stiknrudder

THanks,

I'll try it with 450 and with 4 screws can switch to 480. I appreciate the input.

Rick

AlexinOz

Hi all,

Hope you're well!

I've found some great reading on this forum topic... and I've tried to put what I've learned into practice. Any chance someone can double-check my parts list for a park flyer I'm building?

I got this ARF kit cheap from a guy at my club ($20 AUD ... or about $14USD) and have decided to pull it out from storage and put it together now.

I can work out the servo's - but the battery/ESC combo has got me a bit challenged and I want to confirm if I have spec'd it out correctly before I hit the "buy now" button.

The wingspan is approx 90-100cm and it is made up of balsa for the wings and very thin ply for the fuselage. I estimate it to be about 500-550g (19oz or 1.2 pounds) for the plane plus servos, battery and receiver, and motor. (See photos that came on a CD with the kit attached below). It is about 220g without all the electronics.

The Motor?
I've decided I'd like to make it mildly aerobatic (I'm not putting any dihedral in the wing), so that comes to 130W per pound, so on my math I need to get a motor capable of 150W.

I found a Towerpro motor at HobbyCity, it is rated at 180W - would prefer it more powerful than I need (can always hold off on the throttle). This is the URL to it:
http://www.hobbycity.com/<wbr>hobbycity/store/uh_viewItem.<wbr>asp?idProduct=5112

I work out that I will need 13A to drive it to 150W (150W divided by 11.1V with 3 cell LiPos). This works well as this motor runs most efficiently around 15A apparently.

The ESC?
I picked one that has a bit of headway - the Motor is rated to 20A so I thought a 25A ESC will work fine. My batteries are rated to 20C plus burst capacity on the top (whatever that means).
http://www.hobbycity.com/hobbycity/s...eed_Controller

I've picked this because I think it gives me some safe headroom and the reviews are positive.

My batteries?
Now, I'd prefer to use my existing 3S1P lipo's (have 2x 2200mAh and 1x 1800mAh, rated at 20C plus burst on the top) rather than buy something new.

Am I in any danger of cooking the ESC with these? I am aware that they can provide much higher current than what the ESC is rated to but I'd prefer to have long flights hence why the higher mAh suits me well. Hoping this is OK.

The prop?
According to the motor specs I should pick up either an 8 x 3.8 prop or 8 x 6 prop. I would prefer thrust over speed, so will go with a "slow flyer" 8x3.8 prop. Found one here...
http://www.hobbycity.com/hobbycity/s...idProduct=7130

It would be greatly appreciated if you can take a look at my logic and confirm if I am on the right path!

Many thanks in advance!

Cheers,
Alex

AEAJR

Your logic and reasoning is very well stated. I like your selections. The only suggestions I have are that you get several props, they are cheap, and try them.

The capacity of the battery has no bearing on the ESC. The amperage the motor will pull is the determing factor so your batteries are fine as long as they are in the weight range you want.

If you wanted you could probably go with an 18 amp ESC but it only saves you 3 grams and $1, so stay with the 25.

Based on the user reports the 8X6 looks like the right prop. You could probably also try a 9X4.7 and even a 9X6, based on user reports.

If you have a wattmeter you can more safely experiment with props, but, based on user reports, these should be withing the capability of the motor. If you don't have a wattmeter, stay with the recommended props and see how they work.

Nice write up. Good job! Let us know how it works.

AlexinOz

Hi everyone,

Well I have finished putting the plane together and I gave it about 5 fifteen min flights this weekend.

I bought a mix of 8x3.6, 8x4 and 8.6 props, however because the details weren't clear on the web site only the 8x3.6 fits straight out of the box (others require drilling which I need a vertical drill for to get it exact).

I haven't got any measuring equipment for some solid figures but in a word, it flies very well, if not ever so slightly under powered.

This is interesting as the plane ended up weighing in at only 396g (ready to fly weight, LiPo's and all!) - I really over-estimated the final weight it would come in at. It will go at about 70 degree incline for about 7-10 seconds before wanting to back off which is more than fine given how small it is. Mild aerobatics aren't a problem for it either.

