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Full 3D Printed Airplane – Chapter 1 (Printing)

I’ve had a 3D printer now for a couple years and printing some add on accessories for my RC aircraft was the main reason I purchased it.  Cockpit details, air scoops, replacement plastic parts for broken scale details like antennas and the like have all been projects I have tackled successfully using my 3D printer.

My particular printer is an Ender 3 with the only functional modifications being a v4.2.7 motherboard, a glass build plate and some updated build plate springs.  The base unit can be bought several places and I recommend it as a beginner hobbyist platform.  From what I have seen, it is widely accepted as a great device in this role.  Here is my link to purchasing the current version of this printer from the Creality Store via Amazon.

At the time I purchased it, I was not particularly interested in or really aware there were very many options for printing a full RC airplane.  What I had seen were overweight, ugly airplanes that seemed to just barely fly.  After a time I heard about a new material that made it more feasible to print something that might actually approach a reasonable level of functionality… something called Light Weight PLA.  Here is a link to what I purchased.  There are other brands out there but eSun seems to be a well accepted as a quality product and I don’t have enough experience to accept the challenge of sorting out more factors than I needed to when I was embarking on a new adventure so I went with what seems to be a premium material.  Here’s a link to that:


So of course I purchased a roll of filament and quickly decided it was going to be to complicated to set up my printer to work with it.  Also my printer had such a small print surface that I surely couldn’t print anything of any size… so the filament went up on shelf to gather dust.  The reality was somewhat different, but I wasn’t wrong that with my level of knowledge at the time, I probably wouldn’t have had good results.  

Fast forward a year (or maybe 2??) and I happened on a YouTube video showing a really nice looking airplane that was 3D printed!  This got me thinking, maybe it was time to revisit the idea.  I had learned a bit more about 3D printing and felt I was ready to take the plunge.

So for a week or so, most of my recreational video watching was of 3D printed airplanes and fair amount of web research turned up some interesting information.  There were quite a few sites that espoused particular parameters and setups to get successful prints for LW-PLA and there were a number of free designs around.  What finally made me open the box was when I came across a free download from Eclipson. 

The 3D printed aircraft designs on their site are exceptionally nice looking… rivalying the available ARFs on the market from even the top tier companies using more traditional techniques.  They do charge for these files, but the prices seem very reasonable for the level of quality they appear to represent.  Their website is very well built and presents their product very nicely with lots of pictures and available information. 

Time out for a rant… feel free to skip to the next paragraph.  The only thing I wish for, and I may be completely alone here, is a nice manual to help me build.  They do a one page sheet that has a lot of information packed into it that is very helpful, and there is a good build video but for me personally, I hate build videos.  Especially videos with no narration or discussion like this one.  This one is as good as any I’ve seen, but I would much prefer a well illustrated and written step by step assembly book.  I’d even pay for one in addition to what is available if it was well done.  I find it hard to keep stopping  and starting a video… finding a way to backup and find that one part I’m looking for… stopping at just the right point to see what I want to see… Its all just a PITA for me.  I know some folks would rather have the video… I’m NOT one of those.  OK, rant ended.

Best of all, by all reports, the Eclipson aircraft fly very well.  What really got me out of the starting blocks was that they even provided ready made Gcode for their models, preset to work on my exact printer!  Its like just feeding in the files and hit print and out pops an airplane!  Ok, well maybe not quite that easy but it does get you around having to learn all the parameters necessary to print good quality aircraft parts using this material.  Certainly tweeking their settings a bit could make the parts even a bit better, but what I found was using their exact settings produced parts good enough to actually function.  Or at least it appears so to me.  I don’t mind learning about all the parameters and figuring out how to dial in my printer to produce my own good LW-PLA parts, but I like it even better if I can do that while another perfecty usable part is being produced!  Icing on the cake, they have one airplane you can get the files for simply by signing up!  This airplane is the Wolf.  This RC design is based on a german glider design first produced in 1935 and motorized for RC use.  So I signed up and downloaded the files.

I began printing parts from the supplied Gcode and occaisionally I’d tinker with my profile and try printing my own part just so I’d have that ability in the future and because in one or two cases I realized I could print the part just a bit better if I tuned the settings for my particular printer and material.  For instance, my eSun White PLA (that I used to print a few parts that needed more strength… per the instructions) happens to print better at 5 or 10c higher temp than the supplied Gcode is setup for.  So I pulled up the STL file provided and used my profiles I generally use for PLA+ and printed out those few parts with my own Gcode.  I suprised myself with how well those parts printed out.

Here’s some obligatory “parts being printed” photos..  All of these are using the eSun LW-PLA+.

First section of the port side aileron getting underway…

Here’s another section of the aileron

And this is obviously the vertical fin.  An exceptionally nice print if I do say so myself.

Up to this point, I had only printed some of the smaller parts of the airplane.  But if I want to have an airplane I have to tackle the big parts next and in my experience, big parts take a lot of time to 3D print.

