There is a 3D monster inside you. Let it out; unleash the beast inside you with the ultimate refinement in the current trend of helicopter designs.
Avant releases the Mostro Line of Radio Control Helicopters
Aptly named the “Mostro”, the machine is the refining of the current trends in the helicopter world. It’s double stage direct-to-swash machine with a refined DFC head that combines the best by far technology used in the RigidCore head with a correctly designed Direct Flight Control (DFC) system.
A head from the headmasters…
Some people say that FBL heads are all the same because the one flying is the FBL unit but people who owns a RigidCore head knows better than that. The RigidCore head is a refined design that has absolutely none of the bad tendencies that plague other FBL heads have such as wobbles at low head speeds, low energy retention autos, dampening-generated vibrations and other well known issues that people tend to dismiss as quirks. We at Avant are not happy unless the flying experience is one of true mastery of the mechanics and physics of the machine. This is why we took the time to refine a DFC head that would match our standards.
We wouldn’t be happy knowing that a potential fatigue issue such as the one that plagues many DFC designs would create a crash or due to designers that trying to minimize the fatigue problem end up making the system loose enough to lose precision and crispness.
Out of that we combined the tried and true system used in the RigidCore head with a polymer-based DFC follower arms that would create the perfect response and be durable and precise. WE also added a small pinhole to the polymer that allows for the insertion of a small 1.5mm pin used to rotate the polymer bar effecting the “turnbuckle” threads at the end. This makes the snapping in and out of ball links unnecessary and allows for minute less than the normal one half turn adjustments possible.
Unlike other designs the DFC pivot point doesn't rest on a screw, it rests on a milled shaft integral to the pitch arm eliminating the fatigue point of a screw interface.
To all of that you need to also mention that the design of the head yoke block is a piece of art. If you can make it awesome from the engineering and performance point of view why not make it also beautiful?
Servo layout because symmetry matters...
Regarding the swashplate servo drive system. We wanted to have the shortest possible distance without resorting to weird geometries that force the electronic FBL unit fight back geometry that’s not the best suited to mimic what the radio control system’s gimbal does.
No matter what system you’re using the radio’s gimbal is composed of two potentiometers that measure two angles. Those angles are the rolling (Side to side) and the flipping (Up and Down) movement of the stick by your finger.
The best way to match that is to have symmetry in those two directions. The most critical in maneuvers is the side to side and that makes it naturally better driven via two “mirror-image” configuration servos so that maneuvers like fast side tic-tocs are performed mostly by the mechanics and less by the electronics trying to compensate for the mechanics weird geometry. This results in the decreasing the delay between the FBL gyro sensors sensing of an unintended movement created by odd geometry and the correction and amount of that it has to do to compensate. The same effect is created by having the two mirror image front servos go up and then back one go down but using an opposed direction to compensate and mimic the front ones.
Servos need our support too…
Another thing we had seen was how fast the cyclic servos wear out because of the load on the servos that is carried exclusively by the force that the servo shaft applies to the servo case.
Servos are designed to handle torque well via the gears but not so well when forces are applied to the servo trying to bend the servo shaft. You can eliminate that by using push-pull servos driving bell cranks like we used in the Aurora but a push-pull system can’t be used in a direct-to-swash approach.
We thought about it and we decided to eliminate those forces by adding a support for the servo shaft by the addition of bearing-grade bronze bushings that receive a small stainless steel shaft we added to the servo screw. This eliminates the wear of the servos saving a ton of money on servo replacements. The kit comes with the correct threads and lengths for the most popular brands of servos.
Bada-Boom! There go the boom supports…
Boom supports are a thing of the past. The machines need to look nicer. The technology is available so why not use it?. Yes the obvious answer is Carbon Fiber. The lightness and extreme rigidity of the boom made out of carbon can only be enhanced when a much larger diameter boom is used. Also why round? Because round is the ideal cross-section to handle torque. If you want to try to test it yourself try applying torque to a toilet paper cardboard roll and you’ll see that the small flimsy material can handle quite a bit of torque. Now try that with a square or rectangular tube made out of the same material and you’ll see an order of magnitude of difference in torque handling.
Not only the shape is important but also how it is supported. In the Mostro we have two far away spaced boom clamps that decrease the bending force applied to the boom.
We also made the area of physical contact between the clamp and the boom very large so that the area spreads the pressure from tightening to more area are protecting the tube from damage due to excessive tightening.
Because you got to stay cool…
If you notice, unlike in the nitro Mostro, the electric Mostro canopy features two air inlets. Those are actually true NACA air inlets designed using the real aerodynamic engineering approach.
We wanted to have a way to let air in the canopy without it looking like a patchwork of holes and without it increasing the drag. That problem was also an issue many years ago and engineers at NACA (today’s NASA) came up with an air inlet design that allows for high flow of air inside and minimizes the drag. We also wanted it to be functional and again beautiful so we added two very large NACA air inlets to the bottom of the canopy and added an air diverting plate to direct the air flow to the ESC and motor area.
Just to make sure it worked we put together a canopy with the diverting plate and tried it outside a moving vehicle. We were quite surprised at how much air goes into the canopy. Once we saw the little hurricane inside the canopy and how effective the NACA design was to draw air inside we knew it was going to be cool inside that canopy.
The generously sized main gear uses a much stronger tooth design and a special helical angle. Most helical angles available are not actually the best suitable angle for the application we have in radio control helicopters. Because of that we mad special angle and tooth an important part of the gear system. The large diameter gear implies lower forces per tooth applied and the larger size of the tooth itself means much stronger strength at the base of the larger tooth.
A correctly designed helical gear gives you the quiet ride of the helical gear system with a minimized undesirable axial force effect.
Extend the pleasure…
Most flyers in the hobby go to the field on a weekend and when they go to fly they spend the first couple of minutes of the flight calming down from the excitement and when they’re just starting to enjoy the flight then all of a sudden they’re out of power or fuel.
Something as simple as battery capacity that would fit in the heli or tank fuel size can solve that problem.
The Mostro Nitro has a large tank for the fuel hungry 120. This tank easily allows for very long flights and extends the pleasure part of the flight quite a bit. He same applies for the batteries. In the Mostro we designed it with the ability to carry up to 8000mah batteries. An interesting thing about large batteries is that because of the large mah number a dirt cheap 35C 8000mah battery can supply the same current than a 65C 4000 mah battery can but you get to fly around 8-12 minutes instead.
This is truly a new approach that we are introducing in the market.
In the design of the Mostro we wanted to have all the mechanics connected by rigid elements without flexible elements being part of the system unless they needed dampening. The result was the design of what we call the Mostro “Monoblock” ( single block).
In the Monoblock design all elements of the system that affects the gyro sensing are mounted in a rigid superstructure. No part of it rests on the flexible frames unless it needs dampening.
The Monoblock is actually the flying helicopter. You could possibly strap some batteries to it without frames and fly the thing by itself.
Nitro vs Electric? How about both?
One of the best things about the Monoblock is that you could have one Monoblock and switch it between nitro and electric frames without much trouble. If you’re not sure what you like then have it your way and change it later if you want.
The nitro has a bearing block that uses the same bolt pattern of the electric motors so that even the motor plate is used in the nitro. Swapping between them is pretty simple.
The price is right…
Most people don't know this but because we setup a mostly automated manufacturing facility our pricing of spares has been the same as Taiwanese manufacturers for about two years almost to the cent so you can now fly USAn made high quality product at asian prices.
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