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Old May 09, 2004, 12:06 PM
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Palo Alto, California, United States
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Speed 400 Electric CL model

Here is a picture of an electric CL model I've been experimenting with. It carries batteries on the plane (3S x 340 mah Li-po) and uses a relay to switch the power on and off. the handle has a thumb switch and a 9 V battery to signal the relay. The 9 V relay power travels along the flying lines (insulated 26 AWG stranded wire) which are 15 feet long. The motor is a Speed 400 with a Cox 5x4 propellor, direct drive. I scratch built the airframe and it has a 24 inch span and a 6 inch chord.

I've only flown the model a few times since getting the bugs worked out and it flies reasonably well for a small model on short lines. I can do loops, outside loops, figure 8's, and fly inverted. Flight times appear to be in the 3-5 minute range and I'll try to measure this more carefully. I've flown it inside a small school gymnasium where others were flying indoor RC and it worked well in the small confines.


Steve Morris
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Old May 09, 2004, 03:08 PM
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Telford Pa
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Awesome job. Looks like there may be some life out there after all. Neat looking airplane. Keep up the good work. Could you use an esc with a bec to eliminate the need for insulated lines to control the relay? Or is this just a low budget experiment?
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Old May 09, 2004, 08:22 PM
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Mike,

This is a low budget experiment, so there won't be any speed controllers or wireless links. I wanted something to fly at the indoor RC fun-flys that doesn't require waiting for frequency clearance. It seemed like a small CL plane was do-able with Li-Po power and this model is a test.

Thanks,

Steve
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Old May 10, 2004, 02:34 AM
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N. Staffs, UK
Joined Jan 1997
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Excellent work Steve. The switch on the handle to energise the relay is yet another new variation on a familiar theme. I like it a lot. Would you mind if I added it to my web page showing some of the various ways of controlling power on electric C/L models ? It's definitely time I updated it anyway because I haven't even added the latest infra-red controls yet.

You're lucky with your indoor flying companions. The only time I've flown C/L indoors with anyone else around it took up such a large proportion of the small flying area and so terrified the R/C fliers that we were immediately banned .

Steve
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Old May 10, 2004, 11:24 PM
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Steve,

>Would you mind if I added it to my web page showing some of the various >ways of controlling power on electric C/L models ?


You have my permission to use anything I've posted on this forum for your web site.

Regarding the mix between RC and CL models, the place I flew mine was not very crowded so there was no conflict. A lot of people have lamented the declining interest in CL models and it would be nice if electric versions could help change the situation. No noise, easy starting, reliable engine runs, etc. I really like having the on/off switch for "throttle" control so I can land the plane when I choose or reduce the flight speed and cruise for a few laps. When flying glow models I always hated trying to guess when the engine was about to die. I was often caught trying one more outside loop when the tank would run dry...

Thanks,

Steve Morris
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Old May 14, 2004, 04:41 PM
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Power Over Lines

Hi gentlemen (& ladies?). I am new to this forum, bear with me if I am re-stating old points.

I am puzzled that all talk of C/L electrics dismisses power on the lines while apparently not addressing the basic problem - which is that R/C type motors are wound for high current/low voltage.

That is the obvious setup for onboard power where you have a few battery cells (low voltage) sending lots of juice over short, fat wires. For off-board power you have lots of cells separated by long, thin wires you need a fundamentally different motor, IMHO.

A couple of years ago I experimented with a $5 Radio Shack speed 300 with an 18 volt winding running off a 24 volt power supply plugged into the wall in my backyard. It flew quite nicely, but was far from optimized - basically I took a $5 drugstore foam glider and modified it.

I am going to try again now with a Brodak Trainer coupled to the same motor with a GWS gearbox and big prop. I believe I can keep the current down to less than 2A and hence about 28 gage wire.

Any thoughts on this? Also, does anyone know where to get a 24v wound Speed 400? Mabuchi has not replied to my inquiry.

Ash N.
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Old May 14, 2004, 05:21 PM
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There are to many draw backs to power over the lines. You will never get any type of real performance out of that type of setup. If you want the sure thing power on board is the only way to go. If you just want a trainer I would copy mlbco's (Steve Morris) setup and replace the li-poly battery with NiCD or NiMH cells to keep the cost down. Or you can use the li-poly pack and also use an esc with BEC to turn the motor off and reduce the weight and drag of the lines to run the relay. Then you would be able to fly on conventional .008 braided lines. I'm not saying power over the lines won't work, I'm saying power on board will work better. Either way keep us updated and show us pictures of your progress (we like pics).
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Old May 14, 2004, 05:36 PM
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I decided to give my plane a quick paint job and foolishly chose Sig color dope w/o thinner. I must have added 2 ounces of weight and the results look kind of ugly! The plane was struggling through loops with the extra weight, so I added trailing edge flaps coupled to the elevator and they make a big difference in reducing the diameter of the maneuvers.

If I were to build another plane I would make it lighter and use a 2P-3S 340mah li-po pack so that the extra weight is in the form of energy storage. The KoKam 340 size pack claims to be capable of 20C discharge rates and this is why I would use two of them in parallel. My current flight times are around 3 minutes which is a bit shorter than I'd prefer.

The only other problem remaining is the short flying lines (15 foot radius). When I take the plane inverted, I sometime loose it because it gets ahead of me when reversing direction. Longer lines would be nice and if they were lighter, that would help too.

Steve Morris
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Old May 20, 2004, 02:16 PM
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What was your original all-up weight? At my school in the 'Things that fly' class the teacher teaches the kids (7th and 8th grade) how to fly controll line, but the old Cox motors are always crapping out and annoy my english teacher (well, I see that as a plus, but she doesnt), and building a s400 powered plane would be alot of fun.

I wonder if I could set it up with a switch that turns the plane off when it hits the ground?
Thanks,
Jonathan
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Old May 20, 2004, 05:13 PM
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I'm sure some type of micro switch could be easily set up to do that. Just imagine what a bumpy landing would look like (power on, power off, power on...)!! Or a tough and go! Might be fun to play with.
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Old May 21, 2004, 02:52 AM
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Absolutely, a microswitch with a 6-8" piece of music wire to switch it was probably the first electric C/L "control system" any of us used. If you add a small relay you can even arrange it as a permanent switch off so the motor won't come back on once it's touched down i.e. if it bounces. OTOH Mike's version is simpler and might be more fun .

Steve
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Old May 21, 2004, 11:06 AM
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CAFplanekid,

The all up weight of my model is 9.2 ounces (without handle and lines). I like using the switch on the handle for throttle control. You push it to fly and release it to glide. It's very simple.


Steve
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