Star InactiveStar InactiveStar InactiveStar InactiveStar Inactive
 

With the weather not being helpful and being confined to being indoors I thought now is the time to do some just jobs and modifications I have had on the backburner for a while.  I am surprised at how quick they can mount up especially when you have quite a large number of aircraft.  There is the 4 foot wingspan Ripmax Mustang to figure out why it flew like a heli and was left in the Club container for nearly a year, when the MK1 I had flew great from day one and lasted 2 years plus, and that includes two Bygone Days Events piloted by WMAC member Dave Bright who only knows full throttle and off.  Then there is the MX2, of which I have four, two orange (Century) and two blue/green (Hobbyking).  The former are Century UK versions and the later are Hobbyking versions.  Both these models are discontinued as of May 2014 although there are still stocks around at time of writing.  Limited spares from Century but none and never was from Hobbyking.  Originally I bought two models on the basis that I would have one for spares as I watched the amount of spares available reducing quite dramatically.

 

This story is mainly on upgrading and modifying the MXS.  Although the Mustang was sorted (I think) easily.  Studying the motor mod I had done to use a brushless, I came to realise that the thrust angle was wrong.  It had upthrust which I had built in but I had glued the motor mount on upside down. Doh!  A few washers sorted that issue.  Waiting on fine weather to test it again.

So on to the main story.  My plan was to make a team of MXSs to fly together in pairs.  A bind lead extension from each so pilots with Spektrum/JR DSM2 could fly them.  I had three Century MXs (one damaged but repairable) two brand new and two Hobbyking MXs one damaged and one new.  The plan was to use the damaged models for spares!

The MXS from Century (there is a review on the website regarding this model - http://wimbornemac.org/stories/reviews/46-max-thrust-mx2     and http://wimbornemac.org/stories/workshop/86-century-uk-mx2-issues) has some differences from the Hobbyking version.  Both the  Century models fired up with no issues albiet the arming tone (beep) is not very loud and no nice tune.  The Hobbyking models, first one out of the box the motor would not run.  Tested motor on a known esc and ran.  OEM speed controller failed.  I stripped the shrink back and re-soldered main connections in case there was a dry joint.  They were the output capacitors, power leads and output diode.  No joy there so junked it after snipping off the power leads, ferrite ring.

 

 

 

 

1. The rudder on the Hobbyking has only two hinge pins relying on the tail wheel assembly to support and keep in line with vertical fin.  Century uses three live pin hinges.

2. THe ESC (speed controller) on the Hobbyking is unbranded although shrink-wrapped in similar colour, blue. Century's version displays Topfire brand and is listed as 80 amp.  I assume that is continuous and not burst!  On some forums users have esc failures/burnouts mainly on Hobbyking versions.  Albiet you have to bear in mind that these cheap ARFs will have cheap hardware.  Having said that the airframes are very well made and fit together accurately most of the time.  Being EPO (foamies) they can be patched up fairly easily with UHU or epoxy.  Decals can be peeled off if you have the time and patience and the airframe can be re-sprayed with common acrylic car aerosols.

3.  Rudder and elevator servos in the Hobbyking are near standard size, unbranded, whereas the Century has mini servos, unbranded.

4.  Wing servos are micro and unbranded on both models. (Although one of the Century models had servos branded Topfire, same as the OEM speed controller)

5.  Motors are similar in size although Century are red and Hobbyking a bronze colour.  The cases are slightly different in design but the 6mm prop driver is identical.

Having had great flights with the original MXS from Century I thought it maybe time to upgrade these models with some more reliable components, branded servos and speed controllers that I have had no issues with including a few changes on the airframe.

 

 

Power System

Working on the Century "Orange" versions.  First job is to replace the ESC with my favourite brand, Hobbywing, these being 100amp Platinum Pro. These can be programmed off model.  100 amp a bit overkill but then they will run very cool.  I had two of these at hand anyway.  I had to change the bullet connectors on the OEM motors from 3.5mm to 4mm to match the ESC.  The OEM speed controllers had extra long battery leads so on the 100A Platinums I had to extend the leads, making up some extensions with 4mm connectors.  (Rather this than changing the leads completely and thinking of further use in other models where long leads are not required.  On arming the motors now play a tune too!

I have kept the original motors as I have not had any issues with these yet.  After replacing the motor lead bullets with 4mm connetors I also had to turn the motor 180 degrees on the metal mounting to accomodate a better securing of the ESC.  The motor leads now exit from the top rather then the bottom.  The silicon output leads on the Platinums are longer and flexible compared to the stiff OEMs. The leads are now well clear of the rotating case.

The OEM prop driver is made specificaly for the model allowing the spinner back plate to locate on machined flats.  The 4 bolt prop driver shaft looks like it would bend easily on a nose-over, reports from other forums suggest this is regular hence the short supply of spare parts.  To get round this I wanted to use a driver with a 8mm shaft, also because nearly all my electric models use 8mm shafts therefore lots of choice with props either used or new and sizes.  Because these model motors appear to be peculiar to these models it took a lot of researching and trials to find a prop driver to fit.  There are many prop drivers around but not all are available as spare parts and not always in stock.  I had tried AXI adaptors and Emax but they either did not sit down correctly or the bolts holes did not line up.  However, I think I had found who makes these motors or very similar motors.

