HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 30, 2011, 02:07 PM
Registered User
United States, WI, Merrill
Joined Jun 2011
1,432 Posts
2 motor dilemma

Hi Guys
I think I can make the Infinite A3025-770kv motor work in my clean build fuselage Sig Kadet Mark II, but I recently took a chance on A Turnigy L3020B 600 motor as well.
I am still not electric smart at all I guess, but can any of you tell me which would be better for my expected 5 pound AUW build Kadet?

Here are some specs of each:
Turnigy L3020B-600 Brushless Motor (800w)

Specifications: Dimension : 37mm x 38mm
Weight: 146g (174g with all fittings, connectors prop driver)
Kv : 600rpm V
Voltage: 14.8v (4s)
Max Power: 800w
Max Current : 54A
No load Current: 0.6A
Diameter of shaft : 5mm
Thrust: 1520g
ESC : 80A
Dimension: 37mm x 38mm
Weight: 146g (174g with all fittings, connectors prop driver)
Kv: 600rpm V
Voltage: 14.8v (4s)
Max Power: 800w
Max Current: 54A
No load Current: 0.6A
Diameter of shaft: 5mm
Thrust: 1520g
ESC: 80A






MT-00120/Infinite A3025-770 Brushless motor (500W)

Stator Diameter 30.0 mm (1.181 in)
Stator Thickness 25.0 mm (0.984 in)
No. of Magnet Poles 14
Motor Wind 12 Turn Delta
Motor Kv 770 RPM / Volt
No-Load Current (Io) 1.8 Amps @ 10 volts
Motor Resistance (Rm) 0.033 Ohms
Max Continuous Current 40 Amps
Max Continuous Power 500 Watts
Net Weight 181.4 Grams
Outside Diameter 37.2 mm (1.465 in)
Shaft Diameter 5 mm (0.197 in)
Max Lipo Cell 3-5s
Connector Type 3.5mm
Recommended ESC 70A-SBEC
Recommended Prop Size 10x5-14x7


Thanks again for any insight you can provide.

John
jgestner is offline Find More Posts by jgestner
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 30, 2011, 02:47 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,222 Posts
The specs on the Turnigy motor are either a startling new breakthrough in brushless motor technology and power, a blatant lie, or a moment of incredible stupidity in the advertising department.

A 147 gram motor advertised as capable of 800W of power puts it at 5.55 Watts per gram of motor weight and that is about double what the realistic expectations (3 Watts per gram) would be for typical quality motors.

The Infinite A3025-770 motor, at 181 grams and 500 Watts works out to 2.76 Watts per gram and that is a believable number. The other specifications for the A3025 all seem about right and are believable enough. So I would expect to get that kind of performance out of the motor.

So I'd probably buy the A3025 just to punish HK. And if I needed or wanted an honest 800 Watts of power I would look at other motors in the Infinite line. That 3 Watts per gram rule is a telling indicator for these kinds or motors.

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Old Jun 30, 2011, 05:04 PM
Registered User
scirocco's Avatar
Australia, ACT, Kambah
Joined Feb 2001
3,283 Posts
Both can work, but which is "better" depends so much (actually almost entirely) on the prop and number of cells you use.

I understand you've already got both motors.

Tell us:

a) what diameter prop you are prepared to fit, allowing at least an inch clearance with the model on its wheels. Don't need pitch or type of prop, just diameter.

b) tell us whether you are locked into 3S, 4S or whatever for your battery packs.

Then we can give you a comparative assessment.

But DON'T but another motor on spec just because it has a so-called power rating or it is cheap. Start with the prop, it's all about the prop.
scirocco is offline Find More Posts by scirocco
Reply With Quote
Old Jun 30, 2011, 06:37 PM
Registered User
United States, WI, Merrill
Joined Jun 2011
1,432 Posts
Hi all I have a 5000 MAh 4S ordered and
1 x APC Thin Electric 13 x 6.5 $4.89
1x #APC12x6-E/5441 APC style propeller 12x6-E = $1.30
1x #APC13x4-E/6386 APC style propeller 13x4-E = $1.50
1x #TGS12x8E/7961 TGS Sport 12x8E Precision propeller = $2.77
If I have to go to 5 or 6S battery to make those props and motors work I can do that or I can use a different propeller probably up to 14 inch if needed.

What say you?

