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February 25, 2020, 18:26:32 pm

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Wanted: old DSM2/X transmitters!

Started by PDR, January 18, 2020, 17:35:59 pm

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PDR

My daughter has decided she wants to have a go at flying. I don't think she'll stick with it for long, so I'm reluctant to get her full BMFA membership and insurance in her own right, but apparently if she's on a buddy box lead then I'm the one who is flying and so she's covered. So I just need a couple of basic transmitters I can buddy-box together. Ideally DSM2/x so that I can use basic Orange receivers.

So does anyone have a DX6i or similar that they don't want much money for?

TIA,

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

PDR

OK, so no one offered me anything, you tight-fisted gits!!

:ev

I took another approach and bought a pair of Turnigy TGY-I6 sets from HK (EU warehouse, free shipping, about £40 each f9or a Tx+Rx combo) as being the cheapest buddy-boxable sets I could find (also sold as FlSky etc). HK no longer offer the buddy box cable, but you can get them on ebay or amazon for a few quid. I was expecting basic, but actually these transmitters have 20 model memories and quite a lot of programmable functions, so I'm more than happy with them.

So I then just needed a trainer, and I settled on the FMA Kingfisher for under £140. I have to say for a fairly cheap foamie this thing is very well thought out and nicely engineered. It's a bit larger than most of the 3s trainers (55" span) with big tundra tyres on an aluminium undercarriage and (surprisingly) flaps in a full four-servo wing.

This is the "basic" version, which is ~£140. There's another version of the kit which is about £40 more that includes both floats and skis as well as the tundra tyres (a true all-terrain model!) plus an extended water rudder for use with the floats. I gather it takes a couple of minutes to swap between them, but I couldn't justify getting that version as it rarely snows and we won't have a lake until climate change raises the sea level by 100m or so.

The wings have full span carbon-tube spars which slide onto a carbon tube wing joiner and then just snap-lock into moulded wing root fittings. There are injection moulded V-struts that attach to the wings and fuselage on moulded plastic spigots retained with R-clips. The flap and aileron servo leads pass through good-sized holed in the wing root mouldings into the "cockpit" area.

A large hatch comprising the dummy windscreen and a large part of the front fuselage gives easy access to the motor, battery mount and a shelf for the receiver right next to where the aileron and flap servo leads come into the fuselage. The hatch is retained with a substantial moulded plastic snap-catch. Supplied hardware includes all linkages, and ingenious prop/spinner combination and a pair of Y-leads for flap and aileron connection if you don't have the receiver channels or transmitter mixing to do without (a nice touch). It comes in ARTF format including all six servos, motor and ESC needing only Tx, Rx and flight battery to be added. The instructions and website photos show an EC3 connector on the ESC, so I was expecting to have to cut it off and fit my standard XT60, but when I opened the hatch I was pleased to see an XT60 already fitted. It uses the ubiquitous 3s2200 lipo and claims flight durations of 30 minutes when flying typical "basic training" flight profiles, which will be pretty impressive if it's true (this is a big aeroplane for a 3s2200)

Now I was going to do a build thread (honest!), but it was literally too quick. SWMBO was out this evening, so I opened the box in the sitting room just to have a look while listening to the radio. I opened the box after Sara Millican's quiz show started, and had it fully built before having to switch off to avoid the Archers - less than 25 minutes including setting up an unfamiliar transmitter. Had I actually realised that I would have been seriously tempted to take the unstarted kit to the club field on saturday to build when I got there!