On Giantshark they sell XYH motors, these are very cheap, although there have been some good reports for what they are.  These 600Kv (45amp continuous, 3 - 6 cells,  1300 watts) motors looked virtually identical to Century's MX motor AND they came with a prop adaptor and a compression cone too.  The price of them is only a bit more than some decent prop drivers.  I bought a couple and could use the motors for some other project in the future.  The 8mm adaptor drivers fitted the Century motors.  Now any spinner backplate will sit flush against the driver.  I use Irvine spinners, lightweight aluminium backplates and quality spinner cones.  Through experience I will fit 13 x 8 e APC props requiring the spinner cone's prop exits to be enlarged slightly.  Irvine make this easy for you by reducing the thickness of the plastic at the exits.

On the Hobbyking MX I have replaced the OEM motor with a spare Century one (the motor mounts are identical on both models).  The 8mm prop adaptor I used is not from a XYH but a Century P51 driver.  It does have a slightly raised machined key for the P51's spinner but for now I'll suffer with it.  Probably get a member with a lathe to turn it down for me at a later date.

 

 

 

 

Rudder - Elevator

I have left the rudder servo as is.  I don't intend to do extreme manouvres or 3D and so far I have not had issues with the servo previously.  However, back in the early days I did have a stripped elevator servo which was replaced with as HS225HB, Karbonite gears are 5 times stronger. less noisy and wear less than metal.  With this im mind I again have replaced the elevator servo with HiTec.  This requires a couple of ply strips glued on the servo tray to make for fitting the slightly smaller Hitec.  I also did away with the adjustable servo rod connector on one of the models, opting to connect to the servo arm using a Z bend and making minute adjustments via the clevis at the elevator.  No chance of slip and minimum slop too.

The rudder pin hinges are plastic throughout so before final fitting of the rudder I pulled these hinges out using the "dentist method", get a good grip, twist and pull.  They came out cleanly.  They were replaced with Robart 1/8th steel pin hinges which also are slightly longer therefore more area for the glue to grip on.

 

 

 

 

Wings

Wing servos are mini class and after cutting through decal film carefully prised them out of their slots.  They are glued in with China's version of UHU Por!  Amazingly these OEM's are the same size as HiTec 65HBs (Mighty Feather). The HS65 is a very popular, capable servo with Karbonite gears and high torque for it's size.  These were fitted into the wings.  The only extra work here was that the HiTecs needed 300mm servo lead extensions.  The OEMs obviously were specially made as they had extra long leads and on very light cables.  I have kept these cheapos for now, they might do for a small cheap model or slope soarer, maybe!

The cockpit has a tendency to fly off although it is held down at the rear using a magnet on the Century's and a plastic clip idea on the Hobbyking.  The airflow through the fuselage pushes up the canopy as it appears that the air exit holes on the underside cannot cope.  What is needed is a latch idea or a locking pin.  Latches of any description were in short supply at time of writing so I plumped with an idea that anothe rmember had used with great success.  At the top of the fuselage just behind the canopy edge a small rawl plug was glued in using epoxy.  Into this plug was screwed a self tapping screw hold down a servo arm, tightening down just enough to cause resistance.  To remove canopy swing arm clear and pull up canopy. Simples!

 

Fuselage

After some experience with previous models I found it necessary to encourage longer "lifespan" by adding some stiffening to the fuselage.  Where the firewall meets the canopy deck area there is a tendency for a split in the foam here after heavy landings or roll overs.  Also in the area around the front wing slot (see image) it will also split here after some use or less than acceptable landings or running over rough grass surfaces.

In the case of the latter this was overcome by cutting out some 3mm ply and epoxying over the area in question (See image)  Although I have not done this at present, in the case of the firewall issue, I am going to add 3mm ply to the firewall and brace the wing ply plate to the firewall with a triangular fillet.  This will entail creating a slot in the canopy floor to allow the fillet to slot in.

There have been issues with the ply motor mounting plate which is embedded into the fuselage.  This is due to hard nose-overs or crashing into the terra firma.  It cannot be accessed so if you have a problem with it becoming "floppy" within the fuselage, suggestions are to position correctly and fill the consequential gap with Gorilla glue and also drilling out a plug from the top of the fuselage down to the ply mounting, engaging a dowl and glueing in and then add a bit of the foam plug back into the hole and painting over if you need too for cosmetic reasons.

Update:  07/12/2014

Although all the MXs have kept their rudder servos as OEM with no problems to date and then they prove you wrong!  Prior to the second flight after some downthrust was added to MX No.1 (the one with the black cowling) the rudder servo decided to strip it's gears on pre-flight checks.

The rudder servo was replaced by a HiTec HS225MG.  This entailed widening the servo mounting hole by a few millimeters and adding two pieces of ply at each end to close the end gaps a little and allow for new mounting screw holes.  I discovered that the original servo arm fits HiTec mg servos but not Hitec with plastic drives.  This saves a lot of scrabbling around finding a suitable replacement arm too!  Gaining on this experience I will inevitably fit all four of my MX foamies with Hitec MG servos for rudder.

{jcomments on}

 

 

You may also like....

Related Articles

wmac logo 30px -