John
jgestner is offline Find More Posts by jgestner
Last edited by jgestner; Jun 30, 2011 at 08:59 PM.
Reply With Quote
Old Jun 30, 2011, 11:05 PM
Registered User
Canada
Joined Nov 2000
7,265 Posts
Frankly I'd suggest saving the SIG for 'nother day.
The Kadets (at least mine) was smooth flying but also a slow cumbersome thing. Sporty wasn't an apt descriptor.
Rather than spending a small fortune in accumulating all the large size & pricey bits required to get that Balsa Log airborne again. You might consider going to the Scratchbuilt Foamies Forum area and reading a bit of the stuff in there. IMO for $30/40 you could have a fresh DIY model equipped and flying in a couple of evenings work. Granted it would be half or less the size of the Sig but then you may not have to transport your model to a dedicated field.. just.. to enjoy it. Moving away from fuel usually means rethinking one's Entire approach to flying models and clearly one aspect of this is Model Size.
Food for thought ??
Bare is offline Find More Posts by Bare
Reply With Quote
Old Jul 01, 2011, 09:04 AM
Registered User
scirocco's Avatar
Australia, ACT, Kambah
Joined Feb 2001
3,283 Posts
On 4S, I don't think 6 or 6.5" pitch is enough for the 600 Kv motor, and 13" props on 4S are pushing the 770Kv motor overly hard IMO

The 12x6 might work OK with the 770Kv, but you're likely up around 450W - that's as much as I would want to push through a motor that size. 13x6.5 I reckon is too much prop for a motor that size and Kv on 4S.

12x8 on the 600 Kv motor should be roughly 380-400W, with ample thrust to weight for 5lbs (nearly 1:1 static) and a good pitch speed - a reasonably efficient setup that should make 70-80W/lb work really well.

Those are pretty rough estimates because I don't have constants for either motor (and they'd be pretty optimistic anyway). I still think your motors are on the small side both for handling the 4-500W that is IMO a reasonable target and for balance, but you might as well try them. But I honestly wouldn't put a 13" prop on 4S anywhere near them - and you shouldn't need to.

I disagree with Bare that it would be a log. 5lbs is not a lot of weight for over 700 sq in, and with the nice mix of thrust and pitch speed you could get with either solution, you'll be doing reduced power takeoffs and pulling straight up into a half loop or big wingover - That's what my 4.5 lb Kadet does on about 400W (6S 410Kv 12x8). On 480W (6S 410Kv 12 x10), I just pull straight up after takeoff for about 5 seconds. I've settled on the 12x10 - the pitch speed might seem a little high at around 77mph, but it works really well at part throttle and does respectable low passes (for a trainer). Yep, it's roll rate is not all that snappy, but heaps good enough for learning coordinated slow rolls.
scirocco is offline Find More Posts by scirocco
Reply With Quote
Old Jul 01, 2011, 09:47 AM
Speed cost money.
highflier's Avatar
United States, FL, Marathon
Joined Dec 2002
3,045 Posts
If you liked the Kadet as a nitro you will love it as a electric. Maybe it is a log, But they are damn nice flying logs. Not every plane should be a speedster or sport plane. Yeah you should have one of each, But sometimes you just want a relaxing flight. I still like the higher voltage setups so maybe you should look for a motor that is a tad larger and has something closer to 500KV. When you put floats are her and have the 13" prop you will be in awe with just how well she can get off the ground.

Also keep in mind that it is ok to slighter go over the spec on WOT. A short 30 second climb out will not kill the motor and once you are up you will be throttling back to 1/2 throttle. which will be way within the spec and allow the motor to run cooler.

Highflier
highflier is offline Find More Posts by highflier
Reply With Quote
Old Jul 01, 2011, 09:49 AM
Speed cost money.
highflier's Avatar
United States, FL, Marathon
Joined Dec 2002
3,045 Posts
How much weight do you need up front. I have used this motor in a similar plane and like it. This surely would yank your kadet around the sky
http://www.hobbyking.com/hobbyking/s...idProduct=5388

Highflier
highflier is offline Find More Posts by highflier
Reply With Quote
Old Jul 01, 2011, 07:01 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,222 Posts
That KDA motor, at 289 grams/10 oz. was just the kind of weight I needed to get a SIG Rascal 40 balanced out right. That was in a clipped nose plane with firewall mount, and the battery in the old fuel tank location.

The SIG classics are wonderful fliers! I don't care what kind of cheap thrills you get out of newer and lighter and faster and whatever, they are a pure joy to fly. Especially if you like to fly with coordinated controls. Sometimes the yank and bank crowd just doesn't get it.

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Old Jul 01, 2011, 07:12 PM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by jackerbes View Post
The Infinite A3025-770 motor, at 181 grams and 500 Watts works out to 2.76 Watts per gram and that is a believable number. The other specifications for the A3025 all seem about right and are believable enough. So I would expect to get that kind of performance out of the motor.

So I'd probably buy the A3025 just to punish HK. And if I needed or wanted an honest 800 Watts of power I would look at other motors in the Infinite line. That 3 Watts per gram rule is a telling indicator for these kinds or motors.