I’m not typically impatient when building an airplane.  I don’t mind if a project is sitting on my bench for a while waiting for some necessary parts to ship in or whatever.  I can always find another project or a different aspect of this project to keep me busy.  I will admit however that I was a bit troubled by the thought of how long it was going to take to print all these parts.  I have done some moderatly large parts on my printer before that took 14 hours or more!  Looking at the airplane I was afraid weeks of printing overnight would be involved.  Luckily, once I tried it, nothing could be further from the truth.  I quickly realized that because of the way you print these, there is very little or no supports needed/desired and not much infill either.  This results in parts printing much faster that I expected.  I printed the first dozen or so small parts over a weekend and I think I got all of the LW-PLA pieces (by far the largest part of the airplane) done during a single week of just part time printing while working on other things.  Honestly think I could print all the parts in 3 days now if I really tried.

The final piece or two I needed to print, was the tire and hinges.  These pieces need to be printed  from something a bit more flexible and in the 3D hobbyist world that means TPU.  TPU is about the closest thing to rubber that we can print on a 3D printer and it demands yet another totally different set of printer settings.  After reading a bit on the proper settings, different brands and types of TPU available, etc… I decided to give it a try.  I had gained a little confidence through the process of printing the LW-PLA so I made the leap.  Another order to Amazon and the very next day I had a fresh role of eSun TPU95A in gloss black.

With my very first try, aided by the suggested settings from eSun and a small tweak or two based on articles and videos on line, I had my very first TPU print… a test piece based on a video from a youtuber named CHEP.  It looked great and did point out one small wall adhesion issue so I tweaked one more setting and tried printing my tire.  It worked well enough on the very first try.

As I went through and “post processed” the prints, removing some skirt material and sanding a couple of spots, etc… I did manage to damage a part or two and had to reprint a couple as a result.  The parts aren’t perfect and I have some ideas about what I might try to do differently if I do another airplane down the road, but I think it might actually fly some day! 

After assembling the needed RC gear and a few other necessary supplies (more on that in a follow on article) I had this pile of parts sitting on my bench… time for assembly!

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3D printing add-ons for the Freewing JAS-39 Gripen

I recently acquired a Freewing JAS-39 Gripen (Griffin for us English speakers).  I’ve never had much interest in EDFs but why I have it and what possessed me to buy it is a topic for another post.  For my purposes here, it is enough to say I have one and I wanted to make it look a bit more formidable by adding some weaponry, help out with balance with a little added weight to the aft of the balance point and just add some scale touches at least for display purposes.

Luckily, there are some readily available STL files.  STL files are the output of a CAD program and are what you need to input to the slicer software which produces the G-code files.  The slicer software parses through the STL file to decide what instructions to send to the 3D printer to create the shape and creates a list of those commands which is your G-code file.  So, having the STL files means the hardest part of 3D printing what I want (the actual CAD design work) is done for me!

I printed a couple of Iris-T missiles first using some white eSun brand PLA+ filament.  The Iris-T is the European equivalent to the US Sidewinder missiles.  Both are extremely smart, relatively short range heat seeking air to air missiles.  The Gripen can carry either but I decided to start with the more “native” weaponry.   These are almost always carried on the wingtip hard points on the Gripen and since the wing tip hard points are already in place on the model, it made sense to start with something for those stations.  They came out pretty well with only a little bit of stringing and just one or two very slight imperfections.  I was pretty happy.   There are keyhole slots in the end of the rails on the wingtips of the Gripen and there are mounting rail STLs available so I printed a few of those as well.  The missiles have a flat spot designed in where you can easily glue these to the missile.  Once that was done, with only a little sanding/carving/cleanup I was able to slide the missiles onto the wingtips.  Here is a pic of the IRIS-T on the wingtip of the plane pretty much fresh off the printer with just some minor gluing and sanding.  These are 1/9th scale just like the airplane.

There are a couple of nice things about having these on the plane.  First, they add some needed tail weight.  The Gripen has a very swept back Delta wing so the wingtips are far back from the desired CG so while not the ideal place for extra weight, its not a terrible spot either. Second, they cover up the sort of ugly wingtip “rails” with some nice eye candy.  And third, I’m thinking there may be some wingtip strikes with the landing gear being fairly narrow as they are on many jets, so they can act as wing tip protection to some extent.  I can print another missile or fin or whatever, but the wingtips of the airplane would be much harder to reproduce and replace if they get beat up or broken.

Next I tackled some Meteor missiles.  These are long range, radar guided air to air missiles.  In real life these things are around 13 feet long, so scale they are around 16″ long.  These are massive and carry a big warhead.  Imagine a telephone pole coming at you with a big bomb on the front… at multi-mach speeds!  Used properly they are on par with the best such weaponry out there.  With the right launch parameters and guidance these can be fired from 100+ miles away!

