|Username||Post: MAS TECH - ROTORY JULY 03|
Full Time Senior Member
07-16-03 02:09 AM - Post#23049
RE-PRINTED FROM ROTORY MAY / JUNE 03
It was back in the mid ‘70s when I realized that if I was going to push the envelope of model helicopters from their present state of an occasional loop or roll, that I would first need to develop a totally new setup that would be linear in action. The standard set-up then of -2/+6/+9, only moved 3 degrees from half stick, to full stick. From half stick down, it moved 8 degrees. Therefore, it was traveling over twice the distance one way, than the other.
To fly inverted, I would need a minimum of 7 degrees negative (thick wood blades). This would worsen the standard setup even further. In order to fly inverted with the standard setup, the range from half stick up would be 3 degrees, but from half stick down, it would be a whopping 13 degrees. There was little doubt in my mind, if I were to fly inverted some day, I would have to address this problem.
Coming from an extensive background of model airplane flying, where inverted flight was a common occurrence, I knew one day it would be my next goal with model helicopters. After almost a year of thought and planning, I pioneered a new linear setup for model helicopters. I called it, “The Mas Technique Setup.” It was a completely new style of flying.
After 18 months of preparation, in 1977, my setup enabled me to become the first person in the world to fly a helicopter inverted. In addition to inverted flight, the Mas Tech Setup enabled me the ability to perform the first real aerobatics (3D) with a stock model helicopter. After my first public demonstration-arranged by Walt Schoonard of Miniature Aircraft on Thanksgiving Day 1979, and getting over the initial excitement of flips, tumbles, and numerous other maneuvers, I soon learned that the Mas Tech Setup would start a whole new era in competition flying as well. For example, in the past, when executing a roll, as the machine went knife-edge two times during the maneuver, you could only wonder where the needed 0 degrees of pitch was. With the Mas Tech Setup, I simply move the stick to center and 0 degrees pitch is right where it can easily be found.
After I introduced the Mas Technique Setup in 1977, it was not until some 10 years later that other top pilots began to use it. In fact, not until 1987, would another pilot fly a model helicopter switchless inverted. The term, “switchless inverted” came about when radio manufacturers began installing electronic switching in the radios that reversed some functions. This enabled you to fly inverted, yet move the controls in a normal manner.
Today, regardless of the style of flying, FAI, aerobatics, 3D, stunting, switchless, or whatever you choose to call it, the Mas Technique Setup has been adopted worldwide and is currently in use by almost every sport and aerobatic pilot including World Champion caliber FAI and 3D flyers.
The beauty of the Mas Tech Setup is that it does not require the mythical two-stage setup, one set of parameters for hover and another for aerobatics. Why fly a helicopter with two setups, when you can use the same setup for both. It makes no sense to have one setup when the helicopter is at 6 feet and another when it’s at 15 feet. With the Mas Tech Setup, and the use of fully symmetrical blades, the same set-up you use for your groundwork may also be used for aerobatics or FAI competition.
Another phase of development for the Mas Tech Setup was the need for a new mechanical setup on the helicopter as well. I wanted a setup that was both repeatable and linear. The Mas Tech Setup allows the servo arms, bellcranks, mixing arms, etc. to be in their center of rotation at mid-stick, thus allowing total linear movement from positive to negative pitch. This enables us to have the same deflection at 5 degrees negative as we do at 5 degrees positive. Another plus about this setup is, it will work on any radio system regardless of features. I’m using the same setup today on my 1024Z / PCM-10 transmitters that I used on my 5-channel Futaba in 1978. Keep in mind, there were no helicopter radios back then. If you needed a curve, you created it by drilling a hole off center and offsetting the servo wheel.
There were no idle-ups at that time either. I created the first idle-up on R/C helicopters using a stock 5-channel airplane radio. The collective and throttle were run from a “Y” connector, so they both moved at the same time. I engaged the idle-up by using the fifth channel switch to essentially disconnect the power to the throttle servo using a micro switch mounted on the 5th channel servo. As I climbed out from hover, I would position the throttle at approximately 80-90% open, then I would flip the 5th channel switch, cutting the power to the throttle servo, thereby locking the throttle in an open position. I was then free to operate the collective and maintain reasonable power. As crude as it was, it was a beginning and a way to fly inverted.
