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Electric Conversion

Old 09-20-2009, 12:57 AM
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sweetrex
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Default Electric Conversion

I'm in the process of converting a Richmodels Lancair Legacy. The plane was designed for a .46 size motor but I think I'm going to put a .60 size equivalent like a Power 60 b/c of the weight. The power 46 specs just don't look like it's gonna cut it. I was wondering if anyone had a battery recommendation for me. I think the plane's gonna weigh in at about 8 lbs. I have a 4 cell 3200mah battery but I'm not sure that it's gonna do the job. I just don't know. Anybody have any ideas?
Old 09-20-2009, 12:48 PM
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DaveFlynn
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Default RE: Electric Conversion

I'm running a KMS 4130 Kv=380 comparable to the power 60 with a 9S1P 2100mAh and a 13x6 glow prop. It seems to perform as well as the .46 glow powered birds, but not even close to what a .60 would do. You could get another 4S 3200 to series with the one you have. I'm partial the the Castle HV-45 for an ESC, but in this case the HV-30 would be OK as it tops out at 16 amps (550 watts) in level flight and 25 (900 watts) on the ground.
Old 09-20-2009, 05:03 PM
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sweetrex
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Default RE: Electric Conversion

Thanks Dave, That's the motor I was considering. I think I'll just get another battery and series them. I don't want monster power, I'm looking for scale flight charactaristics although the Legacy seems to hold it's own in the real world. Is an HV ESC necessary? I've got a 70 amp Waypoint sitting around. I'm partial to CC ESC's as well but I'm not partial to the price tag. Especially right now. If you suggested it two or three years ago I would've jumped all over it.
Old 09-20-2009, 05:40 PM
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Default RE: Electric Conversion

The Kv is too low to run less than 6S and get any real power out of a 12 to 14 inch prop, too many amps and not enough watts.
Old 09-21-2009, 01:57 AM
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sweetrex
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Default RE: Electric Conversion

So then the 4s batts in series isn't going to work? I'm confused b/c in your first reply you suggested that.
Old 09-21-2009, 11:06 AM
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DaveFlynn
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Default RE: Electric Conversion

Yes, 8S on a 12,13 or 14 inch prop will work well. Test with a watt meter and tachometer to be sure.
Old 09-21-2009, 11:17 AM
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cyclejockey
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Default RE: Electric Conversion

I thought "series" meant that you were just increasing the mah, not multiplying the # of cells?
Old 09-21-2009, 11:20 AM
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Default RE: Electric Conversion

ok, I get it. Thanks Dave. I was misinformed at the hobby store yesterday. Series is multiplying the # of cells.
Old 09-21-2009, 11:31 AM
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cyclejockey
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Default RE: Electric Conversion

Next question then, Dave...
BTW, this is Sweetrex. I have two accounts.

The KMS motor I have is the 4120-06 the specifications recommend 3-5 cell batteries. Am I going to burn it up if I use an 8s battery? I know you said yours is set up with a 9s battery. Did I read that correctly?
Old 09-21-2009, 11:39 AM
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DaveFlynn
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Default RE: Electric Conversion

8S or 9S is good on the KMS 4120-06 Kv=610. Prop to stay below 30 amps. I fly my Twin-Star with counter rotating APS 9x6 props on a 9S1P 3200mA, it's wicked fast.
Old 09-21-2009, 11:53 AM
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cyclejockey
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Default RE: Electric Conversion

Cool, thanks for the advice. I can't wait to get this puppy in the air. I have a mount for my GoPro camera in the cockpit. the camera turns toward the direction of the turn like the pilots looking to his left and right. Should be interesting.

Two more things...

I want the camera to rotate slower. Right now, the servo horn I'm using is an arm. Can I slow the motion down if I use a wheel type or a longer arm? The servo that drives the camera mount is connected with a y-harness from the left aileron servo. So, when the Lt. Aileron goes up, the camera rotates to the left and of course centers and looks Rt. when the servo is moved in the opposite direction.

Next... I want to run a receiver battery in addition to the lipo's. My thinking is that I can dedicate all of the battery pack power to the motor and drive the servos with a smaller receiver pack. Is it just as simple as plugging the receiver pack into the receiver and the speed controller knows what to do? Am I going to gain a noticeable difference?

Thanks in advance for your help.
Old 09-22-2009, 07:54 PM
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sweetrex
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Default RE: Electric Conversion

Bump

Anybody can answer my question...If you have an intelligent answer.

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