ic vs electric

[Glasshopper]

As a potential revivalist I am tempted to start again with electric flight. I cannot however visualise the kind of kit that I would need on the flight line for say two hours flying in a day.At one club I saw the only electric flyer with his own portable generator to charge batteries. Is a generator essential? if not how many battery packs would I need to take for say a 40 size trainer and how are they recharged at the field? Would I connect a dc charger to my car and if so would this drain the car battery? The carpark is some distance from the flight line so do I trip back and forth with one battery or what? Tell me please how the electric experts manage their logistics

[Fats Flyer]

Hello Raymond,
i take a spare car battery with me and a field charger to charge them with.i normally take a couple of battery packs per plane with me,charging a pack while flying with the other.Also i don't fly all the time when i'm there, let the battery packs rest and cool off a while .Also it's nice to sit and watch others with a cup of tea.

vince

[Glasshopper]

Thks the tea will recharge anyone's batteries

[Mike Rolls]

I used to take a leisure batery and a field charger - but the batteryw killing by back. Now I just take enough battery packs with me. Rare for me to have more than half a dozen flights a session (we yak a lot!) so it is an easy answer.
Mike

[David Ashby - Moderator]

When you think that most li-po's will take an hour to recharge at 1c then many flyers seem to taske several packs to last a session. Sometimes Ni-cd's can be charged quicker at 2-3c so you'll see a leisure battery on call.

[Antony Wright]

Thats helpful to know - although Im training with ic at the moment I have given a lot of thought to using electric and wondered how it might work out. Thanks

[penty]

I have an ESC and brushless outrunner which I bought at a model air show.The ESC is a Tower Pro BMC 15A which lists a max 20A current.
On Lipos 2-5 cells.The motor I have is a 2408-21.I was sold an 8x4 prop.I want to fit all this to an Rip Max "Easy Street" which originally lists a requirement of a 600 motor with7-8 cell 3000mAh Ni-MH. i am now getting conflicting opinions as to the suitability of the motor.Which Li-Po set up should I try?
Maybe this set up isn't suitable for the model?

[David Ashby - Moderator]

Simon, I'm not sure the motor is big enough. I usually start with an watts meter to measure the current draw and then go from there. If you can work out the current draw then you can work out the watts per lb. 100watts per lb min.
If I were you I'd ring an e-flight specialist like Puffin models or BRC hobbies and have a chat to see what they think.

[nasa_steve]

hi simon
i have to back david on this you will be very lucky to get your easystreet to fly on a 120watt motor you will either cook the motor, the esc or both. you need at least a 600 class brushless to fly the easystreet with reasonable results
the motor you have is only suitable for a very lightweight shockie or indoor model
regards
nasa

[penty]

Thanks guys.To get an immediate response like that is great, on my first go at this forum.
I did mail John at Puffin, Who was very helpful.He said nothing less than 240 watts with a GOOD motor.Is the motor I have equivalent to a 400 sized brushed motor?I appreciate what you are saying about putting a meter on the motor, but I don't have any batteries.They seem quite expensive so I didn't want to make the wrong choice.Electric is no cheap alternative to i.c. and seems to work out about the same.
I suppose after years of knowing where I was with i.c. set ups, I feel quite at sea when it comes to electric.Is there any reading matter on the subject?

[David Ashby - Moderator]

Simon, yes, your motor is 400 equiv when you rally need 600 equiv.

You're right, electric flight isn't initially cheap although you don't have to buy glow fuel in the long run.
I usually suggest folks start with one of the tried and tested designs like the twinstar which can accept a variety of battery sizes. Then move on from there.

Reading matter, well you've got the mag and the intenet forums of course. There are some books too if you have a look around.

