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Motor choice for 16" FW190

Old 02-10-2006, 11:35 PM
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Default Motor choice for 16" FW190

You guessed it, I'm thinking about building a Guillow FW190. I have a Micro Joule receiver and servos, but no ESC, motor or batteries yet.
Cirrus makes a brushed ESC, but my limited understanding of li-poly batteries and brushed motors is that they don't match very well. Trying to keep weight down, I would prefer to use a single cell lipo (or two cells if necessary)
On the other hand, Cirrus does not make a brushless ESC and uses very small connectors, which I'm told are not the easiest to solder properly.

Anyone been down this road before and care to point me in the right direction?

Antonio
Old 02-11-2006, 01:51 AM
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Default RE: Motor choice for 16" FW190

hi Antonio,

the motor you'll need will depend on the weight of the completed plane, in its ready to fly form (batt included). the general rule of thumb is your thrust should be at least half of what the planes total weight is. i.e. if the plane weighs 40g, the motor should be able to put out at least 20 grams of the thrust. so really, you'll probably want to figure out how much you think the plane will weigh before you decide on the motor size and lipo to match it.

lipo batteries will work just fine for a brushed motor, but you'll need to figure out how many amps the motor will draw at full throttle.

even with the MJ equipment, you should be able to get away with a geared N20, and if you're wanting to stay with single cell opperation, go with the N20-ULV. you can get the geared setup here: http://www.bsdmicrorc.com/productDet...67&catID=10005

i'm not sure how many amps that pulls, maybe 1.5, so i'd go at least with a 250mah cell. but, do a little looking around online and find your best options for what will suit your needs.

nick
Old 02-11-2006, 12:15 PM
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Default RE: Motor choice for 16" FW190

Thanks Nick. I'm looking around, but my head's spinning (awful pun, I know) there is so much information to process!

From what I've read, looks like some have had good luck keeping these under 3oz ready to fly. My 109 weighs under 46grams (what, 1.6oz), but with a ton of paint, the decals, etc. On the 190, I would start off with tissue and minimal dope, and work my way up.

More questions:

+ wing load. The wing on this thing is 266cm/sq, or 41"/sq. Anyone know of a good ressource to help me figure out what the max/best load for the wing is? I am no engineer, let's leave it at that!

+ ailerons. I was debating whether to cut the ailerons into the wing, or leave the wing in one piece and add external ailerons (which ties into wing load, since I could increase the wing area)
Old 02-11-2006, 01:15 PM
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Default RE: Motor choice for 16" FW190

i know what you mean about information overload. there's lots of differant setups you could go with. with 41sq in of wing area, you'll want to keep the weight as low as possible. for all my micro planes, i've always just kept in mind that 1sq in of wing area for every 1 gram of weight will make for a faster plane. doubling that will slow it down well, tripple it for a nice floater. tissue and minimal dope should help keep the weight down nicely.

not sure about the ailerons. added external ailerons may give you a bit more wing area, but it'll take away from the scale look of the plane. either way should work just fine though, i guess it depends on how scale looking you want to keep it.

even if your completed weight comes up to 60 grams, you could still almost get away with an M20LV geared 5:1 to give you almost 30 grams of thrust. but, you'd probably be flying at near full throttle a lot to keep it in the air. so, i'd go with that N20-ULV from the link above. the N20-LV will put out 35-37 grams of thrust, and the N20-ULV is a hotter wind, so it'll put out even more. i think it should pull your FW190 around nicely. unfortunately, the N20-ULV is sort of inbetween lipo cells. the MaxAmps 160mah cell can pull 1.92A, but it gets warm and flights are short, and the DU 300 can pull 3A, but it weighs more, but i think the flight times would be worth it (technically, around 10 minutes at a 1.5A draw). so, add 7 grams for a DU 300, and around 6 or 7 grams for the N20-ULV motor/gearbox/prop, to your 41g weight and you're looking at 54 grams, less than 2 ounces. not bad i cant find the DU cells at the moment, but i'll ask around, i know they're out there somewhere. if all else fails, the Etec 250 should work for it, your flight times might just be a little short. you could also opt for a two cell pack if need be.

you can find a lot of very usefull info here at Gordon Johnsons web site, he's one of the top guys in terms of motor constants, and has been flying RC for longer than i've been alive (and i'm 25!), so he really knows his stuff: http://home.comcast.net/~gordon-johnson/home.htm

nic
Old 02-12-2006, 04:48 PM
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Default RE: Motor choice for 16" FW190

I'm willing to sacrifice scale to make sure it flies For instance, I was wondering about keeping the leading edge where it is, but increasing the surface by extending the trailing edge and wingspan some (maybe up to 1/4" each).

I've just recycled a CDROM engine from a busted unit. I'm really curious to see if I can get it to work. Talk about light!

Antonio
Old 02-12-2006, 07:03 PM
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Default RE: Motor choice for 16" FW190

increasing the chord of the will give you some extra wing area, and more lift, so that can be a good thing. external ailerons should work just fine too.

DIY brushless motors can be a real pain. most of the time, the stock windings wont really cut it for what it needs to do in the plane, neither will the magnets. so, it usually takes rewinding the motor, and using stronger mangets. most people lighten the bell of the motor as well to help the motor out a little. you can get a .5 gram brushless motor controller from DU, but thats only for single cell opperation. here's a link for it: http://www.slowfly.com/store/view.ch...view=%23735735

you can certainly try using the motor in its stock form, you may get lucky and it might just put out enough thrust to keep the bird flying. it wouldnt hurt to try, and it would be a lot easier than rewinding, using differant magnets, and lightening the bell

nick
Old 02-23-2006, 06:46 PM
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Default RE: Motor choice for 16" FW190

[img]<img src="http://www.elnonio.dns04.com/web/images/RC/F190%2016in%20Wspan/DSC04265.JPG">[/img]

Trying to post a pic of the model so far
Old 05-02-2006, 05:02 PM
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Default RE: Motor choice for 16" FW190

GWS makes some light lipo esc. The ICS-100li is 5Amps and has the proper voltage cut off for 1 and 2 cell lipo. weight of 5grams.
they also have a selection of motors and geared motors with props that give the thrust, weight, and amperage of them.

www.gws.com.tw

Then just google(use the froogle tab) or ebay the items to buy them.

cheers.

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