Yorkman Posted January 28, 2010 Share Posted January 28, 2010 In a triump of optimism over reality, I'm now halfway through another GAD Mosquito. The last one was written off after yet another wingover/splat caused by assymetric thrust, so when I bought this one I also bought a(nother) pair of engines recommended and supplied by GAD. I had already replaced one of the hobbywings 12amp ESCs http://www.giantcod.co.uk/hobbywing-pentium-12amp-speed-controller-p-327.html as there seemed to be a problem with it. So, theoretically, two identical motors and ESCs. Well I connected up the motors today, and already there are two issues- 1-when the throttle is shut the port motor stops immediately while the stbd 'runs down' for a couple of seconds, and 2-if I open the throttle 'click by click' on the trim, the port motor starts spinning a couple of clicks before the stbd. I am fairly certain the two ESCs are in their 'default' settings, but will check again with the program card, and I have disconnected the red wire from one of them. Any thoughts, anyone? Didn't think it was supposed to be this hard....Edited By Yorkman on 28/01/2010 23:30:26 Quote Link to comment Share on other sites More sharing options...
Yorkman Posted January 29, 2010 Author Share Posted January 29, 2010 If, as seems inevitable, the only solution is to try another pair of controllers, would the panel recommend Turnigy or Etronix? Quote Link to comment Share on other sites More sharing options...
Always broke Posted January 29, 2010 Share Posted January 29, 2010 I would buy Castle Creations along with the PC interface lead.Not cheap but they will work properly and can be set up on your PC properly as well.They have always worked perfectly for me Quote Link to comment Share on other sites More sharing options...
Andy Harris Posted January 29, 2010 Share Posted January 29, 2010 One will always start before the other, its the nature of tolerances in components. However there is a difference between the negilable thrust difference at start-up compared to the running thrust needed for flight. Once the motors are running at speed, if you can hear a beat or drone you'll know the motors are within 10's of rpm between each other. The stopping behavior could be additional friction in the motor - you'd notice that! or ESC settings - most likely. You didn't say if you have the props rotating in opposite directions - you'll need that on a smaller model. I use a pair of the exact same ESCs in a Googlie - they are perfect! Note that I use differential thrust mixed form the rudder and therefore I could trim any speed differences out at the TX. I don't need to, they are matched by default. Andy Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 29, 2010 Share Posted January 29, 2010 Motors not engines Yorky Its also possible that one ESC is set for braking and he other is not......this will cause the immediate stopping of the braked one. The hobbywing / pentium / turnigy controllers are usually fine.Edited By Timbo - Administrator on 29/01/2010 07:56:18 Quote Link to comment Share on other sites More sharing options...
Doug Ireland Posted January 29, 2010 Share Posted January 29, 2010 Andy makes a good point regarding slight differences in electronic components. Do ESC manufacturers offer "paired" ESC's for just this type of application? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted January 29, 2010 Share Posted January 29, 2010 thought there was a recent article in the RCME/nigel hawes about running two b/less motor's off one controller/esc...which i thought was taboo-but it said it was feasable...might be a solution ..... ken anderson Quote Link to comment Share on other sites More sharing options...
Doug Ireland Posted January 29, 2010 Share Posted January 29, 2010 I wouldn't have thought one ESC would be smart enough to discriminate the feedback from two motors Ken. Any idea which issue that article was in, wouldn't mind reading it? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted January 29, 2010 Share Posted January 29, 2010 doug-cannot remember where i was yesterday.............saying that i'm sure there was mention on a thread post on here...and timbo replied and commented on it......he'll let you know better..... ken anderson the memory man..... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 29, 2010 Share Posted January 29, 2010 It was a few issues back, but dont remeber which exactly - my comments were simply that in my experience I never had great success firing two motors off one ESC - the timings involved are simply too difficult to handle in most cases. Castle creations did have a model a few years back that claimed to work with two particular motors, but thats about it.Nigel may well have been lucky, but I still dont recommend it - its only my opinion of course,- but I also added that with the price of perfectly good ESCs being so low these days, why would you bother . Maybe for a real cheapy little foamy or similar, but I just wouldnt risk it on anything half decent. Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted January 29, 2010 Share Posted January 29, 2010 I agree with Timbo, sounds like you have the brake activated on one of the ESC's to give the effect you are having at shut down. Try switching the motors over. If the situation is the same after testing then the issue is with the ESC. If it swaps over then you have an issue with one of the motors being a little tight. I see that it is not the same motor that is slow to start and quick to stop, but is it the one running the BEC? This could just be a result of the BEC lowering the voltage slightly which I do have with my Mosquito. This will always be the first motor to show signs of battery voltage sag. Lastly, are you testing both motor / ESC combos off the same battery or 2 separate ones? Could it be a battery issue? Lastly the issue of 2 motors on one ESC is a no go as far as I am concerned with a brushless motor.Edited By Andy Gates on 29/01/2010 18:59:21 Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 30, 2010 Share Posted January 30, 2010 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 5, 2010 Author Share Posted February 5, 2010 Ok, latest situation is- went back and checked esc settings, and reset throttle travel. Motors then started at the same time, tho the port still stops immediately while the stbd runs on slightly. The port motor is stiffer to turn, and if you flick them over with the prop, the stbd spins noticeably more easily. I have mounted the model on a swivelling mount this evening, and, no surprise, I am getting more thrust from the stbd motor (I'll try and put the video up later). My next move is to swap the motors, as it seems they have differences, but that will prove once and for all if it is mismatched motors or differences in the escs. Onwards.... Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 5, 2010 Author Share Posted February 5, 2010 Posted by Andy Harris on 29/01/2010 07:43:59: One will always start before the other, its the nature of tolerances in components. However there is a difference between the negilable thrust difference at start-up compared to the running thrust needed for flight. Once the motors are running at speed, if you can hear a beat or drone you'll know the motors are within 10's of rpm between each other. The stopping behavior could be additional friction in the motor - you'd notice that! or ESC settings - most likely. You didn't say if you have the props rotating in opposite directions - you'll need that on a smaller model. I use a pair of the exact same ESCs in a Googlie - they are perfect! Note that I use differential thrust mixed form the rudder and therefore I could trim any speed differences out at the TX. I don't need to, they are matched by default. Andy How do you do that then Andy? There is no rudder on the mossie, so if I can use the rudder channel and balance the motors on tx settings, then that's my answer. Any advice welcome! Quote Link to comment Share on other sites More sharing options...
