporate them into the wing structure while preserving the airfoil and keeping the wing strong enough to resist in-flight forces? Keep in mind too that the wing will flex in flight both in bending and torsion.

I wish you guys the best of luck. You have a very challenging project ahead of you. It should be a lot of fun!!

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Old 10-25-2012, 09:45 AM   #8
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Denny, I dont have motocalc re-installed on my new computer. Why dont you re-run your simulation with a peak of 200 watts and an all up weight of 120 ounces and see what you come up with. Run it with a 2S pack and what ever size prop it takes to get to 200 watts.

Id like to see what the climb and efficiency numbers looks like under those conditions.

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Old 10-25-2012, 09:53 AM   #9
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Danny - I just had another thought that may help you guys some. I dont think you need to carry around all that battery weight.

What about cutting down the size of your lipo packs drastically. Size them to give you around 25 watts per pound of all up weight but only plan on 2 or 3 minutes of run time. You could maybe go to 6 minutes to give you some margin. You should be able to do that with a relatively small and light weight pack.

Then after take off - fly on the entire 200 watts you will be getting from your solar cells.

To keep things simple - and save more weight - you could leave the lipo in the circuit full time and just charge it with the solar cells - just be sure to limit your in-flight power usage to no more than the solar cells put out - allowing for charging in-efficiencies, losses etc.

That should be able to shave off a pound or more from your all up weight

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Old 10-25-2012, 10:05 AM   #10
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Here are some numbers for you to consider. Lets assume you can actually build a model with an all up weight of 7 pounds. I think thats going to be very dificult, but it gives us a place to start the calcs from

So 7 pounds times 30 watts/pound = 210 watts. Woo Hoo! You only need an additional 10 watts from the lipo for take off and climb out!

Lets say you end up at 10 pounds all up. Thats still only 300 watts total for take off, so your lipo only needs to provide 100 watts for 3 to 6 minutes. You could easily get by with a hi quality 500 mahr 2 cell pack with room to spare.

Thats assuming your model ends up pretty efficient as far as flying goes - low drag etc. Your aspect ratio is going to be fairly low as far as sailplanes go and if your not carefull with the solar panel install drag and airfoil performance could go south easily.

If thats the case, you may need as much as 60 watts per pound. Thats a 600 watt setup.

So that leaves 400 for the lipo to provide. On a 2S setup that still only requires about 48 amps. So a single 2S 2000 mahr pack should do fine to get you through take off.

The question then becomes, can you less efficient model stay in the air on only 200 watts? Thats going to be very iffy.

In any case, you see that you can save a good bit of weight on the lipos from the start. Try to use that type of approach on each part of the design.

Good luck!

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Old 10-25-2012, 10:23 AM   #11
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So it's a 7lb (112oz) model now, that's already gone up 26oz in a few minutes

Having all the facts is usually a big help in these things. You say the solar panels can give 200W; ok but will all of that be available for propulsion or is some used for charging? Also is 200W the realistic average value based on real world conditions (sun intensity where and when you fly, clouds, the typical inclination angle of the panels to to sun etc.) If 200W is the theoretical figure based on the manufacturers claimed peak values in ideal conditions then you would be lucky to average half of that an real world conditions with wing mounted panels.

Sounds to me like the project needs to do a feasibility study using realistic and reasonably accurate and conservative data to make sure that you aren't all off and working on mission impossible.

I appreciate that it may not achieve the objectives of your project but by far the easiest way to fly solar power is to charge the batteries on the ground from solar panels and just fly the plane the 'usual way' on battery power alone. For most of the hobbyist level solar power projects I've seen end up being highly debatable as to if the meagre power supplied by the solar cells can even compensate for the added weight associated with the solar power paraphernalia.

Good luck with the project anyway.. If it's any help the previous advice to look for the motor that will spin a very large prop is great advice. Large props are more efficient and will give you more thrust for your watts. You also need to be totally fanatical on weight saving to stand any chance of success.
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Old 10-25-2012, 08:45 PM   #12
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Originally Posted by Larry3215 View Post
Denny, I dont have motocalc re-installed on my new computer. Why dont you re-run your simulation with a peak of 200 watts and an all up weight of 120 ounces and see what you come up with. Run it with a 2S pack and what ever size prop it takes to get to 200 watts.

Id like to see what the climb and efficiency numbers looks like under those conditions.
Yup
I ran the numbers in motocalc for a 117 ounce total weight model airplane. Looks like the A30 series motors can't do the job, their motor efficiency drops to much. The A30 series motors wound up with negative rate of climbs, indicating at full power, the model will loose altitude. The predicted A30 motor efficiency wound up in the low 70% value with the power selection used. This is not to good.

The A40-10S looks somewhat feasible. Motocalc suggests that motor will turn a 13X6 prop at about 6000 RPM on a two cell LiPo, pulling 31 Amps and 222 watts. The predicted Rate Of Climb is 230 feet per minute. (This is a very low ROC figure) With a three Series LiPo, and with a proper propeller selection, that would result in near doubling the ROC rate, but would also double the watts input to your motor. The Hacker A40 series motor will have some 85% efficiency on two cells. At higher voltages, that A40 motor can hit 90% efficiency.

