Nigel R

Posted by Geoff Sleath on 06/10/2016 12:46:30: I seem to recall seeing a programme or YouTube video of an airliner (can't remember the type) flown remotely from a chase plane and deliberately crashed with crash dummies as 'passengers' to see how safety could be improved. "The Plane Crash", channel 4. It's on their 'on demand' web page.

"The key is to use thick Ali as that will help dampen the noise . A thick walled tube blocked of at one end with a smaller tube with it ." My dad made a few simple expansion chamber types using thick wall ali tube, exactly like that. Ali discs were cut to block both ends. A flat was filed where the exhaust mounted on the tube. Mounting bolts went right through the thick wall tube. The outlet tube was stuck into the thick wall tube. IIRC the end inside the silencer was splayed slightly. The whole lot was sealed up with 24 hr epoxy. They long outlasted the original installation.

Tony Most any rate is ok with nicd. They're tough as boots and easy to deal with, in an electronic sense, for the charger. The difference is with the peak detection stuff, which fast chargers use as the first (and sometimes only) method of sensing when the battery is full. On a nicd, when you go to "only just past full", the cell voltage drops quite fast, but with a nimh, the voltage drop is much slower. The result of this, is the nimh charger has to be more sensitive to this voltage drop. This of course originally meant a bit more developed circuit with more & better components and a bit more cost. Manufacturers looking to make a budget charger would have had a sketchy peak detection (which brings the risk of overcharging). These days, cheap chargers just use a controller chip - the chip has to be set up right though, again, something you'd trust is done with a reputable charger, possibly not with a cheap one. The voltage thing is best explained with a picture (see http://www.mpoweruk.com/chargers.htm) , note the difference between the blue and green curves: Nimh will show a bigger peak drop with higher rate charges (~ 1C). But a slower (~0.5 C) rate gives a very subtle drop - bad news if your peak detection is a bit borderline. As Martin said, best advice, get a reputable charger.

Lucky escape!   Nimh and peak detect and a cheap fast charger = not a good mix.   Nimh fast charge ideally needs a temperature probe which responds to a negative temperature changes as well as a maximum temperature, peak voltage detection (and far more sensitive than nicd), negative voltage change detection, and a timeout for the fast charge (which means the charger needs to know the size of the pack).   Or, trickle charge them at 5% of C for 24 hours.   There was a lot to be said for the robustness of nicd.   "600mA would sound reasonable to me for a fastish charge and the charger should have no problem in detecting the peak provided that it is set for the correct type of cells"   600mA charge rate into a 1100mAh pack is almost the worst rate to use on nimh. The voltage peak is very weak at this charge rate. A full 1100mAh charge rate would be better. Edited By SuperNash on 29/09/2016 13:26:10

Posted by Jon Harper - Laser Engines on 28/09/2016 13:08:00: Yup, 10% oil (ML70 or Klotz) is all good. Jon Any thoughts on relative merits of the model oils in use? I know ML70 has been around ages, is Klotz much better? And the Fuchs oils (which internet rumour suggests is in Weston mixes) are they much different? And MT have their own "EDL2" now... Confused!

Posted by Jon Harper - Laser Engines on 27/09/2016 22:22:33: I know model shop leeds will ship, as will elite models I think. No idea what the shipping charges are like though. The cost of the base fuel should not be more than 16 or 17 quid. Unless you are flying heli's or using a ys 5% nitro is more than satisfactory for all fixed wing engines Elite do Model Technics 5% Propower for £19 a gallon and postage (which took 2 days) was £5. Same postage cost for any amount of fuel, although when you get to six gallons you're over £100 and they post for free. They also do the firepower plugs. Presumably a phone call could source any of the other MT aero blends - the others listed online were for cars. No connection - happy customer, British made kit, etc.

After the worlds smallest monoplane, I can't not post the worlds smallest biplane Stits Sky Baby. 1/4 scale would be a big whole 21.5in on this one...

Posted by Dr. David on 26/09/2016 13:34:57: In case you have not noticed there have been many catastrophic failures on full size aircraft that have abviously been thoroughly designed/tested. Accidents happen, get over it! I think I'm on reasonably safe ground when stating that one thing the full size industry certainly doesn't do is "get over it" when a catastrophic accident occurs. A vast amount of effort goes into ensuring "it", whatever "it" was, doesn't happen again. It's thanks to that attitude that the accident rate in full size is as safe as it is. Or perhaps I'm misunderstanding, and you're only referring to these unimportant little bits of foam and wood that get flown around by RC guys. Except that at 100kg this is as big as a small fixed wing microlight - fine, nobody gets on board, etc. But 100kg is still a big old whack of stuff to lose control of because it hasn't been built strong enough. If this passed the inspection procedures, the inspection procedures aren't good enough. Feel free to disagree.

Why not build large models? Up to the builders really, its their time & money & enjoyment. Some people collect stamps and others go dancing. Personally, if I had £000s burning a hole, looking for an aviation sort of home, I would be more likely to look at building / flying full size. Back in RC land, I find sub 20 size to be a bit too small. All things being equal, a 20 size will fly ok, 40 size better, 60 size better yet. But, 40% and beyond just looks too much faff to transport - for me. YMMV...

"well I was searching for an online distributer" **LINK** I recently found them the cheapest for a single gallon order.