As I am using a 3S 1800mAh LiPo I think this adds considerable weight which would certainly hold it back from going vertical too. A 2S might be the better choice. That said the "big" LiPo I'm using gives me 15 minutes flight time at about half to 2/3rds throttle continually and I was still around the 3.78V-3.80V per cell on landing, battery cool too.

I suspect changing to either the 8x4 or 8x6 props would give me more speed and possibly more vertical performance... is that a fair assumption?

Thanks again for your help, much appreciated and I can definitely call this project a success!

Cheers,
Alex

gittarpikk

Here is my thread on the Brushless system I have on a Gentle Lady 2 meter sailplane

http://www.wattflyer.com/forums/showthread.php?t=44648

And here are links to the Brushed components I am comparing..


http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWK50

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVY74

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXZ996

I finally figured out how to program the ESC (which allows me to program only three variables..cell, brake and protection)

I still get the 1/2 throttle shut down on all batteries , no matter what number of cells I am running, (ie 6,7,8) and I ran the combo prop.

When I hook the same batteries to the brushed /geared folding prop 12-8 , I get a LOT ot power....its really moving a LOT of air. I put the prop on the brushless,and still get the 1/2 throttle shut down and nowhere near the power (I realise that is not a good prop for the brushless but the combo prop still kicks out and will not produce much power)

The esc is only an 8 amp for the brushed motor....and the esc for the brushless is 18. Yes, when I run the 280/geared on 7 cells, 1200MAH pack, and run WOT, it will get pretty warm quickly...but its is really producing a lot of thrust.The duration is fairly good too if I am using the 1200 MAH pack.

It I go to a 9x5 (what everyone seems to reccommend for the brushless combo---saying the motor gets too warm on the combo 10-4.7 prop), will it stop this 1/2 throttle shutdown.

The feedback at Hobby K raves on how good this motor is and what kind of power it wil produce.... but at this time I can only see a cheapo brushed/geared motor blowing its "doors" in...

Ok you motor gurus, see if you can figure this one out..
Thanks in advance

gittarpikk

I had zipped through the included setup paper and it didnt seem to work so I set about researching all forums and the web and tried everything I could find.. Still no programming. So I went back to the pamphlet and deciphered that when you start this one, do it on full throttle.
There has obviously been a change in the number and types of settings you can make manually.
I can only set three which is different form most of the posts about this ESC
Cell type
brake
voltage protect

When you start at full throttle and hook batt to esc, you get one loud tone and then a start of a sequence
b,b
bb,bb
bbb,bbb
that represents
cell type
brake
voltage protect
trick here is when you here the beep for the item you wish to change ...then move stick to 1/2 throttle
you will then hear a soft tone...then a few more...then nothing
move the stick to low and you will hear a few more tones..
your ready to go

I figured out the reason for the 1/2 throttle shutdown....

I copied the lines below from another post

Now the $64,000 question I had a lot of trouble on was why it was cutting off at only 1/2 throttle...no matter what pack I was using
Well that answer , I finally found was simple and is what most people say about the combo I bought. The 10X4.5 prop is usely, THROW IT AWAY
When I put on a 9X5 the motor was able to run wide open and really produced thrust.!! Anything over 9" prop is to large and may work (probably due to anomalies in production) for some or maybe even for a short while, but people have smoked this motor and esc and (my example) will not even run right by using the 10" prop.
So if you learn only one thing here in this thread let it be this
THROW AWAY THE 10 " PROP!!!
You'll be glad you did.

Another update.... motor still kicks out on the 10x4.7 that came with the combo....even after .5 inch was cut off from ends of prop...reshaped and rebalanced...

Which leads me to believe the motor or esc is either faulty of it cuts off prematurely on voltage drop at startup. If I put an old wood prop (old Testors approx 9x3) on it, it screams and does not cut off . Is that all this motor will swing?!?!.Why are others getting good results even on the 10x4.7 that came with the combo?

