PatMc
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Everything posted by PatMc
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Posted by Peter Beeney on 24/01/2011 21:27:36:PatMc, Is that a Yagi aerial? Directional, presumably? I think it is I'm going from memory. IIRC Maynard & a colleague adapted the aerial to use with a model Tx in the year before setting the record. Seems I remembered the altitude incorrectly I thought it was just under 30,000ft but at that height what's 3000ft between friends.
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Posted by Alan on 24/01/2011 21:47:34: How long does it take to charge at 1C. Alan Just over an hour from fully discharged. Less if the battery's part charged already.
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If your Rx has failsafe you can use this for a single handed range check. Just park the Tx as Peter said if you want to check the full range or with the aerial down for simulated range chek. Then walk away with the model. When the range limit is exceeded the servos will drive to the failsafe positions. PS Maynard Hill set an altitude record of 29,000+ft around 1970 using a Tx with a YGI aerial. Edited By PatMc on 24/01/2011 20:58:33
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Fly Cam crashes explorer
PatMc replied to Flanker .'s topic in Aerial Photography, First Person View, UAVs
Posted by Flanker . on 22/01/2011 16:48:51: Instructions mention write speeds but shop only had one make of card. Do they come at different speeds ? GW F Yes the cards come at different speeds, I use a Sandisk 2GB card, IIRC from Amazon. They are currently about £4 inc postage.I've had my Flycam since 2008 so your's may have some upgrades. I had great difficulty upgrading the firmware but my son managed after some poking around. The new features included being able to invert the image being taken, which is handy for mounting the camera on top of the fuselage etc. The battery was poor, only good for about 10mins of video when fully charged & charging via the USB not really satisfactory. I've since done some mods so that I can switch on/off in flight & run it from a separate external single 600mAH lipo.Downloading direct from the camera seems to be limited to USB1 speed so I always remove the card & download via a card reader. -
Steve W-O, I agree to some extent with your comment on wattage. It's a measure of power expended not power realised. However even the worse brushless motors nowadays are more efficient than all but the very best brushed of a few years ago. The prop dia & pitch used should of course be matched to the performance expectations of the model as well as the motor characteristics. And there are variations in the efficiency of props. All in all Watts readings should be considered as an indication not a measure of power.However static thrust isn't even that. It's a useless measure for a moving model. As soon as the model moves thrust diminishes until it's equal to the drag caused by forward movement. It's quite possible to obtain static thrust greater than model weight which wouldn't maintain the model flying S&L let alone take off.Edited By PatMc on 21/01/2011 19:20:47
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Posted by Tony H on 21/01/2011 17:09:23: Thanks guys. It's for a little Ripmax Coyote Glider (55" wingspan), it used to be run with a 6x4 prop on a speed 400 and 8.4v Nicad. What I have is a speed 400 equivalent brushless motor 2830/15 930Kv using a 9X5 foldng propeller I get 9.5amps and 109Watts max the plane weighs 1.58Lbs with the 2200 3s Lipo in it wihich gives me about 69watts/Lb and an estimated flight time of 19 mins. What do you think of this setup?Edited By Tony H on 21/01/2011 17:12:00 I think you'll find it a quantum leap in performance compared with the speed 400. I don't think thermal gliding will be it's forte but it should fly like a slope soarer.
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As Chris says it depends on the performance you want & style of flying that suits you. I've got 4 powered gliders that have flown satisfactorily on power ranging from 46W/lb to 136W/lb. Lowest power/wt ratio was on an 9ft open structure O/D using 7 cell nicads that needed a couple of minutes of motor run before gliding so only 2 or 3 climbs were possible per charge. This model has since been upgraded to 3s lipo & a lower Kv motor increasing power as well as reducing weight to 97W/lb. It now only needs about 30 secs or less of power per climb allowing 7 or 8 climbs per charge. Highest power/wt at 136W/lb is an Easyglider Pro. It will climb vertically & is at my visual limit in 30 secs. Again 7 or 8 climbs per charge which equates to about an hour total flying time without thermal assist. You might be interested in how competition flyers view the power/wt ratio. Up until 2 or 3 years ago BARCS (British Association of RC Soarers) ran a duration competition category based on 200W/Kg & 30 secs max powered climb. This has since been changed to a height limited of 200mtrs within 30secs of powered climb. An out & out power to weight ratio wouldn't be any advantage within these rules except if it was used to climb at a shallow angle as far upwind as possible.
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Posted by Tony Smith 7 on 21/01/2011 13:25:20: Posted by Steve W-O on 21/01/2011 11:45:30: Have you measured the static thrust? No I haven't. I couldn't work out any easy way to do is, so all I can report is that it pulls very hard, and blows stuff off the bench. Seriously it would be interesting to measure RPM. Do any wattmeters do that by sensing the ESC pulses, or do you always need some sort of optical tacho? Edited By Tony Smith 7 on 21/01/2011 13:25:36 I have the older version of the Hyperion Emeter. This meter includes an optical tacho as well as recording Watts, Amps & Volts plus a few other parameters which I don't bother with. I think the new version has increased the data available including a tach sensing the motor directly but it is a relatively expensive bit of kit & seems to really need a number of "optional" extras. IMO a clamp meter is all that's needed for 80% of the time with a tacho & DVM to complement it for the other 20%. IMO static thrust is a pretty useless piece of information unless you intend to hover & even then you only want to know if the thrust's greater than the model weight. Something that can easily be determined without measurement. Posted by Tony Smith 7 on 21/01/2011 13:38:54: The reviewers report anywhere between 13A and 22A with 10"x5" on 3S. I guess I'm right in the middle, although my motor is actually the SK series SK 3530-1100 Yes, that's why I mentioned the reasons there might be for variations from the reviewers. I notice the consensus of reviewers' opinions on the SK motor is that it's less than 1100Kv . I've calculated the Kv of a few motors by using a 6 or 7 cell nicad battery & taking measurements of voltage & RPM (of the rotor body) with the motor unloaded. The only one that's been near identical to the manufacturer's figure has been an AXI the others varied by up to about 12%.
