Nijhuis Mosquito DH98

[Ianto]

I am thinking of building this free RCME(June 2005)plan Mossie with 2 brushless motors + Lipo's.If weight is 40 ozs I figure I need about 15amps@11v per motor.Has anyone built one with twin brushless and how were the motors controlled? How did the model fly?What size Lipo's were used? Any advice welcome.

[Tim Mackey]

Just for starters, that should give around 100watt per pound which should be ample. You will only be likely to hold 11v per battery @15A by using a good quality LiPo with a decent conservative C rate of around 20. Ideally, go for perhaps 12 /1500 ma capacity packs, 20C. This will then be using them at around 10-12C and they should hold voltage quite well ( Flight Power or similar quality )and live longer too !
LiPos....buy cheap buy twice.
I use the F/P 1200s in the sabre, at around 15A, they hold 11.3V, giving a whattmeter reading of 167 watts. I prefer the 1200 to the 1500 as it is a bit lighter.
I sent you a link via email about a motor+esc deal that may be interesting...

[Tim Mackey]

you know thinking a bit further on this.....I reckon you would get away with a bit less power for this model than originally stated. 100watt per pound is pretty damn high, and any well designed and balanced model should fly quite acceptably on around 70 watt per pound. After all, this is not a ballistic hotliner you are doing is it ?

[Ianto]

thanks Timbo, I thought the higher power might allow a better handlaunch getaway.
Another thing I notice on the plan is a 2deg. engine offset to counteract torque effects. Presumably I could reverse one motor, use a pusher prop and eliminate torque.APS do pushers, are they otherwise identical to the equivalent puller?

[Thomas Nash]

I have a Tony Nijhuis 1997 plan of a Miles M33 Monitor rated for two O.S. 15's IC engines,wingspan of 56"and a flying weight 6.5lbs.
I want to build this model with a pair of brushless AXI 2820/10 electic motors, which Puffins say are equivalent to a 40CI eng.
My question is what percentage do I enlarge the plan to for a realisic flying speed for this WWII aircraft.
It was designed for target towing at over 300mph.
Any help would be greatly appreciated.

[John Sheehy]

I'm assembling a Multiplex Twinstar 2 and want to fit brushless motors.  I plan to have the ESC's in the motor mount's.  What I don't understand is the wiring.  Can I set up the power supply in parallel?  Can I use a Y lead from the ESC's to the receiver?

I hope someone can help as work has stopped until I find the answers to these questions.

Thanks,

John.

[Phil Claridge]

 hello john you can get motor mounts from muliplex which fit the pods  and brushless outrunners fit straight on . escs will tuck in behind the motors tidely i hold them in with short lengths of stirrer sticks i believe my wiring is paralel going to a 2200 mahr 3s lipo timbo could tell more about the wiring as mine was wired when i got it  regards phil

[John Sheehy]

Thanks Phil, are these motor mounts different from the ones supplied with the kit?

John.

[Tim Mackey]

John, please start another thread to discuss this model, thanks

[Tim Mackey]

I see you have already done so

[Martin Harris - Moderator]

Ianto,

 

I built one of these recently and went with the same high launch power/contra rotating motor thinking, removing the compensating sidethrust.

 

I used 2217 2200kV motors from Giant Cod on a 3S LiPo - loads of power on APC 6 x 4s which are readily available in both "hands".  Possibly too much power on reflection - see further on...

 

I departed from the plan by using 2 aileron servos and adding a rudder.  I mounted the ESCs in the scale radiator positions (eventually cutting right through the wings instead of the recesses in the picture below)

 

Launch was like an arrow from a bow - it flew superbly but on the second pass, one of the motor shafts sheared, probably due to an out of true prop adapter coupled with heavy nuts added to ensure a safe C of G - and once I'd confirmed the fact that the prop had left the model, ignoring that it had actually been flying quite happily on the one motor and that I had a perfectly good rudder available, I decided on an immediate precautionary landing, reduced throttle to zero (usually best practice on a model twin with a failed engine) flew round the circuit deadstick, hmmm getting a bit low for comfort let's add a little power fairly gently, WHAP the motor burst into life like a whirling banshee, instant spin, too low to react in time, CRUNCH!

 

Lesson to learn:

 Great advantage of going electric for twins is that you don't get dead sticks - WRONG - basic airmanship is ALWAYS expect the worst case - I was simply not thinking about the possibility of a motor failure and was in the wrong frame of mind. I knew what to do and what not to but didn't apply very much of it in the situation.

 

Anyway, on the small amount of evidence so far,  I'd say go for contra-rotating with ample power and you'll have an easy launch. Just don't get lulled into a false sense of security!