Jack
Hi Jack,
I had several of the Infinite A3025-770 kv (182g) and did a static thrust test with APC 14x7 prop and 4s-4000 30C lipo. Result is attached. Rated at 500w is VERY conservative. I pushed it to 820w in 3D flying with no problem. For trainer or scaling flying, 600-650w is pretty safe. APC 13 x 6.5 will get the motor around 600-650w depending on battery rating.
The rating on that Turnigy is very funny.

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Jul 01, 2011, 07:22 PM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by scirocco View Post
On 4S, I don't think 6 or 6.5" pitch is enough for the 600 Kv motor, and 13" props on 4S are pushing the 770Kv motor overly hard IMO

The 12x6 might work OK with the 770Kv, but you're likely up around 450W - that's as much as I would want to push through a motor that size. 13x6.5 I reckon is too much prop for a motor that size and Kv on 4S.
The Infinite runs pretty cool (~110F motor temp, on the ground) with APC 13 x 6.5 prop on 4s-4000 and gives around 600W of power --> should be plenty for taking off. Also, the plane is not crusing at WOT all the time, should have enough air and time for the motor to cool down.
I tested and it worked.

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Jul 02, 2011, 12:40 AM
Registered User
scirocco's Avatar
Australia, ACT, Kambah
Joined Feb 2001
3,283 Posts
Quote:
Originally Posted by jackerbes View Post
That KDA motor, at 289 grams/10 oz. was just the kind of weight I needed to get a SIG Rascal 40 balanced out right. That was in a clipped nose plane with firewall mount, and the battery in the old fuel tank location.

The SIG classics are wonderful fliers! I don't care what kind of cheap thrills you get out of newer and lighter and faster and whatever, they are a pure joy to fly. Especially if you like to fly with coordinated controls. Sometimes the yank and bank crowd just doesn't get it.

Jack
Yep, around 10 oz in the nose sounds about right - or it is for the taildragger LT-25. Balances with a little 1800 4S about an inch back of the firewall and with 6S 2200 centred about under the leading edge.
scirocco is offline Find More Posts by scirocco
Reply With Quote
Old Jul 02, 2011, 12:55 AM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by scirocco View Post
Yep, around 10 oz in the nose sounds about right - or it is for the taildragger LT-25. Balances with a little 1800 4S about an inch back of the firewall and with 6S 2200 centred about under the leading edge.
If using a 7 oz motor, the 4s-5000 should be able to balance at similar location since it is several oz heavier than the 6s-2200. 4s-5000 also give longer flight time.

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Jul 02, 2011, 06:51 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,222 Posts
I was flying with a 5S 2300 mAh A123 pack, that is equivalent to a 4S LiPO as far as voltages but weighed around 370 grams or so. I was getting 15 minutes or so flights out of that with just general mid throttle cruising around and maybe an occasional loop or roll or something.

But 200 to 215 Watts or so would keep it flying level just cruising around the pattern. That was about 30 Watts per pound on that more than 7 pound plane. That gives you an idea why the SIG are considered to be "slippery" fliers as far as drag.

On final it would just glide and glide.

Jack
jackerbes is offline Find More Posts by jackerbes
Reply With Quote
Old Jul 20, 2011, 03:49 PM
Registered User
United States, WI, Merrill
Joined Jun 2011
1,432 Posts
Hi Guys
I am letting the old kadet conversion slide for a while while I get some needed stick time on a Great Planes EP Super Sportster Rx-R http://www3.towerhobbies.com/cgi-bin...&I=LXAVPG&P=ML and a Kadet Seniorita that is using the motor I had intended for my old Kadet Mark II. I need some practice before I try the Seawind electric 39" seaplane that was to be my first new plane since my 15-20 year hiatus from RC. It didn't want to move very well on attempted grass takeoffs and I was a bit nervous about trimming out a new plane over water.

Thanks for the help. It helped me get to a nice setup for the big Seniorita, and it is just what the doctor ordered for my not so nimble stick fingers.

John

PS hope to get back to the old Sig Kadet sometime so I can fly on the snow and ice out my back door for 6-8 months of the year hear in central/north Wisconsin
jgestner is offline Find More Posts by jgestner
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log SIG Kadet Mark II-Electric_reconfigure aileron w/flaps rawUAV Glow to Electric Conversions 75 Aug 25, 2014 04:03 PM
Discussion Sig kadet Mark II conversion stoked6.0 Glow to Electric Conversions 8 Mar 28, 2011 10:01 PM
For Sale SIG Kadet Mark II NIB flybaby55 Aircraft - Fuel - Airplanes (FS/W) 4 Apr 25, 2009 07:24 PM
Question Conversion Of Kadet Mark II To Electric? tigerdude426 Glow to Electric Conversions 1 Feb 06, 2007 09:51 PM
Alert NIB SIG Kadet Mark II Kit Gene Chernosky Aircraft - Fuel - Airplanes (FS/W) 0 Feb 21, 2004 09:38 AM