what size battery pack
 

First let me tell you that I have a 1/3 scale supercub that I built from scratch. It is powered by a 52 cc quadra. I have dual batteries and dual hd switches.The battery packs are nicad sanyo 800 mah 4.8 volts. this setup should give me 1600 mah for seven servos. The servos are. 1. standard for throttle. one 70oz servo for the elevator. one 70oz servo for the rudder. and four 100oz servos forthe flaps and areilons. am I right in thinking that a 70 oz servo will give about four and one half pounds of pull or push? and will the 1600 mah be enough to fly this plane in a scale way? the planes dry weight is 32 puonds. what do you think?

RE: what size battery pack
 

I forgot to mention that quadra is electronic ignition with 1200 mah battery

RE: what size battery pack
 

One 800mah battery is enough to fly that Cub, you just won't get as many flights compared to something with less load.

RE: what size battery pack
 

on an investment that big, i would go with two switchss for the receiver, with a 2500mah 6v pack to each switch , and the battery you have for you ignition is fine.

These batteries are great http://www.3epower.com/servlet/the-9...RC-NiMH/Detail

RE: what size battery pack
 

Thanks guys I want to stay with nicads because that is what my charger handles. I would like to know many mah. that these 7 servos would take in one ten minute scale flight. I was wondering if I had enough rx mah from this setup.

RE: what size battery pack
 

At full stall those servos may consume 2-3A of power each.

I just finished putting in a 6V 3000mAh pack for six digital servos on a small 25% ( 73" ) Yah 54.

I run a 2000mAh 4.8v ignition battery.

I had an 1800mAh battery for the servos and a 1200mAh 4.8v battery for the ignition, and I was NOT happy with the number of flights I could get safely out of those packs.

I fly 16-18 minutes minimum per flight, and 3-4 flights were enough to bring the latter packs down to the point I'd need to recharge them to fly safely again.


With the larger packs I can get a good 10+ flights in without re-charging the packs.

Dual 2500's as MetalicaJunkie suggests would be fine.

RE: what size battery pack
 

Also, you asked about how much force those servos will apply to the different surfaces. That depends on the length of the servo arm to where your connection point is. The servos are measured in Oz-in, which means if the length of the arm to the connection point from the center is 1 inch, then you will get 70 ounces at the connection. If it is 0.5 inches, you will get 140 ounces, if it is 2 inches, you will get 35 ounces. Remember that is only at the cable, or the pushrod, when you couple that to the arm on the surface itself, then the length of that arm will determine how much torque you will place on the surface. You now take the length of that horn and multiply it by the force to find out how much torque on the surface.
Curtis

RE: what size battery pack
 

Just consider that you have a lot of horsepower to "play with" so you can afford a few extra grams (not ounces.. pbecause the differences in batteries will most likely be grams, not ounces (plural) ) of weight. I would go with the largest battery pair that you can afford with the weight, regardless of the number of flights you can attain. The most important consideration is to supply the proper voltage and available current for the style AND duration of flight your aircraft will endure. If you have lots of power, an ounce difference between a lower capacity and a higher capacity will offer more benefits (duration and peace of mind) than drawbacks (weight).

CGr.

RE: what size battery pack
 

Thanks guys you have pretty much answered my questions especialy the one about servo ounce and lenght of push rod. thank all of you very much.