Mike Frith Posted March 18, 2010 Share Posted March 18, 2010 Yep, good advice on the motor, thanks. Anyone wanna buy a BL4030? ... one not so careful owner! Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 18, 2010 Share Posted March 18, 2010 Hi Guys, things are becoming clearer lol, its all good stuff, and it does indeed sound like you are getting a handle on all this smoke taming Mike I simply googled the motor Mike had stated and found the specs I used, sorry If I confused things. The route Timbo advises is my preferred route also, bigger props, slow rpm, and coarser pitch. The problem with modelling light aircraft is the full size props were not very big and when scaled they are not as large as we would like. A 1/5 scale Chippy prop is only 15.5" so you have to make it spin a bit quicker than i like to get tke power required to actually comit aviation All good stuff though Cheers Danny Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted March 18, 2010 Share Posted March 18, 2010 Ground clearance was the issue with a prop bigger than 15". I'd already put a longer nose gear leg on to give a bit more clearance (something else another reviewer mentioned). I shall have to get another and try again with more power and more care in balancing ... it'll be quicker putting it together the second time Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 5, 2010 Share Posted April 5, 2010 Ok fellas, we're back in business, sort of, and I'm after your input again. I've bought another Bulldog and have nearly finished putting it together. Also bought some new powertrain stuff, most of which are the cheaper versions: Motor: XYH50-55 580kv (http://www.giantcod.co.uk/xyh5055-580kv-brushless-outrunner-p-403285.html)ESC: RCSmart 80A (http://www.rcuniverse.com/market/item.cfm?itemId=482332)Lipo: 2 x BQY 3S 3300mAh 20C (http://cgi.ebay.co.uk/3S-3300MAH-20C-11-1v-LiPo-RC-R-C-Battery-Trex-450-/290412761908) The 2 batteries are connected in series to make a 6S Ran it on a test bench with 14x7E APC prop, got 26A peak, 20A nominal. Voltage measured at 24V static, 17.5V under full load. Batteries got a little warm in 30 seconds. Then tried a 15x10 prop, output virtually the same. So that's just 350W! Not enough to get my 7.7lb Bulldog into the air. So what am I doing wrong? Is it the cheap gear I'm using? If so, which components?I'm using a regular ammeter/voltmeter. Do I need a proper power meter? Would appreciate any feedback you have ... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 5, 2010 Share Posted April 5, 2010 Batteries are sagging for starters. A good 6s pack should hold around 3.5V under the modest load of 25A or so. Thats 21V and your only showing 17.5V Suspect the ammeter possibly also - you really ought to be using a wattmeter. The links you included are wrong, but anyway, a 580 Kv motor on those props should be showing more power for sure.For Instance....On 6s LiPo, my 480Kv KMS motor shows a whopping 900+ watts with just a 12 X 7 prop and pulls around 43A. Either your data is wrong, or the motor is not 580Kv. Even if batteries held 21V , at a measly 25A thats still only 520+ watts. Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 5, 2010 Share Posted April 5, 2010 The links work OK for me ... try scrolling down the page ... Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted April 5, 2010 Share Posted April 5, 2010 Hi Mike, Timbo has beat me to it lol. The voltage on those cells is definitely not holding up well. I think you definitely need to invest in a wattmeter. They are probably the single most importatnt piece of test equipment for electric flight. Where are you Mike, anywhere near the Midlands? Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 5, 2010 Share Posted April 5, 2010 Just discovered that one of my batteries is faulty. After another test it's gone completely dead ... so I need to get another before I go any further. I guess I'll get a wattmeter at the same time Any suggestions as to make and model at the cheaper end of the range? I'm in Gloucester, so just south of the Midlands. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted April 5, 2010 Share Posted April 5, 2010 Just a bit too far for me to get to, I am afraid. I have had trouble with the Tornado Wattmeter, even the replacement went wrong so would not recomend one of those. I have a Watts-Up meter and thats been fine. I think BRC do a cheap and cheerful unit. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 5, 2010 Share Posted April 5, 2010 Posted by Mike Frith on 05/04/2010 13:01:29:The links work OK for me ... try scrolling down the page ... No, you have not posted the links correctly Mike.Please read this. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 5, 2010 Share Posted April 5, 2010 I have the Astro flight "Whattmeter" which is a good solid piece of kit, but rather old these days ( and expensive ). Some of them have a rather handy feature of "holding" the highest figure recorded in a session so that you can easily see the peak figutres achieved during a test run. I think it may be the "Watts up" that Danny mentioned??Tornado brand.....wouldnt touch anything with that label after bad experiences a few years back Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 5, 2010 Share Posted April 5, 2010 Incidentally, I note you are using cheap EBay batteries, and although some may well be OK, I cant see the point of taking the risk these days, when proven good quality and excellent performing packs are available for very little money from the likes of Giant Cod.I mean, whats wrong with these....excellent VFM packs , and chargeable at 5C as well.If you want extra capacity these at just £27 are also available - 4000mAh I have several , and they are all performing very well indeed.Edited By Timbo - Administrator on 05/04/2010 15:53:37 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted April 5, 2010 Share Posted April 5, 2010 This looks great value from GC, the reviewers seem impressesd. However I have not any first hand experience, but the price is lower than I have seen elsewhere. Anybody else got one of these and can vouch for it? Watt meter Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted April 5, 2010 Share Posted April 5, 2010 Nope, but as you say, sounds like a cracking good deal. Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 5, 2010 Share Posted April 5, 2010 Previous lipos bought direct from Hong Kong have given me good service and at around £10 each (including postage) it's a tempting proposition. Have read some OK reports on these too and some guys in the club swear by them. I've damaged a couple in crashes which would have been more costly with other packs. The GC 5C packs do look good though. I was going to get the GC wattmeter but it's out of stock, unfortunately. Have found a Turnigy wattmeter at a good price ... see here Quote Link to comment Share on other sites More sharing options...