These are generally carried on under wing pylons on the Gripen but the model doesn’t have any built in hard points for those so I had to print out the keyholes/hardpoints and the pylons themselves and get those mounted on the plane.  It took some carving in the wing, careful alignment and slowly digging a bit deeper until I had what I wanted then glued the hardpoints in.  With those in place I could slide the pylons on and lock them in place then slide the missiles in place under the pylons and lock them in and bingo, we are in business.  Below are some snapshots of that process and the results.

 

 

 

 

 

 

 

This is the outline of the mounting socket as I’m starting to remove just the skin/paint in preparation to route out maybe an 1/8 inch or so of foam so I can glue it in..

This is the socket in place.

 

 

 

 

 

 

 

 

 

 

 

 

The tape attached to the pylon is adding some pressure after the glue is in place and just starting to setup nicely.  It looked a little off so needed some pressure to get it to sit level in the wing.

Here’s the whole thing after I hung a meteor on it… starting to look pretty good! 

After I got this far I was down to needing sanding and painting so I started doing a bit of research and found a variety of paint schemes available and went to work.  The meteors especially varied a lot, so I took a bit more license with those and stayed with the white scheme but the IRIS-T is almost uniformly and almost completely gray so I decided to reprint those so I wouldn’t have to do so much painting (I hate to paint!).  Then I took advantage of where some of the color bands are to cover up some of the glue joints with pin stripe or color bands on both missiles.

Meteors (on left) and Iris-Ts (on right)

I’m sure for the true scale guys these are nothing special but I think they add a lot to the look of the airplane and the effort was not huge.  For me, having the 3D printer (and the efforts of the guys who first did the design) made it possible to really upgrade the look of the airplane with minimal effort.  And no one has anything that looks like these!

Of course, it doesn’t end here.  I have engine inlet and outlet covers printed as well and I’m eyeing some fuel tank designs I’ve seen…

So if you are wondering if you need a 3D printer to add a little extra something to your hobby… the answer is of course, NO.  But I recommend it.  There’s a lot you an do that will add that little something extra to your favorite bird.  I expect to do a bunch more of this in the future.

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Couple of new “to me” motor vendors… specs

Electric motor specs available

I recently was involved in a conversation that started out bemoaning the fact that Horizon hobby often doesn’t supply much in the way of specifications on many of their electric motors, when someone referenced a couple of sites that provided a plethora of information about that particular electric motor vendor products.

I have used ecalc to help me predict power system performance for years but that doesn’t get you around a lack of decent information and for those who for whatever reason don’t have access to that tool or have trouble understanding how to use it correctly, information from the vendor like those below has a very high value.

I haven’t tried out these motors for myself but I applaud the disclosure of specifications along with predicted (maybe tested) test results with a variety of propellers.  This really allows you to pick a setup that does what you want to do without a lot of trial and error as well as allowing us to get the most out of the motor, again without a lot of trial and error.

So here are the links to these manufacturers sites.  With this sort of available information I may have to give them a try.

Leopard Motor Data Chart

Badass Motor Data Chart

 

 

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Aces High P47 Retract issues and repair

I’ve really just gotten started flying my Aces High P-47, with maybe 6 or 8 flights as I figure out the ideal balance, throws and flight envelope for this airplane.  However all of that got a bit sidetracked a few days ago when my port side retract refused to retract after a landing.  I had to cycle it 3 times to get it to extend during that last flight and after the landing it was just totally unresponsive.

So back on the bench, I started trying to troubleshoot the issue.  First off, you have to understand how everything goes together.  The retracts in the P-47 are simple units that require a separate controller unit that looks like this:

The retracts each only have 2 wires, a positive and a negative.   Each retract unit plugs into one of the back wheel  connections on the controller.  The controller has one servo lead for power and signal input to the controller.  This plugs directly into your receiver on whichever channel you chose to control the retractable landing gear. 

In my case, in order to simplify wiring to each wing, I have a wiring harness that allows for a single multipin connector to go to each wing rather than separate servo wires.  Since the harness consists of multiple wires and crimped on pins, etc… I first decided to eliminate the wiring harness in order to eliminate any possibility that a bad wire or crimp connection in the harness was the culprit.  That accomplished and no change in operation I tried swapping the port and starboard connections.  The failure still appeared to be in the port side unit.

At this point I got in contact with Extreme Flight to see what my options were.   I provided my troubleshooting results and awaited a response.  Although the response took several days I did eventually get an email back from a support person who questioned if I was certain the retract unit was failing and not the controller.  At this point I arranged a call with the support person and walked them through the steps I had taken and they agreed that I needed a new retract… which is unfortunately on back order… with no predicted ship date!!

They did agree that the retract set should be replaced under warranty and sent me confirmation of the order… but of course I was not hanging this plane up for the season without a fight!

