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View Full Version : 84 in. Cessna 182 EP conversion


shauntot
10-21-2005, 12:13 PM
Fellow flyers..need your inputs on this please.

I'm planning to buy a built up 84 inch Cessna 182 from a fellow flier back here in the Philippines, it's currently running a .90 Thunder Tiger engine. Made of balsa and some fiberglass, AUW is around 13.5 lbs. (incl. the .90 engine, 7 servos, etc.)

Prob is, the engine is already slapped on and guy selling it doens't know how much the engine weighs. I'm planning to buy it to convert to EP which would be a nice project, I would like to request some details and help from you if possible.

What would be a nice power pack for this plane for it to do scale-flying? Some are suggesting around 400watts would do it, but I would like to get your opinion as well. If possible, what would be the cheapest motor from these- AXI, MEC, Hacker, etc? Or if there are any others available on the net, I would really appreciate your input.

I'm planning to run it on 12 or 14 cell NIMH 3300 GPs.

ESC recommendation would be great as well sirs.

And to wrap it all up, if you could also post how much the parts will run and where available online, that would be very much appreciated.

Here are some pics of the plane.

jonnyjetprop
10-21-2005, 02:28 PM
I think that you are thinking of a power system that is far, far too small for the plane.

At 13.5 pounds with a glow and assuming that you stay with Nimh batteries, you will be looking at least 2 lbs. more than this weight. Lets say 15 lbs. ou then want a power system that will put out a minimum of 1200 watts. That's 30 volts at 40 amps. In other words, you need 30 cells or a 9s lipo battery. Even if you go with a more expensive setup using lipo batteries, I think that you would be hard pressed to get much below the original weight of 13.5 lbs. Then you are looking at something closer to 1000 to 1100 watts. Your still looking at least a 6s lipo system pulling 50 amps.

The cost of a AXI 4130-16 is about $150, speed control is going to run about $120, and for a lipo battery figure about $250. This could be a little more or a little less depending on the manufactor. Figure $120 for a lipo charger also.

I hope this helps.

John

shauntot
10-21-2005, 04:29 PM
I think that you are thinking of a power system that is far, far too small for the plane.

At 13.5 pounds with a glow and assuming that you stay with Nimh batteries, you will be looking at least 2 lbs. more than this weight. Lets say 15 lbs. ou then want a power system that will put out a minimum of 1200 watts. That's 30 volts at 40 amps. In other words, you need 30 cells or a 9s lipo battery. Even if you go with a more expensive setup using lipo batteries, I think that you would be hard pressed to get much below the original weight of 13.5 lbs. Then you are looking at something closer to 1000 to 1100 watts. Your still looking at least a 6s lipo system pulling 50 amps.

The cost of a AXI 4130-16 is about $150, speed control is going to run about $120, and for a lipo battery figure about $250. This could be a little more or a little less depending on the manufactor. Figure $120 for a lipo charger also.

I hope this helps.

John


Hi Johnny, thanks for replying.

Whoa, I'm not quite sure, but do forgive me if I'm wrong, but isn't that a lot extra power? I mean, it's good to have lots of power, but if it won't be used, it might just go to waste (and the money for the big motor as well). I was only hoping to get the plane for scale-flying, that's it. It's just what I'm after, can't find any Cessna's of the same size for it's price. (Guy is selling to me for $180 built and covered (plane only). Additional $145 if I want to include the .90 engine, but that would be defeating my purpose of converting it to EP. He's only flown it twice on the glow engine, guy is selling it because he had to sell his SUV and has no way of transporting it to the field now.

The 13.5 lbs weight is with the Thunder Tiger .90 engine, I'm not quite sure how heavy that engine is though, so the plane is definitely less than 13.5lbs. I don't have experience in glow, maybe you have, you can probably have a rough estimate of how heavy a .90 engine is and subtract that from 13.5lbs.

Appreciate your response, thanks!

Shaun

Matt Kirsch
10-21-2005, 06:34 PM
Agreed. 400 Watts is enough to taxi on grass... Maybe enough to get it rolling on a smooth runway. Maybe even enough to get it going just fast enough to lift off, tip stall, and smash itself to pieces on the runway...

My personal recommendation for scale glow conversions is to shoot for 100 Watts per pound, especially if you're used to horsing the plane around with a glow engine. For a 13.5lb plane, that's 1350 Watts. With 14 cells, that would mean close to 100 Amps, which is totally ridiculous. Most motors in this power range are limited to around 50 Amps if you want them to last very long. Plus, super-high-current equipment is quite expensive.

It's NOT "extra" power. 400 Watts is enough perhaps to maintain level flight, but as I said, you need much more than that to get the plane off the ground. You want adequate power to get out of trouble when necessary. Also, even though you're not using all that power all the time, the advantage is that the power system is not being stressed to the maximum all the time either.

jonnyjetprop
10-21-2005, 10:38 PM
Tower Hobbies list an OS 91 at 24.3 oz. with muffler.

Hobby People lists the Magnum 91 at 25 oz. with muffler.

