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Old May 25, 2012, 09:51 AM
VOLTS > AMPS
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An iffy thing with these motors is that they don't have there collar on the back. Cabledawg has 100 5s 13x6.5 flights on his though.
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Old May 25, 2012, 10:17 AM
Not as Good as The Kid
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South Pasadena, FL
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Originally Posted by stgdz View Post
An iffy thing with these motors is that they don't have there collar on the back. Cabledawg has 100 5s 13x6.5 flights on his though.
The very first conversion I did was an 8S on a Frenzy that originally had a Saito 1.25 turning a 16x6 inch Evolution prop to about 9400 RPMs. Since it was my first go with electric, I didn't want to invest in the e-flite 110 so I bought the ExceedRC 110 equivalent for about $45. It turned an 18x8 to 7500 RPMs and 1450 Watts-out, which was a lot of fun. I liked the motor, even though it was a bit heavy, and so I bought the .46 equivalent and used that to swing a 14x7e APC to about 8500 RPMs on a 4S in another coversion from an OS 55.

I also bought the 160 since it was only $50 but never used it, so a flying buddy put it on his plane and magnets starting coming loose from the first flight. He kept gluing them back with black locktite and finally fried the motor and the ESC.

The same kind of hit-or-miss is what most of my friends experience with HK motors. Tom and I could not keep one in the PA 260 for more than a few flights, and when we went to Motrolfly, every motor we bought is still in an airplane with zero failures or issues.

The Frenzy is in the garage with the other retirees, but I'll bet the motor will pull that plane around for quite some time considering that it lasted for about 100 flights, give or take a few. With the new battery technology and weight difference, I'll bet I can shave a few ounces off the plane and improve the performance, but it will never fly like an EXP, so it will sit there on the rack for a long time, I'm afraid.
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Old May 25, 2012, 11:24 AM
Grumpy old git.. Who me?
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Originally Posted by stgdz View Post
An iffy thing with these motors is that they don't have there collar on the back. Cabledawg has 100 5s 13x6.5 flights on his though.
An easy to fix though... Just reverse the shaft. The other end of the shaft has a flat machined in which I assume is for collar retaining screw to sit against. The rotor has drilling for a bolt on prop adapter, a Hacker one would fit perfectly.
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Last edited by JetPlaneFlyer; May 25, 2012 at 11:46 AM.
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Old May 25, 2012, 11:44 AM
Not as Good as The Kid
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Have any of you come up with a decent HK motor for 8S that can do 2600 to 2800 Watts-in? I'm thinking about an 11 pound plane (5Kg) conversion and would like a 300Kv that can swing at least a 20 inch prop. 22 would be better, of course, but I don't see that happening with a 500 gram motor which will keep the weight about the same as the gas setup. This would be about the same output as a 33 to 35cc gas engine and the new GT33 power is what I'm trying to replicate... about 2400W and 3.2 HP.
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Old May 25, 2012, 11:57 AM
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A couple of possibilities:
http://www.hobbyking.com/hobbyking/s...0KV_2400W.html
http://www.hobbyking.com/hobbyking/s...arehouse_.html
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Old May 25, 2012, 12:21 PM
Not as Good as The Kid
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Originally Posted by JetPlaneFlyer View Post
Here is what I see, so please tell me what I'm missing. They say this is a 6 to 8S motor and their test is with 6S using a 17x8 prop to 1312W at 22.2v and 60A.

A 270Kv motor on even 23.2v will swing a 17x6 prop to only 5950 RPMs on 6S and that is only if the motor is operating at a 95% Kv efficiency:

23.2v * 270Kv * 0.95 = 5950 RPMs

A motor only needs 350 Watts to spin a 17x6 prop 5950 RPMs. I'll bet the HK motors will never deliver anything near 95% KvE, which means that at 80%, the RPMs will only be 5010 and the Watts-out will be 205.... now that's a joke, right....

Am I missing something?
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Old May 25, 2012, 12:37 PM
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Originally Posted by Aeroplayin View Post
Am I missing something?
Yep.. the HK 'test' data often needs to be taken with a large pinch of salt
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Old May 25, 2012, 12:41 PM
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The other motor is showing the same discrepancy in power....

