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Old Mar 05, 2009, 09:23 PM
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TEBerg's Avatar
Clovis, California
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Kadet Mk II Conversion

The airplane wing is actually from the "original" Sig Kadet which was built in 1982. After much learning and horsing around, I replaced the fuselage (dad wrecked it) in 1997 with a Kadet MKII fuselage. During that re-build I installed a K&B 40 on the plane.

The K&B is a bushing motor swinging a 10X6 prop. Never really had very good power and over-heating is a problem. So, I’m interested in converting her to electric.

I have parts and pieces from my failed EDF attempt. They include a 45 amp ESC, UBEC, and two 4S LiPo batteries from Exceed RC (NitroPlanes).

I’ve been reading posts, learning about out runner size and Kv ratings, running motor calc on a whole bunch of different combinations… With doing that, using an AXI 4120/14 would probably be perfect on this plane with a 650Kv rating and good performance.

However, you have all heard this before and I apologize – I want to go with the cheapest setup to get the plane in the air (after all, it is going along with NitroPlanes stuff)… Therefore, I'm planning on using the Turnigy TR 42-50A 700kv Brushless Outrunner

So, I’m currently planning the following:

Motor: Turnigy TR 42-50A 700kv Brushless Outrunner / 720W
Prop: MA 11X8 3-blade, for ground clearance and some extra pull.
Battery: Exceed 4S (14.8V) 15C, 2200mAh LiPo
ESC: Exceed 45 Amp, separate UBEC
Plane: 53in wing 5-6 lbs

I think 2 batteries in parallel would be a great option for flight time. But, I will have to base that decision on weight and balance of the Kadet with the pack(s) mounted where the fuel tank is located.

This all should give me about 3-4 minutes of flight time at full-throttle with about 80 ounces (5 lbs) of thrust at 35-40 amps...

Now I have gone through pages of different motor configurations on electrifly and also looked up Kadet and other 40-size conversions… It looks like a motor in the 600-800 kv range will work best with the 800 providing over 6 pounds of thrust with only 2 minutes of flight time. A 500 kv motor will give me 5 minutes of flight time, but only 4 pounds of thrust. Props can provide a lot of the same differences...

So at this time it looks like the Turnigy 700 kv motor will fit right in the middle with the 11X8 3-blade prop. I have read several reviews that said the 700 will work well with the 4S battery. I also read that the Turnigy motor will probably NOT give me 700 kv on the actual plane, more like 650, which is what I think will be best (like the AXI 4120/14). A 12X8 Electric 2-blade prop would probably give me the best performance, but I don’t have the clearance for that…

So, if you have any feedback on how this motor runs or “doesn’t” run, please let me know. I'm looking to fly her as a trainer with power, not an aerobatic plane that can hover.

As I get things ordered and they arrive, I'll post here as a build thread and provide my results.
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Old Mar 06, 2009, 07:29 AM
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Long Valley, NJ, USA
Joined Dec 2001
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TEBerg,

Nice Kadet, and good luck with her. I like planes that are reborn with parts from other famous planes.

I cannot see anything wrong with your proposed power system - especially if you already have most of the components. I would search the sale forums for a used AXI though.

I think 4s and brushless outrunner with 650 watts in will be tons of power for this bird; you'll be able to throttle back most of the time for longer runtime.

I would recommend a regular (two-blade) 11x7 instead of the three-blade prop, as you will likely have enough power without it, and two-bladers are easier and less expensive to replace.

Paul
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Old Mar 06, 2009, 08:02 PM
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Clovis, California
Joined Dec 2008
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Thanks for the comments and I'll give myself the option of trying different props.

I found out "what type" my ESC is and have a couple extra questions:

I'm pretty sure my ESC is a Suppo Model 50A ESC... At least all the programmed parameters match...

1) battery - Easy, set for 4S
2) Throttle - Auto AND Hard ACC are shown as default
(How do you Set BOTH as default??) or, do I want Auto or Hard?
3) Brake - Soft (best for trainer?)
4) Direction and Cutoff - Direction is easy, but again, how do you set rotation and then cutoff with a different option?