[nasa_steve]

simon
the motor you have is indeed a very small 400 motor more 280-300 as i've said before it really is only suited to ultra light weight flying more indoor than outdoor really. something made of depron or very light balsa somewhere no more than 30" would be around the mark. shock flyers would certainly suit this motor because that is what this size motor was intended for
regards
steve

[penty]

I think I'll bide my time until I can read more and have the money for a decent electric package from Puffin.
Whilst there is a lot of electric content in the mag. has there ever been a Newbies guide to electic? If there has I seem to have missed it.I loved the Nuremburg piece and was quite taken by the Multiplex Twister EDF.
I read one of the other threads, i.c v. electric and David Smith seems to have stirred up quite a furore on the topic.Each to their own. For now I think I'll become the Jeremy Clarkson of our patch, extolling the virtues of sheer petrol grease, grunt, noise and smoke!

[nasa_steve]

hi ya simon
puffin are'nt the only electric suppliers out there and there are plenty of reasonably priced motor esc combo's out there. david is an advocate of smelly power and won't be swayed by anything electric. i just love the conveinience of turning up at the field with nothing more than a couple of batteries a model and tranny and have a good morning flying. its also great for that last minute evening flight
regards
nasa

[penty]

thanks Steve,
I appreciate what you're saying about Puffin. I did mail 4 or 5 companies regarding motor setups, independently of this forum and I was delighted with the response from all of them.The mail I got from John at Puffin just seemed to hit the spot, for me.
Well, yes the electric ethos is a certainly a good one.I'm just struggling to get to grips with the technology,jargon and fear of the unknown! I'm sure it'll come with time, after all it's not Rocket Science........or is it!

[penty]

Good point about the smoke David!
As a matter of interest, is there ever enough light in Finland at winter time,to fly- or do you wait until the longer summer days and fly twice as much?

[Matt Watts]

Can someone give me the equation for flight times? Also one for charging my 1050mah Li-Po would help, because I'm the proud owner of a simplex-in-waiting.
Sorry to hijack the post!

[penty]

Good name for the subject Matt!
i'm afraid I'm still in the learning process myself.I did see quite a thorough explanation on one of the other threads. Have a search around the site.
Good luck.

[Dead-stick]

Matt, to calculate your flight time use the following equation: Divide the capacity of your battery, by total amps consumed at full throttle, multiplied by 60 and that equals your flight time (at max throttle).
For Example: 1.4mAh divided by 24Amps multiplied by 60 equals 3.49 Mins.
With good throttle management that time can be significantly increased of course.
As for charging your Lipo battery, I assume you have a Lipo dedicated charger, as a traditional Nicad/NiMH unit will not be suitable. The charging rate is normally at '1C' and is this is usually printed on the label of the battery. This means that the battery you are quoting should be charged at a maximum rate of 1050mAh. You can of course charge at a lower rate and while this is good for the battery's life-span, it does mean it will take a lot longer to charge up. Also, don't forget that you will need to choose the correct voltage for your Lipo. I assume your battery is a 3s1p pack, so that will need 11.1 Volts.
Hope this helps, and good luck with the Simplex!

[Matt Watts]

THANK YOU SO MUCH!!! (oh brilliant I'm hyper now) I'm aware of the 1C charge rate, but for how long should I charge it for?

[nasa_steve]

hi matt
your charger which must be li-po capable (under no circumstances of course charge on any other setting) will charge the cells for how ever long they need and should stop charging once completed
regards
nasa

[Matt Watts]

Good point. Even my £15 DC only charger's got that (I've only just realised!)
Cheers

[Andy Gates]

Simon

Have a look at J Perkins E-Pro motors & speed controls.
Your 15A ESC will not be enough (15A x 11.1v (3s lipo) = 167W

Have a look at their C35 motors with a 30A ESC. Pretty good combinations for £60 - 70

[penty]

Thanks Andy, will do as I havn't furthered my electric side of things. I may have a look at Wings and Wheels this weekend.

[Toni Ertl]

Quick related question - for brushless motors is it necessary to have cells that can handle extreme discharge currents (like LiPo)?

I'm considering returning to flying and would rather go electric for convenience sake, but already have various NiMH packs here from other projects. Brushless motors *appear* to not require gearboxes etc and offer better efficiency from the little reading I've done this evening.