Be Excellent To Each Other

Hello all.

I seem to recall that one or two of our esteemed board members fly radio controlled aeroplanes. I do too. Swell, eh?

I have up until now, been flying a leetle GWS DH-2 Beaver* with a brushed motor and running off Ni-Mh batteries. Having managed to teach myself to fly on this 3-channel little beauty, I have decided to try my hand at an aileron aircraft. It just so happens that GWS make a lovely little copy of theT6 Harvard, which at £25 without a power system is excellent.

Now, where the point of this post comes in, is that I keep reading about "brushless" motors and "Li-Po" batteries. I'm frankly bewildered as to what on earth I should be buying. I've just about manged to work out what size brushless motor and associated speed controller I need (here), but when it comes to the batteries, I haven't a clue. It's gibberish.

So, can anyone explain to me in a brief idiot's guide what all the stuff in the battery names mean? E.g. HiModel 1300mah 3S 11.1v 20C (26.0A) Lithium Battery here.



I get that the milli-amps per hour figure is basically the capacity (i.e. will dictate the length of use you get out of it), but what's the relevance of the voltage, the "20C" figure (is higher better? Does the motor dictate a maximum figure for this?), the amperage and the continuous and burst discharge rates? Basically I want to be able to buy a moderately cheap Li-Po that will work with the motor and ESC without frying them and give a respectable, but not huge, flying time.

Is anyone who knows anything about electricalmabobs able to help Mr Thicky here?



*Snigger

That would be me then. I'm fairly new to the lecky stuff having learned on the oily, noisy type ones.

I'll try to give a better answer later but that battery you've linked to should be fine. The thing with LiPos is that if you discharge them too quickly then it knackers them. So even if you are unsure exactly how much current your setup will be drawing then buying one advertised as having a high discharge rate is a good idea. You need to choose a capacity based upon the ideal all up weight for you plane. So once you've got it all built you need to weigh it and see how big a battery you can fit to get the most flying time. This figure isn't set in stone though so you can fit a slightly heavier battery and it will still fly just probably a bit differently.

To choose batteries properly you really need to use a watt meter and maths and whatnot, in practice what you are far better off doing is going on one of the many RC forums reading around and just replicating one of the setups of someone who seems to know what they are doing (and there will be loads of threads for any GWS plane). That way you get a feel for what is right and don't waste any money due to a miscalculation.

There's some good info on here (just ignore all the crap about why their batteries are the best):

http://www.flightpower.co.uk/index.asp? ... ticles.asp

Just be really careful when using these batteries though. Whilst they are the same technology as used in laptops there they are in a far more controlled setting with special circuitry etc to keep things safe. Used for RC they get rough treatment and the chargers just need the wrong setting entering to cause a fire. Get one of these or a fire safe from Woolies or somewhere to charge and store them in:

http://www.hobbycity.com/hobbycity/stor ... oduct=4134

Coo, thanks.

I'd picked up on the dangerousness of them, and it frankly scared me to start with.

However, given the dwindling availability of Ni-Mh flight packs I'm not left with much choice. And I've noticed that these new "toy" RC helicopters are being sold with LiPos so they must be becoming even more mainstream within the hobby.

I wouldn't worry about it too much LiPos just hold so much more energy for a given weight (also they don't suffer from battery memory problems) that just double checking your charger settings and keeping them in a safe place is more than worth it.

Here's another good UK supplier of cheap but good Chinese stuff, I don't have any myself yet but the "Loong Max" batteries are meant to be really good (be sure to check the stock level before ordering anything though):

http://www.giantcod.co.uk/index.php

Mark!

You dropped your hat.

When I read about this I thought to start with that the publicaiton was having me on. It's a bizarre phenomenon, an done I wished I'd known about before I started using my GWS Ni-Mhs.



Oooh, very excellent, thankyou.

EDIT - Fucking hell that place is cheap. Double thanks!

So, having transitioned to leccies, what are you flying?

Oh, also - charging/balancing - is there antything special to bear in mind here? Is it worth getting a fancy setup or will a cheapo charger and inline balancer be fine?

I fly gliders more than powered stuff though, if you live anywhere near a suitable hill then you should try it.

