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Update #4 on Mostro Kits

Update on the release of the Mostro kits.

As posted elsewhere we have been waiting for a few parts we shipped out to third party vendors  that needed processing to be completed. We received most of them back and there’s only a few left that we’re waiting for because of delays who our suppliers blamed mostly due on the holidays.

In the meantime we kept testing the units and we found that after the last change of adding the double one-way bearing  we created a situation in a part that had previously had perfect performance but due to the new design wear showed up and had to be recently corrected.

As you can seen in the pictures below  the new parts we announced for the double one-way included what we call a conical pulley because it’s shaped as a cone.

This conical pulley is the one that drives the tail pulley. In the part we announced we kept the original bolt pattern using one through bolt and nut.  The initial testing showed excellent performance but recently we noticed that play had developed in the shaft contact area because the original single bolt and nut design doesn’t offer support for a new torsional strain created by the new conical shape.

We discovered that when the bolt was parallel to the boom and when the tail blade rotor is under load the force from the tail blades under load would not move the conical pulley but when the bolt was perpendicular to the boom line then the conical pulley would not have a locking fastener preventing the rotation of the top of the conical pulley towards the tail. This very minute rotation with enough flights generated a very small play by slightly deforming the shape of the pulley shaft contact area into a slightly oval shape. Even though it’s not something that can be seen in plain sight when you measure the diameter across and perpendicular to the bolt with precise instruments there are very slight differences of diameter of a couple of thousands of an inch that indicate the in time it could become a problem.  Even though for a customer the problem would take hundreds of flights to appear we decided we can’t sell a product with a known wear issue so we corrected the problem by using four screws that offer support and prevent play at any point of the rotation of the conical pulley. The new conical pulley and new shaft  have been in production for a few days. We decided that in order to make the kits available faster we will not wait to have them all ready but instead we will start shipping kits as soon as  those two new parts are being finished once we receive back the remaining parts being processed by third parties. The kits will be shipped in the strict order in which they were ordered.

If you were smart enough to pre-order your kits you will be receiving kits soon. Same with Dealers that placed orders ahead their customers will receive kits sooner than dealers or customers who placed orders later but then again a strict first-come first-served policy will be used.

Keep in mind that we don’t know the exact date that we will start shipping kits but based on the current information we’re expecting that around the beginning of February there should be a good number of kits shipped as we normalize production and will continue to ship as a regular product. 

New conical pulley with four screws prevent the play in all positions and eliminates the wear.
New four-screw intermediate shaft for the new conical pulley.
Hope you had some happy holidays and we wish you a happy and prosperous New Year.
Avant RC.

Update on Release 3

We hit a snag during production that is delaying us. As posted in a previous update we were planing to have the release a few days from now but one of the CNC machines used in the manufacturing has a problem with the Automated Tool Changer (ATC) that keeps stopping the production of that machine. We’re working with the machine manufacturer to resolve the problem. They asked us not to use the machine until they come and fix it. This could potentially delay the release to the end of the month so we will have to play it by ear. We would rather say end of the month instead of what could potentially be sooner than that because that way if the problem resolves quickly we get to release sooner but if it doesn’t then we release at the end of the month.


Sorry for the inconvenience that this can cause to your plans to have your helicopters sooner but we’re working hard to get them out asap. We’ll keep you updated.


Avant RC.

New Boxing of kits

We changed our approach to boxing and we now have a single box for the larger helis like 700 and the 600 lines as well as smaller boxes for the smaller helis like the 500 line that’s being developed. This approach allows us to tailor the kits to the ones that’re being manufactured.

We are now packing the helicopters in a main box that contains 4 boxes inside as well as space for the booms.


There are four boxes. A large one contains the Canopy, a smaller flat one one contains the frames and some of the bags, another flat one one contains more bags and a small one contains things like tanks, fan shrouds and other taller parts that won’t fit in the larger flatter boxes.





Update on release 2

Testing the prototypes we found a prematurely worn-out bearing in a swashplate.
Investigating the cause we were able to determine that the method used to install the inner swashplate ring that we have been using without any problem in the Aurora creates a premature wear in the bearings used in the Mostro.

The Aurora swashplate uses a single thick-walled bearing in the swashplate and the inner ring is installed by “flaring” the bottom of the inner ring to secure the bearing in place. Going to a 12mm diameter main shaft the inner diameter of the swashplate’s bearing needs to be bigger leaving less space between inner and outer bearing.

In the case of the Mostro and many other helicopters today we opted to use two smaller cross-section bearings instead of one. This has the nice effect of allowing the torque that the servos apply to the swashplate to be distributed between two separated rows of ball bearings instead of one.

The problem arises because the bearing being a smaller cross section have thinner walls so they don’t like the deforming forces that a flaring tool does on them when installing the inner swashplate ring.

