Michaelj2k

OK guys, I've been around this RC patch for more years than I can remember. So......I've decided to take one of my IC birds and convert it to electric. The airplane is the Bill Northrop designed "Duster" (pic on right) from around 1964. Over the winter, I stripped the airplane down for recovering and refurb. I've decided to install an Axi 4120 motor and an associated speed control. I've not decided on batteries yet, but will probably go with NiMh for the first go around. The motor will be fully exposed on the firewall with a large ring cowl but my concern is cooling of the speed control and battery pack. I'll be opening up a hole in the firewall for the wires but will that be enough? What is the rule of thumb for cooling?

normgoyer

Hi, I have been running a 4120 in a large PT-19 for two years with great success. I have a 70 amp ESC and run 22.2 volts @ 3400 ma and the combo is bullet proof. Dump the idea of the niHi or nicads, go with A123 or Li-poly, Norm

Michaelj2k

Thanks Norm,

I've also considered A123's as well. But I'd like to know something about cooling airflows around the battery pack and speed control. Or should I forgedaboudit.

normgoyer

Hi, I live in the High Desert where it runs 100 to 106 in the summer and cooling is a non issue. I put the ESC in the cowling and my 123 cells in the fuselage permanently and if I am using LiPooly I cut a hatch in the firewall slide them 1/2 into the fuselage and remove them for charging. I have had zero heat issues and I have 3 large electrics with 123a and 2 with Lipolys. Forget al the negative aspects and go fly, the word is fun not frustration. Norm

82 years old today and going strong.

Michaelj2k

Thanks Norm, I just don't want to toast the stuff. [sm=thumbs_up.gif]

normgoyer

I love the A123 li-ion. I buy the 2300 ma ones from 22 bucks for 2 cells. I use an Astro Flight A123 specific charger. These cells don't burn, blow up or self destruct like LiPolys, and they can dump full power for short period making for shorter flights but much lighter packs. I fly a BH T-28 with a 1420 size off brand motor and power it with a 60 amp Esc and 5 2300 A123 cells and it flies just great and long enough to scare me several times, then I dump the flaps and land, to have fun simplify your hobby, worry less, fly more. Norm

tIANci

Go with lipos as later you can use them on planes that might want a light power supply but for bipes that are floaty, NiMH are fine.

My own rule of thumb for cooling is to run an ESC that is a class bigger than what you will need, e.g. if your system pulls 40-45A then go with a nice 60A ESC, if it pulls about 60A and you are flying a Tiger Moth then 60A ESC is fine as you will not be on WOT all the time. For your plane you can leave the ESC outside the plane, below the cowl area if you feel the tank compartment is tight.

As for batteries I do my best to push my lipos to only 80% of the constant discharge capability, e.g. system pulls 60A, I use about 80A-100A batts. My Sebart Angel pulls about 60A but I am using batts that are able to handle a constant 125A. Only when I am stiffed on weight that I will use batts that will be pushed to its limits. My Fun Jet pulls about 45A and my batts are good for 60A.

Based on what I do I am not too concerned about airflow through the plane.