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Old Aug 10, 2004, 10:12 AM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
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I made up a J250 "C" gearbox with a 1080 prop and tried it out this morning. I like the extra ounce of thrust it provides, I don't loss altitude in sharp turns anymore. I do miss the extra top end speed the J250 "B" with a 9070 prop provides, I really like those diving flybys. So.....

I decided I'll be building and trying out a J250 Dual drive for the Arado this weekend. I've done this for my Slow Stick with "D" ratio and get over 20 ounces of thrust swinging a 1260 prop. A great inexpensive upgrade.

I've played around with MotorCalc and seem to like the J250 dual "B" ratio swinging a 9070 prop. Using a 2 cell Tanic 2200 battery to support the 13.8 amps of current needed.

I'll get 15.2 ounces of thrust at a prop speed of 45.1mph. This is a big upgrade from the J250 single "B" swinging a 9070 at 10 ounces of thrust at a prop speed of 36.6mph. That's 5.2 ounces more thrust and 8.5mph more prop speed. This thing should scream....these are brushless numbers!

Attached is a photo of my Slow Stick J250 dual gearbox. I ended up wrapping it in strapping tape and filling in the gaps with hot glue. It's an awesome powerplant. I'll post a flight report and photos of the Arado J250 dual setup over the weekend.

Jimsky
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Old Aug 10, 2004, 05:56 PM
gpw
“There’s no place like Foam”
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Gee!!! that's pretty SCARY looking......tell us more....
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Old Aug 10, 2004, 07:29 PM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
2,896 Posts
Well it all stared by a thread jamin created on the idea of a dual J250 gearbox:

http://www.rcgroups.com/forums/showthread.php?t=230509

I liked the idea of a dual J250, and some quick MotorCalc simulations showed real promise….not to mention I bought quite a few of there motors at 50 cents each. The cost incentive to use these excellent little motors is a motivator.

The only thing I wasn’t thrilled with was making the bearing tube/prop shaft. Jamin’s idea was on the right track but was a bit of kludge, and seemed to be the weak link in the system. And someway of mounting this whole thing still needed to be addressed.

So, why re-invent the wheel? A GSW100 gearbox costs all of 3 bucks. Standard bearings, prop shaft and the standard motor mount. So I took a Dremel with a cutoff wheel and removed what was not needed. A bit of “fine tuning” with a sharp Exacto knife and the prop shaft/motor mount fit just fine nestled in the groove of the two J250’s.

I’ve always been a fan of JB Weld, so a bit of epoxy and the rest just fell into place. I wrapped the whole thing in a few wraps of strapping tape, and filled in the gaps with hot glue…just for some extra strength.

I just love the J250 duel setup on my Slow Stick; it’s a torque monster with over 20 ounces running on a 2 cell lipo swinging a 1260 prop. I should be setting up my photography rig on the SS this weekend too, now that I’ve got the power plant nailed down.

This will be my first “high speed” J250 duel, it should be fun to both build and fly it. Who said you have to shell out for brushless motors and special speed controllers, when we’ve got these great cheap little motors.

Jimsky
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Old Aug 11, 2004, 07:45 AM
gpw
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The price certainly is Right!!!! Very COOL Jimsky!!!!!!!!!!!!!!!!!!!....OK Boys ...get out the JB weld .....time to make motors.....
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Old Aug 11, 2004, 08:57 PM
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Virginia Beach, Virginia, United States
Joined Jan 2004
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Well I decided to jump on the Arado bandwagon. I traced the plans on my cad program and reduced it to a 21" WS. I plan to use a single IPS direct drive with a 3x3. I think it should it give decent performance. If not I have another one which can easily be mounted.
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Old Aug 11, 2004, 11:29 PM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
2,896 Posts
Sounds like an interesting project. Just keep in mind that the Arado "wing" is just a simple flat peice of Bluecor, it has no airfoil shape to it at all. The planes lift is generated my dialing in a bit of up trim on the elevons. You need a fair amount of foward speed to generate lift, and the plane doesn't really have much glide to it at all.

Just thinking out loud but perhaps putting a bit of under camber on the wing may be a good thing to do. I know on a Nutta build I recently did (ISP "A" ratio, 1047 prop) forming the wing to get just 1/2" of " airfoil shape" to it makes all the difference between a plane that climb and stay aloft and one that can't.

Additionally the blunt nose of the universal fuselage is not the most aerodynamic shape, a bit more drag the powerplant needs to deal with.

I really do love my Arado, my favorite parkflyer. And after my J250 dual conversion this weekend it should be even more fun to fly. But I've only built one Arado and have flown it for a short time.... so I'm not talking from a point of a lot of experience. Hopefully gpw will chime in and provide his advise.

Jimsky
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Old Aug 12, 2004, 07:50 AM
gpw
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Ring, ring!!!...ring,ring!!!!! Mushy,mushy.... Luftwaffe complaint office...
(us) Why did youse' guys make that fuselage so blunt and draggy...????
(them) Er!!!!
(us) and that thing glides like the Space Shuttle...can't you make it thermal????
(them) But.....!!!
(us) to be totally honest with you (cliche') I love the plane , but it SUX!!!!! Can't youse' guys get anything right......?????
(them) We'll get right on it right away ...a plane that will be perfect in every way and be suitable for all applications and it won't cost much and it'll be really easy to build ... and we'll also explain what women really want, and the meaning of life..... but you'll have to give us a few moments to consult with our engineers........
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Old Aug 12, 2004, 08:54 AM
From the bowels of MI
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GPW,
You're a funny guy! But why would the Germans answer with "Mushy mushy"?

