Dear vinay,
pl pardon me. i am unable to recollect our meeting. pl give some clue.

According to me what you have given below is far more than just theory it is very very practical and true. You have taken so much pain and troubles to go to such details in depth. congrats.
coming to the point. ( pl excuse me, if there are few mistakes, did not spend enough time reading this thread)

1. I went thru quickly the RCGROUPS thread that pankaj has given.
2. This says an auw of 14 OZ aroud 400 grams max.
3. At the begining of the thread Pankaj says it is 1 to 1.2 KG
4. This is too gross a discrepancy. So this plane  show different flying characteristics than what is designed.
5. The gear that you have selected is Good if the plane is in the 15-20 Oz range.
6. The motor could be even blue wonder 1300 KV to make things bit lighter.

in my opinion just like  Wing span/ Chrd dimns etc. weight of the palne is also an importnat (most imp?) spec. to be respected to get the designed results.
ashta

Quote from: vinay on November 15, 2009, 07:21:24 PM

Everybody Please COMMENT!!!
Comments are very useful for beginners like myself

Ashta Sir, Expecting your comments also, As you are still the only one I have met in person who has built so many planes from Scratch.

 

Astha/Vinay,

At the start of the thread I had mentioned my assumptions for the weight. I started with a 3S1P 3-5AH rating and then back calculated from there to get a assumption on the weight. Yes, foam is light, but the rest is not, and glue also adds weight.  I started also with a 130-140% model of Scott's design. So a couple of iterations made me realize that the AUW would be 1000gm+

The motor is 1050Kv. The model is http://hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=2100


Whether this will ultimately takeoff? I am hoping it does so else it will be back to the drawing board.

In the meantime there is a problem.....

I have purchase DX6i the unit came with AR6200 receiver. The manual says I need to bind the receiver to the Tx, but the diagram is something that I cannot understand. The diagram has a battery connected to a switch with a charge plug where the bind plug is inserted, but I do not have a switch, I have a ESC with BEC. So the direction given does not match with an electric setup with ESC. So how does one bind the RX?

Pankaj

OK, bound the Rx to the Tx and here's how
http://www.rcindia.org/beginners-zone/connecting-servo-to-receiver-and-binding/msg8982/#msg8982

dear pankaj,
any way it is a great build and very nice looking plane. All the best for your maiden.
Many times i have saved my bulids by hand launching to tall grass with every thing loaded powered on but zero throttle to test the glide. May be you can try that.
I do not know about Ar6200.

best regards
ashta

All Electrical Gurus

Need help in understanding the LiPO.

In one of the threads, Anwar suggested that I fly the model for about 5 mins and measure the charge that goes in to determine the flying time available. While I have not maidened my model yet, what I did was to wire up the motor and try it out.

The following thing I observed.
If I suddenly apply full throttle in one jerk, the motor produces a high screech and turns in a considerable slow speed and keeps jerking. However, there is no problem if I go from min to max in about 4-5 sec. Is there a problem with the motor?

I had tied the model to a chair (normal wodden dining chair, weighing about 7-8ks) and started applying throttle, at full throttle, the motor began to pull the chair along the floor (very slowly). does the thrust seem good enough to take off a model about 1.1 - 1.2Kg?

I have a fully charged 3C1P at 12.59V as shown by the charger, I run the motor at about half the throttle for 4 mins. The voltage drops to about 11.8 and then when I charge it, the charge that went in was 1666. So how much wattage did my motor draw?


The more I get closer to maiden, the more doubt keep coming in my mind...... First model after such a long time, first RC model, first time handling electric ...... excited and stressed out at the same time...

Have you set up the ESC for max and Min throttle ?

Some ESC's require you to set the Max and Min throttle  position before the Motor is ready for action  should be there in the instructions

When you give a burst what you say should not happen  and the possible explanation is  the current draw is very very high  can't say for sure .

Proping down might be required .



Sai

Quote from: PankajC on November 20, 2009, 12:23:33 PM
If I suddenly apply full throttle in one jerk, the motor produces a high screech and turns in a considerable slow speed and keeps jerking. However, there is no problem if I go from min to max in about 4-5 sec. Is there a problem with the motor?

It is possible that the ESC is preventing an overload.  Your setup may be borderline in terms of wattage. Try a smaller prop, if you have one, as a quick test.

Quote from: PankajC on November 20, 2009, 12:23:33 PM
I had tied the model to a chair (normal wodden dining chair, weighing about 7-8ks) and started applying throttle, at full throttle, the motor began to pull the chair along the floor (very slowly). does the thrust seem good enough to take off a model about 1.1 - 1.2Kg?

That seems to be pretty good thrust.

