mickey-gem

After much debate, I ended up ordering an AXI 4120/14 Jeti 70 Esc. UBEC
12x8 prop. I also ordered two kokam 3 cell 11.1v 3200 packs that I plan to wire
in series. I realize this is the upper limit for cells/volts for this motor.

The model motors web site gives one spec of an 18 cell 2400 pack drawing
48 amps with a 12x8 prop yielding 722 watts to the prop. This plane has an AUW
of 8.5 lbs for the glow version.

So I am excited to get all the components installed over the weekend! It took
me about an hour to give my cub a thorough cleaning, taking off the wheels and landing
struts to get all the glow slime off it, now she is clean and ready to be electrified!

Mellemel

Hi Mickey-gem, I just cleaned up my Kyosho Stearman, what a gooey mess it was. Hey let me know how she flies with the set up you are using. I also just received my AXI 4120/14 with Jeti controller. I am just playing with motocalc to get the best setup. Have not bought the Lipos yet some people say avoid the 5S packs and just go with 4S2P packs, motocalc seems to suggest so too.
Good luck.
Mel.

mickey-gem

Wow, really, just 4s huh? Well I also have 4 kokam 2s 2000 ah packs and two kokam 3s 2000 ah packs, so
I can experiment with them in different configurations.
I think you are right the 3s 3200's in series (6s, 22.2volt) pack may be overkill for powering this plane.
I had a Saito 82 in it that I rarely flew over 1/4 throttle. The plane floats with very little power. I will post my experiences.


Thanks!

Mellemel

Yeah, please let me know how it goes. It'll be a month or two I think before I get the Stearman ready. Have you seen this video of an Axi conversion Cub, there's one at this link.

http://www.hobby-lobby.com/j3cub.htm

Have you downloaded the Motocalc program ? it's free for a month, Just try typing in the minimum info it asks for in purple and it's quite fun once you get the hang of it, if you have trouble let me know I can give you the Axi numbers you need although they 'll be on the leaflet that came with the motor, if you still have them.

Mel.

Mellemel

You mention you got an AXI motor and jeti 70 , is the Jeti the NON programmable type ? Mine is and I asked Hobby Lobby what the Low Voltage cut off is set at on this auto function, they tell me it's 2.56V There's a sticker on which says Lithium support, Possibly it's OK but all my other ESC's (Non Jeti) are set at 3v cut off for Lipo's.
I'm concerned that 2.5 v is too low ! I'd better land before LV cut in !!
Have you used this Jeti 70 before with Lipo's ? if you did are your Lipo's OK ?
Thanks.
Mel.

mickey-gem

The Jeti controller I have is the programmable type, the opto plus version. I also have a 40 amp jeti opto plus that I have
in my World Models Fun EP 3D with an AXI 2826/10, running 2 kokam 2s 2000 mah pack wired in series for 4s. The 40 amp is
also programable with the very small program card available through Hobby Lobby-very easy set up compared to my two castle
Creations 25 ESC's

I learned on my second flight with the Fun world that the cutoff for the ESC did not give me much advance warning that I was
running out of power. I went ahead and brought the plane in for a landing, because I had been flying so long, probably about 13 or
14 minutes. I brought the plane in for a long aproach, landed the plane, as I was taxiing the plane back from the far end of the field
it completely lost all throttle affect halfway between me and the end of the field. Had I not brought it in myself when I did I would
have had to make an emergency landing.

You mentioned doing some static tests on your system with a whattmeter? Maybe you could experiment with running 3/4 to full throttle
with your setup and get a good time frame of when the pack voltage approaches the 3.0v per cell mark, then maybe factor in a 1minute
or 5% fudge factor, for safety sake. You definately do not want to risk going below the recommended voltage, Lipo's are pretty unforgiving
in that area. I ruined alipo pack doing that before.

Longarm

My Feedback: (1)

That Cub on the Hobby Lobby page is not a real nice flyer. It looks very nice, but it flys very roughly.

I had a 4120/14 in that one with a 3s2p pack in it. I tried a 13x8 and a 14x10 APCe props and both flew the plane with plenty of power. I would probably use the 14x10 over the 13x8 if I still had that plane. I have been thinking about getting another one with around the 80in wing size. I was thinking about getting the Hangar 9 version, or getting a Sig Kadet Sr. and try that out.

Take Care.....

Longarm

Darrell B.

Longarm,

A friend of mine has the Hanger 9 Cub, glow powered unfortunately, but it still flies very nicely. It is as stable as a cub gets in the 80 inch category. Of corse the larger cubs fly even better.

Darrell B.

mickey-gem

I tried out the AXI 4120/14 today on 4s 2pack of Kokam 2000 mah lipos (two 2s 2000mah in series)
15 c discharge rate with an APC 12x8 E prop. It did not seem to have as much power as I thought it
would on 5s. I have two 3s 3200 mah packs that I will try in series (for 6s) also they have a 20c discharge
rate. we'll see!

Darrell B.

You need a larger prop!! I have a Vermont Bell 1300 that I run an AXI 2820/10 in and I am trrning the APC 12x8 E-prop on it using a 3s3p of the older Kokam 1500s and it flys quite well. I know that in a thread about converting the Hanger 9 60 size P-51 they are using a 15x10 and 16x10 E-prop with great satisfaction.

mickey-gem

I tried the 5s kokam 2000 15C and only got about 7500 rpm with a 12x8 APC E prop.
I tried the 6S Kokam 3200 20C and got 10,500 RPM on both the 12x8 and 13x8 APC props,
much more thrust with the 13x8. I have a 14x7 I may try also.

Thanks!

mickey-gem

The Piper Cub flew very well on the AXI 4120/14 Jeti 70 ESC, Kokam 6s 1p (wired in series) 3200 20 C.

Takeoff was performed at just under 3/4 throttle, scale cruising speed was achieved at 1/4 to 1/2 throttle.

I was in the air for about 8 minutes, but I only used about half of the packs capacity. I put 1500 mah back into

the pack when I recharged them. So I probably had at least 3 more minutes of flight time left, I am very pleased

with this setup! I used a 13x8 APC Thin E prop. I did notice some prop "slippage" when transitioning to more throttle

rapidly, the prop seemed to "churn" . Would this be correctable with a higher pitch prop?

airflow

My Feedback: (1)

I found a nice deal at a fun fly and now have a Great Planes 81" Fabric Covered J-3 NIB. Hoping to assemble it to be electric, I naturally turned to RC Universe to see the haps. mickey-gem seems to have hit it off pretty nice in March, with AXI 4120/14 and Jeti-70 and Kokam 6s. These would be my choices, and I'm wanting some input and reports to confirm the setup.

mickey-gem

To confirm, the 4120/14 is better on 5s and 6s. The 4120/14 is plenty of power for the Cub, this plane is originally intended for a .46 size glow engine, so it needs very little motivation to keep it in the air. The 4120/18 is also a good choice, you can prop it a little bigger and pull less amps on 6S.

Regards.