A low power ducted fan

[quorneng]

One thing I did notice was that the fan did not speed up at all in a dive as you would expect a prop to do, suggesting that for the speeds I am flying at the inlet air is always at such a low speed so as to be insignificant to the fan, probably due to its very coarse pitch.
In due coarse I would like to fit an equivalent commercial EDF unit and see what difference there is when it is driven at the same sort of rpm.

[babylon5]

Originally Posted by Bill G

Quorneng I'm not surprised that the fan blade performs as well without the duct at the flying speed it is at. My FW190 TL would probably be just as fast with a 70mm prop sticking out of the front of it. It would look pretty silly that way though.

Go back and look at the launch of my small prop Savoia S64 video. It was almost as difficult to get the initial hang of it, as your SPAD was. Very responsive.
The FW190TL I showed has an Align motor also. It's a 430L. I'm convinced it should hold up on 4s, as it doesn't warm much on 3s. I may try it with 4cells for more speed.

Bill, I saw your video launch. Tricky especially if you are on mode 2 and a right handed person.
Me I am a right handed person but on mode 1, that is my left finger is always on the left stick that control the elevator and rudder and hence has some measure of control during a launch. I use my nose to push the throttle up while holding the model on my right hand. No such luck if you are right handed on mode 2.
However, there mode 2, right handed person who has master a good toss (with throttle off or low ) and some quick fingers during a DIY launch with great success.

Another good DIY launch is a model with generous vertical fin area. Plane with such a configuration generally are less likely to yaw or roll over during a DIY hand launch.

Cheers

[quorneng]

babylon5
Ah Someone else who launches using their nose!
Mode 2 but left handed. Must admit it never occurred to me how this could be a problem for right handers.

[babylon5]

Originally Posted by quorneng

babylon5
Ah Someone else who launches using their nose!
Mode 2 but left handed. Must admit it never occurred to me how this could be a problem for right handers.

Agree , my nose becomes quite important for the hand launch too in mode 1!. ha ha "launching with your nose" great idea.

Actually mode2 for left handed is not a problem , easier to launched because the right hand would be always on the elevator and aileron and the left hand which is the stronger hand(for left handed) would do the tossing of the aircraft.

On the other hand a right handed person on mode2 would never be able to toss the aircraft well, with their weaker left hand with the exception of an ambidextrous

Cheers

[quorneng]

To allow the possibility of using a prop instead of the fan I have moved the booms outboard.
As the aerial went down one and the elevator servo wire down the other quite a bit of surgery was going to be required.
It seemed logical to move the booms out to the full span of the tailplane.

All the holes in the wing made good.

The original duct was not really that close fitting with between 1 & 2 mm clearance.
This problem was addressed by gluing a layer of 2mm Depron on the inside of the duct. This of course seriously fouled the blades but being soft could be 'worn away' by simply running the fan slowly up to speed until it ran free.

It now has a working clearance between 0.1 & 0.2 mm which should improve its performance a bit.
Too foggy to fly at the moment!

[Bill G]

Originally Posted by quorneng

babylon5
Ah Someone else who launches using their nose!
Mode 2 but left handed. Must admit it never occurred to me how this could be a problem for right handers.

I always get a kick out of folks who hit the throttle, using their teeth.

I think I'm really lucky with my strange hand coordination, as I hand launch myself, and fly with one hand on the trans, while filming with the other. I'm left handed when writing, but use scissors with my right hand, and couldn't think of using them with my left. That works out well, as I can easily hold the trans with my right hand and fly with just my right thumb, hand launch with my left hand, and then grab the camera hung on me with a neck strap with my left hand and then start filming.

Originally Posted by quorneng

One thing I did notice was that the fan did not speed up at all in a dive as you would expect a prop to do, suggesting that for the speeds I am flying at the inlet air is always at such a low speed so as to be insignificant to the fan, probably due to its very coarse pitch.
In due coarse I would like to fit an equivalent commercial EDF unit and see what difference there is when it is driven at the same sort of rpm.

If you don't have any fan units on hand? If not:
I have so many GWS EDF55 and 64mm fans around here, that I might be able to fix you up with one. Your plane looks light enough that it should fly without a ballistic motor. I have some older 370 series brushless inrunners laying around here that are not exactly new, nor powerhouses, but should fly something with a large wing and light loading.