Needless to say, over-speeding was indeed something to deal with. I essentially used the engine’s high-speed needle as a form of governor. Prior to takeoff, I would lock the throttle at 70-90% open and de-pitch the machine to zero-degrees. The needle would then be set to prevent over-speeding with no load. Let me tell ya, this was without a gyro. And for you guys who do aerobatics, I don’t have to tell you what it’s like to keep the tail in check when a machine is falling inverted from the sky screaming with the tail going wild.
Looking at the way it works!
Using the Mas Tech setup, needless to say, a helicopter is not going to hover at the half-stick position with 0 degrees of pitch. When the machine lifts off, the throttle will be just below the 3/4 open position. This puts the engine throttle barrel exactly where we need it, 60-70% open at hover keeping the engine ahead of the collective loads. All this and we never had to touch the collective, throttle curves, or linkage to obtain the setting.
As we compare Chart #l and #2, we can see the evolution of pitch setups. On Chart #1, at the half stick position, we have approximately 5 degrees at hover, -9 degrees at low stick and, +9 degrees at full throttle. As we move the stick from half to full stick position, we move the collective a range of 4 degrees. However, as we move the stick from hover to low position, we now move the collective a range of 14 degrees. This means the typical setup has three times the collective movement from half stick to low throttle, than it does from half stick to high throttle, or a “3 to 1” non-linear collective control. With this standard setup, the collective is somewhat smooth and predictable from half stick to full stick, but very erratic and non-repeatable from half stick down. This is the exact area that is most critical for autorotations, FAI, and aerobatic flying!
I called it then, my “Seven & Seven” setup, –7/0/+7 (9 degree composite blades). Looking at Chart #2, you can see that it’s a total linear design. From half stick (zero degrees), it’s 7-9 degrees up and 7-9 degrees down. Movement from half stick up is identical to half stick down. The result is a helicopter that responds the same no matter where the collective stick is. Just as the transmitter stick is designed linear in its movement from center, now so is the control of the helicopter.
The real beauty of the Mas Tech Setup is, it uses total linear (straight) curves on both the throttle and collective. As we look at Chart #2, you will notice the linear pitch curve also provides a linear throttle curve. The distinct advantage of the Mas Tech Setup is you can physically and mentally feel and “find” a zero degree pitch setting any time you desire. This is a common natural point where the machine and rotor disk are unloaded, producing what I call, “zero lift.” Notice I said, the machine and the rotor disk, because they each can exhibit “zero lift” individually of each other. It is the combination of these two points that practically every maneuver, regardless of type, is dependent upon to occur at the same time.
Let’s demonstrate how linear the Mas Tech Setup is. A maneuver such as a roll is performed using exact 1/4-stick movements. Let’s look at a slow 6-8 second roll as an example. Let’s say you’re at 3/4-throttle when you initiate the roll command, as the machine reaches knife-edge, you simply move the stick to half position, which is 0 degrees pitch. As you reach inverted, you’re at 1/4-stick position. As you reach knife-edge again, you’re back to half stick, when the machine is up right you’re at the 3/4-stick position again.
Try moving your throttle stick linear with a conventional standard setup. Better yet, try finding exactly zero degrees pitch during a roll, it’s hidden somewhere around the 3/8 throttle position. This is the reason that a good roll was one of the most difficult maneuvers in FAI competition. Using the standard setup, it was almost potluck to find the needed zero degrees. This is the exact reason that semi-symmetrical blades were ever considered for F.A.I., because they essentially de-pitched themselves while inverted. When a pilot performed a roll, he would hold almost the same pitch, since the blades had less lift inverted. Well, bottom line-they didn’t work.
With the Mas Tech Setup, anytime you want zero lift, you simply move the stick to center position-it’s that simple. Let’s take autorotations for example, as you perform an auto, you’ll instantly know where 0 degrees is. Move the stick to center, then lower it to 1/4 stick. Next, you’ll add or subtract pitch to lengthen or shorten the auto. Inverted autos-same thing-during the “roll out” back to upright flight, you simply move the stick to the center position, do the roll, and back to normal position again. Performing tumbles or flips are a breeze, because you physically know where the machine is unloaded-collective wise. You’ll find, just as I did back in the ‘70s, that regardless of the maneuver you’re performing–it’s more predictable, since you’re moving the collective control in a linear fashion.
I have also included a “Phase 2” Mas Tech Setup. It is intended to help transition pilots from their standard setup to the Mas Tech Setup without a drastic change in performance and/or transmitter stick orientation.