So moving into some real testing I removed the offending retract from the port wing and the controller from the body and fished out a spare A123 flight pack and my trusty servo tester.   (Note: when I pulled the retract I was sure to use the retract wire to pull a string from the wing root out to the retract area so that replacement would be simple. ) 

First using the starboard wing to check my test bed, I confirmed I could cycle the working retract without an issue.  During this test I noticed that the controller has LEDs that cycle from green to red depending on which way the controller is trying to drive the gear.  The LED goes off once the retract hits its limits and (I presume) the controller senses an end point has been reached.  I’m guessing it senses the spike in current as the motor stalls and automatically shuts down.

I also measured the voltage being supplied by the controller and verified that the controller simply flips the polarity to the motor in order to reverse the direction when the servo signal goes from one end to the other.  Following up on that I started trying to establish whether the continuity of the wire was good all the way to the retract motor.  I stuck a couple of very fine pins into the wire up near the motor and tested for continuity from the connecot to that point.  This established both wires were good to that point so it was down to either the motor being bad/burned up/open or just a bad connection to the motor.  I measured the resistance of the complete working retract in the other wing and established a baseline of about 4.5 ohms was a normal working unit.  Testing the bad unit showed infinite resistance/an open circuit.  After I did this, I quickly realized the red wire had indeed broken loose inside the “can” that surrounds the motor and I was able to easily pull the wire out of the entry point to the can/motor housing.  The problem now was that the motor sits inside this can and has no screws, set screws or other obvious way to get it open!

Deciding that I had nothing to lose I started disassembling the retract mechanism.  

Once the screws on one side were removed it was simple to separate the motor assembly/screw/trunnion pin from the remainder of the servo.  Note that there are  ball bearings in the sides of the assembly so while mine easily stayed in place, I’d be gentle and try not to dislodge those if you ever have reason to dig this deep!

Once the motor can was loose in my hand I realized that if it were going to be possible to get inside the can and get to the solder connection point on the motor it had to be some sort of split/friction fit or two parts had to twist apart somehow.  I first took a razor knife and tried to split it along either of two lines around around the enclosure… neither yielded to my efforts.  Finally I grabbed the center of the can with a pair of pliers and tried twisting either end.  Finally the end nearest the trunnion pin rotated a bit and I was able to unscrew that part and slide the motor out from inside the rest of the assembly.

At this point it was possible (if difficult to manipulate due to just the small size of the solder tabs on the motor and gauge of wire) to re-solder the wire and test the operation.  Hooking the controller back up to my servo tester and operating the retract motor was again attempted and all went well.  Keep in mind the motor will just run continuously as there is nothing stopping the motor so no current surge to tell it to stop.  This is normal/expected operation in this state.  Also note that there is a spacer in the end of the can where the shaft extends out to the trunnion and the shaft of the motor is keyed into the threaded shaft so be careful when reassembling not to lose of those parts and to align the motor carefully so its keyed shaft fits correctly to the threaded rod end as you put things back together.  I was concerned that the wires might touch the can and short out the controller output as there is no obvious protection from this happening but it didn’t so I’m assuming the inside of the can on that end has some sort of clear insulator or other mechanism to prevent it even though I never figured out exactly what it is.

Once I completely re-assembled I took some steps to protect against another failure due to motion of that wire or strain on the wires.  First I coated the entry point with liquid electrical tape and let it set up.  

As you can see by the scars on the can, I marred it up just a bit with my pliers during the process but now that you know that the end cap nearest the pivot point is the one that unscrews, you could probably avoid this with some care and perhaps a wrap of tape around the can in strategic locations when disassembling.

Once that was accomplished (on both retracts) I mounted the retract back in the wing, used the pull string to get the wire properly routed.  At this point I pressed the wire up against the balsa sidewalls of the wheel well and applied a bit of glue to make sure no further physical strain could be applied to the wire at the entry point to the can.  As shipped that is just an entry hole with no grommet or strain relief of any type so I’m being doubly certain to protect it moving forward.

How will it hold up?  Is this the end of the retract issues on this bird??  Well we shall see, assuming I manage not to do anything stupid during my flights.  Let’s hope for the best.

I’m only now realizing that I have no idea what keeps the motor from spinning around in the can… I didn’t see an alignment pin or flat inside the back of the can etc… but it would seem there must be something there besides the wires that can’t rotate… I’m guessing there is something in the front area that accomplishes this.  Well that’s an investigation for another day and probably only if/when I get the new set or have to work on these again so lets hope that remain a mystery!

If you have this airplane or the Aces High FW-190 from Extreme Flight that looks to use similar retracts, I’d definitely address some sort of strain relief on your retracts to avoid similar issues.  Blue Skies.

 

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Seagull Models T-6A Texan II

Early in 2020 I was wandering through a huge swap meet over in Dayton, Ohio and I chanced across two new-in-box 60″ish” size Seagull Models T-6A Texan IIs…  One was made up in a beautiful Red/White/Blue/Black and Silver scheme and the other in more of a gray camouflage pattern. 