Edit:
I put an EDF55 together with a Hacker E-series 370-4900kv motor last night. The motor is a piece of work. I now know that it will handle reasonable power, as the fan was ran to full power on 3s. The motor had 2 wires that were nicked by a mounting screw that was too long, and eventually blew. I pryed the broken winding ends away from the windings, scraped the insulation with an exacto blade, and soldered short jumpers across the breaks. The motor ran fine afterward, and was finally ran last night with real usage power. The shaft is a few thou larger than the "old" standard GWS adapter, so I found an adapter that had been honed. I spent a while adjusting the 2 adapter allen set screws, for best centering, and have it running reasonably well.

[babylon5]

Originally Posted by Bill G

I always get a kick out of folks who hit the throttle, using their teeth.

I think I'm really lucky with my strange hand coordination, as I hand launch myself, and fly with one hand on the trans, while filming with the other. I'm left handed when writing, but use scissors with my right hand, and couldn't think of using them with my left. That works out well, as I can easily hold the trans with my right hand and fly with just my right thumb, hand launch with my left hand, and then grab the camera hung on me with a neck strap with my left hand and then start filming.


Do you have any commercial EDF units?
I have so many GWS EDF55 and 64mm fans around here, that I might be able to fix you up with one. The plane looks light enough that it should fly without a ballistic motor. I have some older 370 series brushless inrunners laying around here that are not exactly new, nor powerhouses, but should fly something with a large wing and light loading.

Hi Bill ,
I have some info on the various current with the 6blade gws55 mm edf or its equivalent on good 3S lipo 1750mah 25C when the aircraft is stationary
I hope this info is useful.

1) 20mm diameter inrunner motor welkera 3.2KV/v draws 12-13 amps

2) 20mm diameter inrunner motor Tahmazo reno class 3.7KV/v draws 16-17amps

3) 20 mm diameter motor no name 3.9-4Kv/v 20-21 amps

4) outrunner P2627L-4200(from H.K)4.2KV/v 24-26 amps

5) outrunner 4.5KV/v 27-30amps similar to item 4 except higher KV


item 3 onwards (need heat sink or outrunner motors)

This will give you the idea of the expected current when the aircraft is stationary.

The running current will drop significantly if the aircraft can translate the thrust to speed. If the aircraft is of low drag design and can penetrate the air with ease , it will consumed a lot less current in flight.

here is the video link to my experimental EDF SPAD interceptor using the P2627L-4200 motor with the 55mm GWS EDF

My micro EDF SPAD(corrugated plastic) interceptor

Cheers

[quorneng]

The latest mod is to move the booms outboard to allow a conventional prop to be used.
As the aerial goes up one boom and the elevator servo wire up the other quite a bit of work was required so I thought I might as well move them out to the span of the tailplane.

The original duct had up to 2mm tip clearance so I glued a layer of 2mm depron all the way round the inside. This of course seriously fouled the blades but as depron is soft it was simply 'worn away' by slowly running the fan up to speed until it was free.

It now has about 0.2mm tip clearance all round.
The result is it now seems to fly on even less power but the question is how much is it actually taking?
My solution was to create this ground run video with the various current draws recorded.

YouTube Video

By simultaneously comparing this with the motor pitch from a DuctFan flight video the current draw can be determined reasonably accurately particularly as the fan does not off load at all in flight.

The answer is 3.5A. Wow!

[mclarkson]

That's pretty low power. Congrats on your cool, evolving project.

[babylon5]

Originally Posted by quorneng

The latest mod is to move the booms outboard to allow a conventional prop to be used.
As the aerial goes up one boom and the elevator servo wire up the other quite a bit of work was required so I thought I might as well move them out to the span of the tailplane.
Attachment 142317
The original duct had up to 2mm tip clearance so I glued a layer of 2mm depron all the way round the inside. This of course seriously fouled the blades but as depron is soft it was simply 'worn away' by slowly running the fan up to speed until it was free.
Attachment 142318
It now has about 0.2mm tip clearance all round.
The result is it now seems to fly on even less power but the question is how much is it actually taking?
My solution was to create this ground run video with the various current draws recorded.

