25 glow to electric

[n3o]

I wanted to build a Martin Baker MB5 plane. The plans are scaled for .25 glow use. The plane's weight without engine is 1.9 lb .
The objectives are

1)Get the plane to fly and do some maneuvers, and get a good speed.
2) Have a flight time of around 7 mins +. ( for one battery; with few aerobatics, cutting off motor not included )
3)Long lasting motor at an affordable price. LiFe setups will be appreciated.
Lipo should be reliable.

Please recommend what will be the ideal setup for such requirements.(in a budget of $130 for a motor/esc and 1/2 batteries. charger and other bits are available)

regards,
n3o

P.S: please mention non-chinese brands, i have had really bad experience with them.

[kyleservicetech]

Originally Posted by n3o

I wanted to build a Martin Baker MB5 plane. The plans are scaled for .25 glow use. The plane's weight without engine is 1.9 lb .
The objectives are

1)Get the plane to fly and do some maneuvers, and get a good speed.
2) Have a flight time of around 7 mins +. ( for one battery; with few aerobatics, cutting off motor not included )
3)Long lasting motor at an affordable price. LiFe setups will be appreciated.
Lipo should be reliable.

Please recommend what will be the ideal setup for such requirements.(in a budget of $130 for a motor/esc and 1/2 batteries. charger and other bits are available)

regards,
n3o

P.S: please mention non-chinese brands, i have had really bad experience with them.

Unfortunately most all motors are now made in China. Even the smaller Hacker motors. That said, I've got eight Hackers, including two A50-12S motors. The first A50-12S motor was mfg in Germany, the second was Mfg in China. These two motors are identical in appearance, and performance.

As for your model, I've got a Electrify Edge 540T with a wingspan of 49.5 inches, area of 490 sq in, dry weight of 40 ounces without power system. The flying weight is 61 ounces.

The motor is a Hacker A40-12S, prop is a 13X6.5 APC-E, battery is a 4S1P (4 Series, 1 Parallel) A123 pack. This power setup turns that prop at about 7400 RPM, pulling about 450 watts or so. That is about 100 watts per pound, a fairly good figure. The model won't fly straight up out of sight, but has absolutely no problems doing loops from level flight and so on. The take off roll is about 20 feet on short grass. I've thought about adding one more cell to the A123 pack, but that might put to much stress on the airframe.

You might be able to get by with an A30 series Hacker, noteably less expensive than the A40 series. Check out one of those computer programs such as www.motocalc.com (Free for 30 days, then $39) for assistance on your setup.

If you go to LiPo batteries, you can cut perhaps 1/3 pound of weight out of your model, depending on which battery you select.

A123 cells are about 1/3 heavier, 1/3 larger in physical size than an equivalent LiPo. On the other hand, they don't seem to wear out, have absolutely zero fire hazard, and can be safely charged in 15 minutes.

I've got some 70 A123 cells in my various models, have yet to wear one out. (Three cells were damaged because of stupidity on my part though! ) Most of my 70 A123 cells are on their fourth flying season, with the same exact performance as when brand new. Some of them have over 300 flights on them. All of them were charged with a charger that charges the cells in about 18-20 minutes.

The LiPo cells have much lower risk of catastrophic failure now with the advent of the new balancing chargers such as the Cellpro line. Even so, most electric flyers are removing the LiPo battery from the model while charging them. That is not an issue with those A123's. They can be built into the model, and charged while inside the model.

[Big Johnny]

Denny, what type of charger are you using for your 123 cells. what would the equivilant to a 8s1p 5000 lipo. I think I might go this route with my 1/4 cub so I don't have to switch batteries all the time + I need nose weight, why not batteries instead of lead.

[kyleservicetech]

Originally Posted by Big Johnny

Denny, what type of charger are you using for your 123 cells. what would the equivilant to a 8s1p 5000 lipo. I think I might go this route with my 1/4 cub so I don't have to switch batteries all the time + I need nose weight, why not batteries instead of lead.

That would be a 10S2P A123 2300 Mah battery pack. At about 2.6 ounces per cell, that's 52 ounces. The charger used is a Cellpro Powerlab 8, with DC power to the charger provided by a 120 Ampere Hour deep cycle marine battery. Or even two of them in parallel.

Unfortunately, you need to set up those 10S2P batteries as 5S4P to charge them with the Cellpro charger. The '8 charger will recharge that 5S2P A123 pack in about 15 or 20 minutes.

You might have to build up your A123 pack your self to save quite a bit of $$$$. Voltman batteries has them at $9.99 each. And if you take reasonable care of them, those A123 batteries will last as long as your model airplane. They also can be stored at full charge, 1/2 charge, 10% charged, it doesn't really matter much.

One good place for those A123 cells.
http://www.voltmanbatteries.com/serv...1-dsh-A/Detail Be sure to order the free welded tabs on these cells. It's difficult to solder directly to the cells. I've ordered from voltmanbatteries, and other club members have also ordered from this USA based company, all have had good luck. Not true of 24 cells I ordered direct from China several years ago, they shipped 24 A123 cells absolutely loose inside a large plastic bag. No protection what so ever.

I've got wiring diagrams and so forth on how to do the 10S2P to 5S4P charging setup. Let me know if you're interested. As for shrink wrapping the cells after building them up, I've used those one or 1.5 liter water bottles available from the local grocery store. Cheap, and extremely strong. Just cut the top and bottom off the bottle, slip it over your battery pack, and hit it with a heat gun. I've used eight of those Anderson Power Pole connectors to configure the cells either as a 5S4P for charging, or 10S2P for flying. I've also got drawings on using this combination with Castle Creations 10 amp uBEC plus a two cell A123 battery pack for primary and backup battery power for your receiver and its servos.

If you've never soldered up a high power battery pack before, use a little caution. Any accidental shorts and the A123 pack will melt anything in its way. (Don't ask how I know) And, the A123 pack will win after being momentairly shorted, and you can keep using them. You will need a high quality soldering iron, not a soldering gun, preferably temperature regulated, and on the order of 100 watts (about $60 or so). I've got soldering iron recommendations also.

Let me know if you'd like more info and photos.