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Member postings for Biggles' Elder Brother - Moderator

Here is a list of all the postings Biggles' Elder Brother - Moderator has made in our forums. Click on a thread name to jump to the thread.

Thread: Please Help Me Out With The Arithmetic On This One Gentlemen!
21/08/2018 11:16:41

Ib agree it won't be the same as a flying test - but it will at least give us a handle! At the moment your earlier comment about no firm data to analysis is totlally correct.

I'd agree with using the physics - but we don't even know the weight of the aircraft to make a start!


21/08/2018 10:43:49
Posted by Nigel R on 21/08/2018 10:42:10:

David, get a wattmeter and stop messing about with guesswork. It would make life so much easier.

Excellent advice! I'll second that.


21/08/2018 10:42:49

1. kV is the unloaded rate - in practice no motor with a prop on it will ever reach its kV value - 75-80% max.

2."Current is regulated by the ESC" - not that simple I'm afraid. The motor will attempt to draw whatever current it needs to meet the the speed demand the clue is in the name "electronic speed controller" - not current controller! - if the current needed to meet the speed demand is beyond the motor or ESC current handling capability, they just burn out.

3. Props are notoriously complex beasts. It might be a very rough generalisation to say a motor is is at its best at 75% (personally I doubt even the usefulness of that claim as basis for calculation) it certainly isn't valid as a generalisation about props, all sorts of things can happen there!

4. "That means that 5S will get you get approximately 25% more power" - again a over simplification I'm afraid. The 5s will spin the prop faster, but to get better performance you would almost certainly change props - all deals are now off. Even if you do get approximately 25% more power - you have added weight the aircraft now needs more power simply to maintain it existing power to weight ratio and hence performance. So some of your "gain" is lost.

5. "A lower current ESC", never heard of it! The current rating on an ESC doesn't tell you what you gives - it just tells you what its maximum current handling capacity is! Again it doesn't determine the current the prop providing the load effectively does that.


Thread: Which Radio Gear?
21/08/2018 09:39:21

Dave H - please read your PM's - now!


Thread: Please Help Me Out With The Arithmetic On This One Gentlemen!
21/08/2018 09:35:05

TWS's analysis also makes sense - but doesn't square with mine based on the current and power info!!

Conclusuon: You can't be getting 800W David or you would need close on 8000mAh not 4400 mAh as TWS calc suggests. Alan is right I suspect, your motor may be capable of handling 800W but you are not getting that - sounds like you are getting more like 500W in reality.


21/08/2018 09:30:48

Hi David,

maths good - 9/10

Terminology? Er,...2/10? smile

Ok you have 800W of power, from a current of 54amps.and you want this for 8 mins.

What proportion of an hour is 8 mins? Well its 8/60 = 0.133 (recuring, but we'll ignore that!)

So we want enough battery capacity to supply 54 amos for 0.133 of an hour - that will be 54 x 0.133 AmpHours

That works out at 7.182 Amp Hours - whch is 7182 mAh - say 7500 to 8000 to be on the safe side. That's a very big (and expensive) battery!


Thread: Which Radio Gear?
21/08/2018 08:57:37

I've asked nicely - now more forcably! This is not the place for fight over radio systems. If you can't give the OP some informed positive advice then its best not to bother!

One post deleted so far - we'll close it if this carries on.


Thread: Servos that swing both ways!
21/08/2018 08:42:07

Yes, you can still get servo-reversers. Sonmetimes they are the only practcal solution.

A friend of mine recently had this issue. He had two elevator servos in the tail of his Sbach, one of which was reversed. Easy with modern radio of course, just put the servos on two channels.

He wanted to test a new gyro he had bought - problem,...only one elevator channel on the gyro! The soltution he employed was to have just one elevator channel, use a Y-lead but put a servo reverser in one leg of the lead.


Thread: Which Radio Gear?
21/08/2018 08:34:50

Guys, we have been handling this type of thread very well lately, but this example seems to me to be slipping back into the old ways.

Remember, there is no perfect radio system.

1. Its not really on to issue instructions like "buy this" or "don't buy that" - it just aggravates people.

2. In my view, and I think that of many others, all modern radio systems are superb, They are full of features, very powerful and ultra reliable.

3. There are differences and I say "viva la differnce"! Because that allows folks to get stuff that suits their interests and their focus.

4. Its also not really on to make sweeping comments about a radio system based on 5 mkns acquantance!

So, can we stow the negative views and focus on the positive please, telling the OP what is good about your choice rather than what's wrong with everyone else's!


20/08/2018 21:43:12

Despite the fact that I am dedicated OpenTx/Taranis user I wouldn't recommend it for you. If you don't like computing, programming etc. and you are only an occassional user you will never get to grips with it.

Try a look at least at a Spektrum 6e, simple to use very user friendly etc. Does most of the set up for you!


Thread: Servos that swing both ways!
20/08/2018 21:39:40

That works for the ailerons yes - just the arm on the other way round. But not for the flaps. If they are mounted mirror image (and nothing else is done) they won't work - or at least they will work, but as ailerons!


20/08/2018 20:17:35

More manufacturers are doing this now - Flightline do it in some of their models for example. Whether is a dedicated servo or some trickery in their "blue box" I don't know. Everything is done on Y-leads then.