YouTube Video

By simultaneously comparing this with the motor pitch from a DuctFan flight video the current draw can be determined reasonably accurately particularly as the fan does not off load at all in flight.

The answer is 3.5A. Wow!

Hi,quorneng , may i know how what type of ammeter and how you measure the current.

Standard ammeter has internal resistance that will result in much lower amps reading. The most accurate ammeter is the one that sense the current by magnetic means. Such ammeter comes with a fork or thongs that simply clamp around either the +ve or -ve wire to read off the DEc current.
They do not introduce resistance to the loop circuitry.

In addition, some of this ammeter can read the frequencies of the 3 phase wire and can be translated to working rpm of the EDF.Its a very cool device

here is the link of the ammeter Kyoritsu Kewmate 2000/2001

http://www.yf-instruments.com/kyoritsu/KM%202000.shtm

Cheers

[JetPlaneFlyer]

Bill,

3.5A is pretty low but i wonder how accurate matching the sound of the fan to the sound in the video is as a way of simulating actual flight power level?.. Would it not be more accurate just to look at the in flight position of the throttle stick on the Tx and simulate this on the ground (still not exact but i suspect better than 'matching noise')

Thing is the numbers dont stack up. You are using a 1500mAh battery and assuming it's delivering it's rated capacity then that will give 1.5A for an hour, or 3.5A for 25 minutes (1.5/3.5 x 60).. This means that you would expect to be able to fly for approaching 25 minutes if only 3.5A was being pulled from the battery. Your actual flight time is 8 minutes which indicates an average current draw of a little over 11A... A VERY large difference.



Steve

[babylon5]

Originally Posted by JetPlaneFlyer

Bill,

3.5A is pretty low but i wonder how accurate matching the sound of the fan to the sound in the video is as a way of simulating actual flight power level?.. Would it not be more accurate just to look at the in flight position of the throttle stick on the Tx and simulate this on the ground (still not exact but i suspect better than 'matching noise')

Thing is the numbers dont stack up. You are using a 1500mAh battery and assuming it's delivering it's rated capacity then that will give 1.5A for an hour, or 3.5A for 25 minutes (1.5/3.5 x 60).. This means that you would expect to be able to fly for approaching 25 minutes if only 3.5A was being pulled from the battery. Your actual flight time is 8 minutes which indicates an average current draw of a little over 11A... A VERY large difference.



Steve

Hi Steve, in flight the plane will be consuming less current when the aircraft is in flight depending on its airframe. It's quite difficult to gauge the actual current in flight without an on board monitoring systems. I had a feeling the flight time is not base on 100 percent full throttle all the way.
Correct me if I am wrong.

Cheers and take care

[JetPlaneFlyer]

Originally Posted by babylon5

Hi,quorneng , may i know how what type of ammeter and how you measure the current.

Standard ammeter has internal resistance that will result in much lower amps reading.

That's not really true.. A typical Wattmeter has an internal resistance that is so low it's similar to just a few inches of wire. The 'Watts-Up' for instance has a resistance of one thousanth on one ohm (0.001 ohm)... thats about the same resistance as 5" of 12AWG wire. At 3.5 Amps that would cause a volt drop of 0.0035V which is too liitle to even measure.

Bottom line - resistance from a wattmeter is completely insignificant.

Steve

[JetPlaneFlyer]

Originally Posted by babylon5

Hi Steve, in flight the plane will be consuming less current when the aircraft is in flight depending on its airframe. It's quite difficult to gauge the actual current in flight without an on board monitoring systems. I had a feeling the flight time is not base on 100 percent full throttle all the way.
Correct me if I am wrong.

Cheers and take care

According to Bill flight time of around 8-9 minutes was the max that could be achieved by flying reasonably gently and conserving power. If the battery was delivering it's rated 1500mAh then that MUST mean the average current draw in flight was around 11A.. very simple math as outlined in the original post.

Could be that the battery was bad?