Model Airplane News - RC Airplane News | Top 10 Warbirds of the Year — RC Heavy Metal Reviews

I admired the models and quickly decided they were not for me.  I kept telling myself that a T-6A is a jet trainer and surely would be fast and heavy and besides, what did I have for a power system?  They are a bit more unique though and the red/white/blue scheme sure looks nice… I almost didn’t make it past the table when the owner made an offer to let me have one for what couldn’t be more than 1/2 of the cost of a new model!!  I stuck my fingers in my ears and ran to the next set of tables… 

Fast forward a couple hours later and I’m about to finish my first lap around the meet when I noticed what looked like a NIB Hacker motor.  The gentleman explained he had bought it as a spare that he had never needed.  I had some recent experience with another Hacker that was part of one of the best E power setups I had ever operated so this looked tempting.  Again the price was right and this time I didn’t try too hard to resist.

Now armed with a high powered 6S power system (1250W continuous and able to easily handle 1600W) I realized I had the exact motor for the Texan II.  After a brisk walk and a quick negotiation I had the airplane as well.  Wait, what had I done!?  It is still a jet trainer.  I like lightweight, overpowered, nimble and aerobatic aircraft with simple fixed gear!!  Why did I buy this beautiful, sleek, heavy trainer with mechanical retracts??

Over the next couple weeks I worked my way through assembly of the T-6A.  Since my expectation was that this airplane would likely end up being something I’d only fly once in a while and probably end up selling to those who have more appreciation for “war birds” I decided to make sure I added most or all of the scale details (something I might normally skimp on) and try not to spend an inordinate amount of money assembling all the pieces and parts I would need.

With that in mind I installed the pitot tubes on the wings, the anti-static rods on the elevator  and even took the time to make a color change on one of pilot busts so that they wouldn’t look quite so much like twins!  I also took some extra time to apply the decals and even did some “base layer” covering work under the star and bar logos to help cover up the color change underneath and not allow it to show through.  I also opted to install the mechanical retracts where I would normally have spent the $300+ to purchase electrics.  The mechanicals are going to cost me more like $50 to install, mostly the cost of a retract servo.

The first pleasant surprise was how well the retracts worked with nice direct routing of the linkages.  Ok, so I’m not a big fan of the plastic inserts for the wheel wells, but with some care they at least are a decent color and fit.  Again, I’m not a big fan of a once piece wing but the upside is the  simple retract linkage geometry and the need for only 1 servo to service both mains.

Once I got it all assembled I was back to the overall look.  I love the lines of the Texan II, the PC-9, and similar aircraft and this one has a great color scheme… but I wasn’t getting my hopes up on flying characteristics so with little fanfare I took it out to the field and with only a couple of friends present I flew it for the first time.  All I can say is wow!  This thing is certainly a warbird.  It’s not light and flies much better with a little more throttle… she’s no floater… but it feels like it is on rails in the air and has enough wing to handle the weight so just by keeping a modicum of speed on the bird, she flies great!

Since that day I have probably put 30 more flights on the airplane and I’ve had zero issues with it.  It flies really well and with all the scale touches it looks great in the air.  I don’t recall flying it without someone commenting on how nice it looks.  I’ve switched out to a very slightly less efficient 4 blade propeller for even more appropriate scale looks on the ground and I’ve had a few of the scale details get broken during transport and assembly but otherwise it has so far been a great airplane.

I created some protective covers out of foam, cardboard and tape to protect several of the protrusions… antennas, static rods, etc… and had to create some replacements once in a while the flight characteristics have been very pleasing and I do enjoy flying it… and lets admit it… the comments and attention it gets!  I have a Styrofoam holder (cut with a foam cutter from a shipping container for frozen food) for the body and a wing bag for the one piece wing that helps keep it all safe during transport and those have cut down on the issues.

So in summary, I’d recommend the plane to anyone interested in a nice psuedo scale attractive airplane that wants to get into warbird type aircraft.  Its a nice step from sport planes into that realm and you will enjoy flying it as long as you remember what it is and fly it accordingly.  3D is not ever going to be its strong point, but sleek lines and scale aerobatics are done with ease and look really nice in this bird.  It has earned a place in the hangar at least for now.

 

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3D Printing… Handy tool for RC airplane work? Or maybe just another hobby to eat up hours!!

After a sad end for my Top Flite P47 due to radio failure, I have been in the market for a replacement and started reading about the Hangar 9 20cc P-47 ARF.  While doing some research I chanced across some posts talking about printing a new cockpit for the bird on a 3D printer… and the wheels started spinning.

Of course I know that 3D printers are too expensive, take a special brand of wizardry to operate, etc… so I inquired with a friend of mine who has perhaps 5 of these magical machines.  So when I asked if he would be willing or how much it might cost to print out these cockpit he response was link to a large online retailer for a 3D printer!!  Hmmm… seems like a hint.  Here is a link in case you want to follow me down this particular rabbit hole.