The solution was to develop a split threaded inner ring that allows for the installation of snug fit bearings without creating any pre-loading on them by a flaring tool. At the same time we developed a different outer ring that also has no need for press-fitting and has a locking screw that holds the bearings in place.

We started the process of manufacturing and replacing all the swashplates in all the kits so that the release version has a swashplate that has no early wear tendency. So far we don’t see this affecting the workflow so we might be able to still have them out within the time frame but in the worst case it could delay the release by maybe five more days in case we nee to catch up with the swashplate replacement. We know it’s annoying to hear about the possibility that it could be delayed but we rather spend extra time and money on the replacement parts and ship a kit to the consumer that will have this premature wear issue already resolved before it hits the streets.

Above is a picture of the inner swashplate ring used in the Mostro until last week.

This is how the previous version was installed. The ends of the cup is flared with a flaring tool to bend the edge outward securing the bearings in place.


This is the new design. Notice how the ends are machined, beefier than a flare and the ring is split in two and threaded allowing for the installation of the bearings with no pre-load.


Here are some pictures of the new threaded parts:






Avant RC.

Mostro Maximum Battery Size,

We have been asked several times what is the maximum size battery the Mostro can handle.

Here’s two diagrams.

The Maximum size (shown 8000 mah packs )

Max size 344mm x 53mm x 71mm

The typical 12S 5000 mah packs.

Typical size of two Large 5000 mah batteries on a tray is 322mm x 53mm x 51.6mm

Avant RC.

Update on release of the Mostro

We initially expected release of the Mostro to be roughly 45 days after the IRCHA 2013 event which ended on August 5th. That would put it roughly around September 19th.

During this time we have been testing the final production version before release and recently some of our pilots expressed concern about what they had seen happening lately in other brands where customers started using overpowered motor setups in their 700 sized machines making some of their components fail.

One of the main concerns was the one-way bearing power handling under those conditions. We went ahead and sourced one of those motors and power systems and  subjected one of the production prototypes to this overpowered setup and found that under those conditions the one-way could can slip intermittently during certain maneuvers.

After this result we decided we needed to quickly develop a new pulley and use two one-way bearings instead of one to double the load capacity for this kind of setups. The result as seen in the pictures below is a new pulley that has a double the one-way bearings and since we were increasing the power handling we went to a much wider belt to add to the power handling capacity. These new parts took care of the issue and are now the standard parts coming in the kits to be released.

As a result there were several parts that were affected by this change including among others the main pulley with the double one-way bearing, the tail driver pulley, the motor pulley for a wider belt, the intermediate shaft, the boom clamps, the frames, the idler pulley posts and some other minor parts.  Due to these developments and barring some unexpected problem we need to recalculate our release date to be two or three weeks later than originally planned so we have time to make enough of the updated parts for the release kits. That would put the release date in the Oct 10th range. Thankfully those parts are all made in-house so we expect to have them done relatively quick.

One of the things we didn’t want to do is release a kit and immediately have to release a high power double one-way upgrade kit making the effective kit price be much higher and having dealer have to stock double the parts for those items. We will keep you posted of any developments along the way if needed.


Avant RC.



Clarification about Mostro heads

We have gotten quite a bit of emails asking about the difference between the Aurora and Mostro Yokes as well as between the Mostro RigidCore™ FA yoke and the Mostro RigidCore™ DFC yoke so here are some clarifications.

1) RigidCore™

RigidCore™ applies to all the heads. RigidCore™ is the dampening system invented by Avant that allows a virtually rigid head to be smooth even at low head speeds while in hover. This is attained by the development of a special non-linear compression polymer used in the dampeners and some other techniques and that’s about all we’re going to reveal about it :).
Experienced pilots that have flown a RigidCore™ head know how smooth and at the same time super-crisp and agile a RigidCore™ head is compared to pretty much all the the other FBL heads in the market. This technology is also part of the Mostro heads both the FA (Follower Arms) and the DFC (Direct Flight Control).

2) Head height.

Both Mostro heads the FA and the DFC are of the exact same height. Because we use the RigidCore™ technology we don’t need to use a softer dampener system in a FA head or increase the height of the head as it’s forced to on less advanced systems.

3) Spindle and Main Shaft diameters.

The Mostro spindle is 10mm and the Main Shaft is 12mm.

In this picture you can see an Aurora Spindle and a Mostro spindle.

4) Difference in Dampeners

The Mostro heads use a larger RigidCore™ dampener.

4) Performance differences.

The main difference between the Mostro FA and DFC rotor head systems is DFC simplicity compared to a FA rotor head system. Since there are many customers who want that simplicity Avant took a step back and  analyzed the DFC style rotor head and evolved it even further by eliminating fatigue point issues present in many designs. Some other brand designers attempting to minimize the fatiguing issues ended up with loose heads that caused the rotor head to lose its crispness. The end result with the Avant heads is that if you like the DFC style head because of the simplicity you have now a head that’s designed properly and works as intended and you’re not going to be penalized by lack of crispness, metal fatigue or other issues that other DFC heads have.

