Tony Cundy 2 Posted June 17, 2008 Share Posted June 17, 2008 I am new to electric flight and wonder why there are so many inconsistent units. We all talk of charge current and discharge current in Amps. We think of discharge times in minutes but it is not too difficult to think of 12 minutes as 0.2 hours. So we can see that a 2 AmpHour battery can discharge at 2 Amps for 1 hour or 4 Amps for 30 mins or 40 Amp for 3 mins, so long as Amps and hours multiplied together comes to 2 for our 2 Amp hour battery.Of course this is a nominal value and there is some inefficiency in the charge process so we might have to charge our 2 Ah battery at 2Amps for 70 minutes - of course the clever Li_Po charger will sort this out.With all this process worked out in Amps, it seems daft that battery suppliers complicate a simple world by giving their capacities in mAh - that is Miliamp hours. All this does is add an unwelcome layer of complication. Surely it would help us all if suppliers said 2Ah instead of 2000mAh.Car batteries and other batteries with discharge rates of several Amps always give capacity in Ah. Let's leave mAh to low power torch batteries that discharge at perhaps 50mA.This is one of many inconsistencies that makes life harder than it ought to be. How about dimensions in inches and wing loading in ounces per square foot. The inch to foot conversinn is enough trouble but where does this leave models weighed in pounds those who use the metric system? I could fill a book. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 17, 2008 Share Posted June 17, 2008 it's there to confuse us Alan ! Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 18, 2008 Share Posted June 18, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Alistair Taylor Posted June 19, 2008 Share Posted June 19, 2008 Probably best just to head down to the 2 hectare flying site, in your left hand drive car, at 50 KPH, in order to fly your 1.3m wingspan plane, with its 6.5 cubic centimetre motor, at a speed of 10 m/s, 50m above the ground.Probably best just to head down to the 7 acre flying site, in your right hand drive car, at 30mph, in order to fly your 45" wingspan plane, with it's .40 cubic inch engine, at a speed of 23 mph, 30 feet above the ground.Eric - I can't help feeling that you're getting confused between the round amp and round tuit.Round tuit's a very thin on the ground - as you will find if you ask a few modellers whether they've got a round tuit.Ali Quote Link to comment Share on other sites More sharing options...
Ed Kershaw Posted June 21, 2008 Share Posted June 21, 2008 Wait till you start trying to work out what all the motor numbers mean - like why is a 400 brushed motor equivalent (roughly - before anyone jumps down my neck) to a 2212/20 brushless? And what does that mean? And what is the difference between a 400 and 480 brushed? etc etc.In reality, it's a bit confusing at first, but you just get used it as you get going. Then it gets quite fun when you realise that people who have been pretending it's all very complicated and you need a PhD in physics to calculate what motor to put in your latest IC to EP conversion were either pulling a fast one or hadn't a clue themselves. Then, later on, when someone at you're club asks why they need a 20C pack and not a 12C and what size outrunner they need for their latest creation or something, you can answer them knowledgeably with an "I've been at this for years, laddie" look on your face. Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 21, 2008 Share Posted June 21, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted June 22, 2008 Share Posted June 22, 2008 Nobody has mentioned Coulombs,Joules,Ergs per cubic Henry,,bhp/HP(English or French). torque in Kg ins or LB mms, Flux density etc,etc,. Lets get really technical Eh ! Centigrade,Celcius/Fahrenheit convertions phew ! Easy Now the owner of my second 'lectric power train for a conversion from ic- I'm not going to let it all beat me & 'er indoors is kitting out the house with padded walls just in case my braincell cant cope !! ) & I get back to full-time proper measurements & methanol .Have even started a spares dept./box filling up with stuff that will be antiques in a week or two OR when the next magazine is published whichever is the sooner!Grumpy Myron PS Spot the deliberate mistakes you boffins out there whilst I work out what my next "must have " will be Thanks again oh great one in the orme (Timbo) for starting me off on this new deviation from proper aero-modelling .Must heat up my glue pot & get the wood out purely for therapeutic reasons Quote Link to comment Share on other sites More sharing options...
Ed Kershaw Posted June 22, 2008 Share Posted June 22, 2008 The point I was really trying to make (but failed miserably) is that there's nothing complicated about it at all.Just read the manufacturer's specs and you soon realise what it all means. The model motors website is great, as is innov8tivedesings.As RJ Mitchell said, "If someone ever tries to explain something to you and it sounds too complicated to understand, it's probably all balls". Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 22, 2008 Share Posted June 22, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 22, 2008 Share Posted June 22, 2008 Quote Link to comment Share on other sites More sharing options...
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