View Full Version : Going brushless

09-04-2005, 05:23 PM
I have gone brushless on all my planes except one. I asked this question a few months back at RCU, and now can't find the thread. Here it is again......I have a Wattage Cessna 182 with a cobalt 400, 30 amp esc,7 cell 1300 Mah ni-cad, and a 7x4 ACP prop. I have no idea how many watts this thing is putting out. I would like to change it over to an AXI outrunner, maybe Li-po if the the amp range is ok with the batteries I have already, or just stay with the ni-cad. The plane OUW at this point is 32 oz. I do have a 6 cell 4200 11.1v Thunderpower brick laying around doing nothing, but it is for another project. It weighs 1.5 oz more than the stock battery. The problem I am having is the ground clearance of the prop. I maybe able to add one inch. I do not want to lengthen the gear or use larger wheels because it looks so scale like it is. People seem to really like the look of the 182 when it is in the air
(even more than my warbirds) If anyone could help that would be great. I am used to light weight foamies, and hand launching so the prop thing never played a roll for choosing a power system. I would like to stay under well under the 20 amp mark.....

Dr Kiwi
09-05-2005, 04:52 PM
For a 32+oz plane you almost certainly need an AXI 2808 (2212 etc would be too small). An AXI 2808-20 (80g) with an 8x4 APC E will get you ~28oz-30oz thrust at ~18A (200W) using your 3s2p TP 4200 [with a 2808-20 on 7-cells you'd have to fit a 10" prop!].

The 2808-16 with only 7-cells would need at least a 9" prop, and on 3s its amp draw even with an 8" prop would be waaay over 25A.

Cheers, Phil

Just had a thought - you probably don't need 180-200W (90-100W/lb) for a Cessna. To stay with a smaller prop (7-8") an AXI 2212/20 should work and if you got a smaller, lighter LiPoly pack (Tanic 1550?), at 10-12A the 2212-20 would get you close to 100W (50W/lb).

09-05-2005, 08:04 PM
Thanks Phil for the response. I am going to try one other route first. I installed a e-flite park 370 and MPI gearbox with a 1600 Mah 3 cell and a 7x5 prop. My watt-meter is showing 110 watts and only pulling around 13 amps. Putting the lighter motor and lighter battery in, put total weight at 25 oz. I tested the thrust on the ground and it has alot more pull power than the stock motor. I read on the net where someone put a Hacker and gearbox in a Wattage aerobatic plane and it did great. If this does not work I will go with what you suggested. Thank you for your time and thoughts..........GW

Dr Kiwi
09-06-2005, 02:37 AM
I can't tell you exactly what to expect from an AXI 2212/20 (I have the 2212/26 and 2212/34 but not the 2212/20) but that, with your 1600 3-cell would come in a fraction lighter than your E-flite and g/box and should run a 7-8" prop well.

09-09-2005, 03:53 PM
Try a smaller diameter GWS 3-bladed prop to get more tip clearance. Hobby Lobby also sells a 3-Blader, Graupner I think. I have an AXI 2212/20 that spins an 8x4.5 or 8x6 prop on a 3s lipo or larger probs on 2S lipo pack. I bought it because it is one of the few that is rated for 8" props on 3S packs. I need to run 8" props for ground clearance with various small scale models with scale landing gears.