the unmagnificent man Posted July 31, 2013 Share Posted July 31, 2013 Which motors please. Hi all, I'm back again at last and Ive decided to give electric flight a go. Well I recently came across a plan I've had for ages and thought I'd lost. It's a 49" skyvan. The plan shows two cox motors but I want to fit 2 electric motors. I started the build 10 days ago and apart from the engine cowls and bits that can't be fitted until I have the motors etc its finished. Now then. You are going to ask what's the weight, well I don't know because I'm not sure how much the motors batteries speed controllers etc will weigh. I am pretty sure that I have to use two identical motors, as you do with ic and I'm pretty sure you need one speed controller with each motor. I assume you need separate lipos but I'm not sure. I know absolutely nothing about all the numbers watts Kv amps etc but I do know that the max prop size is 6" due to its proximity to the fuselage. I imagine with all the motors fitted etc the thing will come in under 2 kilos (4pounds) I understand there are a million threads on electric setup but after starting to read a few I just got confused. I just need someone to say here buy these, they are cheap reliable and will fly your plane with 11.1v lipos and so many amp speed controllers for x minutes. Thanks. UMM Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted July 31, 2013 Share Posted July 31, 2013 Something like these with 6 x 5 or 6 x 6 props two 20A ESCs and a 2200 mah 3s battery, one battery on a Y lead feeding both ESCs should fit the bill. I'm using these with 7 x 5 props on an old MPX Twin Star I converted to brushless, more power than the direct drive brushed motors they replaced. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 31, 2013 Share Posted July 31, 2013 **LINK** OK on 6" prop, use two ESCs HERE and 1 x 3s lipo. Use BEC from one of the ESCs to power radio gear. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 1, 2013 Share Posted August 1, 2013 Same-spec motors and same-spec ESCs ensure that both motors will run at the same speed (as close as you can get) throughout the throttle range. Also, you should run them both off a single battery to ensure they're each getting exactly the same voltage throughout the flight, for the same reason. Rather than get a single battery that's large enough to run both motors, you could parallel two smaller batteries to get the same effect -- that's handy if you have other models that need smaller batteries. If you're powering your receiver from the BEC in the ESC, you should use only one BEC, as Tim has mentioned, and disable the other by pulling its red wire from its receiver plug and taping it back on itself so it can't touch anything. If possible, get ESCs with switching BECs, as they can generally handle higher input voltages and more servos. If the spec doesn't say what type it is, it's probably a linear BEC, which is generally limited to 4 servos on a 3S battery or 3 servos on 4S. An oft-quoted rule is that you need anything from 50 to 200 watts for every pound of flying weight. My 1/5 Piper Cub, and my Flair Magnatilla, are both flying very nicely on 85 watts per pound, and my TwinStar is 79 watts per pound. Figuring all-up flying weight is a bit of trial-and-error, trying different motor and battery combos until you get something reasonable. Check out the weights of the combos suggested above, and see how they look. Quote Link to comment Share on other sites More sharing options...
the unmagnificent man Posted August 1, 2013 Author Share Posted August 1, 2013 Wow, BECs and ESCs together with 3s and watts per pound, phew. I think I might just try two of the motors and speed controllers suggested by Frank and Tim, thanks. I already have a 2200 3s Lipo sitting in a drawer. Ill come back and re read the bit about cutting wires once I have all the bits and know they work seperately. And then Ill post my setup details and see if someone can or wants to work out the power to weight ratio. Thanks to all who helped and pointed me to the website that gave me the kid in the sweetshop feeling and helped to lighten the burden of carrying too much money. I didnt even know that I wanted so many things.... UMM Quote Link to comment Share on other sites More sharing options...
kc Posted August 1, 2013 Share Posted August 1, 2013 Note what it says on the reviews about this type of engine mount - they rely on 2 grub screws which can come loose. If you Loctite them in you probably wont get them out again and this makes access to the mounting bolts difficult because they dont pass the motor casing. You probably need to drill & tap for another grub screw at 90 degrees to the others. And possibly put the mounting bolts in from behind if they are long. It's all OK if you plan for it first. Quote Link to comment Share on other sites More sharing options...
kc Posted August 1, 2013 Share Posted August 1, 2013 Note what it says on the reviews about this type of engine mount - they rely on 2 grub screws which can come loose. If you Loctite them in you probably wont get them out again and this makes access to the mounting bolts difficult because they dont pass the motor casing. You probably need to drill & tap for another grub screw at 90 degrees to the others. And possibly put the mounting bolts in from behind if they are long. It's all OK if you plan for it first. Quote Link to comment Share on other sites More sharing options...
the unmagnificent man Posted August 2, 2013 Author Share Posted August 2, 2013 KC Thanks for the info, I noticed a lot of talk about that on the reviews. I'll make sure they are well and truly fixed. OOPS I just realised that when I ordered my 2 ESCs I forgot to press update on the shopping cart and only ordered 1. Drat. 2 motors and one ESC, mmm I have got a spare ESC in my drawer, it's a different make to the other but the same amps. If I use 1battery to power both motors will it make a difference if the ESCs are different makes? IE 2 identical motors, 1 battery and 2 different makes of ESC both rated at 30 amp? Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted August 2, 2013 Share Posted August 2, 2013 The problem is likely to be that the ESCs will have different responses to your throttle input. You may be able to mitigate this by putting one ESC on the throttle channel as usual, and then programming another channel to mirror the throttle channel, and put the other ESC on that. Then you have the opportunity to at least adjust end-points so they start and stop at the same time, but they may still vary within the throttle range. Quote Link to comment Share on other sites More sharing options...
the unmagnificent man Posted August 2, 2013 Author Share Posted August 2, 2013 Thanks Allan, looks like ill just order another ESC l Quote Link to comment Share on other sites More sharing options...
G-JIMG Posted April 18, 2017 Share Posted April 18, 2017 Up until now I've been a confirmed 'petrol head' but I'm about to start a scratch build of a King Air 350CER (Twin). I plan on using twin electric motors (unfortunately I don't have £8,000 spare for a couple of Wren Turbo Props!) but, as an electric noob, I need help on Motor/ECS/Battery selection. Plan is for a ~1/10th scale model so the current best guesses are: All Up Weight ~ 15 lb Wing Span ~ 69" Wing Area ~1,800 sq in Propellers Scale 4 Bladed, 10" dia (E-Flite 10x5) Ideally I'd like to position the motor batteries in the nacelles (the CER variant has enlarged nacelles/tanks). Any help on Motor/ECS/Battery selection would be appreciated. Quote Link to comment Share on other sites More sharing options...
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