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PostPosted: Tue Mar 03, 2009 2:21 pm
by xgary
ANyone seen these ?

PostPosted: Tue Mar 03, 2009 2:22 pm
by xgary
another picture

PostPosted: Tue Mar 03, 2009 4:22 pm
by ozzie
G'day Shorty
it looks like the RC predator motor.
Is this the Poms Lazair?
There is a Canadian flying a PPG with one but it has been extensivly reworked and has a redrive. the predator is a little underpowered and will burn out if you push them at max for any more than a minute or so, can only handle 60 percent or so continuos. controllers don't like the heat either
have they flown this yet? any more info
here is the website for them


PostPosted: Tue Mar 03, 2009 4:42 pm
by lazairiii
Any pics of the battery packs...and the weights of the batteries? I'd be curious to see how this plane is balanced with such light power plants up front now. Looks like the batteries may be being used for forward balast?


PostPosted: Tue Mar 03, 2009 5:20 pm
by xgary

PostPosted: Tue Mar 03, 2009 9:59 pm
by Chappy
I posted this March 1st. under the Lazair-General section, and I'm sure this is the same Lazair. Check out the magazine article referenced at the bottom of my notes. Here it is again:

"I noticed that Paul Dewhurst over in England recently said in one of the BMAA forums that he was hoping to fly his electric powered Lazair before the end of February. He is using very expensive ($1100 each) German built, brushless outrunner style Platttenberg Predator 30 motors mounted with 32" props. He has found that with the directly driven props these motors will only produce on a continuous bases 60% of their rated output (6 KW out of 10-11 KW, or 8 HP out of about 15) without overheating and failure. The motors turn these props at 7000 rpm, and are very loud and inefficient (as you would expect). The motors are very small, only 4" diameter by 3" long and weigh 3 1/2 pounds! At 50 volts, they require 220 amps for the rated output!! He is using pretty much state of the art Kokam brand SLPB Li-Po lithium batteries to supply that power. I don't know which speed controllers he is using, but it's probably the recommended Schulze ESC Future-40 160H, and they run 2/3's the cost of the motors.

I noticed that Plattenberg has since begun offering a new, more powerful Predator 37 that's rated at 15 KW (that's around 20 HP)! A pair of these with re-drives and appropriate props of somewhere around 42-44" would offer outrageous performance - if only you could afford the batteries needed to produce that much power (almost 300 amps at 50 volts wide open throttle).

Anyway, it appears Paul is using the Lazair as a test mule for a future electric aircraft ( they are calling it "Hummingbird"). I found this article that doesn't mention the Lazair, but it's obvious it's the same program. Very cool: ... flier.aspx

PostPosted: Wed Mar 04, 2009 3:20 am
by ozzie
notice the large cooling fan on the rear of the motor. that would suck a bit of power. if they can get a continuous 8hp then it should fly OK i notice they have a series 3 airframe which is heavier than a series 1. the pioneers only give a rated 5.5hp so i would consider the increase to be great rather than poor that someone who flys on the 185 engines would consider. shame the high rpm of the props drown out the quiet engines but it should be real smoooooth. instant power is a major plus. It seems that duration is not so much an issue for them at the moment as the project is an experiment to further another E aircraft. so i think they would have minimal battery weight for just a few circuits. they must be carrying them around the fuel tank area as there is some additional bracing on the rear to downtubes. The charger is another cost here. lets see 2 grand for the motors plus mods 1200 for the props a pair minimum controllers 1500. batteries at least 3500. minimum then the charger around 1500. minimum. that comes out to $11,200.US what would a solo or hirth conversion cost? anyone have the numbers for that. if you wanted to do a E conversion at a reasonable cost you would have to go single engine with redrive. larger motors and controllers seem to be more readily available at much cheaper price. to keep the cost right down you would have to be handy with a lath and mill and do your own machineing for the drives ect.
good effort by these guys. big investment

PostPosted: Wed Mar 04, 2009 2:07 pm
by Chappy
It is good to see someone finally convert a Lazair. Helps that there is financial backing of some sort. For now, though, for the rest of us, I still think it comes down to batteries. Other than endurance and cost, this set-up could fair OK on a series one when you consider that due to prop loading, the direct drive Pioneers really only produced 4.5 HP! Also, in my experience, the HP to HP conversion is not perfect, and 4.5 HP electric will always come out a bit stronger than 4.5 HP ICE. Just from a "flyability" standpoint, wouldn't it be nice to be able to set a nominal power setting and have the motors hold that setting together in a stable manner. That's not something our 2 stroke engines are known for!

The series one only carried a very small fuel tank, and was more suitable for lighter pilots, certainly under 200 pounds. Larger pilots and especially heavy battery packs cry out for more HP and/or efficiency (prop speed reducers & longer props), and even more so for a series 3. But unlike slapping a little larger engine (like the Pioneer to 185's) and gas tank on the airframe, and carrying a couple more gallons of relatively cheap gas, putting larger but still inefficient motors means giving up endurance or spending big bucks for more heavy batteries.

Since designing a prop speed reducer unit for these motors is so much easier than for the Pioneer (I say that because I've done both-at least of paper-LOL), I'm really surprised they didn't consider going that route. But perhaps they are counting on the future availability of larger motors designed for lower speed torque (very low rpm/V ratings). I'm sure those motors are coming, but all the current ones trade off significant efficiency and peak horsepower for that low speed torque, and appear to have heating issues.

For those of us that don't have a benefactor or investor, there are much more affordable motors out there right now with higher rpm/v ratings suitable for use if you go with a re-drive. There are also much, much cheaper controllers on the market that might be usable. So, going with a re-drive opens up the choices of motors and controllers quite a bit.

One more thing to consider. Current, state of the art lithium-ion battery design calls out for properly designed battery management devices. Not cheap or easy right now. Battery mounting, location, BMS, wiring, charging/chargers, it's all rather challenging. Perhaps even more so, I think, than the motor/redrive/prop/controller issues.

This whole thing reminds me of a friend of mine that years ago bought the plans and aluminum to build a popular homebuilt, 2 place aircraft. After a few years, I asked him home the plane was coming. He said he had pretty much given up on it. He started having nightmares about it. In his dreams sat his finished airframe sitting in his garage - with a big hole in the front where the engine and prop were supposed to be. Every time he had the dream, he realized that even though he could afford to build the plane, the money for the engine/prop was something he had no way of coming up with - short of robbing a bank. That's kind of where I am right now. I believe I could build a reliable, re-drive based system for my Lazair for a reasonable price. But when it gets to the point where I start thinking about buying all those expensive batteries, BMS's and chargers that would be required to make the whole thing a PRACTICAL airplane, I chicken out. The numbers just don't make sense for me. Now, if I lived on an airstrip and could pull my LazairE out of the shed for an hour or so flight everyday, then it might be another matter. That wouldn't call for as much battery power and a less expensive charger, and that would be more affordable.


Blue Skys and fully charged batteries!

PostPosted: Wed Mar 04, 2009 3:58 pm
by yankeflyer
Great thread -- great points -- keep checking eBay -- so much common interest is bound to come up with a collaboration