 

The first thing I noticed is that this particular printer (at the time I purchased it) was under $200…. far below what I had expected.  After another week of research and self justification… I placed the order.

I’ll save all the trials and tribulations of assembling the printer, testing, adjustment, more testing, etc…  I decided not to have a go at printing the cockpit interior immediately.  Soon enough I started finding other uses for the new printer within my RC hobby.  Here are a couple of examples…

First, I struggled with getting an electric nose retract to work for the tail retract of the H9 P-47.  The geometry just didn’t work with the provided linkage so I began creating a replacement, and after a few iterations I came up with a design that worked for me.  Being able to change dimensions and reprint or print 3 or 4 slightly different designs and test each really made it possible for me to get this working!

Here’s one of the early iterations..

And here it is installed on the aircraft for testing.

Also for the P47, there was a pattern available to help guide the wing wiring into the fuselage for easier assembly so I printed those up and installed them immediately.

Here’s the guide tube fresh off the printer…

And here it is installed in the body of the airplane.

Next, I managed to drag a wingtip on landing on my Texan II and broke one of the scale protrusions off of the underside of the wing.  I shortened my redesigned unit a bit and made some minor concessions to ease of fabrication and printed a pair of replacements.

Here you can see the broken part and a replacement part being test fitted on the wing.

And here is the new unit in place after using some marker pen to add a bit of color.

Next I found the tail wheel mounting bracket of my Tundra to be somewhat weak… a known issue at the time.  I found someone had already designed an alternative, so I printed up a replacement.  Actually a couple!

Here are a couple alternatives I found… The top is a bit more solid and the lower a bit lighter but how well will it hold up??

Certainly many of these things take a fair amount of time to design, prototype and print.  But in many cases there are no replacement parts available or there are many options but no way to know which might actually work so 3D printing provides a way to work through the options without ordering and praying you find the right part, eventually.

So the real answer here is, Yes!  3D printing is a hobby all its own and can eat up a lot of time and effort.  It can also be an immeasurably useful tool for the RC modeler.  If you continue to follow my posts here, you will very likely hear more about it.

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New Hangar 9 P-47 67″ ARF… One flight and gone.

My first attempt at a replacement for my late lamented Top Flite is the H9 20cc size P47D 

P-47D Thunderbolt 20cc ARF, 67"

I transplanted all of my radio gear, servos etc… from the Top Flite and contemplated a number of updates/changes etc… 

Should I try to 3D print a better cockpit?  The provided instrument panel in particular looks like it could only be accurate if the instruments were updated to 2020 standards!  I decided to go ahead with the supplied until I decided how much I liked this particular model. 

I also contemplated and decided to put my retracts in the wing and even ordered a retractable tail gear.  When that didn’t fit I tried another and spent a fair amount of time fabricating linkage to make it work correctly.  Don’t believe the Horizon web site…  The nose retract they recommend simply can’t work as the tailwheel retract for this airplane!

I did find some plans for and 3D printed some wire guides to make wiring the bird easier and then crimped up some multi-connectors to make it hassle and error free.

After all that the bird was beautiful but heavy… compared to my Top Flite this bird was 3 lbs heavier and when I flew it I immediately found that it just didn’t track like the Top Flite and the thrust to weight ratio is anemic as well.  The extra 3 or 4 inches of wingspan just can’t compensate for the increased weight.  Now maybe my repaired power system is not operating as it was…. I don’t believe so but it is possible.  Or maybe the power system is just to small for this slightly larger WS and appreciably heavier craft.  Again, perhaps but there is no way the recommended Power 60 would be better.  I love the power 60.  It’s an underrated and amazing motor, but it isn’t going to outperform the Hacker A60. 

I flew one flight on the airplane and was so disappointed I took the airplane home and stripped my radio gear, retracts, etc… aside from the servos and wire guides… out so I could put it up for sale immediately.  Eventually a friend of mine purchased the plane and he and I are installing a DLE-20 he has.  Maybe with that power plant it will find a new lease on life.

For me, I have my eye on an airplane that is similar in size and weight to the Top Flite…  Hopefully my third P47 will be a charm!  For me, the H9 is to heavy for its size to fly the way I like.  I suspect that many warbird guys would love this plane, but anything I fly needs to fly well first.  Looks, scale detail, etc… all have to take a backseat and this was not my impression of the H9.

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Hacker A60 Repair

After the great NX10 failure of July 2021 I found myself with a Hacker A60-5S V2 motor with a bent shaft…  I had heard that parts were available for these motors so I searched and sure enough I found the replacement shaft readily available and at a pretty reasonable price… especially considering how well the motor had run and the higher initial cost of the motor.  I had expected worse so I went ahead and ordered the replacement shaft.

I had included a request for information on the replacement procedure when I ordered the shaft so when it appeared on my doorstep in just a couple days I was pleased until I realized that there were no directions included.  None on the website either and after searching the web thoroughly it didn’t appear there were any videos or descriptions either.  Not even a good exploded view of the motor was to be found!

