With the Concept DX, and the Nexus Standard having the same swashplate and scissor arm mixers, they both need a careful eye kept on them to reduce the chances of "slop" being introduced into the control system.
Little can be done with the swashplate other than changing it for the SX / SR version, which has metal balls as standard. Metal balls HAVE been fitted to the early DX swashplates, but with the easily available, and virtually bullet-proof alternatives, the work involved is better spent on other things.
Check regularly for wear on the plastic balls on the swashplate and replace it when the wear is obvious. The scissor arm mixers, situated just above the swashplate, are another area where excessive wear can take place, with potentially disastrous results.
The DX / Nexus standard mixers are carried on bushes and have a habit of coming loose. A gentle attempt at tightening the hold down bolts is all thats needed here. Don't overthighten them or the threads will strip forcing you to get a new mixer base and / or mixer lever set.
Upgrading to the SX / SR ball-raced mixer levers, and at the same time fitting metal balls is a common thing, and doing this gives a trouble (and wear ) free system. Highly recommended, although the upgrade is fairly costly.
There`s been a variety of Rotor Heads on Concepts over the years, all of which are good for the job they were designed to do. The DX for example had very high flybar authority and heavy (aluminium) paddles. This made the DX an easy to hover machine, and one which was almost unaffected by gust of wind. Good for first circuits and auto`s, even with the original super light moulded plastic blades.
No thrust bearings meant that installing heavy glass or carbon blades could cause the blade holders to lock up at high revs. This is no criticism of the Rotor Head design, as it was never intended to be abused in this fashion. That was the job of the SX Rotor Head. The next "generation" of Rotor Head was found on the later SX.
Lighter plastic paddles for a faster response to cyclic commands, and a lower fly-bar authority, although this was off-set by having re-designed blade holders, giving greater pitch movement for the given fly-bar / swashplate displacement. The new blade holders also gave a much greater collective pitch range, allowing for inverted flight with no modifications.
The pitch arms on the SX rotor head are closer to the centre of the head that the DX / SE holders, giving a greater pitch change angle for the same amount of control rod movement, so doing a direct swap could result in something you WANTED, or something you didn`t EXPECT.
If you wanted an increase in pitch range, you got what you wanted, but if you were changing the holders through "necessity" and bought the first pack on the shelf, then you could`ve bought SX holders for your DX / SX without noticing. (Until you went flying that is). A few degrees of negative is NOT recommended when you`re learning to hover.
With the coming of the SR (T and X), the 2 piece blade holders of old were replaced with a new single piece item. The pitch arm geometry was making it necessary to redesign the collective pitch slider to still attain the pitch range needed for extreme aerobatics.
The new slider featured a plastic outer shell, and was shorter than the SE / SX item to allow for greater vertical movement on the rotor shaft. The new slider required a metal ball on the operating bell-crank which reduced wear and further increased the life expectancy of the SR over the previous models.
With the introduction of the SR range, the rotor diameter was increased, as was the length of the tail boom. This change resulted in lighter disc loading and made the SR fly more like a 60 size than a 30.
This helicopter was getting to be something REALLY worth owning.
As the boom got longer, the tail shaft got thicker and stiffer. (Nice) :-)
The drive wire diameter was increased from 1.6mm to 2mm making for a longer life and more solid drive to the tail rotors. The tail rotor holders were changed (at last) to twin ball-bearing system in favour of the original single thrust bearing. This cured the very common "thrown" tail blade problem that the original design allowed. It`s now possible to fit "after-market" tail blades, some of which are heavier that the originals, without the fear of swallowing one during a flight :-)
Fitting the new SR tail blade holders is recommended for ANY Concept owner for the increase in reliability and precision.
During the life of the Concept range, improvements have been made to all areas, not least the frames and the radio tray.
As the "requirement" for a stronger more rigid structure became apparent, Kyosho dutifully met the demand, first with a new frame set with strengthening webs included, then with the servo tray which included "stand-off" pillars for the throttle and collective servos.
This increase in rigidity, coupled to the ball-link set (available as an extra) for the control rods resulted in even more precision control. Now all that was left was the under carriage. That was re-engineered too, giving a higher stance on the ground and better tail rotor/ground clearance, so the tail blades lasted longer and it was even possible to use foam filled carbon blades without the fear of using a pair each weekend.
Although the new undercarriage held the back of the helicopter off the ground much better than the original, it was (and still is) TOO rigid, which results in broken struts in the event of a hard landing, particularly in cold weather. Something in between would`ve been better, but thats life. You either have it stiff enough to snap, or too soft to be of much use :-)
So...Since it`s introduction in the late 80`s the SR-X had grown from the basic DX trainer into a machine capable of extreme aerobatics, yet is still affordable and still usable AS a trainer. This was in response to the way the helicopter market had moved, and credit is given to Kyosho for moving WITH the market and still catering for the new comers with the introduction of the SR-T and the Nexus line.
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