A dumb question
 

Friends,


Working on the adage that .......'the only dumb question is the one that was never asked' and being a recent convert to electric power,I seek an answer to a question to which I seem unable to find readily herein.[>:]

I am setting up a GWS E starter foam trainer as follows :

1. Stock Airframe, Stock supplied engine ..er ....motor, GWS T4 channel starter radio with tiny servos, ESC and receiver.

2.The GWS E Starter Manual suggests using a 7.2-8.4V Nicad or NiMh 'power pack'.

3. I want to convert it to LiPo power. I imagine a two cell 1200mah pack should work.

Questionsi : i. Will my proposed LiPo battery set up work or would you reccommend a three cell set up ?

ii. Can I use the same ESC or is there a special ESC for LiPo Batteries as opposed to Nicads/NiMh's ?
( Either ESC information appears to be an esotoric art form or I am dumb after all )

iii. Can I switch between NiMhs and Lipos ( while taking care of the CG) Cant think of a real reason why I would, but neverteless a dumb question.

iv. What equivalent 'Brushless' motor would you reccommend if I decide (or need) to hop up the above if the stock motor proves to be a weenie.


Any other thoughts/advice on the above are welcome. BTW I am an experienced RC pilot. ( 2000 + flights) on Gas powered planes.


Thanks for your help.

Rochild

RE: A dumb question
 

I can only answer a couple of your questions. If you switch to a LiPO for power, check your ESC specs to see if you need to adjust or set the LVC (low voltage cut off) for LiPo? You will possibly destroy a LiPo if you discharge it to low. You want the LiPo to cut off the motor when the voltage falls to about 3.3 volts/cell. Would a 3 cell LiPo be okay? Need to check the motor specs again and be sure that you do not exceed the ratings for it and check the current draw to make sure you do not exceed the specs on the ESC. You may be able to change the prop size to allow you to use the 3 cell LiPO without exceeding current or voltage specs. If you can, be sure to get yourself a wattmeter as it will become your best friend for helping to set up your electric powered planes. Accurate current and watt readings are almost a necessity for successful electric flight.

RE: A dumb question
 

I would first fly the plane STOCK. Then modify it. Then you will know what you do not like & want to change.

RE: A dumb question
 

You didn't mention which motor you have. The Estarter ships with a few motors.

The 300 runs nicely on a 2S battery. That's what I use now instead of my original 7C 1100 mAh nimhs.

The 400 motor runs well on a 3S battery with the D gearing (there's a letter on the black gear on the front of gearbox) and a 9 x 5 prop.

Because the battery pretty well sits on the CG, you won't have to worry much about switching packs. I didn't have to add weight to any part of the E Starter when switching between my 140ish gram nimhs to my 60 gram Lipos.

You can use the same ESC with either battery. What you don't want to do is drain your Lipo down past 3V per cell. You didn't say which ESC you have, but if it's programmable, you can reset the low voltage cutoff for each battery.

A better option is to time your flights and land before your lipo battery would be over-drained. Coming from the glow/gas world, you understand the concept of landing before the tank runs dry. :)

RE: A dumb question
 

One other thing:

Even with my heavy nimhs, I liked the way my 300 motor powered Estarter flew. (Like it even more with the lighter lipos.) Most would put it in the weenie class, but to me, it's a trainer and that's how I like to fly it. It would cruise at about half throttle.

Any brushless motor that puts out 150 watts on a 3S lipo and a 9 or 10 inch propellor would satisfy those who gave up their dream of being astronauts and took up RC instead. That gets you almost twice the stock power.

RE: A dumb question
 

GWS speed controls are as flexible as they are affordable:

http://www3.towerhobbies.com/cgi-bin...&I=LXKZY6&P=SM

This ESC300 Li speed controller will auto detect whether you're flying a LiPo or a NiCd/NiMH battery automatically. It works very well with the GWS EPS300 power system. If you get the E-Starter with the EPS400 power system, then simply add the matching ESC400 Li speed controller instead.

GWS stock power systems fly extremely well. I have a Slow Stick with the EPS300/ESC300 Li combo on it that I fly with 800Mah 2S LiPo batteries both inside and out. It's powerful enough to loop indoors, yet I can take the plane out to the flying field and catch thermals with it.

You could very well find out that you're happy enough with the stock power setup that brushless upgrades may no longer be of interest.

RE: A dumb question
 

Thank You ALL who gave your advice on my E strater dreams............All your comments make sense and I will stay with the stock 400/Gearbox combo.
I will check on the ESC which is NOT a GWS part and start off with a 3S LiPo and see how it goes.
Actually this is my 'come back' to RC after an abscence and Im trying to get my young nephews into RC flying.

Incidentally, my reference to 'weenie' performance from the brushed motor is from my first experience with electric flights back in ( gasp! ) the eighties, with 05 can motors and lead heavy 7-8S Nicads. I had scratch built a 5 oz British design called an "Electric Haze" and we just managed to crawl around the sky and plop down at the end of the Battery.
run. It was a nice looking plane.

But golly, looking at all these great stuff available today, I'm jumping back in to electric flght.
I might even re-visit my old Electric Haze.

Cheers you guys and look out for me out here asking all the 'dumb' questions OK.