I said this was well engineered - this model not only needs no gluing, it actually uses only five screws in the whole build (three to attach the undercarriage and two to attach the rudder horn/tailwheel mount). Sadly these screws have 2mm allen heads ("sadly" because it meant I had to pop to the workshop for an allen key!). The tailplane slides in with a snap-catch, the wings slide onto the carbon tube and are retained with a snap-catch and the struts are retained with R-clips as previously mentioned. The wing servos and flap/aileron linkages are all pre-fitted and adjusted. The rudder and elevator pushrods you have to fit and adjust for yourself, but the servos are pre-fitted. In fact the only thing that's even vaguely like "construction" is the rudder assembly. The tailwheel has a long torque rod with a U at the end that passes right through the fuselage to attach to the base of the rudder. Once the tailplane is slid into place and the catch locked home the tailwheel torque rod is passed through a plastic moulding on the bottom of the fuselage and then the U-bend is placed against another plastic moulding in the base of the rudder. A third plastic moulding which incorporates the rudder horn then clamps over the top of the tailwheel torque rod using two screws. You then just fit the pushrod and adjust the clevis to centre it all.

The final clever bit is the spinner/prop assembly. The 3-part plastic spinner has a backplate with a hex socket that fits over the hexagonal shaft of the prop adaptor. This backplate  has moulded seats for the prop blades. Then the second part is slid on, which has moulded plastic seats for the upper surfaces of the prop blades. Finally the cone (which has an integral threaded brass bush) is just fed onto the propshaft and hand-tightened, As far as I can see that's it - there's no way to get a spanner onto anything to tighten it further.

I'll do some photos tomorrow, and add some notes on setting up the transmitters, but it was perfectly straightforward. The weather looks reasonable so I'm expecting a test flight followed by its first basic training sorties on saturday (I'll do some photos).

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

FrankS

Yep, these types of models make good trainers, we've been recommended the Hobbyking Tundras for the l8 months and they've proved ideal (and surprisingly repairable). No longer available at the moment so looking forward to your flight report on the Kingfisher.

PDR

Errors and omitions:

1. Holding a wing up to the light this morning I see it has two 10mm carbon tube spars in each wing, not one. I'm still trying to decide whether the struts are functional or cosmetic, though.

2. They supply a second canopy/hatch which has mountings specifically designed to accept an FPV camera and its transmitter

3. I'm not 100% happy with the battery mounting. The kit provides a large area with a velcro seat and a velcro strap. I guess the idea is that the strap holds the battery in and the velcro seat stops it sliding around. I don't use self-adhesive velcro for batteries (I could never get the damn stuff to stick well enough so that it actually separated the hooks from the loops rather than peeling the tape off battery or model!), and I sure as heck ain't going to add velcro to all 24 of my 3s2200s just for this model. So I may add a couple of spall pieces of wood to locate the battery while still using the strap to hold it in.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

paulinfrance

I use Velcro to stop all my batteries from sliding about and another strap to hold them in from my, 4 M glider to my 250 drones ( am I droning on again $%&  )
As for the strength of the wings, put the midway point of the wings on a support and put 5 times it's flying weight on the fuselage,, ^-^
Mode 2 THE only way to fly

PDR

I was doing the final prepping and final CG check this evening. The CG came out towards the rear of the recommended range, which was OK. But I looked at the battery compartment and thought about how it was huge, and how it would easily take a bigger battery. And then I thought about how this model is intended for basic training - a task that benefits from longer flights. So I tried a 3s3300 pack. It not only fitted with ease, but tghe CG move to the middle of the recommended range. If the claims they make for the 2200 size are true then this pack should be good for 45 minutes.

So I have just charged half a dozen 3s3300s so that my daughter can get a good long introductory flying session with plenty of stick time.

I'll report back after tomorrow's session.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

paulinfrance

Quote from: PDR on January 24, 2020, 23:18:33 pmSo I have just charged half a dozen 3s3300s so that my daughter can get a good long introductory flying session with plenty of stick time.

I'll report back after tomorrow's session.

PDR

Half a dozen battery's, so you have confidence in your daughter and your teaching skills,,,, :study:
Mode 2 THE only way to fly

PDR

Well this is the bit where I say "Flew it today and flies really nicely", but actually it didn't. The day was cold and clammy, but not raining. A complete white overcast with the cloudbase down at about 300feet - not really ideal for first training flights with an aeroplane that has a completely white underside, but never mind.