Steev

[quorneng]

Given that the recording and playback mediums were the same in both cases and the human ear is pretty good at distinguishing variations in pitch I am confident this method is as accurate as my ability to judge, from the ground, what is sustained level flight at minimum power.
It also agrees with the throttle position - 6 clicks up from off.
As far as the duration is concerned it managed just under 10 minutes with the old duct and at the time I did think longer was possible.
The closer fitting duct has noticeably improved the low power performance so as soon as the weather allows I will indeed be looking for 20+ minutes with a new 1500mAh LiPo fitted.

[JetPlaneFlyer]

Looking forward to the next flight report..

[babylon5]

Originally Posted by JetPlaneFlyer

That's not really true.. A typical Wattmeter has an internal resistance that is so low it's similar to just a few inches of wire. The 'Watts-Up' for instance has a resistance of one thousanth on one ohm (0.001 ohm)... thats about the same resistance as 5" of 12AWG wire. At 3.5 Amps that would cause a volt drop of 0.0035V which is too liitle to even measure.

Bottom line - resistance from a wattmeter is completely insignificant.

Steve

Hi Steve,
I am afraid I have to disagree. Let me explain ...

For Standard ammeter you need and additional connector and wire harness to link between the battery and the ESC. Such additional connectors has its own internal resistance and its contact resistance will increase over time and usage and will add on to the ammeter internal resistance. Moreover, when battery is plug to such an ammeter , there is a momentary arcing between the conductors ,further aggravating and increasing the internal resistance .
As a result, I would never recommend this type of ammeter for electric flight. Its accuracies and consistencies are questionable when use for high current application and with high lipo cells count.

If you are into long term electric flight , its better to invest in a ammeter that does introduce any resistance or additional connectors & wiring into the electrical systems.
Moreover, some of this ammeter can read the rpm of the motor indirectly by clamping on any of the 3 phase wire and read off the frequencies
see attachment.
Method:
1) Determine the number of poles of your motor from data sheet
example 2 poles
2) Determine the pole factor=number of poles of motor/2poles
3) Clamp the meter to any of the 3 wires exiting from the motor.(See my previous posting and pictures)
4) Read the frequency
5) Rpm=(frequencyx60)/pole factor
Example#1
Align 430BL-3.55KV is 6 pole
Pole factor=6/2=3
readings=1431hz
rpm=1431x60/3=28620
Measure the DC current =23Amps
Example#2
Walkera motor is a 2 pole
Pole factor=1
readings=488hz
rpm=488x60=28980rpm


Its really a cool equipment.

Cheers

[babylon5]

Sorry this line should read as "If you are into long term electric flight , its better to invest in a ammeter that does not introduce any resistance or additional connectors & wiring into the electrical systems."

Cheers

[quorneng]

babylon5
What you say is correct (but not the arcing bit as I do not connect under load!) but are these losses significant?

With the motor on load, if you measure the battery voltage and then again just before the ESC you can, if you have accurate enough gear, detect the voltage drop caused by the extra wiring and the ammeter itself.
In my case I could not detect any difference to 3 significant figures so no more than 0.1% loss and that's plenty good enough for me!

[JetPlaneFlyer]

Originally Posted by babylon5

Hi Steve,
I am afraid I have to disagree. Let me explain ...

When it's plugged in it does introduce one extra pair of connectors that will have some tiny amount of resistance, that's true, but one properly made up connector wont make any measurable difference to the current or voltage, certainly no difference that would cause a "much lower amps reading"... And anyway you only have the ammeter plugged in for testing.. it's not introducing any extra connections into the normal operating circuit.

I've never observed any arcing when making and breaking the ammeter connection (dont see why it would if the ammeter is an open circuit) and anyway this is something that you might also get making and breaking the battery connection to the ESC and charger, and we all live with that every time we charge a battery.. A ammeter on the other hand is used only rarely.

Regarding the clamp on meter.. How would you measure DC current with that? The one you pictured looks like the type that can measure frequency only, so no way of measuring current. The larger ones that have a great big 'jaw' that loops round the wire can measure current but the cheaper types of these meters do AC only, so could not measure battery discharge current. The 'hall-effect' types that measure DC are pretty expensive, like $200 upward, or they were last time I checked. Personally I'd save $200 and live with plugging in a connector once in a while.


Steve

PS.. this is what a DC clamp type ammeter looks like (and costs): http://www.gettools.com/index.jsp?pa...e,Clamp.Meters ..ouch!