The Phase 2 setup (Chart #3) will work fine for practically all model helicopters regardless of manufacturer and/or blade design. As we examine Chart #3, we find 7-9 degrees (9 degrees for 30 machines) positive top-end pitch. At the other end of the chart, in the low pitch setting, we find only 6-7 degrees of negative pitch. While this setting might seem minimal, I assure you that you’ll have plenty of inverted pitch for hovering and climb out. In addition, it narrows the negative range for autorotations.
I know how much you guys love that top-end pitch; however, it’s your enemy. In forward flight, it will cause “pitch up” and/or loss of control, as well as blade stall during aerobatic maneuvers. Remember, the less pitch travel we have, the more overall control we have of our helicopter. This is especially important with 30-size helicopters, since their control system design has less overall control of the rotor disk. Under no circumstances should you have over 20 degrees of pitch range. Let’s deviate a little, so we understand this a bit better. Unlike 60-size helicopters, most of our 30-size helis use non-precision type plastic mixers for collective and steering control. It’s not that the 30-size control system is inadequate; it’s the fact that the rotor span has increased to the point that the control system is at its maximum operational design limits.
You might not think of a 30-50-size machine as having a large rotor span; but keep in mind the 60-size Schluter Heli-Boy, the helicopter that standardized the 60-size helicopter market, had a 52-inch rotor span. A raptor 50 has a 53 1/2” span. Combine this with the fact that a 50 engine far exceeds the power of previous 60 engines, and you can see that plastic control parts have reached their design limits. This is the prime reason why, as new machines are released, metal parts become more standard. Most mods such as a metal swashplate, ball bearing mixers, washout, etc. all provide additional control for the main rotor system that the original equipment lacks.
Getting back to our Phase 2 chart, instead of using zero degrees at half stick, as in the original Mas Tech Setup, you will find the revised chart has 2 degrees positive pitch at half stick. As in the standard Mas Tech Setup, the helicopter is not going to hover at the half stick position with 0 degrees or 2 degrees of pitch. When the machine lifts off, the throttle position will be somewhere between 1/2 and 3/4 stick. Again, this puts the engine throttle barrel where we need it.
Regardless of which Mas Tech Setup you choose, make sure you start with a “fresh” transmitter model. Double check to make sure that your throttle and collective servo curves are linear in control. The Mas Tech Setup works perfect with only one point on your curve, even in idle up. The throttle “U” curve should be set up at 100%/60%/100%. Yep, just one point set at approximately 60% barrel opening at half stick for the idle-ups. If your transmitter has an expo setting for throttle, use it. It will round the point from a “V” curve to a “U” curve.
Make sure the servo wheels on the throttle and collective servos are at their half travel positions at half stick. Double-check your program to make sure both the throttle and collective curves are totally linear and the ATV (travel volume) is set to 100%. If you cannot achieve the 9-degrees of travel each way, don’t mess with the radio; replace the servo wheel with the correct size to achieve all the travels without the aid of the radio.
Make sure that the engine carburetor barrel is at the half open position when you have the throttle/collective stick at half. As you move the throttle from full open to full-closed position (throttle trim full low) make sure there is no binding or any under or over travel. In addition, it’s very important to make sure that the throttle trim shuts the engine off at full low trim position only. If the engine shuts off as you begin to lower the trim, re-adjust the rod. Just the trim position alone can make a difference on the barrel opening at half stick.
Next, we will adjust the collective. Again, you should have a linear curves ( / ) and the ATVs set to 100%. Move the throttle/collective stick to the half position. You should now obtain 0 or +2 degrees pitch on the main rotors (regardless of blade design). Next, find the proper position on the servo wheel so you can obtain 9-degrees of positive pitch at full throttle and 9-degrees negative at low throttle.
If you’re using the Mas Tech Setup-Phase 2, once you have the collective mechanically set, move the throttle to the full-low stick position and adjust the pitch ATV to reduce the travel at low stick to obtain 6-7 degrees of negative. Do not adjust the pitch curve. Using this method keeps the curve linear. In a few weeks or months, once you’re used to the setup-you’ll want to increase the ATVs to 100% again and get used to –9 degrees at low stick.
When it comes to flying with the Mas Tech Setup, no one will have to tell you it flies different or better. The machine will become predictable and linear in a whole new way. You will feel exactly what I felt back in the early ‘70s when I, for the first time, experienced a world of difference and unlimited abilities with model helicopters. RM [/B]