Tom Foreman Posted April 5, 2010 Share Posted April 5, 2010 65W per lb!!! And here's me wondering if I'll be OK with 130 W per lb on a 90 sized Corsair always better to have more power than you need Mike thats what the throttle's for, if you can't pull the amps you want you can always try going up on voltage but as Tim and Danny have commented sounds like your batteries are knackered. What charger do you use for charging them, and more importantly are you balance charging them? Cheers, Tom Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 5, 2010 Share Posted April 5, 2010 I have a Mystery B6 balancing charger and always balance the cells. Had it over a year and never had problems with charging other lipos. Haven't been pulling over 20 amps before though. Quote Link to comment Share on other sites More sharing options...
Jason Murphy Posted April 25, 2010 Share Posted April 25, 2010 hi,getting back to the bulldog thread,i maidened mine yesterday.first flight was a nightmare as it did not want to rotate on takeoff.once off the ground i was holding in about half elevator to keep it level.managed one curcuit and landed.i had set the c of g to around 70mm to be safe!! lesson learnt.i then reset the c of g to 75mm and it flew better but i think it could still bite the unwary especially on steep turns.(it flicks quite badly if you pull full elevator)i now plan on putting the c of g to the recommended 80mm so will get back here when i ve flown it again. Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted April 26, 2010 Share Posted April 26, 2010 Hi Jason. Sounds like a similar story to mine ... except mine was underpowered too, which became too much to handle. Glad you got yours down safely. I've bought, and just about finished, a second Bulldog. Also bought some new batteries (two from China and two from UK, to compare) and a higher kv motor ... and a wattmeter! After testing the batteries, I've determined that the ones I was using before were very poor performers. Power tapered off after 30 seconds! All new batteries, even with the old motor, give much more power ... 630W with a 14x7 prop, 850W with a 15x10 prop (that's 110 Watts per pound). So, I needn't have bought the new motor! Ho hum. Just when I thought this hobby was getting substantially more expensive, just read some stuff about problems between 35Mhz gear and brushless motors!! So it now looks like I might have to upgrade my 35Mhz set too I took up the hobby because flying the full-size was too expensive. Perhaps I'll go back to renting Cessna 172s at £150 an hour ... I think it's cheaper Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted June 26, 2010 Share Posted June 26, 2010 Most of you guys are probably sipping cold beer at Greenacres at the mo. I was going to go but, alas, no 'A' certificate ... so decided to enjoy the good weather down our club field instead Anyway, I maidened the Bulldog (Mk2). She flys fine, if not a little fast ... probably due to the fact she weighs over 8 lbs. Stacks of power with my long tested power train ... can command over 1200 watts if I need it, that's around 150 watts per pound! Got 5 minutes flight time and used around half the battery. It was all videod, so you can see it ... Edited By Mike Frith on 26/06/2010 21:50:23Edited By Mike Frith on 26/06/2010 21:50:59 Quote Link to comment Share on other sites More sharing options...
Mike Frith Posted July 14, 2010 Share Posted July 14, 2010 Few more photos at http://www.glos-mfc.co.uk/blog/blog10/july10/july10.htmEdited By Mike Frith on 14/07/2010 18:35:46 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 14, 2010 Share Posted July 14, 2010 Looks great Mike, well worth all the work. As you say plenty of power Quote Link to comment Share on other sites More sharing options...
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