"Paul McIntosh" wrote
Bullshit horsepower = torque X RPM so 20 lbft X 1000 rpm or 1 lbft X 20,000 it's the same thing. BTW you don't "win" discussions. The purpose of a discussion is to exchange information not win some arbitrary point, The thing that amazes me is the lengths you're all going to to differentiate electric and fuel engines. Transatlantic flights? Three horsepower motors? Sounds like a mines bigger argument to me............
You merit the sarcasm because you have little idea of what you're talking about. Yet, you are absolutely certain of your "truth."
Screaming RPM is no indication of power whatever. A 2-cyle motorcycle engine revs to thousands of RPM, but has no horsepwer when compared to a single-cylinder marine diesel that turns at 1 RPM and can drive a freighter across the ocean.
You might want to explore the world a little more.
Moe
So, an engine that turns a fixed load SLOWER is more powerful? We WERE talking about a 5X4 prop, not ocean liners. RPM by itself is irrelevant. An engine that turns the same prop faster has maintained its torque at a higher RPM, meaning more HP.
Oh, never mind. You are stuck in your dream world where all electrics are better than any other form of power. Wanna race?
No, the screaming is an indication of wasted power.
The RPM s unsueable except in high speed flight. For vertical pulling power electrics - especailly geared - have the torque to haul themselves straight up using bigger props.
Funny how people losing arguments always resort to adf hominem attacks.
I know you have a commercial interest in selling bearings for clapped out slimers.
>
Nope you said "Screaming prop RPM is an indication of power. Your electric don't have it!" Prop speed itself does not indicate power. It also doesn't *solely* determine thrust produced which is more to the point. The problem is not that you're not making it simple enough, it's that you're oversimplifying it! Prop speed by *itself* means nothing. Torque by *itself* means nothing. If you're trying to state that electric motors don't have enough power to produce equivalent thrust because their RPMs are too low you're dead wrong. Prop pitch and diameter are critical as well as rpm. They also determines load at a particular rpm. Can a 1/2hp electric motor carry the same load as an 1/2hp IC engine? Damn right they can, even at lower rpm's, and produce the same thrust too.
Ibid: horsepower = torque X RPM. You are correct in this but that's irrelevant to your original statement.
No, you have changfed the rules.
A 5x4 prop doing 20K RPM has a pitch speed of 80k inches per minute - about 75mph.
That is pretty unuseable unless you just want to go pylon racing, and won't have more than about 16oz of static thrust.
If vertical aerobatics is what you want, an 10x7 prop doing 5000 rpm will out perform it for similar power. The electrics can be geared to do that - the Norvel cannot.
No, I prefer planes that have good steep climb potential.,
In article , Moe Blues wrote: | In article , | snipped-for-privacy@frenzy.com (Doug McLaren) wrote: | | > No ESC? Don't forget to add $25 for a 10 amp ESC (though I'd suggest | > a 20 amp one for $35, especially if you go with a Speed 400 motor | > instead.) | | Current draw for a Speed 280 with a 5X4 prop is under 5 amps. 10 amps | is overkill, 20 is just wasting weight.
So, you're telling us that your Speed 280 motor, drawing under 5 amps, with no gearbox, is more powerful than an 0.061? I don't buy it for a second. It may be a bit cheaper with only one battery pack and assuming that you already have a charger, but the performance is not even close.
My Astroflight 020 with no gearbox and a 6x3 runs at about the same RPMs as my Norvel 0.061 with the same 6x3 prop. However, it draws about 15 or 20 amps at 9 volts or so to do this, so it'll need a pretty good sized battery to keep it up for 15 minutes. It also cost a lot more than than that Norvell engine ... about $200 just for the motor and ESC (nevermind the battery pack), vs. $40-$50 or so for the engine.
As for the ESC size, I prefer to buy larger ones than a given application needs. They cost only a bit more, weigh only a tiny bit more, but give you much more flexibility. They also give you more BEC power for more servos, and run cooler and so they tend to last longer. But maybe that's just me.
| Try Jameco. Speed 280 motors are $1.75 purchased one at a time. Buy ten | and they're $1.55 each.
Found that. MABUCHIRC280RA2485 at
Also, it looks like shipping will run you $4.75. Still, that's pretty cheap.
| I'm not using a gearbox--direct drive.
