Hi . . . just joined

[BeninTucson]

Hi everyone . . .

I just joined here and thought it would be good to post a basic "hello, I'm here" sort of introduction and to see if I can
intelligently operate the forum software. I'll be exploring archived topics/posts here on Endless-sphere over the next
couple of weeks and jump in on some of the more specific topics thread later on.

Basically, I'm wanting to build a lithium iron phosphate battery pack from sixteen (16) A123 cells (26650 size, 3.3V,
2.3Ah) for a 13.2V "cube." I know that Doctor Bass hangs out here and I'm inspired by his YouTube video concerning
this . . .

http://www.youtube.com/watch?v=JgJ-BHUXQeQ&feature=related

A little powerhouse battery like this, for me, would end up being taken to the flying field to be used (with specific charger
circuits, which all seem to want to work off of 12V to 15V sources) to replenish tiny Lithium Polymer batteries (little flat
foil packs in the 90 mAh range) and supercapacitors (cylindrical 3 to 5 Farad things) that get stuffed into tiny electric
powered model airplanes. The conventional sort of 12V field recharging source for this is still typically lead acid or gel
mat cell technology.

Although I'm not opposed to occasionally relying on plugging into the wall with an appropriate AC charger at first, I'd like to
eventually configure a solar PV panel (40 to 45 Watt range) and matching charge controller to get the 13.2V LiFePo4 battery going.
Makes sense, since we get 300+ days of sunshine per year down here and I've got a back yard with a fairy unobstructed southern
exposure . . . and I'm not opposed to stuffing the whole panel/controller/battery rig into the car and setting it up on the flying
field for additional charging.

If any of the "old hands" here know of particular topic threads where this sort have thing has been discussed before, please don't
hesitate to point me in that direction with hyperlinks. Thanks in advance.

Ben Nead

Tucson, Arizona, USA

. . . hereinafter signing all correspondence
(as I do many other places) . . .

Ben in Tucson

 

[morph999]

welcome

 

[BeninTucson]

Hi "morph999" . . .

Thanks. I'm still plowing through archived topic threads for the most part. Given my current interest
in 16 cell A123 assemblies, I've found this thread concerning battery management circuits particularly
fascinating . . .

http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416

I'm skimming and got through about 20 pages - out of the current 88 - last night. No doubt
I'll have questions, but some of them might already be addressed on the 68 pages still unread.

I note a couple of electric powered airplane topic threads here and I'm sure I'll add to
those in time.

Geez . . . this place is BIG!

For what it's worth, this is the forum that I own. Approximately 200 of us from around the world
chat about tiny free flight model planes powered by tiny solid fuel rocket motors . . .

http://www.jetex.org/scripts/yabb2/nph-YaBB.pl

This is an example of a simple rocket glider model I've built, powered by one of the Czech
made Rapier rocket motors we've been using these past few years . . .

. . . 12" wingspan with an all up weight of about 13 grams. I've lost several of these by having them
fly out of site, but new ones can be built easily and inexpensively. The motor puts out about
50 miliNewtons (mN) of thrust. People think I'm crazy for being into stuff like this,
but they would probably think I'm crazy even if I wasn't. :wink:

Lithium batteries? Supercapacitors? I'm still learning about that stuff. That's why I'm here.

Ben in Tucson

 

[TPA]

Man! don't show me stuff like that!

I have enough stuff to do! Now you show up with more cool stuff. How am I supposed to explain to my wife that I want to build a rocket plane. I'll be in the doghouse for sure!

*starts thinking about miniature tracking stuff, so as not to lose planes*

*multi-stage rocket engines*

See what you started! :lol:

 

[spinningmagnets]

Ben, have you seen the website www.luft46.com ?

 

[BeninTucson]

Hi guys . . .

"TPA" . . . this sort of thing isn't that expensive to get into, as far as a lot of model airplane stuff goes. The planes are cheap
and the motors are about $2 a pop. If you get good and your planes don't crash, you tend to go through a lot of motors and this
can certainly add up.

Multi-staging isn't much of an option here. It's a bit different from standard model rocketry that most folks envision.
Motors burn for about 15 seconds and models have to be hand launched. One of our master builders is Steve Bage from Scotland.
Here is a YouTube video showing one of his planes being launched by his son . . .

http://www.youtube.com/watch?v=HlZTknU_H-Y

The "duration" planes tend to glide well after the motor expires and will sometimes get caught in thermals, rising columns of
hot air. This is when they get lost. Free Flight models a little larger than this (and not necessarily just the rocket powered ones)
tend to glide even more efficiently and these are fitted with simple timer gadgets - called dethermalizers - that pull the tail
up or otherwise change the aerodynamic characteristics enough to let the plane float back to Earth like a feather. The (full size)
Burt Rutan Spaceship One has a dethermalizer tail system to allow it to float through the upper atmosphere without burning up.
Dethermalizers (or D/Ts) are tricky to install on tiny models, though, and adding an extra 2 grams of weight would compromise flight
performance. D/Ts come into their own on planes with wingspans of 18 inches or greater.

Same with electronic tracking. The current state of the art works well with larger models but the devices would weigh down
little models like this. I have high hopes that GPS stuff will eventually get small and light enough to install in these planes.
If a chip and complimentary battery can be made at around 1 gram and end up at around 1/2" square, then it will be worth it.

The scale replica planes don't float away as often but are challenging in other ways. The early (1940s & 50's) jets make better scale flying
subjects, since their aerodynamics work better at relative slower scale speed these models planes will fly in.
And, yes, "spinningmagnets." the Luft '46 site is a treasure trove of such early scale jet data.

Mike Stuart in England built a lot of scale Rapier jets a few years ago and his site has pictures of planes from all over the world.
These models look nice enough for static display but they actually fly! This is this first of 6 such jet model gallery pages on
Mike's site . . .

http://www.ffscale.co.uk/rapgal.htm

Another guy who did a lot of scale rocket planes a few years ago, Marty Richy, has made a lot of Luft '46 fliers from 3-views.
After a couple of his models got burned up with defective motors that burned through the casings (a hazard with this rocket plane thing,)
Marty now engineers the same model planes for tiny ducted fan motors (getting this post back to electronics) which fit inside the
fuselage and behave like the little rocket motors. There are now "flight profiler" chips made that allow the electric motor to
run at near full power for predetermined times for a clean takeoff and then idle back to lower power for the remainder of the flight.
Little Li-Poly batteries power everything. Naturally, a lot of this tiny electric stuff is adapted to micro radio control (R/C) and that's
what most folks hear about. But the free flight guys are having just as much fun these days.

Ben in Tucson