Andy Harris Posted February 5, 2010 Share Posted February 5, 2010 Yorkman. I dug back through my previous posts and found this snippet: I mixed throttle to flap at 100%, the second motor is on flap. Mixed rudder to throttle at 40%, Mixed rudder to flap 40% in the opposite direction. Selected Delta and set the sensitivity of the elevators using rates. Now I have a posh DX7se I'll need to copy the settings from my old DX7 this weekend so I'll be reminding myself! In your case you'll probably mix to AUX2 and 40% might be a little high. The Googlie can be flown in 3 Badmington courts! Andy Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 5, 2010 Author Share Posted February 5, 2010 Hi Andy I've a DX6i, so may be a bit different-I was mucking about this morning with the second motor plugged in to rudder channel, and was getting near something workable, before the battery went flat! I tried plugging in to flap channel, but the motor just ran constantly. When you say 'throttle to flap at 100%', what does that mean exactly? With the mixes on the DX6i both channels can be adjusted from -125 to +125...... Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 7, 2010 Author Share Posted February 7, 2010 I have managed to get something workable. Throttle/rudder are mixed 80-125, whilst rudder 'sub-trim' is set to 98 (I think...will check later). With the model mounted on a swivelling base, motors now start together and there is no noticeable 'swing' any where through the rev range. An added 'bonus' !? is that I have yaw control as the rudder control throttles the stbd engine separately. The only issue I haven't been able to overcome is when the battery is connected, the stbd esc thinks that the tx 'throttle' control isn't fully closed, so beeps away until I give a flick of right rudder, whereupon it shuts up and everything works fine. So I'm running out of excuses to not test fly the thing...... Quote Link to comment Share on other sites More sharing options...
Andy Harris Posted February 7, 2010 Share Posted February 7, 2010 Yorkman Two thoughts: a) if you use flap you need to inhibit the switch, otherwise inadvertent operation of the flap switch will cause a spin. [On the DX6 I think it will be associated with the flight mode swich] b) The ESC sees a pulse train a little over 1mS so goes into program mode. So removing the sub trim will avoid this. My son has a DX6i and in some ways the menus are better than the DX7, quicker to get through etc. PS. I'd ordered a 12A rather than 10A esc so the Googlie will have to wait another week - which is a pity because we only have three badmington courts to fly in this afternoon. Andy Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 7, 2010 Author Share Posted February 7, 2010 came up with a cunning plan.....the 'Coota' amphibian my gorgeous Brazilian wife bought me for christmas has removeable wheels, which masking taped beautifully onto the Mossie nacelles...a sacrificial ventral fin/tailskid, and we were ready to go! An empty stretch of tarmac road on the edge of the plain-and off we went. First attempt, she left the ground, but immediately obvious c/g too far back (which is what did for #1)-it's obviously absolutely critical on this model-but as she fell into grass from 3' altitude, just needed a dust off and remove mud from props. Shifted battery 3/8in forward, tried to calm my nerves, and went for it again-success!! we had a flying machine!! Absolutely no assymetric thrust issues, flew like on rails-and after a couple of minutes (it was flippin cold!) managed to put her down safely back on the tarmac. Let's hope that's the first of many.Edited By Yorkman on 07/02/2010 16:43:56 Quote Link to comment Share on other sites More sharing options...
Andy Harris Posted February 7, 2010 Share Posted February 7, 2010 Nicely done! Quote Link to comment Share on other sites More sharing options...
Yorkman Posted February 7, 2010 Author Share Posted February 7, 2010 Thanks mate Quote Link to comment Share on other sites More sharing options...
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