This left me in a bit of a quandary.  After staring intently for a couple days at the motor and replacement shaft while they sat patiently on  a corner of my desk I eventually unscrewed the bolt that seemed to be some sort of bearing retainer at the back end of the shaft.  There was a thick non-ferrous washer underneath that came off with it but it didn’t just fall apart at this point so I examined it some more.  Seeing that here was a threaded hole and a matching allen bolt/set screw in the replacement shaft package I soon surmised that this set screw was hiding just behind the front plate of the motor and could be reached with an allen wrench via one of the vent holes on the sides of the motor.  With the help of some very bright lighting to make sure I guided the allen wrench to the screw correctly and that making sure I had a nice fit, I managed to unscrew that as well and fish it out of the motor.

At this point I could see no reason the shaft shouldn’t slide out but tugging and pulling (and cursing) didn’t seem to make it happen so I set it down for another bout of staring and perusing of the internet.  There were several videos of shaft replacements for electric motors but none of this model and many talked about pushing the shaft the wrong way causing damage to the coils in the motors… yikes!

A couple days more passed and I decided it was time to just take the plunge.  using a 1/4″ drive socket that happened to taper down to the perfect size to press this shaft out I placed the motor face down on my drill press table with the shaft through the hole… I was going to try to press it out forward as I had seen one other Hacker done in a video (a totally different looking motor but hey I only had two choices).  I had heard a drill press is a pretty good arbor press substitute so I started putting some pressure on the shaft which seemed pretty determined to stay right where it was.  Wondering if I might be purchasing a new motor soon I put a bit more pressure on it and… it moved!

I had to find another rod to push the shaft through a bit more before it started to move a bit more freely and I could press it the rest of the way out by hand.  Finally I had something that looked like this.

After a fair amount of cleaning with high pressure air and a little careful brushing with a toothbrush I grabbed the new shaft and discovered it’s a little shorter than the old one.

The important dimension however from the back of the shaft to the set screw was the same so not a big issue.   There was really only one more big “trick” I had to find out the hard way and that was a little issue of aligning the threaded hole up with the hole in the front plate so the set screw would go back in place easily.  Since it’s down in a dark hole when reassembled it took a bit of finagling but I eventually managed to get it all aligned properly and the motor looks like new and seems to run smoothly once again.

I’m working on the replacement for the Top Flite P47 now… of course a new Jug is in the works and now I have the perfect motor for the job! 

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Spektrum NX10 failure analysis and repair

In a previous post I reported on the demise of one of my favorite airplanes.  The Top Flight P47 60-90 size ARF.  The cause of that crash was that my Spektrum NX10 powered off mid-flight.  This is disappointing as I have run the NX for several months and been extremely happy with it.  The radio link to all of the planes as I  flew them has always been rock solid… well at least while the radio was on!

After the crash, there was no doubt the radio had turned off unexpectedly.  So began the investigation.  I posted online about the failure and found just two folks who had claimed to have something similar occur and none had an occurrence during flight. 

Thinking back, I honestly believe I may have seen it happen once on the bench shortly after first receiving the radio but at the time I was on very early code and was still learning to use the thing.  As it happened I was working on a setup of an airplane and turned away for a few seconds to check something else behind me… an email arriving on my computer or whatever… and when I turned back the radio was off.  I was so uncertain at the time as to the sequence of events that I passed it off as “perhaps I turned it off without thinking or realizing it when I got distracted”.  I really couldn’t believe the radio turned itself off and I never saw it again through setting up 20 or so airplanes on it, multiple upgrades, template creations and many flights on many airplanes later I hadn’t seen it again so had forgotten about it and moved on… until it did it again and my plane crashed.

Online I got the usual advice and questions… folks trying to helpful asking about battery state, shake tests, testing the on/off switch, etc… and I did as many of them as I could justify or understand to no avail.  I tried to jiggle the battery and connector particularly looking for an intermittent connection from the battery but it stayed on solid through all the shaking, wire twisting, switch tapping etc… that I could figure a way to inflict on it.  In a few days I acceded to inevitable and sent it off for repair with fingers crossed.  I spent years troubleshooting network for a living so I understand troubleshooting software and hardware systems like this when there is no no repeatable test case and no apparent error (other than a pile of wreckage) to be seen is an extremely trying task so I held little hope.