Edited By Martin Harris on 20/07/2009 00:20:36

[Paul Hyde]

Hi to all,

               Built a mossie from the free plan a few modifications retracts,split flaps dont think the real one had splits! I decided to go with two brushless bell motors two hi-model escs 25 amp each had plenty of power,3 blade 8x4 gws, 2150 rhino lipo.

               First flight found it was tail heavy and pranged itdone a few repairs added some lead in nose. Its second flight i decided to hand lauch flew very well had some height when disaster struck!!!!! we all saw the bell motor fly out of the nacelle and in turn an un controllable spin started i immediately shut off power 4ft from the deck i gained controll and belly flopped it on the grass the grub srews worked loose holding the motor in place, a few mods later i tried again flew really well until it span violently into the ground , i suspect one of the escs shut down due to heat i had no ventilation running through the fuzz.

                             I decided to persivere with it so back to the building board once rebuilt decided on a motor change went for two brc a2208-14t 1450kv (120w) brushless outrunners.

                     Had another test flight last sunday im pleased to say it went really well,got too much up elevator does a flick roll when applied too much will correct that for next flight ,gonna spray it soon

[Paul Hyde]

corrected the flick rolls with less elevator 3mm up/down was having a good flight when it went into a mad spin again !!!!!!!! shut off power straight away and managed to correct it and belly flopped it in the grass. slight damage to the nacelle repaired already with a bit of cyno........ i'll give it one more go before binning it i think, more trouble than its worth im in two minds!!!

[Paul Hyde]

Had another test flight this morning flew quite well untill we heard a loud screech from one of the motors shut power off straight away.

On landing it cartwheeled broke 1 nacelle off not sure if 1 motors getting too hot ! got to brand new hobby wing 25 amp  speed controllers in it yesterday im sure its not 1 of those shutting down have to take the motors apart and see. Any suggestions greatly appreciated...

[Tim Mackey]

I take it you have measurd the current flowing by using a wattmeter Paul?

If this is within the tolerence of the motors then they should not be overheating, and you problem lies elsewhere - possibly the timing is wrong for them on the ESCs, and one motor is complaining.

[Paul Hyde]

So how does one set the timing i do have a program card for the escs, i'm afraid i dont have a watt meter yet its on my to get list...

[Tim Mackey]

The programming card should include within its set of variables the option for setting the timing.

Most outrunners prefer hard timing, and low frequency ( pwm around 8khz or so) but you may need to experiment with both timing and  PWM settings ( if available ) as well as soft start etc to get the motors happy.

BUY A WATTMETER  

Edited By Timbo - Administrator on 01/02/2010 21:49:27

[sceadu498]

I am going to build the 38" span and I wanted to see if anyone thought if the E5-M-14 Brushless Outrunner Motor - 400 Size motors from Common Sense RC

would work on this plane?

http://www.commonsenserc.com/product_info.php?cPath=51&products_id=326

 

I am new to electric's and am still trying to figure motor sizing out.

 

Thanks in advance for your help.

Jim

Edited By Timbo - Administrator on 12/04/2010 22:21:05

[Tim Mackey]

I had to edit your post as the chart screwed up the page.

That should work, although I have to say that much cheaper units exist that would do the job - have you tried Hobby City - many US modellers use them, as we do here in the UK.

[sceadu498]

Sorry for the page formatting problem.

 

They had the motors on sale at a dicounted price over the weekend of $45 (US) for the two and free shipping. The more I think about it, I am not sure if they could run a 6 inch prop as it looks like that is about the biggest prop the plane can use.

 

What motors from Hobby City would you recommened?

 

Thanks,

Jim

[Tim Mackey]

Well they will "run" a 6" prop, but the power will be down. You may need a slightly higher Kv motor such as THIS

[sceadu498]

Another question for everyone. How do you mount the plastic spinners that Tony has available? Do you make a backplate and screw the spinners to them?

[Paul Hyde]

Thanks for the advice timbo sorry ive taken so long to get back been busy repairing as you do. I found out why my motor was shutting down there was some aluminium flecks of steel in the right hand motor,must have picked it up off the bench cleared that out. Any way i bought a program card set the esc's hard timing and soft start no problems so far,had another test flight sunday flew great no problems at all .

Sprayed it to after that dark green and duck egg blue. The duck egg blues not quite right but wot the hell it flies ... Oh i got a watt meter too (dont know what all them numbers are though LOL.) Cheers mate.

[Paul Hyde]

a bit of a handful. landings yesterday were on the heavy side came in a bit fast!

[Paul Hyde]

R.I.P Mossie my own fault forgot to put flaps up fighting me all the way