Quote from: PankajC on November 20, 2009, 12:23:33 PM
I have a fully charged 3C1P at 12.59V as shown by the charger, I run the motor at about half the throttle for 4 mins. The voltage drops to about 11.8 and then when I charge it, the charge that went in was 1666. So how much wattage did my motor draw?

The more I get closer to maiden, the more doubt keep coming in my mind...... First model after such a long time, first RC model, first time handling electric ...... excited and stressed out at the same time...

Hmm... My suggestion was meant to help determine the safe maximum flying time, and had little to do with wattage (at least I did not intend it that way).  If you can specify the size of your battery (in mah), you can now determine how long you can safely fly. Remember that it is an approximation, as the duration depends on your flying style.  You will get better values if you did a regular flight and then checked the charge that was put back into the battery.

Good luck with your maiden 

As per spec this motor can take with 3 cell even a 12X8 prop. What prop are u using? if it is smaller, that may not be the problem.
Also look for proper connection, Gold bullet connectors 3 wires, and battery connection Deans. Any loose conact can show up the problem.
I always measure current with different props and ensure with in safe limits on any new electric plane.
In any case it may be a good idea to have an expreienced flier do the maiden for you.

Wishing you good luck
ashta

Ashta,

If Pankaj is using 11X7 Prop as mentioned in the Previous post then he is getting approximately 1.2 KG of Static Thrust (if run at banglore's altitude.) which is pretty good for the Plane he has designed. Since he has built the plane like a TANK with all the reinforcements, I think it should hold on 

ALSO,
Since the plane has a semi symmetrical aerofoil, what should be the Thrust to weight ratio for a trainer? I read somewhere that the thrust should be atleast 2/3 the weight of the plane for a trainer, Correct me if Iam wrong.

Also is it possible for the Thrust of 1.2KG to pull a 8 KG Chair?

Pankaj,
When I measured the Wing span on the monitor with a scale, I noted that the left wing was longer than the right? Is that true, or probably a photography angle mistake?

Battery load....

I programmed the ESC for high voltage threshold, and the cut off (motor speed) to 'cut off'. Then switched on the UP timer on the Rx for timing.

At full throttle, the 3S1P 3000mAH Lipo runs for 4 1/2 mins. The motor gets real hot, but one can touch it. The battery is warm, the esc is around room temperature. BTW kept the ESC outside the model to allow the battery to move forward.

After, the motor cuts off, I put it on charge after a gap of 10 mins. The voltage shows 10.8 with individual battery packs around 3.6 and 3.59

Pankaj

Motor Screeching .... seems to be a timing issue.

by default, the ESC came with LOW timing. the ESC instruction said, change to medium for 6 or higher poles and for better efficiency, change the timing to High. I just changed the timining to High and tried the motor.

When I quickly give the max throttle, there is a slight delay before the motor responds, but there is no screeching noise. I have not run the motor for full battery load, but tried this around 5 times - going from 0% to 100% and back to 0% on the throttle. Everytime the motor responded with a slight delay, but no noise....

I guess, the problem was of timing.

Pankaj

Yup, the problem is due to timings, I have read in many forums that increasing the timings will solve problems on higher wattage motor. I wanted to suggest this earlier but since Iam a baby in this field I didnt want to suggest something wrong and burn up you ESC motor

Also Try keeping the ESC in the normal start mode, rather than soft start. This may solve your other problem of delayed starting, If the problem still exists then there may be a problem with compatibility with ESC and motor?   Well not sure. Are you using Turnigy plush 40A ESC?

Also High timings are used to get more power to the motor, but it will reduce the efficiency, and will heat up the motor,

Its necessary to keep the timings as low as possible the motor can take without screeching for higher efficiency.

Managed to fry atleast something before maiden

http://www.rcindia.org/beginners-zone/fried-motor/msg9174/?topicseen#msg9174

Oops

I was going to write that if timing change alone fixed the issue, that would still indicate that you have a border-line power system. 

OK, in case I have a border line power system, how do I figure it out? Any indication (other than a fried motor)? What solves - reduce blade dia or pitch or what?

Things getting too hot and the ESC warning you by cutting off are good indications.

Reducing pitch or dia are both helpful.

vinay/pankaj,
1. Sorry to hear that the motor is burned.
2. But it does not matter. it is very easy to rewind the motor. make this opportunity to learn that.
if interseted pl read thru ( may be u hve seen this already)
You can normally finish rewinding it in 30 mins.
3. Some how the whole system is taking toomuch current for sure. Tetsing with out using an ammeter is very risky. Another thing i do is to use bench power supply 12V which can give only 3- 4 amps so that every thing is safe. When u use a large capacity battery, there is no current limit.
4. 75 W per pound should be good enough to get it air born.
5. to pull an 8KG chair, 1.2 kg thrust may be enough. I think that it depends on the friction. For example if the chair has wheels!/ it is on smmoth surface etc.
so one can use a spring weighing m/c and tie one end to the chair and pull. Find out what is the force required.

