HobbyKing.com New Products Flash Sale
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Old Nov 01, 2011, 07:06 PM
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Jonathan,

Maybe they're not currently available because of the agreement back in 2009 between Kokam and Dow that designated the USA to Dow as manufacturer and supplier of Kokam's batteries. From the D-K website, it looks like they are going after the big commercial accounts like automakers, buses and trucks, etc. I though maybe ebay might have some suppliers but a quick peek there didn't look good. If you contacted Kokam I'm not surprised you didn't get a response, but D-K may be no better as they don't seem to be looking to retailing batteries at this time.

Chappy
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Old Nov 02, 2011, 12:02 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
Joined Feb 2001
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An outsider about the inside of the Joby company
http://endless-sphere.com/forums/vie...art=30#p408902

Prettig weekend Ron
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Old Nov 02, 2011, 12:11 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
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All ESC manufacturers say the same, too long battery wires will kill controller, see:
http://www.rcgroups.com/forums/showthread.php?t=952523
Contents
  • Problem
  • Solution
  • Rule of thumb
  • Capacitor type
  • Capacitor polarity!
  • How to add extra capacitors
  • Expert/manufacturer opinions, rules of thumb, installation
  • Explanation/theory
  • Measurements
  • DIY pictures

More explanation, considerations, capacitor choice, albeit with a slight e-blke slant
http://endless-sphere.com/forums/vie...p?f=30&t=22194

Castle Creations and MGM Compro capacitor banks:
http://www.rcgroups.com/forums/showt...0#post19610747

Castle Creations rule of thumb versus Ludwich Retzbach's rule of thumb:
http://www.rcgroups.com/forums/showt...0#post19653752


Prettig weekend Ron
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Old Nov 02, 2011, 03:29 PM
davincicode
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misc stuff

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Old Nov 02, 2011, 08:13 PM
too old to 3d
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United States, GA, Peachtree City
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Congratulations on such a project. I am still in awe from this Lazair from the movie “The Gods Must Be Crazy II."
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Old Nov 02, 2011, 11:28 PM
Fly it like you stole it..
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Florence, Al
Joined Oct 2000
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Man, I wish I could find a Lazair for sale around here..
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Old Nov 02, 2011, 11:43 PM
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Gary, IN, USA
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I have become aware of a problem with some "big" brushless motors used in RC airplanes and noticed that yours may be approaching that time for an inspection. The motor your plane uses is a 1st cousin to ones used in larger RC airplanes. Let me also say that the problem in RC flying appears to me to be the combination of too small of bearings in the bigger motors + precession forces from outrunner type and larger props. The bearings are failing in 50 to 100 hours flying time. When it begins it progesses rapidly and is easy to know by the buzz that is heard when turning and the feel of the loose prop shaft.
Many of the RC motors can be used with the prop attached to either end of the motor. There is an easy fix for the type with the prop adapter that screws to the rotating part of the motor; the back end of the motor shaft is exposed and offers the alternate prop mounting with a collet prop adapter. Add another bearing and support onto the exposed shaft. This gives the motor 3 bearings.
A 3 bearing motor runs much, much better that the stock motor with 2 bearings.
I use the A123 batteries because they are the safest under any condition. I believe that they have been subjected to charge/discharge conditions that are too brutal for standard lipos and have recorded 1,000 cycles with only a 10% loss in capacity.
By sheer luck I came across this discussion thread and couldn't quit until I read it entirely! Well Done!
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Old Nov 03, 2011, 10:11 AM
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Hey Dale,

(BTW, thanks Chappy for your reply) If you're still out there, would you be interested in selling battery units. My search for large format li-poly cells has come up empty. A123 cells are good, but expensive and difficult to make large packs out of. I'm forced to the conclusion that the only way forward for the "little guy" like me is to combine RC li-po's to get the voltage/Ah I need. You've come up with a novel approach, and I have no desire to re-invent the wheel. So that's why I'm asking if you'd be interested in selling battery units, or at least the PCB and charging method.

Thanks,
Jonathan
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Old Nov 03, 2011, 06:35 PM
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Some years ago I did research into comparing gyroscopic reaction/precession of electric airplanes vs internal combustion airplanes. Bottom line was that similar power size was grossly different because of the large rotating mass of the electric motor compared to the smaller rotating mass of the crankshaft of the IC engine; The gyroscopic precession of the electric motor is about 123 times greater!
This morning I awoke with one of those bursts of revelation......if the twin motors are made to counter-rotate with the tops of the props rotating towards the fuselage, the GP forces when you apply rudder yaw will be up on one wing and down on the other wing just like applying aileron control to bank into a turn. The pitch control with the stick causes GP forces inline but opposite with each other and cancel out.
So, by simply switching a pair of wires feeding each motor to get the correct motor rotation, you get a power roll assist.
Another thought; I'm sure someone can create a simple program that compares the known watt-hours in the battery with the watt-hour useage and display it on a digital readout just like a fuel guage to show what's left in the "tank".
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Old Nov 04, 2011, 12:28 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
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Jim, Joby motors are not a RC spin off,and itīs an inrunner, not an outrunner, see the links, drawings, pictures and videos in this thread
http://www.rcgroups.com/forums/showt...highlight=joby