Now on the forums there are several very respected folks who monitor and comment on things and one is a gentleman who actually works on the software team for the NX series radios.  Andy, like others, recommended sending it in and contacting them to discuss it.  After the radio had been in their hands for a few days I reached out to him to try to figure out the easiest way to reach whomever was testing my radio.  I knew that the best chance of getting a fix was to give them as much information as possible and the online form only allows so many characters so I gave Andy a complete description of the issue and asked for his advice on how to get this to the correct people.  I also tried to impress on Andy that I really wanted a resolution beyond “no problem found” as I would never commit another airplane to flight with that radio unless we could determine a cause and apply an appropriate fix.  I also explained that I have been a pretty loyal Spektrum user for many years now and have purchased many Spektrum radios and spend a fair amount of time helping my fellow club members get the most from their Spektrum radios.  I really didn’t want this story to end with “…and that is why I have a $500 radio that sits in the corner and gathers dust”.  Returning it to me in that state would be a waste of postage.  Unsaleable and unusable…

Just a day later I got the notice that Horizon had sent me a shipment.  I feared the worst… then came the invoice for $0 and a note that they had decided to simply replace my NX10 under warranty!  Is this the best of all outcomes… no.  It is however the best response that I think Horizon had available to them and I commend them for excellent service once again.  I’m sure they tested my radio and had no way to recreate my issue.  I ran it for months and only saw it happen (maybe) twice and the circumstances of each were different.  I’m sure both Horizon and I are hoping it was simply a one in a million intermittent hardware issue and neither of us will ever hear anything like it again.

Horizon even went so far as to transfer all my models over to the new radio and upgrade the software to the very latest version.  They also sent me a complete new kit… radio, battery, strap, etc… all the stuff that comes with a new in the box system…. even though I had only sent them my bare radio minus batteries etc…  Of course they cannot replace my airplane.  That is simply asking to much and lets face it; if you can’t handle an occasional loss of an airplane you probably need to get out of the hobby.  They did more than I think is reasonable to expect in a bad situation and I appreciate that they are electing to take care of a loyal customer such as myself.  I have experienced much less satisfactory service from companies who have gotten a lot more of my money but Horizon seems to get it right more often than not so I will continue to support them and spend my money with them as often as I can.  Thanks to Andy and the rest of the team there.  You guys do it right.  Thanks again.

So I now have a brand new NX10 and am starting to get my planes bound to it and ready to go.  My Timber X is back on the NX10 and flew well on the first couple of test flights…. It may be a bit before I put the 12S powered Aerobat or the 1/4 scale cub back in the sky with the new radio, but as my confidence in the radio recovers, I’ll be moving everything back over.  Fingers crossed this will be the final chapter in this saga.

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Top Flite 60-90 size P47 ARF… Final flight. Spektrum NX10 failure investigation begins.

My Top Flite P47 was a super flying airplane with a great power system and has been performing flawlessly.  I have been testing out some different props to determine best mix of power, speed and flight times attainable.  Have broken a few props but otherwise she was running great.

Unfortunately all good things must end and a couple weeks ago she ended a flight looking like this.

No photo description available.

Here’s how it went.  On takeoff, I started a nice steady climb and flipped both the landing gear up and flaps up switch.  As you can tell in this photo, the gear cycled all the way up successfully and I’m confident the flaps did as well from the way the it was flying.  I then made a left turn and was nearly in knife edge when I suddenly realized I was no longer in control of the airplane.  The plane was sliding on its wingtip toward the ground and nothing I could do with the sticks had any effect.  Being electric and a good way out I heard nothing other than a sickening crunch after it disappeared below the corn stalks…

In disgust I dropped my gaze to my radio and was surprised to discover there was no display and no lights whatsoever!  I removed my sun glasses to be sure and verified the radio was indeed off.  After walking back to a seating area (I needed to sit down) I turned the radio back on and it powered up normally and showed the battery was at 4.0 volts which is in the range of 80-90% of it’s full charge state… i.e. the transmitter battery is not dead or even low.  I then tried to figure out if my neck strap, clip or some placement of my hands could have turned the radio off and I cannot imagine how to make that happen while going through the maneuvers that I performed.  It takes a good 4-5 seconds of steady pressure on the power button to turn off the radio and in that time period before the plane stopped flying I had flipped two switches and moved both sticks to adjust throttle and perform my turn.  Try that and tell me if you can do it, even if you try!

After a long walk in the corn locating the “remains” I started reclaiming all the parts and considering the wingtip and nose in a near knife edge collision to the ground, the components aside from the airframe faired as well as could be expected.  The speed controller had a fan mounted on it… That plastic frame did not survive but the replacement is $10 and the speed controller itself has tested out to be in good condition so far and does not have a mark on it otherwise.  The receiver is likewise undamaged and tests good as do all the servos.  The motor had the worst result, being a bit dirt caked and the main shaft turned out to be bent.  I’ll post on that separately.  The retracts, as you can see in the photo were safely retracted before the loss of signal occurred and also seem to be unscathed.  Even the two batteries (a 6S 5000 and a 2S 5000 run in series) look in good shape and still charge as before.  As I said, things survived pretty well aside from the air frame.  It is a total loss with only the tail surfaces seemingly intact.

As you can imagine, this started a serious investigation into why the radio shut down.  I’ll post a new entry about that soon.

So ends my favorite war bird to date.  There will be a replacement of some sort soon!  Here’s hoping your flights are more successful than this one was.

 

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