Pankaj, you can call me 9448073127 if u need any help in rewinding the motor.

ashta

Quote from: vinay on November 21, 2009, 07:37:36 PM
Ashta,

If Pankaj is using 11X7 Prop as mentioned in the Previous post then he is getting approximately 1.2 KG of Static Thrust (if run at banglore's altitude.) which is pretty good for the Plane he has designed. Since he has built the plane like a TANK with all the reinforcements, I think it should hold on 

ALSO,
Since the plane has a semi symmetrical aerofoil, what should be the Thrust to weight ratio for a trainer? I read somewhere that the thrust should be atleast 2/3 the weight of the plane for a trainer, Correct me if Iam wrong.

Also is it possible for the Thrust of 1.2KG to pull a 8 KG Chair?

Pankaj,
When I measured the Wing span on the monitor with a scale, I noted that the left wing was longer than the right? Is that true, or probably a photography angle mistake?

dear pankaj,
thanks for talking to me.
From what you said and from the photo of the motor that you have shown, one cannot conclude that the Motor is burned.
So do not dismantle it unless confirmed.
For confirmation u need one more motor and an esc. pl take help from Delhi, fliers.
pl check the motor and the esc seperatley and confrim which one has gone bad.
you need only about a max of 200W to take ur plane airbrne.

best regards
ashta

Many thanks Ashta, cleared a lot of doubt. Will be much more careful henceforth.
Actually kicking myself in the butt..... I had envisaged that I would end up making mistake - so had ordered 2 lipo, 2 esc, but got only 1 motor...

Anyways ordered one from Sai 2820/6 with a smaller prop, should be good enough replacement. and also would keep the weight same.

Pankaj

Quote from: Ashta on November 24, 2009, 05:27:01 PM
dear pankaj,

you need only about a max of 200W to take ur plane airbrne.

best regards
ashta

Pankaj ,
2820/6  is a 555 watts  and weighs 130 gms 2217 is around 300 watts weighing 70 gms  this motor is adequate power for my multiplex easy cub.

I will be shipping tomorrow think it over .
Rgds
Sai

I am not sure... reason is that my earlier motor weighs 135gms and with this weight, the plane was balancing around 25-30% mark - with the battery right up in front. If I takeout about 60gm of weight I think I would either have to redo the tail part or add extra weight to the nose.

Since redoing the tail part seems cumbersome at this moment, I thought that if I am adding extra weight might as well be productive - just in case I require and hence my decision to opt for 2820 when 70gm motor could have done..

So do you agree? if not then I shall change the order.

Quote from: PankajC on November 24, 2009, 06:21:50 PM
Many thanks Ashta, cleared a lot of doubt. Will be much more careful henceforth.
Actually kicking myself in the butt..... I had envisaged that I would end up making mistake - so had ordered 2 lipo, 2 esc, but got only 1 motor...

Anyways ordered one from Sai 2820/6 with a smaller prop, should be good enough replacement. and also would keep the weight same.

Pankaj

dear pankaj,
i got the following spec for the motor from the net.
Pl note 37A @60seconds.

Be exremely carefull, while doing static test.

al the best to u

ashta


"
For sport and aerobatic models weighing 2-6 lbs. The XTRM 2820/06 is a 1000 KV Brushless Outrunner with a current capacity of 37 amps @ 60 seconds. A maximum efficiency of 82%, a no load current @ 10vdc of 2 amps and an internal resistance of 59 Mohms. This outrunner has a 4mm shaft and is designed to run on 8-14 NiCad/NiMH cells or 3-5 LiPo cells. Includes Radial Mount, 4mm Collet type prop adapter and 3.5mm Gold Plated Bullet Connectors. This motor weighs 5.1 oz. and the dimensions are 35 x 45mm.

Recommended Prop:

11x6 on 3 cells
13x6 APC e on 3 cells = 69 oz. thrust
10x5 on 4 cells

Recommended Model Weight:

1000 - 2500 grams (35 - 88 oz.)

Recommended ESC:

XTRM 50A

Yes Same specs as the Manufacturer in China is the same Xtrm is another brand name like BP, Suppo , Grayson etc
http://hangitrc-estore.webasyst.net/shop/category/brushless-combos/

Sai

Astha,
I do not plan to load more than 10x5 prop on 3S1P so I guess, the current would be lot less and so would the wattage....

While we are waiting for the motor to arrive, maybe you could start another thread on motor repair

Pankaj

Maiden Unsuccessful.

I did not know whether hand launching could have been done, so I tried ground take off - maybe the surface was uneven or what I did not understand, but the moment the model gathered speed, it started wobbling left-right and then it lifted only to sharply turn left and crash / cartwheel ....

awaiting suggestions on what all could be wrong.