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Member postings for David Hall 9

Here is a list of all the postings David Hall 9 has made in our forums. Click on a thread name to jump to the thread.

Thread: SPACE X LAUNCH
31/05/2020 13:49:37

I tried unsuccessfully to find info/video of the first stage landing... anyone seen a video of the landing?

Thread: Motor thrust alignment Junior 60
31/05/2020 09:08:31

My recently finished (&flown) Junior 60 is my first "Vintage" model. I don't know what kit it came from, it was powered by a big brushed motor with an equally big belt drive gear system. The motor appeared to be mounted on bearers that had very little or no down thrust. I replaced the power system with a 3730 1000kv motor with the intention of 2S operation. It was flown initially on 3S with the throttle wound down to 50% and was still overpowered.

My F5J gliders all have a simple mix on the throttle to include a throttle to (down) elevator mix, adjustable on a Tx trim. I copied the mix to my J60 config. Without the mix, the Junior 60 would loop if left to itself during a high power run. With the mix added and adjusted, the climb is as I like it and the glide is spot-on... it all works well for gentle flying.

Incidentally, I still would like 2S operation. The same motor on 2S with a 13x7 prop on my E-glider sounds perfect, a nice calm whir. I would need higher capacity packs for the J60 but adding to my present battery collection is not a good idea. I measured the input power at around 200w and have now replaced the motor with a 2826/950kv and 11x6 prop (plus a little extra weight in the nose). I have yet to fly this.

Thread: Reisenauer gearbox motor replacement.
26/05/2020 17:03:36

Thanks for the pointer..... the German manual was useful. The motor mount plate appears to be simply tightened on a screw thread. If (big IF) no thread lock was used on it, I should be able to disassemble it. I'll need a new pinion gear I guess, and some Loctite to fix it on the shaft.

Any parts suppliers in the UK?

26/05/2020 12:42:06

I have a used Reisenauer micro 5:1 gearbox and outrunner combo. I'd like to replace the outrunner with an inrunner motor. Is it possible to remove the motor and would I need a fitting kit (some kind of Loctite, new parts etc..)?

Thread: Four Engine electric setup
11/05/2020 10:38:25

I had once considered how i would set up a four engine model for electric. The problems for me were, where to put the battery and how to control the motors.

The battery position was easier, I guess. One battery for each side.

The motor control, without being too techy, was to put the inner and outer motor pairs onto their own channel and to apply a curve to the outer motors to delay their power-up slightly behind the inners.

Never got past any planning and now other projects got in the way.

Thread: Use of SBUS/PPM converters in a wing.
07/05/2020 12:24:13

Thanks for the warning about possible problems using analogue servos. I quite like to use analogue at most, but not all control surfaces, so tend to end up with a mix.

Without a scope or such, I guess that a stalled analogue servo making the "normal" (old) buzzing noise around 50hz will be receiving a suitable frame rate, but if it buzzes with a significantly higher note, there's a problem?

 

EDIT:  just noticed a "Hz" position on my multimeter...  The meter shows 50Hz for the output from my iA10B FLYSKY Rx...  handy...   

 

 

Edited By David Hall 9 on 07/05/2020 12:34:52

07/05/2020 10:02:58

I have just completed my "Inside F5J" glider and wired the six servos in the wing, along with the connection into the fuselage. I had read of others planning to use an SBUS/PPM output from their Rx to drive a converter in the wing (or attached to the wing).

This would allow the wing-fus connection to be a single three pin servo connector.

It's too late for my six servo wing which is now ready, but my future (probably) four servo wings could use this setup. Four/eight channel converters are readily available and quite cheap. I can run the inexpensive FLYSKY iA6B (6CH Rx) from my Taranis Tx via the multimodule, and the later firmware for this Rx supports 8CH SBUS.

I can wire the three channels to the Thr/Ele/Rud as normal using the first three channels, then pick up channels 5 to 8 inside the wing on the converter via SBUS. I'm sure that SBUS/PPM is reliable, has anyone had experience with these cheap converters?