ByxnPlanes

Hey, I bought some brushless/lipo gear before I really knew what I was looking for (only familiar with brushed/Nimh), and I just want to know if I can still make my setup work. I have a 3000kv, 35gram outrunner from Hextronic, and a 3s, 20c, 1500mAh lipo, and 40-50A brushless esc. I have a parkzone Spitfire and Mustang that I was planning to upgrade with this gear. I was informed that this motor my draw to much to have any substantial flight time (maybe should have gone for the 2200mAh lipo). Also wondering if 3000kv is super over kill for this kind of bird. ANY info would be greatly appreciated!

AEAJR

Whenever asking about a specific motor or ESC you really need to provide all the specs for the motor or better would be a link to the information.

Without the MFG specs we are only guessing as to what the max amp capability is of the motor. Usually the MFG will provide prop recommendations and projected amp draws for each prop. That is where you need to look.

Without knowing what prop you will be using there is no way to project the amp draw. Will you be using a gear box?

Is 3000Kv over kill? Not a valid question. The question you want to ask is what kV motor do I want to get to match up with a given prop/battery combination.

I suggest you go back and reread the first post.

I have no idea of the weight of your plane so I can't project performance either.

If you like you can use Webocalc to do some projections based on the inputs it requests. It will suggest prop sizes to match to desired pitch speeds and amp draws.
http://flbeagle.rchomepage.com/softw..._imperial.html

Using some estimates I put in, 20 oz, 40" wing, 90 MPH pitch speed and 25 amp target it pops out a 5.5X4.5 recommendation for a direct drive prop producing 23 oz of thrust at 270 watts.

I have no idea if that motor can handle that many amps.

Sorry I can't be more helpful.

ByxnPlanes

Thanks AEAJR. I will do some research about what I have purchased and post again. Thank you for the links.

mred

This is only a guess so far, because you didn't give all the information, but a 3,000KV motor is meant more for a Chopper then a war bird. I would say going to something with a 900KV to about a 1500KV motor and I think around a 1000KV motor would be much better. A 3000KV motor is going to be spinning a small prop and not give as much thrust unless you have a gear box for it. The higher the KV rating the smaller the prop is going to be. For a war bird, you are looking for thrust from a big prop and you just can't put a big prop on this motor without going over the amp rating of the motor. A 35g motor is going to be pretty small, so I am guessing that the prop you will need to keep this motor in it proper amp range is going to be really small. Maybe a 3" prop or so and that just will not give you enough thrust to fly the plane you have. We need more information on the plane and maybe we can give you a good guess what kind of motor it will need, but I think this is the wrong motor for what you are trying to do. The 2200mah battery will not help you with the amp draw, only duration. The 1500mah battery may give you enough duration if you had the right motor to go with this plane. Give us at least the wing span and total weight with gear and maybe we can give you a better answer for your motor.

Ed

ByxnPlanes

Thanks for helpin this Nube. Flying weight is around 26 oz. Wing area is 335in sqr. Span=39in. I have motor data based on 7.4V supply (2 cell?). With a 7X4 prop, pulls 21 Amps at 8800rpm giving 380 grams of thrust (13.4 oz). With a 8X3.8 prop it pulls 22A at 8200rpm. giving 430 grams of thrust (15.2 oz). As I say, no data with 11.1V supply. Thanks again for the help.

AEAJR

That would suggest to me that this motor is not intended to be run on a 3 cell pack.

Will know more when you post link to the motor info.

Experienced Pile it

Hello.
For my first post on this great forum I have a couple questions, if you please.

I'm preparing to assemble my first electric model. My little boy is keenly interested in things that fly so we have decided to give him an airplane for Christmas this winter. I've decided on the Maxford USA Butterfly for the airframe and am going by recommendations for ESC and motor from their website. I've been reading up last couple weeks on lipo batteries, power plant combinations, etc, but want to check with experienced folks to make sure.

Here's what I've decided so far:

Tower Pro 2408-21 Brushless outrunner

18 amp ESC

Battery 1050 mah 2s 20C.