You're really hurting your performance by not using a gearbox. A gearbox (and larger prop) will give you more thrust with less current draw. Unless it's a pylon racer ...
| > Back to price -- the glow setup is $40 + $10 servo + $5 fuel tank + | > $15 gallon of fuel, or $70. The electric setup is $10 motor, $25 ESC, | > $10 gearbox, $27 battery, or $72. Prices are similar, but performance | > is not. | | This has to be one of those "eye of the beholder" things. The in-flight | performance of my plane is identical to my 1/2A models of the same | size, at least to my eye. The only difference is the lack of fuel.
Maybe you made your plane a lot lighter. Maybe you never really flew your 1/2A planes `wide open throttle' at all. Or maybe your eyes aren't so good -- a 0.061 will deliver several times the power of a non geared Speed 280.
| Without wandering too far from the original topic, there's one other | place were electrics thoroughly trounce glow or gas--LMR applications. | The ability to turn the motor off, then switch it back on when desired | is something neither glow nor gas has equalled (yet).
Of course. But that's not what we were discussing ...
I'm not saying that glow rules and electrics suck -- if anything, I lean the other way. But to deny that glow still has some large advantages is silly.
You confuse energy and power. Energy is power times time (as in kilowatt-hour). Electrics can generate a lot of power, but not for very long.
Thats a pretty good combination, but 50mph is fairly slow, slower than most trainers with bushed 40s (just to give a speed reference). There is an econo .049 CL class that gets around the circle at around 70-80 mph using Cox TD .049s. They are slugs compared to the newer generations of engines such as the Norvel line.
A geared electric is still screaming, but just to itself!
See, you can't just use the simple comparison. You have to throw all kinds of other qualifiers in there. I never said anything about how the power is used.
/ "Paul McIntosh" <
Nope you said "Screaming prop RPM is an indication of power." You didn't say anything about props or speed 280's. You talk about apples and oranges and gerrymandering but you try to cripple the electric with the wrong prop and a smaller motor? Get real.
That's for the "recommended" applications. The motor really is identical to the Graupner Speed 280--I have examples of both, and I've dissected both, and there's no discernable difference in either innards or performance. Really does make life cheaper to buy them 10 at a time (thus bringing cost, including shipping, to under $2 per motor.) Bargain of the year!
Incidentally, Jameco also sells the Mabuchi 380, which is identical to the Graupner Speed 400. If I remember right, they only want about $5 for these--another bargain!
Hey, if I had a 280 gearbox, I'd probably design a model around it and use it. But the one I'm flying direct drive is the same size and configuration as my old 1/2A models.
Yeah, my electric are A LOT lighter than my 1/2A models. All of my older ones flew behind the Cox .049 and .051 engines--no throttle, just full power all the time.
Neither am I. But Paul has the mistaken idea that electrics are stuck somewhere around 1994--when most of them really did suck.
Moe
Don't even try to put words in my mouth. All I have ever been saying is that electrics can't match the performance of glow when comparing weight or cost. Period. No one has shown me anything different.
We've been getting some newbies showing up at the field with these so-called park flyers with these small electric motors and they are real junk. Most of them cannot sustain flight if there is any wind at all. They are definetly low performance, and when they do push them with a little larger motor their wings fold up like cheap suits. Joe L.
Weight yes, cost no.
With Lithiums.
The TD is a wimp compared to other engines in that size range. The Cyclon, CS and several Russian engines are far more powerful. I have a CS CL speed engine that turns a 5X3 at around 30k and the FF version runs around 26k. Even the Norvel sport engines are more powerful.
Yep, there are marine diesels that work that way.
My reply was to Paul's contention that RPM is the sole measure of power. It is not.
Moe
Greetings,
My first plane was an Ultra Stick 40 with an Phasor 45/3 on 16 CP2400's ( yeah, I know. Dumb plane for a newbie but it sure flew great and had plenty of power). I ran it on an 11X7E prop and it lasted quite a while until I let it get too far away and I lost orientation. Another motor that would be great in an Ultra Stick 40 is the AXI 4120 outrunner. No gearbox! Good luck!
Art
Both of those are miniscule compared to the added weight of a dead battery!
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