Edited By David Hall 9 on 07/05/2020 10:04:24

Thread: Varying wing section info?
02/05/2020 11:11:23

Thank you for the very detailed explanation Peter Jenkins.

I guess then, that the value of a specific varying section is arguably overkill on a model, but especially on a model wing of film covered open ribbed structure. The ribs might be accurate, but sagging film section between the ribs must be difficult to design to a known section.

 

Edited By David Hall 9 on 02/05/2020 11:14:55

Thread: Help needed with precise soldering
02/05/2020 09:38:14

Lots of adapters available... start with a search like this....

Thread: Gorilla glue
01/05/2020 23:04:02

It's good stuff, if a little messy at times. Be aware that as it expands in a gap, it can push parts apart, so clamp/pin things to be glued.

Thread: AngelWings Blink
01/05/2020 19:54:07
Posted by Bob Cotsford on 01/05/2020 18:24:48:

I spotted these and thought that for £35 it would occupy a few hours. The kit comes as a mixture of laser cut poplar ply and balsa sheets. At 300mm wingspan it's intended for small multirotor motors around 2000-2500kv running on 3 or 4S packs up to 1000 mAh and two micro servos. I have a 180W BL-2208/12 motor, 20A esc ................................

Is it 300mm span?... doesn't give the span on the website... looks bigger.

Thread: BEC testing surprise.
28/04/2020 19:12:40

As if to underline the effect of QA, I've just found another Hobbywing 3A UBEC, of the same type as the one that I tested. It's like a different device, the voltage regulation is much poorer than the first... it's a game of chance at the budget end ..

28/04/2020 17:19:15

When I came back to RC, I bought a bunch of no-name ESCs and a few Chinese DSMX compatible receivers. They all looked fine. I set them up on the bench and added servos. When I got to three servos, one twitch on the stick set off a shutdown that cycled on and off. Two of the three Rx's did this. A good Rx was fine. Now I test more often.

But my test does show that my current supply need is probably lower than I thought. I use the ZTW ESC in several planes and have no problems. If the one tested is a representative sample (low shut-off current), then I use less than I thought I needed.

Thread: Crow braking
28/04/2020 17:01:09

My setup on a Qx7 works well, although I haven't used crow braking yet It is configured, but I may not need it as flaps at around 80 degrees down brake very well on my lighter gliders.

I take the flap input (switch/stick etc) and put it on a separate unused channel. Flap is the same as spoiler, but in the opposite direction. I add flap to the flaps (some have aileron added), just add CH whatever, + 0r - weight. Similar for the aileron, add flap but in the opposite direction.

 

Edited By David Hall 9 on 28/04/2020 17:12:41

Thread: BEC testing surprise.
28/04/2020 16:36:47

bectest.jpgI have a small collection of BECs that were/are destined for use in my smaller F5J and sports gliders. I had found that the current output of the average ESC/BEC combo tends to be on the low side. For a 6 digital servo setup, I would choose something more like 4A min. For my latest 8 servo glider, a higher output is recommended in order to avoid supply collapse and brownout.

At the same time, I've started using opto ESCs, which can be remarkably small and light. I just need to find a separate BEC. I had a few small ones in hand and had bought a 4A and a 5A version for my plane.

As I recently bought a variable discharge load, I have all the kit I need to actually test my BECs, so I set up on my bench and ran all the BECs I had.

There were some surprises, but first let me say that QC, as always, plays a part in the performance we see.... you might see different performance.

I had set out a few tests for all the BECs, using a 3S battery.

First to see at what current the output collapsed (increasing quickly). Second, measure the voltage at 67% then 100% of the rated output and see how fast they heated up.

My ZTW Beatles 30A ESC output collapsed at 3A/4.1v. It gave 5.1v off load, 4.1v at 2A and at 3A (constant) it melted the heatshrink covering quite quickly. Test aborted.

Turnigy 5A 8-26V input SBEC. 5.3v no load, O/P collapsed at 4.1A. At 67%/5.0v it was getting too hot quickly. Test aborted.

Hobbyking 4A no brand SBEC. Output collapsed at 3.5A.