Jimsky, that's going to be a lot of weight in the back with the dual J250... do you think it'll balance or are you going to try to 'shaft' it?

-Wayno-san
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Old Aug 12, 2004, 09:20 AM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
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gpw...you're a scream.... very, very funny.

Like engineers would know "what women really want". An artist know what women really wants...an engineer knows what a woman really needs. Big difference....

My Arado is a great plane, I really do enjoy flying it. And for me the "lack of glide" works in my favor when flying at my "small" local field...I don't have to worry about it hanging forever up there, or getting blown into the trees or residential areas that boarder the field. Gearbox driven means it quiet enough to do morning flights. I'm hoping a bit more power from the J250 dual setup will really crank up the fun, since I've gotten very comfortable flying it.

I wasn't knocking your take on it (or the original design) I was just pointing out some basic facts of the airframe that might make a single EDP50 driven version difficult to pull off.

An EDP50 with a 3X2 prop at 7.2 volts is good for 2.1 ounces of thrust according to the GWS website. OK, maybe using the 3X3 prop you will get a bit more. I was just highlighting that a low thrust powerplant and a flat wing, blunt nose airframe may not be a good match. Just thinking out loud.

But the cool thing about Bluecor planes is it doesn't take much to build something to try it and see.

Luftwaffe complaint office - thanks for the morning laugh, it made my day.

Jimsky
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Old Aug 12, 2004, 09:29 AM
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Virginia Beach, Virginia, United States
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I didn't mean to start the mudslinging. We have enough of that already since it is an election year.

Jimsky,
You were right on the power of the little edp. I am going to add another one and put a little undercamber in the wing. I did some powered test glides in the front yard and it could use a bit more. Very unstable at low speeds. It does have a slight glide. So back to the drawing board. Total weight is 4.5 ozs. So another motor would help.
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Old Aug 12, 2004, 09:32 AM
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Forgot to ask, but what is the best setup for the motor mount, ie: thrust line. Right now I have the motor mounted about a 1/2" above the wing. Should I drop it down onto the wing or is it really not something to worry about.
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Old Aug 12, 2004, 10:01 AM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
2,896 Posts
I guess the Germans must have hired Japanese quality guys to feild their complaints...

Wayno-san,
I know the J250 dual is going to be heavier. When I built the Arado I put everything up in the nose of the fuse. Because of this my Etec 2S1P 1200maH battery is located back quite a bit, so I've got lots of ability to move the battery forward to counter the additional motor weight.

Additionally I'll be using a Tanic 2S1P 2200maH, it's heavier than the Etec. My gut tells me the original battery position just might be the right spot for the Tanic pack.

pylot2b,
My geared drive is located just as the plans direct...on a stick glued into the end of the fuse...and it works just fine. I know the SuperFly Twin mounts 2 motors about 2" above the wing on pylons, configured as pullers. So I would think what you are talking about doing should work. Again, gpw has got the experience to feild this question.

Jimsky
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Old Aug 13, 2004, 08:33 AM
gpw
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Wayno.... allied trainee ... just like when you call the phone company and Roop in Calcutta answers....
Jim ... My late Father in law was an engineer , and I have a lot of engineer friends , and believe me they know alot of stuff....stuff that boggles the mind.... mystery stuff .... so I assumed that..... about the women wanting thingie' .... Sorry , mine's only a small "difference"...hahahahaha
Dual gotta ' be a rocket ,eh? new weight batt should be perfect ....
I'm afraid we've all gotten spoiled by these parkflyers with their extremely low wing loadings .... in the old days , electrics were much heavier and more powerfull , but flew quite fine , if a little bit faster than today's floaters...
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Old Aug 13, 2004, 03:31 PM
Trying to defy gravity...
jimsky's Avatar
USA, NY, East Northport
Joined Dec 2003
2,896 Posts
And life was slowly breathed into the body of the monster…..

Otherwise known as the continuing saga of the Arado Projekt with a J250 dual gearbox….

Well since this J250 dual is fabricated using JB Weld (that takes a full 24 hours to cure) I decided to get the basic power plant assembly fabricated and glued up today, so I can fly tomorrow.

Below are a few quick pictures I took:

*GWS 100 black gearbox that I usually use for my geared single J250 power plants. It’s only $3 and it’s got everything that’s needed for this build…and a bit more. Just remove the “bit more” with a Dremel and cutoff wheel.

*Cut up GWS100 gearbox, two J250’s, prop shaft I spur gear.

*A couple of shots of the glued up J250 dual gearbox.

The JB Weld setup in only 6 hours, but I’ll be waiting 24 hours until it’s fully cured. Again I’ll be wrapping the whole thing with a few layers of strapping tape and filling in the gaps with some glue. Hot glue, 5 minute epoxy or Gorilla Glue…I haven’t decided yet.

What you see in the pictures; the complete power plant with a Nylon wing nut prop saver (no noise caps installed yet) weighs 89 grams, or about 3.2 ounces.

I’ll post some more photos of the finished dual J250 on the Arado and hopefully a flight report tomorrow.

Jimsky
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Old Aug 13, 2004, 06:47 PM
gpw
“There’s no place like Foam”
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That's really pretty Sweet!!!! Are you going to wire them series or parallel?
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