Firstly I remembered to take some photos:




I should have put something in there for scale, but at 55" span this is quite a big model for a foamie. This is that huge battery bay under the canopy hatch:



I put it all together, fitted a battery and took it out for a test. Full throttle current on a fresh battery was 30A (measured with a clamp meter) - call it 340 watts for most of the battery run. It taxied well, steering was good and no ground-looping tendencies. It responded briskly to throttle and clearly had plenty of power. The take off was rapid with a little directional instability, but only a little (narrow track UC with the wheels well ahead of the CG, so not surprising). But I then found I needed half the available up elevator to fly level (far more than I could trim), so after a couple of quick circuits to check low speed control I landed. Approach was good, landing very straightforward.

I took it back to the pits and cranked in a lot of mechanical up trim. I started doing this on the clevis, but it left far too little threaded rod in the clevis so I moved the servo arm round by one spline. I'm not overly happy about this, so before the next session I'll make a longer pushrod and move the arm back to where it was.

Second flight was better. Elevator trimmed out nicely, but I couldn't seem to trim out the ailerons - it would wander off to one side or the other. Whether this is a lack of lateral stability, cheap servos or cheap Tx isn't clear. It's not a major thing - it's just that I like to be able to trim a trainer to fly the length of the strip hands-off and this one definitely wouldn't. But it was near enough and my daughter was champing at the bit to have a go, so I landed to connect up the buddybox. On this landing I tried the flaps. dropping them at normal cruise speed produces a massive initial pitch-up, but once the speed decayed the trim returned to normal. With the throttle shut and full flap it will do a 40 degree approach with no speed increase - they're powerful!

So we connected up the buddybox lead and did five training flights through the course of the day.My daughter did reasonably well, making all the usual mistakes and learning to recover from them. Given the difficulties (white model against a white sky, a slight blustery wind and lack of lateral stability) I think she actually did pretty well. A couple of times this got into the full death-spiral and I used full up (low rate) to recover - the wings stayed on, which was nice. These transmitters don't have timers on, and I forgot to start a watch, but I'd guess we were doing 15-20 minute flights and they took the battery down to between 12 and 18%. So I wouldn't want to use the recommended 2200mAh battery - not for flight training, at any rate.

My daughter then left to go shopping and I put the last battery in to go for a bit more extensive testing. I found a full throttle take-off would get a vertical climb for about 200 feet, and a 60 degree climb indefinitely. This is about what I'd expect from 300 watts in this size aeroplane. I also found that full (70 degrees) flap does actually boost the lift coefficient as well as add drag (which is actually quite rare) - with full flap I could hover over the centre of the runway in what I'm guessing was ~5kts of surface wind, so probably 10-12kts at 60feet. Loops and rolls were OK, but I found it flew better with a little rudder to help the ailerons. For training flights I may try putting in some CAR mixing to help. I still couldn't get the ailerons to trim-out. It also seemed to roll left slightly with either power or airspeed (not totally sure which) which implies a warp somewhere in the wing or fin, but I couldn't see it.

I couldn't resist the temptation to try out those tundra tyres, so I did a couple of touch & gos on the rough, unmown grass away from the strip which it handled well, and at the end of the flight I taxied back over the rough as well.

When I took the wings off to put it in the car I discovered that the end-fitting of one of the rear struts was loose in the tube. This MIGHT explain the wandering roll trim, but frankly I doubt it because the wings are torsionally stiff and I'm not convinced the struts do any structural work.

So as a sport model it's OK, and undoubtedly tweakable. But until I get the trimming problem sorted it's less than ideal as a trainer.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

firefox

You could always add a Litho plate trim tab, as per full size.
Nothing is foolproof to a sufficiently talented fool......

FrankS

Was one of these down our field yesterday, pilot was happy with it, no reported trim issues. It was on a Spektrum Dx6.