Electrajet EDF conversion

[airmark]

Last week I had the 1st, 2nd and last flight of my Electrajet EDF conversion.

I spent more than 2 months modifying the airframe, and I was more nervous than usual for the maiden flight. I hadn't yet added color & markings, and only have 1 pic of it.

The maiden flight went well, thanks for advice from Bob Andris and a perfect hand lauch by Ron Fikes.
I wanted to share this setup-- it's a good one for a faster-than-your-typical-parkflyer plane:

* minifan 480
* Mega 16/15/4 (fan, motor & leads= 5.5oz)
* TMM ComPro 18e ESC,
* Thunder Power 4s 1950 Lipo pack. (5.4oz)
(yes 14.8V. Fully charged 16.8V, which is max the ESC can handle w/ bec)

This combo gave 17.8oz static thrust at 13.4 Amps on the bench and flew this 23oz plane on 1/3 throttle. Motocalc predictions at static were pretty close, so I'm confident I could fly it for over 35 mins at half throttle or about 12-15 mins at high throttle.

Unfortunately, after the first flight I modified the ailerons mounting by packing tape only. On the second flight, the ailerons pulled away (100% slop) and it had a life-ending meeting with the dirt. Oh well, I still have my pride!

I also was told I should balance the fan rotor. At a couple throttle levels, there was a screetching sort of vibration sound.

For anyone else thinking of converting the Electrajet to EDF, I recommend to mount the fan forward of the fins, as low as possible and in a simple manner to reduce resonation/vibration.

I could post the pic here, as soon as I figure out how to do that

Cheers! Mark

[genovia]

Cool,

Thanks for sharing

Post pic. hurry

--genovia

[nick]

airmark,

Sorry to hear about your crash . AFAIK, WeMoTec fans rarely come off the line balanced. I spent a couple of hours balancing the twin micro fans in my A10. I found that static balancing isn’t enough and you have to do some dynamic testing before you are done. I’m in the middle of doing the same with my mini-480 and it’s non-trivial but definitely required. I think that is part of the challenge of EDF. I’m waiting to be convinced that it is actually possible to balance a rotor across the entire RPM range for a given motor/rotor combination. In the case of my A10 I still get sympathetic vibration around 10 and 20K RPM. The good news is that the fans are typically spinning in the 30K range (which is really where you want to be irrespective of the fan size).

Cheers,
nick

[RedFive]

Hello everyone,


Airmark...sad to hear about the electrajet. I like the 4s setup. I'm working on a similar project. I currently fly my Wattage Saber and Mig with Etec 1200s in a 3s2p configuration. Duration is stellar....but they just don't have the punch like my old Kan 1050s . The Thunders look promising. If you think they can pull 14-15 amps burst without paralleling, I'll make a call to Mr. Wang.

Nick...couldn't think of a better moderator. Even Geno is here. Feels like the ezone already.

Best Regards,
Randy

[genovia]

Nick...couldn't think of a better moderator. Even Geno is here. Feels like the ezone already

Redfive,

Welcome you guys are already rock'n this place. I see Nick is the mod. Hi Nick

It brings tears in my eyes, when we have to say good by to Ezone and make Bay Area R/C our new Haven. Don and Paul are working overtime to create this place and have it running smoothly.....

"Others will come" - movie, Field of dreams.


Regards,
Antonio

[airmark]

Nick, thanks for the info on balancing.

Randy, I recommend call Mr. Wang. The cool thing is they'll make custom config packs for ya. I also have some of the new Kokam 1500s on the way, which FMA rates as 12A continuous - 15A burst.

I just figured out how to post a pic here, and subscribe to a thread to get notice of postings.

Best regards,
Mark

[airmark]

An added note of caution to anyone using a similiar higher V Lipo flight pack and BEC.. I put this power combo into another plane, and learned I am over-taxing my ESC.

The 4s Lipo flight pack is not the problem, nor is motor amps--it's the total watts that the BEC can handle=== and at the higher V, 3 servos is overloading my TMM Com Pro 18A ESC. 2 in-flight power cut-outs, and was lucky to have an undamaging fall to earth.

I talked to the guys at Castle Creations about their ESCs (I have a Phoenix 10) and they told me its BEC is more stout than most; (properly cooled) can handle a 3s Lipo flight pack and 3 micro servos. Their Phoenix 35 has the beefiest BEC, so I could use that with my mf480/Mega/4S Lipo setup; or disable the BEC and add a rx pack.

They recommend Hitec HS-55 servos which they say consume around 30% less power than the GWS equiv.

Mark

[nick]

...
I talked to the guys at Castle Creations about their ESCs (I have a Phoenix 10) and they told me its BEC is more stout than most; (properly cooled) can handle a 3s Lipo flight pack and 3 micro servos. Their Phoenix 35 has the beefiest BEC, so I could use that with my mf480/Mega/4S Lipo setup; or disable the BEC and add a rx pack.
...

Mark,

Are you thinking of a 2 or 3 turn Mega ?
I am considering going with a 2s1p+voltage regulator for my rx pack purely for safety reasons. If my 4s1p pack fails I may be able to at least deadstick the plane in. The CC25 ESC can handle up to 16 cells if the BEC is disabled - but as you point out power is key - I would not use a CC25 with BEC in an application with input power requirements in excess of 300 watts. I would not even think of using a CC25 with BEC disabled in an application requiring input power over 480 watts. The CC35 can get you into the 670 watt range As an aside, I'm still not sold on using Lipolies in high amp applications. My tests show significant temperature rises post landing - which means ventialtion is key both during *and* after the flight. My guess is that one could easily damage a poorly ventilated pack even after landing. Are you seeing this too ?

Nick