Discussion Electric Free Flight?

[skyline223]

How would you go about doing an electric free flight model? Not RC, but simply substituting an electric motor for rubber bands. Of course this has been done, but I simply want to know what setup you guys are using.

[kevin matthews]

I'd like to know the same thing.

Kev

[barry wilson]

I never did one but think I know how I might go about it. First I would measure the thrust the rubber setup was developing. Since weight is an issue I would go with a dc brushed motor and battery as you need nothing to change the dc to pulsating dc to drive the brushless motor.A brushless motor has to have a separate device.

Once required thrust was established start examining obsolite gws type motors or specialty suppliers of simular geared type motors. In most cases you want to turn a simlar size prop at about the same revolutions if the plane flew well under it's rubber set up. Or turn it faster with a much lesser pitch. So I would tach the original blade under rubber power to find the rpms.

.As you said hopefully someone who has actually done it may contribute to your thread.

[slipstick]

I think you'll have to be a bit more definite about what information you need and what type of models you're interested in.

I mainly make small indoor models from scratch and they just use a geared motor, a lipo battery and a timer. I make my own timers but you can buy them from various places. The motors and batteries mainly come from RC toys like Palm-Z/AeroAce planes and Picooz helis.

For bigger outdoor stuff the old GWS motors are a good place to start as Barry says. I'm not sure I'd bother with what the original rubber motor and props do, I'm more likely to look at what similar size RC models use and start there. But I'm only interested in sport flying. I guess if you were doing something competetive you'd want to get a lot more technical.

Steve

[skyline223]

Well the plane is a Guillows 20" Piper Super Cub. It honestly didnt fly very well under the rubber setup. I believe the plane is a bit too heavy for the rubber power - thats why I was asking about electric power.

[slipstick]

For something that size I think I'd try the motor and gearbox out of a Parkzone Ember with a single lipo cell 70-130mAh and timer. Apart from the timer you can buy the bits as Parkzone spares. The timer (and a wide choice of alternative motors) you can get from somewhere like BSD http://www.bsdmicrorc.com/ (look under Misc Electronics).

But it really depends on how heavy we're talking about. If you get too heavy for a given wing area you're never going to get anything to fly well regardless of the power source.

Steve

[scrubs]

Originally Posted by barry wilson

Once required thrust was established start examining obsolite gws type motors or specialty suppliers of simular geared type motors.

As you said hopefully someone who has actually done it may contribute to your thread.

I consider the small GWS LPS motors as anything but obsolete for FF. For RC you need a speed controller anyway but not so with FF. So if I can save those few grams I will. And this also means less cost for something that may go OOS.

I use the smallest LPS motors in 24-30" sport FF jobs. Here's a 27" Rambler with a N20 that I later converted to the 4:1 LPS, a 2 cell 250 lipo and a Rees timer.

bill

[skyline223]

Ive seen people try to fly it using the sukhoi/ember power setup here on RCG but they have all failed. I wonder if the power system out of one of those old air hogs electric free flights would work? Probably not...

http://www.amazon.com/Air-Hogs-Quick...7433377&sr=1-3

[scrubs]

For your 20" Guillows I'd use a Kenway N20 4:1 or a 7mm SS motor in a BSD gearbox.
bill

[skyline223]

Scrubs - something like this?

http://www3.towerhobbies.com/cgi-bin...?&I=LXHHJ9&P=7

[*jj]

You will need a special electronic timer, such as the one from Atomic Workshop, called the Zombie. This takes the current from the battery to the motor. There are other types of timer, such as that from K&P, which use an ECU and replace an RC receiver, which can replace a diesel for larger FF models. Some types of timer have a second channel to control a dethermaliser.

[scrubs]

Originally Posted by skyline223

Scrubs - something like this?

http://www3.towerhobbies.com/cgi-bin...?&I=LXHHJ9&P=7

Nope more like this (2nd one down, N20 motor):

http://www.kenwaymicroflight.com/motors_etc.htm

And a timer similar to this (pink one):

http://www.kenwaymicroflight.com/batterieschargers.htm

And a single cell lipo and charger. If you don't want the expense you could also use the 50 mah Nicads he sells (3). Then you charge after every flight and don't need a timer. I think there are still field chargers available that use D cell batteries for charging the Nicads for only a few bucks.

Down side of the Nicad setup is they are harder to find now and weigh more. Three nicads are about 11 gms in a pack, the lipo maybe 3-5 gms.

BSD micro will steer you right as will Kenway.
bill

[skyline223]

Thanks a ton scrubs. I will look into those

[skootertrash74]

jj had the best advice for ya, atomicworkshop.co.uk their systems are free flight specific setups

[Trisquire]

Does Hi-Line still make the little gear drives for two nicads? They just ran until the power was depleted. Don Srull did a few construction articles on Hi-Line powered planes in MA magazine.

Tom