Hobby King's website claims the motor is 1750kv but Maxford's site states 1400 rpm/V. (???)

Maxford site states 2s or 3s packs and suggests 9x6 prop or 10x4.7 Should that be 9x6 with the 2s pack and 10x4.7 with the 3s pack?

I was planning on 3s lipo's but they're out of stock right now. The link above is for a 2s, 1050 mah, 20C pack. Reviews I've read say the plane flies "loftier" with a lighter weight pack but the wind is a factor where we live so I thought I'd go for the heavier pack (same C and mah rating on both packs) so it'd fly better in the breeze and (I'm guessing) with more of a scale-like appearance. Oh well, 2s packs might be better because I'll be able to charge simultaniously.

Anyway, my question is: Should I use the 9x6 or 10x4.7? Or maybe something different still. (??? 7x5, 8x6 ???)

The prop I'm planning on is the imitation APC knock-off


I'm not interested in a lot of speed with this aircraft, longevity of motor, esc and batteries is more important... and nothing over-heating. We just need casual and relaxing flying and something to train my little guy. He'll be 3 this winter but I believe I can have him ready for the buddy box by fall 2010. This will be my first electric plane and my first 3 channel. When we want speed and performance we can fire up one of my old nitro planes but for now I like the idea of quiet flight. I don't want to frighten the little guy with the noise, I want an enjoyable experience for him right from the start. Plus I'll use this plane to teach my wife and some friends of ours to fly.

Please, when you have a moment, take a look at what I have so far and let me know which prop best fits our needs. Also, if I've missed any of the necessary info to make an educated suggestion, let me know and I'll post it for you and let me know if I've made any poor choices thus far. The airframe should weigh in the 17 to 17.5 ounce range when ready to fly.

Thank you very much and God bless!

ps. I tried to post this but the website kicked it out stating "you cannot post links until your post count has exceeded 3 posts." I had links in this post but I reckon I'll have to put those up later if you need them.
Thanks again.

Sky Sharkster

Hello Experienced Pile it, Welcome to Wattflyer!
To answer your question about the props/battery size, the answer is "Just the opposite".
The larger the number of cells (which is greater input voltage) the SMALLER the prop.
And the reason is clear if you think of it this way; More cells = more volts.
The greater the input voltage, the faster the motor wants to turn. But, nothing's free, everything mechanical has a cost. Leaving the same prop on a given motor while increasing the voltage means the motor will try to produce more RPM with the same amount of drag or resistance. Can't do both, one has to give. It usually comes in the form of white smoke. Which is what occurs when a battery or ESC (or both!) is overloaded.
Big prop, little volts.
Little props, Big volts.
Here's the link to your motor;
http://www.hobbycity.com/hobbycity/s...idProduct=4321
The rule of not adding links for the first few posts is to stop the ever-present spammers. It's the world we live in, a safeguard.
The rest of your suggested parts look good for the application, you might try a 3S LiPo and smaller props when they're in stock.
Here's a free online "Motor Calc". They don't have your motor but you should be able to find a similar Kv and size motor to compare prop and voltage specs. It's educational and fun.
http://brantuas.com/ezcalc/dma1.asp
Good Luck!
Ron

AEAJR

No problem about the first post not allowing links. But in the future, we always need the links otherwise you require us to hunt around to find all the items you ask about. And when asking about specific products it is often helpful to post more info than you provided, though if you post the link we can find it easily.

I don't know the plane you are looking at so I can't tell you if this motor is right for that plane. Again, when possible, post information about the plane. Don't assume any of us know anytihng aout the plane. I often see posts that say, "I have a J3 Cub, I need to know...." Well there must be 30 J3 cubs out there, some 2 oz and some 25 pounds. It can take 5-10 posts to finally find out what the guy has.

Just a posting tip. More info is always better.