Prettig weekend Ron
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Old Nov 04, 2011, 04:55 PM
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Quote:
Originally Posted by Jim Petro View Post
Some years ago I did research into comparing gyroscopic reaction/precession of electric airplanes vs internal combustion airplanes. Bottom line was that similar power size was grossly different because of the large rotating mass of the electric motor compared to the smaller rotating mass of the crankshaft of the IC engine; The gyroscopic precession of the electric motor is about 123 times greater!
This morning I awoke with one of those bursts of revelation......if the twin motors are made to counter-rotate with the tops of the props rotating towards the fuselage, the GP forces when you apply rudder yaw will be up on one wing and down on the other wing just like applying aileron control to bank into a turn. The pitch control with the stick causes GP forces inline but opposite with each other and cancel out.
So, by simply switching a pair of wires feeding each motor to get the correct motor rotation, you get a power roll assist.
Another thought; I'm sure someone can create a simple program that compares the known watt-hours in the battery with the watt-hour useage and display it on a digital readout just like a fuel guage to show what's left in the "tank".
The joby motors have very little mass, I doubt the gyroscopic effects are pronounced enough to be noticeable in this application.

There are tons of very cheap FPV OSD instruments with capabilities far exceeding standard GA VFR instrumentation.
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Old Nov 05, 2011, 05:08 PM
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Ron, thanks for the links to the Joby motor. It is unique and one of the most effective designs applicable to airplane power that I've seen. Yes, it has less motor mass gyroscopic precession, but there is more from the larger prop. Total should be less than the generic designs I calculated from, but still (now this is a wild-ass-quesstimate) perhaps 50 times more than a comparable internal combustion power. Therefore, a twin e-motored plane with the counter-rotating props turning inwards at the top will still give noticable roll assist force.
Structurally, I am still concerned about the bearing loads from the GP forces; Not sure which would be cheaper, 2 larger diameter bearings or a longer shaft with a 3rd bearing. In any case, I don't see a catastrophic motor failure mode with the existing motor design. The sound of bad bearings will catch your attention soon enough.
Has the cause of the period of rough startup been determined? It appears that the phasing is too fast for the initial inertia. All the links to the 'experts' of ESCs are expert with RC size and style in-runner and out-runner motors. The Joby looks like it would be significantly electrically different.
I look forward to your posts during the winter as you enjoy flying the Lazair.
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Old Nov 06, 2011, 10:12 AM
homo ludens modellisticus
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The Netherlands, GE, Nijmegen
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Of course it's an excellent design Jim, the head of development is Dutch (not me though )

Controllers don't know whether a motor is an in- or an outrunner, nor do they know the number of magnet- and statorpoles, it's all the same to them, the motor is a black box. I once read here on RCG that about 90% of the software code in RC sensorless controllers is dedicated to motor startup. At startup, the controller does not know rotor position. No BEMF signal from the motor because rotor speed is zero, therefore the motor cannot 'tell' the controller when to do the commutation switching. The controller has to dick around a bit at first, hence the erratic startup. Rotor+prop inertia plays a role here. Sensored controllers don't have that 'problem'.
About the workings of a brushless controller:
http://www.aerodesign.de/peter/2001/...index_eng.html
-> SPEEDY-BL diy brushless controller


Vriendelijke groeten Ron
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Old Nov 06, 2011, 10:50 AM
homo ludens modellisticus
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BIG rc motors, a compilation
http://www.rcgroups.com/forums/showt...0#post18657288

BTW the sensorless brushless German SLS controllers donīt have startup issues, SLS uses a different principle.
Check out the airplane and shovel (traction) videos.


Vriendelijke groeten Ron
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Old Nov 07, 2011, 08:05 AM
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South Africa
Joined Feb 2010
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"BTW the sensorless brushless German SLS controllers donīt have startup issues, SLS uses a different principle."

Wish they could make it mainstream on all controllers, not that i'm too concerned about startups, my heli starts up perfectly, i use very soft start (heli) so i guess that works differently too for it always starts up good, however my turnigy motor with aeronuts platinum esc on my plank "stutters" a bit sometimes on startup, i find it happening more if the battery has run down a bit but not at lvc yet ( 3s battery was at 11.5 volts) Maybe i should just check my timing on that controller again.... if my timing is fine then it could be a slight compatibility issue, however not a major problem for i does not always give me this problem.
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