"First video - A rather expensive error of judgement. I don't suppose the Greek government have enougfh cash to do that too often." Actually there are now other videos posted highlighting the engine failure - https://www.youtube.com/watch?v=LE3GpxD_IR0 Around ten seconds in is the slow motion bit where you can see the flash from the exhaust. Maybe it is more a case of the pilot having nowhere else to go, with an autorotating heli at ground level; perhaps the beach had people on it, in which case he did a pretty good job of a sharp turn around and safe ditching.

"I've found that the cheapest batteries you can buy from Halfords are way better than the "name" brands for longevity! (Yes, really!)" If I remember right, Halfords own brand are rebadged Varta (Silver?). But not their "A" grade product. The Halfords ones are (somewhat predictably) a little looser in the quality department - you might get a good one - or you might not. From memory Halfords are rated a bit lower in both total capacity and CCA. Having said that both our current cars (and some previous) have Halfords batteries, and they're holding up just fine.

Crikey. You sound a bit busy! Part time helper maybe?

Jon how many of you are there at Laser?

I'd use one of these for the 8mm -> 10mm opertation:   http://www.ebay.co.uk/itm/RC-6-7-8-10mm-4-Step-Metric-Prop-Reamer-RT646-/322054871262?hash=item4afbf758de:g:aBwAAOxyXDhSoFXB   The existing 8mm hole will keep it nicely lined up while it cuts the 10mm hole. Edited By SuperNash on 07/09/2016 15:10:23

Works for me: Keep the joint clean. Never sand the tip, keep it tinned. Wipe tip on damp sponge after each joint. The things you are joining, they must be clean. Flux can help with bigger joints, but clean it all off after making the joint. I use: 120W with a big flat tip for U/C and cabane size joints. 25W for your average electrical connection. Cheap torch for plumbing. I like Geoff's story about the GEC telephone joints. A bit of skill goes a long way!

Yep, looks like a hornet for sure. We get a few around our way every year. They're usually a bit over an inch, maybe inch and a half? They make a reasonably distinctive low pitch buzzing when they fly, vs a vs wasp/bee buzzes. Leave them alone, they leave you alone... usually. Standard yellowjackets are far more annoying, especially this time of year.

The public perception, as I hear it around and about and on forums not devoted to model aircraft of any flavour: Drones = things with four spinny things and a camera, only used to look into peoples houses while they're in the buff. Model airplanes = small Spitfire, or possibly a Tiger Moth if it has two wings. The first one is currently a fad toy. The second holds no interest for the public whatsoever.   If you fly multirotors of any kind, you're flying a drone, you're a naughty boy, and if you haven't been yet you will be - quick let's ban them, from, everywhere. Or something. Quick. Something has to be done. Action must be taken. Blah blah blah. I fully expect to see more stories like the one under discussion, in the near future, until some other toy becomes popular (and therefore dangerous to mankind) and has to be banned... About twenty or thirty years ago, computer games had to be banned because they were turning children into serial killers. Mobile phones give you brain cancer, and even if they don't they turn you into a facebook vegetable. I'm rambling a bit. Sorry.

The Brietling Stearman pair went over nice and low last weekend. Pitts G-EWIZ has been over a few times lately, sadly has not done his display routine directly over our house again. We get a lot of regulars - the Staverton training aircraft - DR400, 172/152?, several flavours of light heli that I don't recognise; the local air ambulance (Eurocopters) are out all the time. The Archer (or is it Cherokee) based at Ledbury comes over regularly too. The other regulars are the Hercs, too, often very low, and Chinooks. Now I come to mention it its surprisingly active around these parts. I think the civvy pilots do sightseeing over the Malverns. The Hercs (I assume) are practising low runs over the Cotswolds, past us and on toward Brecons way. Edited By SuperNash on 19/08/2016 11:59:13

crikey well done to the pilot on quick reactions but that's really very, very close to the crowd

Drug regimes? There will always be some athletes on them. Some will get away with it. Some will get caught and outed. Some will get away with it and only get caught later, to have their shiny prizes taken away and given to other athletes instead. At least there are agencies at work attempting to keep the cheating types at bay. C'est la vie. Edited By SuperNash on 08/08/2016 16:59:03

Olympics? Minority sports given two weeks airtime and good coverage, once every four years. More power to it, I say. Certainly I'll be watching some track cycling, weightlifting, canoeing, rowing, jumping, throwing and sprinting for a couple of weeks. This thread is far too grumpy!

maybe too simple an idea, but turning the model upside down always worked for me...

Couldn't agree with Peter more. One good pack, mount it in such a way as to be isolated from vibration as much as possible, and two switches if you must. Simplicity is worth a lot. "cause a 0.7 volt drop across the diode (assuming a silicon type) " For what its worth, a well picked shottkey diode will drop far less, 0.2V or thereabouts.   ". Continuing to charge a NiMH pack at low current is not best practice but will not lead to thermal runaway as far as I've always been lead to believe." Indefinite trickle charging on nimh is OK at very low rates. Less than C/10 I believe. Which gives at least a 15 hour charge time, by the time charging inefficiencies are done with.     Edited By SuperNash on 01/08/2016 17:59:22

That's a better explanation that I would have given Shaunie! "Perhaps there's something I've missed regarding "negative voltage characteristic" - if so, please explain how this affects the situation." The only thing I'd add is that the negative voltage characteristic means, if you continue to charge a fully charged nicad/nimh, the voltage continues to drop; that means that if pack A starts feeding into pack B, the situation becomes worse, pack B just keeps dropping voltage which makes pack A feed more and more into pack B. So pack B becomes more charged, and its voltage drops, pack A feeds even more current to pack B, and so on an so on until pack B goes pop.   Edited By SuperNash on 01/08/2016 13:27:17