AND THE BIG 2

5) Timing - 15 degrees is suggested for outrunner
6) Pulse Width - 16 KHz for most outrunners...

Any thoughts on these settings???

Thanks Again...
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Old Mar 13, 2009, 01:06 PM
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Clovis, California
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I may just be talking to myself here - but it would not be the first time...

After the comment above I looked at my setup again – In particular the power and propeller. I think I’m going the correct direction. Well, almost – I think that an AXI motor would probably be a great choice. However, I could not find any on-sale or auction that would compare to the Turnigy value.

I’m going to stay away from the 3-blade, because in spite of the “cool look” it draws a huge amount of power for relatively little gain. So I’ll use a 2-blade APC 11X8.5 E propeller.

This has the advantage of not overloading my battery… I had forgot to check that if I only run with one 4S 2200 15C LiPo, I could only deliver approximately 33 Amps without damaging the pack… My original setup with a 3-blade prop would pull about 40 amps. That would have toasted a pack if I tried to run with only 1 pack!!!

Therefore, I’m looking at the following:

Motor: Turnigy 42-50A, 700kv motor
Propeller: APC 11X8.5 2-blade Electric.

This will give me (based on the NeuEnergy calculator: Motor Calculator ) approximately:

Motor Amps = 30
Watts Out = 350
Static Thrust = 80 oz
Full-Throttle Duration = 4 minutes.

This delivers 5 pounds of static thrust and 60 to 70 watts for a 5-6 pound trainer. Now, this is Watts OUT and has been reduced from the calculated Watts IN by the efficiency (inefficiency) of the motor. The Watts IN is about 80 Watts per pound.

I have heard that the Turnigy 700 kv motor will not actually deliver 700 kv. More like 650kv since it is not as efficient as something like the AXI motors. I think that is OK, because the 650 gives me a little longer run time.

I will leave the decision on using 1 or 2 battery packs to the weight and balance of the airplane. Only 4 minutes is a little short on the run time. But with 5 pounds of thrust on a 6 pound trainer, I think I’ll be able to reduce the throttle and fly for a lot longer. If I need two battery packs to balance, I’ll get a lot better run times, but have to “double” charge between flights…
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Old Mar 13, 2009, 02:41 PM
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Sheboygan Falls, WI
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You are going to have really short run times bro. I will post som pics of mine after this post. I have mine running with a turnigy 3548, jeti 77 (overkill but i had it on hand)
and 2 2s 4000mah run in parralel. I madiened it this last weekend and it flew fantastic with this setup. This being said I have both batterys butted up against the front firewall and needed to add wieght to the nose still to balance it right. Basically I have both the cells wrapped in epp and then shove them in there.
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Old Mar 13, 2009, 02:43 PM
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Also running an 11x7 prop but going with the 11x8.5 this weekend. As for power it has more than enough, with all that I get about 10 to 15 min flight depending on power use.
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Old Mar 13, 2009, 02:45 PM
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Her are a couple of pics, the mount is a greatplanes medium brushless mount. very solid and I think i only paid 13 bucks for it? And no I did not do the packer theme, can we please keep that out of the discussion.
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Old Mar 13, 2009, 04:30 PM
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Clovis, California
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Thanks for the notes and the photos...

If I can get up to 10 minutes of run time with the two batteries, it will be pretty nice.

With you running the 3548 and just 7.4 volts but 8,000 mAh (you noted 2S 4000 in parallel) you are in a whole new area for me.. Are you pushing 45+ amps through the 4-turn motor to get the power you need??

I've been pulling my hair out over the question of "How Many KV" for the setup?? The Axi 4120/14 is a 650 kv, I'm looking at 700 and you are running a 900kv.

How are the temperatures on your motor, esc and batts after the flight??

Quote:
Originally Posted by interplanet
Also running an 11x7 prop but going with the 11x8.5 this weekend. As for power it has more than enough, with all that I get about 10 to 15 min flight depending on power use.
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Old Mar 13, 2009, 04:34 PM
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Sorry, my bad I am running 2 2s in series for a 4s 4000mah pack. The motor I have mounted is a little smaller than the ones you were thinking of using. The temps are normal after flights but the packs get a little warm.
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Old Mar 13, 2009, 04:55 PM
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That's what I was wondering, but wanted to check..