Thread: Binding V8R4-II
20/08/2018 20:13:44

Right now you don't need to do anything except buy the X4R (go for that if its a shockie). Every else will start to fall into place once you are an active user!


Thread: C of G Which way up and why?
20/08/2018 13:46:17

CoG often tends to be quite close to the spar I find.

Intentional? Maybe, might be with individual desigers who tale some care, but with the big boys I sometimes think its just luck!


Thread: Binding V8R4-II
20/08/2018 13:31:35

Sorry Ron for mistaking you for Denis - oh and sorry Denis for mistaking you for Ron!

I didn't know the QX7S came with OpenTx, interesting. I assumed that like Horus it came with FROS. You see, still learning! I'm an X9D man myself!

But it doesn't change the basic advice Dave H - go for the X8R - it will get you up and running, and that will give to the incentive to learn mnore!


20/08/2018 11:02:45

OK,let's slow down a bit! Your problem, basically is that FrSky receivers can work in many modes, two of which are so called D16 and D8. I'm not going to go into why, but let's just say that D8 is not the popular mode within Europe, we tend to favour D16. Your Tx is set to work on D16. It can be changed, as the guys have explained, but I'd say don't go there just yet - you're not ready and you don't have enough general background knowledge - yet.

Right, so piece of concrete advice number one:

1. If you just want to get going buy an X8R FrSky receiver from T9HobbySport. That will work off the shelf with what you have because it will be set to D16. It'll solve all your immediate problems for £28 or so. I know Denis recommended the X4R - that's basically the same thing but only has 4 servo inputs - the X8R has 8 inputs and only costs a couple of quid more. Both will work, but the X8R is better value in my view.

Now the next bit of advice

2. FrSky transmitters such as yours can run two different software systems: FROS, that's FrSky's own system, or OpenTx which is a shareware system. I my view OpenTx is the main reason I use FrSky - FrSky kit is good, reliable, low cost etc and I like it. But it's its ability to run OpenTx that really attracts me. OpenTx is immensely powerful, you can program pretty well anything you can conceive of. But its not simple, so this is something you need to research and learn about taking your time - definitely go fo it, when you're ready! In the meantime step 1 above will get you flying.

3. You asked what companion is and how you get it. Companion is in my view the best thing since sliced bread! It is a software application that runs on your PC and enables you to connect your Tx to your PC and program it from there. It only runs with OpenTx - so its something for the future for you as you learn. It is so easy to use - every programming tool on the Tx is laid out for you on tabs - dead easy to see, easy to navigate between. MOST (but not all) of what you can do in Companion you can do on the Tx itself - its just just a lot easier in my view. Eventually you will learn to do it both ways - on Companion and on the Tx.

OK, so there are some starters. You have chosen to buy possibly the most powerful and advanced RC system currently available - don't regret that, its the best you can get in my view, you will never outgrow this. Comparing it with a Spektrum is like comparing a Fiat 500 with a F1 racing car!

But with that power comes some complexity, you have to understand that. Its hard work learning this - there is a lot to learn, you mention 30 hours research, peanuts mate, I've been studying FrSky and OpenTx for going on 3 years, I'm still learning! But commensurate with the effort is the reward - that too is very large, the ability to do more or less anything you want with a model aeroplane, it's got to be worth it.

But see all that in the future and enjoy the journey of discovery - but for now just do step one and go out flying and have some fun with the kit - what its really about!


Thread: Goldwing 70e planes
19/08/2018 17:57:00

It's out of stock Bob, so you're safe,....

unless of course it's out of stock because you just bought the last one!


Thread: C of G Which way up and why?
19/08/2018 10:04:23

David is right of course, the CoG is the CoG - either way up!

But having said that some things are just easier than others - so given you get the same result why make things hard for yourself! So I go for:

High Wing - right way up

Low Wing - inverted

Shoulder Wing - please yourself!

Always balance, initially at least, in the worst posible configuration - so that's usually fuel tank empty as it usually in front of th CoG so when full can only help matters and empty is its worse case. Same with retractable U/C, put it in the worst case position where it will push the CoG back.

If you do that, and its level, or very slightly nose down, then you'll be fine for a maiden. As others have said you can then tweak it a little as you get to know the aeroplane's characteristics and to suit your flying style better. With "tweaking" though remember that some models are very sensitive to CoG position and 5mm can make massive difference. With others, 20mm can hardly seem to make a change! Until you know which you've got be cautious when moving the CoG


Edited By Biggles' Elder Brother - Moderator on 19/08/2018 10:07:47

Thread: Anyone interested in a Nats meet-up?
18/08/2018 22:05:22

Its just next to the trade area Martin. Its not a "tea area" as such, its the general refreshment area, food and drink. Arrangenments for beer can be made for later in the day, 12:30 is a little early in te day for a beer for me smile p


18/08/2018 18:57:45

Saturday is looking a bit thinner. But I will go both days at least so we'll go ahead with both Saturday and Sunday, in the refreshment area (behind the trade) at 12:30-ish.


PS I'm sure Graham and/or David will try to make at least one of the dates as well - that'll add a bit of glamour! And I'll try to drag Mr Bott along, with his soldering iron!

Edited By Biggles' Elder Brother - Moderator on 18/08/2018 18:59:50

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