Topics

121

Slope Soaring / First the good news......and then the bad news.

« on: October 18, 2008, 23:45:04 PM »

Once upon a time, there were three bears,....................No, on second thoughts I guess you've all heard that one before.

How about this; Once upon a time, (about a year ago) I thought I'd try my hand at building a glider

Ordered a Sprit "Elite" from Great Planes. A box of 'bits' with a very large sheet of paper arrived a week later. So I started to build it.


Then I built a bit more.


And then a bit more


Finally had it all built. (Can't show a picture, dam thing wont up load) Looked a bit strange. Polyhederal wing with ailerons and flaps. Never seen one like it before

Took her out to Mt. Lienster today. And she FLEW!!! It's very difficult using both hands to fly the plane and take pictures. I just pointed the camera in the general direction and pushed the button!


I found the ailerons very ineffective, probably because of the polyhederal wing. (Could that be the reason Fred?)


Assending for a loop which she did very well. But because of the ineffectual ailerons she wont roll. (Or at least I couldn't get her to.)

I flew her three times with no probs, but on the fourth flight,..........ooops I let one wing drop on landing..............Not Good! Broke part of the joining section of one wing. (Where the two halves meet together above the fuse')


And split the fuse'

But on the basis that if I built her, then I can repair her I hope to have her back up in the air before too long!

There,.....that was a more interesting story than Goldilocks and the three Bears, wasn't it?

Keith.

122

Electrics / Nano-Phosphate For Ever

« on: September 14, 2008, 14:00:18 PM »

I've just finished building and testing some multi-named battery packs. You might have seen them referred to as any of the following: A123 Batteries. (After the name of the company that developed them, A123 Racing.) Or M1 cells, or Lithium-Ferrite batteries. (Li-Fe) or Nano-Phosphate batteries.
But a Rose by any other name is still a Rose.

The main problem with these batteries as far as I've experienced is two fold.

1/ Their weight per milliamp is slightly higher than that of Li-Po's
2/ These cells only come in one size: 2.3mAh at 3.3v

Each cell is 65mm high and aprox 26mm dia. (About the same dia as a 2Euro coin.)

I should think these facts alone would make them of little interest to power gliders, but to electric power flyers like me they're FANTASTIC. (In my opinion)

Why? I hear you ask. :?:

Well, just look at the plus side:

A/ These cells pose no fire risk, so you can recharge them inside the model if you want to.

B/ They only need balancing every 10 to 20 cycles.

C/They are no more expensive than Li-Po's

D/Discharge rates of 30C. - Phew!

E/ They last for between 1K and 2K charge/discharge cycles. Yes, you read that right, up to 2000 cycles!

F/ And here comes the icing on the cake; they can be safely recharged at 4C i.e. Fully recharged in 15 minutes!

These batteries have been used in the cordless power tool industry for some years now. In fact the cheapest way to buy them is to buy a cordless power pack that uses Nano-phosphate batteries and remove the cells from the pack, as I did.
This has the added advantage of getting cells that have a tin plated solder tag spot welded to each cell. (I should point out that these cells have an aluminium casing,.....very difficult to solder to.)

Guys, this has been a very long post and I'm not used to all this typing  so I'll stop now. If anyone wants any more specific details, just ask.

K.