290Kv on 23.2v (6S) with an 80% KvE with a 19x12 prop will spin 5280 RPM which requires 1000 Watts-out. They are talking about 6Kg of thrust. Sorry, but no freakin' way.... Oh, and I just saw that they are calling this a 9-10S motor, so why did they show test data on 6S? This is either crazy, or they think we're just stupid.

Now if I change the volts to 38.67 (3.87v per cell), the 290Kv at 80% Kv efficiency will turn 8970 RPMs. That's 4630 Watts required to do that with a 19x12 (their test prop) at 80%, and 120A.

They state that this is a 78A max motor. Someone must have been using a calculator from Alibaba to figure this out.
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Old May 25, 2012, 01:01 PM
Don't worry be happy :)
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Originally Posted by JetPlaneFlyer View Post
...struggling to cope with the 14" APC then possibly my similar kv hand wound Scorpion might also be feeling the strain...
Hello!

What is the KV on your hand wound Scorpion? I have the Scorpion SII 3020 890kv.
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Old May 25, 2012, 01:05 PM
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Originally Posted by Stark View Post
Hello!

What is the KV on your hand wound Scorpion? I have the Scorpion SII 3020 890kv.
750kv.. I wanted to be able to spin a 14" prop on 4s and it does that really well with fantastic power, but unfortunately it seems that the structure of the motor is not quite strong enough.
It started life as SII 3020 1110kv
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Old May 25, 2012, 01:13 PM
Don't worry be happy :)
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Thanks!

I'm using my Scorpion in a Sebart Katana S 30 E with 3 cells and a Xoar 13x7. It gives enough power to pull straight out of hover so I'm happy for now.
I've tried the APC 14x7 but I feel that it gives me slower reaction compared to the smaller Xoar for about the same vertical performance.
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Old May 26, 2012, 08:18 PM
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Sorry for the late reply
We have been doing this modification to all motors in the 28xx size factory built or not.
I would say the 750Kv is still a bit much with the 14x7 for hard 3D flight, precision flying would be fine.
There will be 950, 750, and 680Kv, in the 2820 serries, the 680Kv will be the 4s 14x7 set up, watts about 700.
Should have the 680 in about a month.

Ken
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Old May 26, 2012, 08:34 PM
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Originally Posted by Subsonic Ken View Post
Sorry for the late reply
We have been doing this modification to all motors in the 28xx size factory built or not.
I would say the 750Kv is still a bit much with the 14x7 for hard 3D flight, precision flying would be fine.
There will be 950, 750, and 680Kv, in the 2820 serries, the 680Kv will be the 4s 14x7 set up, watts about 700.
Should have the 680 in about a month.

Ken
Thanks to your fast turnaround, I should have my 680kv back in a few days!
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Old May 26, 2012, 10:33 PM
Just flitting about!!
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All this talk about the hot 2820-750 spinning too fast to run the 14x7 prop, why not just trim down your throttle end points?

Tom does it apparently on the 60" with the 4315-480 motor so why not on this 2820-750 motor and trim it down to say 8000 or 8200 rpm at wot?

You can always use a lighter prop than the apc as well, Xoar or Vox are almost half the total weight of the APC and kinda effects the outcome of your angular momentum calcs significantly I think?

Who really needs 1000W on a 48" plane anyway?
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Old May 26, 2012, 10:41 PM
Just flitting about!!
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Joined Aug 2011
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Quote:
Originally Posted by Subsonic Ken View Post
Sorry for the late reply
We have been doing this modification to all motors in the 28xx size factory built or not.
I would say the 750Kv is still a bit much with the 14x7 for hard 3D flight, precision flying would be fine.
There will be 950, 750, and 680Kv, in the 2820 serries, the 680Kv will be the 4s 14x7 set up, watts about 700.
Should have the 680 in about a month.

Ken
Ken,
is this modification to the 28xx range going to be ex factory or SubsonicRC only? ( I am referring to the set screw in the bearing hub being drilled further into the bearing tube)
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