Lydd Model Flying Club. Kents Best.

The Lydd Model Flyers are a BMFA Registered Model Aero Club on the Romney Marsh, UK.
 
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 'lectrics

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grounded

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Number of posts : 813
Age : 62
Location : Greatstone
Registration date : 2008-02-15

PostSubject: 'lectrics   Mon 11 Mar 2013, 8:03 pm

OK i'm having a go at the dark art of electrics affraid Before I make a knob of myself one thursday evening in the future, will this work??

2000Kv 10gram motor running 7x5 prop at max 5.5 amps, through an 8 amp esc, powered by a 2S Lipo??

I think I've got the maths right but would welcome some ideas.

'plane would be the Jbug 22" wingspan(on you tube) made from 3mm depron. Radio 2.4 ghz Spectrum DX4 with lightweight 'orange' Rx.

Errrmmm???

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Worzey

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Location : Ashford
Registration date : 2008-02-09

PostSubject: Re: 'lectrics   Mon 11 Mar 2013, 9:22 pm

I think the 2000Kv bit is how many RPM the motor will do per/volt with no load on it. So, with a 7.4v battery (7.4 x 2000 = 14800RPM)
If you say that the motor will draw 5.5 amps at full power when turning a 7x5 prop, then your 8 amp ESC should be OK.
From this, you can conclude the battery capacity you will require for the amount of flying you want to do. Fit a 5500mah battery and you could fly for an hour at full throttle! Only problem being that your plane probably won't lift the battery! So, a 550mah battery will give you a tenth of the flight time (6 mins) of flat out flying. As your plane will have a throttle (I hope!?), you won't be flat out all the time, so a battery of around 400-500mah should be good for a 6-8 minute flight.


Last edited by Worzey on Mon 11 Mar 2013, 10:30 pm; edited 1 time in total
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rotorman

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Location : greatstone
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PostSubject: Re: 'lectrics   Mon 11 Mar 2013, 9:42 pm

I think your calculation may be a factor of 10 out,200x7.4v is 1480 rpm and for max efficiency you should aim for 80 per cent of this speed which is 296 revs less ie 1184 rpm. scratch
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rotorman

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PostSubject: Re: 'lectrics   Mon 11 Mar 2013, 10:05 pm

I've found this calculator that might help.
http://brantuas.com/ezcalc/dma1.asp
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rotorman

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PostSubject: Re: 'lectrics   Mon 11 Mar 2013, 10:28 pm

Apologies your calculations were right, I read Dave's figures wrong,should have worn my glasses.
Sorry.
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Rainman

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PostSubject: Re: 'lectrics   Mon 11 Mar 2013, 11:20 pm

Don't worry Adrian, your theory sounded far more plausible!! lol!
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grounded

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PostSubject: Re: 'lectrics   Tue 12 Mar 2013, 5:31 pm

Thanks everybody lol! At least I wasn't a million miles out. Bravo Better sharen my penknife n start cutting Deporn then!! lol! lol!

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Nobby
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PostSubject: Calcs debate????   Wed 13 Mar 2013, 11:27 am

Just give Carol Vorderman a buzz and she'll sort the calcs out lol! lol! lol!
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grounded

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PostSubject: Re: 'lectrics   Wed 13 Mar 2013, 8:18 pm

[quote="Nobby"]Just give Carol Vorderman a buzz and she'll sort the calcs out lol! lol! lol! [/quote

I only have to say Carol Vorderman to be hit with a torrent of verbal abuse then silence lol! Don't know why really lol! lol!


Anyway DX4 arrived today from BRC within 24 hrs of order Bravo Bargain at 27 kwid, even came with manual and batteries! Full range Tx 2.4gig DSM2/DSMX (whatever that means) really suprised 'cos although not top range, can still do elevon mixing I can now buy Rx for 10 kwid instead of Futaba at 54.

Gonna replace batteries with NiMH rechargables.

Just ordered 'lectric set up as previous post, so hopefully flying something next Thursday at Hobbs Parker

SE5 nearly finished too!!

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grounded

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PostSubject: Re: 'lectrics   Wed 27 Mar 2013, 2:25 pm

Well, I've always said that lack of time is the biggest problem pale But...Off sick at the moment with chest infection so, unable to do decorating or gardening, I've indulged in 2 days of plane making.
The little 3 channel 22" J bug foamy is ready to go now, just waiting for 'orange' receiver from Hobby King then I can set it all up and play with my new DX4 Very Happy came out at 101grm, 3grm heavier than guide weight pale Glides OK though 'free flight' so hoping the extra weight doesn't affect it too much.

The SE5 that is now over a year 'on the bench' is just having the radio installed, then needs painting finished before maiden, hopefully after Easter when it's a bit less cold out Bravo Looking forward to getting out flying again, seems like a long winter lol! lol!

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