The very serious risk you have is an underpowered model that can't maintain altitude, resulting in a busted up airplane on its maiden flight. Nice thing about the Hacker A40-12S motor, you can do your test flights on a 3S or 4S LiPo with pretty good chances of getting it into the air, and get the model trimmed out. And not worry about burning up the motor. Then, after getting the model trimmed out, you can drop back to the available power you have and see what performance you can get.

You could even go for making a power switch over in the air to switch the motor/ESC from the 4S LiPo battery to your solar power and see if it can maintain altitude. I've got a small very simple Microchip Microcontroller project that can control a simple high current relay to do the switchover on an unused channel on your transmitter. It's presently used to light up LED's, but adding a small power relay would be rather easy to do. A few Mosfets could replace the relay, but mosfets will have problems with interacting between each other when only one is turned on.

As others have indicated, total weight of this project will be absolutely critical. A few ounces overweight, or poor airfoil can result in a model that can not maintain altitude at full power.

If it is possible to increase the cell count to a 3S LiPo, that would give a very significant increase in performance, and would make a positive outcome very feasible.

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Old 10-25-2012, 09:02 PM   #13
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Originally Posted by kyleservicetech View Post
If it is possible to increase the cell count to a 3S LiPo, that would give a very significant increase in performance, and would make a positive outcome very feasible.
I don't think it would help because the plane is supposed to sustain flight on the power available from the solar cells. Play whatever tunes you like with the batteries but you still only have the watts available that the solar cells can produce, which we are told is either 100W or 200W.

Also bear in mind that sticking an A40 will add about 5oz to the overall weight compared to a small A30 motor (A30-28S for instance). A A30-28S is more than capable of coping with the predicted 100-200W. 5oz is a whole bunch of weight for a weight critical project such as this.
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Old 10-25-2012, 09:08 PM   #14
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Originally Posted by JetPlaneFlyer View Post
I don't think it would help because the plane is supposed to sustain flight on the power available from the solar cells. Play whatever tunes you like with the batteries but you still only have the watts available that the solar cells can produce, which we are told is either 100W or 200W.

Also bear in mind that sticking an A40 will add about 5oz to the overall weight compared to a small A30 motor (A30-28S for instance). A A30-28S is more than capable of coping with the predicted 100-200W. 5oz is a whole bunch of weight for a weight critical project such as this.
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I've run the numbers through www.motocalc.com. The results show that the Hacker A30 motor's efficiency will drop to far, and the predictions show that with the Hacker A30 motor, the model will not maintain altitude.

Some of the motocalc predictions for the A30 motor show efficiency dropping between 60 and 70%. Very poor numbers in a critical application like this one.

Many years ago, I built a 8 foot wingspan sailplane powered by a rewound brush type geared motor. The power output was on the order of 200 watts or so to the shaft. That model just barely maintained altitude, climbing out to only a 60-80 feet or so on a three minute flight starting with a full battery charge.

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Old 10-26-2012, 12:22 AM   #15
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What about a little playing with the rules if possible? Would make a big difference in your power system.

Do the rules of your task specifically state it has to take off under it's own power, or that it just has to maintain flight?

Just thinking if it's the latter, you fudge on the launch. Bungee/high start/winch it into the air, then let the motor take over. Heck for that matter all you would need is a nice hill to slope soar it up, then kick in a just enough power system to keep her flying.

Just a thought.

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Old 10-26-2012, 01:12 AM   #16
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Originally Posted by kyleservicetech View Post
Yeah
I've run the numbers through www.motocalc.com. The results show that the Hacker A30 motor's efficiency will drop to far, and the predictions show that with the Hacker A30 motor, the model will not maintain altitude.

Some of the motocalc predictions for the A30 motor show efficiency dropping between 60 and 70%. Very poor numbers in a critical application like this one.

Many years ago, I built a 8 foot wingspan sailplane powered by a rewound brush type geared motor. The power output was on the order of 200 watts or so to the shaft. That model just barely maintained altitude, climbing out to only a 60-80 feet or so on a three minute flight starting with a full battery charge.
Denny, the A30 efficiency numbers will too low - even though its supposed to be a 200 watt motor - because, on 2S, the current will have to be too hi. It will be in iron saturation. Outrunners tend to have a pretty narrow peak efficiency current range.

A hi kV inruner on the other hand will be just fine at the higher current, lower voltage.

Thats why I suggested a geared inrunner. Im sure there is a combo that will perform well at 200 watts on 2S at higher currents but still be able to swing a larger prop. One of the hi kV baby Neu motors with a 6.7/1 gear box perhaps.

I think I need a signature.
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Old 10-26-2012, 01:20 AM   #17
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Originally Posted by JetPlaneFlyer View Post
So it's a 7lb (112oz) model now, that's already gone up 26oz in a few minutes

Having all the facts is usually a big help in these things. You say the solar panels can give 200W; ok but will all of that be available for propulsion or is some used for charging? Also is 200W the realistic average value based on real world conditions (sun intensity where and when you fly, clouds, the typical inclination angle of the panels to to sun etc.) If 200W is the theoretical figure based on the manufacturers claimed peak values in ideal conditions then you would be lucky to average half of that an real world conditions with wing mounted panels.