I searched the Hobby King site and found this reference to Towerproo 2408-21:
http://www.hobbyking.com/hobbycity/s...idProduct=4321

TP 2408-21
The most widely used towerpro motor available today. the 2408-21T is often used in GWS upgrades. Paired with just an 18A besc, this motor is an excellent and cheap way to upgrade small planes to brushless.
An RD1047, RD9070 or 8040 size propeller are the best choice, with the RD9070 and 8040 giving the best thrust and amp draw balance.

For 2-3 Li-Poly Cells (7.2-12.6V)
31 mm diameter x 62 mm length
Maximum current: 13A
Weight: 50.2 grams / 1.77 oz
Comes with stick mount plastic frame
Firewall mount capable
Comes with two prop nuts and one washer
3mm shaft diameter
10mm x 10mm stick mount
Kv: 1750
9 Stator Poles, 12 Magnets

<NOBR>Configuration: </NOBR>	<NOBR>Propeller: </NOBR>	<NOBR>Volts: </NOBR>	<NOBR>Amps: </NOBR>	<NOBR>Thrust: </NOBR>
<NOBR>Direct Drive </NOBR>	<NOBR>8040 </NOBR>	<NOBR>7.4V </NOBR>	<NOBR>8.2A </NOBR>	<NOBR>12.0 oz / 342.86 grams </NOBR>
<NOBR>Direct Drive </NOBR>	<NOBR>8040 </NOBR>	<NOBR>8.4V </NOBR>	<NOBR>8.6A </NOBR>	<NOBR>13.8 oz / 394.29 grams </NOBR>
<NOBR>Direct Drive </NOBR>	<NOBR>8040 </NOBR>	<NOBR>9.6V </NOBR>	<NOBR>11.1A </NOBR>	<NOBR>17.0 oz / 485.71 grams </NOBR>
<NOBR>Direct Drive </NOBR>	<NOBR>8040 </NOBR>	<NOBR>11.1V </NOBR>	<NOBR>13.1A </NOBR>	<NOBR>21.0 oz / 600 grams </NOBR>

I also found this discussion by the owners of this motor
http://www.hobbyking.com/hobbycity/s...wer_Search.asp#

If you are planning on using a 3 cell lipo I would use the 8X4 prop they tested.

Typically the smallest prop listed goes with the highest voltage pack. The largest prop goes with the lowest voltage pack.


If you read the customer comments they all seem to be using 7 or 8" props and some are reporting over 16 amps which is well over the rated capacity of the motor.

Note that HobbyKing has some good stuff at good prices, but if it comes in bad they will ask you to ship it back for replacement. I had this problem. The return shipping was more than the value of the product I purchased. I bought the replacement elsewhere.

On things like motors and ESC, I suggest you buy two. If they both come in good, then you have a set-up for the next plane, but if one comes in bad, it is often cheaper to throw it away than ask for warranty replacement.


So be careful and know what you are buying. I don't buy from Hobby King anymore.

Experienced Pile it

post number 2

Experienced Pile it

post number 3

Experienced Pile it

Thanks for the info, guys.
Yep, that's the motor.

I wanted to provide links for each item, should have thought of "dead" postinig sooner

Anyway, here goes.

ESC
http://www.hobbycity.com/hobbycity/s...idProduct=6457

Reviews sound positive. I think this'll do for a first plane. Can always buy a good Castle creations later and learn how to program them, etc.

Same goes for the charger. So long as it balances properly it should work for now. I can get more technical later.
http://www.hobbycity.com/hobbycity/s...idProduct=2055

Here's the 2 battery sizes.
2s 1050 mah 20C
http://www.hobbycity.com/hobbycity/s...idProduct=7307
3s 1050 mah 20C
http://www.hobbycity.com/hobbycity/s...idProduct=7309

If they are back in stock when I'm ready to order I'll probably go with the 3s and the 8x4 prop. If not the 2s and 9x6.
That sound good?

Thanks for the tip on the return items. I suspected as much. Already planned on buying an extra servo in case of a DOA, maybe I'll do the same for motor and ESC. They're cheap enough, might as well. I already planned on 2 batteries.

