100% scale, Electric Lazair - Page 9 - RC Groups
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Jun 02, 2011, 08:22 AM
Dale Kramer
KiloOne's Avatar

Rewinding the motors was necessary for me to try to get 10 kw out of them with the voltage and propeller that I was committed to. The stock motor converted to WYE was only 7.5 kw with my prop and voltage.

If you want to convert another aircraft the main concern would be the amount of power required to keep the aircraft flying. Those numbers are not published but can be determined from the best L/D and speed if known.

I did once make a contra-rotating electric motor using brushless cdrom sized motors but I used brushes to feed the one motor its power. It worked great though.

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Jun 03, 2011, 02:11 AM
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Here is another e-flight motor that seems has just become available to the public. Not sure of the price though. Looks to be a bit large for a part 103 ultralight twin-engine design.

Jun 03, 2011, 01:32 PM
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g00bd0g's Avatar
I know it's not as sexy as the brushless options but have you considered using Perm or Agni brushed motors? We use them in our electric motorcycles with great success. The Agni is capable of almost 20 kW peak and about 10 Kw sustained, depending on cooling. The perm a bit less, though it is built like a tank. I know you will probably add 20 lbs or so going this route, but the extra power may be worth it.

Agni is already doing well in the Electric Airplane world, holding the current aircraft speed record.

Some friends of mine recently got a tour at Joby, it sounds like an electric airplane enthusiasts wet-dream, maybe you could get out there and check it out.
Jun 03, 2011, 09:30 PM
Registered User
Wow !
Last edited by Lazair883; Jun 04, 2011 at 12:39 AM.
Jun 03, 2011, 11:45 PM
Registered User
Dale, what controllers are you going to use with the Joby motors?

Have you any experience with controlwing (Spratt) type of ULs. The simplicity of the Spratt 103 interests me as a twin pusher?

Jun 04, 2011, 01:49 AM
Registered User
Hi Dale,

I hope you can share continue your experiences with the Joby's. I'm also quite interested in what you will use for controllers?

I've been slowly putting together a lite trike with an Agni 95, but might change to one of these Joby's if I can source a decent controller for it.

Since the Agni is brushed, I am trying to get by with a rectactor controller. Am using the a123's too, as I was a bit scared of going Lipo.

Good luck with it all. I hope to follow along with your progress & journey.

Jun 04, 2011, 11:49 AM
rebell's Avatar
Dale, I would think that you should use bigger current capacity controllers as well, it should not only be about cost, but safety as well. What will happen if the ESC catches fire in the air? Do you have some sort of safety cut-off from the batteries? Did you make use of additional capacitors between the battery and ESC?
Jun 04, 2011, 12:19 PM
Originally Posted by rebell
Dale, I would think that you should use bigger current capacity controllers as well, it should not only be about cost, but safety as well. What will happen if the ESC catches fire in the air? Do you have some sort of safety cut-off from the batteries? Did you make use of additional capacitors between the battery and ESC?
It would help if you read the thread before you ask questions that are already detailed within the thread.
Jun 04, 2011, 01:33 PM
rebell's Avatar
If you read the thread you will see that I am following from the beginning, but it is possible I missed something somewhere. If you are talking about bigger ESC, I know what has been said, it is still my opinion, or is it wrong to have an opinion? If you are talking about safety cut-off, I just went through the tread again and donít see anything about it. What post is it? If you are talking about extra capacitors, yes I know Dale said he got bigger ones to put on the ESC, but I don't remember him saying that he actually installed it. What I did see him saying is he installed caps on the PCB, but that is a long distance from the ESC and it should be as close as possible to the ESC or in addition to bigger capacitance on the ESC, which is why I am asking. For safety, check, double check, triple check and check again. Is it against forum rules to double check? May I not be concerned about his safety?
Jun 04, 2011, 09:16 PM
Dale Kramer
KiloOne's Avatar
No problem asking questions anytime.

As far as the controllers go I plan to stick with the Jetispin OPTO 300 controllers until they prove inadequate. They will easily handle 220 amps or in my case about 14 kw continuous or 19 kw peak. There are no components in the controller that would lead to a large sustained fire. I have blown one OPTO 300 already in early tests (almost all the FETs blew) and there was barely a whimper from it. After much debate with myself, I have continued the model airplane tradition of not putting in a mechanical quick disconnect. Basically, I figure if something shorts it will soon go open or the batteries will run down. I have already discussed battery fire possibilities and I am happy with that level of safety.

My longest battery leads are about 36 inches and here is a thread I started about my capacitor location selection: https://www.rcgroups.com/forums/show...ending+battery

I did not end up replacing the 63v caps used on the Jetispin OPTO 300 as I found that there is an internal 63v cap that is almost impossible to replace anyway. I have been monitoring the OPTO 300 smoothing cap temps and have not noticed any rise above ambient so I am still happy with my choice in pushing them a little on voltage.

Thanks for the other motor choices but I am still sold on the Jobys.

I would love to tour Joby but a side trip out there would be difficult right now. I have changed my order to JM1 82kv motors. They are going to be about 3 week delivery. My dealings with Joby so far have been first class!

Last edited by KiloOne; Jun 05, 2011 at 06:45 AM.
Jun 05, 2011, 02:40 AM
rebell's Avatar
Thanks for the answer Dale. That link does not take us to the correct thread. I must go now, so will search later.
Jun 05, 2011, 06:47 AM
Dale Kramer
KiloOne's Avatar
Sorry, link fixed.
Jun 07, 2011, 01:56 AM
Registered User


flying a lazair without earplugs must be something else. i was very excited to read about your test flight. i hope to see you in oshkosh.
Jun 09, 2011, 10:26 AM
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Please email me, I'm interested in helping. I'm an AP/IA and a cfi, the cri-cri guys are flying their machine and it was in a major mag this month. Brian p wallis at the common email server that begins with hot.
Jun 10, 2011, 09:42 AM
Registered User
I can see the reason to change motors but wanted to make comment about the HK motors. From my experience with large brushless motors, cooling seems to be an issue when pushed to their limit. It seems to me at least, that airflow doesn't go through the motor only around it unless forced to. With my large planes, at the 6000 watt level, the difference between using a duct to force airflow though the motor and not using one can be 50+ degrees. Seems using something like an reverse funnel type device to force air through the stator would help cooling. Just my two cents....
Best of luck to you with this project.
Last edited by yellowbird2800; Jun 10, 2011 at 09:48 AM.

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