So, with the smaller motor, you are pulling about 45 amps for 90 oz of thrust (5.6 pounds) The motor calc (using an axi 2820/12, 920kv) says you would have 4:30 at full throttle with the 4,000 packs. You're getting 10 to 15 so throttle management gains you a bunch of time..

How does the power feel?? You said it flew fantastic, nice to hear. Did you spend a lot of time at 1/2 throttle? How was the vertical/size of the loops with 480 watts of power (from motor calc)??

Quote:
Originally Posted by interplanet
Sorry, my bad I am running 2 2s in series for a 4s 4000mah pack. The motor I have mounted is a little smaller than the ones you were thinking of using. The temps are normal after flights but the packs get a little warm.
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Old Mar 13, 2009, 05:20 PM
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flew mostley at half to quarter throttle. My main concern was not have enough throttle but it had more than plenty. I think my buddy has video otherwise I will shoot some tommorrow.
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Old Mar 21, 2009, 10:53 PM
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TEBerg -- Just ran across your post. I have run that same motor (Turnigy 42-50 -- 700) on a Twist 40 with very good results. I used a 4S 4000mah LiPo pack and got an easy 8 minutes of aerobatics (not 3D). Used an APC 12-8 electric prop and a Turnigy 60 ESC. Watt meter ran about 450 - 475 watts and under 35 amps with that set up. My numbers may be a little off, as I haven't run that setup in a while. Went to a larger motor and 5S pack. I think that you will find the 2200's small. I would parallel them. And yes you would have to double up on charging, but you could also charge them as a single 4S pack at the field. I have done this, but then balance them at home later, then bring the charge down to a storage level.

Just my two cents
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Old Mar 22, 2009, 08:19 PM
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Thanks NoMatta.

Good information on the setup..

I have read that the motor may need some lock-tite on the set screws. I assume there may be screws holding the outrunner on the shaft.

Do you happen to notice this or have any suggestions for anything to watch on the motor??
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Old Mar 22, 2009, 08:56 PM
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Portland, Oregon
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Quote:
Originally Posted by TEBerg
Thanks NoMatta.

Good information on the setup..

I have read that the motor may need some lock-tite on the set screws. I assume there may be screws holding the outrunner on the shaft.

Do you happen to notice this or have any suggestions for anything to watch on the motor??

I use the semi premanent lock-tite on all the screws.There's a grub screw that attaches the bell (outrunner) to the shaft. There is also a piece that looks somewhat like a wheel collar. It mounts on the back and extends through the hole in the cross mount bracket. Be sure to install that piece. I also lock-tite the prop mount on the front of the bell and the cross mount on the back. I have not experienced much vibration, but I also like to eliminate suprises.

As far as running the motor, I always start with a watt meter between the battery pack and the ESC before each flying session, and especially if I change props or battery packs. Don't believe the stated wattage. I would not prop for over 500 if you want long life. Also keep peak amps under 35 and 30 would probably be better. Actually I try not to load sport batteries, esc's, or batteries over 80% of their capability. On the 4s4000 setup I ran in the twist, I usually put around 2200 back in. Could get longer flights, but I don't like buying batteries. Check ESC, battery pack, and motor for temperature after each flight. I go for no more than slightly warm.

Running the 12-8 on 4S gave me good performance and flight times without stressing the system. All in all, I have been quite pleased with the motor. In fact, I am about to put it on a Quickee 500 for fun.

With
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Old Apr 03, 2009, 07:01 PM
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Clovis, California
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The Turnigy 4250A-700 is here...

Not bad on the delivery - Ordered, March 18; Shipped, March 23; Arrived, April 2; and I picked it up at the Post Office (Signature is Required) on April 3rd...

Nice size and good looking motor. I had my plug/switch, propellers and parallel adapter arrive a week ago from Graves RC.

Now I just have to get my Skyraider finished and clear some room to convert the Kadet...
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