Here's the prop.
http://www.hobbycity.com/hobbycity/s...idProduct=5439

I've got a box full of props for 40 to 50 size nitro burners but I'm guessing they have too much mass for electric flight. Is there a difference in standard "electric flight" props and those marked "slow fly"? Maybe I should be looking at a different prop. (???)

Here's the airframe.
http://www.google.com/url?q=http://w...CocsOWm_74ruLg
We already ordered that and it should be arriving soon. Course, being a Christmas present I'll have to stash it away, but I plan on getting the electronic goodies all assembled and tested as soon as they arrive in the event of a DOA that needs replacing. I'll just order one battery charger but think I'll get 2 motors and probably 2 esc's also.

Sky Sharkster. I'll play around with that caluclator. Looks like fun and stuff I'll want to eventually learn more about anyway. I'm in no hurry but wanted to get stuff ordered well in advance before Christmas shopping season starts.

Also getting extenders for charging in an old ammo box with sand in the bottom.
http://www.hobbycity.com/hobbycity/s...idProduct=8873
Hope it's the right one They also have one for 3s batteries.

Prop saver seems like a good idea.
http://www.hobbycity.com/hobbycity/s...idProduct=3738

There's a variety of other little stuff I have on the list from Hobby King. I'll probably order just this once to get those goodies for such a reasonable price and stick with suppliers a little closer to home in the future. Wish my local hobby shop was still open. I always bought stuff there even when it costed more because I really liked the convenience and appreciated the on hand expertise. Oh well.... life goes on.

Thanks again you guys, for the tips and help. Greatly appreciated.


How does one add a signature line so it posts automatically with every post?

Don't fret, just fly. The crashing part comes later.

AEAJR

That motor should have Plenty of power for that plane. will probably climb straight up on a 3 cell and an 8X4.

Enjoy!

Sky Sharkster

Hello Experienced Pile It,
Now that you have the full user options, click on (highlight) your user name on one of these posts.
You should get a drop-down-menu. At the top is "View Public Profile"
Click that on. Next you will go to your profile page.
Click on "Edit User Profile"
New Page, a bunch of boxes. Click on "Custom User Title" and type in your sig.
You now go to a right-side box, "Display Signature?" Click "Yes".
That should do it, takes a couple of seconds to refresh.
Ron

PaperAirplane

Is it ok if you battery has a higher mAH rating than your motor requires?
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mred

The only thing that will do is add a little more weight to the plane and will allow you to fly longer. If you can handle the extra weight, then no problem - you just get longer flights.

Ed

PaperAirplane

One more question.
Do you know anyplace that you can buy discounted motors from brands like Electrifly or Hacker?
I am starting out and know what i am looking for but dont know where to find good priced good-quality gear.

kyleservicetech

I've only purchased Hacker motors due to their quality and performance. The bad news is, they don't get discounted very much. Our Local Hobby Shop in Milwaukee WI area has decent prices, but they only discount a dollar or three.

Nice part about it, all of my Hacker motors ranging from an A30, two A40 class, and two A50 class are running as good as when they were new two years ago. And, I'm pushing them at their rated maximum current repeatedly, and they only get slightly warm after a flight.

And, as for ESC's only used Castle Creations units. And, also used the uBEC's (Switching receiver power supply allows running your radio directly from your motor battery supply, up to something like 25 volts) from both Castle Creations and Common Sense. Both worked well on my 2.4 Ghz Spektrum radios.

mred

You can try E-Bay. Once in awhile you can find a good deal on a good motor. Tower also has theirs on sale once in awhile, but if you want top brand motors, you are going to pay for them at just about full price, unless you find a used one on E-Bay or some place like that. You can find AXI motors on sale from Hobby Lobby once in awhile too, but you are going to be waiting for a long time trying to find a deal on brand name motors. I got a really good buy from them on an AXI once, but that one just happened to come up at the right time. Hacker I have never seen on sale anywhere. Taking 1 or 2 dollars off is not what I consider a sale. You could try advertising for a used motor and may find one that way, but chances are you will not find any GOOD deals on the motor you are looking for.

Ed