Sounds to me like the project needs to do a feasibility study using realistic and reasonably accurate and conservative data to make sure that you aren't all off and working on mission impossible.

I appreciate that it may not achieve the objectives of your project but by far the easiest way to fly solar power is to charge the batteries on the ground from solar panels and just fly the plane the 'usual way' on battery power alone. For most of the hobbyist level solar power projects I've seen end up being highly debatable as to if the meagre power supplied by the solar cells can even compensate for the added weight associated with the solar power paraphernalia.

Good luck with the project anyway.. If it's any help the previous advice to look for the motor that will spin a very large prop is great advice. Large props are more efficient and will give you more thrust for your watts. You also need to be totally fanatical on weight saving to stand any chance of success.
I didnt want to come right out and say it, but i think Steve's assessment of the situation is spot on.

As far as I know, the only people to ever be successful at sustained flight on solar power were those guys in Europe a year or so ago. They had a huge budget, access to the latest and greatest tech and every thing they did was to NASA standards.

It's hard to imagine achieving successful flight with off the shelf solar cells and a home built model.

Danny - if you would post the specs on your cells - weight, output per sq ft, etc, etc - that will give us a much better idea if this is even close to possible.

On the other hand, Id be willing to bet your prof isnt expecting success anyway. I suspect he is more interested in the effort you put into it rather than whether or not you achieve the goal

I think I need a signature.
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Old 10-26-2012, 03:07 AM   #18
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Originally Posted by Larry3215 View Post
Denny, the A30 efficiency numbers will too low - even though its supposed to be a 200 watt motor - because, on 2S, the current will have to be too hi. It will be in iron saturation. Outrunners tend to have a pretty narrow peak efficiency current range.

A hi kV inruner on the other hand will be just fine at the higher current, lower voltage.

Thats why I suggested a geared inrunner. Im sure there is a combo that will perform well at 200 watts on 2S at higher currents but still be able to swing a larger prop. One of the hi kV baby Neu motors with a 6.7/1 gear box perhaps.
Yeah, that's what I indicated in posting #14.

For those readers not familiar with iron saturation, this is a critical issue. Very critical! So what is it? Iron saturation is the maximum number of ampere turns a particular piece of magnetic iron can handle. The Ampere turns item is simply the number of amperes flowing through a given number of turns of a electromagnet. So, 50 Amps times 12 turns is 600 Ampere turns. Same thing for 25 Amps and 24 turns, also equals 600 Ampere turns.

Added additional ampere turns will not result in an increased magnetic field. This characteristic is one reason applying 240 Volts AC to a 120 Volt AC sump pump motor in your home will burn it up.

As for DC motors, running to much current through the winding can also result in saturating the steel magnetic path of your motor. Now, the current limit is not determined by the inductance of the winding, its determined by the resistive portion of the winding itself. You suddenly have very high peak currents, and those peak currents do not turn the shaft, these peak currents simply heat up the motor windings.

I thought about a gear drive, but Hacker outrunners do not easily accept gear drives. And the Hacker inrunners are likely designed for much higher power levels.

Never thought about those Neu geared motors. I've seen several of them in the nose of competition electric sailplanes. To say they have a lot of horsepower would be a great big understatement.

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Old 10-26-2012, 10:07 AM   #19
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Originally Posted by DannyShadow View Post
So I started messing around with this prop calculator:

http://www.s4a.ch/eflight/motorcalc_e.htm
[clip]
According to the calculator, this setup has a mixed flight time of 66 minutes and draws 100 Watts at full throttle (if I'm reading it correctly). For what I'm trying to build, this is perfect.
Danny.

Bear in mind that eCalc is a very simplified program and it does not actually work out if the plane will have enough power to fly or not. The flight time it displays is based purely on the amps that are calculated to be drawn from the battery and the capacity of the battery. You could put a model weight in of 1,000,000oz and the flight time according to eCalc would still be 66 minutes
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Old 10-26-2012, 05:42 PM   #20
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Originally Posted by JetPlaneFlyer View Post
Danny.

Bear in mind that eCalc is a very simplified program and it does not actually work out if the plane will have enough power to fly or not. The flight time it displays is based purely on the amps that are calculated to be drawn from the battery and the capacity of the battery. You could put a model weight in of 1,000,000oz and the flight time according to eCalc would still be 66 minutes
The www.motocalc.com and similar $$$$ programs are a little more realistic.

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Old 10-27-2012, 10:40 PM   #21
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Hope we havent scared him off!

I think I need a signature.
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Old 10-29-2012, 01:02 AM   #22
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I wasn't expecting such feedback! Thanks everyone. I haven't gotten a chance to read everything yet but I'm interested in seeing what everyone says.
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Old 10-29-2012, 02:17 AM   #23
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Originally Posted by DannyShadow View Post
I wasn't expecting such feedback! Thanks everyone. I haven't gotten a chance to read everything yet but I'm interested in seeing what everyone says.
That feedback comes at a price! All of us wattflyers are expecting a report on your results (good or ???) after you've made your first flight!

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