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Posted by Bob Cotsford on 21/01/2011 10:28:21: If it's the old FF7 super with the plug-in RF module, they were prone to cracking in the soldered joints on the pins where the module plugs in. If so, it's easy enough to resolder them.Bob, that would give intermittent output not low power. It was a problem on the FF8 but I don't think it was on the FF7 which had a smaller less rigidly held cct board to plug in to. I've got 2 x FF7s & a FF8.
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Here's the Hobby King page on their version of the motor that I referred to, the reviews are under the item description. I think the inductive load together with switching speed of the ESC smooths the square wave form of the input current to a ripple. However there are voltage spikes that are suppressed by the capacitors but I wouldn't expect these very short duration spikes to have any effect on any ammeter.
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The current seems about right judging by the customer product reviews posted in HK website.There are some variation between reviewers but that could be due to differently calibrated meters, condition of battery, the true Kv of individual motors & variations of 10x5 props used in each case (even when they are the same make). I'm not sure that I'd agree that the ingoing current would have a square waveform.
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Since you have unsatisfactory range testing with the aerial collapsed any fault is unlikely to be aerial connected.It could be a faulty or non-compatible crystal either the Tx or Rx. Are you using a Futaba one in the Tx & is the one in the Rx from the Rx manufacturer ? If your club have a 35MHz monitor or you know anyone that has this can be used to gauge the RF power output. BTW is the FF7 the modern version or older type (FP-T 7UPS) ?
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Posted by MarkyMarc on 18/01/2011 17:43:49: Hope we haven't put Stewart off! Conspiracy theory - maybe he's a ringer? I wondered if he might be a "she" trolling in a different persona.
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I think the last time this topic was raised the OP gave a plausible presentation arguing the opposite to the OP of this thread. When the flaws in her argument were pointed out she admitted that she had been trolling claiming it was in order to demonstrate how easy it was to convince those she thought gullible.
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Time for the biggest Billy Goat Gruff to arrive methinks.
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Posted by Tony H on 17/01/2011 20:57:37: So what would th max be on my lipos as they are 11.1v 3s?11.1v is the nominal operating voltage (3.7v/cell). The fully charged figure is 12.6v (4.2v/cell) So 50W/12.6v = 4A. But in reality this is only approximate. Your charger might settle on a figure slightly above this during the initial charging if the battery is fairly well discharged then drop below this most of the time as the charge progresses Edited By PatMc on 17/01/2011 21:37:22
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Posted by birdy on 17/01/2011 18:19:43: Posted by Tony H on 17/01/2011 18:03:28: My charger says it's 2C capable but it's only a 50W charger. would it be possile to speed the charge up a bit at say 1.5C or 3.3amps? Yes. But it may not be ideal as many chargers have a safety feature which stops them putting too much in, and you would be getting rid of that. But then again, some don't. Try telling your charger that your pack is 1.5 times the capacity you want to charge, and you will get 1.5 times the current (if the charger is any good...). @import url(http://www.modelflying.co.uk/CuteEditor_Files/Style/SyntaxHighlighter.css);@import url(/CuteEditor_Files/public_forums.css); Birdy, if I understand what you're suggesting I think it could be dangerous. I don't see how it will increase the charge current but it would be removing one of the chargers' safety features.Fooling the charger into over-riding the max capacity could result in it continuing to charge a fully charged battery that's past it's peak performance & possibly a little out of balance.
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Posted by Tony H on 17/01/2011 18:03:28: My charger says it's 2C capable but it's only a 50W charger. would it be possile to speed the charge up a bit at say 1.5C or 3.3amps? Tony, I have 3 different chargers. If I enter a current into any of them that will result in a charge rate greater than the max power the charger can handle the current is automatically limited to within the power rating. I think that your charger will behave in the same manner so that even if you entered say 4.4A the charger would limit itself to perhaps 4A or lower. Like Leccy I always only charge at 1C max as I have plenty of spare packs that are charged in advance.
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To charge a 3s battery at 4.4A you're charger would need to have a greater than 55W capability & to charge 3s at 15A would need to be rated over 190W.
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Is this a 5 minute argument or the full half hour ?
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Posted by Tony H on 16/01/2011 21:45:57: Can you use IC props on electric setups or do they have to be Electric Props only? They don't seem much different. Tony I sometimes do when it's convenient & I have a suitable one legacy of my IC days. Also IC props being more robust don't break so easily landing a model with no u/c. Of course at one time there was no option all props were made either for IC or rubber powered models.
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It's looking good Mike. A major weakness in the Mk1 was the unsprung design of the u/c. I don't know if this has been improved in the Mk2.I duplicated a bungee suspension system I had used in a DB Mannock which has proved successful on both models & looks "in period".
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