I think that should be fine yeah, just do a search for the name of the charger you're thinking of buying and the word forum and you should get an idea if there is some terrible problem with it. Also either look for a charger with an AC adapter or look at getting an old computer PSU to convert it into a power supply. I didn't have either for ages and so kept having to use my car battery.

Yes, I'd been using a car battery for my GWS charger. How easy is it to convert a PC PSU, as I have several lying around?

Re gliders - I live on a hill, so it may be worth a go. I've no idea how thermals work, though.

EDIT - sorry, I'm asking lots of questions, and you're being very helpful.

Here you go:
http://www.wikihow.com/Convert-a-Comput ... wer-Supply

Edit: if that's too much hassle do what I did and buy one of these:
http://www.modelsport.co.uk/?CallFuncti ... emID=23410

On the glider thing, there's basically two types of gliding, slope and thermal soaring. Slope is dead simple it's just the wind hitting a slope and being diverted upwards, you can fly in this band of lift as long as the wind is there.

Thermal soaring is perhaps more of an art or requires much more luck. As I understand it the sun heats up different parts of the ground differently according to the colour of the ground or breaks in the cloud etc. What sometimes happens is than bubbles of warm air rise faster than the surrounding air (I've been told by some to picture a lava lamp as a way to visualise it). Usually a stack of seagulls or other birds climbing but not flapping is a good clue, you then fly your glider into the area and get all the height you can before it goes away and you need to find another.

It depends what your hill is like as to whether it would be any good, ideally you want a fairly steep hill facing the prevailing wind direction with a good few miles distance to any hill facing it. You want "clean" air hitting the slope rather than air that is still churning around. Having said that it doesn't need to be perfect, I often fly from the sea wall behind my house, this is just a 20ft high slab of concrete but on a windy day you can still get 50-60' out of the top. Again just watch what the birds are doing, if there's free lift to be had anywhere then they will know about it and use it.

Slope soaring is ace though and you can use pretty much anything with wings given enough lift. To start with though get one of these sorts of things:


http://www.modelmaniacsonline.co.uk/pro ... &CatID=423

They are made of a sort of foam are pretty much indestructible (they really are too, mine piles into the sea wall all the time and you can just pick it up and throw it off again), they fly really well and can be flown in winds from about 10mph to about 50mph. Also if you can persuade someone else to have a go then you can have hours of fun trying to knock each other out of the sky.

Excellent - I shall give that a go. We have a good long flat area between the River Severn and the back of our hill, and the prevailing winds seem to come from that direction, so that should be perfect!

The PSU looks a bit beyond me, though, so I may end up buying a 12v transformer.

EDIT - or I'll just get this.

Thank you for the advice and links - you've just saved me about £30 all told!

I shall soon be whizzing around with one of these:

Mr Chris and his plane, yesterday.

Actually Dudley you've inadvertently raised a good point there, third party insurance is only about £20 a year for £5m cover and I'd say it's a worthwhile thing to have.

I have? Shit I better delete that post at once.

I have it for my RC car (Schumacher Riot, RC fans!).

I can understand insurance for a large scale IC plane, but for small foam parkflyers or for a radio controled car? Wtf are you using the car for, Grim...? Ramming other peoples' pushchairs?

Yeah I'd say that small foam parkflyers are a bit borderline for needing insurance, you'd do pretty well to hurt someone but it's just about conceivable if you imagine the worst case scenario of hitting, say, a small child in the head at full speed. I'm also a bit baffled as to why anyone could need insurance for an RC car though.

While I don't have insurance for my radio controlled car, it's a big heavy beast that could certainly break bones if not worse if used used improperly, or just goes out of range. It has a variety of fail safes, but you can never be sure.

Do you have any links to insurance companies who specialise in these things?

My RC car can go nearly 60mph, and weighs a couple of kilograms.
Ankle-snapping ahoy.

I think I recall from my litigation classes at law school that, oddly enough, most home insurance has some form of cover in it for random lawsuits.

If you hit anyone with a plane, just go get your car and run them over. Bingo, car insurance solves the problem.

Small but pernickety point: "memory problems" don't apply to NiMH cells. Or modern NiCD ones, for that matter.

However, as noted, LiPO is so much better in most regards that you're quite right to be experimenting with it. Just do be careful charging and storing the batteries indoors!

