I'm looking to resurrect my 15 year Great Planes Spectra. The motor and rcvr batteries, of course, are shot. Rather than buy a separate rcvr battery can I buy just a BEC to use in it's place? If so can someone suggest a supplier?
I'm sure I could also buy a brushed ESC w/ BEC, using that to also replace the servo w/ mounted switch that turns the motor on and off. But I'm sure I'll eventually have to/want to go brushless, possibly rendering the ESC as extra junk.
WhoIsIt wrote in news: firstname.lastname@example.org:
absolutely. I haven't had a separate Rx battery in an electric-powered plane in many years.
If so can someone
I'll stay out of this one, but there are a lot of good, reasonably cheap brushed motor controllers out there.
I doubt that you can get a BEC for a lot less than the ESC would be. And as much as I love my brushless motors, I'm not sure you'll be able to convert your Spectra. I have a powered glider from that era, too, but when I looked into converting it to brushless, the brushless motors were simply too light and too powerful!
For example, if I replace the MA 05G that's in my plane right now and put in my biggest brushless, the brushless motor would be 6 oz lighter (3 oz vs. 9 oz) and would have double the thrust. On my plane, at least, this would mean I'd simply wind up stuffing 6 oz of lead in the nose and then holding back to about 2/3 throttle so as not to risk ripping the wings off. Yes, I'd pick up some efficiency improvement, but even with the old brushed motor, I could easily plop in enough Lipos to give myself 12 minutes of full-power climb (enough for >1 hour of flying), and it would still be lighter than the original. So I wouldn't be getting a longer flight from the brushless, and I wouldn't be able to take advantage of the lower weight or higher thrust.
If my plane had been designed for a brushless motor in the first place (longer nose, stronger wing!), it would be a whole different story. And I'm planning to build one - oh, my, yes.
Now, simply replacing the nicads in your Spectra with a 2-cell LiPo pack should give you a very nice performance jump - you should be able to cut your take-off weight by about 20% while doubling the motor run time. I did that with my powered glider, and it certainly made it a more fun airplane.
| I'm looking to resurrect my 15 year Great Planes Spectra. The motor and | rcvr batteries, of course, are shot. Rather than buy a separate rcvr | battery can I buy just a BEC to use in it's place? If so can someone | suggest a supplier?
A BEC is just a voltage regulator (at least the smaller ones are. The larger ones are full fledged switching power supplies!) So any 5-6 volt voltage regulator IC will work, as long as it has adequate current handling capacity. (One that will do an amp will probably be fine for you.)
| I'm sure I could also buy a brushed ESC w/ BEC, using that to also | replace the servo w/ mounted switch that turns the motor on and off. But | I'm sure I'll eventually have to/want to go brushless, possibly | rendering the ESC as extra junk.
Brushed ESCs are pretty easy to find cheaply nowadays, with people selling them to get brushless ones. Watch Ebay, swap meets ...
Certainly, I'd ditch the servo and mounted switch and just get an ESC. You'd save weight too.
While the Universal BEC is what I'm looking for, for the price or a bit more I can get a whole ESC/BEC and lighten my all up weight by a couple of ounces. Moving to a 2S lipo instead of the previous 6 or 7 C size NiCd will lighten it quite a bit too.
Mark's comment about the weight difference in moving to a brushless is quite valid and something I forgot about when I posted my initial question. I 'll just have to make sure that when I lighten the other bits that the CG is still OK.
True but I'm also thinking about that clunky standard Futaba servo and the rcvr battery that'll all go away, too. It's been sitting on the shelf for so long I really ought to get it down and check it out.