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Posted by osterizer | Jan 24, 2012 @ 11:57 PM | 2,602 Views
I made a post earlier this evening that needed some explanation, but I don't want to tie that thread up with this long post, so I'm going to put it here in case anyone else is interested. So please bear with me little-- i'd draw this out but it takes a long time on the computer compared to a napkin! I'm going to get a little schoolish first, but it all comes together and means something about helicopters in the end that's pretty neat.

We all learned about vectors in school; a linear force is a force exerted in a direction from an initial location. If I have an object in an ideal environment, and I put enough force on it to move it east 1 meter, then it will move 1 meter east. If I put enough force to move it one meter to the north, then it will move one meter to the north. BUT... if I put both forces on it at once, then it will move 1 meter to the east AND one meter to the north. The result will be that with both forces on it, it will go 1.414 meters northeast.

But we already knew that. Now we get to some interesting stuff. Talking about the behavior of helicopters, we have static mass and momentum to deal with, just as with fixed wing aircraft, but we have an additional item to deal with: our helicopters are rotational aircraft as well. This introduces both rotational physical concepts and differential lift into the equation, which makes the situation much more interesting.

Posted by osterizer | Jan 28, 2009 @ 06:47 PM | 4,382 Views
I wrote this up a while ago, but haven't edited it since. If anything jumps out as wrong, please note it if you can struggle through reading the whole thing. Rather than post it when the question comes up here and there, I figured I'd just put it here and people can use it as they like.

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Plugging it in:

Channel 3 is your throttle-- since we're talking electric helis, it's the power signal to the ESC, and it gets the three wire plug from that component. If it has Futaba colors, the white wire goes toward the body of the receiver and the black wire towards the edge; if it's JR colored, the orange goes to the middle and the brown to the outside.

Channel 4 is the rudder signal; you plug the gyro in here, and the same color rules apply-- and I won't mention that again for 3 wire connectors, except...

Channel 5 is the gyro gain signal, and it usually only has one wire; this goes toward the inside of the receiver if you have a tx that can do remote gain control (as in, you have any Futaba radio with a heli mode).

Channels 1, 2, and 6 are the ones people have trouble with, which is why I left them for last. The way they work is very simple, but no radio manufacturer-- none, nada, null, never --documents it in a way that you can read and say, "OK, I see how that works." Hopefully I can do so. Channels 1 and 2 are the prime example, but lets see what we're connecting first.

On a 120 CCPM helicopter (the balls that the servo links connect to are...Continue Reading
Posted by osterizer | Nov 09, 2008 @ 10:39 PM | 4,133 Views
The first thing to understand about helicopters is angle of attack, commonly abbreviated as AoA. Almost everything about flying a helicopter results from changing the AoA of the blades, from normal control inputs, to changes in the way it flies under different conditions. Before you can understand AoA, you need to understand lift and drag.

Drag is simply the amount of force with which the air pushes back against the wing, whether rotary or fixed, when it tries to move. It slows a plank's airspeed, or slows the rotor on a helicopter. Drag is constantly changing on the rotor as the inflow angle and blade pitch change. In full sized helis, other drag components are important, such as profile drag of the fuselage, but they don't play so much of a role with our little guys.

Lift is the force generated when a wing airfoil goes through the air (the big wing on a plank, or the smaller, rotary wings on our helis). Lift is the up force that keeps a plane in the air, whatever the wing type. An airfoil gets lift from two mechanisms; first, displacement lift comes from the Newtonian result of the underside of the wing pushing air down through impact on the bottom of the blades- if the blade pushes a mass of air down, then we know that it is pushed up in response. Second is aerodynamic lift, which results from air flowing over the top of the blade faster than it flows over the bottom; from Bernoulli we know that the faster moving air has less pressure, so there's less pressure on...Continue Reading
Posted by osterizer | Sep 27, 2008 @ 01:31 PM | 4,308 Views
I guess I should have done this a while ago, but then I wouldn't have quite so many helis to have pictures of. I've had a lot of spinny things in and out of the garage, so here are the ones that have stayed. Most are flyable, except one of the MXs, the King 2, and the Gazaur; I can't see spending the money to keep electronics in all of them so those are inactive at the moment.

Equipment:

Lama v3- stock (2S LiPo)

Blade CP Pro- microHeli hub, SAB 255 CF blades, EFlite brushless, MD 500 blow molded fuselage (3S LiPo)

HB FP3- stock (2S LiPo)

King 2- JGF 400DH motor, home-made CF boom, HDX300 tail unit, ESky Al head, Phoenix 25 ESC, SAB 280mm CF blades (3S LiPo)

MX450XS- mostly stock, but microHeli red tail and MAH 325 main blades (3S LiPo)

MX450XS- mostly stock, but TRex SA tail unit, RotorTech 325 main blades, S3114+S9257 (4S LiPo)

Dragonus II- an NV Plus, with Al head and tail, Radix CY325 main blades, Jeti Spin 33, JGF 500TH motor, GY401, and S3154 servos everywhere (3S LiPo)

E325 Mini Titan- Kasama head, CY325 blades, Scorpion 2208-10 motor, Phoenix ESC, S3153+GY401/S9650, Sonix tail (4S LiPo)

Poseidon- stock plus aluminum blade grips and stretched boom; JGF 500TH, RT350s, S3156+S9650 (3S LiPo)

Swift 16- stock (but for fixes I had to make); Scorpion 3026-1000, JR DS821+GY401/S9650, Phoenix ESC. (5S LiPo)

Logo 600 3D- stock plus 4134 counter bearing; Scorpion 4025-630, S9452+GY401/S9254, SK360 stabilizer, and usually flies CY600 SB mains/90mm CY tail (10S LiPo)