Extreme end of the scale: http://www.killacycle.com/

Oh, well. I feel less bad about my pattern of usage on the Ni-Mhs then. But one or two of them do seem to have gone quite "short" in terms of capacity, compared to their original performance...



Crikey.

Entirely unrelatedly, you can buy actual mini turbojets these days for RC model jets. Bonkers.

Well, the capacity declines as the cell reaches its cycle life anyway (worn out is defined as 80% of spec, usually). In RC usage which is pretty extreme, the cycle life can be rather short, and the pack can alternatively die early from reversed cells, overheating, overcharging and so on, all of which result in it running out of puff earlier than usual.



Phew, back on topic

Doesn't always work.

Er... Not looked through this thread very carefully, Chinners?

markg/others - any experience with the parkzone aircraft? I was tempted to buy myself their Spitfire at lunch, rather than get another GWS effort.

They all fly and generally do so very well, however to that end the lines of the Spitfire aren't quite scale, still looks good to me though. You'll struggle to find better as a ready to fly out of the box type of thing.

I've just realised that I have masses of open fields around me and haven't bothered to get an RC aeroplane since I built a balsa glider a zillion years ago.

So, tell me a web shop where I can buy a ready to fly Li-Ion machine for not too much money, please.

What's your skill level and how much can you spend?

Definitely beginner! Can I get anything for 70 quid?

I've got a spare transmitter you can have for a few quid if that'll help (although most come with them nowadays).

Might need one of those as my transmitter was actually AM and the radio reception tended to go "downhill" when I added a motor to the glider...

It'll be my first aileron plane, mind, so I may be overreaching. Up til now I've been flying a three channel rudder/elevator Beaver. I wanted my first aileron plane to be aileron and elevator only, no rudder, to avoid complicating matters.

You might struggle to be honest. This time last year I'd maybe have come up with something but now that sort of money gets stuff that would probably only discourage you. The aforementioned Parkzone are probably your best bet but only the newer ones are Lithium although for the type of model you are after I wouldn't have that as an essential requirement, NiMH with an extra battery or two would serve just as well, this is good trainer type for under £100:

http://www.modelshopleeds.co.uk/catalog ... rrency=GBP

Get a simulator though, your chances of not smashing it to pieces first time out would go from less than a couple of percent to maybe fifty or more with some simulator practice.

I wouldn't worry about it too much really, in many respects aileron and elevator is easier, it's just the type of models that tend to be rudder and elevator only are usually the slower, more inherently stable ones.

Slightly put off by the THIS IS NOT FOR BEGINNERS!!"11!! warnings on their website, mind. Hey ho, feet first

You could come and see me for a RC MASTERCLASS.

If you are confident with the plane you have then it should be ok. Can you fly it around with the plane going where you want rather than just fighting to keep it in the air? If so you should be fine.

Generally yes. I may pick up another high wing trainer for now, though, as I don't want to buy 130 quids' worth of warbird and stick it nose first in the ground at 50mph.

Or: fuck it. Maybe I will.

Thanks MarkG I shall look into it. I was assuming 70 without battery and charger but the one you suggested has the lot. Although I'm not even slightly bothered about it "looking like a real airoplane"

Are they throw-launch then or what?

That one will take off from the ground but can just as easily be hand launched, it depends on the field though, to take off frm the ground it would need to be a cricket pitch or similar.

If you do that, make sure your plane doesn't get taken out by a lusty hook shot from their big number six.

Go for it, you should be fine, just wait for the right day though, ideally a little bit of a breeze to help slow it down for landing and make the hand launch a little easier. Just remember that this is a low winger and might not do the same gentle nod after a stall as your trainer, Spitfires will often drop a wing if their airspeed gets too low. So keep in mind that the plane's speed as it appears to you might not have much relation to its airspeed. I've seen so many good models destroyed on downwind turns because even experienced pilots get caught out this way.

Heh - they were out of stock.

I'll see what I can find on t'internet, but I'll also order the GWS AT-6 Texan I was going to get before.

Oooh - found it for £109 plus postage. "ORDER".

This thread has made me want to get my Riot out again.

Is that your petrol RC car, Grimmeh? Where do you tank around with it in London?

For a quick run, there's a little grass area near my house, and because it's by the thames, the pavements are wider than most roads and go on forever. If I want a good thrash, or I'm giving someone a go that's not had a go before, I go up to Blackheath.