To cut out more wordy detail, the KingKong and Hobbywing 3A SBEC (UBEC) did very well, both maintained an output over their rated 3A. The HW maintained 5.4-5.1v right up to 3.5A when the output shut off (collapsed) and was the coolest at 67% output. The King Kong didn't keep such a good regulation but managed a transient output of 4.3A.

The real surprise was the tiny FPV bluesky UBEC 5v. This sold as a 3A device. I tested two. The best had excellent regulation, 5.3v, down to 5.1v at shutoff at over 4A. Managed 5.2v @2A, 5.2v @3A (getting warm), Held 2A fairly well, just getting too hot to hold after ~1.5min.

So... my fav ESC (this example) output is lower than rated, but that might be max transient output, not constant. The higher output SBEC of 4A and 5A are poor, and the super cheapies were very good in this test.... just what kind of noise is output on the supply is something else, I guess.

My tests were based on my need, to supply rather high transient output current whilst maintaining a reasonable steady output.

I think that is shows how the spec can vary almost wildly and probably be effected by QA issues.

 

Edited By David Hall 9 on 28/04/2020 17:05:01

Thread: Varying wing section info?
27/04/2020 12:17:18

I found this in a thread elsewhere. It explains the reason for the changing section.

" Dr Drela designs airfoils for particular Re operation ranges, which is one of the reasons he uses different sections along the span of a wing. As the cord shrinks and the Re gets smaller, he uses an airfoil optimised for that range."

These are fine design changes indeed.

So, if I were to adhere to this idea, then my scaling up of a wing that uses a range of AG airfoils by ~25% might change the airfoil sections to a new set of AG airfoils.

27/04/2020 09:01:01
Posted by Dickw on 25/04/2020 12:39:50:

A linear change between sections along the wing is one possible option (and perhaps the most common), but that it really is up to the designer and that depends on what he hopes to gain by using the different sections at different locations. For example, you might use a thicker tip section to try to avoid tip stalling or a thicker root section to give added strength. Not saying either would work - just simple examples.

Sites like Airfoil Tools allow you to compare how different airfoils work.

Go for it - and lets us know how you get.

Dick

Thanks Dick,

I am considering building a scaled-up version of a glider that I have at the moment. As you say, altering the thickness of the airfoil is something that I might expect. I will have to dig a little deeper. I guess that the different sections incorporate similar features and advantages when compared to simply altering the thickness of a single section.

25/04/2020 12:10:56

On quite a few gliders, I have seen the wing section quoted as, for example: "AG35-36-37".

I guess that this will mean that it varies linearly along the wing...is that what it probably is? is there a design convention for the way this changes?

I am considering having a go at glider wing design and wonder how to incorporate this feature.

 

Edited By David Hall 9 on 25/04/2020 12:11:25

Thread: Höllein Inside f5J kit
25/04/2020 12:05:47

Good info... Have you balanced for the CoG yet, having used a motor much heavier than the Hyperflight example?

Mine has come out of the box again.. adding wiring then to be covered.

Thread: Electric powered gliders
21/04/2020 16:44:21

Posted by Erfolg on 21/04/2020 13:59:01:

.............................

Yet for performance a model glass ship beats anything I have ever built hands down, leagues away in all aspects of performance, if I only had the money.crying

 

Apologies, not directly related to the OP, but this comment from Erfolg stirred my enthusiasm.....

Last year, I became a bit more serious about competing in F5J and decided to move into open class. I had completed with 2m models and had enjoyed it, but noted that even my 2.5m ship would seem to handle better and (apparently) outperform the 2m. I am building a 3m balsa glider (nearly finished) but in the meantime, I bought a competitive, well used CF 3.8M ship. I have begun to regret my purchase (buying into this a bit too heavily) and have thought that I should stay with my smaller models...

I've heard one or two others mention the performance levels of the CF moulded ships, Erfolg's comment reminded me of these... Perhaps, if I am lucky enough to survive the virus, I should at least have a go with it.. If I don't survive it, my wife might sell it for half of what I told her I paid for it.

Edited By David Hall 9 on 21/04/2020 16:53:00

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