The big red jaws have to go round the cable.... they all work in a similar way.

[babylon5]

Hi how about this Kyoritsu kewmate 2000/2001? . The 2000 model up to DC 60amps and the 2001 up to 100amps .
I paid about and equivalent USD 50 5 years ago but price has gone up since the Yuan has risen and the USD dropping now is about USD 70-80 for the 2000 model.
Moreover for this model , the thongs is rather smaller and handy in tight area.

Cheers.

[babylon5]

Hi, you can purchase the Kyoritsu kewmate 200/2001 in the USA

Check this link http://www.expotechusa.com/Catalog_K...Multimeter.pdf

Here are the pros and con.

Pros=can measure both Dc and ESC timing frequencies. Small thongs handy in tight space. Cheaper than most ammeter. Does not introduce parasitic resistance to the loop circuit.

cons: limited resolution. The Dc current resolution up to 0.1Amps and zero centering sucky.

Note: I am not a promoter of Kyoritsu kew mate meter but I think it is quite cool equipment for e-flight application in spite of the cons.
There maybe other similar equipment but they come with a price tag.

cheers and hope this info is useful

[JetPlaneFlyer]

That's a great little multimeter and ideal for our purposes in many ways, I'd not seen one with small jaws like this, good find!.. However there are a few issues, some minor, some rather big.

• First it's not especially accurate having a bases accuracy of +/- 2%, so nowhere near the accuracy of the in-line type, I don't see this as a big deal as it's 'accurate enough' for our purposes.
  
• Capacity is limited. 60A for the model 2000 would not be enough for many medium sized models and even 100A for the 2011 might not be enough for the big or very powerful stuff. They do a 2012R version that goes to 120A but i cant find anywhere that sells it.
  
• The main and big issue is price, as I mentioned in my last post. For most peoples purposes the 2001 would be the model they needed to cover all their needs (up to 100A) and the prices I've seen are around £150 (UK pounds), which works out at over $200 US dollers.. which is a lot of money to have to pay to save the 'inconvenience' (for that is all it really is IMHO) of having to make and break one connector when you are checking your system.

It does look like a great little tool though and if it was available for what you paid I'd snap one up, it would be handy for all sorts of purposes.


Steve

[JetPlaneFlyer]

Ebay to the rescue.. Found one on eBay for half the regular list price: http://cgi.ebay.co.uk/Kewtech-Kyorit...0#ht_793wt_905

It's still three or four times more than an in-line ammeter though, so for now I'll just put up with plugging in my ammeter once in a while.

Steve

[babylon5]

from JPF
"I've never observed any arcing when making and breaking the ammeter connection (dont see why it would if the ammeter is an open circuit) and anyway this is something that you might also get making and breaking the battery connection to the ESC and charger, and we all live with that every time we charge a battery.. A ammeter on the other hand is used only rarely."

Babylon reply
The arcing will occur depending which connectors are plug last. If the battery side is plug last, arcing will occur at the battery connector. If the wattmeter or ammeter side is connected last , the connector attached to the wattmeter will arc.The arcing is very obvious with higher cells count and ESC will huge capacitor. Try 4cells and above and with the ESC will large capacitor , you will see the arcing.
You probably did not notice the arcing because of low cells count maybe 2cell or at most 3cells plus low power applications ESC, where the ESC has low built in capacitance .

Arcing occur because there is a potential difference between the ESC and the battery electrode due to the presence of the discharge state of the electrolytic capacitor at the ESC. (note when the capacitor is at a discharge state and at the instant of time when V is applied to the capacitor, it is a short circuit for a short while but enough to cause an arcing.)

There is a way to get around the arcing by adding and additional connector to the battery and also at the ESC side with a series dummy resistor of say a few hundred Ohms.

The trick is to plug the connector with the dummy resistor and wait for a few seconds before connecting to the primary or the main connectors so that it will bring the potential difference of both the battery connectors and the ESC main connector to the to the same potential as the battery. When this happen no arcing will occur when the primary connectors are finally engaged.

However, the downside to this modification ,is it is quite cumbersome in its application.
I am not sure anyone want to try this to preserve the connectors integrity.

Cheers