As far as performance between the Mostro version of the DFC vs. the Mostro FA Rotor heads there have absolutely no performance differences, simply a user preference on which rotor system they would like to own, with the DFC being slightly more simplistic due to the lower parts count. They both use the RigidCore™ dampening system and they are both smooth, fast, crisp and agile.

Avant previews the Mostro Line of Radio Control Helicopters


Pre-Orders for the Mostro 700 helicopters are open now.
No deposit and no charges until shipped and you can cancel anytime.
Click here to go place your pre-order at

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 is a double stage, direct-to-swash machine available with either a refined DFC head, that combines the  superior technology used in the RigidCore head with a correctly designed Direct Flight Control (DFC) system or the follower arm version of the RigidCore head for the Mostro.

Two heads from the headmasters…

Some people say that FBL heads are all the same because  the flybarless unit is the one doing all the work.  But, people who owns a RigidCore head knows better than that. The RigidCore head is a refined design that has 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  lead to a crash or alternatively, designers trying to minimize the fatigue problem that end up making the system loose enough to lose precision and crispness.

We combined the tried and true system used in the RigidCore head with polymer-based DFC follower arms that would create the perfect response  yet remain 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,  affecting the “turnbuckle” threads at the end. This makes the snapping in and out of ball links unnecessary, and allows for minute adjustments.

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.

Also, the design of the head yoke block is a piece of art. If you can make  something awesome from the engineering and performance point of view why not also make it beautiful?

The Mostro version of our RigidCore head…

For those used to the excellent response of our original RigidCore head we have good news. We have made a Mostro low-profile version of the RigidCore head. The head has all the characteristics of the famous RigidCore arm follower head with the low profile used in the Mostro mechanics. Both the DFC and arm follower head are the same exact height so the style doesn’t change. You can chose the head you like for your Mostro helicopter from the beginning.

Servo layout because symmetry matters…

We wanted to have the shortest possible distance between the swashplate and servos without resorting to weird geometries, that forces the electronic FBL unit to fight back geometry  that is not best suited to mimic what the radio control system’s gimbal does.

No matter what system  you are using, the radio’s gimbal is composed of two potentiometers that measure two angles. Those angles are the  horizontal and the vertical movements of the stick by your finger.

The best way to match that is to have symmetry in those two directions. The  most critical direction in manoeuvres is the side to side movement, which is naturally better driven via two “mirror-image” configuration servos, so that  manoeuvres like fast aileron tic-tocs are performed mostly by the mechanics and less by the electronics trying to compensate for the mechanics weird geometry. This results in  a lessened delay between the FBL gyro sensors  detection of an unintended movement created by odd geometry, and also a lessening of the correction that it has to do to compensate.

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 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.

It is not only the shape of the boom that  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  clamp pressure  is spread across a larger area, protecting the tube from damage due to excessive tightening.

Because you’ve got to stay cool…

Unlike 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 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 a 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.

Size matters…

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 made a 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 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 736cc tank for the fuel hungry 120 class of engines. This tank easily allows for very long flights and extends the pleasure part of the flight quite a bit.  The same applies for the batteries.  We designed  the Mostro with the ability to carry up to 8000mah batteries. An interesting thing about large batteries is that because of the large  number of milliamps a cheap 35C 8000mah battery can supply the same current  as a 65C 4000 mah battery can, but you get to fly around 8-12 minutes instead.

Mono what?…

This is truly a new approach that we are introducing in the market.

When designing the Mostro, we wanted to have all the mechanics connected rigidly, without flexible elements unless dampening is required. The result was the design of what we call the Mostro “Monoblock” ( single block).

In the Monoblock design, all elements of the system that affect the gyro sensing are mounted in a rigid superstructure. No part rests on the flexible frames unless it needs dampening.

The Monoblock is actually the flying helicopter.  Leaving practicality aside, you couldstrap 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  as electric motors so that even the motor plate is used in the nitro. Swapping between them is pretty simple.

A dream of a tail…

A metal version of the amazing Aurora tail system is featured in the Mostro. The large travel allows for minute precise corrections without overshoot and it’s corresponding error correction by the gyro system. Smooth and crisp is the everyday response of a well designed system.

The price is right…

Pricing for the unit is US$899.99 The first batch of Mostro kits in the 700 size will start shipping in October. You can also pre-order it at now.

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 USA-made high quality product at Asian prices.


Pre-Orders for the Mostro 700 helicopters are open now.
No deposit and no charges until shipped and you can cancel anytime.
Click here to go place your pre-order at