John

Nitro Blast
10-22-2005, 03:58 PM
On mine:

Phasor 45 with Castle 60amp controller. 4s2p Batteries. Running 14.8 volts at 8000mah I have plenty in this bird.

Loops rolls, inverted flight... yeah you know.. all that scale stuff too.

Upon closer inspection, I think your bird is a tad bit heavier and bigger than mine! Hmm.... nevermind!

http://img301.imageshack.us/img301/166/cessnaskylane2s7nw.jpg

shauntot
10-23-2005, 06:23 AM
Agreed. 400 Watts is enough to taxi on grass... Maybe enough to get it rolling on a smooth runway. Maybe even enough to get it going just fast enough to lift off, tip stall, and smash itself to pieces on the runway...

My personal recommendation for scale glow conversions is to shoot for 100 Watts per pound, especially if you're used to horsing the plane around with a glow engine. For a 13.5lb plane, that's 1350 Watts. With 14 cells, that would mean close to 100 Amps, which is totally ridiculous. Most motors in this power range are limited to around 50 Amps if you want them to last very long. Plus, super-high-current equipment is quite expensive.

It's NOT "extra" power. 400 Watts is enough perhaps to maintain level flight, but as I said, you need much more than that to get the plane off the ground. You want adequate power to get out of trouble when necessary. Also, even though you're not using all that power all the time, the advantage is that the power system is not being stressed to the maximum all the time either.
Hi Matt, thanks for the insight. Sounds right, it won't be good to just have enough power,better to have extra to avoid taxing the power system.

1000 watts would be great, sorry if I'm a bother, but could I bother you for some motor and esc combo recommendations that would give that power output? And about the NIMH batts - how many 3000mah cells would suffice? Thanks again

Shaun

jonnyjetprop
10-23-2005, 01:43 PM
With a power system running at 40 amps,

20 cells = 800 watts
30 cells = 1200 watts

With apower system running at 50 amps,

20 cells = 1000 watts
30 cells = 1500 watts

Battery weight

20 cells:

3300 mah nimh 40 oz.

3700 mah nimh 46 oz.

30 cells:

3300 mah nimh 60 oz.

3700 mah nihm 69 oz.

ESC:

20 cell Castle Creations Phoenix 80,
30 cell Castle 45HV, 85HV, Jeti 77o, Jeti 90 (these can work at 20 cells also)

Motors:

AXI 4130-16 on 20 cells, AXI 5320-28 on 30-32 cells, AXI 5330-18 on 30-32 cells

Astroflight 40G brushless on 20 cells

Hacker C50 series -10L on 20 cells, XL on 30 cells

Kontronic has motors in that range

Neu Motors


John

shauntot
10-24-2005, 03:52 PM
Hi John,

Thanks for the various recommendations. As per your chart, I'm planning to run it on 20 cells, on 50 amps. Which then brings me to 20 cells of 3300mah and AXI 4130-16 on the Jeti 77 ESC.

Got this from the hobbylobby site:

"AXI 4130 Series External Rotor Brushless Motors
Very high torque motors capable of spinning very large props in sport aerobatic models of 10-12 lbs. and sailplanes up to 16 lbs. "

Cells Prop RPM Current Watts
-------------------------------
20 14x10 7140 39A 685w
24 14x10 8030 49.1A 975w

Is 685 watts on 20 cells good enough or do I need the 975 watts on 24 cells?

Thanks again
Shaun

jonnyjetprop
10-24-2005, 09:27 PM
Take this with a grain of salt since I've been all lipo for a couple of years, but I'd go with the 24 cell pack as I'm sure at that current draw, you'll see some voltage depression. I'd personally look into the 3700 mah cells if you can get them.

John

shauntot
10-25-2005, 04:29 AM
Yup, 3700 mahs can be had. 10 cells/2 packs = 20 cells?

Jollyroger
10-28-2005, 08:44 PM
Intelligent Batteries has a 3800mah that's less expensive and produces even more power. Check out Cheap Battery Packs website.http://www.unipros.com/battpacks/main.asp?session_id=19127

shauntot
10-29-2005, 07:18 AM
thanks for the tip jollyroger, it's ok, batteries back here in the phils are pretty reasonable, a 6pc 3000mah costs only $25..add about $2 for every cell u want to add :)

shauntot
11-08-2005, 12:49 PM
Hey johnnyjet,

I went ahead and took it a bit further to be safe, got myself an Axi 5320/28 which (on paper) will push out 1498watts on 10s lipos or 30cells nimh.

CellCount Prop RPM Current Watts

10S LiPo 18x12 6160 61.9A 1494

Now for the esc. You think the Jeti Advance PLUS 77 Amp Opto be enough for this motor? Or should I get a Castle Phoenix 85a High voltage?

Should I also be looking at a UBEC?

Thanks in advance,
Shaun

jonnyjetprop
11-09-2005, 05:04 PM
I'd go with the Castle esc and I use a seperate receiver pack in my planes.

John

shauntot
11-10-2005, 07:52 AM
Cool, thanks John